Publikationen des Fachgebiets Mensch-Computer-Interaktion

Social events such as cocktail parties are valuable opportunities to build and sustain interpersonal relationships. However, meeting new people, the self-mixing of cocktails, and tracking one's beverage consumption can be difficult and intimidating. To support users during social events, we introduce CheersMate, a smart drinking glass that enables the simultaneous use of a private and a public wearable display. The private display provides cocktail mixing guidance to the user and shows personal consumption statistics during conversations, while the public display encourages social interaction by revealing the user's name and current drink. By clinking two CheersMates, the user can transfer additional information from the private to the public display, for example, showing the number of people the user has toasted with and the number of already consumed drinks. A pilot study with eight participants provides first insights on the acceptance of our concept and on the perceived usefulness as a social catalyst.

As Large Language Models (LLMs) revolutionize Conversational User Interfaces (CUIs) in health and wellbeing, these technologies offer unprecedented potential to enhance user wellbeing by improving physical health, psychological resilience, and social connectivity. However, the integration of such advanced AI into everyday CUI health applications brings substantial challenges, including privacy, user agency, and the psychological impacts of AI interactions. This workshop will provide a platform for collaborative dialogue to explore leveraging these advancements to improve health outcomes while addressing the ethical challenges and risks. Through presentations, breakout sessions, and collaborative discussions, participants will delve into themes such as designing multimodal CUI interventions, structuring conversational interventions for privacy and engagement, personalizing user experiences, and developing proactive and context-adaptive CUI strategies. These discussions aim to develop effective, user-centered CUI strategies that ensure the benefits of LLM-driven innovations are realized without compromising user wellbeing.

On the skin, a small distance between two actuators can result in the perception of a single, centralized stimulus rather than two distinct stimuli – this phenomenon is known as the funneling illusion. In this work, we explore the electrotactile funneling illusion on the forearm in a user study with 16 participants. We placed an electrode strip with 9 electrode pairs along their forearm – from wrist to elbow. The calibration of the same perceived intensity of each electrode pair for each participant shows that the calibrated intensities near the wrist are significantly higher compared to the intensities calibrated near the elbow. A linear regression corresponds to this behavior as well as the qualitative feedback of our participants. Based on this, we created an equation that helps to reduce the calibration time considerably. The results of our study show that the funneling illusion can be reliably evoked at distances of up to 7.2cm. Further, we provide detailed information on occurrence frequency and precision and explored whether an approach adapted for electrotactile feedback can create an apparent tactile motion.

Iterative design cycles for tangible user interfaces and wearable devices require efficient prototyping techniques to optimize development and to elevate the overall design efficacy. A key challenge for rapid prototyping techniques such as cardboard prototyping, 3D printing, or laser cutting is the integration of conductive surfaces. Additional wiring, conductive paint, or special materials like conductive filament often lack the necessary high conductivity and sufficient durability for designing on-skin wearables to measure muscle activity or to electrically stimulate the skin and muscles. To solve this problem we propose to combine spraying and electroplating to create surfaces that exhibit high conductivity, are solderable, corrosion-resistant and skin-friendly, and embody both practical functionality and aesthetic value. In this paper, we describe an effective spraying and electroplating process for rapid prototyping and demonstrate its applicability using several examples of tangible user interfaces. Further, we discuss advantages and disadvantages and describe limitations of the approach.

In the field of controlled horticulture, various methods have been studied to facilitate the environmental data retrieval. One of the great findings in this research is the attraction of insect’s behavior towards the LED lighting of various wavelengths. Previous research shows promising results using LED based insect traps for insect population estimation in greenhouses. Therefore, an automated monitoring system is proposed as a standardization tool for environmental data gathering and estimation of pest population in controlled horticulture settings. The proposed automated monitoring system integrates object recognition models (combination of YOLOv3 and SVM) that identify and classify the pest and beneficial population density. The proposed system provides informative output via a mobile application. As a result, the proposed system functions as an integrated IoT management tool that simplifies the information retrieval process.

Conversational user interfaces (CUIs) have become an everyday technology for people the world over, as well as a booming area of research. Advances in voice synthesis and the emergence of chatbots powered by large language models (LLMs), notably ChatGPT, have pushed CUIs to the forefront of human-computer interaction (HCI) research and practice. Now that these technologies enable an elemental level of usability and user experience (UX), we must turn our attention to higher-order human factors: trust and reliance. In this workshop, we aim to bring together a multidisciplinary group of researchers and practitioners invested in the next phase of CUI design. Through keynotes, presentations, and breakout sessions, we will share our knowledge, identify cutting-edge resources, and fortify an international network of CUI scholars. In particular, we will engage with the complexity of trust and reliance as attitudes and behaviours that emerge when people interact with conversational agents.

Operating small touchscreens with the finger occludes a large part of the screen. We propose using the watch case as the input space, without enlarging the smartwatch. Therefore, we created two prototypes, one with a touch surface on the watch case (CASE) and one with touch surfaces on the watch case and the wristband (CASE+BAND). In a comparative study, we analyze their suitability in a 1D list scrolling task and 2D map navigation task. The results show that occlusion is less of a problem for the list scrolling task, as visibility is sufficient. In the map navigation task, participants reached task completion times with CASE+BAND that are comparable to touch input. CASE was significantly slower, but only requires minimal additional hardware. However, the results of a subsequent longitudinal study demonstrates the learnability of CASE, which led to task completion times comparable to touch input, and provides insights in the gradual development of expert performance.

In the domain of health and well-being, proactive voice interventions have demonstrated their efficacy. However, users often encounter privacy concerns and social embarrassment due to the lack of control over these proactive interventions, especially in formal and social settings. This study introduces a novel approach called “dual-mode intervention.” It begins with primary interventions using different modalities (like graphical, tactile, or auditory). If users do not respond to these primary interventions, the system delivers voice interventions after a short interval. We conducted a study employing a within-subjects design, which involved 15 participants. The study compared dual-mode interventions with direct voice interventions in office settings, focusing on addressing health and well-being issues. Our findings indicate that knowledge workers preferred dual-mode interventions over direct voice interventions. Moreover, direct voice interventions received significantly lower ratings compared to dual-mode interventions. Also, we identify user preferences for different dual-intervention modalities. Our findings reveal that the user preferences depend on the type of health intervention. Vibration emerged as the preferred modality, followed by graphical output, auditory icons, and ringing interventions.

Cycling navigation is a complex and stressful task as the cyclist needs to focus simultaneously on the navigation, the road, and other road users. We propose directional electrotactile feedback at the wrist to reduce the auditory and visual load during navigation-aided cycling. We designed a custom electrotactile grid with 9 electrodes that is clipped under a smartwatch. In a preliminary study we identified suitable calibration settings and gained first insights about a suitable electrode layout. In a subsequent laboratory study we showed that a direction can be encoded with a mean error of 19.28° (σ = 42.77°) by combining 2 adjacent electrodes. Additionally, by interpolating with 3 electrodes a direction can be conveyed with a similar mean error of 22.54° (σ = 43.57°). We evaluated our concept of directional electrotactile feedback for cyclists in an outdoor study, in which 98.8% of all junctions were taken correctly by eight study participants. Only one participant deviated substantially from the optimal path, but was successfully navigated back to the original route by our system.

Prior research has designed and evaluated Voice Assistance (VA) for different settings such as the home, school, and public spaces. Office environments have been relatively understudied, leaving a gap in understanding the essential factors for designing a VA specifically for work settings. In this study, we developed the WorkFit VA specific for the office environment, focusing on the health and well-being of knowledge workers. WorkFit was designed to monitor knowledge workers for sedentary behavior, inconsistent hydration, and stress, and to deliver proactive voice interventions followed by a health recommendation to mitigate those issues. We evaluated WorkFit in a field study with 15 knowledge workers for 5 working days. In the study, we determined challenges and opportunities for voice interactions in work settings. We identified contextual factors for identifying inopportune moments for voice interactions in an office setting. We found that 92\% of knowledge workers accepted WorkFit’s hydration interventions while 79\% of them engaged in walking breaks. Moreover, breathing exercises recommended by WorkFit significantly stabilized the heart rate of knowledge workers during stress. Based on our findings, we propose five design recommendations for the development of VA customized to office settings.

In the study of controlling the insect population within the field of agriculture, many simulation models on herbivorous insects have been proposed. These proposed models contains various factors that determine the population development and growth of the herbivorous insects, such as temperature, light intensity and etc. Due to these factors, intensive studies have been carried out to discover the best model that suits the population development for each specific species of herbivorous insect.

The earlobe is a well-known location for wearing jewelry, but might also be promising for electronic output, such as presenting notifications. This work elaborates the pros and cons of different notification channels for the earlobe. Notifications on the earlobe can be private (only noticeable by the wearer) as well as public (noticeable in the immediate vicinity in a given social situation). A user study with 18 participants showed that the reaction times for the private channels (Poke, Vibration, Private Sound, Electrotactile) were on average less than 1 s with an error rate (missed notifications) of less than 1 %. Thermal Warm and Cold took significantly longer and Cold was least reliable (26 % error rate). The participants preferred Electrotactile and Vibration. Among the public channels the recognition time did not differ significantly between Sound (738 ms) and LED (828 ms), but Display took much longer (3175 ms). At 22 % the error rate of Display was highest. The participants generally felt comfortable wearing notification devices on their earlobe. The results show that the earlobe indeed is a suitable location for wearable technology, if properly miniaturized, which is possible for Electrotactile and LED. We present application scenarios and discuss design considerations. A small field study in a fitness center demonstrates the suitability of the earlobe notification concept in a sports context.

Providing rich feedback on small devices, like smartwatches, can be difficult. We propose colorful electrotactile feedback on the back of a smartwatch. Colorful electrotactile feedback provides private notifications, is energy efficient, and can express various sensations in different qualities. In a first study, 13 participants explored 49 different combinations of frequency and pulse width regarding the perceived “colorfulness” of electrotactile feedback. We investigated what sensations can be expressed with electrotactile feedback and which qualities of these sensations are conveyed. To describe the sensations, participants chose the best fitting terms from a list of 21 terms. The three most frequently selected terms were prickling (177), vibrating (163), and irritating (112). The three least frequently selected ones were twitching (31), tickling (29), and itching (28). In a second study with 17 participants we evaluated a reduced set of 9 sensations that we selected and refined based on the results of study 1. We evaluated these sensations regarding recognition rates and achieved recognition rates of up to 84% without prior learning. Furthermore, we investigated the acceptance of colorful electrotactilefeedbackandpresentamethodforaneasierandfaster calibration of electrotactile feedback.

Validation is the methodology at the end of the simulation and modelling cycle that relates the insights gained by computer calculations to the real world scenario, that is subject of study. Validation establishes credibility concerning the simulation results and implications with respect to the real system. Validation is a very important aspect in real world simulation studies, since important financial and security related decisions concerning the planning, design and optimization of the real systems might be relied. In our study, we conducted a survey on research papers in renowned simulation conferences and evaluated whether validation had been used at all, and if yes, which validation methods had been used to which extent. This reveals the relevance and trust of simulation results of the research papers concerning the real world problem addressed in that research. We found that a majority of research papers neglect the application of validation methodology. Obviously, the validity of the results of simulation studies or the impact on practical problems in the real world seems to be questionable in a vast number of cases.

A methodology on how to prepare agents to succeed on a priori unknown logistics problems is presented. The training of the agents is and can only be executed using a small number of test problems that are taken out of a broad class of generalized logistics problems. The developed agents are then evaluated on unknown instances of the problem class. This work has been developed in the context of last year's AbstractSwarm Multi-Agent Logistics Competition. The most successful algorithms are presented, and additionally, all participating algorithms are discussed with respect to the features of the algorithms that contribute to their success. As a result, we conclude that such a broad variety of a priori unknown logistics problems can be solved efficiently if multiple different good working approaches are used, instead of trying to find one optimal algorithm. For the used test problems this method can undercut, trivial as well as non-trivial implementations, for example, algorithms based on machine learning.

This paper reports on the development of a smart speaker for the home setting of ‘emergent’ users – those whose technology experience and resource availability are low. Earlier research has shown that AI (Artificial Intelligence) powered smart speakers struggled in recognising many emergent users requests. On the other hand, smart speakers powered by human responses were more accurate but slower. In this study, we began by determining, given a choice, emergent users prefer a smart speaker enabled by a human response or an AI response, and what are their preference criteria. We found that they were not completely inclined towards either of those choices. Rather they preferred a smart speaker based on three factors: first, the language of the request, second, the length and complexity of the request, and third, the urgency of response. We developed an integrated version of the smart speaker and evaluated it with emergent user families. From our analysis, it was evident that, when combined, AI and human responses complement each other and provide an elaborate and richer response for emergent users.

Urban environments are often characterized by loud and annoying sounds. Noise-cancelling headphones can suppress negative influences and superimpose the acoustic environment with audio-augmented realities (AAR). So far, AAR exhibited limited interactivity, e. g., being influenced by the location of the listener. In this paper we explore the superimposition of synchronized, augmented footstep sounds in urban AAR environments with noise-cancelling headphones. In an online survey, participants rated different soundscapes and sound augmentations. This served as a basis for selecting and designing soundscapes and augmentations for a subsequent in-situ field study in an urban environment with 16 participants. We found that the synchronous footstep feedback of our application EnvironZen contributes to creating a relaxing and immersive soundscape. Furthermore, we found that slightly delaying footstep feedback can be used to slow down walking and that particular footstep sounds can serve as intuitive navigation cues.

The need for online meetings increased drastically during the COVID-19 pandemic. Wearing headphones for this purpose makes it difficult to know when a headphone wearing person is available or in a meeting. In this work, we explore the design possibilities of headphones as wearable public displays to show the current status or additional information of the wearer to people nearby. After two brainstorming sessions and specifying the design considerations, we conducted an online survey with 63 participants to collect opinions of potential users. Besides the preference of the colors red and green as well as using text to indicate availability, we found that only 54 % of our participants would actually wear headphones with public displays attached. The benefit of seeing the current availability status of a headphone-wearing person in an online meeting or phone call scenario were nonetheless mentioned even by participants that would not use such headphones.

Although in many cases contracts can be made or ended digitally, laws require handwritten signatures in certain cases. Forgeries are a major challenge with digital contracts, as their validity is not always immediately apparent without forensic methods. Illiteracy or disabilities may result in a person being unable to write their full name. In this case x-mark signatures are used, which require a witness for validity. In cases of suspected fraud, the relationship of the witnesses must be questioned, which involves a great amount of effort. In this paper we use audio and motion data from a digital pen to identify users via handwritten symbols. We evaluated the performance our approach for 19 symbols in a study with 30 participants. We found that x-marks offer fewer individual features than other symbols like arrows or circles. By training on three samples and averaging three predictions we reach a mean F1-score of F1 = 0.87, using statistical and spectral features fed into SVMs.

A common problem of touch-based smartwatch interaction is the occlusion of the display. Although some models provide solutions like the Apple "digital crown" or the Samsung rotatable bezel, these are limited to only one degree of freedom (DOF). Performing complex tasks like navigating on a map is still problematic as the additional input option helps to zoom, but touching the screen to pan the map is still required. In this work, we propose using a trackball as an additional input device that adds two DOFs to prevent the occlusion of the screen. We created several prototypes to find a suitable placement and evaluated them in a typical map navigation scenario. Our results show that the participants were significantly faster (15.7%) with one of the trackball setups compared to touch input. The results also show that the idle times are significantly higher with touch input than with all trackball prototypes, presumably because users have to reorient themselves after panning with finger occlusion.

Recent research in Human-Computer Interaction for work has shown that conversational agents (CA) are beneficial for supporting focused work and well-being while at work. Knowledge workers struggle in maintaining focus, work schedule, and well-being. Typically, they rely on multiple tools and services for work productivity, scheduling tasks, and reminding breaks. With the goal of tackling these problems, we propose the concept of a ubiquitous work assistant (UWA), which consists of two components: a stationary CA (S-CA) and a wearable CA (W-CA). S-CA is meant to be placed on user’s work desk while W-CA is fixed on the user’s wrist. The UWA interface is distributed between S-CA and W-CA. We initiated our study by conducting semi-structured interviews with knowledge workers (N = 14). We identified their expectations from conversational agents (CAs) that would assist them in their daily work life. From the interview findings, we developed an UWA prototype that could assist users by briefing their daily schedule, monitoring their schedule, and reminding breaks. We conducted a lab study simulating a home-office environment. The findings of the study show that the knowledge workers see potential in the UWA system. Further, we discuss implications of distributed user interface (DUI) for UWA design.

Software systems have become an integral part of our daily lives. However, users tend to forget that they are not only consuming information, but also delivering personal information to service providers. This data collection means that users’ privacy sphere is increasingly at stake. Informing users about what and how data is collected is pivotal for reaching transparency, trustworthiness, and ethics in modern systems. The main purpose of privacy policies is to inform users about what happens to their personal data. But instead they are extensive and purposefully obfuscating. Information about data practices are hidden in long and ambiguous text passages. To mitigate this, in this paper, we present a concept implemented as a web extension to support the end-user in dealing with privacy policies by providing easier access and visual explanations to privacy-related information. We evaluated the usefulness of our tool in a user study with 65 participants. The results show that our approach helps users to find a privacy policy faster and also supports users to better comprehend the relevant information. Our tool is a first step towards facilitating to deal with privacy policies from the end-user perspective. The results of the study and the positive feedback from the participants show a high degree of acceptance and potential for the tool to increase users’ privacy awareness.

Tactile patterns are a means to convey navigation instructions to pedestrians and are especially helpful for people with visual impairments. This article presents a concept to provide precise micro-navigation instructions through a tactile around-the-head display. Our system presents four tactile patterns for fundamental navigation instructions in conjunction with continuous directional guidance. We followed an iterative, user-centric approach to design the patterns for the fundamental navigation instructions, combined them with a continuous directional guidance stimulus, and tested our system with 13 sighted (blindfolded) and 2 blind participants in an obstacle course, including stairs. We optimized the patterns and validated the final prototype with another five blind participants in a follow-up study. The system steered our participants successfully with a 5.7 cm average absolute deviation from the optimal path. Our guidance is only a little less precise than the usual shoulder wobbling during normal walking and an order of magnitude more precise than previous tactile navigation systems. Our system allows various new use cases of micro-navigation for people with visual impairments, e.g., preventing collisions on a sidewalk or as an anti-veering tool. It also has applications in other areas, such as personnel working in low-vision environments (e.g., firefighters).

This work presents a prototype of a decision-support system for Offshore Wind Farm (OWF) construction based on the Timed Petri-Nets (TPN) approach, which aims to help the decision-maker in the industry to optimize the process execution. The objective function evaluates the solutions or alternatives to find the optimums. We also present a decoupled scheduling strategy that is computationally efficient and stable comparing to the Mixed-Integer Linear Programming method, which is mathematically exact. Nonetheless, the decision-support system also supports the case, in which multiple agents or installation vessels are used in the projects. The numerical study reveals the relation between the process acceleration and charter cost by using two installation vessels. Last, historical data are used for the weather predictions.

Previous literature has reported that users consider hands-free and eyes-free interaction as one of the prime features of IPAs (Intelligent Personal Assistants). Hands-free and eyes-free interaction enables dual tasking. Although users prefer dual tasking with IPAs, it is unknown to what degree current IPAs are compatible with dual tasking. To determine IPA efficiency while dual tasking, we investigate cognitive load in dual-task scenarios with IPAs. In our experiment, we selected a rhythm game as the primary task and everyday IPA requests as secondary tasks. The secondary tasks belonged to four common categories: information search, multimedia control, smart home control, and turn-taking conversations. The findings show that IPAs need significant improvement to support dual tasking. Out of the four categories, only tasks in the smart home and multimedia categories were appropriate for dual tasking, whereas turn-taking conversation and information search had a high cognitive load. Task completion time was significantly different between tasks, but the penalty on the accuracy of the primary task was small. In interviews we found that, due to information abundance in IPA responses and high time pressure during task completion, users tended to make several mistakes. Based on our findings and observations we derive four design recommendations that facilitate dual-tasking while using IPAs.

