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2004


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Flusslinienverankerung in Hochtemperatursupraleitern auf nanostrukturierten Substraten

Brück, S.

Universität Stuttgart, Stuttgart, 2004 (mastersthesis)

mms

[BibTex]

2004


[BibTex]


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Ionenstreuung mit Monolagen-Tiefenauflösung

Olliges, S.

Universität Stuttgart, Stuttgart, 2004 (mastersthesis)

mms

[BibTex]

[BibTex]


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First-principles study of the interplay between magnetism and phase equilibria in Fe-Co systems

Diaz-Ortiz, A., Drautz, R., Fähnle, M., Dosch, H.

{Journal of Magnetism and Magnetic Materials}, 272-276, pages: 780-782, 2004 (article)

mms

[BibTex]

[BibTex]


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Magnetic field optimization of permanent magnet unulators for arbitrary polarization

Bahrdt, J., Frentrup, W., Gaupp, A., Scheer, M., Englisch, U.

{Nuclear Instruments and Methods in Physics Research A}, 516, pages: 575-585, 2004 (article)

mms

[BibTex]

[BibTex]


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High-resolution imaging of fast magnetization dynamics in magnetic nanostructures

Stoll, H., Puzic, A., Van Waeyenberge, B., Fischer, P., Raabe, J., Buess, M., Haug, T., Höllinger, R., Back, C., Weiss, D., Denbeaux, G.

{Applied Physics Letters}, 84, pages: 3328-3330, 2004 (article)

mms

[BibTex]

[BibTex]


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Comparison of low-temperature magnetic relaxations in two systems GdAl2Dx (C15 Laves phase) and Fe3O4 (Inverse spinel)

Walz, F., Reule, H., Hirscher, M., Kronmüller, H.

{Physica Status Solidi B}, 241(2):389-400, 2004 (article)

mms

[BibTex]

[BibTex]


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General relations between many-body potentials and cluster expansions in multi-component systems

Drautz, R., Fähnle, M., Sanchez, J.M.

{Journal of Physics: Condensed Matter}, 16, pages: 3843-3852, 2004 (article)

mms

[BibTex]

[BibTex]


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Counting individual atom layers in graphite - high-resolution RBS experiments on HOPG (highly ordered pyrolytic graphite)

Srivastava, S. K., Plachke, D., Szökefalvi-Nagy, A., Major, J., Carstanjen, H. D.

{Nuclear Instruments and Methods B}, 219-220, pages: 364-368, 2004 (article)

Abstract
{The paper reports about recent experiments on HOPG (highly oriented pyrolytic graphite) by high-resolution RBS (Rutherford backscattering spectroscopy). By using an ion beam of 1 MeV N+ up to 7 individual monolayers could be identified in the RBS spectrum from such a sample. This is about twice as much as observed by other groups up to now. Since close to the surface the RBS peaks from the individual carbon layers are well separated, various quantities important for the ion-solid interaction can be determined with high precision, such as the stopping power of 1 MeV N ions in graphite and their energy straggling. Close to the surface the RBS peaks are asymmetric which is well explained in the framework of the Landau theory of energy straggling.}

mms

[BibTex]

[BibTex]


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Feedback error learning and nonlinear adaptive control

Nakanishi, J., Schaal, S.

Neural Networks, 17(10):1453-1465, 2004, clmc (article)

Abstract
In this paper, we present our theoretical investigations of the technique of feedback error learning (FEL) from the viewpoint of adaptive control. We first discuss the relationship between FEL and nonlinear adaptive control with adaptive feedback linearization, and show that FEL can be interpreted as a form of nonlinear adaptive control. Second, we present a Lyapunov analysis suggesting that the condition of strictly positive realness (SPR) associated with the tracking error dynamics is a sufficient condition for asymptotic stability of the closed-loop dynamics. Specifically, for a class of second order SISO systems, we show that this condition reduces to KD^2 > KP; where KP and KD are positive position and velocity feedback gains, respectively. Moreover, we provide a ÔpassivityÕ-based stability analysis which suggests that SPR of the tracking error dynamics is a necessary and sufficient condition for asymptotic hyperstability. Thus, the condition KD^2>KP mentioned above is not only a sufficient but also necessary condition to guarantee asymptotic hyperstability of FEL, i.e. the tracking error is bounded and asymptotically converges to zero. As a further point, we explore the adaptive control and FEL framework for feedforward control formulations, and derive an additional sufficient condition for asymptotic stability in the sense of Lyapunov. Finally, we present numerical simulations to illustrate the stability properties of FEL obtained from our mathematical analysis.

