@inbook{16409, abstract = {{Given a set of n mobile robots in the d-dimensional Euclidean space, the goal is to let them converge to a single not predefined point. The challenge is that the robots are limited in their capabilities. Robots can, upon activation, compute the positions of all other robots using an individual affine coordinate system. The robots are indistinguishable, oblivious and may have different affine coordinate systems. A very general discrete time model assumes that robots are activated in arbitrary order. Further, the computation of a new target point may happen much earlier than the movement, so that the movement is based on outdated information about other robot's positions. Time is measured as the number of rounds, where a round ends as soon as each robot has moved at least once. In [Cohen, Peleg: Convergence properties of gravitational algorithms in asynchronous robot systems], the Center of Gravity is considered as target function, convergence was proven, and the number of rounds needed for halving the diameter of the convex hull of the robot's positions was shown to be O(n^2) and Omega(n). We present an easy-to-check property of target functions that guarantee convergence and yields upper time bounds. This property intuitively says that when a robot computes a new target point, this point is significantly within the current axes aligned minimal box containing all robots. This property holds, e.g., for the above-mentioned target function, and improves the above O(n^2) to an asymptotically optimal O(n) upper bound. Our technique also yields a constant time bound for a target function that requires all robots having identical coordinate axes. }}, author = {{Cord-Landwehr, Andreas and Degener, Bastian and Fischer, Matthias and Hüllmann, Martina and Kempkes, Barbara and Klaas, Alexander and Kling, Peter and Kurras, Sven and Märtens, Marcus and Meyer auf der Heide, Friedhelm and Raupach, Christoph and Swierkot, Kamil and Warner, Daniel and Weddemann, Christoph and Wonisch, Daniel}}, booktitle = {{Automata, Languages and Programming}}, isbn = {{9783642220111}}, issn = {{0302-9743}}, title = {{{A New Approach for Analyzing Convergence Algorithms for Mobile Robots}}}, doi = {{10.1007/978-3-642-22012-8_52}}, year = {{2011}}, } @inproceedings{14010, abstract = {{Die Modellierung bzw. das virtuelle Design von Ultraschallwandlern spielt gerade im Hinblick auf die Mannigfaltigkeit ihrer Einsatzgebiete und die stetig wachsenden Anforderungen der Industrie eine Schlüsselrolle bei der Entwicklung piezoelektrischer Sensor- und Aktorsysteme. Der jeweils für eine spezielle Anwendung zu erreichende Grad der Realitätsnähe der eingesetzten Modelle ist dabei essentielle Voraussetzung für die Legitimation des virtuellen Designs. Neben idealisierten Strukturen, welche der Modellbildung unweigerlich anhaften, wird die Realitätsnähe wesentlich durch die genutzten Materialmodelle und deren Parametrisierung beeinflusst. Viele Arbeiten wurden aus diesem Grund auf dem Gebiet der akustischen Materialdaten-bestimmung sowohl passiver als auch aktiver Materialien durchgeführt. Ein Ultraschallwandler besteht nun aus einer Komposition von aktiven und passiven Elementen, welche z. B. mittels Klebungen zusammengef{\"u}gt werden. Aktuelle Praxis ist die Vernachl{\"a}ssigung der Klebschichteigenschaften oder ggf. eine Korrektur der durch die Klebschichtdicke hervorgerufene Frequenzverschiebung durch eine virtuelle Vergr{\"o}{\ss}erung eines der F{\"u}geteile. Dabei werden die Koppelbedingungen zwischen den gef{\"u}gten Materialien als ideal angenommen, was in der Realit{\"a}t jedoch nicht der Fall ist. Klebungen sind weder isotrop noch homogen aufgebaut. Des Weiteren ist ihre Dicke sehr klein, was in der Computersimulation dazu f{\"u}hrt, dass sie {\"u}ber effektive Parameter und stark vereinfachte Modelle beschrieben werden.}}, author = {{Bause, Fabian}}, title = {{{Die Auswirkung verschiedener Klebungen auf das Verhalten eines piezoelektrischen Wandlers}}}, year = {{2011}}, } @inproceedings{14011, abstract = {{Ultraschallsensoren werden heute in der Industrie vielfach erfolgreich für die verschiedensten Messaufgaben eingesetzt und ständig weiterentwickelt. Wesentliche aktuelle Entwicklungen zielen auf die Erweiterung der Funktionalität (adaptierbare Abstrahlcharakteristik, scannende Sensoren …), die Erhöhung der Zuverlässigkeit, die Miniaturisierung sowie auf die Reduktion der Gerätekosten (Materialsubstitution) und Fertigungskosten (Konstruktion und Montage). }}, author = {{Henning, Bernd}}, title = {{{Von der Messaufgabe zum Sensorsystem}}}, year = {{2011}}, } @misc{14012, author = {{Bause, Fabian and Olfert, Sergei and Schröder, Andreas and Rautenberg, Jens and Henning, Bernd and Moritzer, Elmar}}, booktitle = {{Journal