People with visual impairments face challenges in scene and object recognition, especially in unknown environments. We combined the mobile scene detection framework Apple ARKit with MobileNet-v2 and 3D spatial audio to provide an auditory scene description to people with visual impairments. The combination of ARKit and MobileNet allows keeping recognized objects in the scene even if the user turns away from the object. An object can thus serve as an auditory landmark. With a search function, the system can even guide the user to a particular item. The system also provides spatial audio warnings for nearby objects and walls to avoid collisions. We evaluated the implemented app in a preliminary user study. The results show that users can find items without visual feedback using the proposed application. The study also reveals that the range of local object detection through MobileNet-v2 was insufficient, which we aim to overcome using more accurate object detection frameworks in future work (YOLOv5x).

In this position paper we approach problems concerning critical digital and information literacy with ideas to provide more digestible explanations of abstract concepts through interface design. In particular, we focus on social media platforms where we see the possibility of counteracting the spread of misinformation by providing users with more proficiency through our approaches. We argue that the omnipresent trend to abstract away and hide information from users via UI/UX design opposes their ability to selflearn. This leads us to propose a different framework in which we unify elegant and simple interfaces with nudges that promote a look behind the curtain. Such designs serve to foster a deeper understanding of employed technologies and aim to increase the critical assessment of content encountered on social platforms. Furthermore, we consider users with an intermediary skill level to be largely ignored in current approaches, as they are given no tools to broaden their knowledge without consultation of expert material. The resulting stagnation is exemplified by the tactics of misinformation campaigns, which exploit the ensuing lack of information literacy and critical thinking. We propose an approach to design that sufficiently emancipates users in both aspects by promoting a look behind the abstraction of UI/UX so that an autonomous learning process is given the chance to occur. Furthermore, we name ideas for future research within this area that take our considerations into account.

This paper focuses on the scheduling problem in the offshore wind farm installation process, which is strongly influenced by the offshore weather condition. Due to the nature of the offshore weather condition, i.e., partially predictable and uncontrollable, it is urgent to find a way to schedule the offshore installation process effectively and economically. For this purpose, this work presents a model based on Timed Petri Nets (TPN) approach for the offshore installation process and applies simulated annealing algorithm to find the optimal schedule.

We present SpectroPhone, a surface material sensing approach based on the rear camera of a smartphone and external white LED light sources. Warm and cool white LEDs, as used for dual or quad flashlights in smartphones, differ in their spectral distribution in the red and blue range. Warm and cool white LEDs in combination can produce a characteristic spectral response curve, when their light is reflected from a surface. We show that with warm and cool white LEDs and the rear-camera of a smartphone 30 different materials can be distinguished with an accuracy of 99 \%. Based on a dataset consisting of 13500 images of material surfaces taken at different LED light intensities, we report recognition rates of support vector machines with different parameters.

We present a Mixed Integer Linear Programming (MILP) approach in order to model the non-linear problem of minimizing the tire noise function. In a recent work, we proposed an exact solution for the Tire Noise Optimization Problem, dealing with an APproximation of the noise (TNOP-AP). Here we study the original non-linear problem modeling the EXact- or real-noise (TNOP-EX) and propose a new scheme to obtain a solution for the TNOP-EX. Relying on the solution for the TNOP-AP, we use a Branch&Cut framework and develop an exact algorithm to solve the TNOP-EX. We also take more industrial constraints into account. Finally, we compare our experimental results with those obtained by other methods.

Creating tactile patterns on the body via a spatial arrangement of many tactile actuators offers many opportunities and presents a challenge, as the design space is enormous. This paper presents a VR interface that enables designers to rapidly prototype complex tactile interfaces. It allows for painting strokes on a modeled body part and translates these strokes into continuous tactile patterns using an interpolation algorithm. The presented VR approach avoids several problems of traditional 2D editors. It realizes spatial 3D input using VR controllers with natural mapping and intuitive spatial movements. To evaluate this approach in detail, we conducted a user study and iteratively improved the system. The study participants gave predominantly positive feedback on the presented VR interface (SUS score 79.7, AttrakDiff “desirable”). The final system is released alongside this paper as an open-source Unity project for various tactile hardware.

Public bookcases offer the opportunity to serendipitously discover books and to anonymously share books with others. The set of available books as well as the sharing patterns are highly dynamic, as anybody can freely take or donate books. This makes it difficult for users to see what is available or of interest to them. To support book sharing via public bookcases we developed a mobile AR application that highlights relevant books in the camera viewfinder and that facilitates searching for specific books. The application recognizes books via text and color features on the spine. In a lab study with 15 participants we evaluated our book recognition algorithm and found that it outperforms unaided visual search. We interviewed users of public bookcases and analyzed the bookcases’ setup and rate of change. A subsequent field evaluation of the AR application on nine public bookcases found a recognition accuracy of 80 % for 450 books under different conditions. The proposed approach provides the basis for effectively sharing books via public bookcases.

We propose around-the-head spatial vibrotactile patterns for representing different kinds of notifications. The patterns are defined in terms of stimulus location, intensity profile, rhythm, and roughness modulation. A first study evaluates recall and distinguishability of 30 patterns, as well as agreement on meaning without a predetermined context: Agreement is low, yet the recognition rate is surprisingly high. We identify which kinds of patterns users recognize well and which ones they prefer. Static stimulus location patterns have a higher recognition rate than dynamic patterns, which move across the head as they play. Participants preferred dynamic patterns for comfort. A second study shows that participants are able to distinguish substantially more around-the-head spatial patterns than smartphone-based patterns. Spatial location has the highest positive impact on accuracy among the examined features, so this parameter allows for a large number of levels.

This work presents a multi-leveled model based on Colored Generalized Stochastic Petri nets (CGSPN) approach for offshore wind energy installation. The offshore logistics, which describes the organization of offshore operations, is embedded at the root level. The offshore operations, e.g., loading and sailing, are implemented at the secondary level using sub-models. The large scale of the wind turbine components and the ever-changing offshore weather conditions make the scheduling difficult. The aim is to support the project operators and managers in making decisions with the knowledge of the system behavior obtained through stochastic simulation, in which historical weather data measured on the German North Sea from 1958 to 2007 is used. The numerical results show the influence of decision variables, e.g. initial inventory, on a designed offshore wind farm with a size of 80 wind turbines.

In this work, we statistically analyze publicly available data on the health-related absenteeism of German professional football players and, outgoing from this, develop a machine-learning model for a prognosis of the probability that a player will have a longer health problem during the current season. That prognosis is essential for German insurance companies, since a short illness or injury is covered by the health insurance, whereas a longer absenteeism (over six weeks) is covered by a special insurance. Insurance companies have to calculate the risk for that special case in order offer an appropriate insurance rate. Our model gives an assessment of the risk, and thus plays a vital role in the calculation of the insurance rate that can be offered to a professional football player.

Despite the success in developments of wind energy technology, there remain challenges, for example, in offshore wind energy installation. Due to changeable and unstable offshore weather conditions, it is hard to effectively schedule the installation logistics. In this work, we propose a simulation-based scheduling strategy to help the operators and the project managers, to make the main decisions during the installation to increase efficiency, e.g. how many offshore wind turbines should be loaded onto the installation vessel. The offshore logistic concept is modeled using timed Petri nets (TPN) approach. The timed transitions in the TPN model are assigned with operation times estimated by means of discrete-time Markov chain (DTMC) approach, which uses historical weather data. Besides, operability is introduced in this work as an indicator to evaluate schedules of a certain time period.

Winter sports like skiing are becoming increasingly popular for both competitive and recreational activities. To minimize the risk of injury, new innovations in skiing equipment have been developed in recent years. However, unexpected slope conditions can still increase risks during skiing. The static categorisation of ski slopes in winter sports resorts does not take into account dynamic changes of difficulty due to high traffic volumes or sudden weather changes. Up to now, efforts have been made to measure the current conditions via satellite imaging or installations on the slope. However, this requires intervention in nature and causes high maintenance costs. To solve these issues we present our preliminary design of a wearable system to let skiers implicitly measure current slope conditions during their skiing experience. Audio and motion data are recorded from a prototype mounted on a ski boot. We show that the data generated by the prototype can be successfully classified with a neural network. We collected data from a skiing activity to demonstrate our concept and discuss the identified challenges in fitting the proposed approach to winter sports equipment.

Wearables are getting more and more powerful. Tasks like notifications can be delegated to smartwatches. But the output capabilities of wearables seem to be stuck at displays and vibration. Electrotactile feedback may serve as an energy-efficient alternative to standard vibration feedback. We developed prototypes of wristbands and rings and conducted two studies to compare electrotactile and vibrotactile feedback. The prototypes have either four electrodes for electrotactile feedback or four actuators for vibration feedback. In a first study we analyzed the localization characteristics of the created stimuli. The results suggest more strongly localized sensations for electrotactile feedback, compared to vibrotactile feedback, which was more diffuse. In a second study we created notification patterns for both modalities and evaluated recognition rates, verbal associations, and satisfaction. Although the recognition rates were higher with electrotactile feedback, vibrotactile feedback was judged as more comfortable and less stressful. Overall, the results show that electrotactile feedback can be a viable alternative to vibrotactile feedback for wearables, especially for notification rings.

In this paper, we aim to draw attention towards wake words. Wake words are an integral part of every request addressed to Intelligent Personal Assistants (IPAs). Currently, a request made to an IPA is led by wake words, making a conversation with an IPA more tiresome than a conversation with a human being. The main question we pose in this paper is, whether we can eliminate the use of wake words at least in specific contexts. Based on our experience with IPAs we propose three less burdensome alternatives that avoid the need for speaking wake words in some cases. Based on these approaches we discuss how to design seamless conversations with IPAs.

The vibrotactile funneling illusion is the sensation of a single (non-existing) stimulus somewhere in-between the actual stimulus locations. Its occurrence depends upon body location, distance between the actuators, signal synchronization, and intensity. Related work has shown that the funneling illusion may occur on the forehead. We were able to reproduce these findings and explored five further regions to get a more complete picture of the occurrence of the funneling illusion on the head. The results of our study (24 participants) show that the actuator distance, for which the funneling illusion occurs, strongly depends upon the head region. Moreover, we evaluated the centralizing bias (smaller perceived than actual actuator distances) for different head regions, which also showed widely varying characteristics. We computed a detailed heat map of vibrotactile localization accuracies on the head. The results inform the design of future tactile head-mounted displays that aim to support the funneling illusion.

Smartwatches can be used independently from smartphones, but input tasks like messaging are cumbersome due to the small display size. Parts of the display are hidden during interaction, which can lead to incorrect input. For simplicity, instead of general text input a small set of answer options are often provided, but these are limited and impersonal. In contrast, free-form drawings can answer messages in a very personal way, but are difficult to produce on small displays. To enable precise drawing input on smartwatches we present a magnetic stylus that is tracked on the back of the hand. In an evaluation of several algorithms we show that 3D position estimation with a 7.5x20mm magnet reaches a worst-case 6% relative position error on the back of the hand. Furthermore, the results of a user study are presented, which show that in the case of drawing applications the presented technique is faster and more precise than direct finger input.

Creating tactile patterns for a grid or a 3D arrangement of a large number of actuators presents a challenge as the design space is huge. This paper explores two different possibilities of implementing an easy-to-use interface for tactile pattern design on a large number of actuators around the head. Two user studies were conducted in order to iteratively improve the prototype to fit user needs.

Offshore wind farms provide a promising technology to produce renewable and sustainable energy. Nevertheless, the installation and operation of offshore wind farms pose a particular challenge to the planning and execution of operations. This article aims to identify requirements towards a decision support tool for the installation planning. Therefore, it provides a review of existing research in planning approaches and summarizes the overall planning problem. Afterwards this problem is decomposed into single tasks, according to their planning horizons. This decomposition shows a high level of interconnection between tasks across all levels. Higher levels provide constraints for the tasks on lower levels, while the results of these tasks are incorporated at higher levels. Finally, the article discusses the advantages and disadvantages of different approaches to solve these tasks.

A novel way of distributed discrete event simulation, called approximate distributed discrete event simulation, is presented in this paper. Compared with the classic simulation, the models for approximate simulation give some kind of free margin to the simulator during the execution. This can be used in some cases to reduce the overhead of the simulation, especially the execution time. Since the margin can be adjusted arbitrarily in the range, a trade-off between the simulation precision and the execution time can be achieved this way. It's well known that the execution time of distributed discrete event simulation can't be reduced significantly compared with a sequential simulation when the logical processes are tightly coupled and the lookahead is very short. In this study, a framework of approximate distributed discrete event simulation with some novel algorithms is developed, which is aimed to provide a longer look-ahead and further the trade-off between the simulation precision and the execution time using the free margin provided by the model.

In this paper, we present the enhancement of a lightweight key-policy attribute-based encryption (KP-ABE) scheme designed for the Internet of Things (IoT). The KP-ABE scheme was claimed to achieve ciphertext indistinguishability under chosen-plaintext attack in the selective-set model but we show that the KP-ABE scheme is insecure even in the weaker security notion, namely, one-way encryption under the same attack and model. In particular, we show that an attacker can decrypt a ciphertext which does not satisfy the policy imposed on his decryption key. Subsequently, we propose an efficient fix to the KP-ABE scheme as well as extending it to be a hierarchical KP-ABE (H-KP-ABE) scheme that can support role delegation in IoT applications. An example of applying our H-KP-ABE on an IoT-connected healthcare system is given to highlight the benefit of the delegation feature. Lastly, using the NIST curves secp192k1 and secp256k1, we benchmark the fixed (hierarchical) KP-ABE scheme on an Android phone and the result shows that the scheme is still the fastest in the literature.

A visualization recommender supports the user through automatic visualization generation. While previous contributions primarily concentrated on integrating visualization design knowledge either explicitly or implicitly, they mostly do not consider the user's individual preferences. In order to close this gap we explore online learning of visualization preferences through dueling bandits. Additionally, we consider this challenge from a usability perspective. Through a user study (N = 15), we empirically evaluate not only the bandit's performance in terms of both effectively learning preferences and properly predicting visualizations (satisfaction regarding the last prediction: μ = 85%), but also the participants' effort with respect to the learning procedure (e.g., NASA-TLX = 24:26). While our findings affirm the applicability of dueling bandits, they further provide insights on both the needed training time in order to achieve a usability-aligned procedure and the generalizability of the learned preferences. Finally, we point out a potential integration into a recommender system.

Complex software-based systems involve several stakeholders, their activities and interactions with the system. Vision videos are used during the early phases of a project to complement textual representations. They visualize previously abstract visions of the product and its use. By creating, elaborating, and discussing vision videos, stakeholders and developers gain an improved shared understanding of how those abstract visions could translate into concrete scenarios and requirements to which individuals can relate. [Question/problem] In this paper, we investigate two aspects of refining vision videos: (1) Refining the vision by providing alternative answers to previously open issues about the system to be built. (2) A refined understanding of the camera perspective in vision videos. The impact of using a subjective (or “ego”) perspective is compared to the usual third-person perspective. [Methodology] We use shopping in rural areas as a real-world application domain for refining vision videos. Both aspects of refining vision videos were investigated in an experiment with 20 participants. [Contribution] Subjects made a significant number of additional contributions when they had received not only video or text but also both – even with very short text and short video clips. Subjective video elements were rated as positive. However, there was no significant preference for either subjective or non-subjective videos in general.

Conversational interfaces (CIs) have the potential to empower a broader spectrum of users to independently conduct visual analysis. Yet, recent approaches do not fully consider the user's characteristics. In particular, the objective of matching the user's language has been understudied in visual analysis. In order to close this gap, we introduce an answer space motivated by Grice's cooperative principle for framing personalized communication in complex data situations. We conducted both an online survey (N=76) to analyze communication preferences and a qualitative experiment (N=10) to investigate personalized conversations with an existing CI. In order to match the user's language properly, our results suggest to consider additional user characteristics along with their knowledge level. While mismatching communication preferences triggers negative reactions, a preference-aligned communication evokes positive reactions. As our analysis confirms the importance of matching the user's language in visual analysis, we provide design implications for future CIs.

Bewegungsmangel ist laut WHO zu einem der führenden Risikofaktoren für gesundheitliche Probleme geworden (WHO 2007: 8) und resultiert aus unserer veränderten Lebens- und Arbeitswelt mit langen körperlichen Ruhezeiten. Neben diesen Phasen, die beispielsweise sitzend am Büroarbeitsplatz verbracht werden, spielt hierbei auch unser Mobilitätsverhalten eine zentrale Rolle. Knapp die Hälfte der Wege, die mit dem Automobil zurückgelegt werden, sind fünf Kilometer lang oder kürzer (infas & DLR 2010, 41). Diese Streckenlängen können auch durch Fuß- und Radverkehr als Bestandteile der aktiven Mobilität geleistet werden. An dieser Stelle setzt das Forschungsprojekt „Aktive Navigation“ der Forschungsinitiative „Mobiler Mensch: Intelligente Mobilität in der Balance von Autonomie, Vernetzung und Security“ der Leibniz Universität Hannover an. Aufbauend auf der Nutzung von Wearables und Smartphones wird eine App entwickelt, die basierend auf der Vorhersage der täglichen Aktivität der Nutzenden eine Route zum Ziel auswählt. Die Routenwahl schließt andere Verkehrsmittel mit ein, soll insgesamt aber dazu dienen, die tägliche Schrittzahl und damit die körperliche Aktivität zu erhöhen.

In this work we improve previous approaches based on genetic algorithms (GA) to solve sudoku puzzles. Those approaches use random swap mutations and filtered mutations, where both operations result in relatively slow convergence, the latter suffering a bit less. We suggest to improve GA based approaches by an intermediate local optimization step of the population. Compared to the previous approaches our approach is superior in terms of convergence rate, success rate and speed. As consequence we find the optimum with one population member and within one generation in a few milliseconds instead of nearly one minute.

Nowadays, wearables can easily monitor and display physical activities throughout the day. Health recommendations are often used to set daily goals, but these barely take individual requirements into account. In addition, due to limited individual adaptability, there are various life situations in which these goals are not achieved due to missing motivation or time. In this position paper we discuss in particular how health recommendations can be integrated into everyday life and what challenges arise. We also address spatial requirements that are necessary for an active lifestyle.

Everyday mobility encompasses different forms of public and private transportation and different forms of physical activity. However, in general everyday mobility does not involve substantial levels of physical activity. There are sometimes structural reasons or a lack of motivation and time to realize an active lifestyle in the context of mobility. The goal of this workshop is to investigate ways to integrate physical activity into everyday mobility in accordance with widely accepted health recommendations. We aim to explore wearable and ambient systems that sense and support active navigation as well as conceptual aspects from a variety of perspectives, such as persuasive technologies, and thus invite researchers from different disciplines to contribute their point of view by means of position papers, posters, and demonstrations. One planned outcome of this workshop is a set of design guidelines for navigation systems that explicitly consider health aspects. For the full-day workshop we aim to explore requirements and design challenges in a creative setting.

Pest population prognosis helps the growers in the greenhouse to keep the pest population below the threshold efficiently. INSIM is one of the recognized pest population simulators. However, the implementation of the INSIM simulation faces some difficulties to be executed as a web service. Thus, we propose a Java-based web application using the mathematical model used in INSIM. Additionally to the known model, our implementation is able to give prognosis boundaries based on uncertainty of the temperature development and pest count. The proposed JIS gives lower and upper estimation of the pest population with the mean accuracy of 66.67% against our experimental validation data. Furthermore, the relationship between the area coverage for each yellow sticky trap and its accuracy percentage is investigated.

Receiving and reacting to notifications on mobile devices can be cumbersome. We propose MuscleIO, the use of electrical muscle stimulation (EMS) for notification output and electromyography (EMG) for reacting to notifications. Our approach provides a one-handed, eyes-free, and low-effort way of dealing with notifications. We built a prototype that interleaves muscle input and muscle output signals using the same electrodes. EMS and EMG alternate such that the EMG input signal is measured in the gaps of the EMS output signal, so voluntary muscle contraction is measured during muscle stimulation. Notifications are represented as EMS signals and are accepted or refused either by a directional or a time-based EMG response. A lab user study with 12 participants shows that the directional EMG response is superior to the time-based response in terms of reaction time, error rate, and user preference. Furthermore, the directional approach is the fastest and the most intuitive for users compared to a button-based smartwatch interface as a baseline.

