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2011


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Collective dynamics of colloids at fluid interfaces

Bleibel, J., Dominguez, A., Oettel, M., Dietrich, S.

European Physical Journal E, 34(11), 2011 (article)

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DOI [BibTex]

2011


DOI [BibTex]


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Anomalous transport of a tracer on percolating clusters

Spanner, M., Höfling, F., Schröder-Turk, G. E., Mecke, K., Franosch, T.

Journal of Physics: Condensed Matter, 23(23), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Dynamics of colloids in confined geometries

Almenar, L., Rauscher, M.

Journal of Physics: Condensed Matter, 23(18), 2011 (article)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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The structure and melting transition of two-dimensional colloidal alloys

Law, A. D., Horozov, T. S., Buzza, D. M. A.

Soft Matter, 7(19):8923-8931, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Second harmonic light scattering from spherical polyelectrolyte brushes

Schürer, B., Hoffmann, M., Wunderlich, S., Harnau, L., Peschel, U., Ballauff, M., Peukert, W.

Journal of Physical Chemistry C, 115, pages: 18302-18309, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Simulation einer fast kritischen binären Flüssigkeit in einem Temperaturgradienten

Single, F.

Universität Stuttgart, Stuttgart, 2011 (mastersthesis)

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[BibTex]

[BibTex]


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Solvation forces in Ising films with long-range boundary fields: density-matrix renormalization-group study

Drzewinski, A., Maciolek, A., Barasinski, A.

Molecular Physics, 109(7-10):1133-1141, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Pulling and pushing a cargo with a catalytically active carrier

Popescu, M. N., Tasinkevych, M., Dietrich, S.

Europhysics Letters, 95(2), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Critical Casimir forces for Ising films with variable boundary fields

Vasilyev, O., Maciolek, A., Dietrich, S.

Physical Review E, 84(4), 2011 (article)

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DOI [BibTex]


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Study of \pi\pi correlations at LHC and RHIC energies in pp collisions within the quark-gluon string model

Nilsson, M. S., Bravina, L. V., Zabrodin, E. E., Malinina, L. V., Bleibel, J.

Physical Review D, 84(5), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Micro-rheology on (polymer-grafted) colloids using optical tweezers

Gutsche, C., Elmahdy, M. M., Kegler, K., Semenov, I., Stangner, T., Otto, O., Ueberschär, O., Keyser, U. F., Krüger, M., Rauscher, M., Weeber, R., Harting, J., Kim, Y. W., Lobaskin, V., Netz, R., Kremer, F.

Journal of Physics: Condensed Matter, 23(18), IOP Publishing, Bristol, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Debye-Scherrer rings from block copolymer films with powder-like order

Busch, P., Rauscher, M., Moulin, J.-F., Müller-Buschbaum, P.

Journal of Applied Crystallography, 44(2):370-379, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Effective interactions and equilibrium configurations of colloidal particles on a sessile droplet

Guzowski, J., Tasinkevych, M., Dietrich, S.

Soft Matter, 7(9):4189-4197, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Capillary interactions in Pickering emulsions

Guzowski, J., Tasinkevych, M., Dietrich, S.

Physical Review E, 84(3), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Critical Casimir forces steered by patterned substrates

Gambassi, A., Dietrich, S.

Soft Matter, 7(4):1247-1253, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Interaction strength between proteins and polyelectrolyte brushes: A small angle X-ray scattering study

Henzler, K., Haupt, B., Rosenfeldt, S., Harnau, L., Narayanan, T., Ballauff, M.

Physical Chemistry Chemical Physics, 13, pages: 17599-17605, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Annealing of single lamella nanoparticles of polyethylene

Rochette, C. N., Rosenfeldt, S., Henzler, K., Polzer, F., Ballauff, M., Tong, Q., Mecking, S., Drechsler, M., Narayanan, T., Harnau, L.

Macromolecules, 44(12):4845-4851, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Struktur dichter ionischer Flüssigkeiten

Dannenmann, O.

Universität Stuttgart, Stuttgart, 2011 (mastersthesis)

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[BibTex]

[BibTex]


The Oxidation of Fe(111)
The Oxidation of Fe(111)

Davies, R., Edwards, D., Gräfe, J., Gilbert, L., Davies, P., Hutchings, G., Bowker, M.

