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Emergence of Coherence in Complex Networks of Heterogeneous Dynamical Systems

Physical Review Letters 2006年第25期96卷 254103-254103页

作者： Juan G. Restrepo Edward Ott Brian R. Hunt Institute for Research in Electronics and Applied Physics University of Maryland College Park Maryland 20742 USA Department of Mathematics University of Maryland College Park Maryland 20742 USA Department of Physics and Department of Electrical and Computer Engineering University of Maryland College Park Maryland 20742 USA Institute for Physical Science and Technology University of Maryland College Park Maryland 20742 USA

We present a general theory for the onset of coherence in collections of heterogeneous maps interacting via a complex connection network. Our method allows the dynamics of the individual uncoupled systems to be either chaotic or periodic, and applies generally to networks for which the number of connections per node is large. We find that the critical coupling strength at which a transition to synchrony takes place depends separately on the dynamics of the individual uncoupled systems and on the largest eigenvalue of the adjacency matrix of the coupling network. Our theory directly generalizes the Kuramoto model of equal strength all-to-all coupled phase oscillators to the case of oscillators with more realistic dynamics coupled via a large heterogeneous network.

关键词： .week ending dynamical systems oscillators coherence per node critical coupling All-to-All Kuramoto Model Maryland USA transition to synchrony

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Scale Dependence of Branching in Arterial and Bronchial Trees

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Physical Review Letters 2006年第12期96卷 128101-128101页

Although models of branching in arterial and bronchial trees often predict a dependence of bifurcation parameters on the scale of the bifurcating vessels, direct verification of this dependence by comparison with data is uncommon. We compare measurements of bifurcation parameters of airways and arterial trees of different mammals as a function of scale to general features predicted by theoretical models based on minimization of pumping power and network volume. We find that the size dependence is more complex than existing theories based solely on energy and volume minimization explain, and suggest additional factors that may govern the branching at different scales.

关键词： .pumping Vessels PRL week Theoretical models bifurcation parameters BRONCHIAL Maryland USA arterial trees

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Characterizing the Dynamical Importance of Network Nodes and Links

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Physical Review Letters 2006年第9期97卷 094102-094102页

The largest eigenvalue of the adjacency matrix of networks is a key quantity determining several important dynamical processes on complex networks. Based on this fact, we present a quantitative, objective characterization of the dynamical importance of network nodes and links in terms of their effect on the largest eigenvalue. We show how our characterization of the dynamical importance of nodes can be affected by degree-degree correlations and network community structure. We discuss how our characterization can be used to optimize techniques for controlling certain network dynamical processes and apply our results to real networks.

关键词： .week ending largest eigenvalue network nodes dynamical processes Maryland USA Dynamical Importance importance of nodes

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Quadruped robot obstacle negotiation via reinforcement learning

Quadruped robot obstacle negotiation via reinforcement learn...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： Honglak Lee Yirong Shen Chih-Han Yu G. Singh A.Y. Ng Stanford University Stanford CA US Department of Electrical Engineering University of Stanford Stanford CA USA Scientific Computing and Computational Mathematics Program University of Stanford Stanford CA USA Computer Science Department University of Stanford Stanford CA USA

Legged robots can, in principle, traverse a large variety of obstacles and terrains. In this paper, we describe a successful application of reinforcement learning to the problem of negotiating obstacles with a quadruped robot. Our algorithm is based on a two-level hierarchical decomposition of the task, in which the high-level controller selects the sequence of foot-placement positions, and the low-level controller generates the continuous motions to move each foot to the specified positions. The high-level controller uses an estimate of the value function to guide its search; this estimate is learned partially from supervised data. The low-level controller is obtained via policy search. We demonstrate that our robot can successfully climb over a variety of obstacles which were not seen at training time

关键词： Learning Robot kinematics Legged locomotion Foot Mobile robots Leg Motion control Robotics and automation Path planning Computer science

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Plant-wide (BSM2) evaluation of reject water treatment with a SHARON-anommox process

Plant-wide (BSM2) evaluation of reject water treatment with ...