Digital pens emit ink on paper and digitize handwriting. The range of the pen is typically limited to a special writing surface on which the pen's tip is tracked. We present Pentelligence, a pen for handwritten digit recognition that operates on regular paper and does not require a separate tracking device. It senses the pen tip's motions and sound emissions when stroking. Pen motions and writing sounds exhibit complementary properties. Combining both types of sensor data substantially improves the recognition rate. Hilbert envelopes of the writing sounds and mean-filtered motion data are fed to neural networks for majority voting. The results on a dataset of 9408 handwritten digits taken from 26 individuals show that motion+sound outperforms single-sensor approaches at an accuracy of 78.4% for 10 test users. Retraining the networks for a single writer on a dataset of 2120 samples increased the precision to 100% for single handwritten digits at an overall accuracy of 98.3%.

Tactile patterns are a means to convey general direction information to pedestrians (for example when turning right) and specific navigation instructions (for example when approaching the stairs). Tactile patterns are especially helpful for people with visual impairments in navigation scenarios and can also be used to deliver general notifications. This workshop paper is supposed to spark a discussion within the workshop about correctly identifying requirements and other needs of the visually impaired population in order to create a useful guidance tool to eventually replace the white cane as a primary navigation tool for the visually impaired.

Modern technologies enable data analysis in scenarios where keyboard and mouse are not available. Research on multimodality in visual analytics is facing this challenge. But existing approaches consider exclusively static environments with large screens. Therefore, we envision Valletto, a prototypical tablet app which allows the user to generate and specify visualizations through a speech-based conversational interface, through multitouch gestures, and through a conventional GUI interface. We conducted an initial expert evaluation to gain information on the modality function mapping and for the integration of different modalities. Our aim is to discuss design and interaction considerations in a mobile context which fits the user's daily life.

Emoji, a set of pictographic Unicode characters, have seen strong uptake over the last couple of years. All common mobile platforms and many desktop systems now support emoji entry and users have embraced their use. Yet, we currently know very little about what makes for good emoji entry. While soft keyboards for text entry are well optimized, based on language and touch models, no such information exists to guide the design of emoji keyboards. In this article, we investigate of the problem of emoji entry, starting with a study of the current state of the emoji keyboard implementation in Android. To enable moving forward to novel emoji keyboard designs, we then explore a model for emoji similarity that is able to inform such designs. This semantic model is based on data from 21 million collected tweets containing emoji. We compare this model against a solely description-based model of emoji in a crowdsourced study. Our model shows good performance in capturing detailed relationships between emoji.

Electrical Muscle Stimulation (EMS) recently received considerable attention in the HCI community. By applying small signals to the user's body, different types of movement can be generated. These movements allow designers to create more meaningful and embodied haptic feedback compared to vibrotactile feedback. This advantage also comes with further technical and practical challenges which need to be tackled. These challenges include a fine grained calibration procedure and a close contact to the user's body at specific on-body locations. This tutorial gives an overview about current research projects, challenges, and opportunities to use EMS for providing rich embodied feedback followed by a hands on experience. The main goal of this tutorial is that participants get a basic understanding of how EMS works and how systems that are using EMS can be developed and evaluated.

The human body reveals emotional and bodily states through measurable signals, such as body language and electroencephalography. However, such manifestations are difficult to communicate to others remotely. We propose EmotionActuator, a proof-of-concept system to investigate the transmission of emotional states in which the recipient performs emotional gestures to understand and interpret the state of the sender.We call this kind of communication embodied emotional feedback, and present a prototype implementation. To realize our concept we chose four emotional states: amused, sad, angry, and neutral. We designed EmotionActuator through a series of studies to assess emotional classification via EEG, and create an EMS gesture set by comparing composed gestures from the literature to sign-language gestures. Through a final study with the end-to-end prototype interviews revealed that participants like implicit sharing of emotions and find the embodied output to be immersive, but want to have control over shared emotions and with whom. This work contributes a proof of concept system and set of design recommendations for designing embodied emotional feedback systems.

Large scale distributed simulation should be well planned before the execution, since applying unnecessary hardware only wastes our time and money. On the other side, we need enough hardware to achieve an acceptable performance. Thus, it is considerable to estimate the performance of a large scale distributed simulation before the execution. Such an estimation also improves the efficiency of the applied hardware in many cases due to the optimization on the simulation algorithm and on the partition of the model. In this paper, we show our approaches to estimate the performance, especially the duration of execution, of a large scale distributed simulation system built on a large set of homogeneous hardware, using a small set of hardware of the same type. Our basic idea is to simulate a distributed simulation in a sequential way for a short time considering all the costs and benefits of the distribution. The results of our case study show that our approaches are able to provide meaningful estimations.

In this paper, we establish a relation between sealed-bid e-auction and e-cheque by proposing a transformation technique which transforms a secure sealed-bid e-auction into a secure e-cheque scheme. Although the application scenario differs, we notice that the scheme structure and fundamental security properties in both schemes are similar, namely, unforgeability, anonymity and indistinguishability. As a proof of concept, we apply the transformation technique on the classic Sakurai and Miyazaki sealed-bid e-auction scheme and obtain a secure e-cheque scheme.

Current virtual and augmented reality head-mounted displays usually include no or only a single vibration motor for haptic feedback and do not use it for guidance. We present HapticHead, a system utilizing multiple vibrotactile actuators distributed in three concentric ellipses around the head for intuitive haptic guidance through moving tactile cues. We conducted three experiments, which indicate that HapticHead vibrotactile feedback is both faster (2.6 s vs. 6.9 s) and more precise (96.4% vs. 54.2% success rate) than spatial audio (generic head-related transfer function) for finding visible virtual objects in 3D space around the user. The baseline of visual feedback is as expected more precise (99.7% success rate) and faster (1.3 s) in comparison, but there are many applications in which visual feedback is not desirable or available due to lighting conditions, visual overload, or visual impairments. Mean final precision with HapticHead feedback on invisible targets is 2.3° compared to 0.8° with visual feedback. We successfully navigated blindfolded users to real household items at different heights using HapticHead vibrotactile feedback independently of a head-mounted display.

Exploratory data analysis is an essential step in discovering patterns and relationships in data. However, the exploration may start without a clear conception about what attributes to pick or what visualizations to choose in order to develop an understanding of the data. In this work we aim to support the exploration process by automatically choosing attributes according to an information-theoretic measure and by providing a simple means of navigation through the space of visualizations. The system suggests data attributes to be visualized and the visualization's type and appearance. The user intuitively modifies these suggestions by performing swiping gestures on a tablet device. Attribute suggestions are based on the mutual information between multiple random variables (MMI). The results of a preliminary user study (N = 12 participants) show the applicability of MMI for guided exploratory data analysis and confirm the system's general usability (SUS score: 74).

Position determination in an indoor environment has become a widely discussed problem, due to the growing complexity of building layouts and the lack of any natural heuristics for orientation as compared to the case outdoors. Additionally there is no universal standard for indoor positioning, such as GPS, which however cannot be used for this purpose. Locating oneself in a building serves an increasingly vital function, especially in time-critical scenarios such as airports etc. The use of expensive hardware may assist in solving this problem, which has been studied thoroughly with different technologies being used to achieve a precision of within a few meters. Nevertheless these methods have remained in the academic realm for the most part. This is largely due to the high costs and labour of such hardware installations and the construction of software to interpret the measurements. The goal of this paper is to use existing wireless LAN access points in a building and user-provided smartphones to create a cost-effective positioning system, by omitting the labour and cost of altering building infrastructure, and at the same time simplifying the construction of classifiers for real-life use-cases. An alternative approach using image recognition techniques is presented, for a purely web-based solution.

A high level of presence is an important aspect of immersive virtual reality applications. However, presence is difficult to achieve as it depends on the individual user, immersion capabilities of the system (visual, auditory, and tactile) and the concrete application. We use a vibrotactile grid around the head in order to further increase the level of presence users feel in virtual reality scenes. In a between-groups comparison study the vibrotactile group scored significantly higher in a standardized presence questionnaire compared to the baseline of no tactile feedback. This suggests the proposed prototype as an additional tool to increase the level of presence users feel in virtual reality scenes.

Determination of the absolute geographical position has become every day routine, using the Global Positioning System (GPS), despite the prior existence of maps. However no equally universal solution has been developed for determining one’s location inside a building, which is an equally relevant problem statement, for which GPS cannot be used. Existing solutions usually involve additional infrastructure on the end of the location provider, such as beacon installations or particular configurations of wireless access points. These solutions are generally facilitated by additional native mobile applications on the client device, which connect to this infrastructure. We are aware of such solutions, but believe these to be lacking in simplicity. Our approach for indoor positioning alleviates the necessity for additional hardware by the provider, and software installation by the user. We propose to determine the user’s position inside a building using only a photo of the corridor visible to the user, uploading it to a local positioning server, accessible using a browser, which performs a classification of the photo based on a Neural Network approach. Our results prove the feasibility of our approach. One floor of the university’s building with partially very similar corridors has been learned by a deep convolutional neural network. A person lost in the building simply accesses the positioning server’s website and uploads a photo of his current line of sight. The server responds by generating and displaying a map of the building with the user’s current position and current direction.

Compression feedback uses inflatable straps to create uniform pressure sensations around limbs. Lower-pressure stimuli are well suited as a feedback channel for, e.g., notifications. However, operating compression feedback systems at higher pressure levels allows to physically inhibit movement. Here, we describe this modality and present a pervasive jogging game that employs physical inhibition to push runners to reach checkpoints in time.

In this paper, we cryptanalyze a receipt-free electronic sealed-bid auction scheme and show that it is forgeable under the known bid attack. Specifically, we show that a malicious sealer can forge the sealed-bid with non-negligible probability. Besides, we also propose a possible fix for the attack.

In this paper, we cryptanalyze two sealed-bid auction schemes and show that both schemes are not secure against the known-bid attack. In the first scheme, we show that a dishonest sealer can swap the price of a sealed-bid and yet its validity remains intact; in the second scheme, we show that a dishonest auctioneer can forge a bidder's bid if the bidder was once a winning bidder. We propose a workaround for the former using a designated confirmer signature but not the latter, which is fundamentally flawed.

Current mobile devices commonly use vibration feedback to signal incoming notifications. However, vibration feedback exhibits strong attention capture, limiting its use to short periods and prominent notifications. Instead, we investigate the use of compression feedback for notifications, which scales from subtle stimuli to strong ones and can provide sustained stimuli over longer periods. Compression feedback utilizes inflatable straps around a user's limbs, a form factor allowing for easy integration into many common wearables. We explore technical aspects of compression feedback and investigate its psychophysical properties with several lab and in situ studies. Furthermore, we show how compression feedback enables reactive feedback. Here, deflation patterns are used to reveal further information on a user's query. We also compare compression and vibrotactile feedback and find that they have similar performance.

Electrical muscle stimulation (EMS) has been used successfully in HCI to generate force feedback and simple movements both in stationary and mobile settings. However, many natural limb movements require the coordinated actuation of multiple muscles. Off-the-shelf EMS devices are typically limited in their ability to generate fine-grained movements, because they only have a low number of channels and do not provide full control over the EMS parameters. More capable medical devices are not designed for mobile use or still have a lower number of channels and less control than is desirable for HCI research. In this paper we present the concept and a prototype of a 20-channel mobile EMS system that offers full control over the EMS parameters. We discuss the requirements of wearable multi-electrode EMS systems and present the design and technical evaluation of our prototype. We further outline several application scenarios and discuss safety and certification issues.

Electrical muscle stimulation (EMS) is a promising wearable haptic output technology as it can be miniaturized and delivers a wide range of tactile and force output. However, prototyping EMS applications is currently challenging and requires detailed knowledge about EMS. We present a toolkit that simplifies prototyping with EMS and serves as a starting point for experimentation and user studies. It consists of (1) a hardware control module that uses off-the-shelf EMS devices as safe signal generators, (2) a simple communication protocol, and (3) a set of control applications for prototyping. The interactivity allows hands-on experimentation with our sample control applications.

A Multi-Agent algorithm works by using at least two agents to create a synergistic effect, resulting in an emergence of new possibilities which are not programmed implicitly into the various agents. To achieve this synergistic effect the algorithm has to provide the possibility to communicate and consecutively allow cooperation between the agents. Considering the use of multi-agent algorithms in search and rescue scenarios the targeted effect of the emergence is on one hand a more effective search and rescue process or on the other hand only an optimized rescue process. This paper examines the number of agents that is needed for the Multi-Agent Flood algorithm to yield the most beneficial ratio between the used number of agents and time it takes to complete the search process. Our studies show that adding more robots may not be cost efficient for the search and rescue process. This in turn allows for a better planning and coordination of robotic search teams, as the number of needed agents can be anticipated and the possible transport logistics of robots can be optimized.

The work in progress described in this paper has the objective to implement a beehive monitoring system to monitor essential parameters of a bee hive (such as temperature, sound, weight) and additionally including an image recognition algorithm to observe the degree of infestation with Varroa mites. Mites should be detected at the entrance and statistics about the degree of infestation should be made available by a web interface. As ultimate approach to fight mites without chemicals the coordinates of the mites are to be detected and a laser will be used to kill them. This work describes approaches relevant to all steps of the aforementioned procedure, however it is still work in progress and the components of the approach still have to be integrated into one system that is deployable in practice.

In what we call the focused-casual continuum, users pick how much control they want to have when interacting. Through offering several different ways for interaction, such interfaces can then be more appropriate for, e.g., use in some social situations, or use when exhausted. In a very basic example, an alarm clock could offer one interaction mode where an alarm can only be turned off, while in another, users can choose between different snooze responses. The first mode is more restrictive but could be controlled with one coarse gesture. Only when the user wishes to pick between several responses, more controlled and fine interaction is needed. Low control, more casual interactions can take place in the background or the periphery of the user, while focused interactions move into the foreground. Along the focused-casual continuum, a plethora of interaction techniques have their place. Currently, focused interaction techniques are often the default ones. In this chapter, we thus focus more closely on techniques for casual interaction, which offer ways to interact with lower levels of control. Presented use cases cover scenarios such as text entry, user recognition, tangibles, or steering tasks. Furthermore, in addition to potential benefits from applying casual interaction techniques during input, there is also a need for feedback which does not immediately grab our attention, but can scale from the periphery to the focus of our attention. Thus, we also cover several such feedback methods and show how the focused-casual continuum can encompass the whole interaction.

Current soft keyboards for emoji entry all present emoji in the same way: in long lists, spread over several categories. While categories limit the number of emoji in each individual list, the overall number is still so large, that emoji entry is a challenging task. The task takes particularly long if users pick the wrong category when searching for an emoji. Instead, we propose a new zooming keyboard for emoji entry. Here, users can see all emoji at once, aiding in building spatial memory where related emoji are to be found. We compare our zooming emoji keyboard against the Google keyboard and find that our keyboard allows for 18% faster emoji entry, reducing the required time for one emoji from 15.6s to 12.7s. A preliminary longitudinal evaluation with three participants showed that emoji entry time over the duration of the study improved at up to 60% to a final average of 7.5s.

In mobile contexts guidance towards objects is usually done through the visual channel. Sometimes this channel is overloaded or not appropriate. A practicable form of haptic feedback is challenging. Electrical muscle stimulation (EMS) can generate mobile force feedback but has a number of drawbacks. For complex movements several muscles need to be actuated in concert and a feedback loop is necessary to control movements. We present an approach that only requires the actuation of six muscles with four pairs of electrodes to guide the index finger to a 2D point and let the user perform mid-air disambiguation gestures. In our user study participants found invisible, static target positions on top of a physical box with a mean 2D deviation of 1.44 cm from the intended target.

In this course, participants create their own prototypes using electrical-muscle stimulation. We provide a ready-to-use device and toolkit consisting of electrodes, microcontroller, and an off-the-shelve muscle stimulator that allows for programmatically actuating the user's muscles directly from mobile devices.

Current generation virtual reality (VR) and augmented reality (AR) head-mounted displays (HMDs) usually include no or only a single vibration motor for haptic feedback and do not use it for guidance. We present HapticHead, a system utilizing 20 vibration motors distributed in three concentric ellipses around the head to give intuitive haptic guidance hints and to increase immersion for VR and AR applications. Our user study indicates that HapticHead is both faster (mean=3.7s, SD=2.3s vs. mean=7.8s, SD=5.0s) and more precise (92.7% vs. 44.9% hit rate) than auditory feedback for the purpose of finding virtual objects in 3D space around the user. The baseline of visual feedback is as expected more precise (99.9% hit rate) and faster (mean=1.5s, SD=0.6s) in comparison but there are many applications in which visual feedback is not desirable or available due to lighting conditions, visual overload, or visual impairments.

Plagiarism in online learning environments has a detrimental effect on the trust of online courses and their viability. Automatic plagiarism detection systems do exist yet the specific situation in online courses restricts their use. To allow for easy automated grading, online assignments usually are less open and instead require students to fill in small gaps. Therefore solutions tend to be very similar, yet are then not necessarily plagiarized. In this paper we propose a new approach to detect code re-use that increases the prediction accuracy by dynamically removing parts in assignments which are part of almost every assignment—the so called common ground. Our approach shows significantly better F-measure and Cohen's Kappa results than other state of the art algorithms such as Moss or JPlag. The proposed method is also language agnostic to the point that training and test data sets can be taken from different programming languages.

Distributed discrete event simulation is an important approach for enabling the modeling and analysis of the behavior of large systems. This approach presents a major problem, namely, the possible low performance due to the excessive overhead in synchronizing the distributed logical processes. To counter this, our approach to distributed discrete event simulation involves conservative synchronization and its acceleration using dynamic estimation of process-to-process look-ahead with a feedback mechanism. This mechanism allows for the estimation of a larger look-ahead, which may be invalidated and recalculated during the course of the simulation, if one of the processes obtains more detailed knowledge. In this work, we extend the dynamically estimated look-ahead, on the basis of the local state of the logical processes, by exchanging conditional look-aheads, in conjunction with the broadcast of invalidation announcements. A notable reduction in runtime in various cases is thus achieved, especially when the estimated look-ahead is stochastically too conservative.

Electrical muscle stimulation (EMS) is a promising wearable haptic output technology as it can be miniaturized considerably and delivers a wide range of haptic output. However, prototyping EMS applications is challenging. It requires detailed knowledge and skills about hardware, software, and physiological characteristics. To simplify prototyping with EMS in mobile and wearable situations we present the Let Your Body Move toolkit. It consists of (1) a hardware control module with Bluetooth communication that uses off-the-shelf EMS devices as signal generators, (2) a simple communications protocol to connect mobile devices, and (3) a set of control applications as starting points for EMS prototyping. We describe EMS-specific parameters, electrode placements on the skin, and user calibration. The toolkit was evaluated in a workshop with 10 researchers in haptics. The results show that the toolkit allows to quickly generate non-trivial prototypes. The hardware schematics and software components are available as open source software.

Interaction with mobile devices currently requires close engagement with them. For example, users need to pick them up and unlock them, just to check whether the last notification was for an urgent message. But such close engagement is not always desirable, e.g., when working on a project with the phone just laying around on the table. Instead, we explore around-device interactions to bring up and control notifications. As users get closer to the device, more information is revealed and additional input options become available. This allows users to control how much they want to engage with the device. For feedback, we use a custom LED-matrix display prototype on the edge of the device. This allows for coarse, but bright, notifications in the periphery of attention, but scales up to allow for slightly higher resolution feedback as well.

