@article{11825, abstract = {{In this paper, we propose an enhanced error concealment strategy at the server side of a distributed speech recognition (DSR) system, which is fully compatible with the existing DSR standard. It is based on a Bayesian approach, where the a posteriori probability density of the error-free feature vector is computed, given all received feature vectors which are possibly corrupted by transmission errors. Rather than computing a point estimate, such as the MMSE estimate, and plugging it into the Bayesian decision rule, we employ uncertainty decoding, which results in an integration over the uncertainty in the feature domain. In a typical scenario the communication between the thin client, often a mobile device, and the recognition server spreads across heterogeneous networks. Both bit errors on circuit-switched links and lost data packets on IP connections are mitigated by our approach in a unified manner. The experiments reveal improved robustness both for small- and large-vocabulary recognition tasks.}}, author = {{Ion, Valentin and Haeb-Umbach, Reinhold}}, journal = {{Speech Communication}}, keywords = {{Channel error robustness, Distributed speech recognition, Soft features, Uncertainty decoding}}, number = {{11}}, pages = {{1435--1446}}, title = {{{Uncertainty decoding for distributed speech recognition over error-prone networks}}}, doi = {{10.1016/j.specom.2006.03.007}}, volume = {{48}}, year = {{2006}}, } @inproceedings{11826, abstract = {{The accuracy of distributed speech recognition has been shown to be very sensitive to errors occurring during transmission. One reason for this is that the classifier, usually trained under error free conditions, is unable to cope with the mismatch between an error free and error prone channel. In this paper we present a novel decision rule for classification which is able to account for channel errors. To achieve this, the classical Bayesian speech recognition approach has been reformulated for the server side, where the observation is known only to the extent, as is given by its a posteriori density function. We present a method to estimate the a posteriori density which is based on a Markov model of the source, which captures correlations of both static and dynamic features. A practical implementation is given, accompanied by experimental results for distributed speech recognition over an IP-network.}}, author = {{Ion, Valentin and Haeb-Umbach, Reinhold}}, booktitle = {{Interspeech 2006}}, title = {{{Improved Source Modeling and Predictive Classification for Channel Robust Speech Recognition}}}, year = {{2006}}, } @inproceedings{11884, abstract = {{In this paper we present the design of a particle filter for post filtering instantaneous positioning estimates of GSM mobile terminals. The instantaneous estimates are obtained by comparing signal power levels, which are reported by the mobile terminal to the base station, with a database of predictions using a novel statistically motivated similarity measure. Unlike a simple Euclidian distance measure, the proposed scheme incorporates inherent information about signal power level measurements requested by the serving base station but not reported by the mobile terminal. Furthermore, we show how the Monte Carlo method of particle filtering helps to obtain better position estimates and, surprisingly, also helps to reduce the computational complexity. Results are presented for real field data.}}, author = {{Peschke, Sven and Haeb-Umbach, Reinhold}}, booktitle = {{European Navigation Conference \& Exhibition (ENC 2006)}}, title = {{{A Probabilistic Similarity Measure and a Non-Linear Post-Filter for Mobile Phone Positioning using GSM Signal Power Measurements}}}, year = {{2006}}, } @inproceedings{11885, abstract = {{In this paper we present a novel and statistically motivated similarity measure for database assisted positioning of GSM mobile terminals by evaluating signal power level reports which are transmitted regulary. Unlike a simple Euclidian distance measure, the proposed scheme incorporates inherent information about signal power level measurements requested by the serving base station but not reported by the mobile terminal. Furthermore we show how the Monte Carlo method of nonlinear post filtering using particle filtering helps to obtain better position estimates and surprisingly also helps to reduce the computational complexity. Results are presented for real field data.