Stability estimates for hybrid coupled domain decomposition methods
Steinbach, Olaf
2003-01-01
Domain decomposition methods are a well established tool for an efficient numerical solution of partial differential equations, in particular for the coupling of different model equations and of different discretization methods. Based on the approximate solution of local boundary value problems either by finite or boundary element methods, the global problem is reduced to an operator equation on the skeleton of the domain decomposition. Different variational formulations then lead to hybrid domain decomposition methods.
Fast structural design and analysis via hybrid domain decomposition on massively parallel processors
Farhat, Charbel
1993-01-01
A hybrid domain decomposition framework for static, transient and eigen finite element analyses of structural mechanics problems is presented. Its basic ingredients include physical substructuring and /or automatic mesh partitioning, mapping algorithms, 'gluing' approximations for fast design modifications and evaluations, and fast direct and preconditioned iterative solvers for local and interface subproblems. The overall methodology is illustrated with the structural design of a solar viewing payload that is scheduled to fly in March 1993. This payload has been entirely designed and validated by a group of undergraduate students at the University of Colorado using the proposed hybrid domain decomposition approach on a massively parallel processor. Performance results are reported on the CRAY Y-MP/8 and the iPSC-860/64 Touchstone systems, which represent both extreme parallel architectures. The hybrid domain decomposition methodology is shown to outperform leading solution algorithms and to exhibit an excellent parallel scalability.
Energy Technology Data Exchange (ETDEWEB)
Gaiffe, St.
2000-03-23
In this thesis, we are interested in the modeling of fluid flow through porous media with 2-D and 3-D unstructured meshes, and in the use of domain decomposition methods. The behavior of flow through porous media is strongly influenced by heterogeneities: either large-scale lithological discontinuities or quite localized phenomena such as fluid flow in the neighbourhood of wells. In these two typical cases, an accurate consideration of the singularities requires the use of adapted meshes. After having shown the limits of classic meshes we present the future prospects offered by hybrid and flexible meshes. Next, we consider the generalization possibilities of the numerical schemes traditionally used in reservoir simulation and we draw two available approaches: mixed finite elements and U-finite volumes. The investigated phenomena being also characterized by different time-scales, special treatments in terms of time discretization on various parts of the domain are required. We think that the combination of domain decomposition methods with operator splitting techniques may provide a promising approach to obtain high flexibility for a local tune-steps management. Consequently, we develop a new numerical scheme for linear parabolic equations which allows to get a higher flexibility in the local space and time steps management. To conclude, a priori estimates and error estimates on the two variables of interest, namely the pressure and the velocity are proposed. (author)
Directory of Open Access Journals (Sweden)
Ran Zhao
2015-01-01
Full Text Available The hybrid solvers based on integral equation domain decomposition method (HS-DDM are developed for modeling of electromagnetic radiation. Based on the philosophy of “divide and conquer,” the IE-DDM divides the original multiscale problem into many closed nonoverlapping subdomains. For adjacent subdomains, the Robin transmission conditions ensure the continuity of currents, so the meshes of different subdomains can be allowed to be nonconformal. It also allows different fast solvers to be used in different subdomains based on the property of different subdomains to reduce the time and memory consumption. Here, the multilevel fast multipole algorithm (MLFMA and hierarchical (H- matrices method are combined in the framework of IE-DDM to enhance the capability of IE-DDM and realize efficient solution of multiscale electromagnetic radiating problems. The MLFMA is used to capture propagating wave physics in large, smooth regions, while H-matrices are used to capture evanescent wave physics in small regions which are discretized with dense meshes. Numerical results demonstrate the validity of the HS-DDM.
Ying, Jinyong
2016-01-01
The size-modified Poisson-Boltzmann equation (SMPBE) is one important variant of the popular dielectric model, the Poisson-Boltzmann equation (PBE), to reflect ionic size effects in the prediction of electrostatics for a biomolecule in an ionic solvent. In this paper, a new SMPBE hybrid solver is developed using a solution decomposition, the Schwartz's overlapped domain decomposition, finite element, and finite difference. It is then programmed as a software package in C, Fortran, and Python based on the state-of-the-art finite element library DOLFIN from the FEniCS project. This software package is well validated on a Born ball model with analytical solution and a dipole model with a known physical properties. Numerical results on six proteins with different net charges demonstrate its high performance. Finally, this new SMPBE hybrid solver is shown to be numerically stable and convergent in the calculation of electrostatic solvation free energy for 216 biomolecules and binding free energy for a DNA-drug com...
A Hybrid, Parallel Krylov Solver for MODFLOW using Schwarz Domain Decomposition
Sutanudjaja, E.; Verkaik, J.; Hughes, J. D.
2015-12-01
In order to support decision makers in solving hydrological problems, detailed high-resolution models are often needed. These models typically consist of a large number of computational cells and have large memory requirements and long run times. An efficient technique for obtaining realistic run times and memory requirements is parallel computing, where the problem is divided over multiple processor cores. The new Parallel Krylov Solver (PKS) for MODFLOW-USG is presented. It combines both distributed memory parallelization by the Message Passing Interface (MPI) and shared memory parallelization by Open Multi-Processing (OpenMP). PKS includes conjugate gradient and biconjugate gradient stabilized linear accelerators that are both preconditioned by an overlapping additive Schwarz preconditioner in a way that: a) subdomains are partitioned using the METIS library; b) each subdomain uses local memory only and communicates with other subdomains by MPI within the linear accelerator; c) is fully integrated in the MODFLOW-USG code. PKS is based on the unstructured PCGU-solver, and supports OpenMP. Depending on the available hardware, PKS can run exclusively with MPI, exclusively with OpenMP, or with a hybrid MPI/OpenMP approach. Benchmarks were performed on the Cartesius Dutch supercomputer (https://userinfo.surfsara.nl/systems/cartesius) using up to 144 cores, for a synthetic test (~112 million cells) and the Indonesia groundwater model (~4 million 1km cells). The latter, which includes all islands in the Indonesian archipelago, was built using publically available global datasets, and is an ideal test bed for evaluating the applicability of PKS parallelization techniques to a global groundwater model consisting of multiple continents and islands. Results show that run time reductions can be greatest with the hybrid parallelization approach for the problems tested.
Domain decomposition algorithms and computational fluid dynamics
Chan, Tony F.
1988-01-01
Some of the new domain decomposition algorithms are applied to two model problems in computational fluid dynamics: the two-dimensional convection-diffusion problem and the incompressible driven cavity flow problem. First, a brief introduction to the various approaches of domain decomposition is given, and a survey of domain decomposition preconditioners for the operator on the interface separating the subdomains is then presented. For the convection-diffusion problem, the effect of the convection term and its discretization on the performance of some of the preconditioners is discussed. For the driven cavity problem, the effectiveness of a class of boundary probe preconditioners is examined.
Decomposition and Removability Properties of John Domains
Indian Academy of Sciences (India)
M Huang; S Ponnusamy; X Wang
2008-08-01
In this paper we characterize John domains in terms of John domain decomposition property. In addition, we also show that a domain in $\\mathbb{R}^n$ is a John domain if and only if $D\\backslash P$ is a John domain, where is a subset of containing finitely many points of . The best possibility and an application of the second result are also discussed.
Domain Decomposition Based High Performance Parallel Computing
Raju, Mandhapati P
2009-01-01
The study deals with the parallelization of finite element based Navier-Stokes codes using domain decomposition and state-ofart sparse direct solvers. There has been significant improvement in the performance of sparse direct solvers. Parallel sparse direct solvers are not found to exhibit good scalability. Hence, the parallelization of sparse direct solvers is done using domain decomposition techniques. A highly efficient sparse direct solver PARDISO is used in this study. The scalability of both Newton and modified Newton algorithms are tested.
Convergence Analysis of a Domain Decomposition Paradigm
Energy Technology Data Exchange (ETDEWEB)
Bank, R E; Vassilevski, P S
2006-06-12
We describe a domain decomposition algorithm for use in several variants of the parallel adaptive meshing paradigm of Bank and Holst. This algorithm has low communication, makes extensive use of existing sequential solvers, and exploits in several important ways data generated as part of the adaptive meshing paradigm. We show that for an idealized version of the algorithm, the rate of convergence is independent of both the global problem size N and the number of subdomains p used in the domain decomposition partition. Numerical examples illustrate the effectiveness of the procedure.
Multiple Shooting and Time Domain Decomposition Methods
Geiger, Michael; Körkel, Stefan; Rannacher, Rolf
2015-01-01
This book offers a comprehensive collection of the most advanced numerical techniques for the efficient and effective solution of simulation and optimization problems governed by systems of time-dependent differential equations. The contributions present various approaches to time domain decomposition, focusing on multiple shooting and parareal algorithms. The range of topics covers theoretical analysis of the methods, as well as their algorithmic formulation and guidelines for practical implementation. Selected examples show that the discussed approaches are mandatory for the solution of challenging practical problems. The practicability and efficiency of the presented methods is illustrated by several case studies from fluid dynamics, data compression, image processing and computational biology, giving rise to possible new research topics. This volume, resulting from the workshop Multiple Shooting and Time Domain Decomposition Methods, held in Heidelberg in May 2013, will be of great interest to applied...
Domain decomposition for implicit solvation models.
Cancès, Eric; Maday, Yvon; Stamm, Benjamin
2013-08-07
This article is the first of a series of papers dealing with domain decomposition algorithms for implicit solvent models. We show that, in the framework of the COSMO model, with van der Waals molecular cavities and classical charge distributions, the electrostatic energy contribution to the solvation energy, usually computed by solving an integral equation on the whole surface of the molecular cavity, can be computed more efficiently by using an integral equation formulation of Schwarz's domain decomposition method for boundary value problems. In addition, the so-obtained potential energy surface is smooth, which is a critical property to perform geometry optimization and molecular dynamics simulations. The purpose of this first article is to detail the methodology, set up the theoretical foundations of the approach, and study the accuracies and convergence rates of the resulting algorithms. The full efficiency of the method and its applicability to large molecular systems of biological interest is demonstrated elsewhere.
Domain Decomposition Methods for Hyperbolic Problems
Indian Academy of Sciences (India)
Pravir Dutt; Subir Singh Lamba
2009-04-01
In this paper a method is developed for solving hyperbolic initial boundary value problems in one space dimension using domain decomposition, which can be extended to problems in several space dimensions. We minimize a functional which is the sum of squares of the 2 norms of the residuals and a term which is the sum of the squares of the 2 norms of the jumps in the function across interdomain boundaries. To make the problem well posed the interdomain boundaries are made to move back and forth at alternate time steps with sufficiently high speed. We construct parallel preconditioners and obtain error estimates for the method. The Schwarz waveform relaxation method is often employed to solve hyperbolic problems using domain decomposition but this technique faces difficulties if the system becomes characteristic at the inter-element boundaries. By making the inter-element boundaries move faster than the fastest wave speed associated with the hyperbolic system we are able to overcome this problem.
Domain decomposition methods for mortar finite elements
Energy Technology Data Exchange (ETDEWEB)
Widlund, O.
1996-12-31
In the last few years, domain decomposition methods, previously developed and tested for standard finite element methods and elliptic problems, have been extended and modified to work for mortar and other nonconforming finite element methods. A survey will be given of work carried out jointly with Yves Achdou, Mario Casarin, Maksymilian Dryja and Yvon Maday. Results on the p- and h-p-version finite elements will also be discussed.
Bregmanized Domain Decomposition for Image Restoration
Langer, Andreas
2012-05-22
Computational problems of large-scale data are gaining attention recently due to better hardware and hence, higher dimensionality of images and data sets acquired in applications. In the last couple of years non-smooth minimization problems such as total variation minimization became increasingly important for the solution of these tasks. While being favorable due to the improved enhancement of images compared to smooth imaging approaches, non-smooth minimization problems typically scale badly with the dimension of the data. Hence, for large imaging problems solved by total variation minimization domain decomposition algorithms have been proposed, aiming to split one large problem into N > 1 smaller problems which can be solved on parallel CPUs. The N subproblems constitute constrained minimization problems, where the constraint enforces the support of the minimizer to be the respective subdomain. In this paper we discuss a fast computational algorithm to solve domain decomposition for total variation minimization. In particular, we accelerate the computation of the subproblems by nested Bregman iterations. We propose a Bregmanized Operator Splitting-Split Bregman (BOS-SB) algorithm, which enforces the restriction onto the respective subdomain by a Bregman iteration that is subsequently solved by a Split Bregman strategy. The computational performance of this new approach is discussed for its application to image inpainting and image deblurring. It turns out that the proposed new solution technique is up to three times faster than the iterative algorithm currently used in domain decomposition methods for total variation minimization. © Springer Science+Business Media, LLC 2012.
Load Estimation by Frequency Domain Decomposition
DEFF Research Database (Denmark)
Pedersen, Ivar Chr. Bjerg; Hansen, Søren Mosegaard; Brincker, Rune;
2007-01-01
When performing operational modal analysis the dynamic loading is unknown, however, once the modal properties of the structure have been estimated, the transfer matrix can be obtained, and the loading can be estimated by inverse filtering. In this paper loads in frequency domain are estimated...... by analysis of simulated responses of a 4 DOF system, for which the exact modal parameters are known. This estimation approach entails modal identification of the natural eigenfrequencies, mode shapes and damping ratios by the frequency domain decomposition technique. Scaled mode shapes are determined by use...
Energy Technology Data Exchange (ETDEWEB)
Feng, Xiaobing [Univ. of Tennessee, Knoxville, TN (United States)
1996-12-31
A non-overlapping domain decomposition iterative method is proposed and analyzed for mixed finite element methods for a sequence of noncoercive elliptic systems with radiation boundary conditions. These differential systems describe the motion of a nearly elastic solid in the frequency domain. The convergence of the iterative procedure is demonstrated and the rate of convergence is derived for the case when the domain is decomposed into subdomains in which each subdomain consists of an individual element associated with the mixed finite elements. The hybridization of mixed finite element methods plays a important role in the construction of the discrete procedure.
PARTITION PROPERTY OF DOMAIN DECOMPOSITION WITHOUT ELLIPTICITY
Institute of Scientific and Technical Information of China (English)
Mo Mu; Yun-qing Huang
2001-01-01
Partition property plays a central role in domain decomposition methods. Existing theory essentially assumes certain ellipticity. We prove the partition property for problems without ellipticity which are of practical importance. Example applications include implicit schemes applied to degenerate parabolic partial differential equations arising from superconductors, superfluids and liquid crystals. With this partition property, Schwarz algorithms can be applied to general non-elliptic problems with an h-independent optimal convergence rate. Application to the time-dependent Ginzburg-Landau model of superconductivity is illustrated and numerical results are presented.
Domain decomposition algorithms and computation fluid dynamics
Chan, Tony F.
1988-01-01
In the past several years, domain decomposition was a very popular topic, partly motivated by the potential of parallelization. While a large body of theory and algorithms were developed for model elliptic problems, they are only recently starting to be tested on realistic applications. The application of some of these methods to two model problems in computational fluid dynamics are investigated. Some examples are two dimensional convection-diffusion problems and the incompressible driven cavity flow problem. The construction and analysis of efficient preconditioners for the interface operator to be used in the iterative solution of the interface solution is described. For the convection-diffusion problems, the effect of the convection term and its discretization on the performance of some of the preconditioners is discussed. For the driven cavity problem, the effectiveness of a class of boundary probe preconditioners is discussed.