Surface Science, 605(17-18):1754-1762, 2011 (article)

Abstract
The oxidation of Fe(111) was studied using Auger electron spectroscopy (AES), low energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), ion scattering spectroscopy (ISS) and scanning tunnelling microscopy (STM). Oxidation of the crystal was found to be a very fast process, even at 200 K, and the Auger O signal saturation level is reached within ~ 50 × 10− 6 mbar s. Annealing the oxidised surface at 773 K causes a significant decline in apparent surface oxygen concentration and produces a clear (6 × 6) LEED pattern, whereas after oxidation at ambient temperature no pattern was observed. STM results indicate that the oxygen signal was reduced due to the nucleation of large, but sparsely distributed oxide islands, leaving mainly the smooth (6 × 6) structure between the islands. The reactivity of the (6 × 6) layer towards methanol was investigated using temperature programmed desorption (TPD), which showed mainly decomposition to CO and CO2, due to the production of formate intermediates on the surface. Interestingly, this removes the (6 × 6) structure by reduction, but it can be reformed from the sink of oxygen present in the large oxide islands simply by annealing at 773 K for a few minutes. The (6 × 6) appears to be a relatively stable, pseudo-oxide phase, that may be useful as a model oxide surface.

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DOI [BibTex]

DOI [BibTex]


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Trapping colloids near chemical stripes via critical Casimir forces

Tröndle, M., Zvyagolskaya, O., Gambassi, A., Vogt, D., Harnau, L., Bechinger, C., Dietrich, S.

Molecular Physics, 109, pages: 1169-1185, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Electrostatic interactions in critical solvents

Bier, M., Gambassi, A., Oettel, M., Dietrich, S.

Europhysics Letters, 95, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Structural investigation of thin diblock copolymer films using time-of-flight grazing-incidence small-angle neutron scattering

Metwalli, E., Moulin, J.-F., Rauscher, M., Kaune, G., Ruderer, M. A., Van Bürck, U., Haese-Seiller, M., Kampmann, R., Müller-Buschbaum, P.

Journal of Applied Crystallography, 44(1):84-92, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Complexation of beta-lactoglobulin fibrils and sulfated polysaccharides

Jones, O. G., Handschin, S., Adamcik, J., Harnau, L., Bolisetty, S., Mezzenga, R.

Biomacromolecules, 12, pages: 3056-3065, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Parallelisierung Stokesscher Dynamik für Graphikprozessoren zur Simulation kolloidaler Suspensionen

Kopp, M.

Universität Stuttgart, Stuttgart, 2011 (mastersthesis)

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[BibTex]

[BibTex]


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Diffusion in Wandnähe

Müller, J.

Universität Stuttgart, Stuttgart, 2011 (mastersthesis)

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[BibTex]

[BibTex]


High-resolution x-ray absorption spectroscopy of BaTiO${}_{3}$: Experiment and first-principles calculations
High-resolution x-ray absorption spectroscopy of BaTiO_3: Experiment and first-principles calculations

Chassé, A., Borek, S., Schindler, K., Trautmann, M., Huth, M., Steudel, F., Makhova, L., Gräfe, J., Denecke, R.

Physical Review B, 84, pages: 195135, 2011 (article)

Abstract
High resolution x-ray absorption spectroscopy (XAS) affords new insight into the microscopic properties of perovskite transition metal oxides. Interpretation of XAS spectra in transition metal oxides requires theoretical tools capable of describing relativistic and many-body effects. In this work, full relativistic (SPR-KKR) and multiplet calculations (CTM4XAS) are carried out and compared to experimental multiedge XAS spectra of BaTiO3 single crystals. The impact of relativistic and many-body effects on the calculated density of states and x-ray absorption near edge structure spectra are individually considered.

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DOI [BibTex]

DOI [BibTex]


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Magnetization of multicomponent ferrofluids

Szalai, I., Dietrich, S.

Journal of Physics: Condensed Matter, 23(32), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Space-resolved dynamics of a tracer in a disordered solid

Franosch, T., Spanner, M., Bauer, T., Schröder-Turk, G. E., Höfling, F.

Journal of Non-Crystalline Solids, 357(2):472-478, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Long-wavelength anomalies in the asymptotic behavior of mode-coupling theory

Schnyder, S. K., Höfling, F., Franosch, T., Voigtmann, T.

Journal of Physics: Condensed Matter, 23(23), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Ferromagnetism of ZnO influenced by physical and chemical treatment

Chen, Y.

Universität Stuttgart, Stuttgart, 2011 (mastersthesis)

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[BibTex]

[BibTex]


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Herstellung und Charakterisierung von ultradünnen, funktionellen CoFeB Filmen

Streckenbach, F.

Hochschule Esslingen / Hochschule Aalen, Esslingen / Aalen, 2011 (mastersthesis)

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[BibTex]

[BibTex]


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Hydrogen adsorption on metal-organic frameworks

Streppel, B.