}}, author = {{Peschke, Sven and Haeb-Umbach, Reinhold}}, booktitle = {{3rd Workshop on Positioning Navigation and Communication (WPNC 2006)}}, title = {{{Particle Filtering of Database assisted Positioning Estimates using a novel Similarity Measure for GSM Signal Power Level Measurements}}}, year = {{2006}}, } @inproceedings{11928, abstract = {{Broadband adaptive beamformers, which use a narrowband SNR-maximization optimization criterion for noise reduction, typically cause distortions of the desired speech signal at the beamformer output. In this paper two methods are investigated to control the speech distortion by comparing the eigenvector beamformer with a maximum likelihood beamformer: One is an analytic solution for the ideal case of absence of reverberation and the other one is a statistically motivated approach. We use the recently introduced gradient-ascent algorithm for adaptive principal eigenvector beamforming and then normalize the filter coefficients by the proposed distortion control methods. Experimental results in terms of the achievable SNR gain and a perceptual speech quality measure are given for the normalized eigenvector beamformer and are compared to standard beamforming methods.}}, author = {{Warsitz, Ernst and Haeb-Umbach, Reinhold}}, booktitle = {{32. Deutsche Jahrestagung fuer Akustik (DAGA 2006)}}, title = {{{Mehrkanalige Sprachsignalverarbeitung durch adaptives Eigenbeamforming fuer Freisprecheinrichtungen im Kraftfahrzeug}}}, year = {{2006}}, } @inproceedings{11929, abstract = {{Broadband adaptive beamformers, which use a narrowband SNR-maximization optimization criterion for noise reduction, typically cause distortions of the desired speech signal at the beamformer output. In this paper two methodsare investigated to control the speech distortion by comparing the eigenvector beamformer with a maximum likelihood beamformer: One is an analytic solution for the ideal case of absence of reverberation and the other one is a statistically motivated approach. We use the recently introduced gradient-ascent algorithm for adaptive principal eigenvector beamforming and then normalize the filter coefficient s by the proposed distortion control methods. Experimental results in terms of the achievable SNR gain and a perceptual speech quality measure are given for the normalized eigenvector beamformer and are compared to standard beamforming methods.}}, author = {{Warsitz, Ernst and Haeb-Umbach, Reinhold}}, booktitle = {{International Workshop on Acoustic Echo and Noise Control (IWAENC 2006)}}, title = {{{Controlling Speech Distortion in Adaptive Frequency-Domain Principal Eigenvector Beamforming}}}, year = {{2006}}, } @inproceedings{11942, abstract = {{Es wird ein marginalisiertes Partikelfilter beschrieben, das zur einkanaligen Sprachsignalverbesserung mit einem nichtlinearen dynamischen Zustandsmodell eingesetzt werden soll. Das System besteht aus einem Partikelfilter zum Tracking von LSP-Parametern und einem Kalman-Filter fuer jedes Partikel, das zur Sprachsignalverbesserung verwendet wird. In unserem Ansatz wird angenommen, dass die Parameter in kurzen Sprachsignalbloecken konstant sind, waehrend das Sprachsignal sich mit jedem Abtastwert aendert. Bei weissem Rauschen werden aehnliche SNR-Gewinne wie mit einem Kalman-EM-iterative Algorithmus erzielt, waehrend das Hintergrundrauschen und die Log-spektrale Distanz etwas geringer sind. Mit einem erweiterten Zustandsmodell wurden auch Untersuchungen fuer farbiges Rauschen durchgefuehrt.}}, author = {{Windmann, Stefan and Haeb-Umbach, Reinhold}}, booktitle = {{7. ITG-Fachtagung Sprachkommunikation}}, title = {{{Einkanalige Sprachsignalverbesserung mit Hilfe eines marginalisierten Partikelfilters}}}, year = {{2006}}, } @inproceedings{11943, abstract = {{A marginalized particle filter is proposed for performing single channel speech enhancement with a non-linear dynamic state model. The system consists of a particle filter for tracking line spectral pair (LSP) parameters and a Kalman filter per particle for speech enhancement. The state model for the LSPs has been learnt on clean speech training data. In our approach parameters and speech samples are processed at different time scales by assuming the parameters to be constant for small blocks of data. Further enhancement is obtained by an iteration which can be applied on these small blocks. The experiments show that similar SNR gains are obtained as with the Kalman-LM-iterative algorithm. However better values of the noise level and the log-spectral distance are achieved}}, author = {{Windmann, Stefan and Haeb-Umbach, Reinhold}}, booktitle = {{IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP 2006)}}, keywords = {{clean speech training data, iterative methods, iterative speech enhancement, Kalman