Space-time domain decomposition method for scalar conservation laws
Doucoure, S
2012-01-01
The Space-Time Integrated Least-Squares (STILS) method is considered to analyze a space-time domain decomposition algorithm for scalar conservation laws. Continuous and discrete convergence estimates are given. Next using a time-marching finite element formulation, the STILS solution and its domain decomposition form are numerically compared.
A NONOVERLAPPING DOMAIN DECOMPOSITION METHOD FOR EXTERIOR 3-D PROBLEM
Institute of Scientific and Technical Information of China (English)
De-hao Yu; Ji-ming Wu; Ji-ming Wu
2001-01-01
In this paper, a nonoverlapping domain decomposition method, which is based on the natural boundary reduction(cf. [4, 13, 15]), is developed to solve the boundary value problem in exterior three-dimensional domain of general shape. Convergence analyses both for the exterior spherical domain and the general exterior domain are made. Some numerical examples are also provided to illustrate the method.
Non-overlapping domain decomposition methods in structural mechanics
Gosselet, Pierre; 10.1007/BF02905857
2012-01-01
The modern design of industrial structures leads to very complex simulations characterized by nonlinearities, high heterogeneities, tortuous geometries... Whatever the modelization may be, such an analysis leads to the solution to a family of large ill-conditioned linear systems. In this paper we study strategies to efficiently solve to linear system based on non-overlapping domain decomposition methods. We present a review of most employed approaches and their strong connections. We outline their mechanical interpretations as well as the practical issues when willing to implement and use them. Numerical properties are illustrated by various assessments from academic to industrial problems. An hybrid approach, mainly designed for multifield problems, is also introduced as it provides a general framework of such approaches.
21st International Conference on Domain Decomposition Methods
Gander, Martin; Halpern, Laurence; Pichot, Géraldine; Sassi, Taoufik; Widlund, Olof
2014-01-01
This volume contains a selection of papers presented at the 21st international conference on domain decomposition methods in science and engineering held in Rennes, France, June 25-29, 2012. Domain decomposition is an active and interdisciplinary research discipline, focusing on the development, analysis and implementation of numerical methods for massively parallel computers. Domain decomposition methods are among the most efficient solvers for large scale applications in science and engineering. They are based on a solid theoretical foundation and shown to be scalable for many important applications. Domain decomposition techniques can also naturally take into account multiscale phenomena. This book contains the most recent results in this important field of research, both mathematically and algorithmically and allows the reader to get an overview of this exciting branch of numerical analysis and scientific computing.
A PARALLEL NONOVERLAPPING DOMAIN DECOMPOSITION METHOD FOR STOKES PROBLEMS
Institute of Scientific and Technical Information of China (English)
Mei-qun Jiang; Pei-liang Dai
2006-01-01
A nonoverlapping domain decomposition iterative procedure is developed and analyzed for generalized Stokes problems and their finite element approximate problems in RN(N=2,3). The method is based on a mixed-type consistency condition with two parameters as a transmission condition together with a derivative-free transmission data updating technique on the artificial interfaces. The method can be applied to a general multi-subdomain decomposition and implemented on parallel machines with local simple communications naturally.
22nd International Conference on Domain Decomposition Methods
Gander, Martin; Halpern, Laurence; Krause, Rolf; Pavarino, Luca
2016-01-01
These are the proceedings of the 22nd International Conference on Domain Decomposition Methods, which was held in Lugano, Switzerland. With 172 participants from over 24 countries, this conference continued a long-standing tradition of internationally oriented meetings on Domain Decomposition Methods. The book features a well-balanced mix of established and new topics, such as the manifold theory of Schwarz Methods, Isogeometric Analysis, Discontinuous Galerkin Methods, exploitation of modern HPC architectures, and industrial applications. As the conference program reflects, the growing capabilities in terms of theory and available hardware allow increasingly complex non-linear and multi-physics simulations, confirming the tremendous potential and flexibility of the domain decomposition concept.
Splitting extrapolation based on domain decomposition for finite element approximations
Institute of Scientific and Technical Information of China (English)
吕涛; 冯勇
1997-01-01
Splitting extrapolation based on domain decomposition for finite element approximations is a new technique for solving large scale scientific and engineering problems in parallel. By means of domain decomposition, a large scale multidimensional problem is turned to many discrete problems involving several grid parameters The multi-variate asymptotic expansions of finite element errors on independent grid parameters are proved for linear and nonlin ear second order elliptic equations as well as eigenvalue problems. Therefore after solving smaller problems with similar sizes in parallel, a global fine grid approximation with higher accuracy is computed by the splitting extrapolation method.
Noise Tracking Using DFT Domain Subspace Decompositions
Hendriks, R.C.; Jensen, J.; Heusdens, R.
2008-01-01
All discrete Fourier transform (DFT) domain-based speech enhancement gain functions rely on knowledge of the noise power spectral density (PSD). Since the noise PSD is unknown in advance, estimation from the noisy speech signal is necessary. An overestimation of the noise PSD will lead to a loss in
Noise Tracking Using DFT Domain Subspace Decompositions
Hendriks, R.C.; Jensen, J.; Heusdens, R.
2008-01-01
All discrete Fourier transform (DFT) domain-based speech enhancement gain functions rely on knowledge of the noise power spectral density (PSD). Since the noise PSD is unknown in advance, estimation from the noisy speech signal is necessary. An overestimation of the noise PSD will lead to a loss in
Using domain decomposition in the Jacobi-Davidson method
Genseberger, M.; Sleijpen, G.L.G.; Vorst, H.A. van der
2000-01-01
The Jacobi-Davidson method is suitable for computing solutions of large $n$-dimensional eigenvalue problems. It needs (approximate) solutions of specific $n$-dimensional linear systems. Here we propose a strategy based on a nonoverlapping domain decomposition technique in order to reduce the wall cl
Using domain decomposition in the Jacobi-Davidson method
Genseberger, M.; Sleijpen, G.L.G.; Vorst, H.A. van der
2001-01-01
The JacobiDavidson method is suitable for computing solutions of large ndimensional eigen value problems. It needs (approximate) solutions of specific ndimensional linear systems. Here we propose a strategy based on a nonoverlapping domain decomposition technique in order to reduce the wall c
DOMAIN DECOMPOSITION METHODS WITH NONMATCHING GRIDS FOR THE UNILATERAL PROBLEM
Institute of Scientific and Technical Information of China (English)
Ping Luo; Guo-ping Liang
2002-01-01
This paper is devoted to the construction of domain decomposition methods with nonmatching grids based on mixed finite element methods for the unilateral problem. The existence and uniqueness of solution are discussed and optimal error bounds are obtained.Furthermore, global superconvergence estimates are given.
QPACE 2 and Domain Decomposition on the Intel Xeon Phi
Arts, Paul; Georg, Peter; Glaessle, Benjamin; Heybrock, Simon; Komatsubara, Yu; Lohmayer, Robert; Mages, Simon; Mendl, Bernhard; Meyer, Nils; Parcianello, Alessio; Pleiter, Dirk; Rappl, Florian; Rossi, Mauro; Solbrig, Stefan; Tecchiolli, Giampietro; Wettig, Tilo; Zanier, Gianpaolo
2015-01-01
We give an overview of QPACE 2, which is a custom-designed supercomputer based on Intel Xeon Phi processors, developed in a collaboration of Regensburg University and Eurotech. We give some general recommendations for how to write high-performance code for the Xeon Phi and then discuss our implementation of a domain-decomposition-based solver and present a number of benchmarks.
Using domain decomposition in the Jacobi-Davidson method
Genseberger, M.; Sleijpen, G.L.G.; Vorst, H.A. van der
2000-01-01
The JacobiDavidson method is suitable for computing solutions of large ndimensional eigen value problems. It needs (approximate) solutions of specific ndimensional linear systems. Here we propose a strategy based on a nonoverlapping domain decomposition technique in order to reduce the
Automated Frequency Domain Decomposition for Operational Modal Analysis
DEFF Research Database (Denmark)
Brincker, Rune; Andersen, Palle; Jacobsen, Niels-Jørgen
2007-01-01
The Frequency Domain Decomposition (FDD) technique is known as one of the most user friendly and powerful techniques for operational modal analysis of structures. However, the classical implementation of the technique requires some user interaction. The present paper describes an algorithm for au...
Implementation and performance of a domain decomposition algorithm in Sisal
Energy Technology Data Exchange (ETDEWEB)
DeBoni, T.; Feo, J. [Lawrence Livermore National Lab., CA (United States); Rodrigue, G. [California Univ., Livermore, CA (United States); Muller, J. [State Univ. of New York, Stony Brook, NY (United States)
1993-09-23
Sisal is a general-purpose functional language that hides the complexity of parallel processing, expedites parallel program development, and guarantees determinacy. Parallelism and management of concurrent tasks are realized automatically by the compiler and runtime system. Spatial domain decomposition is a widely-used method that focuses computational resources on the most active, or important, areas of a domain. Many complex programming issues are introduced in paralleling this method including: dynamic spatial refinement, dynamic grid partitioning and fusion, task distribution, data distribution, and load balancing. In this paper, we describe a spatial domain decomposition algorithm programmed in Sisal. We explain the compilation process, and present the execution performance of the resultant code on two different multiprocessor systems: a multiprocessor vector supercomputer, and cache-coherent scalar multiprocessor.
Domain Decomposition Solvers for Frequency-Domain Finite Element Equations
Copeland, Dylan
2010-10-05
The paper is devoted to fast iterative solvers for frequency-domain finite element equations approximating linear and nonlinear parabolic initial boundary value problems with time-harmonic excitations. Switching from the time domain to the frequency domain allows us to replace the expensive time-integration procedure by the solution of a simple linear elliptic system for the amplitudes belonging to the sine- and to the cosine-excitation or a large nonlinear elliptic system for the Fourier coefficients in the linear and nonlinear case, respectively. The fast solution of the corresponding linear and nonlinear system of finite element equations is crucial for the competitiveness of this method. © 2011 Springer-Verlag Berlin Heidelberg.
A TFETI Domain Decomposition Solver for Elastoplastic Problems
Čermák, M; Sysala, S; Valdman, J
2012-01-01
In the paper, we propose an algorithm for the efficient parallel implementation of elastoplastic problems with hardening based on the so-called TFETI (Total Finite Element Tearing and Interconnecting) domain decomposition method. We consider an associated elastoplastic model with the von Mises plastic criterion and the linear isotropic hardening law. Such a model is discretized by the implicit Euler method in time and the consequent one time step elastoplastic problem by the finite element method in space. The latter results in a system of nonlinear equations with a strongly semismooth and strongly monotone operator. The semismooth Newton method is applied to solve this nonlinear system. Corresponding linearized problems arising in the Newton iterations are solved in parallel by the above mentioned TFETI domain decomposition method. The proposed TFETI based algorithm was implemented in Matlab parallel environment and its performance was illustrated on a 3D elastoplastic benchmark. Numerical results for differ...
Domain decomposition methods for solving an image problem
Energy Technology Data Exchange (ETDEWEB)
Tsui, W.K.; Tong, C.S. [Hong Kong Baptist College (Hong Kong)
1994-12-31
The domain decomposition method is a technique to break up a problem so that ensuing sub-problems can be solved on a parallel computer. In order to improve the convergence rate of the capacitance systems, pre-conditioned conjugate gradient methods are commonly used. In the last decade, most of the efficient preconditioners are based on elliptic partial differential equations which are particularly useful for solving elliptic partial differential equations. In this paper, the authors apply the so called covering preconditioner, which is based on the information of the operator under investigation. Therefore, it is good for various kinds of applications, specifically, they shall apply the preconditioned domain decomposition method for solving an image restoration problem. The image restoration problem is to extract an original image which has been degraded by a known convolution process and additive Gaussian noise.
Separation Surfaces in the Spectral TV Domain for Texture Decomposition
Horesh, Dikla; Gilboa, Guy
2016-09-01
In this paper we introduce a novel notion of separation surfaces for image decomposition. A surface is embedded in the spectral total-variation (TV) three dimensional domain and encodes a spatially-varying separation scale. The method allows good separation of textures with gradually varying pattern-size, pattern-contrast or illumination. The recently proposed total variation spectral framework is used to decompose the image into a continuum of textural scales. A desired texture, within a scale range, is found by fitting a surface to the local maximal responses in the spectral domain. A band above and below the surface, referred to as the \\textit{Texture Stratum}, defines for each pixel the adaptive scale-range of the texture. Based on the decomposition an application is proposed which can attenuate or enhance textures in the image in a very natural and visually convincing manner.
Overlapping Domain Decomposition Methods with FreeFem++
Jolivet, Pierre; Hecht, Frédéric; Nataf, Frédéric; Prud'Homme, Christophe
2012-01-01
International audience; In this note, the performances of a framework for two-level overlapping domain decomposition methods are assessed. Numerical experiments are run on Curie, a Tier-0 system for PRACE, for two second order elliptic PDE with highly heterogeneous coefficients: a scalar equation of diffusivity and the system of linear elasticity. Those experiments yield systems with up to ten billion unknowns in 2D and one billion unknowns in 3D, solved on few thousands cores.
An Improved Traffic Matrix Decomposition Method with Frequency Domain Regularization
Wang, Zhe; Yin, Baolin
2012-01-01
In this letter, we propose a novel network traffic matrix decomposition method named as Stable Principal Component Pursuit with Frequency Domain Regularization (SPCP-FDR). SPCP-FDR improves the Stable Principal Component Pursuit (SPCP) method by using a new noise regularization function defined in frequency domain. Compared with SPCP, SPCP-FDR is more adaptive to empirical frequency properties of diverse traffic components. The Accelerated Proximal Gradient (APG) algorithm for SPCP-FDR is presented. Our experiment results demonstrate the rationality of this new method.
Higher order statistical frequency domain decomposition for operational modal analysis
Nita, G. M.; Mahgoub, M. A.; Sharyatpanahi, S. G.; Cretu, N. C.; El-Fouly, T. M.
2017-02-01
Experimental methods based on modal analysis under ambient vibrational excitation are often employed to detect structural damages of mechanical systems. Many of such frequency domain methods, such as Basic Frequency Domain (BFD), Frequency Domain Decomposition (FFD), or Enhanced Frequency Domain Decomposition (EFFD), use as first step a Fast Fourier Transform (FFT) estimate of the power spectral density (PSD) associated with the response of the system. In this study it is shown that higher order statistical estimators such as Spectral Kurtosis (SK) and Sample to Model Ratio (SMR) may be successfully employed not only to more reliably discriminate the response of the system against the ambient noise fluctuations, but also to better identify and separate contributions from closely spaced individual modes. It is shown that a SMR-based Maximum Likelihood curve fitting algorithm may improve the accuracy of the spectral shape and location of the individual modes and, when combined with the SK analysis, it provides efficient means to categorize such individual spectral components according to their temporal dynamics as coherent or incoherent system responses to unknown ambient excitations.
Segmented Domain Decomposition Multigrid For 3-D Turbomachinery Flows
Celestina, M. L.; Adamczyk, J. J.; Rubin, S. G.
