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2005


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Composite adaptive control with locally weighted statistical learning

Nakanishi, J., Farrell, J. A., Schaal, S.

Neural Networks, 18(1):71-90, January 2005, clmc (article)

Abstract
This paper introduces a provably stable learning adaptive control framework with statistical learning. The proposed algorithm employs nonlinear function approximation with automatic growth of the learning network according to the nonlinearities and the working domain of the control system. The unknown function in the dynamical system is approximated by piecewise linear models using a nonparametric regression technique. Local models are allocated as necessary and their parameters are optimized on-line. Inspired by composite adaptive control methods, the proposed learning adaptive control algorithm uses both the tracking error and the estimation error to update the parameters. We first discuss statistical learning of nonlinear functions, and motivate our choice of the locally weighted learning framework. Second, we begin with a class of first order SISO systems for theoretical development of our learning adaptive control framework, and present a stability proof including a parameter projection method that is needed to avoid potential singularities during adaptation. Then, we generalize our adaptive controller to higher order SISO systems, and discuss further extension to MIMO problems. Finally, we evaluate our theoretical control framework in numerical simulations to illustrate the effectiveness of the proposed learning adaptive controller for rapid convergence and high accuracy of control.

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link (url) [BibTex]

2005


link (url) [BibTex]


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Global phase diagrams of binary dipolar fluid mixtures

Szalai, I., Dietrich, S.

Molecular Physics, 103(21-23):2873-2895, 2005 (article)

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[BibTex]

[BibTex]


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Reversible diffusion-limited reactions: "Chemical Equilibrium" state and the Law of Mass Action revisited

Voituriez, R., Moreau, M., Oshanin, G.

Europhysics Letters, 69(2):177-183, 2005 (article)

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[BibTex]

[BibTex]


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The depletion potential in one, two and three dimensions

Roth, R., König, P. M.

Pramana - Journal of Physics, 64(6):971-980, 2005 (article)

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[BibTex]

[BibTex]


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Saltatory drift in a randomly driven two-wave potential

Oshanin, G., Klafter, J., Urbakh, M.

Journal of Physics: Condensed Matter, 17(47, Sp. Iss. SI):S3697-S3707, 2005 (article)

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[BibTex]

[BibTex]


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A thin-film equation for viscoelastic liquids of Jeffreys type

Rauscher, M., Münch, A., Wagner, B., Blossey, R.

European Physical Journal E, 17(3):373-379, 2005 (article)

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[BibTex]

[BibTex]


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Curvature expansion of density profiles

König, P.-M., Bryk, P., Mecke, K. R., Roth, R.

Europhysics Letters, 69(5):832-838, 2005 (article)

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[BibTex]

[BibTex]


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General methods for free-volume theory

Oversteegen, S. M., Roth, R.

Journal of Chemical Physics, 122(21), 2005 (article)

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[BibTex]

[BibTex]


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Morphological characterisation of point patterns

Mecke, K., Stoyan, D.

Biometrical Journal, 47, pages: 1-16, 2005 (article)

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[BibTex]

[BibTex]


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Thermodynamic Casimir force in models of 4He films

Dantchev, D., Krech, M., Dietrich, S.

Physical Review Letters, 95(25), 2005 (article)

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[BibTex]

[BibTex]


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Capillary-induced interactions between colloids at an interface

Dominguez, A., Oettel, M., Dietrich, S.

Journal of Physics: Condensed Matter, 17(45):S3387-S3392, 2005 (article)

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[BibTex]

[BibTex]


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Homogeneous and inhomogeneous hard-sphere mixtures: manifestations of structural crossover

Grodon, C., Dijkstra, M., Evans, R., Roth, R.

Molecular Physics, 103, pages: 3009-3023, 2005 (article)

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[BibTex]

[BibTex]


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Critical behavior of the two-dimensional randomly driven lattice gas

Caracciolo, S., Gambassi, A., Gubinelli, M., Pelissetto, A.

Physical Review E, 72(5), 2005 (article)

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[BibTex]

[BibTex]


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Integral equations for simple fluids in a general reference functional approach

Oettel, M.

