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Autonomous Motion Conference Paper Overt visual attention for a humanoid robot Vijayakumar, S., Conradt, J., Shibata, T., Schaal, S. In IEEE International Conference on Intelligent Robots and Systems (IROS 2001), 2001, clmc
The goal of our research is to investigate the interplay between oculomotor control, visual processing, and limb control in humans and primates by exploring the computational issues of these processes with a biologically inspired artificial oculomotor system on an anthropomorphic robot. In this paper, we investigate the computational mechanisms for visual attention in such a system. Stimuli in the environment excite a dynamical neural network that implements a saliency map, i.e., a winner-take-all competition between stimuli while simultenously smoothing out noise and suppressing irrelevant inputs. In real-time, this system computes new targets for the shift of gaze, executed by the head-eye system of the robot. The redundant degrees-of- freedom of the head-eye system are resolved through a learned inverse kinematics with optimization criterion. We also address important issues how to ensure that the coordinate system of the saliency map remains correct after movement of the robot. The presented attention system is built on principled modules and generally applicable for any sensory modality.
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Physical Intelligence Conference Paper PZT actuated four-bar mechanism with two flexible links for micromechanical flying insect thorax Sitti, M. In Robotics and Automation, 2001. Proceedings 2001 ICRA. IEEE International Conference on, 4:3893-3900, 2001 BibTeX
Theory of Inhomogeneous Condensed Matter Article Polydisperse fluid in contact with a semipermeable membrane Bryk, P., Patrykiejew, A., Sokolowski, S. Molecular Physics, 99(20):1709-1717, 2001 BibTeX
Theory of Inhomogeneous Condensed Matter Article Polymer depletion interaction between two parallel repulsive walls Schlesener, F., Hanke, A., Klimpel, R., Dietrich, S. Physical Review E, 63(4):041803, 2001 DOI BibTeX
Theory of Inhomogeneous Condensed Matter Article Positron annihilation studies on the migration of deformation induced vacancies in stainless steel AISI 316 L Holzwarth, U., Barbieri, A., Hansen-Ilzhofer, S., Schaaff, P., Haaks, M. Applied Physics A-Materials Science \& Processing, 73(4):467-475, 2001 BibTeX
Autonomous Motion Conference Paper Real-time statistical learning for robotics and human augmentation Schaal, S., Vijayakumar, S., D’Souza, A., Ijspeert, A., Nakanishi, J. In International Symposium on Robotics Research, (Editors: Jarvis, R. A.;Zelinsky, A.), Lorne, Victoria, Austrialia Nov.9-12, 2001, clmc
Real-time modeling of complex nonlinear dynamic processes has become increasingly important in various areas of robotics and human augmentation. To address such problems, we have been developing special statistical learning methods that meet the demands of on-line learning, in particular the need for low computational complexity, rapid learning, and scalability to high-dimensional spaces. In this paper, we introduce a novel algorithm that possesses all the necessary properties by combining methods from probabilistic and nonparametric learning. We demonstrate the applicability of our methods for three different applications in humanoid robotics, i.e., the on-line learning of a full-body inverse dynamics model, an inverse kinematics model, and imitation learning. The latter application will also introduce a novel method to shape attractor landscapes of dynamical system by means of statis-tical learning.
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Micro, Nano, and Molecular Systems Article Reply to “Comment on ‘Phenomenological damping in optical response tensors’” Buckingham, A., Fischer, P. PHYSICAL REVIEW A, 63(4), 2001
We show that damping factors must not be incorporated in the perturbation of the ground state by a static electric field. If they are included, as in the theory of Stedman et al. {[}preceding Comment. Phys. Rev. A 63, 047801 (2001)], then there would be an electric dipole in the y direction induced in a hydrogen atom in the M-s = + 1/2 state by a static electric field in the x direction. Such a dipole is excluded by symmetry.
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Autonomous Motion Conference Paper Robust learning of arm trajectories through human demonstration Billard, A., Schaal, S. In IEEE International Conference on Intelligent Robots and Systems (IROS 2001), Piscataway, NJ: IEEE, Maui, Hawaii, Oct.29-Nov.3, 2001, clmc
We present a model, composed of hierarchy of artificial neural networks, for robot learning by demonstration. The model is implemented in a dynamic simulation of a 41 degrees of freedom humanoid for reproducing 3D human motion of the arm. Results show that the model requires few information about the desired trajectory and learns on-line the relevant features of movement. It can generalize across a small set of data to produce a qualitatively good reproduction of the demonstrated trajectory. Finally, it is shown that reproduction of the trajectory after learning is robust against perturbations.