Swarm algorithms are often used for the generation of graphs. The generated graphs are mostly planar, inexpensive and fault-tolerant. In this work we evaluate the graphs produced by a swarm algorithm with respect to the properties and the quality of the found graphs and to the runtime requirements. The algorithm under consideration is essentially a simulation of the foraging of the slime mold Physarum polycephalum. Especially emphasized are the properties of the algorithm, since its deployment in many other works is limited to the existence of a graph solution, not reporting however the quality of the graph and runtime requirements of the algorithm. We compare the quality of the resulting graphs and the runtime of the algorithm to classical algorithms from graph theory. Our results show that the slime mold algorithm has some interesting features, however it is not the best means to construct graphs of large sets of nodes in terms of efficiency of the algorithm or quality of the outcome.

Electromyography (EMG) and electrical muscle stimulation (EMS) are promising technologies for muscle sensing and actuation in wearable interfaces. The required electrodes can be manufactured to form a thin layer on the skin. We discuss requirements and approaches for EMG and EMS as on-skin technologies. In particular, we focus on fine-grained muscle sensing and actuation with an electrode grid on the lower arm. We discuss a prototype, scenarios, and open issues.

One important aim in tire industry when finalizing a tire design is the modeling of the noise characteristics as received by the passengers of the car. In previous works, the problem was studied using heuristic algorithms to minimize the noise by looking for a sequence under constraints. These constraints are imposed by tire industry. We present a new technique to compute the noise. We also propose an integer linear program based on that technique in order to solve this problem and find an optimal sequence. Our study shows that the integer linear programming approach shows significant improvement of the found tire designs, however it has to be improved further to meet the calculation time restrictions for real world problem size.

We present a framework for realization of a decentralized decision support system for deployment in production scenarios with a low level of automation, such as in multi-site construction. Furthermore we present the insights concerning the improvements of the production process when applying online simulation based optimization methods in that scenarios. Our solution shows how to realize a central control and decision support station with special focus on easy connection to the possible multiple construction sites and on high usability for nonexperts. Our framework is able to connect to a large number of modeling, simulation and analysis tools. For sake of usability it turned out, that only dialogue-based communication with the end user seems applicable in those scenarios, where often only simple devices are present.

With the increasing popularity of smartwatches over the last years, there has been a substantial interest in novel input methods for such small devices. However, feedback modalities for smartwatches have not seen the same level of interest. This is surprising, as one of the primary function of smartwatches is their use for notifications. It is the interrupting nature of current notifications on smartwatches that has also drawn some of the more critical responses to them. Here, we present a subtle notification mechanism for smartwatches that uses light scattering in a wearer's skin as a feedback modality. This does not disrupt the wearer in the same way as vibration feedback and also connects more naturally with the user's body.

Current generation virtual reality (VR) and augmented reality (AR) head-mounted displays (HMDs) usually include no or only a single vibration motor for haptic feedback and do not use it for guidance. In a previous work, we presented HapticHead, a potentially mobile system utilizing vibration motors distributed in three concentric ellipses around the head to give intuitive haptic guidance hints and to increase immersion for VR and AR applications. The purpose of this paper is to explore potential application scenarios and aesthetic possibilities of the proposed concept in order to create an active discussion amongst workshop participants.

Pointing is one of the most basic interaction methods for 3D user interfaces. Previous work has shown that visual feedback improves such actions. Here we investigate if electrical muscle stimulation (EMS) and vibration is beneficial for 3D virtual hand pointing. In our experiment we used a 3D version of a Fitts' task to compare visual feedback, EMS, vibration, with no feedback. The results demonstrate that both EMS and vibration provide reasonable addition to visual feedback. We also found good user acceptance for both technologies.

We present a framework for realization of a decentralized decision support system for deployment in production scenarios with a low level of automation, such as in multi-site construction. Our solution shows how to realize a central control and decision support station. Special focus is on easy connection to the possible multiple construction sites and on high usability for non-experts. Our framework is able to connect to a large number of modeling, simulation and analysis tools. For sake of usability it turned out, that only dialogue-based communication with the end user seems applicable in those scenarios, where often only simple devices are present.

Many MOOCs report high drop off rates for their students. Among the factors reportedly contributing to this picture are lack of motivation, feelings of isolation, and lack of interactivity in MOOCs. This paper investigates the potential of gamification with social game elements for increasing retention and learning success. Students in our experiment showed a significant increase of 25% in retention period (videos watched) and 23% higher average scores when the course interface was gamified. Social game elements amplify this effect significantly – students in this condition showed an increase of 50% in retention period and 40% higher average test scores.

In this work we demonstrate how the deployment of several types of agents increases the efficiency and the overall success concerning the task to explore unknown terrain, and finding a pathbetween a starting point and various points of interest. The used agents have different capabilities that are typically foundin technical assistance systems used in search and rescueoperations. In our test cases, the environments to be explored have both, regular characteristics like a maze or a building as well as irregular structures. Our simulations using heterogeneous and cooperating agent populationsshow, that this approach is superior to homogeneous populations, with a higher rate of finding the destinations and in shorter time.

Online applications such as e-auction, e-voting, and e-cash require common security properties such as integrity, unforgeability, confidentiality, non-repudiation, authentication, and anonymity. In this paper, besides identifying the security properties needed by these three applications, we also discuss the importance of access control. We show that undeniable signature schemes and its variants fulfil the security requirements and access control needed by the applications. We also propose a generic method to combine an undeniable signature scheme with a trapdoor function for constructing the applications mentioned above.

In relaxed living room settings, using a phone to control the room can be inappropriate or cumbersome. Instead of such explicit interactions, we enable implicit control via a posture-sensing couch. Users can then, e.g., automatically turn on the reading lights when sitting down.

In the focused-casual continuum, users are given a choice of how much they wish to engage with an interface. In situations where they are, e.g., physically encumbered, they may wish to trade some control for the convenience of interacting at all. Currently, most devices only offer focused interaction capabilities or restrict users to binary foreground/background interaction choices. In casual interactions, users consciously pick a way to interact that is suitable for their desired engagement level. Users will be expecting devices to offer several ways for control along the engagement scale.

Pedestrian navigation systems require users to perceive, interpret, and react to navigation information. This can tax cognition as navigation information competes with information from the real world. We propose actuated navigation, a new kind of pedestrian navigation in which the user does not need to attend to the navigation task at all. An actuation signal is directly sent to the human motor system to influence walking direction. To achieve this goal we stimulate the sartorius muscle using electrical muscle stimulation. The rotation occurs during the swing phase of the leg and can easily be counteracted. The user therefore stays in control. We discuss the properties of actuated navigation and present a lab study on identifying basic parameters of the technique as well as an outdoor study in a park. The results show that our approach changes a user's walking direction by about 16°/m on average and that the system can successfully steer users in a park with crowded areas, distractions, obstacles, and uneven ground.

The construction of fault-tolerant graphs is a trade-off between costs and degree of fault-tolerance. Thus the construction of such graphs can be viewed as a two-criteria optimization problem. Any algorithm therefore should be able to generate a Pareto-front of graphs so that the right graph can be chosen to match the application and the user’s need. In this work algorithms from three different domains for the construction of fault-tolerant graphs are evaluated. Classical graph-theoretic algorithms, optimization and bio-inspired approaches are compared regarding the quality of the generated graphs as well as concerning the runtime requirements. As result, recommendations for the application of the right algorithm for a certain problem class can be concluded.

Haptic feedback allows leveraging other faculties such as proprioception instead of using the visual sense, which is often overloaded with traditional UIs. However, most haptic technologies have been away from the current trend in Human-Computer Interaction (HCI) which is miniaturization (eg, mobile, wearable). Therefore haptic techniques, such as force feedback, tend to stay inside labs. In fact, most haptic devices resist miniaturization because they require physical motors and mechanics which do not scale down easily. Researchers have proposed miniaturizing and simplifying haptic devices by using electrical-muscle stimulation as to actuate the muscles directly, rather than actuating through mechanics. Electrical muscle stimulation (EMS) uses a small current to elicit action on the motor fibers/nerves, causing an involuntary contraction on the user’s body.

In this study several algorithms for the generation of inexpensive and fault-tolerant graphs are evaluated with respect to the quality of the found graphs and to the runtime requirements. A special focus lies on the properties of the algorithm that basically is a simulation of the foraging of the slime mold Physarum polycephalum, since in many other works the deployment of this algorithm does not go beyond the conclusion, that the algorithm is capable to generate a graph, while quality of the graph and runtime requirements of the algorithm are not reported. Our results show that the slime mold algorithm has some interesting features, however it is not the best means to construct highly efficient graphs out of large sets of nodes.

Planning in a multi-site, non-mass production environment is a special challenge because of several sources of uncertainty. Unlike in mass production facilities, in our setting the current state at all sites cannot be determined easily and exactly due to the spatial distribution of sites and the low degree of automation. For re-planning in case of failures, the possible alternative actions have to be formalized on the decision making facility, where the possible alternatives will then be determined and evaluated. In this work, we will present the necessary components for an automated evaluation of alternatives and decision support procedure. The main challenges are the formalization of product plans including alternative steps and the non-automated collection or assessment of the distributed system state of all sites. In our experiments we evaluate different state update intervals and the effect on prediction accuracy. It turns out, that even sparse updates show significant improvement on the production time in comparison to only local static decisions.

We present a novel way to recognize users by the way they press a button. Our approach allows low-effort and fast interaction without the need for augmenting the user or controlling the environment. It eschews privacy concerns of methods such as fingerprint scanning. Button pressing behavior is sufficiently discriminative to allow distinguishing users within small groups. This approach combines recognition and action in a single step, e.g., getting and tallying a coffee can be done with one button press. We deployed our system for 5 users over a period of 4 weeks and achieved recognition rates of 95% in the last week. We also ran a larger scale but short-term evaluation to investigate effects of group size and found that our method degrades gracefully for larger groups.

Robots deployed in Search and Rescue missions are required to act autonomously, since in disaster scenarios even a remote control of the robots might not be possible anymore. Additionally it is desirable to use several of these robots at once, since the search for survivors is a time-critical task, and the time to find victims should in the best case scale with the number of robots. In order to achieve this scaling the robots have to communicate and cooperate. This paper discusses how to optimize the search and rescue mission with multiple autonomous yet cooperating robots, evaluating different communication patterns to speed up the search process. Emphasis lies on the evaluation of the diverse types of communication methods, which can be direct, indirect or a combination thereof. Our studies show, that the combination of direct and indirect communication optimizes the search and rescue process. Further using a combined method of data transfer between the agents provides robust communication between the robots, improving the search efficiency.

Universal Simulation Engine (USE) is a C++ library providing a model-independent environment for Discrete Event Simulation (DES) tasks. Unlike most simulators, USE focuses on the general simulation technology and integrates many features, which are necessary to build a correct and efficient simulation system. It is aimed at providing a professional environment to reduce the cost of modeling as well as the execution time of the simulation for almost all DES models. Developers may use USE as an open framework to build models very efficiently. USE also supports many advanced features such as Distributed Discrete Event Simulation (DDES), Virtual Environments (VE), Online Simulation (OS), dynamic coupling / decoupling of sub-models, etc. This paper introduces the distinctive features of USE for practical implementation of DES, DDES and VE systems. We also evaluate the performance of USE by comparison with existing simulators.

Universal Simulation Engine (USE) is a C++ library providing a model-independent environment for Discrete Event Simulation (DES) tasks. Unlike most simulators, USE focuses on the general simulation technology and integrates many features, which are necessary to build a correct and efficient simulation system. It is aimed at providing a professional environment to reduce the cost of modeling as well as the execution time of the simulation for almost all DES models. Developers may use USE as an open framework to build models very efficiently. USE also supports many advanced features such as Distributed Discrete Event Simulation (DDES), Virtual Environments (VE), Online Simulation (OS), dynamic coupling / decoupling of sub-models, etc. This paper introduces the distinctive features of USE for practical implementation of DES, DDES and VE systems. We also evaluate the performance of USE by comparison with existing simulators.

The amount of logistical data in the automotive industry drastically increases due to digitalization and data that is automatically generated due to Auto-ID-Technologies. However, new methods need to be devised to make sense of this data, in particular when users are mobile, and when users need to collaborate to solve complex logistical tasks, such as resource scheduling. We propose a visualization method for hierarchical event data that is designed for tablets. The main design goals have been to foster collaboration and enable mobility. Our think aloud user study shows that both the event recognition and understanding of the participants improved with the proposed solution.

Most common forms of haptic feedback use vibration, which immediately captures the user's attention, yet is limited in the range of strengths it can achieve. Vibration feedback over extended periods also tends to be annoying. We present compression feedback, a form of haptic feedback that scales from very subtle to very strong and is able to provide sustained stimuli and pressure patterns. The demonstration may serve as an inspiration for further work in this area, applying compression feedback to generate subtle, intimate, as well as intense feedback.

Free-hand interaction becomes a common technique for interacting with large displays. At the same time, providing haptic feedback for free-hand interaction is still a challenge, particularly feedback with different characteristics (i.e., strengths, patterns) to convey particular information. We see electrical muscle stimulation (EMS) as a well-suited technology for providing haptic feedback in this domain. The characteristics of EMS can be used to assist users in learning, manipulating, and perceiving virtual objects. One of the core challenges is to understand these characteristics and how they can be applied. As a step in this direction, this paper presents a design space that identifies different aspects of using EMS for haptic feedback. The design space is meant as a basis for future research investigating how particular characteristics can be exploited to provide specific haptic feedback.

This paper introduces an approach for the use of direct and indirect communication between robots for a robust communication framework in a multi-agent scenario. This approach is granting the robots access to a defined minimum of information via indirect communication that is needed to fulfill the needs of the underlying navigation or exploration algorithm and creating a robust mechanism that does not suffer the drawbacks of direct communication via radio signals or light waves. It also allows the agents to access a higher level of communication via creating an ad hoc network for the exchange of additional information which would enhance the communication and cooperation between the agents. This will enable the underlying algorithm to access added information which can be used to significantly boost the navigation or exploration process, while not relying on this high level of communication.

Distributed discrete event simulation is a very important method today to analyze the behavior of large models. We investigate the practical implementation of distributed discrete event simulation with conservative synchronization and its acceleration through dynamic estimation of process-to-process look-ahead. Since the dynamic look-ahead changes with time, we have to face the situation, that the look-ahead between some logical processes is decreased temporarily. The shortened lookahead has a very negative influence to the performance of the simulation and it is hard to avoid. However, this effect can be reduced by introducing some extra mechanisms in the simulation. In this paper, we present a mechanism to optimize the simulation for the situation that the look-ahead between some processes is very short. This mechanism is based on exchange of conditional look-ahead and broadcast of invalidation announcement. Our evaluation shows reduction of the execution time of a majority of distributed simulations, especially when the estimated look-ahead is stochastically too conservative.

For many people their phones have become their main everyday tool. While phones can fulfill many different roles they also require users to (1) make do with affordance not specialized for the specific task, and (2) closely engage with the device itself. We propose utilizing the space and objects around the phone to offer better task affordance and to create an opportunity for casual interactions. Such around-device devices are a class of interactors that do not require users to bring special tangibles, but repurpose items already found in the user's surroundings. In a survey study, we determine which places and objects are available to around-device devices. Furthermore, in an elicitation study, we observe what objects users would use for ten interactions.

In the area of sports, athletes often resort to performance enhancing drugs to gain an advantage. Similarly, people use pharmaceutical drugs to aid learning, dexterity, or concentration. We investigate how pharmaceutical drugs could be used to enhance interactions. We envision that in the future, people might take pills along with their vitamins in the morning to improve how they can interact over the day. In addition to performance improvements this, e.g., could also include improvements in enjoyment or fatigue.

When interacting casually, users relinquish some control over their interaction to gain the freedom to devote their engagement elsewhere. This allows them to still interact even when they are encumbered, distracted, or engaging with others. With their focus on something else, casual interaction will often take place in the periphery---either spatially by, e.g., interacting laterally or with respect to attention, by interacting in the background.

The thumb and the fingers have different flexibility, and thus, gestures performed on the back of a held tablet are suggested to be different from ones performed on the touchscreen with the thumb of grasping hands. APIs for back-of-device gesture detection should consider that difference. In a user study, we recorded vectors for the four most common touch gestures. We found that drag, swipe, and press gestures are significantly differently when executed on the back versus on the front side of a held tablet. Corresponding values are provided that may be used to define gesture detection thresholds for back-of-tablet interaction.

We present imaginary reality basketball, i.e., a ball game that mimics the respective real world sport, i.e., basketball, except that there is no visible ball. The ball is virtual and players learn about its position only from watching each other act and a small amount of occasional auditory feedback, e.g., when a person is receiving the ball. Imaginary reality games maintain many of the properties of physical sports, such as unencumbered play, physical exertion, and immediate social interaction between players. At the same time, they allow introducing game elements from video games, such as power-ups, non-realistic physics, and player balancing. Most importantly, they create a new game dynamic around the notion of the invisible ball.

Free-hand interaction with large displays is getting more common, for example in public settings and exertion games. Adding haptic feedback offers the potential for more realis- tic and immersive experiences. While vibrotactile feedback is well known, electrical muscle stimulation (EMS) has not yet been explored in free-hand interaction with large displays. EMS offers a wide range of different strengths and qualities of haptic feedback. In this paper we first systematically inves- tigate the design space for haptic feedback. Second, we ex- perimentally explore differences between strengths of EMS and vibrotactile feedback. Third, based on the results, we evaluate EMS and vibrotactile feedback with regard to differ- ent virtual objects (soft, hard) and interaction with different gestures (touch, grasp, punch) in front of a large display. The results provide a basis for the design of haptic feedback that is appropriate for the given type of interaction and the material.

Planning in a multi-site, non-mass production environment is a special challenge because of several sources of uncertainty. Unlike in mass production facilities, in our setting the current state at all sites cannot be determined easily and exactly due to the spatial distribution of sites and the low degree of automation. For re-planning in case of failures, the possible alternative actions have to be formalized on the decision making facility, where the possible alternatives will then be determined and evaluated. In this work, we will present the necessary components for an automated evaluation of alternatives and decision support procedure. The main challenges are the formalization of product plans including alternative steps and the non-automated collection or assessment of the distributed system state of all sites.

Modern mobile devices typically rely on touchscreen keyboards for input. Unfortunately, users often struggle to enter text accurately on virtual keyboards. To address this, we present a novel decoder for touchscreen text entry that combines probabilistic touch models with a long-span language model. We investigate two touch models – one based on Gaussian Processes that implicitly models the inherent uncertainty of the touching process and a second that allows users to explicitly control the uncertainity via touch pressure. Using the first model we show that character error rate can be reduced by up to 7% over a baseline, and by up to 1.3% over a leading commercial keyboard. With the second model, we demonstrate that providing users with control over input certainty results in improved text entry rates for phrases containing out of vocabulary words.

Parkinson's disease causes a wide range of motor impairments that also affect speech. Even patients with mild speech motor disabilities do suffer from symptoms such as reduced dynamics, melody, tone, pace and continuity of speech. Besides invasive or drug based treatments, effective logopedic treatments do exist. However, constant training is a key factor for this type of therapy. Digital games can be one way to enhance patient's motivation for repetitive exercises both in therapy sessions and in prolonged use at home. This paper examines the possibilities of such a digital logopedic game developed for PD patients and reports first promising study results that indicate an increased peak voice loudness of the players' voice when playing the game.

In this paper we will introduce a new multi-agent algorithm for the use in search and rescue scenarios for exploration of unknown terrain. This method combines the concept of exploration from the flood algorithm and the path optimizing features of the ant algorithm. The first part leads to a fast exploration of the unknown terrain, while the second part constructs short paths from points of interest back to the base. Together this enables the starting of rescue operations parallel to the ongoing search. We demonstrate the feasibility of our approach by agent-based simulations. The simulations show, that our approach is comparable in speed and quality with already existing algorithms, delivering the additional benefit of short paths to points of interest, and adhering to the inherent limitations of these kind of scenarios.

