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2003


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Guest editorial: Computational vision at Brown

Black, M. J., Kimia, B.

International Journal of Computer Vision, 54(1-3):5-11, August 2003 (article)

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pdf pdf from publisher [BibTex]

2003


pdf pdf from publisher [BibTex]


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Statistical Learning Theory, Capacity and Complexity

Schölkopf, B.

Complexity, 8(4):87-94, July 2003 (article)

Abstract
We give an exposition of the ideas of statistical learning theory, followed by a discussion of how a reinterpretation of the insights of learning theory could potentially also benefit our understanding of a certain notion of complexity.

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Web DOI [BibTex]


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Robust parameterized component analysis: Theory and applications to 2D facial appearance models

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

Computer Vision and Image Understanding, 91(1-2):53-71, July 2003 (article)

Abstract
Principal component analysis (PCA) has been successfully applied to construct linear models of shape, graylevel, and motion in images. In particular, PCA has been widely used to model the variation in the appearance of people's faces. We extend previous work on facial modeling for tracking faces in video sequences as they undergo significant changes due to facial expressions. Here we consider person-specific facial appearance models (PSFAM), which use modular PCA to model complex intra-person appearance changes. Such models require aligned visual training data; in previous work, this has involved a time consuming and error-prone hand alignment and cropping process. Instead, the main contribution of this paper is to introduce parameterized component analysis to learn a subspace that is invariant to affine (or higher order) geometric transformations. The automatic learning of a PSFAM given a training image sequence is posed as a continuous optimization problem and is solved with a mixture of stochastic and deterministic techniques achieving sub-pixel accuracy. We illustrate the use of the 2D PSFAM model with preliminary experiments relevant to applications including video-conferencing and avatar animation.

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pdf [BibTex]

pdf [BibTex]


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Dealing with large Diagonals in Kernel Matrices

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

Annals of the Institute of Statistical Mathematics, 55(2):391-408, June 2003 (article)

Abstract
In kernel methods, all the information about the training data is contained in the Gram matrix. If this matrix has large diagonal values, which arises for many types of kernels, then kernel methods do not perform well: We propose and test several methods for dealing with this problem by reducing the dynamic range of the matrix while preserving the positive definiteness of the Hessian of the quadratic programming problem that one has to solve when training a Support Vector Machine, which is a common kernel approach for pattern recognition.

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PDF DOI [BibTex]

PDF DOI [BibTex]


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The em Algorithm for Kernel Matrix Completion with Auxiliary Data

Tsuda, K., Akaho, S., Asai, K.

Journal of Machine Learning Research, 4, pages: 67-81, May 2003 (article)

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PDF [BibTex]

PDF [BibTex]


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Constructing Descriptive and Discriminative Non-linear Features: Rayleigh Coefficients in Kernel Feature Spaces

Mika, S., Rätsch, G., Weston, J., Schölkopf, B., Smola, A., Müller, K.

IEEE Transactions on Pattern Analysis and Machine Intelligence, 25(5):623-628, May 2003 (article)

Abstract
We incorporate prior knowledge to construct nonlinear algorithms for invariant feature extraction and discrimination. Employing a unified framework in terms of a nonlinearized variant of the Rayleigh coefficient, we propose nonlinear generalizations of Fisher‘s discriminant and oriented PCA using support vector kernel functions. Extensive simulations show the utility of our approach.

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DOI [BibTex]

DOI [BibTex]


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Kernel-based nonlinear blind source separation

Harmeling, S., Ziehe, A., Kawanabe, M., Müller, K.

Neural Computation, 15(5):1089-1124, May 2003 (article)

Abstract
We propose kTDSEP, a kernel-based algorithm for nonlinear blind source separation (BSS). It combines complementary research fields: kernel feature spaces and BSS using temporal information. This yields an efficient algorithm for nonlinear BSS with invertible nonlinearity. Key assumptions are that the kernel feature space is chosen rich enough to approximate the nonlinearity and that signals of interest contain temporal information. Both assumptions are fulfilled for a wide set of real-world applications. The algorithm works as follows: First, the data are (implicitly) mapped to a high (possibly infinite)—dimensional kernel feature space. In practice, however, the data form a smaller submanifold in feature space—even smaller than the number of training data points—a fact that has already been used by, for example, reduced set techniques for support vector machines. We propose to adapt to this effective dimension as a preprocessing step and to construct an orthonormal basis of this submanifold. The latter dimension-reduction step is essential for making the subsequent application of BSS methods computationally and numerically tractable. In the reduced space, we use a BSS algorithm that is based on second-order temporal decorrelation. Finally, we propose a selection procedure to obtain the original sources from the extracted nonlinear components automatically. Experiments demonstrate the excellent performance and efficiency of our kTDSEP algorithm for several problems of nonlinear BSS and for more than two sources.

