Braunschweig, Germany
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Hernandez H.,Polytechnic University of Catalonia | Blesa M.J.,Polytechnic University of Catalonia | Blum C.,Polytechnic University of Catalonia | Baumgartner T.,Braunschweig Institute of Technology | And 2 more authors.
Proceedings - 2010 6th International Conference on Mobile Ad-hoc and Sensor Networks, MSN 2010 | Year: 2010

In this work we present a protocol for self-synchronized duty-cycling in wireless sensor networks with energy harvesting capabilities. The protocol is implemented in Wiselib, a library of generic algorithms for sensor networks. Simulations are conducted with the sensor network simulator Shawn. They are based on the specifications of real hardware known as iSense sensor nodes. The experimental results show that the proposed mechanism is able to adapt to changing energy availabilities. Moreover, it is shown that the system is very robust against packet loss. © 2010 IEEE.

Barth T.,Braunschweig Institute of Technology | Scholz P.,Braunschweig Institute of Technology | Scholz P.,Institute of Fluid Mechanics | Wierach P.,German Aerospace Center | Wierach P.,German Institute of Composite Structures and Adaptive Systems
AIAA Journal | Year: 2011

This paper describes a study of dynamical vane vortex generators in a flow over a flat plate. Fluidic vortex generators are more effective when operated dynamically. Thus, it is the aim of this study to find out whether mechanical vortex generators are also superior under dynamic operating conditions. The motion of the vortex generators is generated by piezoceramic actuators constructed in a bimorph configuration, which consists of a carbon-fiber bar covered with piezoceramic face actuators. The actuators exploit the longitudinal piezoelectric effect (d33 effect), they are operated in resonance to reach the required displacement and generate a sinusoidal motion of the vortex generators. Vortex generators and actuators were integrated into a flat plate in a low-speed wind tunnel. A stereo particle image velocimetry system was used to record phase-locked flowfields that were analyzed using vortex classification methods. It was found that the transient development of the vortex core position and circulation is very different from that of static vanes. While vortices from static vortex generators are able to survive over a considerable distance, the vortices from dynamically driven ones decay faster. It is argued that the dynamic vortices have a greater ability to reorganize the momentum in the turbulent boundary layer. Copyright © 2010 by Peter Scholz.

Fekete S.P.,Braunschweig Institute of Technology | Kamphans T.,Braunschweig Institute of Technology | Kroller A.,Braunschweig Institute of Technology | Mitchell J.S.B.,State University of New York at Stony Brook | Schmidt C.,Braunschweig Institute of Technology
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

We consider online and offline problems related to exploring and surveying a region by a swarm of robots with limited communication range. The minimum relay triangulation problem (MRTP) asks for placing a minimum number of robots, such that their communication graph is a triangulated cover of the region. The maximum area triangulation problem (MATP) aims at finding a placement of n robots such that their communication graph contains a root and forms a triangulated cover of a maximum possible amount of area. Both problems are geometric versions of natural graph optimization problems. The offline version of both problems share a decision problem, which we prove to be NP-hard. For the online version of the MRTP, we give a lower bound of 6/5 for the competitive ratio, and a strategy that achieves a ratio of 3; for different offline versions, we describe polynomial-time approximation schemes. For the MATP we show that no competitive ratio exists for the online problem, and give polynomial-time approximation schemes for offline versions. © 2011 Springer-Verlag.

Baumgartner T.,Braunschweig Institute of Technology | Chatzigiannakis I.,Research Academic Computer Technology Institute | Chatzigiannakis I.,University of Patras | Fekete S.,Braunschweig Institute of Technology | And 4 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

One unfortunate consequence of the success story of wireless sensor networks (WSNs) in separate research communities is an ever-growing gap between theory and practice. Even though there is a increasing number of algorithmic methods for WSNs, the vast majority has never been tried in practice; conversely, many practical challenges are still awaiting efficient algorithmic solutions. The main cause for this discrepancy is the fact that programming sensor nodes still happens at a very technical level. We remedy the situation by introducing Wiselib, our algorithm library that allows for simple implementations of algorithms onto a large variety of hardware and software. This is achieved by employing advanced C++ techniques such as templates and inline functions, allowing to write generic code that is resolved and bound at compile time, resulting in virtually no memory or computation overhead at run time. The Wiselib runs on different host operating systems, such as Contiki, iSense OS, and ScatterWeb. Furthermore, it runs on virtual nodes simulated by Shawn. For any algorithm, the Wiselib provides data structures that suit the specific properties of the target platform. Algorithm code does not contain any platform-specific specializations, allowing a single implementation to run natively on heterogeneous networks. In this paper, we describe the building blocks of the Wiselib, and analyze the overhead. We demonstrate the effectiveness of our approach by showing how routing algorithms can be implemented. We also report on results from experiments with real sensor-node hardware. © 2010 Springer Berlin Heidelberg.

