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2002


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A kernel approach for learning from almost orthogonal patterns

Schölkopf, B., Weston, J., Eskin, E., Leslie, C., Noble, W.

In Principles of Data Mining and Knowledge Discovery, Lecture Notes in Computer Science, 2430/2431, pages: 511-528, Lecture Notes in Computer Science, (Editors: T Elomaa and H Mannila and H Toivonen), Springer, Berlin, Germany, 13th European Conference on Machine Learning (ECML) and 6th European Conference on Principles and Practice of Knowledge Discovery in Databases (PKDD'2002), 2002 (inproceedings)

ei

PostScript DOI [BibTex]

2002


PostScript DOI [BibTex]


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Choosing Multiple Parameters for Support Vector Machines

Chapelle, O., Vapnik, V., Bousquet, O., Mukherjee, S.

Machine Learning, 46(1):131-159, 2002 (article)

Abstract
The problem of automatically tuning multiple parameters for pattern recognition Support Vector Machines (SVM) is considered. This is done by minimizing some estimates of the generalization error of SVMs using a gradient descent algorithm over the set of parameters. Usual methods for choosing parameters, based on exhaustive search become intractable as soon as the number of parameters exceeds two. Some experimental results assess the feasibility of our approach for a large number of parameters (more than 100) and demonstrate an improvement of generalization performance.

ei

PDF PostScript [BibTex]

PDF PostScript [BibTex]


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Infinite Mixtures of Gaussian Process Experts

Rasmussen, CE., Ghahramani, Z.

In (Editors: Dietterich, Thomas G.; Becker, Suzanna; Ghahramani, Zoubin), 2002 (inproceedings)

Abstract
We present an extension to the Mixture of Experts (ME) model, where the individual experts are Gaussian Process (GP) regression models. Using a input-dependent adaptation of the Dirichlet Process, we implement a gating network for an infinite number of Experts. Inference in this model may be done efficiently using a Markov Chain relying on Gibbs sampling. The model allows the effective covariance function to vary with the inputs, and may handle large datasets -- thus potentially overcoming two of the biggest hurdles with GP models. Simulations show the viability of this approach.

ei

PDF PostScript [BibTex]

PDF PostScript [BibTex]


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Marginalized kernels for RNA sequence data analysis

Kin, T., Tsuda, K., Asai, K.

In Genome Informatics 2002, pages: 112-122, (Editors: Lathtop, R. H.; Nakai, K.; Miyano, S.; Takagi, T.; Kanehisa, M.), Genome Informatics, 2002, (Best Paper Award) (inproceedings)

ei

Web [BibTex]

Web [BibTex]


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Luminance Artifacts on CRT Displays

Wichmann, F.

In IEEE Visualization, pages: 571-574, (Editors: Moorhead, R.; Gross, M.; Joy, K. I.), IEEE Visualization, 2002 (inproceedings)

Abstract
Most visualization panels today are still built around cathode-ray tubes (CRTs), certainly on personal desktops at work and at home. Whilst capable of producing pleasing images for common applications ranging from email writing to TV and DVD presentation, it is as well to note that there are a number of nonlinear transformations between input (voltage) and output (luminance) which distort the digital and/or analogue images send to a CRT. Some of them are input-independent and hence easy to fix, e.g. gamma correction, but others, such as pixel interactions, depend on the content of the input stimulus and are thus harder to compensate for. CRT-induced image distortions cause problems not only in basic vision research but also for applications where image fidelity is critical, most notably in medicine (digitization of X-ray images for diagnostic purposes) and in forms of online commerce, such as the online sale of images, where the image must be reproduced on some output device which will not have the same transfer function as the customer's CRT. I will present measurements from a number of CRTs and illustrate how some of their shortcomings may be problematic for the aforementioned applications.

ei

[BibTex]

[BibTex]


Chirality-specific nonlinear spectroscopies in isotropic media
Chirality-specific nonlinear spectroscopies in isotropic media

Fischer, P., Albrecht, A.

