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Hydrodynamic interaction between overlapping domains during recurrence of registration within planar lipid bilayer membranes

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Physical Review E 2014年第3期89卷 032717-032717页

作者： Tao Han Trevor P. Bailey Mikko Haataja Department of Mechanical and Aerospace Engineering Princeton Institute for the Science and Technology of Materials (PRISM) and Program in Applied and Computational Mathematics (PACM) Princeton University Princeton New Jersey 08544 USA

Due to a thermodynamic coupling between the two leaflets comprising a lipid bilayer, compositional lipid domains residing within opposing leaflets are often found in registry. If the system is perturbed by displacing one domain relative to the other, diffusive and advective lipid fluxes are established to restore equilibrium and reestablish domain overlap. In this work, we focus on the advective part of the process, and first derive an analytical expression for the hydrodynamic drag coefficient associated with the advective flow for the special case of perfect domain overlap. The resulting expression identifies parameter regions where sliding friction between the leaflets dominates over viscous dissipation within the leaflets or vice versa. It is shown that in all practically relevant cases, sliding friction between the leaflets is the dominant factor. Finally, we investigate the domain separation dependence of the hydrodynamic drag coefficient via direct simulations of a continuum diffuse interface model, and provide useful empirical expressions for its behavior.

关键词： HYDRODYNAMICS BILAYER lipid membranes DRAG coefficient ENERGY dissipation SLIDING friction FLUX (Energy)

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Erratum to: Some Joys and Trials of Mathematical Neuroscience

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Journal of Nonlinear Science 2014年第2期24卷 243-244页

作者： Holmes, Philip Department of Mechanical and Aerospace Engineering Program in Applied and Computational Mathematics Princeton University Princeton USA Princeton Neuroscience Institute Princeton University Princeton USA

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Hybrid LS-SA-PS methods for solving fuzzy non-linear programming problems

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MATHEMATICAL AND COMPUTER MODELLING 2013年第1-2期57卷 180-188页

作者： Vasant, Pandian Engineering Mathematics Program Fundamental & Applied Sciences Department University Technology Petronas Malaysia

The fuzzy optimization problem is one of the prominent topics in the broad area of artificial intelligence. It is applicable in the field of non-linear fuzzy programming. Its application as well as practical realization can been seen in all the real world problems. In this paper a large scale non-linear fuzzy programming problem was solved by hybrid optimization techniques like Line Search (LS), Simulated Annealing (SA) and Pattern Search (PS). An industrial production planning problem with a cubic objective function, eight decision variables and 29 constraints was solved successfully using the LS-SA-PS hybrid optimization techniques. The computational results for the objective function with respect to vagueness factor and level of satisfaction has been provided in the form of 2D and 3D plots. The outcome is very promising and strongly suggests that the hybrid LS-SA-PS algorithm is very efficient and productive in solving the large scale non-linear fuzzy programming problem. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Nonlinear fuzzy programming Simulated annealing Pattern search Line search Vagueness factor Level of satisfaction

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Optimization of feedforward neural network by Multiple Particle Collision Algorithm

Optimization of feedforward neural network by Multiple Parti...

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IEEE Symposium on Foundations of Computational Intelligence, FOCI

作者： Juliana A Anochi Haroldo F. de Campos Velho Applied Computing Graduate Program National Institute for Space Research SP Brazil Laboratory Computing and Applied Mathematics National Institute for Space Research SP Brazil

Optimization of neural network topology, weights and neuron activation functions for given data set and problem is not an easy task. In this article, a technique for automatic configuration of parameters topology for feedforward artificial neural networks (ANN) is presented. The determination of optimal parameters is formulated as an optimization problem, solved with the use of meta-heuristic Multiple Particle Collision Algorithm (MPCA). The self-configuring networks are applied to predict the mesoscale climate for the precipitation field. The results obtained from the neural network using the method of data reduction by the Theory of Rough Sets and the self-configuring network by MPCA were compared.

关键词： Artificial neural networks Topology Meteorology Network topology Training Atmospheric modeling Biological neural networks

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Randomized Iterative Hard Thresholding for Sparse Approximations

Randomized Iterative Hard Thresholding for Sparse Approximat...