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PDF Web DOI [BibTex]

PDF Web DOI [BibTex]


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Tractable Inference for Probabilistic Data Models

Csato, L., Opper, M., Winther, O.

Complexity, 8(4):64-68, April 2003 (article)

Abstract
We present an approximation technique for probabilistic data models with a large number of hidden variables, based on ideas from statistical physics. We give examples for two nontrivial applications. © 2003 Wiley Periodicals, Inc.

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PDF GZIP Web [BibTex]

PDF GZIP Web [BibTex]


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Feature selection and transduction for prediction of molecular bioactivity for drug design

Weston, J., Perez-Cruz, F., Bousquet, O., Chapelle, O., Elisseeff, A., Schölkopf, B.

Bioinformatics, 19(6):764-771, April 2003 (article)

Abstract
Motivation: In drug discovery a key task is to identify characteristics that separate active (binding) compounds from inactive (non-binding) ones. An automated prediction system can help reduce resources necessary to carry out this task. Results: Two methods for prediction of molecular bioactivity for drug design are introduced and shown to perform well in a data set previously studied as part of the KDD (Knowledge Discovery and Data Mining) Cup 2001. The data is characterized by very few positive examples, a very large number of features (describing three-dimensional properties of the molecules) and rather different distributions between training and test data. Two techniques are introduced specifically to tackle these problems: a feature selection method for unbalanced data and a classifier which adapts to the distribution of the the unlabeled test data (a so-called transductive method). We show both techniques improve identification performance and in conjunction provide an improvement over using only one of the techniques. Our results suggest the importance of taking into account the characteristics in this data which may also be relevant in other problems of a similar type.

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Web [BibTex]


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Rademacher and Gaussian averages in Learning Theory

Bousquet, O.

Universite de Marne-la-Vallee, March 2003 (talk)

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PDF [BibTex]

PDF [BibTex]


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Use of the Zero-Norm with Linear Models and Kernel Methods

Weston, J., Elisseeff, A., Schölkopf, B., Tipping, M.

Journal of Machine Learning Research, 3, pages: 1439-1461, March 2003 (article)

Abstract
We explore the use of the so-called zero-norm of the parameters of linear models in learning. Minimization of such a quantity has many uses in a machine learning context: for variable or feature selection, minimizing training error and ensuring sparsity in solutions. We derive a simple but practical method for achieving these goals and discuss its relationship to existing techniques of minimizing the zero-norm. The method boils down to implementing a simple modification of vanilla SVM, namely via an iterative multiplicative rescaling of the training data. Applications we investigate which aid our discussion include variable and feature selection on biological microarray data, and multicategory classification.

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PDF PostScript PDF [BibTex]

PDF PostScript PDF [BibTex]


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Introduction: Robots with Cognition?

Franz, MO.

6, pages: 38, (Editors: H.H. Bülthoff, K.R. Gegenfurtner, H.A. Mallot, R. Ulrich, F.A. Wichmann), 6. T{\"u}binger Wahrnehmungskonferenz (TWK), February 2003 (talk)