Fault-tolerant networks are needed for many applications, such as telecommunication networks, electricity networks, traffic, routing, and others. Several methods for constructing fault-tolerant networks out of a given set of nodes exists, among them classical graph-theoretic ones, and recently also several bio-inspired algorithms have been proposed for such application. In this paper we study the performance of these different algorithms for that problem. Performance means that both the complexity of the algorithm for a given problem size and the quality of the generated networks are taken into account. We conclude that classical algorithms that belong to a certain complexity class are efficient for small to medium size problems, while at some point, for larger problems, bio-inspired solutions are more efficient to get a solution.

Motivated by the addition of gyroscopes to a large number of new smart phones, we study the effects of combining accelerometer and gyroscope data on the recognition rate of motion gesture recognizers with dimensionality constraints. Using a large data set of motion gestures we analyze results for the following algorithms: Protractor3D, Dynamic Time Warping (DTW) and Regularized Logistic Regression (LR). We chose to study these algorithms because they are relatively easy to implement, thus well suited for rapid prototyping or early deployment during prototyping stages. For use in our analysis, we contribute a method to extend Protractor3D to work with the 6D data obtained by combining accelerometer and gyroscope data. Our results show that combining accelerometer and gyroscope data is beneficial also for algorithms with dimensionality constraints and improves the gesture recognition rate on our data set by up to 4\%.

A recurrent challenge for human computation is motivation. Motivation is not only a prevailing topic for crowd based human computation it is also multifarious. Contributors support human computation projects for money, fun, and many other reasons. Probably the most appealing motivation from a requester’s perspective is an intrinsic interest in the task itself, although this is a rare situation. Therefore, when designing a human computation system a key challenge to accept and handle is to offer a valuable reward for contributors. One possible approach to this challenge is to design human computation systems in a way that makes their use an inherently pleasurable experience. A powerful concept to make tasks more pleasurable is to use game design to add playful elements to the task or merge the task completely into a digital game. This chapter describes concepts, methods, and pitfalls of this approach. It will give hints to identify suitable tasks, design an overall strategy, and deal with the evaluation of data in playful human computation systems.

We describe the focused–casual continuum, a framework for describing interaction techniques according to the degree to which they allow users to adapt how much attention and effort they choose to invest in an interaction conditioned on their current situation. Casual interactions are particularly appropriate in scenarios where full engagement with devices is frowned upon socially, is unsafe, physically challenging or too mentally taxing. Novel sensing approaches which go beyond direct touch enable wider use of casual interactions, which will often be ‘around device’ interactions. We consider the degree to which previous commercial products and research prototypes can be considered as fitting the focused– casual framework, and describe the properties using control theoretic concepts. In an experimental study we observe that users naturally apply more precise and more highly engaged interaction techniques when faced with a more challenging task and use more relaxed gestures in easier tasks.

We present imaginary reality games, i.e., games that mimic the respective real world sport, such as basketball or soccer, except that there is no visible ball. The ball is virtual and players learn about its position only from watching each other act and a small amount of occasional auditory feedback, e.g., when a person is receiving the ball. Imaginary reality games maintain many of the properties of physical sports, such as unencumbered play, physical exertion, and immediate social interaction between players. At the same time, they allow introducing game elements from video games, such as power-ups, non-realistic physics, and player balancing. Most importantly, they create a new game dynamic around the notion of the invisible ball. To allow players to successfully interact with the invisible ball, we have created a physics engine that evaluates all plausible ball trajectories in parallel, allowing the game engine to select the trajectory that leads to the most enjoyable game play while still favoring skillful play.

In recent years crowd-based and human computation systems have attracted increasing attention in science and industry. For applications that are driven by input from a multitude of human raters, ensuring data reliability and organizing an interactive workflow constitute a new challenge. In this paper we describe a novel approach to ensure data quality in crowd-based and human computation systems. The proposed algorithm features the potential for direct feedback and interactivity while producing little computational overhead.

With the advent of mobile games and the according growing and competitive market, game user research can provide valuable insights and a competitive edge if methods and procedures are employed that match the distinct challenges that mobile devices, games and usage scenarios induce. We present a summary of parameters that frame the research setup and procedure, focusing on the trade-offs between lab and field studies and the related decision whether to pursue large-scale and quantitative or small-scale focused research accompanied by qualitative methods. We then illustrate the implications of these considerations on real world projects along the lines of two evaluations of different input methods for the action-puzzle mobile game Somyeol: a local study with 37 participants and a mixed design of qualitative and quantitative methods, and the strictly quantitative analysis of game-play data from 117,118 users. The findings underline the importance of small-scale evaluations prior to release.

One major problem of distributed discrete event simulation is the poor performance due to the huge overhead for maintaining the order of causality, so that the execution time cannot be reduced significantly compared to sequential simulation. This holds especially when the processes are tightly coupled and the look-ahead is very short. On the other hand, results of many simulations are obtained from a number of independent outputs, which are of stochastic nature and a small deviation of a limited amount of outputs is acceptable. Acceptance of such deviations in a controlled way could affect a trade-off between the simulation accuracy and the execution time. The goal of our investigation is to develop a methodology to handle the trade-off. In this paper, we propose a new way of distributed simulation with semi-conservative look-ahead estimation, where we accept causality errors to a certain and limited extent. In our approach, we consider a semi-conservative estimation allowing limited over-estimation. If the look-ahead is over-estimated, unsolved causality errors will be resolved by a very efficient recovery procedure at the expense of simulation errors. Results from a case study demonstrate that our approach is able to maximize the look-ahead with respect to the predefined error bounds and can reduce the execution time of many simulations. We do however also point out the limitations of the mechanism and the trend of our further investigation.

Planning in a multi-site, non-mass production environment is a special challenge because of several sources of uncertainty. Unlike in mass production facilities, in our setting the current state is not easily and exactly known when the case of re-planning occurs. The planning procedure has to contribute to that fact, as well as to further uncertainties concerning the effects of a plan when evaluating the plan. Thus in this work, we apply online simulation as means for re-planning multi-site production in the case of resource failure. This work is a first step where two alternatives are considered when a resource fails: either wait for repair of the resource, or transport another instance of this resource from another site, if there is more than one available. Our study shows that the planning using online simulation is superior to a static strategy such as `always wait for repair' or `always import resource' in case of resource failure.

As displays in public space are augmented with sensors, such as the Kinect, they enable passersby to interact with the content on the screen. As of today, feedback on the user action in such environments is usually limited to the visual channel. However, we believe that more immediate and intense forms, in particular haptic feedback, do not only increase the user experience, but may also have a strong impact on user attention and memorization of the content encountered during the interaction. Haptic feedback can today be achieved through vibration on the mobile phone, which is strongly dependent on the location of the device. We envision that fabrics, such as underwear, can in the future be equipped with electrical muscle stimulation, thus providing a more natural and direct way of haptic feedback. In this demo we aim to showcase the potential of applying electrical muscle stimulation as direct haptic feedback during interaction in public spaces in the context of a Kinect-based game for public displays.

We present a wearable interface that consists of motion sensors. As the interface can be worn on the user's fingers (as a ring) or fixed to it (with nail polish), the device controlled by finger gestures can be any generic object, provided they have an interface for receiving the sensor's signal. We implemented four gestures: tap, release, swipe, and pitch, all of which can be executed with a finger of the hand holding the device. In a user study we tested gesture appropriateness for the index finger at the back of a handheld tablet that offered three different form factors on its rear: flat, convex, and concave (undercut). For all three shapes, the gesture performance was equally good, however pitch performed better on all surfaces than swipe. The proposed interface is an example towards the idea of ubiquitous computing and the vision of seamless interactions with grasped objects. As an initial application scenario we implemented a camera control that allows the brightness to be configured using our tested gestures on a common SLR device.

This work evaluates and improves agent-based approaches for exploration of unknown terrain and finding (shortest) paths to a goal with an unknown location. This scenario is typically found in emergency incidents and for technically assisted search and rescue cases, e.g. when a building or a block of a city has been damaged by an earthquake and as a result, former maps are not valid anymore. In our approach we simulate the exploration of the unknown environment by agents that have different capabilities typically found in the technical assistance systems used in search and rescue operations, such as cameras, sensors, and limited communication abilities. The outcome of our simulation experiments indicates, which composition of a population of agents is best suited for efficient exploration of the unknown terrain, in terms of speed and path length. The results give hints which agent populations should be tried in a real world setting, in a search and rescue test scenario with real robots and sensors.

Mobile handheld projectors in small form factors, e.g., integrated into mobile phones, are getting more common. However, managing the projection puts a burden on the user as it requires holding the hand steady over an extended period of time and draws attention away from the actual task to solve. To address this problem, we propose a body worn projector that follows the user's locus of attention. The idea is to take the user's hand and dominant ngers as an indication of the current locus of attention and focus the projection on that area. Technically, a wearable and steerable camera-projector system positioned above the shoulder tracks the ngers and follows their movement. In this paper, we justify our approach and explore further ideas on how to apply steerable projection for wearable interfaces. Additionally, we describe a Kinect-based prototype of the wearable and steerable projector system we developed.

Recently several approaches have been presented that exploit the ability of Physarum polycephalum to connect several food sources via a network of pipes in order to maintain an efficient food distribution inside the organism. These approaches use the mechanisms found in nature in order to solve a technical problem, namely the design of constructing faulttolerant and efficient connection networks. These works comprise experiments with a real slime mold Physarum polycephalum as well as computer simulations based on a tubular model and an agent-based approach. In this work, we study the suitability of those bio-inspired approaches and compare their performance to a graph-theoretic algorithm for construction of fault-tolerant connection networks, the (k, t)-spanner algorithm. The graphtheoretic algorithm is able to construct graphs with a certain degree of fault tolerance as well as meet a given maximal path length between two arbitrary nodes. However the definition of fault tolerance in previous bio-inspired works differs to that used in graph theory. Thus in our contribution we analyze the bio-inspired approaches as well as the graph-theoretic approach for their efficiency of designing optimal fault-tolerant graphs. We demonstrate the usability of the graph-theoretic approach despite relying on a different definition of fault tolerance. We conclude that classical efficient computational algorithms from graph theory can be adapted and applied in the same field as the bio-inspired approaches for the problem of constructing efficient fault tolerant networks. They often provide an easier to use and more direct solution than bio-inspired approaches, that need more parameter tuning before getting satisfactory results.

Designing digital games is primarily interaction design. This interaction manifests as a meaningful change in the game world. An aspect of a game can only change dynamically with a parametric model of this aspect available. One aspect of digital games is yet missing such a systematic description: the genre of a game is currently only determined by its designer. This paper introduces a new approach that allows for dynamic blending between genres. We describe a set of game mechanics that express the characteristics of different game genres. We extract a parametric model from these mechanics to allow dynamic blending. The paper illustrates the possibilities of this approach with an implementation of a multi-genre-game. It also provides empiric evidence that the described model successfully generates different game genres.

Exergames offer exciting perspectives not only for recreational, but also for therapeutic use. Increasing numbers of older adults in many industrialized countries raise the need for affordable and reliable solutions to help people to stay healthy and fit at advanced ages. While games user research is vital to increasing the quality of game designs and improving game design processes, many research tools are difficult to use with senior gamers, and the target group is especially vulnerable to mistakes both in game design and games user research. We report and classify some of these challenges along with possible approaches, aiming to fuel intensified exchange about methodological experiences among researchers in the field.

Mobile devices are already an important platform for digital games. These devices need specialized input metaphors as they have various restrictions such as their own hardware capabilities and the lack of external input devices. Especially challenging are fast paced interactions as in Jump and Run games. This paper explores three user inputs for Jump and Run games on mobile devices along the game Somyeol.

With recent advances in harnessing the knowledge and skill of large groups of (unknown) network-connected humans, researchers and practitioners have been designing systems that make contributions of users entertaining and more engaging. Game mechanics are being applied to the traditional human computation tasks, such as transcription, classification and labeling. Seminal examples of such applications include ESP game and FoldIt. At the same time, companies seek strategies to include elements of gaming into business processes to increase productivity and engagement of employees. Framing a business goal in the form of a game is also a promising method for motivating newer generations in the workforce.

The scientific study of serious games is a recent development, spanning less than two decades. One aspect in this field is human computation with digital games. The core of the paradigm is to outsource problems that are not yet solvable by conventional computational systems to humans. Therefore, these problems are reformulated into tasks that are then integrated into digital games. The players of the game then solve the problem while playing. Different human computation games have been successfully deployed, but tend to provide a relatively narrow gaming experience. This chapter analyzes the differences between game design for human computation and traditional digital game design. An in-depth consideration of these differences shows that it is a viable approach to build human computation games with a wide range of designs. The key issues of human computation game design are illustrated with the game OnToGalaxy.

We investigate the capability of ad-hoc sensor networks equipped with simple sensor devices to enable a more accurate spatial event localization in order to support smart camera networks. We present a novel algorithm named Orthogonal Cut which is suitable for many different event detection scenarios, especially when large interferences occur. It estimates the spatial position of a detected event by dividing the surveillance space of a sensor network into smaller areas until a threshold criteria is met.

Rotating 3D objects is a diffcult task on mobile devices, because the task requires 3 degrees of freedom and (multi-)touch input only allows for an indirect mapping. We propose a novel style of mobile interaction based on mid-air gestures in proximity of the device to increase the number of DOFs and alleviate the limitations of touch interaction with mobile devices. While one hand holds the device, the other hand performs mid-air gestures in proximity of the device to control 3D objects on the mobile device's screen. A at hand pose de nes a virtual surface which we refer to as the PalmSpace for precise and intuitive 3D rotations. We constructed several hardware prototypes to test our interface and to simulate possible future mobile devices equipped with depth cameras. Pilot tests show that PalmSpace hand gestures are feasible. We conducted a user study to compare 3D rotation tasks using the most promising two designs for the hand location during interaction - behind and beside the device - with the virtual trackball, which is the current state-of-art technique for orientation manipulation on touchscreens. Our results show that both variants of PalmSpace have signi cantly lower task completion times in comparison to the virtual trackball.

A major challenge of human subject research lies in motivating enough subjects to participate in studies. Traditionally, participants are extrinsically motivated, for example by getting paid for their contribution. Together with the effort of organizing and supervising experiments, this renders human subject research either very expensive, or reduces the validity due to small sample sizes. This work describes the method of utilizing playful web-based surveys to intrinsically motivate contributors to participate in studies and illustrates the approach with two examples: a study of the effect of retouching portraits on the perception of human faces and according estimates of wealth and success that was distributed via a single announcement on a social network and attracted more than 2400 participants within a five months period, as well as a study on the perception of a questionnaire in the form of a playful survey as compared to a more traditional online questionnaire, which showed that participants are more likely to recommend playful surveys to friends than normal surveys.

Research over the past years has shown that machine translation results can be greatly enhanced with the help of mono-or bilingual human contributors, eg by asking humans to proofread or correct outputs of machine translation systems. However, it remains difficult to determine the quality of individual revisions. This paper proposes a method to determine the quality of individual contributions by analyzing task-independent data. Examples of such data are completion time, number of keystrokes, etc. An initial evaluation showed promising F-measure values larger than 0.8 for support vector machine and decision tree based classifications of a combined test set of Vietnamese and German translations.

We present Quantum games, physical games that resemble corresponding real–world sports—except that the ball exists only in the players’ imagination. We demonstrate Quantum versions of team handball and air hockey. A computer system keeps score by tracking players using a Microsoft Kinect (air hockey) or a webcam (handball), simulates the physics of the ball, and reports ball interactions and scores back using auditory feedback. The key element that makes Quantum games playable is a novel type of physics engine that evaluates not one, but samples the set of all plausible ball trajectories in parallel. Before choosing a trajectory to realize, the engine massively increases the probability of outcomes that lead to enjoyable gameplay, such as goal shots, but also successful passes and intercepts that lead to fluid gameflow. The same mechanism allows giving a boost to inexpe- rienced players and implementing power–ups.

When the user is engaged with a real-world task it can be inappropriate or difficult to use a smartphone. To address this concern, we developed ShoeSense, a wearable system consisting in part of a shoe-mounted depth sensor pointing upward at the wearer. ShoeSense recognizes relaxed and discreet as well as large and demonstrative hand gestures. In particular, we designed three gesture sets (Triangle, Radial, and Finger-Count) for this setup, which can be performed without visual attention. The advantages of ShoeSense are illustrated in five scenarios: (1) quickly performing frequent operations without reaching for the phone, (2) discreetly performing operations without disturbing others, (3) enhancing operations on mobile devices, (4) supporting accessibility, and (5) artistic performances. We present a proof-of-concept, wearable implementation based on a depth camera and report on a lab study comparing social acceptability, physical and mental demand, and user preference. A second study demonstrates a 94-99% recognition rate of our recognizers.

Graspable tangibles are now being explored on the current generation of capacitive touch surfaces, such as the iPad and the Android tablet. Because the size and form factor is relatively new, early and low fidelity prototyping of these TUIs is crucial in getting the right design. The problem is that it is difficult for the average interaction designer to develop such physical prototypes. They require a substantial amount time and effort to physically model the tangibles, and expertise in electronics to instrument them. Thus prototyping is sometimes handed off to specialists, or is limited to only a few design iterations and alternative designs. Our solution contributes a low fidelity prototyping approach that is time and cost effective, and that requires no electronics knowledge. First, we supply non-specialists with cardboard forms to create tangibles. Second, we have them draw lines on it via conductive ink, which makes their objects recognizable by the capacitive touch screen. They can then apply routine programming to recognize these tangibles and thus iterate over various designs.

In this work we use a simulation model of the slime mold Dictyostelium discoideum to study mechanisms of evolutional selection. Dictyostelium discoideum shows “altruistic” behavior: some cells sacrifice themselves in order to enable the survival of other cells. This behavior contradicts the individual selection on a “survival of the fittest” basis, which is used in many computational algorithms. We will show that individuals with lower fitness will not die out; on the contrary, they might be necessary for the survival of a population. As a conclusion, we should rethink the practice of selecting the best individuals on the basis of one single measure in computational algorithms using a selection scheme.

This paper explores how microinteractions such as hand gestures allow executing a secondary task, e.g. controlling mobile applications and devices, without interrupting the manual primary tasks, for instance driving a car. We asked sports- and physiotherapists for using props while interviewing these experts in order to iteratively design microgestures. The required gestures should be easily performable without interrupting the primary task, without needing high cognitive effort, and without taking the risk of being mixed up with natural movements. Resulting from the expert interviews we developed a taxonomy for classifying these gestures according to their use cases and assess their ergonomic and cognitive attributes, focusing on their primary task compatibility. We defined 21 hand gestures, which allow microinteractions within manual dual task scenarios. In expert interviews we evaluated their level of required motor or cognitive resources under the constraint of stable primary task performance. Our taxonomy poses a basis for designing microinteraction techniques.

Interactive surfaces are only just beginning to break into the market, and they still do not offer the advanced functionality demonstrated with many lab prototypes. The path from a prototype system to a finished product for use in real-world scenarios is a long one, and many obstacles must be overcome. The design of an interactive multitouch table had to address issues like optical recognition, hardware design, and ergonomics. This paper describes in detail the construction of a large, robust multi-touch table called mrT. It will show how to solve major problems of the diffuse illumination technique and other challenges of constructing a large-screen, high-resolution, self-contained interactivemultitouch surface that not only serves as a development system but can be deployed in the real-world. Additionally, to further motivate some of the design decisions, especially why the diffuse illumination technology was chosen, this paper will discuss related on-going research projects on the application side.

We present CapWidgets, passive tangible controls for capacitive touch screens. CapWidgets bring back physical controls to off-the-shelf multi-touch surfaces as found in mobile phones and tablet computers. While the user touches the widget, the surface detects the capacitive marker on the widget's underside. We study the relative performance of this tangible interaction with direct multi-touch interaction and our experimental results show that user performance and preferences are not automatically in favor of tangible widgets and careful design is necessary to validate their properties.