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Data Compression Conference (DCC)

作者： Robert Crandall Bin Dong Ali Bilgin program in Applied Mathematics University of Arizona Tucson AZ USA Dept. of Mathematics University of Arizona Tucson AZ USA Dept of Electrical and Computer Eng University of Arizona Tucson AZ USA

ISBN: (纸本)9781479934188

Summary form only given. Typical greedy algorithms for sparse reconstruction problems, such as orthogonal matching pursuit and iterative thresholding, seek strictly sparse solutions. Recent work in the literature suggests that given a priori knowledge of the distribution of the sparse signal coefficients, better results can be obtained by a weighted averaging of several sparse solutions. Such a combination of solutions, while not strictly sparse, approximates an MMSE estimator and can outperform strictly sparse solvers in terms of l-2 reconstruction error. We introduce a novel method for obtaining such an approximate MMSE estimator by replacing the deterministic thresholding operator of Iterative Hard Thresholding with a randomized version. We demonstrate the improvement in performance experimentally for both synthetic 1D signals and real images.

关键词： Sparse Approximations sparse reconstruction problem recover a vector x from (possibly noisy) measurements Iterative RANDOMISING Noise Threshold formula

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Angular momentum dependent orbital-free density functional theory: Formulation and implementation

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Physical Review B 2014年第15期89卷 155112-155112页

作者： Youqi Ke Florian Libisch Junchao Xia Emily A. Carter []Department of Mechanical and Aerospace Engineering Program in Applied and Computational Mathematics and Andlinger Center for Energy and the Environment Princeton University Princeton New Jersey 08544-5263 USA

Orbital-free density functional theory (OFDFT) directly solves for the ground-state electron density. It scales linearly with respect to system size, providing a promising tool for large-scale material simulations. Removal of the orbitals requires use of approximate noninteracting kinetic energy density functionals. If replacing ionic cores with pseudopotentials, removal of the orbitals also requires these pseudopotentials to be local. These are two severe challenges to the capabilities of conventional OFDFT. While main group elements are often well described within conventional OFDFT, transition metals remain intractable due to their localized d electrons. To advance the accuracy and general applicability of OFDFT, we have recently reported a general angular momentum dependent formulation as a next-generation OFDFT. In this formalism, we incorporate the angular momenta of electrons by devising a hybrid scheme based on a muffin tin geometry: inside spheres centered at the ionic cores, the electron density is expanded in a set of atom-centered basis functions combined with an onsite density matrix. The explicit treatment of the angular momenta of electrons provides an important basis for accurately describing the important ionic core region, which is not possible in conventional OFDFT. In addition to the conventional OFDFT total energy functional, we introduce a nonlocal energy term containing a set of angular momentum dependent energies to correct the errors due to the approximate kinetic energy density functional and local pseudopotentials. Our approach greatly increases the accuracy of OFDFT while largely preserving its numerical simplicity. Here, we provide details of the theoretical formulation and practical implementation, including the hybrid scheme, the derivation of the nonlocal energy term, the choice of basis functions, the direct minimization of the total energy, the procedure to determine the angular momentum dependent energies, the force formula with Pu

关键词： ANGULAR momentum (Nuclear physics) DENSITY functional theory GROUND state (Quantum mechanics) ELECTRON density SIMULATION methods & models DENSITY functionals

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Study on eliminating spurious eddies at the interfaces of two-phase flows using lattice boltzmann simulations

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Journal of Computational Multiphase Flows 2014年第2期6卷 127-131页

作者： Wei, Y. Yang, J.F. Wang, Z.D. Yan, W.W. Qian, Y.H. Faculty of Mechanical Engineering and Automation Province Key Laboratory of Fluid Transmission Technology Zhejiang Sci-Tech University Hangzhou 310018 China Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China Shanghai Program for Innovative Research Team in Universities Shanghai 200072 China College of Metrology and Measurement Engineering China Jiliang University Hangzhou 310018 China

Stationary bubbles simulated by the multiphase lattice Boltzmann method (LBM) lead to eight symmetric eddies at the interfaces of two-phase flows. A distribution function is introduced in the lattice Boltzmann equation. Numerical simulations conform that eight symmetric eddies at the interfaces of two-phase flows are eliminated effectively by using this method, and the spurious velocities are reduces effectively.

