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2002


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Contrast discrimination with pulse-trains in pink noise

Henning, G., Bird, C., Wichmann, F.

Journal of the Optical Society of America A, 19(7), pages: 1259-1266, 2002 (article)

Abstract
Detection performance was measured with sinusoidal and pulse-train gratings. Although the 2.09-c/deg pulse-train, or line gratings, contained at least 8 harmonics all at equal contrast, they were no more detectable than their most detectable component. The addition of broadband pink noise designed to equalize the detectability of the components of the pulse train made the pulse train about a factor of four more detectable than any of its components. However, in contrast-discrimination experiments, with a pedestal or masking grating of the same form and phase as the signal and 15% contrast, the noise did not affect the discrimination performance of the pulse train relative to that obtained with its sinusoidal components. We discuss the implications of these observations for models of early vision in particular the implications for possible sources of internal noise.

ei

PDF [BibTex]

2002


PDF [BibTex]


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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]

PostScript DOI [BibTex]


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Optimal linear estimation of self-motion - a real-world test of a model of fly tangential neurons

Franz, MO.

SAB 02 Workshop, Robotics as theoretical biology, 7th meeting of the International Society for Simulation of Adaptive Behaviour (SAB), (Editors: Prescott, T.; Webb, B.), 2002 (poster)

Abstract
The tangential neurons in the fly brain are sensitive to the typical optic flow patterns generated during self-motion (see example in Fig.1). We examine whether a simplified linear model of these neurons can be used to estimate self-motion from the optic flow. We present a theory for the construction of an optimal linear estimator incorporating prior knowledge both about the distance distribution of the environment, and about the noise and self-motion statistics of the sensor. The optimal estimator is tested on a gantry carrying an omnidirectional vision sensor that can be moved along three translational and one rotational degree of freedom. The experiments indicate that the proposed approach yields accurate results for rotation estimates, independently of the current translation and scene layout. Translation estimates, however, turned out to be sensitive to simultaneous rotation and to the particular distance distribution of the scene. The gantry experiments confirm that the receptive field organization of the tangential neurons allows them, as an ensemble, to extract self-motion from the optic flow.

ei

PDF [BibTex]

PDF [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]


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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.

pf

DOI [BibTex]

DOI [BibTex]


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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.

pf

DOI [BibTex]

DOI [BibTex]


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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.

pf

[BibTex]

[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]


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Learning robot control

Schaal, S.

In The handbook of brain theory and neural networks, 2nd Edition, pages: 983-987, 2, (Editors: Arbib, M. A.), MIT Press, Cambridge, MA, 2002, clmc (inbook)

Abstract
This is a review article on learning control in robots.

am

link (url) [BibTex]

link (url) [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)

mms

[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)

mms

[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)

mms

[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)

mms

[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)

mms

[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)

mms

[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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Arm and hand movement control

Schaal, S.

In The handbook of brain theory and neural networks, 2nd Edition, pages: 110-113, 2, (Editors: Arbib, M. A.), MIT Press, Cambridge, MA, 2002, clmc (inbook)

Abstract
This is a review article on computational and biological research on arm and hand control.

am

link (url) [BibTex]

link (url) [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]


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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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Rumpfniveau-Photoemissions-Spektroskopie an Platinclustern auf HOPG

Schneider, N.

Würzburg, 2002 (misc)

mms

[BibTex]


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Photoelektronenspektroskopie an deponierten Nickelclustern

Wiesner, B.

Würzburg, 2002 (misc)

mms

[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)

mms

[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)

mms

[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)

mms

[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]


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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]


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The initial stages of oxidation of γ-TiAl: an X-ray photoelectron study

Schmiedgen, M., Graat, P. C. J., Baretzky, B., Mittemeijer, E. J.

{Thin Solid Films}, 415(1-2):114-122, 2002 (article)

mms

[BibTex]

[BibTex]


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Morphology and thermal stability of metal contacts on crystalline organic thin films

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

{Advanced Materials}, 14(13-14):961-963, 2002 (article)

mms

[BibTex]

[BibTex]


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Magnetic Imaging of Nanostructured Systems with Transmission X-Ray Microscopy

Eimüller, T.

Bayrische Julius-Maximilians-Universität Würzburg, Würzburg, 2002 (phdthesis)

mms

[BibTex]

[BibTex]


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Magnetic anisotropy of textured CrO2 thin films investigated by X-ray magnetic circular dichroism

Goering, E., Justen, M., Geissler, J., Rüdiger, U., Rabe, M., Güntherodt, G., Schütz, G.

{Applied Physics A-Materials Science \& Processing}, 74(6):747-753, 2002 (article)

mms

[BibTex]

[BibTex]