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作者： Volcke, Eveline I.P. Gernaey, K.V. Vrecko, Darko Jeppsson, Ulf Van Loosdrecht, M.C.M. Vanrolleghem, Peter A. BIOMATH Department of Applied Mathematics Biometrics and Process Control Ghent University Coupure Links 653 B-9000 Gent Belgium Department of Industrial Electrical Engineering and Automation Lund University PO Box 118 SE-22100 Lund Sweden Department of Chemical Engineering Technical University of Denmark Building 229 DK-2800 Kgs. Lyngby Denmark Department of Systems and Control Jožef Stefan Institute Jamova 39 SI-1000 Ljubljana Slovenia Department of Biochemical Engineering Delft University of Technology Julianalaan 67 NL-2628 BC Delft Netherlands ModelEAU Département de Génie Civil Université Laval Pavillon Pouliot Québec QC G1K 7P4 Canada

ISBN: (纸本)1843395835

In wastewater treatment plants (WWTPs) equipped with sludge digestion and dewatering systems, the reject water originating from these facilities contributes significantly to the nitrogen load of the activated sludge tanks, to which it is typically recycled. In this paper, the impact of reject water streams on the performance of a WWTP is assessed in a simulation study, using the Benchmark Simulation Model no. 2 (BSM2), that includes the processes describing sludge treatment and in this way allows for plant-wide evaluation. Comparison of performance of a WWTP without reject water with a WWTP where reject water is recycled to the primary clarifier, i.e. the BSM2 plant, shows that the ammonium load of the influent to the primary clarifier is 28% higher in the case of reject water recycling. This results in violation of the effluent total nitrogen limit. In order to relieve the main wastewater treatment plant, reject water treatment with a combined SHARON-Anammox process seems a promising option. The simulation results indicate that significant improvements of the effluent quality of the main wastewater treatment plant can be realized. An economic evaluation of the different scenarios is performed using an Operating Cost Index (OCI). © IWA Publishing 2006.

关键词： Wastewater treatment

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Vocal Folds Vibrations with a Three-Dimensional Deformable Model

Vocal Folds Vibrations with a Three-Dimensional Deformable M...

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IEEE International Symposium on Multimedia

作者： Arlindo Neto Montagnoli Jose Benaque Rubert Rodrigo Capobianco Guido Jose Carlos Pereira Department of Statistic Applied Mathematics and Computing São Paulo State University Sao Paulo Brazil Department of Production Engineering Federal University of So Carlos Department of Computation University of Norte Paulista-UNORP Sao Paulo Brazil Department of Electrical Engineering University of São Paulo at São Carlos-USP Sao Paulo Brazil

ISBN: (纸本)0769527469;9780769527468

In this work a computational method is presented to simulate the movements of vocal folds in three dimensions. The proposed model consists of a mesh free structure where each vertex is connected its neighbor through a group spring-damper. Forced oscillations were studied by time varying surface forces. The preliminary results using this model are similar with the literature and with the experimental stroboscopic observations of larynx

关键词： Deformable models Springs Larynx Vibrations Computational modeling Shock absorbers Damping Nonlinear equations Ligaments Surface waves

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Enhancement of light extraction in GaInN light-emitting diodes by conductive omni-directional reflectors

Enhancement of light extraction in GaInN light-emitting diod...

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Conference on Lasers and Electro-Optics (CLEO)

作者： Jong Kyu Kim J.-Q. Xi Hong Luo E. Fred Schubert Jaehee Cho Cheolsoo Sone Yongjo Park Electrical Computer and Systems Engineering Department Rensselaer Polytechnic Institute Troy NY USA Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy NY USA Photonics Program Team Samsung Advanced Institute of Technology Suwon South Korea

Enhancement of light extraction in a GaInN light-emitting diode employing a conductive omnidirectional reflector consisting of GaN, an indium-tin oxide nanorod low-refractive-index layer, and an Ag layer is presented.