of Electronic Measurement and Instrument }}, title = {{{Ultrasonic Nondestructive Testing of composite materials using disturbed coincidence conditions}}}, year = {{2011}}, } @inproceedings{14013, abstract = {{Modeling and simulation play a key-role in computer-assisted design of ultrasonic sensors. The accuracy of those numerical or analytical models highly depends on the material dataset chosen as well as on the digitized simplified geometry. Thus, researchers worked on techniques how to measure material datasets of piezoceramics or passive materials (i.e. polymers) for use in simulation [Rau08] [Rup09]. Most computer models neglect the influence of adhesive bonds between those active and passive material components used to form a complete ultrasonic transducer and thus imply perfect interface layers. To gain a more accurate model one need to go further and consider non-perfect interface layers between assembly parts. Because adhesive bonds are neither necessarily isotropic nor homogeneous and their geometric dimensions are very small, we need to define effective material datasets dependent on the model used in simulation. In this contribution the indicator under study is the electric impedance of the active element. We will show the influence of different adhesives used to adhere metal electrodes on piezoceramic discs. Therefore, we use several different types of adhesives (epoxies, cyanoacrylates and perfluorpolyether grease) and different sizes of piezoceramic discs (PIC 255, manufacturer: PI Ceramic GmbH) of the same batch (thickness, diameter). The electrodes have been cut from one plate made of stainless steel using a laser to avoid uncertainty effects due to variations in material-parameters. The probes have been prepared in an air-conditioned Lab with constant temperature and humidity. The indicators considered to identify the effect of those different adhesive films are extracted from the electric impedance of the electromechanical converter.}}, author = {{Bause, Fabian and Rautenberg, Jens and Henning, Bernd}}, location = {{Chengdu, China}}, pages = {{18--23}}, title = {{{Analyzing the effect of adhered metal electrodes on piezoelectric elements using different types of adhesives}}}, volume = {{3}}, year = {{2011}}, } @article{14014, abstract = {{Nowadays ultrasonic distance sensors are widely used in automobiles, robotics and in industrial automation. Some functional principles of usable transducers for airborne ultrasonic distance measurements are shown. As every sensor principle, ultrasonic distance sensors have pros and cons which lead to some problems and challenges described below. For the main challenges (crosstalk and blind zone) some trends and solutions are presented.}}, author = {{Henning, Bernd and Schröder, Andreas}}, journal = {{Journal of Electronic Measurement and Instrument}}, number = {{7}}, pages = {{577--581}}, title = {{{Ultrasonic distance sensors - An overview and trends}}}, volume = {{25}}, year = {{2011}}, } @inproceedings{14015, abstract = {{Es gibt unterschiedliche Methoden, um räumliche Schallwechseldruckverteilungen in Flüssigkeiten zu erfassen. Viele dieser Verfahren haben zwei Nachteile. Sie sind zum einen invasiv, beeinflussen somit die sich ausbreitende Ultraschallwelle, und zum anderen sehr zeitaufwendig. Die Visualisierung von Ultraschallfeldern mittels Schlierenmethode ist eine schnelle und einfache Methode, um zweidimensionale Schallfelder nichtinvasiv zu analysieren. Ein besonderer Vorteil besteht darin, dass man unmittelbar resultierende Veränderungen im Schallfeld zum Beispiel bei Frequenzänderung, Sensorausrichtung… beobachten kann. In diesem Beitrag werden zwei dieser Verfahren vorgestellt. Die modifizierte Schlierenmethode nach Toepler, das im Weiteren als modifizierte Schlierenmethode bezeichnet wird, und die Hintergrund-schlierenmethode, das sich bisher hauptsächlich zur Strömungsvisualisierung etabliert hat [1]. Im ersten Teil werden beide Messverfahren erläutert, die realisierten Messaufbauten sowie Einsatzmöglichkeiten für die Schallfeldcharakterisierung kurz vorgestellt. Im zweiten Teil werden beide Verfahren verglichen und die Vor- und Nachteile bezüglich ausgewählter Messaufgaben bewertet. }}, author = {{Olfert, Sergei and Henning, Bernd}}, location = {{Düsseldorf}}, title = {{{Vergleich zwischen der Schlierenmethode nach Toepler und der Hintergrundschlierenmethode zur Bestimmung akustischer Grössen eines Ultraschallwandlers}}}, year = {{2011}}, } @inproceedings{14016, abstract = {{There has been a lot of progress in finding measurable quantities of high in- formation content for the inverse determination of piezoelectric material properties. Since some material parameters (mainly \textgreek{e}S 11, e15and cE 44) do not or only marginally