Journal of Physics: Condensed Matter, 17(3):429-452, 2005 (article)

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[BibTex]

[BibTex]


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Ageing properties of critical systems

Calabrese, P., Gambassi, A.

Journal of Physics A, 38(18):R133-R193, 2005 (article)

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[BibTex]

[BibTex]


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Physics of size selectivity

Roth, R., Gillespie, D.

Physical Review Letters, 95, 2005 (article)

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[BibTex]

[BibTex]


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Solvent mediated interactions close to fluid-fluid phase separation: microscopic treatment of bridging in a soft-core fluid

Archer, A. J., Evans, R., Roth, R., Oettel, M.

Journal of Chemical Physics, 122, 2005 (article)

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[BibTex]

[BibTex]


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Phase behavior of a nematic liquid crystal in contact with a chemically and geometrically structured substrate

Harnau, L., Kondrat, S., Poniewierski, A.

Physical Review E, 72, 2005 (article)

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[BibTex]

[BibTex]


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Diffusive spreading and mixing of fluid monolayers

Popescu, M. N., Dietrich, S., Oshanin, G.

Journal of Physics: Condensed Matter, 17(49):S4189-S4198, 2005 (article)

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[BibTex]

[BibTex]


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Free isotropic-nematic interfaces in fluids of charged platelike colloids

Bier, M., Harnau, L., Dietrich, S.

Journal of Chemical Physics, 123, 2005 (article)

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[BibTex]

[BibTex]


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Critical adsorption at chemically structured substrates

Sprenger, M., Schlesener, F., Dietrich, S.

Physical Review E, 71, 2005 (article)

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DOI [BibTex]

DOI [BibTex]


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Local density profiles in thin films and multilayers from diffuse x-ray and neutron scattering

Rauscher, M., Reichert, H., Engemann, S., Dosch, H.

Physical Review B, 72(20), 2005 (article)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Corrections to the law of mass action and properties of the asymptotic t\textequalsinfinity state for reversible diffusion-limited reactions

Voituriez, R., Moreau, M., Oshanin, G.

Journal of Chemical Physics, 122(8), 2005 (article)

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[BibTex]


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Corrections to local scale invariance in the nonequilibrium dynamics of critical systems: numerical evidences

Pleimling, M., Gambassi, A.

Physical Review B, 71(18), 2005 (article)

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[BibTex]


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Kinetics of diffusion-limited catalytically activated reactions: an extension of the Wilemski-Fixman approach

Benichou, O., Coppey, M., Moreau, M., Oshanin, G.

The Journal of Chemical Physics, 123, 2005 (article)

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[BibTex]

[BibTex]


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Adhesive gravitational clustering

Buchert, T., Dominguez, A.

Astronomy & Astrophysics, 438(2):443-460, 2005 (article)

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[BibTex]

[BibTex]


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Effective pair interactions between colloidal particles at a nematic-isotropic interface

Andrienko, D., Tasinkevych, M., Dietrich, S.

Europhysics Letters, 70(1):95-101, 2005 (article)

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[BibTex]

[BibTex]


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The Boolean Model: from Matheron till today

Stoyan, D., Mecke, K.

In Space, Structure and Randomness: contributions in honor of Georges Matheron in the fields of geostatistics, random sets, and mathematical morphology, 183, pages: 151-182, Lecture Notes in Statistics, Springer, New York, 2005 (incollection)

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[BibTex]

[BibTex]


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On thermal fluctuations in thin film flow

Mecke, K., Rauscher, M.

Journal of Physics: Condensed Matter, 17(45):S3515-S3522, 2005 (article)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Scaling in the time domain: Universal dynamics of order fluctuations in Fe3Al

Mocuta, C., Reichert, H., Mecke, K., Dosch, H., Drakopoulos, M.

Science, 308(5726):1287-1291, 2005 (article)

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[BibTex]

[BibTex]


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Structure and equation of state of interaction site models for disc-shaped lamellar colloids

Costa, D., Hansen, J.-P., Harnau, L.

