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2009


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Fast subtree kernels on graphs

Shervashidze, N., Borgwardt, K.

In Advances in Neural Information Processing Systems 22, pages: 1660-1668, (Editors: Bengio, Y. , D. Schuurmans, J. Lafferty, C. Williams, A. Culotta), Curran, Red Hook, NY, USA, 23rd Annual Conference on Neural Information Processing Systems (NIPS), 2009 (inproceedings)

Abstract
In this article, we propose fast subtree kernels on graphs. On graphs with n nodes and m edges and maximum degree d, these kernels comparing subtrees of height h can be computed in O(mh), whereas the classic subtree kernel by Ramon & G{\"a}rtner scales as O(n24dh). Key to this efficiency is the observation that the Weisfeiler-Lehman test of isomorphism from graph theory elegantly computes a subtree kernel as a byproduct. Our fast subtree kernels can deal with labeled graphs, scale up easily to large graphs and outperform state-of-the-art graph kernels on several classification benchmark datasets in terms of accuracy and runtime.

ei

PDF Web [BibTex]

2009


PDF Web [BibTex]


Full phase and amplitude control in computer-generated holography
Full phase and amplitude control in computer-generated holography

Fratz, M., Fischer, P., Giel, D. M.

OPTICS LETTERS, 34(23):3659-3661, 2009 (article)

Abstract
We report what we believe to be the first realization of a computer-generated complex-valued hologram recorded in a single film of photoactive polymer. Complex-valued holograms give rise to a diffracted optical field with control over its amplitude and phase. The holograms are generated by a one-step direct laser writing process in which a spatial light modulator (SLM) is imaged onto a polymer film. Temporal modulation of the SLM during exposure controls both the strength of the induced birefringence and the orientation of the fast axis. We demonstrate that complex holograms can be used to impart arbitrary amplitude and phase profiles onto a beam and thereby open new possibilities in the control of optical beams. (C) 2009 Optical Society of America

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[BibTex]

[BibTex]


Digital polarization holograms with defined magnitude and orientation of each pixel's birefringence
Digital polarization holograms with defined magnitude and orientation of each pixel’s birefringence

Fratz, M., Giel, D. M., Fischer, P.

OPTICS LETTERS, 34(8):1270-1272, 2009 (article)

Abstract
A new form of digital polarization holography is demonstrated that permits both the amplitude and the phase of a diffracted beam to be independently controlled. This permits two independent intensity images to be stored in the same hologram. To fabricate the holograms, a birefringence with defined retardance and orientation of the fast axis is recorded into a photopolymer film. The holograms are selectively read out by choosing the polarization state of the read beam. Polarization holograms of this kind increase the data density in holographic data storage and allow higher quality diffractive optical elements to be written. (C) 2009 Optical Society of America

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[BibTex]


Controlled Propulsion of Artificial Magnetic Nanostructured Propellers
Controlled Propulsion of Artificial Magnetic Nanostructured Propellers

Ghosh, A., Fischer, P.

NANO LETTERS, 9(6):2243-2245, 2009, Featured highlight ‘Nanotechnology: The helix that delivers’ Nature 459, 13 (2009). (article)

Abstract
For biomedical applications, such as targeted drug delivery and microsurgery, it is essential to develop a system of swimmers that can be propelled wirelessly in fluidic environments with good control. Here, we report the construction and operation of chiral colloidal propellers that can be navigated in water with micrometer-level precision using homogeneous magnetic fields. The propellers are made via nanostructured surfaces and can be produced in large numbers. The nanopropellers can carry chemicals, push loads, and act as local probes in rheological measurements.

Featured highlight ‘Nanotechnology: The helix that delivers’ Nature 459, 13 (2009).

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Video - Nanospropellers DOI [BibTex]

Video - Nanospropellers DOI [BibTex]


Absolute Asymmetric Reduction Based on the Relative Orientation of Achiral Reactants
Absolute Asymmetric Reduction Based on the Relative Orientation of Achiral Reactants

Kuhn, A., Fischer, P.