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 75(5):1119-1124, 2002, 10th International Conference on Time-Resolved Vibrational Spectroscopy (TRVS 2001), OKAZZAKI, JAPAN, MAY 21-25, 2001 (article)

Abstract
Sum or difference frequency generation (SFG or DFG) in isotropic media is in the electric-dipole approximation only symmetry allowed for optically active systems. The hyperpolarizability giving rise to these three-wave mixing processes features only one isotropic component. It factorizes into two terms, an energy (denominator) factor and a triple product of transition moments. These forbid degenerate SFG, i.e., second harmonic generation, as well as the existence of the linear electrooptic effect (Pockels effect) in isotropic media. This second order response also has no static limit, which leads to particularly strong resonance phenomena that are qualitatively different from those usually seen in the ubiquitous even-wave mixing spectroscopies. In particular, the participation of two (not the usual one) excited states is essential to achieve dramatic resonance enhancement, We report our first efforts to see such resonantly enhanced chirality specific SFG.

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DOI [BibTex]

DOI [BibTex]


The chiral specificity of sum-frequency generation in solutions
The chiral specificity of sum-frequency generation in solutions

Fischer, P., Beckwitt, K., Wise, F., Albrecht, A.

CHEMICAL PHYSICS LETTERS, 352(5-6):463-468, 2002 (article)

Abstract
Sum-frequency generation in isotropic media is in the electric-dipole approximation the only symmetry allowed for chiral systems. We demonstrate that the sum-frequency intensity from an optically active liquid depends quadratically on the difference in concentration of the two enantiomers. The dominant contribution to the signal is found to be due to the chirality specific electric-dipolar three-wave mixing nonlinearity. Selecting the polarization of all fields allows the chiral electric-dipolar contributions to the bulk sum-frequency signal to be discerned from any achiral magnetic-dipolar and electric-quadrupolar contributions. (C) 2002 Published by Elsevier Science B.V.

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DOI [BibTex]

DOI [BibTex]


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Inferring hand motion from multi-cell recordings in motor cortex using a Kalman filter

Wu, W., Black M., Gao, Y., Bienenstock, E., Serruya, M., Donoghue, J.

Program No. 357.5. 2002 Abstract Viewer/Itinerary Planner, Society for Neuroscience, Washington, DC, 2002, Online (conference)

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abstract [BibTex]

abstract [BibTex]


On optical rectification in isotropic media
On optical rectification in isotropic media

Fischer, P., Albrecht, A.

LASER PHYSICS, 12(8):1177-1181, 2002 (article)

Abstract
Coherent nonlinear optical processes at second-order are only electric-dipole allowed in isotropic media that are optically active. Sum-frequency generation in chiral liquids has recently been observed, and difference-frequency and optical rectification have been predicted to exist in isotropic chiral media. Both Rayleigh-Schrodinger perturbation theory and the density matrix approach are used to discuss the quantum-chemical basis of optical rectification in optically active liquids. For pinene we compute the corresponding orientationally averaged hyperpolarizability, and estimate the light-induced dc electric polarization and the consequent voltage across a measuring capacitor it may give rise to near resonance.

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[BibTex]

[BibTex]


Probabilistic inference of hand motion from neural activity in motor cortex
Probabilistic inference of hand motion from neural activity in motor cortex

Gao, Y., Black, M. J., Bienenstock, E., Shoham, S., Donoghue, J.

In Advances in Neural Information Processing Systems 14, pages: 221-228, MIT Press, 2002 (inproceedings)

Abstract
Statistical learning and probabilistic inference techniques are used to infer the hand position of a subject from multi-electrode recordings of neural activity in motor cortex. First, an array of electrodes provides train- ing data of neural firing conditioned on hand kinematics. We learn a non- parametric representation of this firing activity using a Bayesian model and rigorously compare it with previous models using cross-validation. Second, we infer a posterior probability distribution over hand motion conditioned on a sequence of neural test data using Bayesian inference. The learned firing models of multiple cells are used to define a non- Gaussian likelihood term which is combined with a prior probability for the kinematics. A particle filtering method is used to represent, update, and propagate the posterior distribution over time. The approach is com- pared with traditional linear filtering methods; the results suggest that it may be appropriate for neural prosthetic applications.