Molecular Physics, 103(14):1917-1927, 2005 (article)

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[BibTex]

[BibTex]


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Local density profiles in thin films and multilayers from diffuse x-ray and neutron scattering

Rauscher, M., Reichert, H., Engemann, S., Dosch, H.

Physical Review B, 72, 2005 (article)

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[BibTex]

[BibTex]


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Fluids in porous media: a morphometric approach

Mecke, K., Arns, C. H.

Journal of Physics: Condensed Matter, 17, pages: S503-S534, 2005 (article)

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[BibTex]

[BibTex]


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Fluid mixtures at curved walls

Roth, R.

Journal of Physics: Condensed Matter, 17, pages: S3463-S3468, 2005 (article)

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[BibTex]

[BibTex]


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Microscopic model of charge carrier transfer in complex media

Benichou, O., Klafter, J., Moreau, M., Oshanin, G.

Chemical Physics, 319(1-3):16-27, 2005 (article)

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[BibTex]

[BibTex]


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Wetting on structured substrates

Dietrich, S., Popescu, M. N., Rauscher, M.

Journal of Physics: Condensed Matter, 17(9):S577-S593, 2005 (article)

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[BibTex]

[BibTex]


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Attractions between charged colloids at water interfaces

Oettel, M., Dominguez, A., Dietrich, S.

Journal of Physics: Condensed Matter, 17(32):L337-L342, 2005 (article)

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[BibTex]

[BibTex]


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Effective capillary interaction of spherical particles at fluid interfaces

Oettel, M., Dominguez, A., Dietrich, S.

Physical Review E, 71, 2005 (article)

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[BibTex]

[BibTex]


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Local orientations of fluctuating fluid interfaces

Mecke, K., Dietrich, S.

Journal of Chemical Physics, 123(20), 2005 (article)

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[BibTex]

[BibTex]


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Evidence for capillarity contributions to gecko adhesion from single spatula nanomechanical measurements

Huber, G., Mantz, H., Spolenak, R., Mecke, K., Jacobs, K., Gorb, S. N., Arzt, E.

Proceedings of the National Academy of Sciences of the United States, 102(45):16293-16296, 2005 (article)

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[BibTex]

[BibTex]


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Swollen lamellar phases confined in capillary-like pores

Tasinkevych, M., Ciach, A.

Physical Review E, 72(6), 2005 (article)

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[BibTex]

[BibTex]


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Nematic liquid crystal in contact with periodically patterned surfaces

Kondrat, S., Poniewierski, A., Harnau, L.

Liquid Crystals, 32(1):95-105, 2005 (article)

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[BibTex]

[BibTex]


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A model of smooth pursuit based on learning of the target dynamics using only retinal signals

Shibata, T., Tabata, H., Schaal, S., Kawato, M.

Neural Networks, 18, pages: 213-225, 2005, clmc (article)

Abstract
While the predictive nature of the primate smooth pursuit system has been evident through several behavioural and neurophysiological experiments, few models have attempted to explain these results comprehensively. The model we propose in this paper in line with previous models employing optimal control theory; however, we hypothesize two new issues: (1) the medical superior temporal (MST) area in the cerebral cortex implements a recurrent neural network (RNN) in order to predict the current or future target velocity, and (2) a forward model of the target motion is acquired by on-line learning. We use stimulation studies to demonstrate how our new model supports these hypotheses.

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link (url) [BibTex]

link (url) [BibTex]


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Parametric and Non-Parametric approaches for nonlinear tracking of moving objects

Hidaka, Y, Theodorou, E.

Technical Report-2005-1, 2005, clmc (article)

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PDF [BibTex]

PDF [BibTex]

1999


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Is imitation learning the route to humanoid robots?

Schaal, S.