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 48(37):6857-6860, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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One-dimensional phthalocyanine nanostructures directed by gold templates

Krauss, T. N., Barrena, E., Lohmüller, T., Kelsch, M., Breitling, A., Van Aken, P. A., Spatz, J., Dosch, H.

{Chemistry of Materials}, 21, pages: 5010-5015, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Near-edge X-ray absorption fine-structure microscopy of organic and magnetic materials

Ade, H., Stoll, H.

{Nature Materials}, 8, pages: 281-290, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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X-ray imaging of the dynamic magnetic vortex core deformation

Vansteenkiste, A., Chou, K. W., Weigand, M., Curcic, M., Sackmann, V., Stoll, H., Tyliszczak, T., Woltersdorf, G., Back, C. H., Schütz, G., Van Waeyenberge, B.

{Nature Physics}, 5, pages: 332-334, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Order\textendashdisorder transition and valence state of ytterbium in YbAuxGa2-x(0.26 \textless\textequalsx \textless\textequals1.31)

Gumeniuk, R., Bischoff, E., Burkhardt, U., Prots, Y., Schnelle, W., Vasylechko, L., Schmidt, M., Kuzma, Y., Grin, Y.

{Journal of Solid State Chemistry}, 182(12):3374-3382, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Coercivity of ledge-type L10-FePt/Fe nanocomposites with perpendicular magnetization

Goll, D., Breitling, A.

{Applied Physics Letters}, 94, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Time-resolved X-ray microscopy of nanoparticle aggregates under oscillatory shear

Auernhammer, G. K., Fauth, K., Ullrich, B., Zhao, J., Weigand, M., Vollmer, D.

{Journal of Synchrotron Radiation}, 16, pages: 307-309, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Micromagnetism of advanced hard magnetic materials

Kronmüller, H., Goll, D.

{International Journal of Materials Research}, 100, pages: 640-651, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Confinement of MgH2 nanoclusters within nanoporous aerogel scaffold materials

Nielsen, T. K., Manickam, K., Hirscher, M., Besenbacher, F., Jensen, T. R.

{American Chemical Society Nano}, 3(11):3521-3528, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Possible definition of atom- and bond-resolved contributions to the magnetocrystalline anisotropy energy

Subkow, S., Fähnle, M.

{Physical Review B}, 80, 2009 (article)

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DOI [BibTex]


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Complex magnetic phase in submonolayer Fe stripes on Pt(977)

Honolka, J., Lee, T. Y., Kuhnke, K., Repetto, D., Sessi, V., Wahl, P., Buchsbaum, A., Varga, P., Gardonio, S., Carbone, C., Krishnakumar, S. R., Gambardella, P., Komelj, M., Singer, R., Fähnle, M., Fauth, K., Schütz, G., Enders, A., Kern, K.

{Physical Review B}, 79, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Local and nonlocal atomic contributions to unit-cell damping in near-adiabatic collinear magnetization dynamics

Seib, J., Steiauf, D., Fähnle, M.

{Physical Review B}, 79, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Temperature-dependent critical currents in superconducting YBa2Cu3O7-δand ferromagnetic La2/3Ca1/3MnO3 hybrid structures

Djupmyr, M., Soltan, S., Habermeier, H.-U., Albrecht, J.

{Physical Review B}, 80, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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High surface area polyHIPEs with hierarchical pore system

Schwab, M. G., Senkovska, I., Rose, M., Klein, N., Koch, M., Pahnke, J., Jonschker, G., Schmitz, B., Hirscher, M., Kaskel, S.

{Soft Matter}, 5, pages: 1055-1059, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Grain boundary wetting phase transformations in the Zn-Sn and Zn-In systems

Gornakova, A. S., Straumal, B. B., Tsurekawa, S., Chang, L.-S., Nekrasov, A. N.