influence the electrical impedance over frequency, it is not sufficient to look only at the electri- cal impedance of discoidal piezoceramics [1]. Moreover, the parameter sensitivities vary with respect to the diameter--thickness ratio of the disc and the design of an ultrasonic transducer's piezoceramic has to match other requirements than those of a good material characterization [2, 3]. That is why it is still desirable to find model based approaches for parameter identification that either keep the technical effort low (e.g., only an impedance measurement) or increase speed of the inversion procedure. In this contribution we answer the question if an additional analytical approximation of cE 44, strictly following the ideas of Theocaris [4], in conjunction with a single measured elec- trical impedance will be sufficient for an accurate simulation of both, electrical impedance and surface normal velocity of a piezoceramic disc. Thereby, the remaining parameters are identified by means of the Inverse Method. Furthermore, we use the parameter ap- proximation as an initial guess and limiting boundary to speed up the inverse algorithm if both, electrical impedance and surface normal velocity are taken into account within the optimization procedure.}}, author = {{Rautenberg, Jens and Rupitsch, Stefan J. and Henning, Bernd and Lerch, Reinhard}}, booktitle = {{7th International Workshop on Direct and Inverse Problems in Piezoelectricity}}, title = {{{Utilizing an Analytical Approximation for c44E to Enhance the Inverse Method for Material Parameter Identification of Piezoceramics}}}, year = {{2011}}, } @inproceedings{14548, abstract = {{Bei der Luftultraschall-Abstandsmessung mit einem einzelnen Schallwandler ist der Mindestabstand durch die Sendesignaldauer und die Ausschwingzeit des Schallwandlers begrenzt. Daher führt die Verwendung von codierten Sendesignalen, wie sie z.B. für die Unterscheidung mehrerer Sender genutzt werden können, im Allgemeinen zu einer Vergrößerung des Mindestabstandes. Dieser Beitrag zeigt, dass der Mindestabstand bei codierten Sendesignalen durch eine geeignete Signalverarbeitung, bei der eine Trennung des Sende- und Empfangssignals erfolgt, deutlich verringert werden kann.}}, author = {{Schröder, Andreas and Henning, Bernd}}, location = {{Düsseldorf}}, title = {{{Luftultraschall-Abstandsmessung mit verkürztem Mindestabstand}}}, year = {{2011}}, } @inproceedings{14549, abstract = {{Simultaneous transmitting and receiving (STaR) enhances the utilization of single transducer ultrasound measurement systems. In distance measurement applications the dead zone can be reduced to nearly zero, independent of the transmitted signal. So it is possible to transmit codedsignals to identify different sensors without increasing the minimum distance. The electrical transducer signal consists of the electrical transmitted and received signal. A separation of these two signals can be done with a mathematical model of the electrical system. For this purpose it is necessary to digitize the electrical transducer signal. Due to the relative small amplitude of the received signal compared to the transmitted signal amplitude, a high resolution analog to digital converter (ADC) is needed. This leads to high requirements for the ADC. The necessary resolution limits the sample rate of the ADC. By down mixing the transducer signal using a coherent quadrature demodulation (CQD), as used in many high frequency ultrasound applications, the sample rate of the ADC can be reduced. In this contribution an airborne ultrasound distance measurement system with reduced dead zone is used to analyze the effects of this concept to the signal conditioning, system identification and system performance. The approach is compared with a system without CQD and an ADC with a lower resolution but a higher sample rate. By analyzing the pros and cons of both systems the usability of a CQD based system for a STaR application is evaluated. The distance measurement system used for the experiments is based on a 40 kHz airborne ultrasonic transducer. A gyrator based transmit amplifier delivers a system bandwidth of about 10 kHz. In the experiments, coded transmitted signals are used to measure the distance to a metal reflector. The main objectives are short distances between 0 mm and 200 mm. Here a separation of transmitted and received signal is necessary. The reflector distance is calculated by a cross correlation between transmitted and received signal.