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Theory of Inhomogeneous Condensed Matter Article Self-diffusion of 71Ge in Si-Ge Strohm, A., Voss, T., Frank, W., Raisanen, J., Dietrich, M. Physica B, 308:542-545, 2001 BibTeX
Physical Intelligence Conference Paper Survey of nanomanipulation systems Sitti, M. In Nanotechnology, 2001. IEEE-NANO 2001. Proceedings of the 2001 1st IEEE Conference on, 75-80, 2001 BibTeX
Autonomous Motion Article Synchronized robot drumming by neural oscillator Kotosaka, S., Schaal, S. Journal of the Robotics Society of Japan, 19(1):116-123, 2001, clmc
Sensory-motor integration is one of the key issues in robotics. In this paper, we propose an approach to rhythmic arm movement control that is synchronized with an external signal based on exploiting a simple neural oscillator network. Trajectory generation by the neural oscillator is a biologically inspired method that can allow us to generate a smooth and continuous trajectory. The parameter tuning of the oscillators is used to generate a synchronized movement with wide intervals. We adopted the method for the drumming task as an example task. By using this method, the robot can realize synchronized drumming with wide drumming intervals in real time. The paper also shows the experimental results of drumming by a humanoid robot.
BibTeX
Empirical Inference Article The psychometric function: I. Fitting, sampling and goodness-of-fit Wichmann, F., Hill, N. Perception and Psychophysics, 63 (8):1293-1313, 2001
The psychometric function relates an observer'sperformance to an independent variable, usually some physical quantity of a stimulus in a psychophysical task. This paper, together with its companion paper (Wichmann & Hill, 2001), describes an integrated approach to (1) fitting psychometric functions, (2) assessing the goodness of fit, and (3) providing confidence intervals for the function'sparameters and other estimates derived from them, for the purposes of hypothesis testing. The present paper deals with the first two topics, describing a constrained maximum-likelihood method of parameter estimation and developing several goodness-of-fit tests. Using Monte Carlo simulations, we deal with two specific difficulties that arise when fitting functions to psychophysical data. First, we note that human observers are prone to stimulus-independent errors (or lapses ). We show that failure to account for this can lead to serious biases in estimates of the psychometric function'sparameters and illustrate how the problem may be overcome. Second, we note that psychophysical data sets are usually rather small by the standards required by most of the commonly applied statistical tests. We demonstrate the potential errors of applying traditional X^2 methods to psychophysical data and advocate use of Monte Carlo resampling techniques that do not rely on asymptotic theory. We have made available the software to implement our methods
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Empirical Inference Article The psychometric function: II. Bootstrap-based confidence intervals and sampling Wichmann, F., Hill, N. Perception and Psychophysics, 63 (8):1314-1329, 2001 PDF BibTeX
Physical Intelligence Conference Paper Thorax Design and Wing Control for a Micromechanical Flying Insect Yan, J., Ayadhanula, S., Sitti, M., Wood, R., Fearing, R. In PROCEEDINGS OF THE ANNUAL ALLERTON CONFERENCE ON COMMUNICATION CONTROL AND COMPUTING, 39(2):952-961, 2001 BibTeX
Physical Intelligence Conference Paper Towards flapping wing control for a micromechanical flying insect Yan, J., Wood, R. J., Avadhanula, S., Sitti, M., Fearing, R. S. In Robotics and Automation, 2001. Proceedings 2001 ICRA. IEEE International Conference on, 4:3901-3908, 2001 BibTeX
Autonomous Motion Conference Paper Trajectory formation for imitation with nonlinear dynamical systems Ijspeert, A., Nakanishi, J., Schaal, S. In IEEE International Conference on Intelligent Robots and Systems (IROS 2001), 752-757, Weilea, Hawaii, Oct.29-Nov.3, 2001, clmc
This article explores a new approach to learning by imitation and trajectory formation by representing movements as mixtures of nonlinear differential equations with well-defined attractor dynamics. An observed movement is approximated by finding a best fit of the mixture model to its data by a recursive least squares regression technique. In contrast to non-autonomous movement representations like splines, the resultant movement plan remains an autonomous set of nonlinear differential equations that forms a control policy which is robust to strong external perturbations and that can be modified by additional perceptual variables. This movement policy remains the same for a given target, regardless of the initial conditions, and can easily be re-used for new targets. We evaluate the trajectory formation system (TFS) in the context of a humanoid robot simulation that is part of the Virtual Trainer (VT) project, which aims at supervising rehabilitation exercises in stroke-patients. A typical rehabilitation exercise was collected with a Sarcos Sensuit, a device to record joint angular movement from human subjects, and approximated and reproduced with our imitation techniques. Our results demonstrate that multi-joint human movements can be encoded successfully, and that this system allows robust modifications of the movement policy through external variables.