{Reviews on Advanced Materials Science}, 21(1):18-26, 2009 (article)

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[BibTex]

[BibTex]


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Magnetization study of nanograined pure and Mn-doped ZnO films: formation of a ferromagnetic grain-boundary foam

Straumal, B. B., Mazilkin, A. A., Protasova, S. G., Myatiev, A. A., Straumal, P. B., Schütz, G., van Aken, P. A., Goering, E., Baretzky, B.

{Physical Review B}, 79, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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In situ synthesis and hydrogen storage properties of PdNi alloy nanoparticles in an ordered mesoporous carbon template

Campesi, R., Cuevas, F., Leroy, E., Hirscher, M., Gadiou, R., Vix-Guterl, C., Latroche, M.

{Microporous and Mesoporous Materials}, 117, pages: 511-514, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Mit Röntgenblitzen zu neuen Erkenntnissen

Hedderich, R., Weigand, M., Baretzky, B.

{Nanotechnik - Molek\"ule Materialien Mikrosysteme}, (6 (Beilage zu Photonik 41. 2009)), 2009 (article)

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[BibTex]

[BibTex]


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Second-order faceting-roughening of the tilt grain boundary in zinc

Straumal, B. B., Gornakova, A. S., Sursaeva, V. G., Yashnikov, V. P.

{International Journal of Materials Research}, 100(4):525-529, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Improvement of interface structure and magnetic properties of Co on Si (100) by surfactant (Sb) mediated growth

Dash, S. P., Goll, D., Carstanjen, H. D.

{Applied Physics A}, 97(3):651-656, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Effect of severe plastic deformation on the coercivity of Co-Cu alloys

Straumal, B. B., Protasova, S. G., Mazilkin, A. A., Baretzky, B., Goll, D., Gunderov, D. V., Valiev, R. Z.

{Philosophical Magazine Letters}, 89(10):649-654, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetic properties of cobalt-covered MgB2 films

Treiber, S., Stuhlhofer, B., Habermeier, H.-U., Albrecht, J.

{Superconductor Science and Technology}, 22, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Reconstruction of historic alloys for pipe organs brings true Baroque music back to life

Baretzky, B., Friesel, M., Straumal, B.

{Japan Organist}, 36, pages: 29-38, 2009 (article)

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[BibTex]

[BibTex]


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Exchange-coupled L10-FePt/Fe composite patterns with perpendicular magnetization

Breitling, A., Bublat, T., Goll, D.

{Physica Status Solidi - Rapid Research Letters}, 3(5):130-132, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Proton NMR studies of the NaAlH4 structure

Valiente-Banuet, L. E., Majer, G., Müller, K.

{Journal of Magnetic Resonance}, 200, pages: 280-284, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetism of FePt surface alloys

Honolka, J., Lee, T. Y., Kuhnke, K., Enders, A., Skomski, R., Bornemann, S., Mankovsky, S., Minár, J., Staunton, J., Ebert, H., Hessler, M., Fauth, K., Schütz, G., Buchsbaum, A., Schmid, M., Varga, P., Kern, K.

{Physical Review Letters}, 102(6), 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Enhanced 95Zr diffusion in grain boundaries of nano-crystalline ZrO2 \mbox⋅ 9.5 mol\textpercent Y2O3

Drings, H., Brossmann, U., Carstanjen, H. D., Szökefalvi-Nagy, A., Noll, C., Schaefer, H.-E.

{Physica Status Solidi (A)}, 206(1):54-58, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetism of nanostructured materials for advanced magnetic recording

Goll, D.

{International Journal of Materials Research}, 100, pages: 652-662, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Vortex core switching by coherent excitation with single in-plane magnetic field pulses

Weigand, M., van Waeyenberge, B., Vansteenkiste, A., Curcic, M., Sackmann, V., Stoll, H., Tyliszczak, T., Kaznatcheev, K., Bertwistle, D., Woltersdorf, G., Back, C. H., Schütz, G.

{Physical Review Letters}, 102, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Increase of Mn solubility with decreasing grain size in ZnO

Straumal, B., Baretzky, B., Mazilkin, A., Protasova, S., Myatiev, A., Straumal, P.