Abstract
Using robots as models of cognitive behaviour has a long tradition in robotics. Parallel to the historical development in cognitive science, one observes two major, subsequent waves in cognitive robotics. The first is based on ideas of classical, cognitivist Artificial Intelligence (AI). According to the AI view of cognition as rule-based symbol manipulation, these robots typically try to extract symbolic descriptions of the environment from their sensors that are used to update a common, global world representation from which, in turn, the next action of the robot is derived. The AI approach has been successful in strongly restricted and controlled environments requiring well-defined tasks, e.g. in industrial assembly lines. AI-based robots mostly failed, however, in the unpredictable and unstructured environments that have to be faced by mobile robots. This has provoked the second wave in cognitive robotics which tries to achieve cognitive behaviour as an emergent property from the interaction of simple, low-level modules. Robots of the second wave are called animats as their architecture is designed to closely model aspects of real animals. Using only simple reactive mechanisms and Hebbian-type or evolutionary learning, the resulting animats often outperformed the highly complex AI-based robots in tasks such as obstacle avoidance, corridor following etc. While successful in generating robust, insect-like behaviour, typical animats are limited to stereotyped, fixed stimulus-response associations. If one adopts the view that cognition requires a flexible, goal-dependent choice of behaviours and planning capabilities (H.A. Mallot, Kognitionswissenschaft, 1999, 40-48) then it appears that cognitive behaviour cannot emerge from a collection of purely reactive modules. It rather requires environmentally decoupled structures that work without directly engaging the actions that it is concerned with. This poses the current challenge to cognitive robotics: How can we build cognitive robots that show the robustness and the learning capabilities of animats without falling back into the representational paradigm of AI? The speakers of the symposium present their approaches to this question in the context of robot navigation and sensorimotor learning. In the first talk, Prof. Helge Ritter introduces a robot system for imitation learning capable of exploring various alternatives in simulation before actually performing a task. The second speaker, Angelo Arleo, develops a model of spatial memory in rat navigation based on his electrophysiological experiments. He validates the model on a mobile robot which, in some navigation tasks, shows a performance comparable to that of the real rat. A similar model of spatial memory is used to investigate the mechanisms of territory formation in a series of robot experiments presented by Prof. Hanspeter Mallot. In the last talk, we return to the domain of sensorimotor learning where Ralf M{\"o}ller introduces his approach to generate anticipatory behaviour by learning forward models of sensorimotor relationships.

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Web [BibTex]

Web [BibTex]


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An Introduction to Variable and Feature Selection.

Guyon, I., Elisseeff, A.

Journal of Machine Learning, 3, pages: 1157-1182, 2003 (article)

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[BibTex]

[BibTex]


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Dynamics of a rigid body in a Stokes fluid

Gonzalez, O., Graf, ABA., Maddocks, JH.

Journal of Fluid Mechanics, 2003 (article) Accepted

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[BibTex]

[BibTex]


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A novel transient heater-foil technique for liquid crystal experiments on film cooled surfaces

Vogel, G., Graf, ABA., von Wolfersdorf, J., Weigand, B.

ASME Journal of Turbomachinery, 125, pages: 529-537, 2003 (article)

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PDF [BibTex]

PDF [BibTex]


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Microarrays: How Many Do You Need?

Zien, A., Fluck, J., Zimmer, R., Lengauer, T.

Journal of Computational Biology, 10(3-4):653-667, 2003 (article)

Abstract
We estimate the number of microarrays that is required in order to gain reliable results from a common type of study: the pairwise comparison of different classes of samples. We show that current knowledge allows for the construction of models that look realistic with respect to searches for individual differentially expressed genes and derive prototypical parameters from real data sets. Such models allow investigation of the dependence of the required number of samples on the relevant parameters: the biological variability of the samples within each class, the fold changes in expression that are desired to be detected, the detection sensitivity of the microarrays, and the acceptable error rates of the results. We supply experimentalists with general conclusions as well as a freely accessible Java applet at www.scai.fhg.de/special/bio/howmanyarrays/ for fine tuning simulations to their particular settings.

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Web [BibTex]

Web [BibTex]


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New Approaches to Statistical Learning Theory

Bousquet, O.

Annals of the Institute of Statistical Mathematics, 55(2):371-389, 2003 (article)

Abstract
We present new tools from probability theory that can be applied to the analysis of learning algorithms. These tools allow to derive new bounds on the generalization performance of learning algorithms and to propose alternative measures of the complexity of the learning task, which in turn can be used to derive new learning algorithms.

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PostScript [BibTex]

PostScript [BibTex]


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Gene expression in chondrocytes assessed with use of microarrays

Aigner, T., Zien, A., Hanisch, D., Zimmer, R.

Journal of Bone and Joint Surgery, 85(Suppl 2):117-123, 2003 (article)

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[BibTex]

[BibTex]


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New electro-optic effect: Sum-frequency generation from optically active liquids in the presence of a dc electric field

Fischer, P., Buckingham, A., Beckwitt, K., Wiersma, D., Wise, F.

PHYSICAL REVIEW LETTERS, 91(17), 2003 (article)

Abstract
We report the observation of sum-frequency signals that depend linearly on an applied electrostatic field and that change sign with the handedness of an optically active solute. This recently predicted chiral electro-optic effect exists in the electric-dipole approximation. The static electric field gives rise to an electric-field-induced sum-frequency signal (an achiral third-order process) that interferes with the chirality-specific sum-frequency at second order. The cross-terms linear in the electrostatic field constitute the effect and may be used to determine the absolute sign of second- and third-order nonlinear-optical susceptibilities in isotropic media.