am

link (url) [BibTex]

link (url) [BibTex]


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Computational approaches to motor learning by imitation

Schaal, S., Ijspeert, A., Billard, A.

In The Neuroscience of Social Interaction, (1431):199-218, (Editors: Frith, C. D.;Wolpert, D.), Oxford University Press, Oxford, 2004, clmc (inbook)

Abstract
Movement imitation requires a complex set of mechanisms that map an observed movement of a teacher onto one's own movement apparatus. Relevant problems include movement recognition, pose estimation, pose tracking, body correspondence, coordinate transformation from external to egocentric space, matching of observed against previously learned movement, resolution of redundant degrees-of-freedom that are unconstrained by the observation, suitable movement representations for imitation, modularization of motor control, etc. All of these topics by themselves are active research problems in computational and neurobiological sciences, such that their combination into a complete imitation system remains a daunting undertaking - indeed, one could argue that we need to understand the complete perception-action loop. As a strategy to untangle the complexity of imitation, this paper will examine imitation purely from a computational point of view, i.e. we will review statistical and mathematical approaches that have been suggested for tackling parts of the imitation problem, and discuss their merits, disadvantages and underlying principles. Given the focus on action recognition of other contributions in this special issue, this paper will primarily emphasize the motor side of imitation, assuming that a perceptual system has already identified important features of a demonstrated movement and created their corresponding spatial information. Based on the formalization of motor control in terms of control policies and their associated performance criteria, useful taxonomies of imitation learning can be generated that clarify different approaches and future research directions.

am

link (url) [BibTex]

link (url) [BibTex]


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Micro-and nano-scale robotics

Sitti, M.

In American Control Conference, 2004. Proceedings of the 2004, 1, pages: 1-8, 2004 (inproceedings)

pi

[BibTex]

[BibTex]


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Gecko inspired surface climbing robots

Menon, C., Murphy, M., Sitti, M.

In Robotics and Biomimetics, 2004. ROBIO 2004. IEEE International Conference on, pages: 431-436, 2004 (inproceedings)

pi

Project Page [BibTex]

Project Page [BibTex]


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Untersuchungen zum Magnetismus von Clustern und Nanopartikeln und zum Einfluss der Wechselwirkung mit ihrer Umgebung

Fauth, Kai

Julius-Maximilians-Universität Würzburg, Würzburg, 2004 (phdthesis)

mms

[BibTex]

[BibTex]


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Micromagnetism and the microstructure of high-temperature permanent magnets

Goll, D., Kronmüller, H., Stadelmaier, H. H.

{Journal of Applied Physics}, 96(11):6534-6545, 2004 (article)

mms

[BibTex]

[BibTex]


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Atomic defects and diffusion in intermetallic compounds with DO3 structure: An ab-initio study

Fähnle, M., Schimmele, L.

{Zeitschrift f\"ur Metallkunde}, 95, pages: 864-869, 2004 (article)

mms

[BibTex]

[BibTex]


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Cluster surface interactions: Small Fe clusters driven nonmagnetic on graphite

Fauth, K., Gold, S., He\ssler, M., Schütz, G.

{Chemical Physics Letters}, 392(4-6):498-502, 2004 (article)

mms

DOI [BibTex]

DOI [BibTex]


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\textquotesingleWetting by solid state’grain boundary phase transition in Zn-Al alloys

Straumal, B. B., Khruzhcheva, A. S., Lopez, G. A.