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pdf [BibTex]

pdf [BibTex]


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Learning rhythmic movements by demonstration using nonlinear oscillators

Ijspeert, J. A., Nakanishi, J., Schaal, S.

In IEEE International Conference on Intelligent Robots and Systems (IROS 2002), pages: 958-963, Piscataway, NJ: IEEE, Lausanne, Sept.30-Oct.4 2002, 2002, clmc (inproceedings)

Abstract
Locally weighted learning (LWL) is a class of statistical learning techniques that provides useful representations and training algorithms for learning about complex phenomena during autonomous adaptive control of robotic systems. This paper introduces several LWL algorithms that have been tested successfully in real-time learning of complex robot tasks. We discuss two major classes of LWL, memory-based LWL and purely incremental LWL that does not need to remember any data explicitly. In contrast to the traditional beliefs that LWL methods cannot work well in high-dimensional spaces, we provide new algorithms that have been tested in up to 50 dimensional learning problems. The applicability of our LWL algorithms is demonstrated in various robot learning examples, including the learning of devil-sticking, pole-balancing of a humanoid robot arm, and inverse-dynamics learning for a seven degree-of-freedom robot.

am

link (url) [BibTex]

link (url) [BibTex]


Automatic detection and tracking of human motion with a view-based representation
Automatic detection and tracking of human motion with a view-based representation

Fablet, R., Black, M. J.

In European Conf. on Computer Vision, ECCV 2002, 1, pages: 476-491, LNCS 2353, (Editors: A. Heyden and G. Sparr and M. Nielsen and P. Johansen), Springer-Verlag , 2002 (inproceedings)

Abstract
This paper proposes a solution for the automatic detection and tracking of human motion in image sequences. Due to the complexity of the human body and its motion, automatic detection of 3D human motion remains an open, and important, problem. Existing approaches for automatic detection and tracking focus on 2D cues and typically exploit object appearance (color distribution, shape) or knowledge of a static background. In contrast, we exploit 2D optical flow information which provides rich descriptive cues, while being independent of object and background appearance. To represent the optical flow patterns of people from arbitrary viewpoints, we develop a novel representation of human motion using low-dimensional spatio-temporal models that are learned using motion capture data of human subjects. In addition to human motion (the foreground) we probabilistically model the motion of generic scenes (the background); these statistical models are defined as Gibbsian fields specified from the first-order derivatives of motion observations. Detection and tracking are posed in a principled Bayesian framework which involves the computation of a posterior probability distribution over the model parameters (i.e., the location and the type of the human motion) given a sequence of optical flow observations. Particle filtering is used to represent and predict this non-Gaussian posterior distribution over time. The model parameters of samples from this distribution are related to the pose parameters of a 3D articulated model (e.g. the approximate joint angles and movement direction). Thus the approach proves suitable for initializing more complex probabilistic models of human motion. As shown by experiments on real image sequences, our method is able to detect and track people under different viewpoints with complex backgrounds.

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pdf [BibTex]

pdf [BibTex]


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Chemical processes during solid state reaction of carbon with alkali salts prepared for gravimetric hydrogen storage measurements

Skakalova, V., Quintel, A., Choi, Y. M., Roth, S., Becher, M., Hirscher, M.

{Chemical Physics Letters}, 365(3-4):333-337, 2002 (article)

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[BibTex]

[BibTex]


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Micromagnetic analysis of nucleation-hardened nanocrystalline PrFeB magnets

Kronmüller, H., Goll, D.

{Scripta Materialia}, 47(8):551-556, 2002 (article)

mms

[BibTex]

[BibTex]


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The Verwey transition in magnetite as studied by means of definite impurity doping

Walz, F., Brabers, J. H. V. J., Brabers, V. A. M.

{Zeitschrift f\"ur Metallkunde}, 93(10):1095-1102, 2002 (article)

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[BibTex]

[BibTex]


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Antiparallel ruthenium coupling in doped La1.2Sr1.8Mn2-xRuxO7

Weigand, F., Gold, S., Schmid, A., Geissler, J., Goering, E., Dorr, K., Krabbes, G., Ruck, K.