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DOI [BibTex]

DOI [BibTex]


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Chiral and achiral contributions to sum-frequency generation from optically active solutions of binaphthol

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

JOURNAL OF PHYSICAL CHEMISTRY A, 107(40):8232-8238, 2003 (article)

Abstract
The nonlinear sum- and difference-frequency generation spectroscopies can be probes of molecular chirality in optically active systems. We present a tensorial analysis of the chirality-specific electric-dipolar sum-frequency-generation susceptibility and the achiral electric-quadrupolar and magnetic-dipolar nonlinearities at second order in isotropic media. The chiral and achiral contributions to the sum-frequency signal from the bulk of optically active solutions of 1,1'-bi-2-naphthol (2,2'-dehydroxy-1,1'-binaphthyl) can be distinguished, and the former dominates. Ab initio computations reveal the dramatic resonance enhancement that the isotropic component of the electric-dipolar three-wave mixing hyperpolarizability experiences. Away from resonance its magnitude rapidly decreases, as-unlike the vector component-it is zero in the static limit. The dispersion of the first hyperpolarizability is computed by a configuration interaction singles sum-over-states approach with explicit regard to the Franck-Condon active vibrational substructure for all resonant electronic states.

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DOI [BibTex]

DOI [BibTex]


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Synthetic gecko foot-hair micro/nano-structures as dry adhesives

Sitti, M., Fearing, R. S.

Journal of adhesion science and technology, 17(8):1055-1073, Taylor & Francis Group, 2003 (article)

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Project Page [BibTex]

Project Page [BibTex]


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Teleoperated touch feedback from the surfaces at the nanoscale: modeling and experiments

Sitti, M., Hashimoto, H.

IEEE/ASME transactions on mechatronics, 8(2):287-298, IEEE, 2003 (article)

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[BibTex]

[BibTex]


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Mixing in Cu/Ge system by swift heavy ions

Kumar, S., Chauhan, R. S., Singh, R. P., Kabiraj, D., Sahoo, P. K., Rumbolz, C., Srivastava, S. K., Bolse, W., Avasthi, D. K.

{Nuclear Instruments \& Methods in Physics Research Section B-Beam Interactions with Materials and Atoms}, 212, pages: 242-245, 2003 (article)

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[BibTex]

[BibTex]


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Magnetic properties of [NdFeBx/Nbz]n multilayer films

Tsai, J. L., Chin, T. S., Yao, Y. D., Melsheimer, A., Fischer, S. F., Dragon, T., Kelsch, M., Kronmüller, H.

{Journal of Applied Physics}, 93(10):6915-6917, 2003 (article)

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[BibTex]

[BibTex]


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Analysis of the temperature dependence of the coercive field of Sm2Co17 based magnets

Kronmüller, H., Goll, D.

{Scripta Materialia}, 48(7):833-838, 2003 (article)

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[BibTex]

[BibTex]


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NMR studies of hydrogen motion in nanostructured hydrogen-graphite systems

Majer, G., Stanik, E., Orimo, S.

{Journal of Alloys and Compounds}, 356-357, pages: 617-621, 2003 (article)

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[BibTex]

[BibTex]


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Hydrogen diffusion in metallic and nanostructured materials

Majer, G., Eberle, U., Kimmerle, F., Stanik, E., Orimo, S.

{Physica B}, 328, pages: 81-89, 2003 (article)

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[BibTex]

[BibTex]


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Electron density-of-states and the metal-insulator transition in LaHx

Barnes, R. G., Chang, C. T., Majer, G., Kaess, U.

{Journal of Alloys and Compounds}, 356-357, pages: 137-141, 2003 (article)

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[BibTex]

[BibTex]


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Electronic sputtering from HOPG: A study of angular dependence

Tripathi, A., Khan, S. A., Srivastava, S. K., Kumar, M., Kumar, S., Rao, S. V. S. N., Lakshmi, G. B. V. S., Siddiqui, A. M., Bajwa, N., Nagaraja, H. S., Mittal, V. K., Szökefalvi, A., Kurth, M., Pandey, A. C., Avasthi, D. K., Carstanjen, H. D.

{Nuclear Instruments and Methods B}, 212, pages: 402-406, 2003 (article)

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[BibTex]

[BibTex]


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Stress-induced relaxation mechanisms in single-crystalline titanomagnetites

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

{Journal of Physics-Condensed Matter}, 15(41):7029-7045, 2003 (article)

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[BibTex]

[BibTex]


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Morphology and interdiffusion behavior of evaporated metal films on crystalline diindenoperylene thin films

Dürr, A. C., Schreiber, F., Kelsch, M., Carstanjen, H. D., Dosch, H., Seeck, O. H.