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Empirical Inference Conference Paper Unsupervised Segmentation and Classification of Mixtures of Markovian Sources Seldin, Y., Bejerano, G., Tishby, N. In The 33rd Symposium on the Interface of Computing Science and Statistics (Interface 2001 - Frontiers in Data Mining and Bioinformatics), 1-15, 33rd Symposium on the Interface of Computing Science and Statistics (Interface 2001 - Frontiers in Data Mining and Bioinformatics), 2001
We describe a novel algorithm for unsupervised segmentation of sequences into alternating Variable Memory Markov sources, first presented in [SBT01]. The algorithm is based on competitive learning between Markov models, when implemented as Prediction Suffix Trees [RST96] using the MDL principle. By applying a model clustering procedure, based on rate distortion theory combined with deterministic annealing, we obtain a hierarchical segmentation of sequences between alternating Markov sources. The method is applied successfully to unsupervised segmentation of multilingual texts into languages where it is able to infer correctly both the number of languages and the language switching points. When applied to protein sequence families (results of the [BSMT01] work), we demonstrate the method‘s ability to identify biologically meaningful sub-sequences within the proteins, which correspond to signatures of important functional sub-units called domains. Our approach to proteins classification (through the obtained signatures) is shown to have both conceptual and practical advantages over the currently used methods.
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Empirical Inference Conference Paper Unsupervised Sequence Segmentation by a Mixture of Switching Variable Memory Markov Sources Seldin, Y., Bejerano, G., Tishby, N. In In the proceeding of the 18th International Conference on Machine Learning (ICML 2001), 513-520, 18th International Conference on Machine Learning (ICML 2001), 2001
We present a novel information theoretic algorithm for unsupervised segmentation of sequences into alternating Variable Memory Markov sources. The algorithm is based on competitive learning between Markov models, when implemented as Prediction Suffix Trees (Ron et al., 1996) using the MDL principle. By applying a model clustering procedure, based on rate distortion theory combined with deterministic annealing, we obtain a hierarchical segmentation of sequences between alternating Markov sources. The algorithm seems to be self regulated and automatically avoids over segmentation. The method is applied successfully to unsupervised segmentation of multilingual texts into languages where it is able to infer correctly both the number of languages and the language switching points. When applied to protein sequence families, we demonstrate the method‘s ability to identify biologically meaningful sub-sequences within the proteins, which correspond to important functional sub-units called domains.
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Physical Intelligence Article Wing transmission for a micromechanical flying insect Yan, J., Avadhanula, S., Birch, J., Dickinson, M., Sitti, M., Su, T., Fearing, R. Journal of Micromechatronics, 1(3):221-237, Brill, 2001 BibTeX
Modern Magnetic Systems Article A full field transmission X-ray microscope as a tool for high-resolution magnetic imaging Denbeaux, G., Fischer, P., Kusinski, G., Le Gros, M., Pearson, A., Attwood, D. {IEEE Transactions on Magnetics}, 37:2764-2766, 2001 BibTeX
Modern Magnetic Systems Conference Paper AMOC studies of positronium in fine MgO powder van Waeyenberge, B., Dauwe, C., Stoll, H. In Positron Annihilation. Proceedings of the 12th International Conference on Positron Annihilation, 363/365:401-403, Materials Science Forum, Trans Tech Publications Ltd., München, 2001 BibTeX
