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2014


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Pole Balancing with Apollo

Holger Kaden

Eberhard Karls Universität Tübingen, December 2014 (mastersthesis)

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[BibTex]

2014


[BibTex]


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Finite-size scaling study of shear viscosity anomaly at liquid-liquid criticality

Roy, S., Das, S. K.

The Journal of Chemical Physics, 141(23), December 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Wenn es was zu sagen gibt

(Klaus Tschira Award 2014 in Computer Science)

Trimpe, S.

Bild der Wissenschaft, pages: 20-23, November 2014, (popular science article in German) (article)

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PDF Project Page [BibTex]

PDF Project Page [BibTex]


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Robotics and Neuroscience

Floreano, Dario, Ijspeert, Auke Jan, Schaal, S.

Current Biology, 24(18):R910-R920, sep 2014 (article)

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[BibTex]

[BibTex]


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Learning Coupling Terms for Obstacle Avoidance

Rai, A.

École polytechnique fédérale de Lausanne, August 2014 (mastersthesis)

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Project Page [BibTex]

Project Page [BibTex]


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Object Tracking in Depth Images Using Sigma Point Kalman Filters

Issac, J.

Karlsruhe Institute of Technology, July 2014 (mastersthesis)

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Project Page [BibTex]

Project Page [BibTex]


Robot Arm Pose Estimation through Pixel-Wise Part Classification
Robot Arm Pose Estimation through Pixel-Wise Part Classification

Bohg, J., Romero, J., Herzog, A., Schaal, S.

In IEEE International Conference on Robotics and Automation (ICRA) 2014, pages: 3143-3150, IEEE International Conference on Robotics and Automation (ICRA), June 2014 (inproceedings)

Abstract
We propose to frame the problem of marker-less robot arm pose estimation as a pixel-wise part classification problem. As input, we use a depth image in which each pixel is classified to be either from a particular robot part or the background. The classifier is a random decision forest trained on a large number of synthetically generated and labeled depth images. From all the training samples ending up at a leaf node, a set of offsets is learned that votes for relative joint positions. Pooling these votes over all foreground pixels and subsequent clustering gives us an estimate of the true joint positions. Due to the intrinsic parallelism of pixel-wise classification, this approach can run in super real-time and is more efficient than previous ICP-like methods. We quantitatively evaluate the accuracy of this approach on synthetic data. We also demonstrate that the method produces accurate joint estimates on real data despite being purely trained on synthetic data.

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video code pdf DOI Project Page [BibTex]

video code pdf DOI Project Page [BibTex]


Nonmyopic View Planning for Active Object Classification and Pose Estimation
Nonmyopic View Planning for Active Object Classification and Pose Estimation

Atanasov, N., Sankaran, B., Le Ny, J., Pappas, G., Daniilidis, K.

IEEE Transactions on Robotics, May 2014, clmc (article)

Abstract
One of the central problems in computer vision is the detection of semantically important objects and the estimation of their pose. Most of the work in object detection has been based on single image processing and its performance is limited by occlusions and ambiguity in appearance and geometry. This paper proposes an active approach to object detection by controlling the point of view of a mobile depth camera. When an initial static detection phase identifies an object of interest, several hypotheses are made about its class and orientation. The sensor then plans a sequence of viewpoints, which balances the amount of energy used to move with the chance of identifying the correct hypothesis. We formulate an active M-ary hypothesis testing problem, which includes sensor mobility, and solve it using a point-based approximate POMDP algorithm. The validity of our approach is verified through simulation and real-world experiments with the PR2 robot. The results suggest a significant improvement over static object detection

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Web pdf link (url) [BibTex]

Web pdf link (url) [BibTex]


Data-Driven Grasp Synthesis - A Survey
Data-Driven Grasp Synthesis - A Survey

Bohg, J., Morales, A., Asfour, T., Kragic, D.

IEEE Transactions on Robotics, 30, pages: 289 - 309, IEEE, April 2014 (article)

Abstract
We review the work on data-driven grasp synthesis and the methodologies for sampling and ranking candidate grasps. We divide the approaches into three groups based on whether they synthesize grasps for known, familiar or unknown objects. This structure allows us to identify common object representations and perceptual processes that facilitate the employed data-driven grasp synthesis technique. In the case of known objects, we concentrate on the approaches that are based on object recognition and pose estimation. In the case of familiar objects, the techniques use some form of a similarity matching to a set of previously encountered objects. Finally for the approaches dealing with unknown objects, the core part is the extraction of specific features that are indicative of good grasps. Our survey provides an overview of the different methodologies and discusses open problems in the area of robot grasping. We also draw a parallel to the classical approaches that rely on analytic formulations.