Trends in Cognitive Sciences, 3(6):233-242, 1999, clmc (article)

Abstract
This review will focus on two recent developments in artificial intelligence and neural computation: learning from imitation and the development of humanoid robots. It will be postulated that the study of imitation learning offers a promising route to gain new insights into mechanisms of perceptual motor control that could ultimately lead to the creation of autonomous humanoid robots. This hope is justified because imitation learning channels research efforts towards three important issues: efficient motor learning, the connection between action and perception, and modular motor control in form of movement primitives. In order to make these points, first, a brief review of imitation learning will be given from the view of psychology and neuroscience. In these fields, representations and functional connections between action and perception have been explored that contribute to the understanding of motor acts of other beings. The recent discovery that some areas in the primate brain are active during both movement perception and execution provided a first idea of the possible neural basis of imitation. Secondly, computational approaches to imitation learning will be described, initially from the perspective of traditional AI and robotics, and then with a focus on neural network models and statistical learning research. Parallels and differences between biological and computational approaches to imitation will be highlighted. The review will end with an overview of current projects that actually employ imitation learning for humanoid robots.

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link (url) [BibTex]

1999


link (url) [BibTex]


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Nonparametric regression for learning nonlinear transformations

Schaal, S.

In Prerational Intelligence in Strategies, High-Level Processes and Collective Behavior, 2, pages: 595-621, (Editors: Ritter, H.;Cruse, H.;Dean, J.), Kluwer Academic Publishers, 1999, clmc (inbook)

Abstract
Information processing in animals and artificial movement systems consists of a series of transformations that map sensory signals to intermediate representations, and finally to motor commands. Given the physical and neuroanatomical differences between individuals and the need for plasticity during development, it is highly likely that such transformations are learned rather than pre-programmed by evolution. Such self-organizing processes, capable of discovering nonlinear dependencies between different groups of signals, are one essential part of prerational intelligence. While neural network algorithms seem to be the natural choice when searching for solutions for learning transformations, this paper will take a more careful look at which types of neural networks are actually suited for the requirements of an autonomous learning system. The approach that we will pursue is guided by recent developments in learning theory that have linked neural network learning to well established statistical theories. In particular, this new statistical understanding has given rise to the development of neural network systems that are directly based on statistical methods. One family of such methods stems from nonparametric regression. This paper will compare nonparametric learning with the more widely used parametric counterparts in a non technical fashion, and investigate how these two families differ in their properties and their applicabilities. We will argue that nonparametric neural networks offer a set of characteristics that make them a very promising candidate for on-line learning in autonomous system.

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link (url) [BibTex]

link (url) [BibTex]


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Segmentation of endpoint trajectories does not imply segmented control

Sternad, D., Schaal, D.

Experimental Brain Research, 124(1):118-136, 1999, clmc (article)

Abstract
While it is generally assumed that complex movements consist of a sequence of simpler units, the quest to define these units of action, or movement primitives, still remains an open question. In this context, two hypotheses of movement segmentation of endpoint trajectories in 3D human drawing movements are re-examined: (1) the stroke-based segmentation hypothesis based on the results that the proportionality coefficient of the 2/3 power law changes discontinuously with each new â??strokeâ?, and (2) the segmentation hypothesis inferred from the observation of piecewise planar endpoint trajectories of 3D drawing movements. In two experiments human subjects performed a set of elliptical and figure-8 patterns of different sizes and orientations using their whole arm in 3D. The kinematic characteristics of the endpoint trajectories and the seven joint angles of the arm were analyzed. While the endpoint trajectories produced similar segmentation features as reported in the literature, analyses of the joint angles show no obvious segmentation but rather continuous oscillatory patterns. By approximating the joint angle data of human subjects with sinusoidal trajectories, and by implementing this model on a 7-degree-of-freedom anthropomorphic robot arm, it is shown that such a continuous movement strategy can produce exactly the same features as observed by the above segmentation hypotheses. The origin of this apparent segmentation of endpoint trajectories is traced back to the nonlinear transformations of the forward kinematics of human arms. The presented results demonstrate that principles of discrete movement generation may not be reconciled with those of rhythmic movement as easily as has been previously suggested, while the generalization of nonlinear pattern generators to arm movements can offer an interesting alternative to approach the question of units of action.

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link (url) [BibTex]

link (url) [BibTex]