In this work we evaluate slime mold inspired algorithms, that gained a lot of attention in renowned journals recently, for their ability to construct fault tolerant connection networks. In previous work, experiments with a real slime mold Physarum polycephalum as well as computer simulations based on a tube model of the slime mold showed, that the slime mold (and simulations thereof) is able to construct fault tolerant and efficient transport networks similar to the actual Tokyo rail system. However the quality of the solutions of the real slime mold show big variations, and the tubular computer simulation does not seem to reproduce the natural slime mold very well, since the constructed networks do not show the variety of the naturally build ones, instead they show a heavy dependence of one simulation parameter. Thus in our work we present a different approach for construction of fault tolerant connection networks for the Tokyo rail system using an agent based simulation of Physarum polycephalum. Analysis of the results show that the agent based simulation reproduces the variance in the behavior of the natural slime mold much better. Analyzing the cost benefit ratio of bio-inspired network construction we however conclude that it might be worth to consider classical efficient computational algorithms for the problem of constructing minimal fault tolerant networks.

The information a small mobile device can show via its display has been always limited by its size. In large information spaces, relevant information, such as important locations on a map can get clipped when a user starts zooming and panning. Dynamic ambient lighting allows mobile devices to visualize off-screen objects by illuminating the background without compromising valuable display space. The lighted spots can be used to show the direction and distance of such objects by varying the spot's position and intensity. Dynamic ambient lighting also provides a new way of displaying the state of a mobile device. Illumination is provided by a prototype rear of device shell which contains LEDs and requires the device to be placed on a surface, such as a table or desk.

Cars offer an increasing number of infotainment systems as well as comfort functions that can be controlled by the driver. In our research, we investigate new interaction techniques that aim to make it easier to interact with these systems while driving. We suggest utilizing the steering wheel as an additional interaction surface. In this paper, we present two user studies conducted with a working prototype of a multi-touch steering wheel. In the first, we developed a user-defined steering wheel gesture set, and in the second, we applied the identified gestures and compared their application to conventional user interaction with infotainment systems in terms of driver distraction. The main outcome was that driver's visual demand is reduced significantly by using gestural interaction on the multi-touch steering wheel.

Motivation has been one of the central challenges of human computation. A promising approach is the integration of human computation tasks into digital games. Different human computation games have been successfully deployed, but tend to provide relatively narrow gaming experiences. This survey discusses various approaches of digital games for human computation and aims to explore the ties to signal processing and possible generalizations.

Rohs and Oulasvirta (2008) proposed a two-component Fitts' law model for target acquisition with magic lenses in mobile augmented reality (AR) with 1) a physical pointing phase, in which the target can be directly observed on the background surface, and 2) a virtual pointing phase, in which the target can only be observed through the device display. The model provides a good fit (R2=0.88) with laboratory data, but it is not known if it generalizes to real-world AR tasks. In the present outdoor study, subjects (N=12) did building-selection tasks in an urban area. The differences in task characteristics to the laboratory study are drastic: targets are three-dimensional and they vary in shape, size, z-distance, and visual context. Nevertheless, the model yielded an R2 of 0.80, and when using effective target width an R2 of 0.88 was achieved.

Games for rehabilitation are developing rapidly in recent years. It has been shown that utilization of therapy and gaming technology affects positively on the patients’ physical and mental condition. However, to this day there are only few playable games for Parkinson’s disease patients. This paper presents the development process of WuppDi! – a collection of five motion-based games for Parkinson’s disease patients, aimed at supporting their exercises routines in various playful environments. We describe the game design challenges for Parkinson’s disease patients and our solutions used in the games. Finally, we present the results of a conducted field test showing a very positive motivational effect among the majority of the patients but also highlighting remaining issues and technical difficulties, which can be beneficial for the future development in this field.

Protractor 3D is a gesture recognizer that extends the 2D touch screen gesture recognizer Protractor to 3D gestures. It inherits many of Protractor's desirable properties, such as high recognition rate, low computational and low memory requirements, ease of implementation, ease of customization, and low number of required training samples. Protractor 3D is based on a closed-form solution to finding the optimal rotation angle between two gesture traces involving quaternions. It uses a nearest neighbor approach to classify input gestures. It is thus well-suited for application in resource-constrained mobile devices. We present the design of the algorithm and a study that evaluated its performance.

Even with the rise of the World Wide Web, TV has remained the most pervasive entertainment medium and is nowadays often used together with other media, which allow for active participation. The idea of connecting non-collocated TV viewers via telecommunication technologies, referred to as Social TV, has recently received considerable attention. Such systems typically include set-top boxes for supporting collaboration. In this research we investigate if real-time opinion sharing about TV shows through a nonverbal (non-textual) iconic UI on mobile phones is reasonable. For this purpose we developed a mobile app, made it available to a large number of users through the Android Market, and conducted an uncontrolled user study in the wild during the soccer world cup 2010. The results of the study indicate that TV viewers who used the app had more fun and felt more connected to other viewers. We also show that by monitoring this channel it is possible to collect sentiments relevant to the broadcasted content in real-time. The collected data exemplify that the aggregated sentiments correspond to important moments, and hence can be used to generate a summary of the event.

Conducting surveys is a costly and time-consuming process. We developed a playful questionnaire that addresses the issue of motivation for voluntary participation. In addition, distributing playful questionnaires on Facebook gives access to basic user data, which may allow employing some of them as quality control questions or simply help to lessen the number of questions.

Game development is a challenging and diverse field. It integrates different disciplines such as computer science, design, art, and psychology. Many different skills are required to create successful games, posing great challenges for education. These challenges also apply to the area of Serious Games with the additional difficulty of adding goals beside entertainment to the design. We report on our experiences with designing and implementing teaching formats to further the development of curricula and formal education in the area of Serious Game development. Our approach combines theoretical as well as practical elements. To reinforce and motivate our students we connect our courses to external events such as game development competitions. Furthermore, we experimented with using meta-games as a way of teaching game design.

Advances in sensing technology are currently bringing touch input to non-planar surfaces, ranging from spherical touch screens to prototypes the size and shape of a ping-pong ball. To help interface designers create usable interfaces on such devices, we determine how touch surface curvature affects targeting. We present a user study in which participants acquired targets on surfaces of different curvature and at locations of different slope. We find that surface convexity increases pointing accuracy, and in particular reduces the offset between the input point perceived by users and the input point sensed by the device. Concave surfaces, in contrast, are subject to larger error offsets. This is likely caused by how concave surfaces hug the user's finger, thus resulting in a larger contact area. The effect of slope on targeting, in contrast, is unexpected at first sight. Some targets located downhill from the user's perspective are subject to error offsets in the opposite direction from all others. This appears to be caused by participants acquiring these targets using a different finger posture that lets them monitor the position of their fingers more effectively.

Enterprise Architecture Management (EAM) plays an important supporting role in IT management of organizations to align their IT infrastructure to actual business needs. This emerging research paper presents an approach to enable real-time monitoring and controlling of enterprise architectures. Therefore, we adapted the “control center” concept as applied in power plants or railway control plants. The contribution of this paper presents an architecture for real-time monitoring and controlling facilities for complex business application landscapes. The business software control center is designed to give a real-time view of instances of IT-supported business processes together with the currently involved software systems and services. Moreover, IT operators are supported by controlling centers to actively control the load of software services at the business function level and to control the flow of business process instances through the organization’s IT infrastructure.

Mobile devices are increasingly used in social networking applications and research. So far, there is little work on real-time emotion or opinion sharing in large loosely coupled user communities. One potential area of application is the assessment of widely broadcasted television TV shows. The idea of connecting non-collocated TV viewers via telecommunication technologies is referred to as Social TV. Such systems typically include set-top boxes for supporting the collaboration. In this work the authors investigated whether mobile phones can be used as an additional channel for sharing opinions, emotional responses, and TV-related experiences in real-time. To gain insight into this area, an Android app was developed for giving real-time feedback during soccer games and to create ad hoc fan groups. This paper presents results on rating activity during games and discusses experiences with deploying this app over four weeks during soccer World Cup. In doing so, challenges and opportunities faced are highlighted and an outlook on future work in this area is given.

The Parkinson’s disease is a neurodegenerative disorder with a range of symptoms such as slowness, rigidity, resting tremor (trembling), and an impairment of postural balance leading to disturbance of gait and falling. Continuous exercises are an effective strategy to maintain the patient’s movement abilities, slowing down the progression of the disease. Self-directed exercises in addition to supervised physiotherapy sessions are not only beneficial, but necessary. This paper presents an approach to support Parkinson’s disease patients in their daily exercises using the playful context of different motionbased digital games adapted from physiotherapy.

We present the $3 Gesture Recognizer, a simple but robust gesture recognition system for input devices featuring 3D acceleration sensors. The algorithm is designed to be implemented quickly in prototyping environments, is intended to be device-independent and does not require any special toolkits or frameworks. It relies solely on simple trigonometric and geometric calculations. A user evaluation of our system resulted in a correct gesture recognition rate of 80%, when using a set of 10 unique gestures for classification. Our method requires significantly less training data than other gesture recognizers and is thus suited to be deployed and to deliver results rapidly.

Symbiotic simulation in industrial applications requires efficient connectivity between industrial processes and embedded legacy simulators. One main challenge is to handle heterogeneous system parameters like bandwidth, latency, redundancy, security and data representation. Moreover, data management needs to be improved in terms of unified access providing an interface to online, historical and corresponding simulation data. This paper proposes a framework for symbiotic simulation addressing the problem of connectivity. We introduce the Process Data Streaming Protocol (PDSP) managing distributed process data flows. Additionally we present PDSP based modules covering different modes of operation for data processing. The Framework interacts with distributed control systems via object linking and embedding for process control as well as to embedded systems using different hierarchic operation modes. Historical data can be provided transparently through an integrated stream-database. The framework is primarily optimized to be used in JAVA-based simulation environments, but is not limited to these. Finally we demonstrate the usability of the system while interacting with a simulation environment for a hybrid process and present some experimental results.

We present a tabletop-based system that supports rapid paper-based prototyping for mobile applications. Our system combines the possibility of manually sketching interface screens on paper with the ability to define dynamic interface behavior through actions on the tabletop. This not only allows designers to digitize interface sketches for paper prototypes, but also enables the generation of prototype applications able to run on target devices. By making physical and virtual interface sketches interchangeable, our system greatly enhances and speeds up the development of mobile applications early in the interface design process.

Cars offer an increasing number of infotainment systems as well as comfort functions that can be controlled by the driver. With our research we investigate new interaction techniques that aim to make it easier to interact with these systems while driving. In contrast to the standard approach of combining all functions into hierarchical menus controlled by a multifunctional controller or a touch screen we suggest to utilize the space on the steering wheel as additional interaction surface. In this paper we show the design challenges that arise for multi-touch interaction on a steering wheel. In particular we investigate how to deal with input and output while driving and hence rotating the wheel. We describe the details of a functional prototype of a multi-touch steering wheel that is based on FTIR and a projector, which was built to explore experimentally the user experience created. In an initial study with 12 participants we show that the approach has a general utility and that people can use gestures for controlling applications intuitively but have difficulties to imagine gestures to select applications.

Slime molds are fascinating organisms, they can either live as an organism consisting out of a single cell (protozoa) or they can form a multi-cellular organism (pseudoplasmodium). So from the biological point of view, the slime molds are studied in order to understand the evolutionary step from a single cell organism to a multi-cellular organism. Studies have shown that the behavior of cooperating single cell organisms exhibit synergistic emergent intelligence, for example finding shortest paths. Just recently, simulation and experiments with a real slime mold (Physarum polycephalum) have been used for traveling salesman like problems. In this work we present a simulation model for the slime mold Dictyostelium discoideum. Different to other studies, here the whole life-cycle is modeled and simulated. This model is used to study the mechanism of cooperation of single cells: We compare the mechanism of altruistic group selection against individual and egoistic selection. It turns out that simple signaling mechanisms are sufficient for a complex behavior of Dictyostelium discoideum, that allows altruistic behavior on cell level, helping the whole population to survive.

Interactive surfaces are only just beginning to break into the market, and they still do not offer the advanced functionality demonstrated with many lab prototypes. The path from a prototype system to a finished product for use in real-world scenarios is a long one, and many obstacles must be overcome. The design of an interactive multitouch table had to address issues like optical recognition, hardware design, and ergonomics. This paper describes in detail the construction of a large, robust multi-touch table called mrT. It will show how to solve major problems of the diffuse illumination technique and other challenges of constructing a large-screen, high-resolution, self-contained interactive multitouch surface that not only serves as a development system but can be deployed in the real-world. Additionally, to further motivate some of the design decisions, especially why the diffuse illumination technology was chosen, this paper will discuss related on-going research projects on the application side.

We conducted a series of user studies to understand and clarify the fundamental characteristics of pressure in user interfaces for mobile devices. We seek to provide insight to clarify a longstanding discussion on mapping functions for pressure input. Previous literature is conflicted about the correct transfer function to optimize user performance. Our study results suggest that the discrepancy can be explained by different signal conditioning circuitry and with improved signal conditioning the user-performed precision relationship is linear. We also explore the effects of hand pose when applying pressure to a mobile device from the front, the back, or simultaneously from both sides in a pinching movement. Our results indicate that grasping type input outperforms single-sided input and is competitive with pressure input against solid surfaces. Finally we provide an initial exploration of non-visual multimodal feedback, motivated by the desire for eyes-free use of mobile devices. The findings suggest that non-visual pressure input can be executed without degradation in selection time but suffers from accuracy problems.

In this paper we describe a method to detect patterns in dance movements. Such patterns can be used in the context of interactive dance systems to allow dancers to influence computational systems with their body movements. For the detection of motion patterns, dynamic time warping is used to compute the distance between two given movements. A custom threshold clustering algorithm is used for subsequent unsupervised classification of movements. For the evaluation of the presented method, a wearable sensor system was built. To quantify the accuracy of the classification, a custom label space mapping was designed to allow comparison of sequences with disparate label sets.

Interaction with 3D objects and scenes is becoming increasingly important on mobile devices. We explore 3D object rotation as a fundamental interaction task. We propose an extension of the virtual trackball metaphor, which is typically restricted to a half sphere and single-sided interaction, to actually use a full sphere. The extension is enabled by a hardware setup called the ¿iPhone Sandwich,¿ which allows for simultaneous front-and-back touch input. This setup makes the rear part of the virtual trackball accessible for direct interaction and thus achieves the realization of the virtual trackball metaphor to its full extent. We conducted a user study that shows that a back-of-device virtual trackball is as effective as a front-of-device virtual trackball and that both outperform an implementation of tilt-based input.

Each day millions of people play digital games with different motivations. These motivations rang from time beating to deep immersion into a narration or interacting with a community. To address all these different means, a range of game designs is necessary. Traditional human computation games cannot present all these aspects yet. This work will give a game centered view on game design for human computation. To demonstrate the value of this view it will present a fast-paced action game called OnTo-Galaxy along with two different human computation tasks.

User interfaces for mobile devices move away from mainly button- and menu-based interaction styles and towards more direct techniques, involving rich sensory input and output. The recently proposed concept of Natural User Interfaces (NUIs) provides a way to structure the discussion about these developments. We examine how two-sided and around-device interaction, gestural input, and shape- and weight-based output can be used to create NUIs for mobile devices. We discuss the applicability of NUI properties in the context of mobile interaction.

In this paper we present a novel interface for mobile map navigation based on Semi-Automatic Zooming (SAZ). SAZ gives the user the ability to manually control the zoom level of an SDAZ interface, while retaining the automatic zooming characteristics of that interface at times when the user is not explicitly controlling the zoom level. In a user study conducted using a realistic mobile map with a wide scale space, we compare SAZ with existing map interface techniques, multi-touch and Speed-Dependent Automatic Zooming (SDAZ). We extend a dynamic state-space model for Speed-Dependent Automatic Zooming (SDAZ) to accept 2D tilt input for scroll rate and zoom level control and implement a dynamically zoomable map view with access to high-resolution map material for use in our study. The study reveals that SAZ performs significantly better than SDAZ and that SAZ is comparable in performance and usability to a standard multi-touch map interface. Furthermore, the study shows that SAZ could serve as an alternative to multi-touch as input technique for mobile map interfaces.

Slime molds are fascinating organisms, they can either live as an organism consisting out of a single cell or they can form a multi-cellular organism. Therefore from the biological point of view, the slime molds are studied in order to understand the evolutionary step from a single cell organism to a multi-cellular organism. Studies have shown that the behavior of cooperating single cell organisms exhibits synergistic emergent intelligence, for example finding shortest paths. Just recently, simulation and experiments with a real slime mold (Physarum polycephalum) have been used for traveling salesman like problems. In this work we present a simulation model for the slime mold Dictyostelium discoideum. Different to other studies, here the whole life-cycle is modeled and simulated. Very detailed behavioral patterns and parameters are modeled and as result a simulation model is obtained, that shows a behavior very close to the living slime mold. This result is consolidated by extensive verification experiments. As consequence, this model can be used to further study the mechanism of cooperation of single cells, mechanisms of synergy and emergence, and additionally this model offers the possibility to develop more slime mold inspired algorithms.

Impact force is an important dimension for percussive musical instruments such as the piano. We explore three possible mechanisms how to get impact forces on mobile multi-touch devices: using built-in accelerometers, the pressure sensing capability of Android phones, and external force sensing resistors. We find that accelerometers are difficult to control for this purpose. Android's pressure sensing shows some promise, especially when combined with augmented playing technique. Force sensing resistors can offer good dynamic resolution but this technology is not currently offered in commodity devices and proper coupling of the sensor with the applied impact is difficult.

Gestures can offer an intuitive way to interact with a computer. In this paper, we investigate the question whether gesturing with a mobile phone can help to perform complex tasks involving two devices. We present results from a user study, where we asked participants to spontaneously produce gestures with their phone to trigger a set of different activities. We investigated three conditions (device configurations): phone-to-phone, phone-to-tabletop, and phone to public display. We report on the kinds of gestures we observed as well as on feedback from the participants, and provide an initial assessment of which sensors might facilitate gesture recognition in a phone. The results suggest that phone gestures have the potential to be easily understood by end users and that certain device configurations and activities may be well suited for gesture control.

We present a human computation online game for enabling users to contribute to the creation of a corpus of question-resource pairs for harvesting web-based question answering. Our idea was motivated by the popular 'jeopardy' quiz.

Mobile devices are increasingly used in social networking applications. So far, there is little work on real-time emotion and opinion sharing in large loosely-coupled user communities. We present an Android app for giving realtime feedback during soccer games and to create ad hoc fan groups. We discuss our experiences with deploying this app over four weeks during 2010 soccer world cup. We highlight challenges and opportunities we faced and give recommendations for future work in this area.

Passing around stacks of paper photographs while sitting around a table is one of the key social practices defining what is commonly referred to as the ‘Kodak Generation’. Due to the way digital photographs are stored and handled, this practice does not translate well to the ‘Flickr Generation’, where collocated photo sharing often involves the (wireless) transmission of a photo from one mobile device to another. In order to facilitate ‘cross-generation’ sharing without enforcing either practice, it is desirable to bridge this gap in a way that incorporates familiar aspects of both. In this paper, we discuss a novel interaction technique that addresses some of the constraints introduced by current communication technology, and that enables photo sharing in a way, which resembles the passing of stacks of paper photographs. This technique is based on dynamically generated spatial regions around mobile devices and has been evaluated through two user studies. The results we obtained indicate that our technique is easy to learn and as fast, or faster than, current technology such as transmitting photos between devices using Bluetooth. In addition, we found evidence of different sharing techniques influencing social practice around photo sharing. The use of our technique resulted in a more inclusive and group-oriented behavior in contrast to Bluetooth photo sharing, which resulted in a more fractured setting composed of sub-groups.

The present work and demonstration system aims at finding an efficient and cost-effective human computation method to expand the linguistic capabilities of interactive games that need it to respond appropriately to the language based input of their users. As a showcase scenario for the experiments conducted, we took interactive fiction applications and examined how the human computation game design and scoring approaches affects the quality of the data gathered. The ensuing analysis of the data confirms our initial hypothesis that game approaches can provide both the qualitative and quantitative data needed for the corresponding interactive games.