}}, author = {{Schröder, Andreas and Henning, Bernd}}, title = {{{Model based separation of transmitted and received signal for single transducer distance measurement applications}}}, year = {{2011}}, } @inproceedings{14550, abstract = {{For many applications like level measurement and industry robotics it is of advantage if the directional characteristic of an ultrasonic transducer is changeable or adaptable for the improvement of spatial resolution. Often this goal is reached with the use of ultrasonic transducer arrays, which elements are driven with phase shifted excitation signals. One disadvantage of these solutions is the great effort for building such an array and the multi-channel sensor electronics. In this contribution the directional characteristic of a single air transducer with segmented electrodes is analyzed. Therefore a variable script based finite element model is used to discover the influence of different electrode configurations on the directional characteristic of a single piezoceramic transducer. Especially the influence on the angle of beam and the near field length are evaluated. The used variable model permits an optimization of the configuration with regards to the mentioned criteria. The findings will be used for the development of a level measurement system for bulk solids.}}, author = {{Unverzagt, Carsten and Henning, Bernd}}, keywords = {{Elektrode}}, location = {{Gdansk, Poland}}, title = {{{Finite element simulation of single ultrasonic transducer with segmented electrodes to adjust the directional characteristic}}}, year = {{2011}}, } @inproceedings{13053, author = {{Cook, Alejandro and Hellebrand, Sybille and Indlekofer, Thomas and Wunderlich, Hans-Joachim}}, booktitle = {{5. GMM/GI/ITG Fachtagung "Zuverlässigkeit und Entwurf"}}, pages = {{48--53}}, title = {{{Robuster Selbsttest mit Diagnose}}}, year = {{2011}}, } @inproceedings{13194, author = {{Dembczynski, K. and Waegeman, W. and Cheng, W. and Hüllermeier, Eyke}}, booktitle = {{In Proceedings NIPS-2011, 25th Annual Conference on Neural Information Processing Systems, Granada, Spain}}, title = {{{An exact algorithm for F-measure maximization}}}, year = {{2011}}, } @inproceedings{13195, author = {{Cheng, W. and Fuernkranz, J. and Hüllermeier, Eyke and Park, S.H.}}, booktitle = {{Proceedings ECML/PKDD-2011, European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases, Athens, Greece, }}, title = {{{Preference-based policy iteration: Leveraging preference learning for reinforcement learning}}}, year = {{2011}}, } @inproceedings{13196, author = {{Fürnkranz, J. and Hüllermeier, Eyke}}, booktitle = {{in Proceedings DS-2011, 14th International Conference on Discovery Science, number 6926 in LNAI}}, editor = {{Elomaa, T. and Hollmen, J. and Mannila, H.}}, pages = {{2--17}}, publisher = {{Springer}}, title = {{{Learning from label preferences}}}, year = {{2011}}, } @inproceedings{13197, author = {{Fallah Tehrani, A. and Cheng, W. and Dembczynski, K. and Hüllermeier, Eyke}}, booktitle = {{In Proceedings ECML/PKDD-2011, European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases, Athens, Greece,}}, title = {{{Learning monotone nonlinear models using the Choquet integral}}}, year = {{2011}}, } @inproceedings{13198, author = {{Hüllermeier, Eyke and Schlegel, P.}}, booktitle = {{In Proceedings ICCBR-2011, 19th International Conference on Case-Based Reasoning, number 6880 in LNAI}}, editor = {{Ram, A. and Wiratunga, N.}}, pages = {{77--91}}, publisher = {{Springer}}, title = {{{Preference-based CBR: First steps toward a methodological framework}}}, year = {{2011}}, } @inproceedings{13206, author = {{Trier, Matthias and Richter, Alexander and Mörl, Susanne and Koch, Michael}}, booktitle = {{10th International Conference on Wirtschaftsinformatik}}, editor = {{Bernstein, A and Schwabe, G}}, title = {{{Anwendungsszenarien als Werkzeug zur (V) Ermittlung des Nutzens von corporate social software}}}, year = {{2011}}, } @article{13256, author = {{Ahn, Junghyun and Borowiec, Anna and Buckley, Kevan and Cai, Di and Chmiel, Anna and Czaplicka, Agnieszka and Dąbrowski, Grzegorz and Garas, Antonios and Garcia, David and Gobron, Stéphane and Hillmann, Robert and Hołyst, Janusz and Kappas, Arvid and Küster, Dennis and Mitrovic, Marija and Paltoglou, Georgios and Pirker, Hannes and Rank, Stefan and Schweitzer, Frank and Sienkiewicz, Julian and Skowron, Marcin and Sobkowicz, Paweł and Thalmann, Daniel and Thelwall, Mike and Theunis, Mathias and Trier, Matthias and Tsankova, Elena and Weronski, Paweł}}, issn = {{1877-0509}}, journal = {{Procedia Computer Science}}, pages = {{221--222}}, title = {{{CYBEREMOTIONS – Collective Emotions in Cyberspace}}}, doi = {{10.1016/j.procs.2011.09.076}}, year = {{2011}}, } @inbook{13265, author = {{Trier, Matthias and Bobrik, Annette}}, booktitle = {{Netzwerkanalyse und Netzwerktheorie}}, isbn = {{9783531173276}}, title = {{{Dynamische Analyse von Netzwerken elektronischer Kommunikation. Kann der Zentralität getraut werden?}}}, doi = {{10.1007/978-3-531-92029-0_25}}, year = {{2011}}, }