{Reviews on Advanced Materials Science}, 7(1):13-22, 2004 (article)

mms

[BibTex]

[BibTex]


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Two prototypes of metal adatom configurations on Mo(112): an ab initio study for Li and Co

Singer, R., Drautz, R., Fähnle, M.

{Surface Science}, 559, pages: 241-248, 2004 (article)

mms

[BibTex]

[BibTex]


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Grain boundary phase transitions and their influence on properties of polycrystals

Straumal, B., Baretzky, B.

{Interface Science}, 12(2-3):147-155, 2004 (article)

mms

[BibTex]

[BibTex]


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Hard magnetic hollow nanospheres

Goll, D., Berkowitz, A. E., Bertram, H. N.

In Proceedings of the 18th International Workshop on Rare-Earth Magnets and their Applications, pages: 704-707, Laboratoire de Cristallographie/Laboratoire Louis Neel, CNRS, Grenoble, 2004 (inproceedings)

mms

[BibTex]

[BibTex]


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Swift heavy ion induced modification of Si/C60 multilayers

Srivastava, S. K., Kabiraj, D., Schattat, B., Carstanjen, H. D., Avasthi, D. K.

{Nuclear Instruments and Methods in Physics Research B}, 219 - 220, pages: 815-819, 2004 (article)

mms

[BibTex]

[BibTex]


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Static displacements of Pd in the solid solution PdBy (0\textlessy\textless0.2) as determined by neutron diffraction

Berger, T. G., Leineweber, A., Mittemeijer, E. J., Fischer, P.

{Physica Status Solidi (A)}, 201, pages: 1484-1492, 2004 (article)

mms

[BibTex]

[BibTex]


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X-MCD magnetometry of CMR perovskites La0.67-yREyCa0.33MnO3

Sikora, M., Kapusta, C., Zajac, D., Tokarz, W., Oates, C. J., Borowiec, M., Rybicki, D., Goering, E. J., Fischer, P., Schütz, G., De Teresa, J. M., Ibarra, M. R.

{Journal of Magnetism and Magnetic Materials}, 272-276, pages: 2148-2150, 2004 (article)

mms

[BibTex]

[BibTex]


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Critical thicknesses of domain formations in cubic particles and thin films

Kronmüller, H., Goll, D., Hertel, R., Schütz, G.

{Physica B}, 343(1-4):229-235, 2004 (article)

mms

[BibTex]

[BibTex]


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Effect of Grain Boundary Phase Transitions on the Superplasticity in the Al-Zn System

Lopez, G.A., Straumal, B.B., Gust, W., Mittemeijer, E.J.

In Nanomaterials by Severe Plastic Deformation, pages: 642-647, Wiley-VCH Verlag, Weinheim, 2004 (incollection)

mms

[BibTex]

[BibTex]

1996


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A kendama learning robot based on a dynamic optimiation principle

Miyamoto, H., Gandolfo, F., Gomi, H., Schaal, S., Koike, Y., Rieka, O., Nakano, E., Wada, Y., Kawato, M.

In Preceedings of the International Conference on Neural Information Processing, pages: 938-942, Hong Kong, September 1996, clmc (inproceedings)

am

[BibTex]

1996


[BibTex]


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Incorporating invariances in support vector learning machines

Schölkopf, B., Burges, C., Vapnik, V.

In Artificial Neural Networks: ICANN 96, LNCS vol. 1112, pages: 47-52, (Editors: C von der Malsburg and W von Seelen and JC Vorbrüggen and B Sendhoff), Springer, Berlin, Germany, 6th International Conference on Artificial Neural Networks, July 1996, volume 1112 of Lecture Notes in Computer Science (inproceedings)

Abstract
Developed only recently, support vector learning machines achieve high generalization ability by minimizing a bound on the expected test error; however, so far there existed no way of adding knowledge about invariances of a classification problem at hand. We present a method of incorporating prior knowledge about transformation invariances by applying transformations to support vectors, the training examples most critical for determining the classification boundary.

ei

PDF DOI [BibTex]

PDF DOI [BibTex]


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A Kendama learning robot based on bi-directional theory

Miyamoto, H., Schaal, S., Gandolfo, F., Koike, Y., Osu, R., Nakano, E., Wada, Y., Kawato, M.

