@article{41695, author = {{Fuchs, Christian and Horak, Eva}}, journal = {{Masaryk University Journal of Law and Technology}}, number = {{2}}, pages = {{11--32}}, title = {{{Informational Capitalism and the Digital Divide in Africa. (Proceedings of the Conference “Cyberspace 2006“, 24.11-25.11.2006, Masaryk University, Brno, Czech Republic)}}}, volume = {{1}}, year = {{2007}}, } @article{44114, abstract = {{Optical 2D Fourier transform spectroscopy (2DFTS) provides insight into the many-body interactions in direct gap semiconductors by separating the contributions to the coherent nonlinear optical response. We demonstrate these features of optical 2DFTS by studying the heavy-hole and light-hole excitonic resonances in a gallium arsenide quantum well at low temperature. Varying the polarization of the incident beams exploits selection rules to achieve further separation. Calculations using a full many-body theory agree well with experimental results and unambiguously demonstrate the dominance of many-body physics.}}, author = {{Meier, Torsten and Zhang, Tianhao and Kuznetsova, Irina and Li, Xiaoqin and Mirin, R. P. and Thomas, Peter and Cundiff, S.T.}}, journal = {{Proceedings of the National Academy of Sciences}}, number = {{36}}, pages = {{14227--14232}}, title = {{{Multidimensional ultrafast spectroscopy special feature: polarization-dependent optical 2d fourier transform spectroscopy of semiconductors}}}, doi = {{10.1073/pnas.0701273104}}, volume = {{104}}, year = {{2007}}, } @book{23486, author = {{Meier, Torsten and Thomas, Peter and Koch, Stephan W.}}, isbn = {{9783540325543}}, title = {{{Coherent Semiconductor Optics}}}, doi = {{10.1007/978-3-540-32555-0}}, volume = {{1}}, year = {{2007}}, } @techreport{42731, author = {{Hofkirchner, Wolfgang and Fuchs, Christian and Raffl, Celina and Schafranek, Matthias and Sandoval, Marisol and Bichler, Robert}}, issn = {{1990-8563}}, publisher = {{ICT&S Center}}, title = {{{ICTs and society: The Salzburg Approach: Towards a Theory for, about, and by Means of the Information Society. ICT&S Research Paper No. 3}}}, year = {{2007}}, } @article{43264, abstract = {{On the basis of a microscopic theory, the signatures of many-particle correlations in Two-Dimensional Fourier-Transform Spectra (2D-FTS) of semiconductor nanostructures are identified and compared to experimental data. Spectra in the photon energy range of the heavy-hole and light-hole excitonic resonances show characteristic features due to correlations, which depend on the relative polarization directions of the excitation pulses.}}, author = {{Kuznetsova, I. and Thomas, P. and Meier, Torsten and Zhang, T. and Li, X. and Mirin, R.P. and Cundiff , S. T.}}, journal = {{Solid state communications}}, number = {{3}}, pages = {{154--158}}, publisher = {{Pergamon}}, title = {{{Signatures of Many-Particle Correlations in Two-Dimensional Fourier-Transform Spectra of Semiconductor Nanostructures}}}, doi = {{10.1016/j.ssc.2007.02.010}}, volume = {{142}}, year = {{2007}}, } @inproceedings{2111, author = {{Kothapalli, Kishore and Scheideler, Christian and Onus, Melih and Schindelhauer, Christian}}, booktitle = {{IPDPS}}, title = {{{Distributed coloring in O/spl tilde/(/spl radic/(log n)) bit rounds}}}, year = {{2006}}, } @inproceedings{2112, author = {{Awerbuch, Baruch and Scheideler, Christian}}, booktitle = {{OPODIS}}, pages = {{275----289}}, title = {{{Robust Random Number Generation for Peer-to-Peer Systems}}}, year = {{2006}}, } @inproceedings{2113, author = {{Awerbuch, Baruch and Scheideler, Christian}}, booktitle = {{SPAA}}, pages = {{318----327}}, title = {{{Towards a scalable and robust DHT}}}, year = {{2006}}, } @inbook{18601, author = {{Friedrich, Christoph and Schindlmayr, Arno}}, booktitle = {{Computational Condensed Matter Physics}}, editor = {{Blügel, Stefan and Gompper, Gerhard and Koch, Erik and Müller-Krumbhaar, Heiner and Spatschek, Robert and Winkler, Roland G.}}, isbn = {{3-89336-430-7}}, issn = {{1433-5506}}, location = {{Jülich}}, pages = {{A5.1--A5.21}}, publisher = {{Forschungszentrum Jülich}}, title = {{{Many-body perturbation theory: The GW approximation}}}, volume = {{32}}, year = {{2006}}, } @inbook{18603, author = {{Schindlmayr, Arno}}, booktitle = {{Computational Condensed Matter Physics}}, editor = {{Blügel, Stefan and Gompper, Gerhard and Koch, Erik and Müller-Krumbhaar, Heiner and Spatschek, Robert and Winkler, Roland G.}}, isbn = {{3-89336-430-7}}, issn = {{1433-5506}}, location = {{Jülich}}, pages = {{A4.1--A4.19}}, publisher = {{Forschungszentrum Jülich}}, title = {{{Time-dependent density-functional theory}}}, volume = {{32}}, year = {{2006}}, } @inbook{18606, abstract = {{In this lecture we present many-body perturbation theory as a method to determine quasiparticle excitations in solids, especially electronic band structures, accurately from first principles. The main ingredient is the electronic self-energy that, in principle, contains all many-body exchange and correlation effects beyond the Hartree potential. As its exact mathematical expression is unknown, approximations must be used in practical calculations. The approximation is obtained using a systematic algebraic approach on the basis of Green function techniques. It constitutes an expansion of the self-energy up to linear order in the screened Coulomb potential, which describes the interaction between the quasiparticles and includes dynamic screening through the creation of exchange-correlation holes around the bare particles. The implementation of the approximation relies on a perturbative treatment starting from density functional theory. Besides a detailed mathematical discussion we focus on the underlying physical concepts and show some illustrative applications.