filter, Kalman filters, Kalman-LM-iterative algorithm, line spectral pair parameters, log-spectral distance, marginalized particle filter, noise level, nonlinear dynamic state speech model, particle filtering (numerical methods), single channel speech enhancement, SNR gains, speech enhancement, speech samples}}, pages = {{I}}, title = {{{Iterative Speech Enhancement using a Non-Linear Dynamic State Model of Speech and its Parameters}}}, doi = {{10.1109/ICASSP.2006.1660058}}, volume = {{1}}, year = {{2006}}, } @inbook{12907, author = {{Beutner, Marc and Schaumann, U and Twardy, M}}, booktitle = {{Berufs- und wirtschaftspädagogische Grundlagenforschung. Lehr-Lern-Prozesse und Kompetenzdiagnostik. Festschrift für Klaus Beck}}, editor = {{Minnameier, G and Wuttke, E}}, pages = {{289 -- 303}}, publisher = {{Peter Lang Verlag}}, title = {{{Neue Beruflichkeit und damit verbundene Anforderungen auf Basis des Kompetenzgedankens in der beruflichen Bildung}}}, year = {{2006}}, } @inproceedings{15347, abstract = {{Um das Schwingungsverhalten eines mit Flüssigkeit gefüllten zylindrischen Stahltanks mit beliebiger Füllhöhe zu modellieren, werden Ansätze aus der Schalentheorie genutzt. Verschiedene analytische Modelle und Vereinfachungen werden gegenübergestellt und für den leeren sowie komplett gefüllten Zylinder gelöst. Zudem wird ein semianalytisches Modell für den teilweise gefüllten Zylinder entworfen. Simulationsergebnisse aus FEM-Simulationen sowie Ergebnisse aus Testmessungen werden den Modellwerten gegenübergestellt.}}, author = {{Kehl, Romina and Rautenberg, Jens and Henning, Bernd}}, location = {{Braunschweig}}, pages = {{407--408}}, title = {{{Schwingungsverhalten eines flüssigkeitsgefüllten Tanks}}}, year = {{2006}}, } @inproceedings{15348, abstract = {{In spite of the outstanding importance of neuronavigational techniques the neurosurgeon has still highly to rely on his visual as well as tactile sense and his experience in distinguishing tumor tissue from intact brain parenchyma. All the more - as neuronavigation is based on preoperative imaging scans - considerable brain shift may occur during surgery and that will lead to erroneous results. Furthermore the surgeon loses his tactile sense during endoscopic surgery. Therefore control of tissue manipulation is limited today to the fiberoptic image techniques, possibly ensured by neuronavigational supervision or haptic feedback systems. In robotic guided surgery the missing tactile sensing will be particularly crucial. The human sense of touch is a highly complex sensory perception comprising epicritical and propiozeptive information processing. The development of a tool for intraoperative tactile perception will be a highly challenging task to improve the safety during surgery. Different sensor concepts (elasticity probe and resonant piezoelectric sensor) have been set up and adapted to distinguish elasticity differences in soft tissue mimicking gel phantoms. The elasticity probe is based on two leaf springs of different bending stiffness. The two tips of the beams act both on the material to be tested. The two deflections measured by strain gauges are processed in a mathematical model calculating the phantoms' stiffness. In contrast to this differential sensing concept the piezoelectric sensor, which is driven at its resonance, measures stiffness and damping of the phantoms by evaluating frequency or phase shift and amplitude change. Gelatine gels of different concentrations (5{\%}, 10{\%}, 20{\%} of gelatine) have been used for a characterization of sensor elements and their sensitivity to elasticity distinctions. Using the hand-guided elasticity probe the determination of gel elasticity is performed with high reliability. By constant mechanical load the piezoelectric sensor also presents a proportional dependency of tissue elasticity.}}, author = {{Kehl, Romina and Stroop, Ralf and Oliva Uribe, David and Hemsel, Tobias and Henning, Bernd}}, location = {{Hannover}}, title = {{{Tactile sensors for determination of elastic properties of brain tissue mimicking phantoms}}}, year = {{2006}}, } @inproceedings{15349, abstract = {{Die kontinuierliche und zuverlässige Konzentrationsmessung in Flüssigkeiten ob zur Dosierung oder Prozessverfolgung stellt auch heute noch eine große messtechnische Herausforderung dar. Akustische Sensorsysteme sind für diese Messaufgabe insbesondere unter industriellen Einsatzbedingungen prädestiniert. Es gibt eine Vielzahl verschiedener sorgfältig entworfener Ultraschallsensoren, die diese Aufgabe durch Bestimmung der Schallgeschwindigkeit und der akustischen Impedanz