2001-01-01
A Segmented Domain Decomposition Multigrid (SDDMG) procedure was developed for three-dimensional viscous flow problems as they apply to turbomachinery flows. The procedure divides the computational domain into a coarse mesh comprised of uniformly spaced cells. To resolve smaller length scales such as the viscous layer near a surface, segments of the coarse mesh are subdivided into a finer mesh. This is repeated until adequate resolution of the smallest relevant length scale is obtained. Multigrid is used to communicate information between the different grid levels. To test the procedure, simulation results will be presented for a compressor and turbine cascade. These simulations are intended to show the ability of the present method to generate grid independent solutions. Comparisons with data will also be presented. These comparisons will further demonstrate the usefulness of the present work for they allow an estimate of the accuracy of the flow modeling equations independent of error attributed to numerical discretization.
Decomposition method for solving parabolic equations in finite domains
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
This paper presents a comparison among Adomian decomposition method (ADM), Wavelet-Galerkin method (WGM),the fully explicit (1,7) finite difference technique (FTCS), the fully implicit (7,1) finite difference method (BTCS), (7,7)Crank-Nicholson type finite difference formula (C-N), the fully explicit method (1,13) and 9-point finite difference method, for solving parabolic differential equations with arbitrary boundary conditions and based on weak form functionals in finite domains.The problem is solved rapidly, easily and elegantly by ADM. The numerical results on a 2D transient heat conducting problem and 3D diffusion problem are used to validate the proposed ADM as an effective numerical method for solving finite domain parabolic equations. The numerical results showed that our present method is less time consuming and is easier to use than other methods. In addition, we prove the convergence of this method when it is applied to the nonlinear parabolic equation.
Simplified approaches to some nonoverlapping domain decomposition methods
Energy Technology Data Exchange (ETDEWEB)
Xu, Jinchao
1996-12-31
An attempt will be made in this talk to present various domain decomposition methods in a way that is intuitively clear and technically coherent and concise. The basic framework used for analysis is the {open_quotes}parallel subspace correction{close_quotes} or {open_quotes}additive Schwarz{close_quotes} method, and other simple technical tools include {open_quotes}local-global{close_quotes} and {open_quotes}global-local{close_quotes} techniques, the formal one is for constructing subspace preconditioner based on a preconditioner on the whole space whereas the later one for constructing preconditioner on the whole space based on a subspace preconditioner. The domain decomposition methods discussed in this talk fall into two major categories: one, based on local Dirichlet problems, is related to the {open_quotes}substructuring method{close_quotes} and the other, based on local Neumann problems, is related to the {open_quotes}Neumann-Neumann method{close_quotes} and {open_quotes}balancing method{close_quotes}. All these methods will be presented in a systematic and coherent manner and the analysis for both two and three dimensional cases are carried out simultaneously. In particular, some intimate relationship between these algorithms are observed and some new variants of the algorithms are obtained.
Institute of Scientific and Technical Information of China (English)
Ji-ming Wu; De-hao Yu
2000-01-01
In this paper, the overlapping domain decomposition method, which is based on the natural boundary reduction[1] and first suggested in [2], is applied to slove the exterior boundary value problem of harmonic equation over three-dimensional domain. The convergence and error estimates both for the continuous case and the discrete case are given. The contraction factor for the exterior spherical domain is also discussed. Moreover, numerical results are given which show that the accuracy and the convergence are in accord with the theoretical analyses.
23rd International Conference on Domain Decomposition Methods in Science and Engineering
Cai, Xiao-Chuan; Keyes, David; Kim, Hyea; Klawonn, Axel; Park, Eun-Jae; Widlund, Olof
2017-01-01
This book is a collection of papers presented at the 23rd International Conference on Domain Decomposition Methods in Science and Engineering, held on Jeju Island, Korea on July 6-10, 2015. Domain decomposition methods solve boundary value problems by splitting them into smaller boundary value problems on subdomains and iterating to coordinate the solution between adjacent subdomains. Domain decomposition methods have considerable potential for a parallelization of the finite element methods, and serve a basis for distributed, parallel computations.
Energy Technology Data Exchange (ETDEWEB)
Gazzaniga, G.; Sacchi, G. [Istituto di Analisi Numerica, Pavia (Italy)
1995-12-01
Different Domain Decomposition techniques for the solution of elliptic boundary-value problems are considered. The results of the implementation on a parallel distributed memory architecture are discussed.
Institute of Scientific and Technical Information of China (English)
Igor Boglaev; Matthew Hardy
2008-01-01
This paper presents and analyzes a monotone domain decomposition algorithm for solving nonlinear singularly perturbed reaction-diffusion problems of parabolic type.To solve the nonlinear weighted average finite difference scheme for the partial differential equation,we construct a monotone domain decomposition algorithm based on a Schwarz alternating method and a box-domain decomposition.This algorithm needs only to solve linear discrete systems at each iterative step and converges monotonically to the exact solution of the nonlinear discrete problem. The rate of convergence of the monotone domain decomposition algorithm is estimated.Numerical experiments are presented.
THE DOMAIN DECOMPOSITION TECHNIQUES FOR THE FINITE ELEMENT PROBABILITY COMPUTATIONAL METHODS
Institute of Scientific and Technical Information of China (English)
LIU Xiaoqi
2000-01-01
In this paper, we shall study the domain decomposition techniques for the finite element probability computational methods. These techniques provide a theoretical basis for parallel probability computational methods.
Non-linear scalable TFETI domain decomposition based contact algorithm
Dobiáš, J.; Pták, S.; Dostál, Z.; Vondrák, V.; Kozubek, T.
2010-06-01
The paper is concerned with the application of our original variant of the Finite Element Tearing and Interconnecting (FETI) domain decomposition method, called the Total FETI (TFETI), to solve solid mechanics problems exhibiting geometric, material, and contact non-linearities. The TFETI enforces the prescribed displacements by the Lagrange multipliers, so that all the subdomains are 'floating', the kernels of their stiffness matrices are known a priori, and the projector to the natural coarse grid is more effective. The basic theory and relationships of both FETI and TFETI are briefly reviewed and a new version of solution algorithm is presented. It is shown that application of TFETI methodology to the contact problems converts the original problem to the strictly convex quadratic programming problem with bound and equality constraints, so that the effective, in a sense optimal algorithms is to be applied. Numerical experiments show that the method exhibits both numerical and parallel scalabilities.
A convergent overlapping domain decomposition method for total variation minimization
Fornasier, Massimo
2010-06-22
In this paper we are concerned with the analysis of convergent sequential and parallel overlapping domain decomposition methods for the minimization of functionals formed by a discrepancy term with respect to the data and a total variation constraint. To our knowledge, this is the first successful attempt of addressing such a strategy for the nonlinear, nonadditive, and nonsmooth problem of total variation minimization. We provide several numerical experiments, showing the successful application of the algorithm for the restoration of 1D signals and 2D images in interpolation/inpainting problems, respectively, and in a compressed sensing problem, for recovering piecewise constant medical-type images from partial Fourier ensembles. © 2010 Springer-Verlag.
Analysis of generalized Schwarz alternating procedure for domain decomposition
Energy Technology Data Exchange (ETDEWEB)
Engquist, B.; Zhao, Hongkai [Univ. of California, Los Angeles, CA (United States)
1996-12-31
The Schwartz alternating method(SAM) is the theoretical basis for domain decomposition which itself is a powerful tool both for parallel computation and for computing in complicated domains. The convergence rate of the classical SAM is very sensitive to the overlapping size between each subdomain, which is not desirable for most applications. We propose a generalized SAM procedure which is an extension of the modified SAM proposed by P.-L. Lions. Instead of using only Dirichlet data at the artificial boundary between subdomains, we take a convex combination of u and {partial_derivative}u/{partial_derivative}n, i.e. {partial_derivative}u/{partial_derivative}n + {Lambda}u, where {Lambda} is some {open_quotes}positive{close_quotes} operator. Convergence of the modified SAM without overlapping in a quite general setting has been proven by P.-L.Lions using delicate energy estimates. The important questions remain for the generalized SAM. (1) What is the most essential mechanism for convergence without overlapping? (2) Given the partial differential equation, what is the best choice for the positive operator {Lambda}? (3) In the overlapping case, is the generalized SAM superior to the classical SAM? (4) What is the convergence rate and what does it depend on? (5) Numerically can we obtain an easy to implement operator {Lambda} such that the convergence is independent of the mesh size. To analyze the convergence of the generalized SAM we focus, for simplicity, on the Poisson equation for two typical geometry in two subdomain case.
Hybrid proper orthogonal decomposition formulation for linear structural dynamics
Placzek, A.; Tran, D.-M.; Ohayon, R.
2008-12-01
Hybrid proper orthogonal decomposition (PODh) formulation is a POD-based reduced-order modeling method where the continuous equation of the physical system is projected on the POD modes obtained from a discrete model of the system. The aim of this paper is to evaluate the hybrid POD formulation and to compare it with other POD formulations on the simple case of a linear elastic rod subject to prescribed displacements in the perspective of building reduced-order models for coupled fluid-structure systems in the future. In the first part of the paper, the hybrid POD is compared to two other formulations for the response to an initial condition: an approach based on the discrete finite elements equation of the rod called the discrete POD (PODd), and an analytical approach using the exact solution of the problem and consequently called the analytical POD (PODa). This first step is useful to ensure that the PODh performs well with respect to the other formulations. The PODh is therefore used afterwards for the forced motion response where a displacement is imposed at the free end of the rod. The main contribution of this paper lies in the comparison of three techniques used to take into account the non-homogeneous Dirichlet boundary condition with the hybrid POD: the first method relies on control functions, the second on the penalty method and the third on Lagrange multipliers. Finally, the robustness of the hybrid POD is investigated on two examples involving firstly the introduction of structural damping and secondly a nonlinear force applied at the free end of the rod.
Hybrid empirical mode decomposition- ARIMA for forecasting exchange rates
Abadan, Siti Sarah; Shabri, Ani; Ismail, Shuhaida
2015-02-01
This paper studied the forecasting of monthly Malaysian Ringgit (MYR)/ United State Dollar (USD) exchange rates using the hybrid of two methods which are the empirical model decomposition (EMD) and the autoregressive integrated moving average (ARIMA). MYR is pegged to USD during the Asian financial crisis causing the exchange rates are fixed to 3.800 from 2nd of September 1998 until 21st of July 2005. Thus, the chosen data in this paper is the post-July 2005 data, starting from August 2005 to July 2010. The comparative study using root mean square error (RMSE) and mean absolute error (MAE) showed that the EMD-ARIMA outperformed the single-ARIMA and the random walk benchmark model.
Energy Technology Data Exchange (ETDEWEB)
Maliassov, S.Y. [Texas A& M Univ., College Station, TX (United States)
1996-12-31
An approach to the construction of an iterative method for solving systems of linear algebraic equations arising from nonconforming finite element discretizations with nonmatching grids for second order elliptic boundary value problems with anisotropic coefficients is considered. The technique suggested is based on decomposition of the original domain into nonoverlapping subdomains. The elliptic problem is presented in the macro-hybrid form with Lagrange multipliers at the interfaces between subdomains. A block diagonal preconditioner is proposed which is spectrally equivalent to the original saddle point matrix and has the optimal order of arithmetical complexity. The preconditioner includes blocks for preconditioning subdomain and interface problems. It is shown that constants of spectral equivalence axe independent of values of coefficients and mesh step size.
A physics-motivated Centroidal Voronoi Particle domain decomposition method
Fu, Lin; Hu, Xiangyu Y.; Adams, Nikolaus A.
2017-04-01
In this paper, we propose a novel domain decomposition method for large-scale simulations in continuum mechanics by merging the concepts of Centroidal Voronoi Tessellation (CVT) and Voronoi Particle dynamics (VP). The CVT is introduced to achieve a high-level compactness of the partitioning subdomains by the Lloyd algorithm which monotonically decreases the CVT energy. The number of computational elements between neighboring partitioning subdomains, which scales the communication effort for parallel simulations, is optimized implicitly as the generated partitioning subdomains are convex and simply connected with small aspect-ratios. Moreover, Voronoi Particle dynamics employing physical analogy with a tailored equation of state is developed, which relaxes the particle system towards the target partition with good load balance. Since the equilibrium is computed by an iterative approach, the partitioning subdomains exhibit locality and the incremental property. Numerical experiments reveal that the proposed Centroidal Voronoi Particle (CVP) based algorithm produces high-quality partitioning with high efficiency, independently of computational-element types. Thus it can be used for a wide range of applications in computational science and engineering.
Parallel Finite Element Domain Decomposition for Structural/Acoustic Analysis
Nguyen, Duc T.; Tungkahotara, Siroj; Watson, Willie R.; Rajan, Subramaniam D.
2005-01-01
A domain decomposition (DD) formulation for solving sparse linear systems of equations resulting from finite element analysis is presented. The formulation incorporates mixed direct and iterative equation solving strategics and other novel algorithmic ideas that are optimized to take advantage of sparsity and exploit modern computer architecture, such as memory and parallel computing. The most time consuming part of the formulation is identified and the critical roles of direct sparse and iterative solvers within the framework of the formulation are discussed. Experiments on several computer platforms using several complex test matrices are conducted using software based on the formulation. Small-scale structural examples are used to validate thc steps in the formulation and large-scale (l,000,000+ unknowns) duct acoustic examples are used to evaluate the ORIGIN 2000 processors, and a duster of 6 PCs (running under the Windows environment). Statistics show that the formulation is efficient in both sequential and parallel computing environmental and that the formulation is significantly faster and consumes less memory than that based on one of the best available commercialized parallel sparse solvers.
The domain interface method in non-conforming domain decomposition multifield problems
Lloberas-Valls, O.; Cafiero, M.; Cante, J.; Ferrer, A.; Oliver, J.
2017-04-01
The Domain Interface Method (DIM) is extended in this contribution for the case of mixed fields as encountered in multiphysics problems. The essence of the non-conforming domain decomposition technique consists in a discretization of a fictitious zero-thickness interface as in the original methodology and continuity of the solution fields across the domains is satisfied by incorporating the corresponding Lagrange Multipliers. The multifield DIM inherits the advantages of its irreducible version in the sense that the connections between non-matching meshes, with possible geometrically non-conforming interfaces, is accounted by the automatic Delaunay interface discretization without considering master and slave surfaces or intermediate surface projections as done in many established techniques, e.g. mortar methods. The multifield enhancement identifies the Lagrange multiplier field and incorporates its contribution in the weak variational form accounting for the corresponding consistent stabilization term based on a Nitsche method. This type of constraint enforcement circumvents the appearance of instabilities when the Ladyzhenskaya-Babu\\vska-Brezzi (LBB) condition is not fulfilled by the chosen discretization. The domain decomposition framework is assessed in a large deformation setting for mixed displacement/pressure formulations and coupled thermomechanical problems. The continuity of the mixed field is studied in well selected benchmark problems for both mixed formulations and the objectivity of the response is compared to reference monolithic solutions. Results suggest that the presented strategy shows sufficient potential to be a valuable tool in situations where the evolving physics at particular domains require the use of different spatial discretizations or field interpolations.
The domain interface method in non-conforming domain decomposition multifield problems
Lloberas-Valls, O.; Cafiero, M.; Cante, J.; Ferrer, A.; Oliver, J.