ISBN: (纸本)1557528136

关键词： Indium tin oxide Light emitting diodes Refractive index Gallium nitride Films Reflectivity Optical reflection

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Mechanism of enhanced broadening of the ionization level of Li outside transition metal surfaces

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Physical Review B 2006年第11期74卷 115109-115109页

作者： Keith Niedfeldt Peter Nordlander Emily A. Carter Department of Mechanical and Aerospace Engineering and Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544-5263 USA Department of Physics and Astronomy M.S. 61 Rice University P.O. Box 1892 6100 South Main Street Houston Texas 77251-1892 USA

We show that the d-band of a transition metal surface induces intra-atomic hybridization of an atom in its vicinity. It is demonstrated that such hybridization can have a profound influence on the resonance width and hence lifetime of the atomic ionization level. The degree of Li s−p hybridization is found to be directly correlated to the overlap of the d-band density of states with the Li 2s and 2p levels, and is shown to be not due solely to long-range electrostatic image potential effects.

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Nano-scale imaging with a compact EUV laser

Nano-scale imaging with a compact EUV laser

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Conference on Lasers and Electro-Optics, CLEO 2006

作者： Vaschenko, G. Brizuela, F. Brewer, C. Grisham, M. Mancini, H. Menoni, C.S. Marconi, M. Rocca, J.J. Chao, W. Liddle, A. Anderson, E. Attwood, D. Vinogradov, A.V. Artioukov, I.A. Pershyn, Yu.P. Kondratenko, V.V. NSF ERC for Extreme Ultraviolet Science and Technology Department of Electrical and Computer Engineering Colorado State University Fort Collins CO 80523 United States Center for X-ray Optics Lawrence Berkeley National Laboratory Berkeley CA 94720 United States NSF ERC for Extreme Ultraviolet Science and Technology United States P. N. Lebedev Physical Institute Moscow 117942 Russia Metal and Semiconductor Physics Department National Technical University KhPI Kharkov Ukraine Department of Physics and Applied Mathematics University of Navarre Pamplona Spain

We report sub-140 nm resolution imaging with 46.9 nm radiation from a compact capillary-discharge laser. This result was obtained using a combination of a Sc/Si multilayercoated Schwarzschild condenser and free-standi... 详细信息

ISBN: (纸本)1557528136

关键词： Nanotechnology

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Collective coordinate control of density distributions

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Physical Review E 2006年第3期74卷 031104-031104页

作者： Obioma U. Uche Salvatore Torquato Frank H. Stillinger Department of Chemical Engineering Princeton University Princeton New Jersey 08544 USA Department of Chemistry Princeton University Princeton New Jersey 08544 USA Princeton Institute for the Science and Technology of Materials Princeton University Princeton New Jersey 08544 USA Program in Applied & Computational Mathematics Princeton University Princeton New Jersey 08544 USA Princeton Center for Theoretical Physics Princeton University Princeton New Jersey 08544 USA

Real collective density variables C(k) [cf. Eq. (1.3)] in many-particle systems arise from nonlinear transformations of particle positions, and determine the structure factor S(k), where k denotes the wave vector. Our objective is to prescribe C(k) and then to find many-particle configurations that correspond to such a target C(k) using a numerical optimization technique. Numerical results reported here extend earlier one- and two-dimensional studies to include three dimensions. In addition, they demonstrate the capacity to control S(k) in the neighborhood of ∣k∣=0. The optimization method employed generates multiparticle configurations for which S(k)∝∣k∣α, ∣k∣⩽K, and α=1, 2, 4, 6, 8, and 10. The case α=1 is relevant for the Harrison-Zeldovich model of the early universe, for superfluid He4, and for jammed amorphous sphere packings. The analysis also provides specific examples of interaction potentials whose classical ground states are configurationally degenerate and disordered.

关键词： STATISTICAL MECHANICS REALIZABILITY SYSTEM

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