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PDF link (url) DOI Project Page [BibTex]

PDF link (url) DOI Project Page [BibTex]


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Local Gaussian Regression

Meier, F., Hennig, P., Schaal, S.

arXiv preprint, March 2014, clmc (misc)

Abstract
Abstract: Locally weighted regression was created as a nonparametric learning method that is computationally efficient, can learn from very large amounts of data and add data incrementally. An interesting feature of locally weighted regression is that it can work with ...

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Web link (url) [BibTex]

Web link (url) [BibTex]


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A Self-Tuning LQR Approach Demonstrated on an Inverted Pendulum

Trimpe, S., Millane, A., Doessegger, S., D’Andrea, R.

In Proceedings of the 19th IFAC World Congress, Cape Town, South Africa, 2014 (inproceedings)

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PDF Supplementary material DOI [BibTex]

PDF Supplementary material DOI [BibTex]


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Learning objective functions for autonomous motion generation

Kalakrishnan, M.

University of Southern California, University of Southern California, Los Angeles, CA, 2014 (phdthesis)

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Project Page Project Page [BibTex]

Project Page Project Page [BibTex]


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Ultracompact Three-Dimensional Tubular Conductivity Microsensors for Ionic and Biosensing Applications

Martinez-Cisneros, C. S., Sanchez, S., Schmidt, O. G., Xi, W.

Nano Letters, pages: 2219-2224, American Chemical Society, Washington, DC, 2014 (article)

Abstract
We present ultracompact three-dimensional tubular structures integrating Au-based electrodes as impedimetric microsensors for the in-flow determination of mono- and divalent ionic species and HeLa cells. The microsensors show an improved performance of 2 orders of magnitude (limit of detection \textequals 0.1 nM for KCl) compared to conventional planar conductivity detection systems integrated in microfluidic platforms and the capability to detect single HeLa cells in flowing phosphate buffered saline. These highly integrated conductivity tubular sensors thus open new possibilities for lab-in-a-tube devices for bioapplications such as biosensing and bioelectronics.

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DOI [BibTex]

DOI [BibTex]


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Catalytic nanomotors for environmental monitoring and water remediation

Soler, L., Sanchez, S.

Nanoscale, 6(13):7175-7182, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Proton-proton collisions at ultra-relativistic energies in quark-gluon string model

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

EPJ Web of Conferences, 70, EDP Sciences, Les Ulis, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Hydrodynamic interactions induce anomalous diffusion under partial confinement

Bleibel, J., Dominguez, A., Günther, F., Harting, J., Oettel, M.

Soft Matter, 10(17):2945-2948, Royal Society of Chemistry, Cambridge, UK, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Clay nanotube encapsulation for functional biocomposites

Lvov, Y., Aerov, Artem A., Aerov, A. A., Fakhrullin, R.

Advances in Colloid and Interface Science, 207, pages: 189-198, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Wetting phenomena in electrolyte solutions

Ibagon, I.

Universität Stuttgart, Stuttgart, 2014 (phdthesis)

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link (url) [BibTex]

link (url) [BibTex]


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A Limiting Property of the Matrix Exponential

Trimpe, S., D’Andrea, R.

IEEE Transactions on Automatic Control, 59(4):1105-1110, 2014 (article)

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PDF DOI [BibTex]

PDF DOI [BibTex]


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Learning coupling terms for obstacle avoidance

Rai, A., Meier, F., Ijspeert, A., Schaal, S.

In International Conference on Humanoid Robotics, pages: 512-518, IEEE, 2014, clmc (inproceedings)

Abstract
Autonomous manipulation in dynamic environments is important for robots to perform everyday tasks. For this, a manipulator should be capable of interpreting the environment and planning an appropriate movement. At least, two possible approaches exist for this in literature. Usually, a planning system is used to generate a complex movement plan that satisfies all constraints. Alternatively, a simple plan could be chosen and modified with sensory feedback to accommodate additional constraints by equipping the controller with features that remain dormant most of the time, except when specific situations arise. Dynamic Movement Primitives (DMPs) form a robust and versatile starting point for such a controller that can be modified online using a non-linear term, called the coupling term. This can prove to be a fast and reactive way of obstacle avoidance in a human-like fashion. We propose a method to learn this coupling term from human demonstrations starting with simple features and making it more robust to avoid a larger range of obstacles. We test the ability of our coupling term to model different kinds of obstacle avoidance behaviours in humans and use this learnt coupling term to avoid obstacles in a reactive manner. This line of research aims at pushing the boundary of reactive control strategies to more complex scenarios, such that complex and usually computationally more expensive planning methods can be avoided as much as possible.