Modern Magnetic Systems Article Ab-initio statistical mechanics for the phase diagram of NiAl including the effect of vacancies Lechermann, F., Fähnle, M. {Physica Status Solidi B-Basic Research}, 224(2):R4-R6, 2001 BibTeX
Modern Magnetic Systems Article Ab-initio statistical mechanics for the phase diagram of NiAl including the effect of vacancies Lechermann, F., Fähnle, M. {Physica Status Solidi (B)}, 224:R4-R6, 2001 BibTeX
Modern Magnetic Systems Conference Paper Atomic defects and electronic structure of B2-FeAl, CoAl and NiAl Fähnle, M., Meyer, B., Bester, G., Majer, J., Börnsen, N. In Proceedings of DIMAT 2000, the Fifth International Conference on Diffusion in Materials, 194/199:279-285, Defect and Diffusion Forum, Scitec Publications Ltd., Paris, France, 2001 BibTeX
Modern Magnetic Systems Article Atomic defects and electronic structure of B2FeAl, CoAl and NiAl Fähnle, M., Meyer, B., Bester, G., Majer, J., Börnsen, N. {Defect and Diffusion Forum}, 194-199:279-285, 2001 BibTeX
Modern Magnetic Systems Article Atomic defects in FeCo: Stabilization of the B2 structure by magnetism Neumayer, M., Fähnle, M. {Physical Review B}, 64(13), 2001 BibTeX
Modern Magnetic Systems Article Carbon nanostructures: an efficient hydrogen storage medium for fuel cells Atkinson, K., Roth, S., Hirscher, M., Grünwald, W. {Fuel Cells Bulletin}, 4(38):9-12, 2001 BibTeX
Modern Magnetic Systems Article Co(NH3)2Cl2 and Co(ND3)2Cl2: Order-Disorder Behaviour of N(H,D)3 and Antiferromagnetic Structure Leineweber, A., Jacobs, H., E\ssmann, P., Allenspach, F., Fauth, F., Fischer, P. {Zeitschrift f\"ur Anorganische und Allgemeine Chemie}, 627:2063-2069, 2001 BibTeX
Modern Magnetic Systems Article Compound formation and abrasion resistance of ion-implanted Ti6Al4V Schmidt, H., Schminke, A., Schmiedgen, M., Baretzky, B. {Acta Materialia}, 49(3):487-495, 2001 BibTeX
Modern Magnetic Systems Article Compound formation and abrasion resistance of ion-implanted Ti6Al4V Schmidt, H., Schminke, A., Schmiedgen, M., Baretzky, B. {Acta Materialia}, 49:487-495, 2001 BibTeX
Modern Magnetic Systems Conference Paper Computational micromagnetism of magnetic structures and magnetization processes in thin plantelets and small particles Kronmüller, H., Hertel, R. In Magnetic Storage Sstems Beyond 2000, 41:345-362, Nato Science Series II: Mathematics, Physics and Chemistry, Kluwer Academic Publishers, Rhodos, Greece, 2001 BibTeX
Modern Magnetic Systems Article Critical magnetic properties of disordered Cr-rich FeCr alloys Fischer, S. F., Kaul, S. N., Kronmüller, H. {Journal of Magnetism and Magnetic Materials}, 226(Sp. Iss. SI):540-541, 2001 BibTeX
Modern Magnetic Systems Article Critical magnetic properties of disordered polycrystalline Fe75Fe25 and Cr70Fe30 alloys Fischer, S. F., Kaul, S. N., Kronmüller, H. {Physical Review B}, 65, 2001 BibTeX
Modern Magnetic Systems Article Diffusion of 23Na and 35K in the eutectic melt Na0.32K0.69 Feinauer, A., Majer, G. {Physical Review B}, 64, 2001 BibTeX
Modern Magnetic Systems Article Diffusion of hydrogen in heterogeneous systems Herrmann, A., Schimmele, L., Mössinger, J., Hirscher, M., Kronmüller, H. {Applied Physics A-Materials Science \& Processing}, 72(2):197-208, 2001 BibTeX
Modern Magnetic Systems Article Effect of Ga substitution on the magnetocrystalline anisotropy of arc-melted Sm2Co17-xGax (x\textequals5,6) compounds Liang, B., Kleinschroth, I., Kronmüller, H. {Journal of Applied Physics}, 89(1):488-491, 2001 BibTeX
Modern Magnetic Systems Article Element-specific imaging of magnetic domains at 25 nm spatial Resolution using soft X-ray microscopy Fischer, P., Eimüller, T., Schütz, G., Denbeaux, G., Pearson, A., Johnson, L., Attwood, D., Tsunashima, S., Kumazawa, M., Takagi, N., Köhler, M., Bayreuther, G. {Review of Scientific Instruments}, 72:2322-2324, 2001 BibTeX