关键词： Two phase flow

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Downlink analysis for a heterogeneous cellular network

Downlink analysis for a heterogeneous cellular network

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2014 12th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, WiOpt 2014

作者： Madhusudhanan, Prasanna Restrepo, Juan G. Liu, Youjian Eugene Brown, Timothy X. Department of Electrical Computer and Energy Engineering University of Colorado Boulder CO 80309-0425 United States Department of Applied Mathematics University of Colorado Boulder CO 80309-0425 United States Interdisciplinary Telecommunications Program University of Colorado Boulder CO 80309-0425 United States

ISBN: (纸本)9783901882630

In this paper, a comprehensive study of the downlink performance in a heterogeneous cellular network (or hetnet) is conducted. A general hetnet model is considered consisting of an arbitrary number of open-access and closed-access tier of base stations (BSs) arranged according to independent homogeneous Poisson point processes. The BSs of each tier have a constant transmission power, random fading coefficient with an arbitrary distribution and arbitrary path-loss exponent of the power-law path-loss model. For such a system, analytical characterizations for the coverage probability and average rate at an arbitrary mobile-station (MS), and average per-tier load are derived for the max-SINR connectivity model. Using stochastic ordering, interesting properties and simplifications for the hetnet downlink performance are derived by relating this connectivity model to the maximum instantaneous received power (MIRP) connectivity model, providing good insights about the hetnets and the downlink performance in these complex networks. Furthermore, the results also demonstrate the effectiveness and analytical tractability of the stochastic geometric approach to study the hetnet performance. © 2014 IFIP.

关键词： Fading channels

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Optimization-Based String Method for Finding Minimum Energy Path

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Communications in Computational Physics 2013年第7期14卷 265-275页

作者： Amit Samanta Weinan E Program in Applied and Computational Mathematics Princeton UniversityPrincetonNew JerseyUSA Department of Mathematics and Program in Applied and Computational Mathematics Princeton UniversityPrincetonNew JerseyUSA Beijing International Center for Mathematical Research Peking UniversityBeijingChina

We present an efficient algorithm for calculating the minimum energy path(MEP)and energy barriers between local minima on a multidimensional potential energy surface(PES).Such paths play a central role in the understanding of transition pathways between metastable *** method relies on the original formulation of the string method[***.B,66,052301(2002)],*** evolve a smooth curve along a direction normal to the *** algorithm works by performing minimization steps on hyperplanes normal to the *** the problem of finding MEP on the PES is remodeled as a set of constrained minimization *** provides the flexibility of using minimization algorithms faster than the steepest descent method used in the simplified string method[***.,126(16),164103(2007)].At the same time,it provides a more direct analog of the finite temperature string *** applicability of the algorithm is demonstrated using various examples.

关键词： Rare events string method minimum energy path dislocation nucleation

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Density-based and transport-based core-periphery structures in networks

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Physical Review E 2014年第3期89卷 032810-032810页

作者： Sang Hoon Lee Mihai Cucuringu Mason A. Porter Oxford Centre for Industrial and Applied Mathematics Mathematical Institute University of Oxford Oxford OX2 6GG United Kingdom Program in Applied and Computational Mathematics (PACM) Princeton University Fine Hall Washington Road Princeton New Jersey 08544-1000 USA Department of Mathematics University of California Los Angeles Los Angeles California 90095 USA CABDyN Complexity Centre University of Oxford Oxford OX1 1HP United Kingdom

Networks often possess mesoscale structures, and studying them can yield insights into both structure and function. It is most common to study community structure, but numerous other types of mesoscale structures also exist. In this paper, we examine core-periphery structures based on both density and transport. In such structures, core network components are well-connected both among themselves and to peripheral components, which are not well-connected to anything. We examine core-periphery structures in a wide range of examples of transportation, social, and financial networks—including road networks in large urban areas, a rabbit warren, a dolphin social network, a European interbank network, and a migration network between counties in the United States. We illustrate that a recently developed transport-based notion of node coreness is very useful for characterizing transportation networks. We also generalize this notion to examine core versus peripheral edges, and we show that the resulting diagnostic is also useful for transportation networks. To examine the properties of transportation networks further, we develop a family of generative models of roadlike networks. We illustrate the effect of the dimensionality of the embedding space on transportation networks, and we demonstrate that the correlations between different measures of coreness can be very different for different types of networks.

关键词： MESOSCALE convective complexes -- Computer simulation COMMUNITY organization TRANSPORTATION SOCIAL networks DENSITY MARKOV processes DEPENDENCY (Imperialism)

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