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link (url) Project Page [BibTex]

link (url) Project Page [BibTex]


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Control of Self-Propelled Microjets Inside a Microchannel With Time-Varying Flow Rates

Magdanz, V., Sanchez, S., Schmidt, O. G., Khalil, I. S. M., Misra, S.

IEEE Transactions on Robotics and Automation, pages: 49-58, IEEE, New York, NY, 2014 (article)

Abstract
We demonstrate the closed-loop motion control of self-propelled microjets inside a fluidic microchannel. The motion control of the microjets is achieved in hydrogen peroxide solution with time-varying flow rates, under the influence of the controlled magnetic fields and the self-propulsion force. Magnetic dipole mo- ment of the microjets is characterized using the U-turn and the rotating field techniques. The characterized magnetic dipole mo- ment has an average of 1.4 $\times$ 10 \textminus 13 A.m 2 at magnetic field, linear velocity, and boundary frequency of 2 mT, 100 $\mu$ m/s, and 25 rad/s, respectively. We implement a closed-loop control system that is based on the characterized magnetic dipole moment of the mi- crojets. This closed-loop control system positions the microjets by directing the magnetic field lines toward the reference position. Experiments are done using a magnetic system and a fluidic mi- crochannel with a width of 500 $\mu$ m. In the absence of a fluid flow, our control system positions the microjets at an average velocity and within an average region-of-convergence (ROC) of 119 $\mu$ m/s and 390 $\mu$ m, respectively. As a representative case, we observe that our control system positions the microjets at an average velocity and within an average ROC of 90 $\mu$ m/s and 600 $\mu$ m and 120 $\mu$ m/s and 600 $\mu$ m when a flow rate of 2.5 $\mu$ l/min is applied against and along the direction of the microjets, respectively. Furthermore, the average velocity and ROC are determined throughout the flow range (0 to 7.5 $\mu$ l/min) to characterize the motion of the microjets inside the microchannel

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DOI [BibTex]

DOI [BibTex]


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Electrostatic interaction between colloidal particles trapped at an electrolyte interface

Majee, A., Bier, M., Dietrich, S.

The Journal of Chemical Physics, 140(16), American Institute of Physics, Woodbury, N.Y., 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Capillary attraction induced collapse of colloidal monolayers at fluid interfaces

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

Soft Matter, 10(23):4091-4109, Royal Society of Chemistry, Cambridge, UK, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Trapping self-propelled micromotors with microfabricated chevron and heart-shaped chips

Restrepo-Pérez, L., Soler, L., Mart\’\inez-Cisneros, C. S., Sanchez, S., Schmidt, O. G.

Lab on a Chip, 14(9):1515-1518, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Order of wetting transitions in electrolyte solutions

Ibagon, I., Bier, M., Dietrich, S.

The Journal of Chemical Physics, 140(17), American Institute of Physics, Woodbury, N.Y., 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Specific salt effects on thermophoresis of charged colloids

Eslahian, K. A., Majee, A., Maskos, M., Würger, A.

Soft Matter, 10(12):1931-1936, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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H5MD: A structured, efficient, and portable file format for molecular data

De Buyl, P., Colberg, P. H., Höfling, F.

Computer Physics Communications, 185(6):1546-1553, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Emergent Long-Range Couplings in Arrays of Fluid Cells

Abraham, D. B., Maciolek, A., Vasilyev, O.

Physical Review Letters, 113(7), American Physical Society, Woodbury, N.Y., 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Event-Based State Estimation With Variance-Based Triggering

Trimpe, S., D’Andrea, R.

IEEE Transactions on Automatic Control, 59(12):3266-3281, 2014 (article)

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PDF Supplementary material DOI Project Page [BibTex]

PDF Supplementary material DOI Project Page [BibTex]


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Effective interaction between a colloid and a soft interface near criticality

Law, A. D., Harnau, L., Tröndle, M., Dietrich, S.

The Journal of Chemical Physics, 141(13), 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Tubular micro- nanorobots: smart design for bio-related applications

Sanchez, S., Wang, X., Solovev, A. A., Soler, L., Magdanz, V., Schmidt, O. G.