2016-12-01
The Domain Interface Method (DIM) is extended in this contribution for the case of mixed fields as encountered in multiphysics problems. The essence of the non-conforming domain decomposition technique consists in a discretization of a fictitious zero-thickness interface as in the original methodology and continuity of the solution fields across the domains is satisfied by incorporating the corresponding Lagrange Multipliers. The multifield DIM inherits the advantages of its irreducible version in the sense that the connections between non-matching meshes, with possible geometrically non-conforming interfaces, is accounted by the automatic Delaunay interface discretization without considering master and slave surfaces or intermediate surface projections as done in many established techniques, e.g. mortar methods. The multifield enhancement identifies the Lagrange multiplier field and incorporates its contribution in the weak variational form accounting for the corresponding consistent stabilization term based on a Nitsche method. This type of constraint enforcement circumvents the appearance of instabilities when the Ladyzhenskaya-Babu\\vska-Brezzi (LBB) condition is not fulfilled by the chosen discretization. The domain decomposition framework is assessed in a large deformation setting for mixed displacement/pressure formulations and coupled thermomechanical problems. The continuity of the mixed field is studied in well selected benchmark problems for both mixed formulations and the objectivity of the response is compared to reference monolithic solutions. Results suggest that the presented strategy shows sufficient potential to be a valuable tool in situations where the evolving physics at particular domains require the use of different spatial discretizations or field interpolations.
Domain decomposition parallel computing for transient two-phase flow of nuclear reactors
Energy Technology Data Exchange (ETDEWEB)
Lee, Jae Ryong; Yoon, Han Young [KAERI, Daejeon (Korea, Republic of); Choi, Hyoung Gwon [Seoul National University, Seoul (Korea, Republic of)
2016-05-15
KAERI (Korea Atomic Energy Research Institute) has been developing a multi-dimensional two-phase flow code named CUPID for multi-physics and multi-scale thermal hydraulics analysis of Light water reactors (LWRs). The CUPID code has been validated against a set of conceptual problems and experimental data. In this work, the CUPID code has been parallelized based on the domain decomposition method with Message passing interface (MPI) library. For domain decomposition, the CUPID code provides both manual and automatic methods with METIS library. For the effective memory management, the Compressed sparse row (CSR) format is adopted, which is one of the methods to represent the sparse asymmetric matrix. CSR format saves only non-zero value and its position (row and column). By performing the verification for the fundamental problem set, the parallelization of the CUPID has been successfully confirmed. Since the scalability of a parallel simulation is generally known to be better for fine mesh system, three different scales of mesh system are considered: 40000 meshes for coarse mesh system, 320000 meshes for mid-size mesh system, and 2560000 meshes for fine mesh system. In the given geometry, both single- and two-phase calculations were conducted. In addition, two types of preconditioners for a matrix solver were compared: Diagonal and incomplete LU preconditioner. In terms of enhancement of the parallel performance, the OpenMP and MPI hybrid parallel computing for a pressure solver was examined. It is revealed that the scalability of hybrid calculation was enhanced for the multi-core parallel computation.
Dupuis, A.; Koumoutsakos, P.
We present a convergence study for a hybrid Lattice Boltzmann-Molecular Dynamics model for the simulation of dense liquids. Time and length scales are decoupled by using an iterative Schwarz domain decomposition algorithm. The velocity field from the atomistic domain is introduced as forcing terms to the Lattice Boltzmann model of the continuum while the mean field of the continuum imposes mean field conditions for the atomistic domain. In the present paper we investigate the effect of varying the size of the atomistic subdomain in simulations of two dimensional flows of liquid argon past carbon nanotubes and assess the efficiency of the method.
Output-only Modal Analysis by Frequency Domain Decomposition
DEFF Research Database (Denmark)
Brincker, Rune; Zhang, L.; Andersen, P.
2000-01-01
approach where the modal parameters are estimated by simple peak picking. However, by introducing a decomposition of the spectral density function matrix, the response spectra can be separated into a set of single degree of freedom systems, each corresponding to an individual mode. By using...... this decomposition technique close modes can be identified with high accuracy even in the case of strong noise contamination of the signals. Also, the technique clearly indicates harmonic components in the response signals....
Output-Only Modal Analysis by Frequency Domain Decomposition
DEFF Research Database (Denmark)
Brincker, Rune; Zhang, Lingmi; Andersen, Palle
2000-01-01
approach where the modal parameters are estimated by simple peak picking. However, by introducing a decomposition of the spectral density function matrix, the response spectra can be separated into a set of single degree of freedom systems, each corresponding to an individual mode. By using...... this decomposition technique close modes can be identified with high accuracy even in the case of strong noise contamination of the signals. Also, the technique clearly indicates harmonic components in the response signals....
Institute of Scientific and Technical Information of China (English)
WANG Bing; SHU Jiwu; ZHENG Weimin; WANG Jinzhao; CHEN Min
2005-01-01
A hybrid decomposition method for molecular dynamics simulations was presented, using simultaneously spatial decomposition and force decomposition to fit the architecture of a cluster of symmetric multi-processor (SMP) nodes. The method distributes particles between nodes based on the spatial decomposition strategy to reduce inter-node communication costs. The method also partitions particle pairs within each node using the force decomposition strategy to improve the load balance for each node. Simulation results for a nucleation process with 4 000 000 particles show that the hybrid method achieves better parallel performance than either spatial or force decomposition alone, especially when applied to a large scale particle system with non-uniform spatial density.
Korneev, V. G.
2012-09-01
BPS is a well known an efficient and rather general domain decomposition Dirichlet-Dirichlet type preconditioner, suggested in the famous series of papers Bramble, Pasciak and Schatz (1986-1989). Since then, it has been serving as the origin for the whole family of domain decomposition Dirichlet-Dirichlet type preconditioners-solvers as for h so hp discretizations of elliptic problems. For its original version, designed for h discretizations, the named authors proved the bound O(1 + log2 H/ h) for the relative condition number under some restricting conditions on the domain decomposition and finite element discretization. Here H/ h is the maximal relation of the characteristic size H of a decomposition subdomain to the mesh parameter h of its discretization. It was assumed that subdomains are images of the reference unite cube by trilinear mappings. Later similar bounds related to h discretizations were proved for more general domain decompositions, defined by means of coarse tetrahedral meshes. These results, accompanied by the development of some special tools of analysis aimed at such type of decompositions, were summarized in the book of Toselli and Widlund (2005). This paper is also confined to h discretizations. We further expand the range of admissible domain decompositions for constructing BPS preconditioners, in which decomposition subdomains can be convex polyhedrons, satisfying some conditions of shape regularity. We prove the bound for the relative condition number with the same dependence on H/ h as in the bound given above. Along the way to this result, we simplify the proof of the so called abstract bound for the relative condition number of the domain decomposition preconditioner. In the part, related to the analysis of the interface sub-problem preconditioning, our technical tools are generalization of those used by Bramble, Pasciak and Schatz.
Output-Only Modal Analysis by Frequency Domain Decomposition
DEFF Research Database (Denmark)
Brincker, Rune; Zhang, Lingmi; Andersen, Palle
2000-01-01
approach where the modal parameters are estimated by simple peak picking. However, by introducing a decomposition of the spectral density function matrix, the response spectra can be separated into a set of single degree of freedom systems, each corresponding to an individual mode. By using...
Hybrid model decomposition of speech and noise in a radial basis function neural model framework
DEFF Research Database (Denmark)
Sørensen, Helge Bjarup Dissing; Hartmann, Uwe
1994-01-01
applied is based on a combination of the hidden Markov model (HMM) decomposition method, for speech recognition in noise, developed by Varga and Moore (1990) from DRA and the hybrid (HMM/RBF) recognizer containing hidden Markov models and radial basis function (RBF) neural networks, developed by Singer...... and Lippmann (1992) from MIT Lincoln Lab. The present authors modified the hybrid recognizer to fit into the decomposition method to achieve high performance speech recognition in noisy environments. The approach has been denoted the hybrid model decomposition method and it provides an optimal method...... for decomposition of speech and noise by using a set of speech pattern models and a noise model(s), each realized as an HMM/RBF pattern model...
Spatial, temporal, and hybrid decompositions for large-scale vehicle routing with time windows
Energy Technology Data Exchange (ETDEWEB)
Bent, Russell W [Los Alamos National Laboratory
2010-01-01
This paper studies the use of decomposition techniques to quickly find high-quality solutions to large-scale vehicle routing problems with time windows. It considers an adaptive decomposition scheme which iteratively decouples a routing problem based on the current solution. Earlier work considered vehicle-based decompositions that partitions the vehicles across the subproblems. The subproblems can then be optimized independently and merged easily. This paper argues that vehicle-based decompositions, although very effective on various problem classes also have limitations. In particular, they do not accommodate temporal decompositions and may produce spatial decompositions that are not focused enough. This paper then proposes customer-based decompositions which generalize vehicle-based decouplings and allows for focused spatial and temporal decompositions. Experimental results on class R2 of the extended Solomon benchmarks demonstrates the benefits of the customer-based adaptive decomposition scheme and its spatial, temporal, and hybrid instantiations. In particular, they show that customer-based decompositions bring significant benefits over large neighborhood search in contrast to vehicle-based decompositions.
Multiscale analysis of damage using dual and primal domain decomposition techniques
Lloberas-Valls, O.; Everdij, F.P.X.; Rixen, D.J.; Simone, A.; Sluys, L.J.
2014-01-01
In this contribution, dual and primal domain decomposition techniques are studied for the multiscale analysis of failure in quasi-brittle materials. The multiscale strategy essentially consists in decomposing the structure into a number of nonoverlapping domains and considering a refined spatial res
Pal, Arup Kumar
2017-01-01
Digital image watermarking has emerged as a promising solution for copyright protection. In this paper, a discrete cosine transform (DCT) and singular value decomposition (SVD) based hybrid robust image watermarking method using Arnold scrambling is proposed and simulated to protect the copyright of natural images. In this proposed scheme, before embedding, watermark is scrambled with Arnold scrambling. Then, the greyscale cover image and encrypted watermark logo are decomposed into non-overlapping blocks and subsequently some selected image blocks are transformed into the DCT domain for inserting the watermark blocks permanently. For better imperceptibility and effectiveness, in this proposed algorithm, watermark image blocks are embedded into singular values of selected blocks by multiplying with a feasible scaling factor. Simulation result demonstrates that robustness is achieved by recovering satisfactory watermark data from the reconstructed cover image after applying common geometric transformation attacks (such as rotation, flip operation, cropping, scaling, shearing and deletion of lines or columns operation), common enhancement technique attacks (such as low-pass filtering, histogram equalization, sharpening, gamma correction, noise addition) and jpeg compression attacks. PMID:28680684
Adaptive Aggregation Based Domain Decomposition Multigrid for the Lattice Wilson Dirac Operator
Frommer, Andreas; Krieg, Stefan; Leder, Björn; Rottmann, Matthias
2013-01-01
In lattice QCD computations a substantial amount of work is spent in solving discretized versions of the Dirac equation. Conventional Krylov solvers show critical slowing down for large system sizes and physically interesting parameter regions. We present a domain decomposition adaptive algebraic multigrid method used as a precondtioner to solve the "clover improved" Wilson discretization of the Dirac equation. This approach combines and improves two approaches, namely domain decomposition and adaptive algebraic multigrid, that have been used seperately in lattice QCD before. We show in extensive numerical test conducted with a parallel production code implementation that considerable speed-up over conventional Krylov subspace methods, domain decomposition methods and other hierarchical approaches for realistic system sizes can be achieved.
Lattice QCD with Domain Decomposition on Intel Xeon Phi Co-Processors
Energy Technology Data Exchange (ETDEWEB)
Heybrock, Simon; Joo, Balint; Kalamkar, Dhiraj D; Smelyanskiy, Mikhail; Vaidyanathan, Karthikeyan; Wettig, Tilo; Dubey, Pradeep
2014-12-01
The gap between the cost of moving data and the cost of computing continues to grow, making it ever harder to design iterative solvers on extreme-scale architectures. This problem can be alleviated by alternative algorithms that reduce the amount of data movement. We investigate this in the context of Lattice Quantum Chromodynamics and implement such an alternative solver algorithm, based on domain decomposition, on Intel Xeon Phi co-processor (KNC) clusters. We demonstrate close-to-linear on-chip scaling to all 60 cores of the KNC. With a mix of single- and half-precision the domain-decomposition method sustains 400-500 Gflop/s per chip. Compared to an optimized KNC implementation of a standard solver [1], our full multi-node domain-decomposition solver strong-scales to more nodes and reduces the time-to-solution by a factor of 5.
Lattice QCD with Domain Decomposition on Intel Xeon Phi Co-Processors
Heybrock, Simon; Kalamkar, Dhiraj D; Smelyanskiy, Mikhail; Vaidyanathan, Karthikeyan; Wettig, Tilo; Dubey, Pradeep
2014-01-01
The gap between the cost of moving data and the cost of computing continues to grow, making it ever harder to design iterative solvers on extreme-scale architectures. This problem can be alleviated by alternative algorithms that reduce the amount of data movement. We investigate this in the context of Lattice Quantum Chromodynamics and implement such an alternative solver algorithm, based on domain decomposition, on Intel Xeon Phi co-processor (KNC) clusters. We demonstrate close-to-linear on-chip scaling to all 60 cores of the KNC. With a mix of single- and half-precision the domain-decomposition method sustains 400-500 Gflop/s per chip. Compared to an optimized KNC implementation of a standard solver [1], our full multi-node domain-decomposition solver strong-scales to more nodes and reduces the time-to-solution by a factor of 5.
A Domain Decomposition Method for Time Fractional Reaction-Diffusion Equation
Directory of Open Access Journals (Sweden)
Chunye Gong
2014-01-01
Full Text Available The computational complexity of one-dimensional time fractional reaction-diffusion equation is O(N2M compared with O(NM for classical integer reaction-diffusion equation. Parallel computing is used to overcome this challenge. Domain decomposition method (DDM embodies large potential for parallelization of the numerical solution for fractional equations and serves as a basis for distributed, parallel computations. A domain decomposition algorithm for time fractional reaction-diffusion equation with implicit finite difference method is proposed. The domain decomposition algorithm keeps the same parallelism but needs much fewer iterations, compared with Jacobi iteration in each time step. Numerical experiments are used to verify the efficiency of the obtained algorithm.
Fast estimation of discretization error for FE problems solved by domain decomposition
Parret-Fréaud, Augustin; Gosselet, Pierre; Feyel, Frédéric; 10.1016/j.cma.2010.07.002
2012-01-01
This paper presents a strategy for a posteriori error estimation for substructured problems solved by non-overlapping domain decomposition methods. We focus on global estimates of the discretization error obtained through the error in constitutive relation for linear mechanical problems. Our method allows to compute error estimate in a fully parallel way for both primal (BDD) and dual (FETI) approaches of non-overlapping domain decomposition whatever the state (converged or not) of the associated iterative solver. Results obtained on an academic problem show that the strategy we propose is efficient in the sense that correct estimation is obtained with fully parallel computations; they also indicate that the estimation of the discretization error reaches sufficient precision in very few iterations of the domain decomposition solver, which enables to consider highly effective adaptive computational strategies.