Fekete S.P.,Braunschweig Institute of Technology | Mitchell J.S.B.,State University of New York at Stony Brook | Schmidt C.,Braunschweig Institute of Technology
Journal of Combinatorial Optimization | Year: 2012

Given a polygon and a visibility range, the Myopic Watchman Problem with Discrete Vision (MWPDV) asks for a closed path P and a set of scan points S, such that (i) every point of the polygon is within visibility range of a scan point; and (ii) path length plus weighted sum of scan number along the tour is minimized. Alternatively, the bicriteria problem (ii) aims at minimizing both scan number and tour length. We consider both lawn mowing (in which tour and scan points may leave P) and milling (in which tour, scan points and visibility must stay within P) variants for the MWPDV; even for simple special cases, these problems are NP-hard. We show that this problem is NP-hard, even for the special cases of rectilinear polygons and L8 scan range 1, and negligible small travel cost or negligible travel cost. For rectilinear MWPDV milling in grid polygons we present a 2.5- approximation with unit scan range; this holds for the bicriteria version, thus for any linear combination of travel cost and scan cost. For grid polygons and circular unit scan range, we describe a bicriteria 4-approximation. These results serve as stepping stones for the general case of circular scans with scan radius r and arbitrary polygons of feature size a, for which we extend the underlying ideas to a φ( r/a + r+1/ 2 ) bicriteria approximation algorithm. Finally, we describe approximation schemes for MWPDV lawn mowing and milling of grid polygons, for fixed ratio between scan cost and travel cost. © Springer Science+Business Media, LLC 2011.

Coulson G.,Lancaster University | Porter B.,Lancaster University | Chatzigiannakis I.,University of Patras | Koninis C.,University of Patras | And 10 more authors.
Communications of the ACM | Year: 2012

Virtual testbeds model them by seamlessly integrating physical, simulated, and emulated sensor nodes and radios in real time.

Hibbeln M.,Braunschweig Institute of Technology | Jenkins J.L.,Brigham Young University | Schneider C.,City University of Hong Kong | Valacich J.S.,University of Arizona | Weinmann M.,University of Liechtenstein
35th International Conference on Information Systems "Building a Better World Through Information Systems", ICIS 2014 | Year: 2014

The completion of online forms is the catalyst for many business and governmental processes. However, providing fraudulent information in such forms is pervasive, resulting in costly consequences for organizations and society. Furthermore, detecting fraudulent responses in online forms is often very difficult, time consuming, and expensive. This research proposes that analyzing users' mouse movements may reveal when a person is being fraudulent. Namely, based on neuroscience and deception theory, the paper explains how deception may influence hand movements captured via the computer mouse. In an insurance fraud context, a study is conducted to explore these proposed relationships. The results suggest that being deceptive may increase the normalized distance of movement, decrease the speed of movement, increase the response time, and result in more left clicks. Implications for human-computer interaction research and practice are discussed.

Baumgartner T.,Braunschweig Institute of Technology | Fekete S.P.,Braunschweig Institute of Technology | Kamphans T.,Braunschweig Institute of Technology | Kroller A.,Braunschweig Institute of Technology | Pagel M.,Braunschweig Institute of Technology
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

We present a sensor network testbed that monitors a hallway. It consists of 120 load sensors and 29 passive infrared sensors (PIRs), connected to 30 wireless sensor nodes. There are also 29 LEDs and speakers installed, operating as actuators, and enabling a direct interaction between the testbed and passers-by. Beyond that, the network is heterogeneous, consisting of three different circuit boards-each with its specific responsibility. The design of the load sensors is of extremely low cost compared to industrial solutions and easily transferred to other settings. The network is used for in-network data processing algorithms, offering possibilities to develop, for instance, distributed target-tracking algorithms. Special features of our installation are highly correlated sensor data and the availability of miscellaneous sensor types. © 2010 Springer-Verlag.

Weinmann M.,Braunschweig Institute of Technology | Hibbeln M.,Braunschweig Institute of Technology | Robra-Bissantz S.,Braunschweig Institute of Technology
19th European Conference on Information Systems, ECIS 2011 | Year: 2011

Product configuration systems are useful instruments of individualization in the field of mass customization. Recent studies have shown that the two factors Expertise and the Motivation to process information have a significant influence on the preference of configurators. In this paper we consider the influence of those two factors on the fit of two types of configuration systems: Parameter-based and Needs-based configurators. While a Parameter-based system allows users to specify design parameters, a Needs-based configurator calculates those parameters based on the users weighted needs. To test the fit of each configurator depending on the Expertise and the Motivation of users, we carried out an experiment. Therefore, we developed a prototype for both types of configuration systems. We found out that Parameter-based systems are more appropriate for customers with high Expertise and high Motivation to process information. Contrary, for customers with low Expertise and Motivation companies are better advised to use Needs-based configurators.

Weinmann M.,Braunschweig Institute of Technology | Schneider C.,City University of Hong Kong | Robra-Bissantz S.,Braunschweig Institute of Technology
ECIS 2013 - Proceedings of the 21st European Conference on Information Systems | Year: 2013

Given people's differences in preferences, personalities, or demographic factors, building useradaptive systems can aid in providing each individual user with the interface that helps to best achieve the desired outcome. For example, online retailers now have the possibility to offer customized Web sites to individual customers, so as to meet each customer's specific needs. However, online retailers typically only have little data available to segment customers in real-Time. In this study, we propose that observable usage data (such as click path data) can be used to distinguish female and male Web site visitors. Drawing on research in psychology and consumer behavior, we hypothesize that observable differences in Web surfing behavior can be indicative of a user's gender. Our results show that women tend to need less time and have shorter click paths than men in online product configuration tasks, and thus confirm the utility of using observable usage data to distinguish Web site visitors based on their gender.

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