Neural Networks, 9(8):1281-1302, 1996, clmc (article)

Abstract
A general theory of movement-pattern perception based on bi-directional theory for sensory-motor integration can be used for motion capture and learning by watching in robotics. We demonstrate our methods using the game of Kendama, executed by the SARCOS Dextrous Slave Arm, which has a very similar kinematic structure to the human arm. Three ingredients have to be integrated for the successful execution of this task. The ingredients are (1) to extract via-points from a human movement trajectory using a forward-inverse relaxation model, (2) to treat via-points as a control variable while reconstructing the desired trajectory from all the via-points, and (3) to modify the via-points for successful execution. In order to test the validity of the via-point representation, we utilized a numerical model of the SARCOS arm, and examined the behavior of the system under several conditions.

am

link (url) [BibTex]

link (url) [BibTex]


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From isolation to cooperation: An alternative of a system of experts

Schaal, S., Atkeson, C. G.

In Advances in Neural Information Processing Systems 8, pages: 605-611, (Editors: Touretzky, D. S.;Mozer, M. C.;Hasselmo, M. E.), MIT Press, Cambridge, MA, 1996, clmc (inbook)

Abstract
We introduce a constructive, incremental learning system for regression problems that models data by means of locally linear experts. In contrast to other approaches, the experts are trained independently and do not compete for data during learning. Only when a prediction for a query is required do the experts cooperate by blending their individual predictions. Each expert is trained by minimizing a penalized local cross validation error using second order methods. In this way, an expert is able to adjust the size and shape of the receptive field in which its predictions are valid, and also to adjust its bias on the importance of individual input dimensions. The size and shape adjustment corresponds to finding a local distance metric, while the bias adjustment accomplishes local dimensionality reduction. We derive asymptotic results for our method. In a variety of simulations we demonstrate the properties of the algorithm with respect to interference, learning speed, prediction accuracy, feature detection, and task oriented incremental learning. 

am

link (url) [BibTex]

link (url) [BibTex]


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One-handed juggling: A dynamical approach to a rhythmic movement task

Schaal, S., Sternad, D., Atkeson, C. G.

Journal of Motor Behavior, 28(2):165-183, 1996, clmc (article)

Abstract
The skill of rhythmic juggling a ball on a racket is investigated from the viewpoint of nonlinear dynamics. The difference equations that model the dynamical system are analyzed by means of local and non-local stability analyses. These analyses yield that the task dynamics offer an economical juggling pattern which is stable even for open-loop actuator motion. For this pattern, two types of pre dictions are extracted: (i) Stable periodic bouncing is sufficiently characterized by a negative acceleration of the racket at the moment of impact with the ball; (ii) A nonlinear scaling relation maps different juggling trajectories onto one topologically equivalent dynamical system. The relevance of these results for the human control of action was evaluated in an experiment where subjects performed a comparable task of juggling a ball on a paddle. Task manipulations involved different juggling heights and gravity conditions of the ball. The predictions were confirmed: (i) For stable rhythmic performance the paddle's acceleration at impact is negative and fluctuations of the impact acceleration follow predictions from global stability analysis; (ii) For each subject, the realizations of juggling for the different experimental conditions are related by the scaling relation. These results allow the conclusion that for the given task, humans reliably exploit the stable solutions inherent to the dynamics of the task and do not overrule these dynamics by other control mechanisms. The dynamical scaling serves as an efficient principle to generate different movement realizations from only a few parameter changes and is discussed as a dynamical formalization of the principle of motor equivalence.

am

link (url) [BibTex]

link (url) [BibTex]