Large Scale Simulation of Hydrogen Dispersion by a Stabilized Balancing Domain Decomposition Method
Directory of Open Access Journals (Sweden)
Qing-He Yao
2014-01-01
Full Text Available The dispersion behaviour of leaking hydrogen in a partially open space is simulated by a balancing domain decomposition method in this work. An analogy of the Boussinesq approximation is employed to describe the connection between the flow field and the concentration field. The linear systems of Navier-Stokes equations and the convection diffusion equation are symmetrized by a pressure stabilized Lagrange-Galerkin method, and thus a balancing domain decomposition method is enabled to solve the interface problem of the domain decomposition system. Numerical results are validated by comparing with the experimental data and available numerical results. The dilution effect of ventilation is investigated, especially at the doors, where flow pattern is complicated and oscillations appear in the past research reported by other researchers. The transient behaviour of hydrogen and the process of accumulation in the partially open space are discussed, and more details are revealed by large scale computation.
Non-conformal domain decomposition methods for time-harmonic Maxwell equations.
Shao, Yang; Peng, Zhen; Lim, Kheng Hwee; Lee, Jin-Fa
2012-09-08
We review non-conformal domain decomposition methods (DDMs) and their applications in solving electrically large and multi-scale electromagnetic (EM) radiation and scattering problems. In particular, a finite-element DDM, together with a finite-element tearing and interconnecting (FETI)-like algorithm, incorporating Robin transmission conditions and an edge corner penalty term, are discussed in detail. We address in full the formulations, and subsequently, their applications to problems with significant amounts of repetitions. The non-conformal DDM approach has also been extended into surface integral equation methods. We elucidate a non-conformal integral equation domain decomposition method and a generalized combined field integral equation method for modelling EM wave scattering from non-penetrable and penetrable targets, respectively. Moreover, a plane wave scattering from a composite mockup fighter jet has been simulated using the newly developed multi-solver domain decomposition method.
Multiscale Domain Decomposition Methods for Elliptic Problems with High Aspect Ratios
Institute of Scientific and Technical Information of China (English)
Jфrg Aarnes; Thomas Y. Hou
2002-01-01
In this paper we study some nonoverlapping domain decomposition methods for solving a class of elliptic problems arising from composite materials and flows in porous media which contain many spatial scales. Our preconditioner differs from traditional domain decomposition preconditioners by using a coarse solver which is adaptive to small scale heterogeneous features. While the convergence rate of traditional domain decomposition algorithms using coarse solvers based on linear or polynomial interpolations may deteriorate in the presence of rapid small scale oscillations or high aspect ratios, our preconditioner is applicable to multiplescale problems without restrictive assumptions and seems to have a convergence rate nearly independent of the aspect ratio within the substructures. A rigorous convergence analysis based on the Schwarz framework is carried out, and we demonstrate the efficiency and robustness of the proposed preconditioner through numerical experiments which include problems with multiple-scale coefficients, as well problems with continuous scales.
Domain decomposition algorithms for mixed methods for second-order elliptic problems
Energy Technology Data Exchange (ETDEWEB)
Chen, Zhangxin; Ewing, R.E.; Lazarov, R.
1996-04-01
In this paper domain decomposition algorithms for mixed finite element methods for linear second-order elliptic problems in R{sup 2} and R{sup 3} are developed. A convergence theory for two-level and multilevel Schwartz methods applied to the algorithms under consideration is given. It is shown that the condition number of these iterative methods is bounded uniformly from above in the same manner as in the theory of domain decomposition methods for conforming and nonconforming finite element methods for the same differential problems. Numerical experiments are presented to illustrate the present techniques. 40 refs., 3 figs., 2 tabs.
Domain decomposition for a mixed finite element method in three dimensions
Cai, Z.; Parashkevov, R.R.; Russell, T.F.; Wilson, J.D.; Ye, X.
2003-01-01
We consider the solution of the discrete linear system resulting from a mixed finite element discretization applied to a second-order elliptic boundary value problem in three dimensions. Based on a decomposition of the velocity space, these equations can be reduced to a discrete elliptic problem by eliminating the pressure through the use of substructures of the domain. The practicality of the reduction relies on a local basis, presented here, for the divergence-free subspace of the velocity space. We consider additive and multiplicative domain decomposition methods for solving the reduced elliptic problem, and their uniform convergence is established.
Modal Identification from Ambient Responses Using Frequency Domain Decomposition
DEFF Research Database (Denmark)
Brincker, Rune; Zhang, Lingmi; Andersen, Palle
2000-01-01
In this paper a new frequency domain technique is introduced for the modal identification from ambient responses, i.e. in the case where the modal parameters must be estimated without knowing the input exciting the system. By its user friendliness the technique is closely related to the classical...
Modal Identification from Ambient Responses using Frequency Domain Decomposition
DEFF Research Database (Denmark)
Brincker, Rune; Zhang, L.; Andersen, P.
2000-01-01
In this paper a new frequency domain technique is introduced for the modal identification from ambient responses, ie. in the case where the modal parameters must be estimated without knowing the input exciting the system. By its user friendliness the technique is closely related to the classical...
Energy Technology Data Exchange (ETDEWEB)
Tang Shaojie; Tang Xiangyang [Imaging and Medical Physics, Department of Radiology and Imaging Sciences, Emory University School of Medicine, 1701 Uppergate Dr., C-5018, Atlanta, Georgia 30322 (United States); School of Automation, Xi' an University of Posts and Telecommunications, Xi' an, Shaanxi 710121 (China); Imaging and Medical Physics, Department of Radiology and Imaging Sciences, Emory University School of Medicine, 1701 Uppergate Dr., C-5018, Atlanta, Georgia 30322 (United States)
2012-09-15
Purposes: The suppression of noise in x-ray computed tomography (CT) imaging is of clinical relevance for diagnostic image quality and the potential for radiation dose saving. Toward this purpose, statistical noise reduction methods in either the image or projection domain have been proposed, which employ a multiscale decomposition to enhance the performance of noise suppression while maintaining image sharpness. Recognizing the advantages of noise suppression in the projection domain, the authors propose a projection domain multiscale penalized weighted least squares (PWLS) method, in which the angular sampling rate is explicitly taken into consideration to account for the possible variation of interview sampling rate in advanced clinical or preclinical applications. Methods: The projection domain multiscale PWLS method is derived by converting an isotropic diffusion partial differential equation in the image domain into the projection domain, wherein a multiscale decomposition is carried out. With adoption of the Markov random field or soft thresholding objective function, the projection domain multiscale PWLS method deals with noise at each scale. To compensate for the degradation in image sharpness caused by the projection domain multiscale PWLS method, an edge enhancement is carried out following the noise reduction. The performance of the proposed method is experimentally evaluated and verified using the projection data simulated by computer and acquired by a CT scanner. Results: The preliminary results show that the proposed projection domain multiscale PWLS method outperforms the projection domain single-scale PWLS method and the image domain multiscale anisotropic diffusion method in noise reduction. In addition, the proposed method can preserve image sharpness very well while the occurrence of 'salt-and-pepper' noise and mosaic artifacts can be avoided. Conclusions: Since the interview sampling rate is taken into account in the projection domain
Institute of Scientific and Technical Information of China (English)
Wu Zhi-jian; Tang Zhi-long; Kang Li-shan
2003-01-01
This paper presents a parallel two level evolutionary algorithm based on domain decomposition for solving function optimization problem containing multiple solutions.By combining the characteristics of the global search and local search in each sub-domain, the former enables individual to draw closer to each optirma and keeps the diversity of individuals, while the latter selects local optimal solutions known as latent solutions in sub-domain. In the end, by selecting the global optimal solutions from latent solutions in each sub-domain, we can discover all the optimal solutions easily and quickly.
Dynamic load balancing algorithm for molecular dynamics based on Voronoi cells domain decompositions
Energy Technology Data Exchange (ETDEWEB)
Fattebert, J.-L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Richards, D.F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Glosli, J.N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2012-12-01
We present a new algorithm for automatic parallel load balancing in classical molecular dynamics. It assumes a spatial domain decomposition of particles into Voronoi cells. It is a gradient method which attempts to minimize a cost function by displacing Voronoi sites associated with each processor/sub-domain along steepest descent directions. Excellent load balance has been obtained for quasi-2D and 3D practical applications, with up to 440·10^{6} particles on 65,536 MPI tasks.
Stochastic domain decomposition for the solution of the two-dimensional magnetotelluric problem
Bihlo, Alexander; Haynes, Ronald D; Loredo-Osti, J Concepcion
2016-01-01
Stochastic domain decomposition is proposed as a novel method for solving the two-dimensional Maxwell's equations as used in the magnetotelluric method. The stochastic form of the exact solution of Maxwell's equations is evaluated using Monte-Carlo methods taking into consideration that the domain may be divided into neighboring sub-domains. These sub-domains can be naturally chosen by splitting the sub-surface domain into regions of constant (or at least continuous) conductivity. The solution over each sub-domain is obtained by solving Maxwell's equations in the strong form. The sub-domain solver used for this purpose is a meshless method resting on radial basis function based finite differences. The method is demonstrated by solving a number of classical magnetotelluric problems, including the quarter-space problem, the block-in-half-space problem and the triangle-in-half-space problem.
A Structural Model Decomposition Framework for Hybrid Systems Diagnosis
Daigle, Matthew; Bregon, Anibal; Roychoudhury, Indranil
2015-01-01
Nowadays, a large number of practical systems in aerospace and industrial environments are best represented as hybrid systems that consist of discrete modes of behavior, each defined by a set of continuous dynamics. These hybrid dynamics make the on-line fault diagnosis task very challenging. In this work, we present a new modeling and diagnosis framework for hybrid systems. Models are composed from sets of user-defined components using a compositional modeling approach. Submodels for residual generation are then generated for a given mode, and reconfigured efficiently when the mode changes. Efficient reconfiguration is established by exploiting causality information within the hybrid system models. The submodels can then be used for fault diagnosis based on residual generation and analysis. We demonstrate the efficient causality reassignment, submodel reconfiguration, and residual generation for fault diagnosis using an electrical circuit case study.
A Nitsche-based domain decomposition method for hypersingular integral equations
Chouly, Franz
2011-01-01
We introduce and analyze a Nitsche-based domain decomposition method for the solution of hypersingular integral equations. This method allows for discretizations with non-matching grids without the necessity of a Lagrangian multiplier, as opposed to the traditional mortar method. We prove its almost quasi-optimal convergence and underline the theory by a numerical experiment.
High performance domain decomposition methods on massively parallel architectures with FreeFEM++
Jolivet, Pierre; Dolean, Victorita; Hecht, Frédéric; Nataf, Frédéric; Prud'Homme, Christophe; Spillane, Nicole
2012-01-01
International audience; In this document, we present a parallel implementation in Freefem++ of scalable two-level domain decomposition methods. Numerical studies with highly heterogeneous problems are then performed on large clusters in order to assert the performance of our code.
DEFF Research Database (Denmark)
Jacobsen, Niels-Jørgen; Andersen, Palle; Brincker, Rune
2006-01-01
Enhanced Frequency Domain Decomposition technique for eliminating the influence of these harmonic components in the modal parameter extraction process. For various experiments, the quality of the method is assessed and compared to the results obtained using broadband stochastic excitation forces. Good...
APPLICATION OF DOMAIN DECOMPOSITION IN ACOUSTIC AND STRUCTURAL ACOUSTIC ANALYSIS
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Conventional element based methods for modeling acoustic problems are limited to low-frequency applications due to the huge computational efforts. For high-frequency applications, probabilistic techniques, such as statistical energy analysis (SEA), are used. For mid-frequency range, currently no adequate and mature simulation methods exist. Recently, wave based method has been developed which is based on the indirect TREFFTZ approach and has shown to be able to tackle problems in the mid-frequency range. In contrast with the element based methods, no discretization is required. A sufficient, but not necessary, condition for convergence of this method is that the acoustic problem domain is convex. Non-convex domains have to be partitioned into a number of (convex) subdomains. At the interfaces between subdomains, specific coupling conditions have to be imposed. The considered two-dimensional coupled vibro-acoustic problem illustrates the beneficial convergence rate of the proposed wave based prediction technique with high accuracy. The results show the new technique can be applied up to much higher frequencies.
Domain decomposition solvers for nonlinear multiharmonic finite element equations
Copeland, D. M.
2010-01-01
In many practical applications, for instance, in computational electromagnetics, the excitation is time-harmonic. Switching from the time domain to the frequency domain allows us to replace the expensive time-integration procedure by the solution of a simple elliptic equation for the amplitude. This is true for linear problems, but not for nonlinear problems. However, due to the periodicity of the solution, we can expand the solution in a Fourier series. Truncating this Fourier series and approximating the Fourier coefficients by finite elements, we arrive at a large-scale coupled nonlinear system for determining the finite element approximation to the Fourier coefficients. The construction of fast solvers for such systems is very crucial for the efficiency of this multiharmonic approach. In this paper we look at nonlinear, time-harmonic potential problems as simple model problems. We construct and analyze almost optimal solvers for the Jacobi systems arising from the Newton linearization of the large-scale coupled nonlinear system that one has to solve instead of performing the expensive time-integration procedure. © 2010 de Gruyter.
Domain and range decomposition methods for coded aperture x-ray coherent scatter imaging
Odinaka, Ikenna; Kaganovsky, Yan; O'Sullivan, Joseph A.; Politte, David G.; Holmgren, Andrew D.; Greenberg, Joel A.; Carin, Lawrence; Brady, David J.
2016-05-01
Coded aperture X-ray coherent scatter imaging is a novel modality for ascertaining the molecular structure of an object. Measurements from different spatial locations and spectral channels in the object are multiplexed through a radiopaque material (coded aperture) onto the detectors. Iterative algorithms such as penalized expectation maximization (EM) and fully separable spectrally-grouped edge-preserving reconstruction have been proposed to recover the spatially-dependent coherent scatter spectral image from the multiplexed measurements. Such image recovery methods fall into the category of domain decomposition methods since they recover independent pieces of the image at a time. Ordered subsets has also been utilized in conjunction with penalized EM to accelerate its convergence. Ordered subsets is a range decomposition method because it uses parts of the measurements at a time to recover the image. In this paper, we analyze domain and range decomposition methods as they apply to coded aperture X-ray coherent scatter imaging using a spectrally-grouped edge-preserving regularizer and discuss the implications of the increased availability of parallel computational architecture on the choice of decomposition methods. We present results of applying the decomposition methods on experimental coded aperture X-ray coherent scatter measurements. Based on the results, an underlying observation is that updating different parts of the image or using different parts of the measurements in parallel, decreases the rate of convergence, whereas using the parts sequentially can accelerate the rate of convergence.
Lahmiri, Salim
2016-08-01
The main purpose of this work is to explore the usefulness of fractal descriptors estimated in multi-resolution domains to characterize biomedical digital image texture. In this regard, three multi-resolution techniques are considered: the well-known discrete wavelet transform (DWT) and the empirical mode decomposition (EMD), and; the newly introduced; variational mode decomposition mode (VMD). The original image is decomposed by the DWT, EMD, and VMD into different scales. Then, Fourier spectrum based fractal descriptors is estimated at specific scales and directions to characterize the image. The support vector machine (SVM) was used to perform supervised classification. The empirical study was applied to the problem of distinguishing between normal and abnormal brain magnetic resonance images (MRI) affected with Alzheimer disease (AD). Our results demonstrate that fractal descriptors estimated in VMD domain outperform those estimated in DWT and EMD domains; and also those directly estimated from the original image.