Modern Magnetic Systems Conference Paper Enhancement of the critical current density of YBa2Cu3O7-8-films by substracte irradiation Leonhardt, S., Albrecht, J., Warthmann, R., Kronmüller, H. In High-Tc Superconductors and Related Applications: Materials Science, Fundamental Properties, and Some Future Electronic Applications. Proceedings of the NATO Advanced Study Institute, 86:529-534, NATO Science Series 3. High Technology, Kluwer Academic Publishers, Albena, Bulgaria, 2001 BibTeX
Modern Magnetic Systems Article Faceting of \sum3 and \sum9 grain boundaries in copper Straumal, B. B., Polyakov, S. A., Bischoff, E., Gust, W., Mittemeijer, E. J. {Interface Science}, 9(3-4):287-292, 2001 BibTeX
Modern Magnetic Systems Article Fast ab initio methods for the calculation of adiabatic spin wave spectra in complex systems Grotheer, O., Ederer, C., Fähnle, M. {Physical Review B}, 63(10):100401-100401, 2001 BibTeX
Modern Magnetic Systems Conference Paper First proof of slow trapping of positronium in polymers by an Age-Momentum-Correlation (AMOC) experiment Dauwe, C., Balcaen, N., van Waeyenberge, B., van Petegem, S., Stoll, H. In Positron Annihilation. Proceedings of the 12th International Conference on Positron Annihilation, 363/365:254-256, Materials Science Forum, Trans Tech Publications Ltd., München, 2001 BibTeX
Modern Magnetic Systems Conference Paper Flux-line pinning in low-angle grain boundaries. Albrecht, J., Leonhardt, S., Kronmüller, H. In Proceedings 10th International Workshop on Critical Currents (IWCC 2001), 41-43, Göttingen, Germany, 2001 BibTeX
Modern Magnetic Systems Article Formation and structure of highly over-stoichiometric LaNi5+x (x\textasciitilde1) alloys obtained by manifold non-equilibrium methods Cuevas, F., Latroche, M., Hirscher, M., Percheron-Guegan, A. {Journal of Alloys and Compounds}, 323:4-7, 2001 BibTeX
Modern Magnetic Systems Conference Paper From the electronic structure to the macroscopic behaviour: a multi-scale analysis of plasticity in intermetallic compounds Fähnle, M., Kohlhammer, S., Bester, G. In Influences of Interface and Dislocation Behavior on Microstructure Evolution, 652:Y.4.5.1-Y.4.5.12, Materials Research Society Symposium Proceedings, MRS, Boston, Mass., 2001 BibTeX
Modern Magnetic Systems Conference Paper From the electronic structure to the macroscopiy behavior: A multi-scale analysis of plasticity in intermetallic compounds Fähnle, M., Kohlhammer, S., Bester, G. In Influences of Interface and Dislocation Behavior on Microstructure Evolution, 652:Y4.5.1.-Y4.5.12, Materials Research Society Symposium Proceedings, MRS, Boston, Mass., USA, 2001 BibTeX
Modern Magnetic Systems Article Generation and application of ultra-high-intensity magnetic field gradient pulses for NMR spectroscopy Galvosas, P., Stallmach, F., Seiffert, G., Karger, J., Kaess, U., Majer, G. {Journal of Magnetic Resonance}, 151(2):260-268, 2001 BibTeX
Modern Magnetic Systems Article Grain boundary grooving as an indicator of grain boundary phase transformations Schölhammer, J., Baretzky, B., Gust, W., Mittemeijer, E., Straumal, B. {Interface Science}, 9(1-2):43-53, 2001 BibTeX
Modern Magnetic Systems Article Grain boundary phase transition in the Cu-Bi system Straumal, B. B., Prokofyev, S. I., Chang, L., Sluchanko, N. E., Baretzky, B., Gust, W., Mittemeijer, E. J. {Diffusion and Defect Forum}, 194-199:1343-1348, 2001 BibTeX
Modern Magnetic Systems Article Hardness-depth profile of a carbon-implanted Ti-6Al-4V alloy and its relation to composition and microstructure Kunert, M., Kienzle, O., Baretzky, B., Baker, S. P., Mittemeijer, E. J. {Journal of Materials Research}, 16(8):2321-2335, 2001 BibTeX
Modern Magnetic Systems Article Hardness-depth profiling on nanometer scale Kunert, M., Baretzky, B., Baker, S. P., Mittemeijer, E. J. {Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science}, 32(5):1201-1209, 2001 BibTeX