{Journal of the European Ceramic Society}, 29(10):1963-1970, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Fe-C nanograined alloys obtained by high-pressure torsion: Structure and magnetic properties

Straumal, B. B., Mazilkin, A. A., Protasova, S. G., Dobatkin, S. V., Rodin, A. O., Baretzky, B., Goll, D., Schütz, G.

{Materials Science and Engineering A}, 503, pages: 185-189, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Chiral symmetry breaking of magnetic vortices by sample roughness

Vansteenkiste, A., Weigand, M., Curcic, M., Stoll, H., Schütz, G., Van Waeyenberge, B.

{New Journal of Physics}, 11, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Extended s-d model for magnetization dynamics of strongly noncollinear configurations

De Angeli, L., Steiauf, D., Singer, R., Köberle, I., Dietermann, F., Fähnle, M.

{Physical Review B}, 79, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Superconducting phase formation in random neck syntheses: a study of the Y-Ba-Cu-O system by magneto-optics and magnetometry

Willems, J. B., Albrecht, J., Landau, I. L., Hulliger, J.

{Superconductor Science and Technology}, 22, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Determination of spin moments from magnetic EXAFS

Popescu, V., Gü\ssmann, M., Fähnle, M., Schütz, G.

{Physical Review B}, 79, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Linewidth of ferromagnetic resonance for systems with anisotropic damping

Seib, J., Steiauf, D., Fähnle, M.

{Physical Review B}, 79, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Structural and magnetic deconvolution of FePt/FeOx-nanoparticles using x-ray magnetic circular dichroism

Nolle, D., Goering, E., Tietze, T., Schütz, G., Figuerola, A., Manna, L.

{New Journal of Physics}, 11, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetic imaging with femtosecond temporal resolution

Li, J., Lee, M.-S., He, W., Redeker, B., Remhof, A., Amaladass, E., Hassel, C., Eimüller, T.

{Review of Scientific Instruments}, 80(7), 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Elliott-Yafet mechanism and the discussion of femtosecond magnetization dynamics

Steiauf, D., Fähnle, M.

{Physical Review B}, 79, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Investigation of the stability of Mn12 single molecule magnets

Voss, S., Fonin, M., Burova, L., Burgert, M., Dedkov, Y. S., Preobrajenski, A. B., Goering, E., Groth, U., Kaul, A. R., Ruediger, U.

{Applied Physics A}, 94(3):491-495, 2009 (article)

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DOI [BibTex]

DOI [BibTex]

2007


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A Tutorial on Spectral Clustering

von Luxburg, U.

Statistics and Computing, 17(4):395-416, December 2007 (article)

Abstract
In recent years, spectral clustering has become one of the most popular modern clustering algorithms. It is simple to implement, can be solved efficiently by standard linear algebra software, and very often outperforms traditional clustering algorithms such as the k-means algorithm. On the first glance spectral clustering appears slightly mysterious, and it is not obvious to see why it works at all and what it really does. The goal of this tutorial is to give some intuition on those questions. We describe different graph Laplacians and their basic properties, present the most common spectral clustering algorithms, and derive those algorithms from scratch by several different approaches. Advantages and disadvantages of the different spectral clustering algorithms are discussed.

ei

PDF PDF DOI [BibTex]

2007


PDF PDF DOI [BibTex]


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A Tutorial on Kernel Methods for Categorization

Jäkel, F., Schölkopf, B., Wichmann, F.

Journal of Mathematical Psychology, 51(6):343-358, December 2007 (article)