{Applied Physics Letters}, 81(11):2035-2037, 2002 (article)

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[BibTex]

[BibTex]


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Micromagnetic theory of the pinning of domain walls at phase boundaries

Kronmüller, H., Goll, D.

{Physica B}, 319(1-4):122-126, 2002 (article)

mms

[BibTex]

[BibTex]


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Diffusion of oxygen in CdSe-photo sensor arrays

Klement, U., Ernst, F., Baretzky, B., Plitzko, J. M.

{Materials Science and Engineering B-Solid State Materials for Advanced Technology}, 94(2-3):123-130, 2002 (article)

mms

[BibTex]

[BibTex]


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Magnetic imaging with full-field soft X-ray microscopy

Fischer, P., Eimüller, T., Goll, D., Stoll, H., Puzic, A., Schütz, G., Denbeaux, G.

{Zeitschrift f\"ur Metallkunde}, 93(5):377-382, 2002 (article)

mms

[BibTex]

[BibTex]


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Magneto-optical studies of current distributions in high-Tc superconductors

Jooss, C., Albrecht, J., Kuhn, H., Leonhardt, S., Kronmüller, H.

{Reports on Progress in Physics}, 65(5):651-788, 2002 (article)

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[BibTex]

[BibTex]


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Dominant thermal defects in B2-FeAl

Bester, G., Meyer, B., Fähnle, M., Fu, C. L.

{Materials Science and Engineering A-Structural Materials Properties Microstructure and Processing}, 323(1-2):487-490, 2002 (article)

mms

[BibTex]

[BibTex]


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Hydrogen desorption kinetics of nanostructured MgH2 composite materials

von Zeppelin, F., Reule, H., Hirscher, M.

{Journal of Alloys and Compounds}, 330, pages: 723-726, 2002 (article)

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[BibTex]

[BibTex]


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Hydrogen in mechanically prepared nanostructured h-BN: a critical comparison with that in nanostructured graphite

Wang, P., Orimo, S., Matsushima, T., Fujii, H., Majer, G.

{Applied Physics Letters}, 80(2):318-320, 2002 (article)

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[BibTex]

[BibTex]


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Pressure Isotherms of Hydrogen Adsorption in Carbon Nanostructures

Chen, X., Dettlaff-Weglikowska, U., Haluska, M., Hulman, M., Roth, S., Hirscher, M., Becher, M.

In Making Functional Materials with Nanotubes, pages: Z9.11.1-Z9.11.6, Materials Research Society Symposium Proceedings, MRS, Boston [Mass.], 2002 (inproceedings)

mms

[BibTex]

[BibTex]


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Enhancement of the critical current density by silver sheeting of YBCO thin films

Kienzle, M., Albrecht, J., Warthmann, R., Kronmüller, H., Leonhardt, S., Joos, C.

{Physical Review B}, 66, 2002 (article)

mms

[BibTex]

[BibTex]


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Pt magnetization profile in a Pt/Co bilayer studied by resonant magnetic x-ray reflectometry

Geissler, J., Goering, E., Justen, M., Weigand, F., Schütz, G., Langer, J., Schmitz, D., Maletta, H., Mattheis, R.

{Physical Review B}, 65, 2002 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Imaging magnetic microstructures with soft x-ray microscopies

Fischer, P., Denbeaux, G., Nolting, F., Goll, D., Eimüller, T., Quitmann, C., Schütz, G.

{Transactions of the Magnetics Society of Japan}, 2, pages: 234-237, 2002 (article)

mms

[BibTex]

[BibTex]


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Positron age-momentum correlation (AMOC) measurements on organic liquids

Castellaz, P., Siegle, A., Stoll, H.

{Journal of Nuclear and Radiochemical Sciences}, 3, pages: R1-R7, 2002 (article)

mms

[BibTex]

[BibTex]


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Scalable techniques from nonparameteric statistics for real-time robot learning

Schaal, S., Atkeson, C. G., Vijayakumar, S.