Energy Technology Data Exchange (ETDEWEB)
Girardi, E.; Ruggieri, J.M. [CEA Cadarache, CEA/DEN/CAD/DER/SPRC/LEPH, 13 - Saint-Paul Lez Durance (France)
2003-07-01
The aim of this paper is to present the last developments made on a domain decomposition method applied to reactor core calculations. In this method, two kind of balance equation with two different numerical methods dealing with two different unknowns are coupled. In the first part the two balance transport equations (first order and second order one) are presented with the corresponding following numerical methods: Variational Nodal Method and Discrete Ordinate Nodal Method. In the second part, the Multi-Method/Multi-Domain algorithm is introduced by applying the Schwarz domain decomposition to the multigroup eigenvalue problem of the transport equation. The resulting algorithm is then provided. The projection operators used to coupled the two methods are detailed in the last part of the paper. Finally some preliminary numerical applications on benchmarks are given showing encouraging results. (authors)
Energy Technology Data Exchange (ETDEWEB)
Flauraud, E.
2004-05-01
In this thesis, we are interested in using domain decomposition methods for solving fluid flows in faulted porous media. This study comes within the framework of sedimentary basin modeling which its aim is to predict the presence of possible oil fields in the subsoil. A sedimentary basin is regarded as a heterogeneous porous medium in which fluid flows (water, oil, gas) occur. It is often subdivided into several blocks separated by faults. These faults create discontinuities that have a tremendous effect on the fluid flow in the basin. In this work, we present two approaches to model faults from the mathematical point of view. The first approach consists in considering faults as sub-domains, in the same way as blocks but with their own geological properties. However, because of the very small width of the faults in comparison with the size of the basin, the second and new approach consists in considering faults no longer as sub-domains, but as interfaces between the blocks. A mathematical study of the two models is carried out in order to investigate the existence and the uniqueness of solutions. Then; we are interested in using domain decomposition methods for solving the previous models. The main part of this study is devoted to the design of Robin interface conditions and to the formulation of the interface problem. The Schwarz algorithm can be seen as a Jacobi method for solving the interface problem. In order to speed up the convergence, this problem can be solved by a Krylov type algorithm (BICGSTAB). We discretize the equations with a finite volume scheme, and perform extensive numerical tests to compare the different methods. (author)
Energy Technology Data Exchange (ETDEWEB)
Girardi, E.; Ruggieri, J.M. [CEA Cadarache (DER/SPRC/LEPH), 13 - Saint-Paul-lez-Durance (France). Dept. d' Etudes des Reacteurs; Santandrea, S. [CEA Saclay, Dept. Modelisation de Systemes et Structures DM2S/SERMA/LENR, 91 - Gif sur Yvette (France)
2005-07-01
This paper describes a recently-developed extension of our 'Multi-methods,multi-domains' (MM-MD) method for the solution of the multigroup transport equation. Based on a domain decomposition technique, our approach allows us to treat the one-group equation by cooperatively employing several numerical methods together. In this work, we describe the coupling between the Method of Characteristics (integro-differential equation, unstructured meshes) with the Variational Nodal Method (even parity equation, cartesian meshes). Then, the coupling method is applied to the benchmark model of the Phebus experimental facility (Cea Cadarache). Our domain decomposition method give us the capability to employ a very fine mesh in describing a particular fuel bundle with an appropriate numerical method (MOC), while using a much large mesh size in the rest of the core, in conjunction with a coarse-mesh method (VNM). This application shows the benefits of our MM-MD approach, in terms of accuracy and computing time: the domain decomposition method allows us to reduce the Cpu time, while preserving a good accuracy of the neutronic indicators: reactivity, core-to-bundle power coupling coefficient and flux error. (authors)
An improved convergence bound for aggregation-based domain decomposition preconditioners.
Energy Technology Data Exchange (ETDEWEB)
Shadid, John Nicolas; Sala, Marzio; Tuminaro, Raymond Stephen
2005-06-01
In this paper we present a two-level overlapping domain decomposition preconditioner for the finite-element discretization of elliptic problems in two and three dimensions. The computational domain is partitioned into overlapping subdomains, and a coarse space correction, based on aggregation techniques, is added. Our definition of the coarse space does not require the introduction of a coarse grid. We consider a set of assumptions on the coarse basis functions to bound the condition number of the resulting preconditioned system. These assumptions involve only geometrical quantities associated with the aggregates and the subdomains. We prove that the condition number using the two-level additive Schwarz preconditioner is O(H/{delta} + H{sub 0}/{delta}), where H and H{sub 0} are the diameters of the subdomains and the aggregates, respectively, and {delta} is the overlap among the subdomains and the aggregates. This extends the bounds presented in [C. Lasser and A. Toselli, Convergence of some two-level overlapping domain decomposition preconditioners with smoothed aggregation coarse spaces, in Recent Developments in Domain Decomposition Methods, Lecture Notes in Comput. Sci. Engrg. 23, L. Pavarino and A. Toselli, eds., Springer-Verlag, Berlin, 2002, pp. 95-117; M. Sala, Domain Decomposition Preconditioners: Theoretical Properties, Application to the Compressible Euler Equations, Parallel Aspects, Ph.D. thesis, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland, 2003; M. Sala, Math. Model. Numer. Anal., 38 (2004), pp. 765-780]. Numerical experiments on a model problem are reported to illustrate the performance of the proposed preconditioner.
Domain Decomposition of a Constructive Solid Geometry Monte Carlo Transport Code
Energy Technology Data Exchange (ETDEWEB)
O' Brien, M J; Joy, K I; Procassini, R J; Greenman, G M
2008-12-07
Domain decomposition has been implemented in a Constructive Solid Geometry (CSG) Monte Carlo neutron transport code. Previous methods to parallelize a CSG code relied entirely on particle parallelism; but in our approach we distribute the geometry as well as the particles across processors. This enables calculations whose geometric description is larger than what could fit in memory of a single processor, thus it must be distributed across processors. In addition to enabling very large calculations, we show that domain decomposition can speed up calculations compared to particle parallelism alone. We also show results of a calculation of the proposed Laser Inertial-Confinement Fusion-Fission Energy (LIFE) facility, which has 5.6 million CSG parts.
Moussawi, Ali
2015-02-24
Summary: The post-treatment of (3D) displacement fields for the identification of spatially varying elastic material parameters is a large inverse problem that remains out of reach for massive 3D structures. We explore here the potential of the constitutive compatibility method for tackling such an inverse problem, provided an appropriate domain decomposition technique is introduced. In the method described here, the statically admissible stress field that can be related through the known constitutive symmetry to the kinematic observations is sought through minimization of an objective function, which measures the violation of constitutive compatibility. After this stress reconstruction, the local material parameters are identified with the given kinematic observations using the constitutive equation. Here, we first adapt this method to solve 3D identification problems and then implement it within a domain decomposition framework which allows for reduced computational load when handling larger problems.
A domain decomposition study of massively parallel computing in compressible gas dynamics
Energy Technology Data Exchange (ETDEWEB)
Wong, C.C.; Blottner, F.G.; Payne, J.L. [Sandia National Labs., Albuquerque, NM (United States); Soetrisno, M. [Amtec Engineering, Inc., Bellevue, WA (United States)
1995-01-01
The appropriate utilization of massively parallel computers for solving the Navier-Stokes equations is investigated and determined from an engineering perspective. The issues investigated are: (1) Should strip or patch domain decomposition of the spatial mesh be used to reduce computer time? (2) How many computer nodes should be used for a problem with a given sized mesh to reduce computer time? (3) Is the convergence of the Navier-Stokes solution procedure (LU-SGS) adversely influenced by the domain decomposition approach? The results of the paper show that the present Navier-Stokes solution technique has good performance on a massively parallel computer for transient flow problems. For steady-state problems with a large number of mesh cells, the solution procedure will require significant computer time due to an increased number of iterations to achieve a converged solution. There is an optimum number of computer nodes to use for a problem with a given global mesh size.
Adaptive Aggregation-based Domain Decomposition Multigrid for Twisted Mass Fermions
Alexandrou, Constantia; Finkenrath, Jacob; Frommer, Andreas; Kahl, Karsten; Rottmann, Matthias
2016-01-01
The Adaptive Aggregation-based Domain Decomposition Multigrid method (arXiv:1303.1377) is extended for two degenerate flavors of twisted mass fermions. By fine-tuning the parameters we achieve a speed-up of the order of hundred times compared to the conjugate gradient algorithm for the physical value of the pion mass. A thorough analysis of the aggregation parameters is presented, which provides a novel insight into multigrid methods for lattice QCD independently of the fermion discretization.
A domain decomposition method for the efficient direct simulation of aeroacoustic problems
Utzmann, Jens
2008-01-01
A novel domain decomposition approach is developed in this thesis, which significantly accelerates the direct simulation of aeroacoustic problems. All relevant scales must be resolved with high accuracy, from the small, noise generating flow features (e.g., vortices) to the sound with small pressure amplitudes and large wavelengths. Furthermore, the acoustic waves must be propagated over great distances and without dissipation and dispersion errors. In order to keep the computational effort w...
Energy Technology Data Exchange (ETDEWEB)
Griebel, M. [Technische Universitaet Muenchen (Germany)
1994-12-31
In recent years, it has turned out that many modern iterative algorithms (multigrid schemes, multilevel preconditioners, domain decomposition methods etc.) for solving problems resulting from the discretization of PDEs can be interpreted as additive (Jacobi-like) or multiplicative (Gauss-Seidel-like) subspace correction methods. The key to their analysis is the study of certain metric properties of the underlying splitting of the discretization space V into a sum of subspaces V{sub j}, j = 1{hor_ellipsis}, J resp. of the variational problem on V into auxiliary problems on these subspaces. Here, the author proposes a modified approach to the abstract convergence theory of these additive and multiplicative Schwarz iterative methods, that makes the relation to traditional iteration methods more explicit. To this end he introduces the enlarged Hilbert space V = V{sub 0} x {hor_ellipsis} x V{sub j} which is nothing else but the usual construction of the Cartesian product of the Hilbert spaces V{sub j} and use it now in the discretization process. This results in an enlarged, semidefinite linear system to be solved instead of the usual definite system. Then, modern multilevel methods as well as domain decomposition methods simplify to just traditional (block-) iteration methods. Now, the convergence analysis can be carried out directly for these traditional iterations on the enlarged system, making convergence proofs of multilevel and domain decomposition methods more clear, or, at least, more classical. The terms that enter the convergence proofs are exactly the ones of the classical iterative methods. It remains to estimate them properly. The convergence proof itself follow basically line by line the old proofs of the respective traditional iterative methods. Additionally, new multilevel/domain decomposition methods are constructed straightforwardly by now applying just other old and well known traditional iterative methods to the enlarged system.
Directory of Open Access Journals (Sweden)
Dolean Victorita
2014-07-01
Full Text Available Multiphase, compositional porous media flow models lead to the solution of highly heterogeneous systems of Partial Differential Equations (PDE. We focus on overlapping Schwarz type methods on parallel computers and on multiscale methods. We present a coarse space [Nataf F., Xiang H., Dolean V., Spillane N. (2011 SIAM J. Sci. Comput. 33, 4, 1623-1642] that is robust even when there are such heterogeneities. The two-level domain decomposition approach is compared to multiscale methods.
A frequency-spatial domain decomposition (FSDD) method for operational modal analysis
Zhang, Lingmi; Wang, Tong; Tamura, Yukio
2010-07-01
Following a brief review of the development of operational modal identification techniques, we describe a new method named frequency-spatial domain decomposition (FSDD), with theoretical background, formulation and algorithm. Three typical applications to civil engineering structures are presented to demonstrate the procedure and features of the method: a large-span stadium roof for finite-element model verification, a highway bridge for damage detection and a long-span cable-stayed bridge for structural health monitoring.
Previti, Alberto; Furfaro, Roberto; Picca, Paolo; Ganapol, Barry D; Mostacci, Domiziano
2011-08-01
This paper deals with finding accurate solutions for photon transport problems in highly heterogeneous media fastly, efficiently and with modest memory resources. We propose an extended version of the analytical discrete ordinates method, coupled with domain decomposition-derived algorithms and non-linear convergence acceleration techniques. Numerical performances are evaluated using a challenging case study available in the literature. A study of accuracy versus computational time and memory requirements is reported for transport calculations that are relevant for remote sensing applications.
Java-Based Coupling for Parallel Predictive-Adaptive Domain Decomposition
Directory of Open Access Journals (Sweden)
Cécile Germain‐Renaud
1999-01-01
Full Text Available Adaptive domain decomposition exemplifies the problem of integrating heterogeneous software components with intermediate coupling granularity. This paper describes an experiment where a data‐parallel (HPF client interfaces with a sequential computation server through Java. We show that seamless integration of data‐parallelism is possible, but requires most of the tools from the Java palette: Java Native Interface (JNI, Remote Method Invocation (RMI, callbacks and threads.
Energy Technology Data Exchange (ETDEWEB)
Jemcov, A.; Matovic, M.D. [Queen`s Univ., Kingston, Ontario (Canada)
1996-12-31
This paper examines the sparse representation and preconditioning of a discrete Steklov-Poincare operator which arises in domain decomposition methods. A non-overlapping domain decomposition method is applied to a second order self-adjoint elliptic operator (Poisson equation), with homogeneous boundary conditions, as a model problem. It is shown that the discrete Steklov-Poincare operator allows sparse representation with a bounded condition number in wavelet basis if the transformation is followed by thresholding and resealing. These two steps combined enable the effective use of Krylov subspace methods as an iterative solution procedure for the system of linear equations. Finding the solution of an interface problem in domain decomposition methods, known as a Schur complement problem, has been shown to be equivalent to the discrete form of Steklov-Poincare operator. A common way to obtain Schur complement matrix is by ordering the matrix of discrete differential operator in subdomain node groups then block eliminating interface nodes. The result is a dense matrix which corresponds to the interface problem. This is equivalent to reducing the original problem to several smaller differential problems and one boundary integral equation problem for the subdomain interface.
A Dual Super-Element Domain Decomposition Approach for Parallel Nonlinear Finite Element Analysis
Jokhio, G. A.; Izzuddin, B. A.
2015-05-01
This article presents a new domain decomposition method for nonlinear finite element analysis introducing the concept of dual partition super-elements. The method extends ideas from the displacement frame method and is ideally suited for parallel nonlinear static/dynamic analysis of structural systems. In the new method, domain decomposition is realized by replacing one or more subdomains in a "parent system," each with a placeholder super-element, where the subdomains are processed separately as "child partitions," each wrapped by a dual super-element along the partition boundary. The analysis of the overall system, including the satisfaction of equilibrium and compatibility at all partition boundaries, is realized through direct communication between all pairs of placeholder and dual super-elements. The proposed method has particular advantages for matrix solution methods based on the frontal scheme, and can be readily implemented for existing finite element analysis programs to achieve parallelization on distributed memory systems with minimal intervention, thus overcoming memory bottlenecks typically faced in the analysis of large-scale problems. Several examples are presented in this article which demonstrate the computational benefits of the proposed parallel domain decomposition approach and its applicability to the nonlinear structural analysis of realistic structural systems.
Singh, Phool; Yadav, A. K.; Singh, Kehar
2017-04-01
A novel scheme for image encryption of phase images is proposed, using fractional Hartley transform followed by Arnold transform and singular value decomposition in the frequency domain. Since the plaintext is a phase image, the mask used in the spatial domain is a random amplitude mask. The proposed scheme has been validated for grayscale images and is sensitive to the encryption parameters such as the order of the Arnold transform and the fractional orders of the Hartley transform. We have also evaluated the scheme's resistance to the well-known noise and occlusion attacks.