Universität Stuttgart, Stuttgart, 2011 (phdthesis)

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link (url) [BibTex]

link (url) [BibTex]


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Electron theory of fast and ultrafast dissipative magnetization dynamics

Fähnle, M., Illg, C.

{Journal of Physics: Condensed Matter}, 23, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Large-area hard magnetic L10-FePt nanopatterns by nanoimprint lithography

Bublat, T., Goll, D.

{Nanotechnology}, 22(31), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Hydrogen storage by cryoadsorption in ultrahigh-porosity metal-organic frameworks

Hirscher, M.

{Angewandte Chemie International Edition}, 50(3):581-582, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Amorphous grain boundary layers in the ferromagnetic nanograined ZnO films

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

In 520, pages: 1192-1194, Hersonissos, Greece, 2011 (inproceedings)

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DOI [BibTex]

DOI [BibTex]


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Multilayer Fresnel zone plate for soft X-ray microscopy resolves sub-39 nm structures

Mayer, M., Grévent, C., Szeghalmi, A., Knez, M., Weigand, M., Rehbein, S., Schneider, G., Baretzky, B., Schütz, G.

{Ultramicroscopy}, 111, pages: 1706-1711, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Generalized Gilbert equation including inertial damping: derivation from an extended breathing Fermi surface model

Fähnle, M., Steiauf, D., Illg, C.

{Physical Review B}, 84, 2011 (article)

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DOI [BibTex]


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Hydrogen physisorption in high SSA microporous materials - A comparison between AX-21\textunderscore33 and MOF-177 at cryogenic conditions

Schlichtenmayer, M., Streppel, B., Hirscher, M.

{International Journal of Hydrogen Energy}, 36, pages: 586-591, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Inversed solid-phase grain boundary wetting in the Al-Zn system

Protasova, S. G., Kogtenkova, O. A., Straumal, B. B., Zieba, P., Baretzky, B.

In 46, pages: 4349-4353, Mie, Japan, 2011 (inproceedings)

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DOI [BibTex]

DOI [BibTex]


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Magnetic vortex core reversal by excitation of spin waves

Kammerer, M., Weigand, M., Curcic, M., Noske, M., Sproll, M., Vansteenkiste, A., Van Waeyenberge, B., Stoll, H., Woltersdorf, G., Back, C. H., Schütz, G.

{Nature Communications}, 2, pages: 279-284, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Toward simple control for complex, autonomous robotic applications: combining discrete and rhythmic motor primitives

Degallier, S., Righetti, L., Gay, S., Ijspeert, A.

Autonomous Robots, 31(2-3):155-181, October 2011 (article)

Abstract
Vertebrates are able to quickly adapt to new environments in a very robust, seemingly effortless way. To explain both this adaptivity and robustness, a very promising perspective in neurosciences is the modular approach to movement generation: Movements results from combinations of a finite set of stable motor primitives organized at the spinal level. In this article we apply this concept of modular generation of movements to the control of robots with a high number of degrees of freedom, an issue that is challenging notably because planning complex, multidimensional trajectories in time-varying environments is a laborious and costly process. We thus propose to decrease the complexity of the planning phase through the use of a combination of discrete and rhythmic motor primitives, leading to the decoupling of the planning phase (i.e. the choice of behavior) and the actual trajectory generation. Such implementation eases the control of, and the switch between, different behaviors by reducing the dimensionality of the high-level commands. Moreover, since the motor primitives are generated by dynamical systems, the trajectories can be smoothly modulated, either by high-level commands to change the current behavior or by sensory feedback information to adapt to environmental constraints. In order to show the generality of our approach, we apply the framework to interactive drumming and infant crawling in a humanoid robot. These experiments illustrate the simplicity of the control architecture in terms of planning, the integration of different types of feedback (vision and contact) and the capacity of autonomously switching between different behaviors (crawling and simple reaching).

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Learning Force Control Policies for Compliant Manipulation

Kalakrishnan, M., Righetti, L., Pastor, P., Schaal, S.