Applied Intelligence, 17(1):49-60, 2002, clmc (article)

Abstract
Locally weighted learning (LWL) is a class of techniques from nonparametric statistics that provides useful representations and training algorithms for learning about complex phenomena during autonomous adaptive control of robotic systems. This paper introduces several LWL algorithms that have been tested successfully in real-time learning of complex robot tasks. We discuss two major classes of LWL, memory-based LWL and purely incremental LWL that does not need to remember any data explicitly. In contrast to the traditional belief that LWL methods cannot work well in high-dimensional spaces, we provide new algorithms that have been tested on up to 90 dimensional learning problems. The applicability of our LWL algorithms is demonstrated in various robot learning examples, including the learning of devil-sticking, pole-balancing by a humanoid robot arm, and inverse-dynamics learning for a seven and a 30 degree-of-freedom robot. In all these examples, the application of our statistical neural networks techniques allowed either faster or more accurate acquisition of motor control than classical control engineering.

am

link (url) [BibTex]

link (url) [BibTex]


A layered motion representation with occlusion and compact spatial support
A layered motion representation with occlusion and compact spatial support

Fleet, D. J., Jepson, A., Black, M. J.

In European Conf. on Computer Vision, ECCV 2002, 1, pages: 692-706, LNCS 2353, (Editors: A. Heyden and G. Sparr and M. Nielsen and P. Johansen), Springer-Verlag , 2002 (inproceedings)

Abstract
We describe a 2.5D layered representation for visual motion analysis. The representation provides a global interpretation of image motion in terms of several spatially localized foreground regions along with a background region. Each of these regions comprises a parametric shape model and a parametric motion model. The representation also contains depth ordering so visibility and occlusion are rightly included in the estimation of the model parameters. Finally, because the number of objects, their positions, shapes and sizes, and their relative depths are all unknown, initial models are drawn from a proposal distribution, and then compared using a penalized likelihood criterion. This allows us to automatically initialize new models, and to compare different depth orderings.

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pdf [BibTex]

pdf [BibTex]


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Theory of crystal field states for heavy rare-earth impurities in MgB2

Welsch, F., Kremer, R., Fähnle, M.

{Journal of Physics-Condensed Matter}, 14(43):10273-10279, 2002 (article)

mms

[BibTex]

[BibTex]


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Micromagnetism and microstructure - tailoring of high- performance permanent magnets

Goll, D.

{Zeitschrift f\"ur Metallkunde}, 93(10):1009-1018, 2002 (article)

mms

[BibTex]

[BibTex]


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Interplay between chemical and magnetic roughness of Pt in a Pt/Co bilayer investigated with X-ray resonant magnetic reflectometry

Geissler, J., Goering, E., Weigand, F., Schütz, G.

{Zeitschrift f\"ur Metallkunde}, 93(10):946-952, 2002 (article)

mms

[BibTex]


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Untersuchungen zur Spindynamik in nanostrukturierten ferromagnetischen Schichtsystemen

Puzic, A.

Universität Stuttgart, Stuttgart, 2002 (mastersthesis)

mms

[BibTex]

[BibTex]


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Direct correlation of Cr 3d orbital polarization and O K-edge X-ray magnetic circular dichroism of epitaxial CrO2 films

Goering, E., Bayer, A., Gold, S., Schütz, G., Rabe, M., Rüdiger, U., Güntherodt, G.

{Europhysics Letters}, 58(6):906-911, 2002 (article)

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[BibTex]

[BibTex]


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Surface magnetization reversal of sputtered CrO2

Goering, E., Gold, S., Will, J.

{Zeitschrift f\"ur Metallkunde}, 93(5):372-376, 2002 (article)

mms

[BibTex]

[BibTex]


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Shear-strain-related nonlinear magnetoelastic properties of epitaxial films

Komelj, M., Fähnle, M.

{Physical Review B}, 65(9), 2002 (article)

mms

[BibTex]

[BibTex]


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NMR studies of hydrogen diffusion in the hydrogen-stabilized Laves phase compound C15-HfTi2Hx

Eberle, U., Majer, G., Skripov, A. V., Kozhanov, V. N.