Mechanical and assembly units of viral capsids identified via quasi-rigid domain decomposition.
Directory of Open Access Journals (Sweden)
Guido Polles
Full Text Available Key steps in a viral life-cycle, such as self-assembly of a protective protein container or in some cases also subsequent maturation events, are governed by the interplay of physico-chemical mechanisms involving various spatial and temporal scales. These salient aspects of a viral life cycle are hence well described and rationalised from a mesoscopic perspective. Accordingly, various experimental and computational efforts have been directed towards identifying the fundamental building blocks that are instrumental for the mechanical response, or constitute the assembly units, of a few specific viral shells. Motivated by these earlier studies we introduce and apply a general and efficient computational scheme for identifying the stable domains of a given viral capsid. The method is based on elastic network models and quasi-rigid domain decomposition. It is first applied to a heterogeneous set of well-characterized viruses (CCMV, MS2, STNV, STMV for which the known mechanical or assembly domains are correctly identified. The validated method is next applied to other viral particles such as L-A, Pariacoto and polyoma viruses, whose fundamental functional domains are still unknown or debated and for which we formulate verifiable predictions. The numerical code implementing the domain decomposition strategy is made freely available.
Energy Technology Data Exchange (ETDEWEB)
Jo, Yu Gwon; Cho, Nam Zin [KAIST, Daejeon (Korea, Republic of)
2014-10-15
The OLG iteration scheme uses overlapping regions for each local problem solved by continuous-energy MC calculation to reduce errors in inaccurate boundary conditions (BCs) that are caused by discretization in space, energy, and angle. However, the overlapping region increases computational burdens and the discretized BCs for continuous-energy MC calculation result in an inaccurate global p-CMFD solution. On the other hand, there also have been several studies on the direct domain decomposed MC calculation where each processor simulates particles within its own domain and exchanges the particles crossing the domain boundary between processors with certain frequency. The efficiency of this method depends on the message checking frequency and the buffer size. Furthermore, it should overcome the load-imbalance problem for better parallel efficiency. Recently, fission and surface source (FSS) iteration method based on banking both fission and surface sources for the next iteration (i.e., cycle) was proposed to give exact BCs for non overlapping local problems in domain decomposition and tested in one-dimensional continuous-energy reactor problems. In this paper, the FSS iteration method is combined with a source splitting scheme to reduce the load imbalance problem and achieve global variance reduction. The performances are tested on a two dimensional continuous-energy reactor problem with domain-based parallelism and compared with the FSS iteration without source splitting. Numerical results show the improvements of the FSS iteration with source splitting. This paper describes the FSS iteration scheme in the domain decomposition method and proposes the FSS iteration combined with the source splitting based on the number of sampled sources, reducing the load-imbalance problem in domain-based parallelism and achieving global variance reduction.
Institute of Scientific and Technical Information of China (English)
Yi-rang Yuan
2007-01-01
For a coupled system of multiplayer dynamics of fluids in porous media,the characteristic finite element domain decomposition procedures applicable to parallel arithmetic are put forward.Techniques such as calculus of variations,domain decomposition,characteristic method,negative norm estimate,energy method and the theory of prior estimates are adopted.Optimal order estimates in L2 norm are derived for the error in the approximate solution.
Energy Technology Data Exchange (ETDEWEB)
Li,Jing; Tu, Xuemin
2008-12-10
A variant of balancing domain decomposition method by constraints (BDDC) is proposed for solving a class of indefinite system of linear equations, which arises from the finite element discretization of the Helmholtz equation of time-harmonic wave propagation in a bounded interior domain. The proposed BDDC algorithm is closely related to the dual-primal finite element tearing and interconnecting algorithm for solving Helmholtz equations (FETI-DPH). Under the condition that the diameters of the subdomains are small enough, the rate of convergence is established which depends polylogarithmically on the dimension of the individual subdomain problems and which improves with the decrease of the subdomain diameters. These results are supported by numerical experiments of solving a Helmholtz equation on a two-dimensional square domain.
Institute of Scientific and Technical Information of China (English)
LIAO HongLin; SHI HanSheng; SUN ZhiZhong
2009-01-01
Corrected explicit-implicit domain decomposition (CEIDD) algorithms are studied for parallel approximation of semilinear parabolic problems on distributed memory processors. It is natural to divide the spatial domain into some smaller parallel strips and cells using the simplest straight-line interface (SI). By using the Leray-Schauder fixed-point theorem and the discrete energy method, it is shown that the resulting CEIDD-SI algorithm is uniquely solvable, unconditionally stable and convergent. The CEIDD-SI method always suffers from the globalization of data communication when interior boundaries cross into each other inside the domain. To overcome this disadvantage, a composite interface (CI) that consists of straight segments and zigzag fractions is suggested. The corresponding CEIDD-CI algorithm is proven to be solvable, stable and convergent. Numerical experiments are presented to support the theoretical results.
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
It was proved numerically that the Domain Decomposition Method (DDM) with one layer overlapping grids is identical to the block iterative method of linear algebra equations. The results obtained using DDM could be in reasonable aggeement with the results of full-domain simulation. With the three dimensional solver developed by the authors, the flow field in a pipe was simulated using the full-domain DDM with one layer overlapping grids and with patched grids respectively. Both of the two cases led to the convergent solution. Further research shows the superiority of the DDM with one layer overlapping grids to the DDM with patched grids. A comparison between the numerical results obtained by the authors and the experimental results given by Enayet[3] shows that the numerical results are reasonable.
Investigation of Ag2O Thermal Decomposition by Terahertz Time-Domain Spectroscopy
Institute of Scientific and Technical Information of China (English)
CHEN Hua; WANG Li
2009-01-01
Application of terahertz time-domain spectroscopy is demonstrated to study the process of Ag2O thermal decomposition. In the process of decomposition, the time-resolved signals are characterized by broad oscillations and decreased intensity, and THz pulse essentially contains two broad spectral components: one centered at around 0.35 THz and a band with a maximum at around 0.81 THz shift to 0.71 THz. Optical absorption spectra of different specimens are studied in the frequency range 0.3-1.4 THz and the data are analyzed by the relevant theory of the effective medium approach combined with the Drude-Lorentz model. The analysis suggests that optical properties stem from the Drude term for the metallic phase and the Lorentz term for the insulator phase in the complex system.
Adaptive aggregation-based domain decomposition multigrid for twisted mass fermions
Alexandrou, Constantia; Bacchio, Simone; Finkenrath, Jacob; Frommer, Andreas; Kahl, Karsten; Rottmann, Matthias
2016-12-01
The adaptive aggregation-base domain decomposition multigrid method [A. Frommer et al., SIAM J. Sci. Comput. 36, A1581 (2014)] is extended for two degenerate flavors of twisted mass fermions. By fine-tuning the parameters we achieve a speed-up of the order of a hundred times compared to the conjugate gradient algorithm for the physical value of the pion mass. A thorough analysis of the aggregation parameters is presented, which provides a novel insight into multigrid methods for lattice quantum chromodynamics independently of the fermion discretization.
Analysis of a Reflectarray by Using an Iterative Domain Decomposition Technique
Directory of Open Access Journals (Sweden)
Carlos Delgado
2012-01-01
Full Text Available We present an efficient method for the analysis of different objects that may contain a complex feeding system and a reflector structure. The approach is based on a domain decomposition technique that divides the geometry into several parts to minimize the vast computational resources required when applying a full wave method. This technique is also parallelized by using the Message Passing Interface to minimize the memory and time requirements of the simulation. A reflectarray analysis serves as an example of the proposed approach.
DEFF Research Database (Denmark)
Brincker, Rune; Andersen, Palle; Zhang, Lingmi
2007-01-01
As a part of a research project co-founded by the European Community, a series of 15 damage tests were performed on a prestressed concrete highway bridge in Switzerland. The ambient response of the bridge was recorded for each damage case. A dense array of instruments allowed the identification...... of a modal model with a total of 408 degrees of freedom. Six modes were identified in the frequency range from 0 to 16.7 Hz. The objective of this paper is to demonstrate the effectiveness of the Frequency Domain Decomposition (FDD) technique for modal identification of large structures. A second objective...
DEFF Research Database (Denmark)
Brincker, Rune; Andersen, P.; Zhang, L.
2002-01-01
As a part of a research project co-founded by the European Community, a series of 15 damage tests were performed on a prestressed concrete highway bridge in Switzerland. The ambient response of the bridge was recorded for each damage case. A dense array of instruments allowed the identification...... of a modal model with a total of 408 degrees of freedom. Six modes were identified in the frequency range from 0 to 16.7 Hz. The objective of this paper is to demonstrate the effectiveness of the Frequency Domain Decomposition (FDD) technique for modal identification of large structures. A second objective...
Local Exponential Methods: a domain decomposition approach to exponential time integration of PDEs
Bonaventura, Luca
2015-01-01
A local approach to the time integration of PDEs by exponential methods is proposed, motivated by theoretical estimates by A.Iserles on the decay of off-diagonal terms in the exponentials of sparse matrices. An overlapping domain decomposition technique is outlined, that allows to replace the computation of a global exponential matrix by a number of independent and easily parallelizable local problems. Advantages and potential problems of the proposed technique are discussed. Numerical experiments on simple, yet relevant model problems show that the resulting method allows to increase computational efficiency with respect to standard implementations of exponential methods.
Domain decomposition methods for a class of integro-partial differential equations
Califano, Giovanna; Conte, Dajana
2016-10-01
This paper deals with the construction of Schwarz Waveform Relaxation (SWR) methods for fractional diffusion-wave equations. SWR methods are a class of domain decomposition algorithms to solve evolution problems in parallel and have been mainly developed and analysed for several kinds of PDEs. We first analyse the convergence behaviour of the classical SWR method applied to fractional diffusion-wave equations, showing that Dirichlet boundary conditions at the artificial interfaces slow down the convergence of the method. Then, we construct optimal SWR methods, by providing the transmission conditions which assure convergence in two iterations.
Institute of Scientific and Technical Information of China (English)
Ju-e Yang; De-hao Yu
2006-01-01
In this paper, we are concerned with a non-overlapping domain decomposition method (DDM) for exterior transmission problems in the plane. Based on the natural boundary integral operator, we combine the DDM with a Dirichlet-to-Neumann (DtN) mapping and provide the numerical analysis with nonmatching grids. The weak continuity of the approximation solutions on the interface is imposed by a dual basis multiplier. We show that this multiplier space can generate optimal error estimate and obtain the corresponding rate of convergence. Finally, several numerical examples confirm the theoretical results.
DOMAIN DECOMPOSITION WITH NON-MATCHING GRIDS FOR COUPLING OF FEM AND NATURAL BEM
Institute of Scientific and Technical Information of China (English)
YANG Jue; HU Qiya; YU Dehao
2005-01-01
In this paper, we introduce a domain decomposition method with non-matching grids for solving Dirichlet exterior boundary problems by coupling of finite element method(FEM) and natural boundary element method(BEM). We first derive the optimal energy error estimate of the nonconforming approximation generated by this method. Then we apply a Dirichlet-Neumann(D-N) alternating algorithm to solve the coupled discrete system. It will be shown that such iterative method possesses the optimal convergence. The numerical experiments testify our theoretical results.
Abuturab, Muhammad Rafiq
2014-06-01
A new color image security system based on singular value decomposition (SVD) in gyrator transform (GT) domains is proposed. In the encryption process, a color image is decomposed into red, green and blue channels. Each channel is independently modulated by random phase masks and then separately gyrator transformed at different parameters. The three gyrator spectra are joined by multiplication to get one gray ciphertext. The ciphertext is separated into U, S, and V parts by SVD. All the three parts are individually gyrator transformed at different transformation angles. The three encoded information can be assigned to different authorized users for highly secure verification. Only when all the authorized users place the U, S, and V parts in correct multiplication order in the verification system, the correct information can be obtained with all the right keys. In the proposed method, SVD offers one-way asymmetrical decomposition algorithm and it is an optimal matrix decomposition in a least-square sense. The transformation angles of GT provide very sensitive additional keys. The pre-generated keys for red, green and blue channels are served as decryption (private) keys. As all the three encrypted parts are the gray scale ciphertexts with stationary white noise distributions, which have camouflage property to some extent. These advantages enhance the security and robustness. Numerical simulations are presented to support the viability of the proposed verification system.
Rafiq Abuturab, Muhammad
2016-06-01
A new multiple color-image authentication system based on HSI (Hue-Saturation-Intensity) color space and QR decomposition in gyrator domains is proposed. In this scheme, original color images are converted from RGB (Red-Green-Blue) color spaces to HSI color spaces, divided into their H, S, and I components, and then obtained corresponding phase-encoded components. All the phase-encoded H, S, and I components are individually multiplied, and then modulated by random phase functions. The modulated H, S, and I components are convoluted into a single gray image with asymmetric cryptosystem. The resulting image is segregated into Q and R parts by QR decomposition. Finally, they are independently gyrator transformed to get their encoded parts. The encoded Q and R parts should be gathered without missing anyone for decryption. The angles of gyrator transform afford sensitive keys. The protocol based on QR decomposition of encoded matrix and getting back decoded matrix after multiplying matrices Q and R, enhances the security level. The random phase keys, individual phase keys, and asymmetric phase keys provide high robustness to the cryptosystem. Numerical simulation results demonstrate that this scheme is the superior than the existing techniques.
Directory of Open Access Journals (Sweden)
Sushanta Ghuku
2016-09-01
In the present bar problem, only one such singularity point arising from the application of a concentrated axial load, is considered. Governing equation of the problem is derived from equilibrium condition and expressed in variational form with assumed displacement field by using direct variational principle. The computational domain is divided into two sub-domains based on the location of singularity point within the domain. An approximate solution of the governing equation is obtained assuming a series expression of the unknown variable by using Galerkin's principle. This approximation is carried out by a linear combination of sets of orthogonal co-ordinate functions which satisfy prescribed conditions at three points. The three conditions comprises of two boundary conditions and another condition at the point of application of concentrated load. The solution algorithm is implemented with the help of MATLAB® computational simulation software. The problem is also studied by using energy functional based variational method and an identical solution is observed. The present analysis highlights the generalized application of domain decomposition method based on variational principle in solving structural problems having singularities in domain.
A domain decomposition method for modelling Stokes flow in porous materials
Liu, Guangli; Thompson, Karsten E.
2002-04-01
An algorithm is presented for solving the Stokes equation in large disordered two-dimensional porous domains. In this work, it is applied to random packings of discs, but the geometry can be essentially arbitrary. The approach includes the subdivision of the domain and a subsequent application of boundary integral equations to the subdomains. This gives a block diagonal matrix with sparse off-block components that arise from shared variables on internal subdomain boundaries. The global problem is solved using a biconjugate gradient routine with preconditioning. Results show that the effectiveness of the preconditioner is strongly affected by the subdomain structure, from which a methodology is proposed for the domain decomposition step. A minimum is observed in the solution time versus subdomain size, which is governed by the time required for preconditioning, the time for vector multiplications in the biconjugate gradient routine, the iterative convergence rate and issues related to memory allocation. The method is demonstrated on various domains including a random 1000-particle domain. The solution can be used for efficient recovery of point velocities, which is discussed in the context of stochastic modelling of solute transport. Copyright
A novel moving mesh method based on the domain decomposition for traveling singular sources problems
Zhou, Xiaoyan; Liang, Keiwei
2012-01-01
This paper studies the numerical solution of traveling singular sources problems. A big challenge is the sources move with different speeds. Our work focus on a moving mesh method based on the domain decomposition. A predictor-corrector algorithm is derived to simulate the position of singular sources, which are described by some ordinary differential equations. The whole domain is splitted into several subdomains according to the positions of the sources. The endpoints of each subdomain are two adjacent sources. In each subdomain, moving mesh method is respectively applied. Moreover, the computation of jump $[\\dot{u}]$ is avoided and there are only two different cases discussed in the discretization of the PDE. Furthermore, the new method has a desired second-order of the spacial convergence. Numerical examples are presented to illustrate the convergence rates and the efficiency of the method. Blow-up phenomenon is also investigated for various motions of the sources.