In Small-Scale Robotics, 8336, pages: 16-27, Lecture Notes in Computer Science, Springer, Karlsruhe, 2014 (inproceedings)

Abstract
We designed microrobots in the form of autonomous and remotely guided microtubes. One of the challenges at small scales is the effective conversion of energy into mechanical force to overcome the high viscosity of the fluid at low Reynolds numbers. This can be achieved by integration of catalytic nano-materials and processes to decompose chemical fuels. However, up to now, mostly hydrogen peroxide has been employed as a fuel which renders the potential applications in biomedicine and in vivo experiments. Therefore, other sources of energy to achieve motion at the micro- nanoscale are highly sought-after. Here, we present different types of tubular micro- and nanorobots, alternative approaches to toxic fuels and also, steps towards the use of tubular microrobots as micro- and nanotools

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DOI [BibTex]

DOI [BibTex]


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Photoactive rolled-up TiO2 microtubes: fabrition, characterization and applications

Giuducatti, S., Marz, S. M., Soler, L., Madani, A., Jorgensen, M. R., Sanchez, S., Schmidt, O. G.

Journal of Materials Chemistry C: Materials for Optical and Electronic Devices, pages: 5892-5901, Royal Society of Chemistry, London, UK, 2014 (article)

Abstract
Because of its unique properties, titania (TiO2) represents a promising candidate in a wide variety of research fields. In this paper, some of the properties and potential applications of titania within rolled-up nanotechnology are explored. It is shown how the structural and optical properties of rolled titania microtubes can be controlled by properly tuning the microfabrication parameters. The rolling up of titania films on different sacrificial layers and containing different shapes, achieving a control on the diameter of the fabricated titania microtubes, is presented. In order to obtain the more photoactive crystalline form of titania, one during-fabrication and two post-fabrication methods are demonstrated. Interesting applications in the fields of photocatalysis and photonics are suggested: the use of titania rolled-up microtubes as micromotors and optical microresonators is presented.

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DOI [BibTex]

DOI [BibTex]


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How ions in solution can change the sign of the critical Casimir potential

Pousaneh, F., Ciach, A., Maciolek, A.

Soft Matter, 10(3):470-483, Royal Society of Chemistry, Cambridge, UK, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Critical Casimir interactions around the consolute point of a binary solvent

Mohry, T. F., Kondrat, S., Maciolek, A., Dietrich, S.

Soft Matter, 10(30):5510-5522, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Collapse and reversibility of the superhydrophobic state on nanotextured surfaces

Checco, A., Ocko, B. M., Rahman, A., Black, C. T., Tasinkevych, M., Giacomello, A., Dietrich, S.

Physical Review Letters, 112(21), American Physical Society., Woodbury, N.Y., etc., 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Density functional theory of electrowetting

Bier, M., Ibagon, I.

Physical Review E, 89(4), American Physical Society, Melville, NY, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Incremental Local Gaussian Regression

Meier, F., Hennig, P., Schaal, S.

In Advances in Neural Information Processing Systems 27, pages: 972-980, (Editors: Z. Ghahramani, M. Welling, C. Cortes, N.D. Lawrence and K.Q. Weinberger), 28th Annual Conference on Neural Information Processing Systems (NIPS), 2014, clmc (inproceedings)

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PDF link (url) [BibTex]

PDF link (url) [BibTex]


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Alignment of cylindrical colloids near chemically patterned substrates induced by critical Casimir torques

Labbe-Laurent, M., Tröndle, M., Harnau, L., Dietrich, S.

Soft Matter, 10(13):2270-2291, Royal Society of Chemistry, Cambridge, UK, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Heat transfer between anisotropic nanoparticles: Enhancement and switching

Incardone, R., Emig, T., Krüger, M.

Europhysics Letters, 106(4), 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Rolled-up Functionalized Nanomembranes as Three-Dimensional Cavities for Single Cell Studies

Xi, W., Schmidt, C., Sanchez, S., Gracias, D., Carazo-Salas, R., Jackson, S., Schmidt, O. G.

Nano Letters, 14(8):4197-4204, American Chemical Society, Washington, DC, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Cosmology in a petri dish? Simulation of collective dynamics of colloids at fluid interfaces

Bleibel, J.

In EPJ Web of Conferences, 70, EDP Sciences, 2014 (inproceedings)

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DOI [BibTex]


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Dispersions of ellipsoidal particles in a nematic liquid crystal

Tasinkevych, M., Mondiot, F., Mondain-Monval, O., Loudet, J. C.