Abstract
The abilities to learn and to categorize are fundamental for cognitive systems, be it animals or machines, and therefore have attracted attention from engineers and psychologists alike. Modern machine learning methods and psychological models of categorization are remarkably similar, partly because these two fields share a common history in artificial neural networks and reinforcement learning. However, machine learning is now an independent and mature field that has moved beyond psychologically or neurally inspired algorithms towards providing foundations for a theory of learning that is rooted in statistics and functional analysis. Much of this research is potentially interesting for psychological theories of learning and categorization but also hardly accessible for psychologists. Here, we provide a tutorial introduction to a popular class of machine learning tools, called kernel methods. These methods are closely related to perceptrons, radial-basis-function neural networks and exemplar theories of catego rization. Recent theoretical advances in machine learning are closely tied to the idea that the similarity of patterns can be encapsulated in a positive definite kernel. Such a positive definite kernel can define a reproducing kernel Hilbert space which allows one to use powerful tools from functional analysis for the analysis of learning algorithms. We give basic explanations of some key concepts—the so-called kernel trick, the representer theorem and regularization—which may open up the possibility that insights from machine learning can feed back into psychology.

ei

PDF Web DOI [BibTex]

PDF Web DOI [BibTex]


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Accurate Splice site Prediction Using Support Vector Machines

Sonnenburg, S., Schweikert, G., Philips, P., Behr, J., Rätsch, G.

BMC Bioinformatics, 8(Supplement 10):1-16, December 2007 (article)

Abstract
Background: For splice site recognition, one has to solve two classification problems: discriminating true from decoy splice sites for both acceptor and donor sites. Gene finding systems typically rely on Markov Chains to solve these tasks. Results: In this work we consider Support Vector Machines for splice site recognition. We employ the so-called weighted degree kernel which turns out well suited for this task, as we will illustrate in several experiments where we compare its prediction accuracy with that of recently proposed systems. We apply our method to the genome-wide recognition of splice sites in Caenorhabditis elegans, Drosophila melanogaster, Arabidopsis thaliana, Danio rerio, and Homo sapiens. Our performance estimates indicate that splice sites can be recognized very accurately in these genomes and that our method outperforms many other methods including Markov Chains, GeneSplicer and SpliceMachine. We provide genome-wide predictions of splice sites and a stand-alone prediction tool ready to be used for incorporation in a gene finder. Availability: Data, splits, additional information on the model selection, the whole genome predictions, as well as the stand-alone prediction tool are available for download at http:// www.fml.mpg.de/raetsch/projects/splice.

ei

PDF DOI [BibTex]

PDF DOI [BibTex]


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Towards compliant humanoids: an experimental assessment of suitable task space position/orientation controllers

Nakanishi, J., Mistry, M., Peters, J., Schaal, S.

In IROS 2007, 2007, pages: 2520-2527, (Editors: Grant, E. , T. C. Henderson), IEEE Service Center, Piscataway, NJ, USA, IEEE/RSJ International Conference on Intelligent Robots and Systems, November 2007 (inproceedings)

Abstract
Compliant control will be a prerequisite for humanoid robotics if these robots are supposed to work safely and robustly in human and/or dynamic environments. One view of compliant control is that a robot should control a minimal number of degrees-of-freedom (DOFs) directly, i.e., those relevant DOFs for the task, and keep the remaining DOFs maximally compliant, usually in the null space of the task. This view naturally leads to task space control. However, surprisingly few implementations of task space control can be found in actual humanoid robots. This paper makes a first step towards assessing the usefulness of task space controllers for humanoids by investigating which choices of controllers are available and what inherent control characteristics they have—this treatment will concern position and orientation control, where the latter is based on a quaternion formulation. Empirical evaluations on an anthropomorphic Sarcos master arm illustrate the robustness of the different controllers as well as the eas e of implementing and tuning them. Our extensive empirical results demonstrate that simpler task space controllers, e.g., classical resolved motion rate control or resolved acceleration control can be quite advantageous in face of inevitable modeling errors in model-based control, and that well chosen formulations are easy to implement and quite robust, such that they are useful for humanoids.

ei

PDF Web DOI [BibTex]

PDF Web DOI [BibTex]


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Performance Stabilization and Improvement in Graph-based Semi-supervised Learning with Ensemble Method and Graph Sharpening

Choi, I., Shin, H.

In Korean Data Mining Society Conference, pages: 257-262, Korean Data Mining Society, Seoul, Korea, Korean Data Mining Society Conference, November 2007 (inproceedings)

ei

PDF [BibTex]

PDF [BibTex]