In 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems, pages: 4639-4644, IEEE, San Francisco, USA, sep 2011 (inproceedings)

Abstract
Developing robots capable of fine manipulation skills is of major importance in order to build truly assistive robots. These robots need to be compliant in their actuation and control in order to operate safely in human environments. Manipulation tasks imply complex contact interactions with the external world, and involve reasoning about the forces and torques to be applied. Planning under contact conditions is usually impractical due to computational complexity, and a lack of precise dynamics models of the environment. We present an approach to acquiring manipulation skills on compliant robots through reinforcement learning. The initial position control policy for manipulation is initialized through kinesthetic demonstration. We augment this policy with a force/torque profile to be controlled in combination with the position trajectories. We use the Policy Improvement with Path Integrals (PI2) algorithm to learn these force/torque profiles by optimizing a cost function that measures task success. We demonstrate our approach on the Barrett WAM robot arm equipped with a 6-DOF force/torque sensor on two different manipulation tasks: opening a door with a lever door handle, and picking up a pen off the table. We show that the learnt force control policies allow successful, robust execution of the tasks.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Control of legged robots with optimal distribution of contact forces

Righetti, L., Buchli, J., Mistry, M., Schaal, S.

In 2011 11th IEEE-RAS International Conference on Humanoid Robots, pages: 318-324, IEEE, Bled, Slovenia, 2011 (inproceedings)

Abstract
The development of agile and safe humanoid robots require controllers that guarantee both high tracking performance and compliance with the environment. More specifically, the control of contact interaction is of crucial importance for robots that will actively interact with their environment. Model-based controllers such as inverse dynamics or operational space control are very appealing as they offer both high tracking performance and compliance. However, while widely used for fully actuated systems such as manipulators, they are not yet standard controllers for legged robots such as humanoids. Indeed such robots are fundamentally different from manipulators as they are underactuated due to their floating-base and subject to switching contact constraints. In this paper we present an inverse dynamics controller for legged robots that use torque redundancy to create an optimal distribution of contact constraints. The resulting controller is able to minimize, given a desired motion, any quadratic cost of the contact constraints at each instant of time. In particular we show how this can be used to minimize tangential forces during locomotion, therefore significantly improving the locomotion of legged robots on difficult terrains. In addition to the theoretical result, we present simulations of a humanoid and a quadruped robot, as well as experiments on a real quadruped robot that demonstrate the advantages of the controller.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Learning Motion Primitive Goals for Robust Manipulation

Stulp, F., Theodorou, E., Kalakrishnan, M., Pastor, P., Righetti, L., Schaal, S.

In IEEE/RSJ International Conference on Intelligent Robots and Systems, pages: 325-331, IEEE, San Francisco, USA, sep 2011 (inproceedings)

Abstract
Applying model-free reinforcement learning to manipulation remains challenging for several reasons. First, manipulation involves physical contact, which causes discontinuous cost functions. Second, in manipulation, the end-point of the movement must be chosen carefully, as it represents a grasp which must be adapted to the pose and shape of the object. Finally, there is uncertainty in the object pose, and even the most carefully planned movement may fail if the object is not at the expected position. To address these challenges we 1) present a simplified, computationally more efficient version of our model-free reinforcement learning algorithm PI2; 2) extend PI2 so that it simultaneously learns shape parameters and goal parameters of motion primitives; 3) use shape and goal learning to acquire motion primitives that are robust to object pose uncertainty. We evaluate these contributions on a manipulation platform consisting of a 7-DOF arm with a 4-DOF hand.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Inverse Dynamics Control of Floating-Base Robots with External Constraints: a Unified View

Righetti, L., Buchli, J., Mistry, M., Schaal, S.

In 2011 IEEE International Conference on Robotics and Automation, pages: 1085-1090, IEEE, Shanghai, China, 2011 (inproceedings)

Abstract
Inverse dynamics controllers and operational space controllers have proved to be very efficient for compliant control of fully actuated robots such as fixed base manipulators. However legged robots such as humanoids are inherently different as they are underactuated and subject to switching external contact constraints. Recently several methods have been proposed to create inverse dynamics controllers and operational space controllers for these robots. In an attempt to compare these different approaches, we develop a general framework for inverse dynamics control and show that these methods lead to very similar controllers. We are then able to greatly simplify recent whole-body controllers based on operational space approaches using kinematic projections, bringing them closer to efficient practical implementations. We also generalize these controllers such that they can be optimal under an arbitrary quadratic cost in the commands.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Piezo driven strain effects on magneto-crystalline anisotropy

Badr, E.

Universität Stuttgart, Stuttgart, 2011 (mastersthesis)

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[BibTex]

[BibTex]


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Magnetooptische Untersuchungen an granularen und beschichteten MgB2 Filmen

Stahl, C.

Universität Stuttgart, Stuttgart, 2011 (mastersthesis)

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[BibTex]

[BibTex]


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Mikromagnetismus der Wechselwirkung von Spinwellen mit Domänenwänden in Ferromagneten

Macke, S.

Universität Stuttgart, Stuttgart, 2011 (phdthesis)

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[BibTex]

[BibTex]