{Journal of Physics-Condensed Matter}, 14(2):153-164, 2002 (article)

mms

[BibTex]

[BibTex]


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The existence of more than one jump process of hydrogen in palladium-silver alloys - an NMR study

Züchner, H., Barlag, H., Majer, G.

{Journal of Alloys and Compounds}, 330-332, pages: 448-453, 2002 (article)

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[BibTex]

[BibTex]


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Hydrogen Storage in Carbon SWNTs: Atomic or Molecular?

Haluska, M., Hirscher, M., Becher, M., Dettlaff-Weglikowska, U., Chen, X., Roth, S.

In Structural and Electronic Properties of Molecular Nanostructures, pages: 601-605, AIP Conference Proceedings, AIP, Kirchberg, Tirol [Austria], 2002 (inproceedings)

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[BibTex]

[BibTex]


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Electric field distribution at low-angle grain boundaries in high-temperature superconductors

Jooss, C., Guth, K., Born, V., Albrecht, J.

{Physical Review B}, 65(1), 2002 (article)

mms

[BibTex]

[BibTex]


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Finite element calculations on the single-domain limit of a ferromagnetic cube - a solution to \microMAG Standard Problem No. 3

Hertel, R., Kronmüller, H.

{Journal of Magnetism and Magnetic Materials}, 238(2-3):185-199, 2002 (article)

mms

[BibTex]

[BibTex]


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Diffusion of oxygen in CdSe-photosensor arrays

Klement, U., Ernst, F., Baretzky, B., Plitzko, J. M.

{Materials Science and Engineering B}, 94, pages: 123-130, 2002 (article)

mms

[BibTex]

[BibTex]


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Influence of the grain boundary phase transitions on the diffusion-related properties

Straumal, B., Baretzky, B.

{Diffusion and Defect Forum}, 216-217, pages: 53-64, 2002 (article)

mms

[BibTex]

[BibTex]


Implicit probabilistic models of human motion for synthesis and tracking
Implicit probabilistic models of human motion for synthesis and tracking

Sidenbladh, H., Black, M. J., Sigal, L.

In European Conf. on Computer Vision, 1, pages: 784-800, 2002 (inproceedings)

Abstract
This paper addresses the problem of probabilistically modeling 3D human motion for synthesis and tracking. Given the high dimensional nature of human motion, learning an explicit probabilistic model from available training data is currently impractical. Instead we exploit methods from texture synthesis that treat images as representing an implicit empirical distribution. These methods replace the problem of representing the probability of a texture pattern with that of searching the training data for similar instances of that pattern. We extend this idea to temporal data representing 3D human motion with a large database of example motions. To make the method useful in practice, we must address the problem of efficient search in a large training set; efficiency is particularly important for tracking. Towards that end, we learn a low dimensional linear model of human motion that is used to structure the example motion database into a binary tree. An approximate probabilistic tree search method exploits the coefficients of this low-dimensional representation and runs in sub-linear time. This probabilistic tree search returns a particular sample human motion with probability approximating the true distribution of human motions in the database. This sampling method is suitable for use with particle filtering techniques and is applied to articulated 3D tracking of humans within a Bayesian framework. Successful tracking results are presented, along with examples of synthesizing human motion using the model.

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pdf [BibTex]

pdf [BibTex]


Robust parameterized component analysis: Theory and applications to {2D} facial modeling
Robust parameterized component analysis: Theory and applications to 2D facial modeling

De la Torre, F., Black, M. J.

In European Conf. on Computer Vision, ECCV 2002, 4, pages: 653-669, LNCS 2353, Springer-Verlag, 2002 (inproceedings)

ps

pdf [BibTex]

pdf [BibTex]


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Magneto-optical studies of flux pinning in high-temperature superconductors

Jooss, C., Albrecht, J.

{Zeitschrift f\"ur Metallkunde}, 93(10):1065-1070, 2002 (article)

mms

[BibTex]

[BibTex]


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From the bulk to monatomic wires: An ab initio study of magnetism in Co systems with various dimensionality

Komelj, M., Ederer, C., Davenport, J. W., Fähnle, M.

{Physical Review B}, 66(14), 2002 (article)

mms

[BibTex]

[BibTex]