In this paper we explore the design space of around-device interaction (ADI). This approach seeks to expand the interaction possibilities of mobile and wearable devices beyond the confines of the physical device itself to include the space around it. This enables rich 3D input, comprising coarse movement-based gestures, as well as static position-based gestures. ADI can help to solve occlusion problems and scales down to very small devices. We present a novel around-device interaction interface that allows mobile devices to track coarse hand gestures performed above the device's screen. Our prototype uses infrared proximity sensors to track hand and finger positions in the device's proximity. We present an algorithm for detecting hand gestures and provide a rough overview of the design space of ADI-based interfaces.

We conducted a user study to investigate the effect of visual context in handheld augmented reality interfaces. A dynamic peephole interface (without visual context beyond the device display) was compared to a magic lens interface (with video see-through augmentation of external visual context). The task was to explore objects on a map and look for a specific attribute shown on the display. We tested different sizes of visual context as well as different numbers of items per area, i.e. different item densities. We found that visual context is most effective for sparse item distributions and the performance benefit decreases with increasing density. User performance in the magic lens case approaches the performance of the dynamic peephole case the more densely spaced the items are. In all conditions, subjective feedback indicates that participants generally prefer visual context over the lack thereof. The insights gained from this study are relevant for designers of mobile AR and dynamic peephole interfaces by suggesting when external visual context is most beneficial.

This article reports on two user studies investigating the effect of visual context in handheld augmented reality interfaces. A dynamic peephole interface (without visual context beyond the device display) was compared to a magic lens interface (with video see-through augmentation of external visual context). The task was to explore items on a map and look for a specific attribute. We tested different sizes of visual context as well as different numbers of items per area, i.e. different item densities. Hand motion patterns and eye movements were recorded. We found that visual context is most effective for sparsely distributed items and gets less helpful with increasing item density. User performance in the magic lens case is generally better than in the dynamic peephole case, but approaches the performance of the latter the more densely the items are spaced. In all conditions, subjective feedback indicates that participants generally prefer visual context over the lack thereof. The insights gained from this study are relevant for designers of mobile AR and dynamic peephole interfaces, involving spatially tracked personal displays or combined personal and public displays, by suggesting when to use visual context.

Efficient and effective communication between mobile units and the central emergency operation center is a key factor to respond successfully to the challenges of emergency management. Nowadays, the only ubiquitously available modality is a voice channel through mobile phones or radio transceivers. This makes it often very difficult to convey exact geographic locations and can lead to misconceptions with severe consequences, such as a fire brigade heading to the right street address in the wrong city. In this paper we describe a handheld augmented reality approach to support the communication of spatial information in a crisis response scenario. The approach combines mobile camera devices with paper maps to ensure a quick and reliable exchange of spatial information.

Mobile phones offer an attractive platform for interactive music performance. We provide a theoretical analysis of the sensor capabilities via a design space and show concrete examples of how different sensors can facilitate interactive performance on these devices. These sensors include cameras, microphones, accelerometers, magnetometers and multitouch screens. The interactivity through sensors in turn informs aspects of live performance as well as composition though persistence, scoring, and mapping to musical notes or abstract sounds.

With the miniaturization of projection technology the integration of tiny projection units, normally referred to as pico projectors, into mobile devices is not longer ction. Such integrated projectors in mobile devices could make mobile projection ubiquitous within the next few years. These phones soon will have the ability to project large-scale information onto any surfaces in the real world. By doing so the interaction space of the mobile device can be expanded to physical objects in the environment and this can support interaction concepts that are not even possible on modern desktop computers today. In this paper, we explore the possibilities of camera projector phones with a mobile adaption of the Playstation3 game LittleBigPlanet. The camera projector unit is used to augment the hand drawings of a user with an overlay displaying physical interaction of virtual objects with the real world. Players can sketch a 2D world on a sheet of paper or use an existing physical configuration of objects and let the physics engine simulate physical procedures in this world to achieve game goals.

The advantages of paper-based maps have been utilized in the field of mobile Augmented Reality (AR) in the last few years. Traditional paper-based maps provide high-resolution, large-scale information with zero power consumption. There are numerous implementations of magic lens interfaces that combine high-resolution paper maps with dynamic handheld displays. From an HCI perspective, the main challenge of magic lens interfaces is that users have to switch their attention between the magic lens and the information in the background. In this paper, we attempt to overcome this problem by using a lightweight mobile camera projector unit to augment the paper map directly with additional information. The "Map Torchlight" is tracked over a paper map and can precisely highlight points of interest, streets, and areas to give directions or other guidance for interacting with the map.

Adding security mechanisms to computer and communication systems without degrading their performance is a difficult task. This holds especially for wireless sensor networks, which due to their design are especially vulnerable to intrusion or attack. It is therefore important to find security mechanisms which deal with the limited resources of such systems in terms of energy consumption, computational capabilities and memory requirements. In this document we discuss and evaluate several learning algorithms according to their suitability for intrusion and attack detection. Learning algorithms subject to evaluation include bio-inspired approaches such as Artificial Immune Systems or Neural Networks, and classical such as Decision Trees, Bayes classifier, Support Vector Machines, k-Nearest Neighbors and others. We conclude that, in our setup, the more simplistic approaches such as Decision Trees or Bayes classifier offer a reasonable performance. The performance was, however, found to be significantly dependent on the feature representation.

Most of the performance assessment of semiconductor manufacturer is based on their self-appraisal or subjective judgments. The needs to measure fabrication (fab) operation performance along with its various dimensions have led to the development of a large number of quantitative performance indicators. An overall scheme to measure the performance of fab operation involving multi-input and multi-effects (output) has not been well established yet. In this study, we approach the performance assessment and prediction by combining clustering approaches with Artificial Neural Networks (ANN) approaches. We use historical data from a Taiwan semiconductor major player which comprise input/investment data (such as headcount, salary, cost for machines, running the fab,...) as well as output of each fab (such as margin, waferoutput rate, stepmove, number of patents). The data comprise several years, during which some of the fabs have been ramped up. In the first phase of our approach, we studied several clustering algorithms (K-Means, X-means, Kernel K-Means, SIB, and EM) on the data. We found several clusterings that were meaningful according to human experts. One of the clustering approaches clearly divided one older fab from newer fabs, and also was able to distinguish fabs in ramping up phase from fabs that are in stable operation phase. Other approaches formed clusters according to the grade of performance (bad, medium-bad, medium-good, good) of the data sets. Second, we use the classification to let a neural network learn the status of a fab, so that for a new fab, the status can be judged by the neural net. In a third step, we let a neural network learn the relationship between the multiple inputs and outputs. As result we found a neural net structure that is able to predict changes in the inputs of a fab on the different output factors. By this we enable the fab management to obtain a prediction, which effect a planned measure (eg increase or decrease of headcount) has on the output of the fab, that is the performance figures.

In many mid- to large-sized cities public maps are ubiquitous. One can also find a great number of maps in parks or near hiking trails. Public maps help to facilitate orientation and provide special information to not only tourists but also to locals who just want to look up an unfamiliar place while on the go. These maps offer many advantages compared to mobile maps from services like Google Maps Mobile or Nokia Maps. They often show local landmarks and sights that are not shown on standard digital maps. Often these 'You are here' (YAH) maps are adapted to a special use case, e.g. a zoo map or a hiking map of a certain area. Being designed for a fashioned purpose these maps are often aesthetically well designed and their usage is therefore more pleasant. In this paper we present a novel technique and application called PhotoMap that uses images of 'You are here' maps taken with a GPS-enhanced mobile camera phone as background maps for on-the-fly navigation tasks. We discuss different implementations of the main challenge, namely helping the user to properly georeference the taken image with sufficient accuracy to support pedestrian navigation tasks. We present a study that discusses the suitability of various public maps for this task and we evaluate if these georeferenced photos can be used for navigation on GPS-enabled devices.

Collaborative Tagging is a powerful method to create folksonomies that can be used to grasp/filter user preferences or enhance web search. Recent research has shown that depending on the number of users and the quality of user-provided tags powerful community-driven semantics or "ontologies" can emerge - as it was evident analyzing user data from social web applications such as del.icio.us or Flickr. Unfortunately, most web pages do not contain tags and, thus, no vocabulary that describes the information provided. A common problem in web page annotation is to motivate users for constant participation, i.e. tagging. In this paper we describe our approach of a binary verification game that embeds collaborative tagging into on-line games in order to produce domain specific folksonomies.

In this work we present an approach that uses a neural net for an online control of the cooling process in light metal die casting industry. Normally the die casting process is controlled manually or semi-manually, and quality control is done well after the cooling process. In our approach we increase the product quality during the production process by monitoring the cooling process with an infra red camera and heating or cooling different parts of the mold. The control is done using a neural net, which has been trained with data from previous casting processes, where the quality has been judged by experts. We conclude that this approach is a feasible way to online monitor and increase product quality in die casting.

Two-sided pressure input is common in everyday interactions such as grabbing, sliding, twisting, and turning an object held between thumb and index finger. We describe and demonstrate a research prototype which allows for twosided multitouch sensing with continuous pressure input at interactive rates and we explore early ideas of interaction techniques that become possible with this setup. The advantage of a two-sided pressure interaction is that it enables high degree-of-freedom input locally. Hence rather complex, yet natural interactions can be designed using little finger motion and device space.

The use of public transport vehicles, such as trams, buses, and taxis as an advertising space is increasing since several years. However mainly the outside of the vehicles is used to show advertisements using paintings, foil or roofmounted displays. Nowadays, with advances in display technologies, small highresolution displays can be easily embedded in vehicles and be used for entertainment or advertising purposes. In this paper we introduce an interactive context-ware advertising system designed for cabs, which is targeted to offer context-aware information such as advertisements, points of interest, events, etc. during a cab ride. Additionally it is possible for advertisers to upload their contents and define areas where their advertisements should be shown.

Reduction of noise is a growing subject of interest in the automotive industry, especially in tire manufacturing. After construction of the basic tire design, that is design of the material and the basic building blocks called pitches, the last step in noise engineering of a tire is the determination of the pitch sequence of a tire. In this step the different types of pitches are put together regarding several constraints. Since there are a combinatorial number of valid pitch sequences, the goal is to find a valid pitch sequence with optimal noise characteristics. Due to the complexity of the problem, the globally optimal pitch sequence cannot be found by exhaustive search and intelligent algorithms such as Heuristic Optimization Algorithms, have to be used in order to find at least a locally optimal pitch sequence. Several successful approaches for this problem can be found in the literature for tires consisting out of just one pitch sequence. In this work tires consisting out of multiple pitch sequence (several tracks) are considered. We show how we can use algorithms for single track optimization and how we can combine them best for finding noise optimal tire designs for multiple pitch track tires.

In this paper we argue that for wide deployment, interactive surfaces should be embedded in real environments as unobtrusively as possible. Rather than deploying dedicated interactive furniture, in environments such as pubs, cafés, or homes it is often more acceptable to augment existing tables with interactive functionality. One example is the use of robust camera-projector systems in real-world settings in combination with spatially tracked touch-enabled personal devices. This retains the normal usage of tabletop surfaces, solves privacy issues, and allows for storage of media items on the personal devices. Moreover, user input can easily be tracked with high precision and low latency and can be attributed to individual users.

We demonstrate how multi-touch hand gestures in combination with foot gestures can be used to perform navigation tasks in interactive systems. The geospatial domain is an interesting example to show the advantages of the combination of both modalities because the complex user interfaces of common Geographic Information System (GIS) requires a high degree of expertise from its users. Recent developments in interactive surfaces that enable the construction of low cost multi-touch displays and relatively cheap sensor technology to detect foot gestures allow the deep exploration of these input modalities for GIS users with medium or low expertise. In this paper, we provide a categorization of multitouch hand and foot gestures for the interaction with spatial data on a large-scale interactive wall. In addition we show with an initial evaluation how these gestures can improve the overall interaction with spatial information.

Combining GPS tracks with semantic annotations is the basis for large data analysis tasks that give insight into the movement behavior of populations. In this paper, we present a first prototype implementation of a GPS tracking application that aims at subsuming GPS tracking and manual annotation on a standard mobile phone. The main purpose of this prototype is to investigate its usability, which is achieved by a tilt- and motion-sensing interface. We provide a GPS diary function that visualizes GPS trajectories on a map, allows annotating the trajectory, and navigating through the trajectory by moving and tilting the mobile phone. We present the design of our application and report on the very first user experiences.

In this paper we present a survey of several methods, that are suitable for modeling service systems with inventory control. One Markovian approximation method is extended with priorities. These approaches also can be coupled with optimization algorithms, where here the Taguchi method and ant algorithms are considered and a serial four stage example is given.

We compare two approaches for misbehavior detection in sensor wireless networks based on artificial immune systems (AIS) and neural networks (NN). We conclude that AIS and NN based misbehavior detection offers a decent detection performance at a very low computational cost. However both approaches are different regarding the length of the preprocessing phase, memory requirements, speed of computation and the rate of false positives. Both approaches are suitable for misbehavior detection in sensor networks, the decision which approach to choose for a specific sensor network depends on the details of the scenario.

In this paper we explore spatial audio as a new design space for applications like teleconferencing and audio stream management on mobile devices. Especially in conjunction with input techniques using motion-tracking, the interaction has to be thoroughly designed in order to allow low-dimensional input devices like gyroscopic sensors to be used for controlling the rather complex spatial setting of the virtual audio space. We propose a new interaction scheme that allows the mapping of low-dimensional input data to navigation of a listener within the spatial setting.

Some public display systems provide information that is vital for people in their vicinity (such as departure times at airports and train stations) whereas other screens are more ambient (such as displays providing background information on exhibits in a museum). The question we are discussing in this paper is how to design interaction mechanisms for the latter, in particular how mobile phones can be used to enable opportunistic and leisurely interaction. We present results from an investigation into the use and perception of a public display in a café, and we derive some requirements for phone-based interaction with (ambient) public displays. Based on these requirements, we briefly evaluate three different interaction techniques.

Negotiation and coordination of activities involving a number of people can be a difficult and time-consuming process, even when all participants are collocated. We propose the use of spatial proximity regions around mobile devices on a table to significantly reduce the effort of proposing and exploring content within a group of collocated people. In order to determine the location of devices on ordinary tables, we developed a tracking mechanism for a camera-projector system that uses dynamic visual markers displayed on the screen of a device. We evaluated our spatial proximity region based approach using a photo-sharing application for people sat around a table. The tabletop provides a frame of reference in which the spatial arrangement of devices signals the coordination state to the users. The results from the study indicate that the proposed approach facilitates coordination in several ways, for example, by allowing for simultaneous user activity and by reducing the effort required to achieve a common goal. Our approach reduced the task completion time by 43% and was rated as superior in comparison to other established techniques.

Virtual globes have progressed from little-known technology to broadly popular software in a mere few years. We investigated this phenomenon through a survey and discovered that, while virtual globes are en vogue, their use is restricted to a small set of tasks so simple that they do not involve any spatial thinking. Spatial thinking requires that users ask "what is where" and "why"; the most common virtual globe tasks only include the "what". Based on the results of this survey, we have developed a multi-touch virtual globe derived from an adapted virtual globe paradigm designed to widen the potential uses of the technology by helping its users to inquire about both the "what is where" and "why" of spatial distribution. We do not seek to provide users with full GIS (geographic information system) functionality, but rather we aim to facilitate the asking and answering of simple "why" questions about general topics that appeal to a wide virtual globe user base.

Many mobile devices, specifically mobile phones, come equipped with a microphone. Microphones are high-fidelity sensors that can pick up sounds relating to a range of physical phenomena. Using simple feature extraction methods, parameters can be found that sensibly map to synthesis algorithms to allow expressive and interactive performance. For example blowing noise can be used as a wind instrument excitation source. Also other types of interactions can be detected via microphones, such as striking. Hence the microphone, in addition to allowing literal recording, serves as an additional source of input to the developing field of mobile phone performance.

Real-world objects (and the world) are usually not at. It is unfortunate, then, that mobile augmented reality (AR) applications often concentrate on the interaction with 2D objects. Typically, 2D markers are required to track mobile devices relative to the real-world objects to be augmented, and the interaction with these objects is normally limited to the xed plane in which these markers are located. Using platonic solids, we show how to easily extend the interaction space to tangible 3D models. In particular, we present a proof-of-concept example in which users interact with a 3D paper globe using a mobile device that augments the globe with additional information. (In other words, mobile interaction with the "real world".) We believe that this particular 3D interaction with a paper globe can be very helpful in educational settings, as it allows pupils to explore our planet in an easy and intuitive way. An important aspect is that using the real shape of the world can help to correct many common geographic misconceptions that result from the projection of the earth's surface onto a 2D plane.

In the past many researchers and companies have focused on mastering different multitouch interface technologies, yet there are currently still only few applications that are truly using the full capabilities of multitouch. In this paper we describe our vision for new multitouch interaction metaphors based on finger and hand gestures especially suited for 3d conceptual modeling and show some ideas about the context in which such a multitouch system could be useful.

Convincing animations of virtual characters continue to require motion capture technology or extensive skills in manual keyframing. We want to outline a simple yet natural motion capturing method that takes advantage of multitouch input devices to create believable character motion.

On mobile devices, navigating in high-resolution and high-density 2D information spaces, such as geographic maps, is a common and important task. In order to support this task, we expand on work done in the areas of tilt-based browsing on mobile devices and speed-dependent automatic zooming in the traditional desktop environment to create an efficient interface for browsing high-volume map data at a wide range of scales. We also discuss infrastructure aspects, such as streaming 2D content to the device and efficiently rendering it on the display, using standards such as Scalable Vector Graphics (SVG).

Reducing noise is a growing subject of interest in the automotive industry, especially in tire manufacturing. When it comes to tires with spikes then the reduction of noise is an urgent issue. The placement of spikes on a given tire is combinatorial problem with constraints, since there are restrictions imposed by the traffic law as well as restrictions stemming from the production process. In this work we show that the application of heuristic optimization algorithms is usually not feasible because of the problem size that makes it impossible to find even one valid spike distribution with simple methods. We show three approaches based on the divide and conquer strategy that show promising results, one approach even including an optimization strategy in a genetic algorithms like style. As result our powerful algorithms are now used successfully in tire industry in order to produce valid and noise reduced spike distributions.

Adding security mechanisms to computer and com-munications systems without degrading their performance is a difficult task. This holds especially for wireless ad hoc networks that, due to their physical and logical openness, are easier to attack than wired networks. Additionally, such networks are expected to have less resources in terms of computational capabilities and must also rely on batteries for power supply. We investigate the impact of two misbehavior detection mechanisms based on Neural Networks and Artificial Immune Systems. In the performance analysis we assume that wireless devices, in many scenarios, must work with extremely limited computational resources. An example of such a scenario are sensor networks. This implicates that the security system of choice has to be very efficient in order not to disturb the normal wireless device operation.

One compelling scenario for the use of GPS enabled phones is support for navigation, e.g. enabling a user to glance down at the screen of her mobile phone in order to be reassured that she is indeed located where she thinks she is. While service based approaches to support such navigation tasks are becoming increasingly available - whereby a user downloads (for a fee) a relevant map of her current area onto her GPS enabled phone, the approach is often far from ideal. Typically, the user is unsure as to the cost of downloading the map (especially when she is in a foreign country) and such maps are highly generalised and may not match the user's current activity and needs. For example, rather than requiring a standard map on a mobile device of the area, the user may simply require a map of a university campus with all departments or a map showing footpaths around the area in which she is currently trekking. Indeed, one will often see such specialised maps on public signs situated where they may be required (in a just-in-time sense) and it is interesting to consider how one might enable users to walk up to such situated signs and use their mobile phone to `take away' the map presented in order to use it to assist their ongoing navigation activity. In this paper, we are interested in a subset of this problem space in which the user `grabs' a map shown on a public display by taking a photograph of it and using it as a digital map on her mobile phone. We present two di erent scenarios for our new application called PhotoMaps: In the rst one we are having full control on the map design process (e.g. we are able to place markers etc., in the second scenario we use the map as it is and appropriate it for further navigation use.

