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2004


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Formation of nanograined structure and decomposition of supersaturated solid solution during high pressure torsion of Al-Zn and Al-Mg alloys

Straumal, B. B., Baretzky, B., Mazilkin, A. A., Phillipp, F., Kogtenkova, O. A., Volkov, M. N., Valiev, R. Z.

{Acta Materialia}, 52, pages: 4469-4478, 2004 (article)

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[BibTex]

2004


[BibTex]


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Ab-initio modeling of nonlinear magnetoelastic coupling in epitaxial films

Komelj, M., Fähnle, M.

{Journal of Magnetism and Magnetic Materials}, 272-276, pages: e1587-e1588, 2004 (article)

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[BibTex]

[BibTex]


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Atomic force microscope probe based controlled pushing for nanotribological characterization

Sitti, M.

IEEE/ASME Transactions on mechatronics, 9(2):343-349, IEEE, 2004 (article)

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[BibTex]

[BibTex]


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Effective exchange interaction in a quasi-two-dimensional self-assembled nanoparticle array

Wiedwald, U., Cerchez, M., Farle, M., Fauth, K., Schütz, G., Zürn, K., Boyen, H., Ziemann, P.

{Physical Review B}, 70, 2004 (article)

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DOI [BibTex]

DOI [BibTex]


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How well does total electron yield measure x-ray absorption in nanoparticles?

Fauth, K.

{Applied Physics Letters}, 85(15):3271-3273, 2004 (article)

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DOI [BibTex]

DOI [BibTex]


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Ordering and magnetism in Fe-Co: Dense sequence of ground-state structures

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

{Physical Review Letters}, 93(6), 2004 (article)

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[BibTex]

[BibTex]


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Thermal reversal of elongated ferromagnetic particles misoriented to the applied field

Goll, D., Bertram, H. N.

{IEEE Transactions on Magnetics}, 40(4):2416-2418, 2004 (article)

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[BibTex]

[BibTex]


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Anisotropy of the orbital moments and the magnetic dipole term Tz in CrO2: An ab-initio study

Komelj, M., Ederer, C., Fähnle, M.

{Physical Review B}, 69, 2004 (article)

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[BibTex]

[BibTex]


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Core-shell iron-iron oxide nanoparticles: magnetic properties and interactions

Theil-Kuhn, L., Bojesen, A., Timmermann, L., Fauth, K., Goering, E. J., Johnson, E., Meedom Nielsen, M., Morup, S.

{Journal of Magnetism and Magnetic Materials}, 272-276, pages: 1485-1486, 2004 (article)

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[BibTex]

[BibTex]


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Measurement of very low bulk concentrations (below 1 atppm) of hydrogen using ERDA

Tripathi, A., Kruse, O., Carstanjen, H. D.

{Nuclear Instruments and Methods B}, 219-220, pages: 435-439, 2004 (article)

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[BibTex]

[BibTex]


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Unusual doublet structure in proton magnetic-resonance spectra of yttrium and lutetium trihydrides

Majer, G., Telfah, A., Grinberg, F., Barnes, R. G.

{Physical Review B}, 70(13), 2004 (article)

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[BibTex]

[BibTex]


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Kinetics of primary nanocrystallization in Al-rich metallic glass with quenched-in nuclei

Wang, J. Q., Zhang, H. W., Gu, X. J., Lu, K., Sommer, F., Mittemeijer, E.

{Materials Science and Engineering A}, 375-377, pages: 980-984, 2004 (article)

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[BibTex]

[BibTex]


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3-dimensional Wulff diagrams for \Sigma3 grain boundaries in Cu

Straumal, B., Kucherinenko, Y., Baretzky, B.

{Reviews on Advanced Materials Science}, 7(1):23-31, 2004 (article)

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)

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[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)

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[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)

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[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)

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[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)

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[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.}

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[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.

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link (url) [BibTex]

link (url) [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)

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[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)

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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)

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[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)

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[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)

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[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)

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[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)

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[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)

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[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]

1996


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Estimating optical flow in segmented images using variable-order parametric models with local deformations

Black, M. J., Jepson, A.

IEEE Transactions on Pattern Analysis and Machine Intelligence, 18(10):972-986, October 1996 (article)

Abstract
This paper presents a new model for estimating optical flow based on the motion of planar regions plus local deformations. The approach exploits brightness information to organize and constrain the interpretation of the motion by using segmented regions of piecewise smooth brightness to hypothesize planar regions in the scene. Parametric flow models are estimated in these regions in a two step process which first computes a coarse fit and estimates the appropriate parameterization of the motion of the region (two, six, or eight parameters). The initial fit is refined using a generalization of the standard area-based regression approaches. Since the assumption of planarity is likely to be violated, we allow local deformations from the planar assumption in the same spirit as physically-based approaches which model shape using coarse parametric models plus local deformations. This parametric+deformation model exploits the strong constraints of parametric approaches while retaining the adaptive nature of regularization approaches. Experimental results on a variety of images indicate that the parametric+deformation model produces accurate flow estimates while the incorporation of brightness segmentation provides precise localization of motion boundaries.

ps

pdf pdf from publisher [BibTex]

1996


pdf pdf from publisher [BibTex]


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On the unification of line processes, outlier rejection, and robust statistics with applications in early vision

Black, M., Rangarajan, A.

International Journal of Computer Vision , 19(1):57-92, July 1996 (article)

Abstract
The modeling of spatial discontinuities for problems such as surface recovery, segmentation, image reconstruction, and optical flow has been intensely studied in computer vision. While “line-process” models of discontinuities have received a great deal of attention, there has been recent interest in the use of robust statistical techniques to account for discontinuities. This paper unifies the two approaches. To achieve this we generalize the notion of a “line process” to that of an analog “outlier process” and show how a problem formulated in terms of outlier processes can be viewed in terms of robust statistics. We also characterize a class of robust statistical problems for which an equivalent outlier-process formulation exists and give a straightforward method for converting a robust estimation problem into an outlier-process formulation. We show how prior assumptions about the spatial structure of outliers can be expressed as constraints on the recovered analog outlier processes and how traditional continuation methods can be extended to the explicit outlier-process formulation. These results indicate that the outlier-process approach provides a general framework which subsumes the traditional line-process approaches as well as a wide class of robust estimation problems. Examples in surface reconstruction, image segmentation, and optical flow are presented to illustrate the use of outlier processes and to show how the relationship between outlier processes and robust statistics can be exploited. An appendix provides a catalog of common robust error norms and their equivalent outlier-process formulations.

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pdf pdf from publisher DOI [BibTex]


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The robust estimation of multiple motions: Parametric and piecewise-smooth flow fields

Black, M. J., Anandan, P.

Computer Vision and Image Understanding, 63(1):75-104, January 1996 (article)

Abstract
Most approaches for estimating optical flow assume that, within a finite image region, only a single motion is present. This single motion assumption is violated in common situations involving transparency, depth discontinuities, independently moving objects, shadows, and specular reflections. To robustly estimate optical flow, the single motion assumption must be relaxed. This paper presents a framework based on robust estimation that addresses violations of the brightness constancy and spatial smoothness assumptions caused by multiple motions. We show how the robust estimation framework can be applied to standard formulations of the optical flow problem thus reducing their sensitivity to violations of their underlying assumptions. The approach has been applied to three standard techniques for recovering optical flow: area-based regression, correlation, and regularization with motion discontinuities. This paper focuses on the recovery of multiple parametric motion models within a region, as well as the recovery of piecewise-smooth flow fields, and provides examples with natural and synthetic image sequences.

ps

pdf pdf from publisher [BibTex]

pdf pdf from publisher [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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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]