{Journal of Applied Physics}, 93(9):5201-5209, 2003 (article)

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[BibTex]

[BibTex]


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Recent progress with high resolution X-ray microscopy at the XM-1

Denbeaux, G., Schneider, G., Pearson, A., Chao, W., Bates, B., Harteneck, B., Olynick, D., Anderson, E., Fischer, P., Juenger, M.

{Journal de Physique IV}, 104, pages: 9-9, 2003 (article)

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[BibTex]

[BibTex]


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Comment on the analysis of angle-dependent X-ray magnetic circular dichroism in systems with reduced dimensionality

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

{Journal of Electron Spectroscopy and Related Phenomena}, 130(1-3):97-100, 2003 (article)

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[BibTex]

[BibTex]


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The electron theory of magnetism in monoatomic nanowires

Komelj, M., Ederer, C., Fähnle, M.

{Advances in Solid State Science}, 43, pages: 781-788, 2003 (article)

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[BibTex]

[BibTex]


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Nuclear relaxation in the dideuteride of hafnium and titanium

Majer, G., Gottwald, J., Peterson, D. T., Barnes, R. G.

{Physical Review B}, 68, 2003 (article)

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[BibTex]

[BibTex]


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Magnetism in systems with various dimensionalities: A comparison between Fe and Co

Ederer, C., Komelj, M., Fähnle, M.

{Physical Review B}, 68, 2003 (article)

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[BibTex]

[BibTex]


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Scaled teleoperation system for nano-scale interaction and manipulation

Sitti, M., Aruk, B., Shintani, H., Hashimoto, H.

Advanced Robotics, 17(3):275-291, Taylor & Francis Group, 2003 (article)

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[BibTex]

[BibTex]


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Atomic force microscope probe based controlled pushing for nano-tribological characterization

Sitti, M.

IEEE/ASME Transactions on Mechatronics, 8(3), 2003 (article)

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[BibTex]


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Characterization of free volumes in amorphous and nanostructured Pr2Fe14B using positron lifetime spectroscopy

Wu, Y. C., Ye, F., Barbe, V., Sprengel, W., Reimann, K., Reichle, K. J., Goll, D., Würschum, R., Schaefer, H. E.

{Physica Status Solidi A-Applied Research}, 198(1):204-209, 2003 (article)

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[BibTex]

[BibTex]


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The magnetization behavior of nanocrystalline permanent magnets based on the Stoner-Wohlfarth model

Zhang, H. W., Zhang, S. Y., Shen, B. G., Kronmüller, H.

{Journal of Magnetism and Magnetic Materials}, 260(3):352-360, 2003 (article)

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[BibTex]

[BibTex]


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X-ray magnetic microscopy for correlations between magnetic domains and crystal structure

Denbeaux, G., Anderson, E., Bates, B., Chao, W., Liddle, J. A., Harteneck, B., Pearson, A., Salmassi, F., Schneider, G., Fischer, P., Eimüller, T., Taylor, S., Chang, H., Kusinski, G. J.

{Journal de Physique IV}, 104, pages: 477-481, 2003 (article)

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[BibTex]

[BibTex]


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Statistical mechanics of inhomogeneous model colloid-polymer mixtures

Brader, J. M., Evans, R., Schmidt, M.

{Molecular Physics}, 101, pages: 3349-3384, 2003 (article)

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[BibTex]

[BibTex]


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Cluster expansion technique: An efficient tool to search for ground-state configurations of adatoms on plane surfaces

Drautz, R., Singer, R., Fähnle, M.

{Physical Review B}, 67, 2003 (article)

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[BibTex]


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Hydrogen strorage in carbon nanotubes

Becher, M., Haluska, M., Hirscher, M., Quintel, A., Skakalova, V., Dettlaff-Weglikovska, U., Chen, X., Hulman, M., Choi, Y., Roth, S., Meregalli, V., Parrinello, M., Ströbel, R., Jörissen, L., Kappes, M., Fink, J., Züttel, A., Stepanek, I., Bernier, P.

{Comptes Rendus Physique}, 4, pages: 1055-1062, 2003 (article)

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[BibTex]

[BibTex]


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Thermal desorption spectroscopy as a quantitative tool to determine the hydrogen content in solids

von Zeppelin, F., Haluska, M., Hirscher, M.

{Thermochimica Acta}, 404, pages: 251-258, 2003 (article)

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[BibTex]

[BibTex]