Information navigation on handheld displays is characterized by the small display dimensions and limited input capabilities of today’s mobile devices. Special strategies are required to help users navigate to off-screen content and develop awareness of spatial layouts despite the small display. Yet, handheld devices offer interaction possibilities that desktop computers do not. Handheld devices can easily be moved in space and used as a movable window into a large virtual workspace. We investigate different information navigation methods for small-scale handheld displays using a range of sensor technologies for spatial tracking. We compare user performance in an abstract map navigation task and discuss the tradeoffs of the different sensor and visualization techniques.

The exploitation of finger and hand tracking technology based on infrared light, such as FTIR, Diffused Illumination (DI) or Diffused Surface Illumination (DSI) has enabled the construction of large-scale, low-cost, interactive multi-touch surfaces. In this context, access and security problems arise if larger teams operate theses surfaces with different access rights. The team members might have several levels of authority or specific roles, which determine what functions and objects they are allowed to access via the multi-touch surface. In this paper we present first concepts and strategies to authenticate and interact with subregions of a large-scale multi-touch wall.

When camera phones are used as magic lenses in handheld augmented reality applications involving wall maps or posters, pointing can be divided into two phases: (1) an initial coarse physical pointing phase, in which the target can be directly observed on the background surface, and (2) a fine-control virtual pointing phase, in which the target can only be observed through the device display. In two studies, we show that performance cannot be adequately modeled with standard Fitts' law, but can be adequately modeled with a two-component modification. We chart the performance space and analyze users' target acquisition strategies in varying conditions. Moreover, we show that the standard Fitts' law model does hold for dynamic peephole pointing where there is no guiding background surface and hence the physical pointing component of the extended model is not needed. Finally, implications for the design of magic lens interfaces are considered.

The mobile phone is the first truly pervasive computer. In addition to its core communications functionality, it is increasingly used for interaction with the physical world. This chapter examines the design space of input techniques using established desktop taxonomies and design spaces to provide an indepth discussion of existing interaction techniques. A new five-part spatial classification is proposed for ubiquitous mobile phone interaction tasks discussed in our survey. It includes supported subtasks (position, orient, and selection), dimensionality, relative vs. absolute movement, interaction style (direct vs. indirect), and feedback from the environment (continuous vs. discrete). Key design considerations are identified for deploying these interaction techniques in real-world applications. Our analysis aims to inspire and inform the design of future smart phone interaction techniques.

In this work we evaluate the feasibility of both classical machine learning algorithms and bio-inspired algorithms for misbehavior detection in sensor networks, since recent works in that field seem to concentrate mainly on bio-inspired approaches, without a convincing rational reason. As a first step, we analyze the packet traffic of a simulated sensor network in order to find relevant features that distinguish normal network operation from misbehaving nodes. This kind of data analysis is often missing in previous studies. Using these features acquired by the systematic data analysis we study the suitability of classical machine learning algorithms as well as bio-inspired learning algorithms for the given classification problem. We conclude which algorithms perform best in this special scenario, considering classification success and resource-friendliness of the algorithms. As result we can say that classical algorithms have equal or even better detection capabilities compared to some bio-inspired algorithms. It turns out that it is even possible to detect different levels of misbehavior with nearly 100% accuracy.

For multi-user multi-touch tables with around the table interaction, orientation of items on screen (such as text) is a problem. We address this issue by proposing a technique to detect the location of users around a multi-touch table. We discuss sensors and algorithms to be used, and benefits of the proposed sensors as well as possible applications.

The development of FTIR (Frustrated Total Internal Reflection) technology has enabled the construction of large-scale, low-cost, multi-touch displays. These displays—capable of sensing fingers, hands, and whole arms—have great potential for exploring complex data in a natural manner and easily scale in size and the number of simultaneous users. In this context, access and security problems arise if a larger team operates the surface with different access rights. The team members might have different levels of authority or specific roles, which determines what functions they are allowed to access via the multi-touch surface. In this paper we present first concepts and strategies to use a mobile phone to spontaneously authenticate and interact with sub-regions of a large-scale multi-touch wall.

The theory of modeling formalisms for Discrete Event Systems has a long history and is well developed, many algorithms for modeling and efficient analysis of the modeled systems exist. However in many practical applications or commercial software, the theory is not used. The reasons are manifold. The question is, whether the theoretical concepts are not suited for practical applications, or whether the problem lies in the proper transfer to practice. Other problems lie in the sometimes missing flexibility of theoretical models, to some extend in missing good software that would enable the practical use of such models. In this work we review Petri net based methodologies with regard to their applicability in practice, and try to understand why many aspects of the theory of modeling and simulation do not find their way into practice. We identify crucial factors such as support of complex models and hierarchic modeling capabilities. These factors not only concern the modeling methodology, but also need to be implemented in a software tool. The availability of a software supporting a modeling concept is another important factor. The software should also have an adequate and appealing graphical representation because at the end, the practitioners have to be convinced to’buy’the theoretical concept, and that will only be the case, if decision makers can recognize’their’system easily. Furthermore we survey a number of papers about application of Petri nets to find out to which extend these applications are practical ones, ie whether the applications are of academic nature, proof of concept, toy size or inside a productive environment.

In this paper an automatic transformation of arbitrary manufacturing models (modeled as queuing net or stochastic Petri net) to an interactive 3D visualization and animation (realized in a game-engine) is presented. The motivation behind this is, to make the very useful but rather boring mathematical models formulated as queuing net or Petri net easily accessible for users and decision makers, who are not interested in the details of the mathematical modeling formalism. Queuing networks and Petri nets have a long tradition and are a well accepted means for modeling, simulation and analysis of discrete event systems. Although these formalisms have a graphical notation intuitive to use for experts, they lack a good presentation layer which is needed for acceptance in industry or for commercial purposes, or for academic non experts.

In this article we evaluate and compare diverse methodologies for designing low-noise tread profiles. Finding a low noise tread profile under given constraints can be described as a search in search space which is typically of the order of a 50– to 70-dimensional vector space. A complete search for the optimal tread profile is not possible even with today's computers. Thus in this work we compare the feasibility of three classes of algorithms for tread profile construction. First, we discuss approaches of speeding up the generation and analysis of tread profiles. Second we use two algorithms for iterative construction of large tread profiles out of several smaller tread profiles known to be of good quality. One of these algorithms is based on Neural Networks. Third, we evaluate heuristic optimization algorithms such as Genetic Algorithms and Simulated Annealing. Last we compare suitability and efficiency of our approaches.

The main task of a Wireless Sensor Network (WSN) is to collect data and either send it to a base station immediately or to store it locally until the data is requested by a base station. WSN form a wireless network without specific infrastructure thus efficient routing protocols are necessary to let a data packet find its way from one specific sensor node through the network to the base station. Since WSN are a quite new technology, in a first step existing routing protocols from other types of wireless networks have been employed in WSN. However these protocols are not well suited for WSN, since the characteristics of the technology and the application of other wireless networks may be quite different from those in WSNs. As consequence the adopted routing protocols often perform badly in the context of WSN. In this work we study the usability of several routing protocols in a real world environmental monitoring task and show how the performance of wireless routing protocols can be improved significantly if adapted carefully for the use in WSN. Finally, the performance of the different available routing protocols is then measured and compared through actual deployment of the WSN using cricket motes, which have been designed by U.C. Berkeley.

In this paper we report about deployment of genetic algorithms in order to optimize tread profiles for tires that will produce an unobtrusive noise. Since the complexity of the problem grows exponentially (the search space is typically of the order of a 65-dimensional vector space), a complete search for the optimal tread profile is not possible even with today's computers. Thus heuristic optimization algorithms are an appropriate means to find (near) optimal tread profiles. We discuss approaches of speeding up the generation and analysis of tread profiles, and results using genetic algorithms.

In this paper we report about deployment of intelligent optimisation algorithms for noice reduction in tire manufacturing. Since the complexity of the problem grows exponentially (the search space is typically of the order of a 65-dimensional vector space), a complete search for the optimal tread profile is not possible even with today’s computers. Thus heuristic optimization algorithms such as Genetic Algorithms and Simulated Annealing are an appropriate means to find (near) optimal tread profiles. We discuss approaches of speeding up the generation and analysis of tread profiles, and results using various optimization algorithms.

We review recent approaches to dealing with misbehavior in ad hoc wireless networks. We focus on a specific class of solutions that are based on autonomic computing. This class is motivated by the very efficient and complex system that is able to protect the health of humans against an amazing set of malicious extraneous attacks. We also provide the reader with a summary of misbehavior that is currently considered in the literature. Certain aspects of machine learning and game theory with relevance to misbehavior detection are reviewed as well. Based on relevant design properties of Artificial immune systems motivated by human immunity we present an outline of a four-layer architecture for ad hoc wireless networks. The purpose of this architecture is to impose a high degree of survivability against misbehavior of nodes.

In this article we use the Ant Colony Optimisation (AGO) algorithm in order to find optimal Kanban allocations in Kanban systems represented by Stochastic Petri Net (SPN) models. Like other optimisation algorithms inspired by nature, such as Simulated Annealing/Genetic Algorithms, the AGO algorithm contains a large number of adjustable parameters. Thus we study the influence of the parameters on performance of AGO on the Kanban allocation problem, and identify the most important parameters.

In this article we study the feasibility of the Ant Colony Optimisation (ACO) algorithm for finding optimal Kanban allocations in Kanban systems represented by Stochastic Petri Net (SPN) models. Like other optimisation algorithms inspired by nature, such as Simulated Annealing/Genetic Algorithms, the ACO algorithm contains a large number of adjustable parameters. Thus we study the influence of the parameters on performance of ACO on the Kanban allocation problem, and identify the most important parameters.

Complex systems such as flexible manufacturing systems and traffic systems typically evolve with alternating periods of transient and nearly steady-state behavior; such systems often show suboptimal performance. Thus, it is desirable to optimize the system’s performance on-line by adjusting the system’s parameters properly before a performance drop is to occur. To this end, the system’s future evolution is assessed in advance repeatedly by means of on-line simulation. However, there are several problems accompanying this approach, particularly the demand of real-time decisions, that have not been sufficiently solved yet. Aiming at studying the dynamics of on-line control as well as its impact on the system’s operation, we built a stochastic Petri net model that simulates online control of a simple open queueing network as it performs by means of on-line simulation. The system under control is easy to study since it has known properties and can be considered as part of a manufacturing system; jobs arriving at the system have to be dispatched to one of two machines, each providing a queue for jobs waiting to be processed. The processing times of the machines are deterministic or stochastic, while the jobs’ arrival times are stochastic. With on-line simulation, the system’s future performance is assessed by virtually dispatching a new job to either of the machines, based on the system’s current state; the results are compared and thus lead to the real decision concerning to what machine the new job should be dispatched in order to minimize the work in progress.

Most studies employing Petri nets in semiconductor manufacturing model only one specific area (e.g. etching) in detail, and model the rest of the manufacturing process, e.g. by abstract input/output behavior. In our study, we show the feasibility of using Petri nets for modeling the complete production process. We use the first set of test data provided by the MASM-LAB, Arizona State University. It is a process of a two-product system making non-volatile memory chips. For modeling, we use our own tool PSim, which is based on a combined queuing and Petri net formalism. The integration of queues makes the modeling of parts waiting in front of a machine quite concise and intuitive. PSim offers a hierarchical and modular modeling approach, which is especially feasible for large and complex systems. We use the modular approach by once defining the structure of a machine as Petri net and then instantiating as many machines as needed. Then we model the operators, resources and the movement of parts between the machines as specified in the production plan. As a result, we can state that Petri nets are feasible for modeling a complete semiconductor manufacturing process.

In this case study, two alternatives for reconstruction of an existing shiplift are evaluated. At the moment, the shiplift consists of two long chambers. One chamber is to be rebuilt. Instead of rebuilding it in its original length, a shorter and cheaper chamber could also be built.

In this paper, we present a tool (DIMON) for distributed modeling of nets such as queueing networks or Petri nets or combinations of both over an IP based computer network, together with a 3-D graphical editor (DIM3ON) for modeling hierarchical nets utilizing that tool. Both the tool and the editor are implemented in Java. In this implementation, the net concept is considered as a superclass and thus can be extended by inheritance to any more specialized concept, eg, to a stochastic Petri net (note that the Petri net concept itself is a subclass of the net concept). The editor is designed to be extensible in a rather easy manner in order to consider yet unsupported net classes. The nets are specified using the Extensible Markup Language (XML) in order to facilitate storage and interchange across a computer network.

Two different types of timed Petri nets that contain continuous tokens have been developed separately. Fluid Stochastic Petri Nets (FSPN) are stochastic Petri nets enhanced by continuous places. Continuous places can be filled from ordinary transitions, while the transitions are enabled by discrete places. Hybrid Petri Nets (HPN) are stochastic Petri nets enhanced by continuous places and continuous transitions. Both kinds of transitions can be enabled by both kinds of places, and both kinds of transitions can be connected by arcs to/from both kinds of places (of course with some restrictions). Each of the continuous Petri net formalisms provides interesting analysis methods, and both formalisms experienced a lot of extensions on modeling level after their first introduction. In this paper, we compare the modeling power of the basic versions and of some extensions of both formalisms. As result we show, that in general, FSPNs can be emulated with HPNs, and vice versa, however depending on the versions considered. Thus, there is no essential difference in both formalisms. A transformation of one type of net to the other one can be found, if for some reason (eg, use of different analysis methods) the other formalism is to prefer.

During a case study we encountered some problems, which could be solved manually this time, but pose a grand challenge regarding a generally applicable methodology. The case study was about verification and performance evaluation of a Fault Tolerant Computer (FTC) System to be employed in the International Space Station (ISS). Four different specifications of the FTC had to be developped for different purposes (chronologically ordered): the informal specification (Data Flow Diagram), OCCAM code (implementation), a CSP model (deadlock-analysis), and a GSPN-model for performance evaluation. Each model has been derived from the predecessors, mostly manually. This was an enduring and error-prone process, for which an integrated methodology should be developed. Why this is urgently necessary, and why this is a challenge and what steps might lead to a possible solution, these questions will be answered in this paper.

In this paper, we extend Petri Nets including Queueing Networks (PNiQs) with several job classes and define Multi Class-PNiQs (MC-PNiQ). A MC-PNiQ is a Generalized Stochastic Petri Net (GSPN) which contains multiclass queueing networks (MC-QNs). This approach allows to combine the advantages of both concepts on the modelling level as well as on the analysis level. The use of MC-QNs permits concise modelling of waiting room, server and queueing and offers many fast analysis algorithms for large multiclass systems. Additionally, GSPN provide the expressiveness and flexibility for modelling of more complicated structures like fork/join, etc. The definition of MC-PNiQs is especially designed to allow a qualitative analysis based on a reduced state space, as well as automated approximate analysis by aggregation of the multi-class queueing nets and replacing them with GSPN elements. The resulting GSPN can then be analyzed with state-of-the-art methods and tools.

Integrated performance and dependability analysis, called performability has been receiving considerable attention in the design of complex, fault-tolerant systems. We present Petri Nets including Queueing Networks (PNIQ) a novel high-level modeling technique, which is particularly appropriate for performability evaluation. The definition integrates concepts of generalized stochastic Petri nets (GSPN) and Queueing Networks on the modeling level and specifies interfaces between them. Steady state solution is based on aggregation of queueing networks and replacing them with GSPN constructs that model the delays of tokens introduced by queueing nets. The resulting GSPN model can be analyzed with state of the art methods and tools. This process can be carried out automatically. Applicability of PNIQ for evaluation of performability is shown in an example.

Generalised stochastic Petri nets (GSPN) and queuing networks are combined at the modelling level by defining Petri Nets including Queuing Networks (PNiQ). The definition is especially designed to allow approximate analysis by aggregation of the queuing nets and replacing them with GSPN elements. Usually the aggregation of combined GSPN and queuing network models is carried out manually which limits the use of this technique to experts and furthermore may easily lead to modelling errors and larger approximation errors than inherent in the method. These are avoided by the definition of PNiQ which shows how to incorporate queuing networks into GSPN and provides interfaces between them. This makes combined modelling easier and less error-prone. Steady state analysis of the model can be carried out automatically: queuing network parts are analysed with efficient queuing network algorithms for large nets and replaced by GSPN subnets that model the delay of tokens in the queuing network. The resulting GSPN can then be handled with state-of-the-art tools.

Until very recently genetic algorithms GAs were considered to be the proprietary field of general systems theoreticians and important for esoteric or extremely complex optimization studies. This paper endeavors to show that GA are of great utility in cases where complex systems have to be designed and, therefore, rational choices have to be made. The GA approach is based loosely on the theory of natural evolution, genetic diversity, and searching for beneficial adaptations to a complicated and changing environment. GAs can be viewed as a modelling tool and as a technique for simulation of complex systems represented by communities of interacting units. The representation of units can express characteristics, capabilities, or relatively simple strategies. These units compete and are modified by external operators, so that the overall system adapts to its environment. That environment defines the criterion by which the success in adapting can be measured. Genetic algorithms have been successfully applied to many optimization problems including mathematical function optimization, very large scale integration VLSI chip layout, molecular docking, parameter fitting, scheduling, manufacturing, clustering, machine learning, etc. and are still finding increasing acceptance. Modelling and optimization of a Kanban system from the field of flexible manufacturing systems is discussed in the last section.

We investigate the kanban assignment problem for assembly kanban systems. We use REMO, a general purpose tool for optimization. REMO includes several algorithms like hill climbing and genetic algorithms and has an easily adaptable interface to performance analysis tools. As we try to find an optimal kanban assignment with respect to certain performance measures of the system, a fast performance analysis is a crucial factor for sensible and successful application of optimization algorithms. For this purpose we introduce Petri nets including queueing nets (PNiQ) as modeling formalism especially suited for optimization of arbitrary kanban systems. At modeling level, PNiQ allow the use of both the concise description of queueing nets where possible and the notation of stochastic Petri nets where needed, e.g. to model fork/join needed for the matching of kanbans and parts. Approximate performance analysis is carried out by decomposition and aggregation of the queueing net parts. This technique provides a fast numerical solution even for large systems as important requirement for the application of optimization algorithms. The optimization not only yields optimal kanban assignments for various kanban systems but also a common pattern in the set of solutions can be recognized.

In modern broadband systems several on/off traffic sources transmit over a common telecommunication network. Since the network has a finite capacity, the probability of a breakdown due to congestion increases the more sources simultaneously send data packets. In case of a failure due to congestion a time consuming recovery procedure resolves the overload situation. During this procedure no service can be provided for the traffic sources. In this paper we model this scenario with generalized stochastic Petri nets and investigate the influence of several system parameters on the performability of the system. For these parameters (number of traffic sources in the system, length of on/off period in send modus and length of send/idle period of the sources) we try to find optimal settings which maximize the number of transmitted data packets. Optimization was performed with the tool REMO. Moreover we model and optimize a dynamic decision rule which decides, dependent on the load situation, whether to admit an additional source or not. These investigations could be used to create guidelines for service providers how to optimally operate the system.

Im Zuge der raschen Entwicklung und Globalisierung internationaler Märkte sind die Unternehmen gezwungen, auf stark fluktuierende Nachfrageänderungen zu reagieren. Aus dieser Notwendigkeit hat sich die Just-in-Time Philosophie entwickelt, die zum Ziel hat, Lagerbestand und Durchlaufzeiten gering zu halten, um sich schnell an eine neue Marktsituation anpassen zu können. Der Kanban-Mechanismus ist eine Möglichkeit, den Fluß der Teile in einer Fertigungsanlage im Sinne der JIT Philosophie zu steuern. In der Literatur gibt es einige Ansätze zur Analyse von Kanban gesteuerten Produktionssystemen [1],[2], es gibt bisher aber keine Arbeiten, die mehrere Klassen, Rüstzeiten und Prioritäten berücksichtigen. Deshalb erweitern wir den Analyseansatz von Mitra und Mitrani [1] auf die Behandlung von zwei Produktarten, Umrüstzeiten und Prioritäten. Motiviert wurde die Arbeit durch ein Problem aus der Halbleiterfertigung, wo “Engineering” — Wafer Priorität vor regulären Wafer haben.