lösen. Sie basieren meist auf senkrechten Durchgängen des Schalls durch Grenzschichten, was sie sehr empfindlich gegenüber Ablagerungen macht. Dieser Beitrag liefert einen neuen Ansatz, indem die gesamte Oberfläche des Messraumes als akustischer Wellenleiter gestaltet und genutzt wird. Es hat sich gezeigt, dass sich durch Ausnutzen verschiedener Simulationswerkzeuge die Hauptkomponenten eines Empfangssignals berechnen lassen, die eindeutig den verschiedenen modalen Anteilen zugeordnet werden können. Damit ist es möglich, allein aus dem Empfangssignal eines herkömmlichen Ultraschallwandlers auf die modalen Anteilsfaktoren zu schließen. Mit Hilfe dieser Koeffizienten und eines Modells des akustischen Wellenleiters lässt sich ein Gleichungssystem aufstellen, das den Zusammenhang zwischen Dissipation in der Flüssigkeit sowie der durch Wellenleitergeometrie und Impedanzverhältnisse bedingten Signaldämpfung und den Amplituden der modalen Anteilsfaktoren beschreibt.}}, author = {{Rautenberg, Jens and Henning, Bernd}}, isbn = {{978-3-8322-5419-3}}, location = {{Bayreuth}}, pages = {{55--73}}, title = {{{Messung der akustischen Impedanz einer Flüssigkeit in einem akustischen Wellenleiter}}}, year = {{2006}}, } @inproceedings{15350, abstract = {{In many different ultrasound applications mirrors are often used to deflect ultrasonic waves. The dimensions of the mirror and the applied materials have an essential influence on the output signal characteristics and the obtained measuring quantities. The extension of mirror geometry is not necessarily associated with a higher reflection coefficient. This can be explained with the aid of coincidence condition. A second criterion aims at the avoidance of the mirror resonance. This two conditions lead to an optimal dimensioning of mirror geometry with given material properties and operation mode, as exemplified for a rectangular mirror.}}, author = {{Unverzagt, Carsten and Rautenberg, Jens and Kehl, Romina and Henning, Bernd}}, booktitle = {{2006 IEEE International Ultrasonics Symposium}}, pages = {{1390--1393}}, title = {{{Optimization of ultrasound reflecting mirrors}}}, year = {{2006}}, } @inproceedings{15351, abstract = {{Today's automotive headlights are built with transparent cover lenses. Therefore condensation of water leads to a visible optical defect. This paper presents a new approach for determination of the droplet size using colour phenomena in totally reflected light. It is based on a model of the generation of colour patterns by interference of several rays of light each multiple totally reflected inside condensed droplets. The droplet size may be determined by the colour if the contact angle is known. Measurement of both droplet size and colour all}}, author = {{Wetzlar, Dietmar and Henning, Bernd and Nolte, Sascha and Klahold, Jens}}, isbn = {{978-3-9810993-0-0}}, location = {{Nürenberg}}, title = {{{Investigation of colour phenomena in condensed water droplets}}}, year = {{2006}}, } @article{15357, author = {{Henning, Bernd and Rautenberg, Jens}}, journal = {{Ultrasonics}}, number = {{44}}, pages = {{e1395--e1399}}, title = {{{Process monitoring using ultrasonic sensor systems}}}, year = {{2006}}, } @article{15694, author = {{Magenheim, Johannes and Schulte, Carsten}}, journal = {{EAIT}}, number = {{3-4}}, pages = {{319--339}}, title = {{{Social, ethical and technical issues in informatics - An integrated approach}}}, volume = {{11}}, year = {{2006}}, } @article{15695, author = {{Lister, Raymond and Berglund, Anders and Clear, Tony and Bergin, Joe and Garvin-Doxas, Kathy and Hanks, Brian and E. Hitchner, Lewis and Luxton-Reilly, Andrew and Sanders, Kate and Schulte, Carsten and L. Whalley, Jacqueline}}, journal = {{SIGCSE Bulletin}}, number = {{4}}, pages = {{146--165}}, title = {{{Research perspectives on the objects-early debate}}}, volume = {{38}}, year = {{2006}}, } @inproceedings{15696, author = {{Schulte, Carsten and Bennedsen, Jens}}, booktitle = {{ICER}}, pages = {{17--28}}, publisher = {{ACM}}, title = {{{What do teachers teach in introductory programming?}}}, year = {{2006}}, } @inproceedings{15697, author = {{Bennedsen, Jens and Schulte, Carsten}}, booktitle = {{PPIG}}, pages = {{1}}, publisher = {{Psychology of Programming Interest Group}}, title = {{{A Competence Model for Object-Interaction in Introductory Programming}}}, year = {{2006}}, } @inproceedings{15698, author = {{Schulte, Carsten and Thomas, Marco}}, booktitle = {{HDI}}, pages = {{77--88}}, publisher = {{GI}}, title = {{{Gestaltung von Informatikseminaren unter Einsatz von Videokonferenzen}}}, volume = {{P-100}}, year = {{2006}}, }