}}, author = {{Friedrich, Christoph and Schindlmayr, Arno}}, booktitle = {{Computational Nanoscience: Do It Yourself!}}, editor = {{Grotendorst, Johannes and Blügel, Stefan and Marx, Dominik}}, isbn = {{3-00-017350-1}}, location = {{Jülich}}, pages = {{335--355}}, publisher = {{John von Neumann Institute for Computing}}, title = {{{Many-body perturbation theory: The GW approximation}}}, volume = {{31}}, year = {{2006}}, } @inproceedings{2213, author = {{Scheideler, Christian}}, booktitle = {{6th International HNI Symposium on New Trends in Parallel and Distributed Computing}}, title = {{{Towards a paradigm for robust distributed algorithms and data structures}}}, year = {{2006}}, } @article{4243, abstract = {{We investigate the optical properties of a Coulomb-coupled double-quantum dot system excited by coherent light pulses. Basic effects of Coulomb coupling regarding linear and nonlinear optical processes are discussed. By numerically solving the Heisenberg equation of motion we are able to present the temporal evolution of the system’s density matrix for a wide range of coupling parameters. The two main coupling effects in dipole approximation, biexcitonic shift and Förster energy transfer, are investigated and their qualitative and quantitative influence on absorption spectra, Rabi oscillations, and single- and two-pulse excitation is discussed. We present simulated differential transmission spectra to allow for comparison with recent experimental studies.}}, author = {{Danckwerts, J. and Ahn, K. J. and Förstner, Jens and Knorr, A.}}, issn = {{1098-0121}}, journal = {{Physical Review B}}, keywords = {{tet_topic_qd}}, number = {{16}}, pages = {{165318--165318--18}}, publisher = {{American Physical Society (APS)}}, title = {{{Theory of ultrafast nonlinear optics of Coulomb-coupled semiconductor quantum dots: Rabi oscillations and pump-probe spectra}}}, doi = {{10.1103/physrevb.73.165318}}, volume = {{73}}, year = {{2006}}, } @inproceedings{5659, abstract = {{Spam e-mails have become a serious technological and economic problem. So far we have been reasonably able to resist spam e-mails and use the Internet for regular communication by deploying complementary anti-spam approaches. However, if we are to avert the danger of losing the Internet email service as a valuable, free, and worldwide medium of open communication, anti-spam activities should be performed more systematically than is done in current, mainly heuristic, anti-spam approaches. A formal framework within which the modes of spam delivery, anti-spam approaches, and their effectiveness can be investigated, may encourage a shift in methodology and pave the way for new, holistic anti-spam approaches. This paper presents a model of the Internet e-mail infrastructure as a directed graph and a deterministic finite automaton, and draws on automata theory to formally derive the modes of spam delivery possible. Finally the effectiveness of anti-spam approaches in terms of coverage of spamming modes is assessed.}}, author = {{Schryen, Guido}}, booktitle = {{39th Annual Hawaii International Conference on System Sciences}}, title = {{{A formal approach towards assessing the effectiveness of anti-spam procedures}}}, year = {{2006}}, } @inproceedings{11823, abstract = {{In this study we evaluate transmission error compensation techniques for distributed speech recognition systems based on modification of the speech decoder. The candidates are marginalization, weighted Viterbi and our recently proposed soft-feature uncertainty decoding. For the latter, it is shown how the Bayesian speech recognition approach must be reformulated for recognition at the server side. The resulting predictive classifier is able to take account of the transmission errors by changing the contribution of the affected speech features to the acoustic score. The comparison of the experimental results has proven the superiority of our approach.}}, author = {{Ion, Valentin and Haeb-Umbach, Reinhold}}, booktitle = {{7. ITG-Fachtagung Sprachkommunikation}}, title = {{{Comparison of Decoder-based Transmission Error Compensation Techniques for Distributed Speech Recognition}}}, year = {{2006}}, } @inproceedings{11824, abstract = {{Soft-feature based speech recognition, which is an example of uncertainty decoding, has been proven to be a robust error mitigation method for distributed speech recognition over wireless channels exhibiting bit errors. In this paper we extend this concept to packet-oriented transmissions. The a posteriori probability density function of the lost feature vector, given the closest received neighbours, is computed. In the experiments, the nearest frame repetition, which is shown to be equivalent to the MAP estimate, outperforms the MMSE estimate for long bursts. Taking the variance into account at the speech recognition stage results in superior performance compared to classical schemes using point estimates. A computationally and memory efficient implementation of the proposed packet loss compensation scheme based on table lookup is presented}}, author = {{Ion, Valentin and Haeb-Umbach, Reinhold}}, booktitle = {{IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP 2006)}}, keywords = {{distributed speech recognition, least mean squares methods, MAP estimate, maximum likelihood estimation, MMSE estimate, packet loss compensation scheme, packet switched communication, posteriori probability density function, robust error mitigation method, soft-features, speech recognition, table lookup, voice communication, wireless channels}}, pages = {{I}}, title = {{{An Inexpensive Packet Loss Compensation Scheme for Distributed Speech Recognition Based on Soft-Features}}}, doi = {{10.1109/ICASSP.2006.1659984}}, volume = {{1}}, year = {{2006}}, } @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}}, }