Soft Matter, 10(12):2047-2058, Royal Society of Chemistry, Cambridge, UK, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Critical Casimir interactions between spherical particles in the presence of bulk ordering fields

Vasilyev, O.

Physical Review E, 90, American Physical Society, Melville, NY, 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Towards Template-Assisted Assembly of Nematic Colloids

Silvestre, N. M., Liu, Q., Senyuk, B., Smalyukh, I. I., Tasinkevych, M.

Physical Review Letters, 112(22), American Physical Society, Woodbury, N.Y., 2014 (article)

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DOI [BibTex]

DOI [BibTex]


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Efficient Bayesian Local Model Learning for Control

Meier, F., Hennig, P., Schaal, S.

In Proceedings of the IEEE International Conference on Intelligent Robots and Systems, pages: 2244 - 2249, IROS, 2014, clmc (inproceedings)

Abstract
Model-based control is essential for compliant controland force control in many modern complex robots, like humanoidor disaster robots. Due to many unknown and hard tomodel nonlinearities, analytical models of such robots are oftenonly very rough approximations. However, modern optimizationcontrollers frequently depend on reasonably accurate models,and degrade greatly in robustness and performance if modelerrors are too large. For a long time, machine learning hasbeen expected to provide automatic empirical model synthesis,yet so far, research has only generated feasibility studies butno learning algorithms that run reliably on complex robots.In this paper, we combine two promising worlds of regressiontechniques to generate a more powerful regression learningsystem. On the one hand, locally weighted regression techniquesare computationally efficient, but hard to tune due to avariety of data dependent meta-parameters. On the other hand,Bayesian regression has rather automatic and robust methods toset learning parameters, but becomes quickly computationallyinfeasible for big and high-dimensional data sets. By reducingthe complexity of Bayesian regression in the spirit of local modellearning through variational approximations, we arrive at anovel algorithm that is computationally efficient and easy toinitialize for robust learning. Evaluations on several datasetsdemonstrate very good learning performance and the potentialfor a general regression learning tool for robotics.

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PDF link (url) DOI [BibTex]

PDF link (url) DOI [BibTex]


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Perspective: Intelligent Systems: Bits and Bots

Spatz, J. P., Schaal, S.

Nature, (509), 2014, clmc (article)

Abstract
What is intelligence, and can we create it? Animals can perceive, reason, react and learn, but they are just one example of an intelligent system. Intelligent systems could be robots as large as humans, helping with search-and- rescue operations in dangerous places, or smart devices as tiny as a cell, delivering drugs to a target within the body. Even computing systems can be intelligent, by perceiving the world, crawling the web and processing â??big dataâ?? to extract and learn from complex information.Understanding not only how intelligence can be reproduced, but also how to build systems that put these ideas into practice, will be a challenge. Small intelligent systems will require new materials and fabrication methods, as well as com- pact information processors and power sources. And for nano-sized systems, the rules change altogether. The laws of physics operate very differently at tiny scales: for a nanorobot, swimming through water is like struggling through treacle.Researchers at the Max Planck Institute for Intelligent Systems have begun to solve these problems by developing new computational methods, experiment- ing with unique robotic systems and fabricating tiny, artificial propellers, like bacterial flagella, to propel nanocreations through their environment.

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PDF link (url) [BibTex]

PDF link (url) [BibTex]


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Stability Analysis of Distributed Event-Based State Estimation

Trimpe, S.

In Proceedings of the 53rd IEEE Conference on Decision and Control, Los Angeles, CA, 2014 (inproceedings)

Abstract
An approach for distributed and event-based state estimation that was proposed in previous work [1] is analyzed and extended to practical networked systems in this paper. Multiple sensor-actuator-agents observe a dynamic process, sporadically exchange their measurements over a broadcast network according to an event-based protocol, and estimate the process state from the received data. The event-based approach was shown in [1] to mimic a centralized Luenberger observer up to guaranteed bounds, under the assumption of identical estimates on all agents. This assumption, however, is unrealistic (it is violated by a single packet drop or slight numerical inaccuracy) and removed herein. By means of a simulation example, it is shown that non-identical estimates can actually destabilize the overall system. To achieve stability, the event-based communication scheme is supplemented by periodic (but infrequent) exchange of the agentsâ?? estimates and reset to their joint average. When the local estimates are used for feedback control, the stability guarantee for the estimation problem extends to the event-based control system.

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PDF Supplementary material DOI Project Page [BibTex]

PDF Supplementary material DOI Project Page [BibTex]