Le, Thien-Phu; Argoul, Pierre
2016-12-01
This paper proposes a new modal identification method of ambient vibration responses. The application of the singular value decomposition to continuous wavelet transform of power spectral density matrix gives singular values and singular vectors in frequency-scale domain. Analytical development shows a direct relation between local maxima in frequency-scale representation of singular values and modal parameters. This relation is then carried on for the identification of modal parameters via a complete practical procedure. The main novelties of this work involve the new formulation in frequency-scale domain and the capacity for the identification of modal parameters without the step of ridges extraction in comparison with previous wavelet-based modal identification methods.
Spatiotemporal Domain Decomposition for Massive Parallel Computation of Space-Time Kernel Density
Hohl, A.; Delmelle, E. M.; Tang, W.
2015-07-01
Accelerated processing capabilities are deemed critical when conducting analysis on spatiotemporal datasets of increasing size, diversity and availability. High-performance parallel computing offers the capacity to solve computationally demanding problems in a limited timeframe, but likewise poses the challenge of preventing processing inefficiency due to workload imbalance between computing resources. Therefore, when designing new algorithms capable of implementing parallel strategies, careful spatiotemporal domain decomposition is necessary to account for heterogeneity in the data. In this study, we perform octtree-based adaptive decomposition of the spatiotemporal domain for parallel computation of space-time kernel density. In order to avoid edge effects near subdomain boundaries, we establish spatiotemporal buffers to include adjacent data-points that are within the spatial and temporal kernel bandwidths. Then, we quantify computational intensity of each subdomain to balance workloads among processors. We illustrate the benefits of our methodology using a space-time epidemiological dataset of Dengue fever, an infectious vector-borne disease that poses a severe threat to communities in tropical climates. Our parallel implementation of kernel density reaches substantial speedup compared to sequential processing, and achieves high levels of workload balance among processors due to great accuracy in quantifying computational intensity. Our approach is portable of other space-time analytical tests.
Domain Decomposition Preconditioners for Multiscale Flows in High-Contrast Media
Galvis, Juan
2010-01-01
In this paper, we study domain decomposition preconditioners for multiscale flows in high-contrast media. We consider flow equations governed by elliptic equations in heterogeneous media with a large contrast in the coefficients. Our main goal is to develop domain decomposition preconditioners with the condition number that is independent of the contrast when there are variations within coarse regions. This is accomplished by designing coarse-scale spaces and interpolators that represent important features of the solution within each coarse region. The important features are characterized by the connectivities of high-conductivity regions. To detect these connectivities, we introduce an eigenvalue problem that automatically detects high-conductivity regions via a large gap in the spectrum. A main observation is that this eigenvalue problem has a few small, asymptotically vanishing eigenvalues. The number of these small eigenvalues is the same as the number of connected high-conductivity regions. The coarse spaces are constructed such that they span eigenfunctions corresponding to these small eigenvalues. These spaces are used within two-level additive Schwarz preconditioners as well as overlapping methods for the Schur complement to design preconditioners. We show that the condition number of the preconditioned systems is independent of the contrast. More detailed studies are performed for the case when the high-conductivity region is connected within coarse block neighborhoods. Our numerical experiments confirm the theoretical results presented in this paper. © 2010 Society for Industrial and Applied Mathematics.
Yamamoto, T.; Brewster, R.; Safran, S. A.
2010-07-01
We use a liquid-crystal model to predict that hybrid lipids (lipids that have one saturated and one unsaturated tail) can stabilize line interfaces between domains in mixed membranes of saturated lipids, hybrid lipids, and cholesterol (SHC membranes). The model predicts the phase separation of SHC membranes with both parabolic and loop binodals depending on the cholesterol concentration, modeled via an effective pressure. In some cases, the hybrid lipids can reduce the line tension to zero in SHC membranes at temperatures that approach the critical temperature as the pressure is increased. The differences in the hybrid saturated tail conformational order in bulk and at the interface are responsible for the reduction of the line tension.
A Hybrid Decomposition Parallel Implementation of the Car-Parrinello Method
Wiggs, J K; Wiggs, James K.; Jonsson, Hannes
1994-01-01
We have developed a flexible hybrid decomposition parallel implementation of the first-principles molecular dynamics algorithm of Car and Parrinello. The code allows the problem to be decomposed either spatially, over the electronic orbitals, or any combination of the two. Performance statistics for 32, 64, 128 and 512 Si atom runs on the Touchstone Delta and Intel Paragon parallel supercomputers and comparison with the performance of an optimized code running the smaller systems on the Cray Y-MP and C90 are presented.
Energy Technology Data Exchange (ETDEWEB)
Guerin, P
2007-12-15
The neutronic simulation of a nuclear reactor core is performed using the neutron transport equation, and leads to an eigenvalue problem in the steady-state case. Among the deterministic resolution methods, diffusion approximation is often used. For this problem, the MINOS solver based on a mixed dual finite element method has shown his efficiency. In order to take advantage of parallel computers, and to reduce the computing time and the local memory requirement, we propose in this dissertation two domain decomposition methods for the resolution of the mixed dual form of the eigenvalue neutron diffusion problem. The first approach is a component mode synthesis method on overlapping sub-domains. Several Eigenmodes solutions of a local problem solved by MINOS on each sub-domain are taken as basis functions used for the resolution of the global problem on the whole domain. The second approach is a modified iterative Schwarz algorithm based on non-overlapping domain decomposition with Robin interface conditions. At each iteration, the problem is solved on each sub domain by MINOS with the interface conditions deduced from the solutions on the adjacent sub-domains at the previous iteration. The iterations allow the simultaneous convergence of the domain decomposition and the eigenvalue problem. We demonstrate the accuracy and the efficiency in parallel of these two methods with numerical results for the diffusion model on realistic 2- and 3-dimensional cores. (author)
Adaptive Hybrid Visual Servo Regulation of Mobile Robots Based on Fast Homography Decomposition
Directory of Open Access Journals (Sweden)
Chunfu Wu
2015-01-01
Full Text Available For the monocular camera-based mobile robot system, an adaptive hybrid visual servo regulation algorithm which is based on a fast homography decomposition method is proposed to drive the mobile robot to its desired position and orientation, even when object’s imaging depth and camera’s position extrinsic parameters are unknown. Firstly, the homography’s particular properties caused by mobile robot’s 2-DOF motion are taken into account to induce a fast homography decomposition method. Secondly, the homography matrix and the extracted orientation error, incorporated with the desired view’s single feature point, are utilized to form an error vector and its open-loop error function. Finally, Lyapunov-based techniques are exploited to construct an adaptive regulation control law, followed by the experimental verification. The experimental results show that the proposed fast homography decomposition method is not only simple and efficient, but also highly precise. Meanwhile, the designed control law can well enable mobile robot position and orientation regulation despite the lack of depth information and camera’s position extrinsic parameters.
Schaller, Matthieu; Chalk, Aidan B G; Draper, Peter W
2016-01-01
We present a new open-source cosmological code, called SWIFT, designed to solve the equations of hydrodynamics using a particle-based approach (Smooth Particle Hydrodynamics) on hybrid shared/distributed-memory architectures. SWIFT was designed from the bottom up to provide excellent strong scaling on both commodity clusters (Tier-2 systems) and Top100-supercomputers (Tier-0 systems), without relying on architecture-specific features or specialized accelerator hardware. This performance is due to three main computational approaches: (1) Task-based parallelism for shared-memory parallelism, which provides fine-grained load balancing and thus strong scaling on large numbers of cores. (2) Graph-based domain decomposition, which uses the task graph to decompose the simulation domain such that the work, as opposed to just the data, as is the case with most partitioning schemes, is equally distributed across all nodes. (3) Fully dynamic and asynchronous communication, in which communication is modelled as just anot...
Poggi, Valerio; Ermert, Laura; Burjanek, Jan; Michel, Clotaire; Fäh, Donat
2015-01-01
Frequency domain decomposition (FDD) is a well-established spectral technique used in civil engineering to analyse and monitor the modal response of buildings and structures. The method is based on singular value decomposition of the cross-power spectral density matrix from simultaneous array recordings of ambient vibrations. This method is advantageous to retrieve not only the resonance frequencies of the investigated structure, but also the corresponding modal shapes without the need for an absolute reference. This is an important piece of information, which can be used to validate the consistency of numerical models and analytical solutions. We apply this approach using advanced signal processing to evaluate the resonance characteristics of 2-D Alpine sedimentary valleys. In this study, we present the results obtained at Martigny, in the Rhône valley (Switzerland). For the analysis, we use 2 hr of ambient vibration recordings from a linear seismic array deployed perpendicularly to the valley axis. Only the horizontal-axial direction (SH) of the ground motion is considered. Using the FDD method, six separate resonant frequencies are retrieved together with their corresponding modal shapes. We compare the mode shapes with results from classical standard spectral ratios and numerical simulations of ambient vibration recordings.
On the convergence rate of a parallel nonoverlapping domain decomposition method
Institute of Scientific and Technical Information of China (English)
2008-01-01
In recent years,a nonoverlapping domain decomposition iterative procedure,which is based on using Robin-type boundary conditions as information transmission conditions on the subdomain interfaces,has been developed and analyzed.It is known that the convergence rate of this method is 1-O(h),where h is mesh size.In this paper,the convergence rate is improved to be 1-O(h1/2 H-1/2)sometime by choosing suitable parameter,where H is the subdomain size.Counter examples are constructed to show that our convergence estimates are sharp,which means that the convergence rate cannot be better than 1-O(h1/2H-1/2)in a certain case no matter how parameter is chosen.
Lubineau, Gilles
2015-03-01
We propose a domain decomposition formalism specifically designed for the identification of local elastic parameters based on full-field measurements. This technique is made possible by a multi-scale implementation of the constitutive compatibility method. Contrary to classical approaches, the constitutive compatibility method resolves first some eigenmodes of the stress field over the structure rather than directly trying to recover the material properties. A two steps micro/macro reconstruction of the stress field is performed: a Dirichlet identification problem is solved first over every subdomain, the macroscopic equilibrium is then ensured between the subdomains in a second step. We apply the method to large linear elastic 2D identification problems to efficiently produce estimates of the material properties at a much lower computational cost than classical approaches.
DOMAIN DECOMPOSITION FOR POROELASTICITY AND ELASTICITY WITH DG JUMPS AND MORTARS
GIRAULT, V.
2011-01-01
We couple a time-dependent poroelastic model in a region with an elastic model in adjacent regions. We discretize each model independently on non-matching grids and we realize a domain decomposition on the interface between the regions by introducing DG jumps and mortars. The unknowns are condensed on the interface, so that at each time step, the computation in each subdomain can be performed in parallel. In addition, by extrapolating the displacement, we present an algorithm where the computations of the pressure and displacement are decoupled. We show that the matrix of the interface problem is positive definite and establish error estimates for this scheme. © 2011 World Scientific Publishing Company.
A balancing domain decomposition method by constraints for advection-diffusion problems
Energy Technology Data Exchange (ETDEWEB)
Tu, Xuemin; Li, Jing
2008-12-10
The balancing domain decomposition methods by constraints are extended to solving nonsymmetric, positive definite linear systems resulting from the finite element discretization of advection-diffusion equations. A pre-conditioned GMRES iteration is used to solve a Schur complement system of equations for the subdomain interface variables. In the preconditioning step of each iteration, a partially sub-assembled finite element problem is solved. A convergence rate estimate for the GMRES iteration is established, under the condition that the diameters of subdomains are small enough. It is independent of the number of subdomains and grows only slowly with the subdomain problem size. Numerical experiments for several two-dimensional advection-diffusion problems illustrate the fast convergence of the proposed algorithm.
Rey, Valentine; Rey, Christian
2016-01-01
This article deals with the computation of guaranteed lower bounds of the error in the framework of finite element (FE) and domain decomposition (DD) methods. In addition to a fully parallel computation, the proposed lower bounds separate the algebraic error (due to the use of a DD iterative solver) from the discretization error (due to the FE), which enables the steering of the iterative solver by the discretization error. These lower bounds are also used to improve the goal-oriented error estimation in a substructured context. Assessments on 2D static linear mechanic problems illustrate the relevance of the separation of sources of error and the lower bounds' independence from the substructuring. We also steer the iterative solver by an objective of precision on a quantity of interest. This strategy consists in a sequence of solvings and takes advantage of adaptive remeshing and recycling of search directions.
Domain decomposition, multi-level integration and exponential noise reduction in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Ce, Marco [Scuola Normale Superiore, Pisa (Italy); INFN, Sezione di Pisa (Italy); Giusti, Leonardo [Univ. di Milano-Bicocca (Italy). Dipt. di Fisica; INFN, Sezione di Milano-Bicocca (Italy); Schaefer, Stefan [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2016-01-15
We explore the possibility of computing fermionic correlators on the lattice by combining a domain decomposition with a multi-level integration scheme. The quark propagator is expanded in series of terms with a well defined hierarchical structure. The higher the order of a term, the (exponentially) smaller its magnitude, the less local is its dependence on the gauge field. Once inserted in a Wick contraction, the gauge-field dependence of the terms in the resulting series can be factorized so that it is suitable for multi-level Monte Carlo integration. We test the strategy in quenched QCD by computing the disconnected correlator of two flavor-diagonal pseudoscalar densities, and a nucleon two-point function. In either cases we observe a significant exponential increase of the signal-to-noise ratio.
Zhao, Tao; Hwang, Feng-Nan; Cai, Xiao-Chuan
2016-07-01
We consider a quintic polynomial eigenvalue problem arising from the finite volume discretization of a quantum dot simulation problem. The problem is solved by the Jacobi-Davidson (JD) algorithm. Our focus is on how to achieve the quadratic convergence of JD in a way that is not only efficient but also scalable when the number of processor cores is large. For this purpose, we develop a projected two-level Schwarz preconditioned JD algorithm that exploits multilevel domain decomposition techniques. The pyramidal quantum dot calculation is carefully studied to illustrate the efficiency of the proposed method. Numerical experiments confirm that the proposed method has a good scalability for problems with hundreds of millions of unknowns on a parallel computer with more than 10,000 processor cores.
A stabilized explicit Lagrange multiplier based domain decomposition method for parabolic problems
Zheng, Zheming; Simeon, Bernd; Petzold, Linda
2008-05-01
A fully explicit, stabilized domain decomposition method for solving moderately stiff parabolic partial differential equations (PDEs) is presented. Writing the semi-discretized equations as a differential-algebraic equation (DAE) system where the interface continuity constraints between subdomains are enforced by Lagrange multipliers, the method uses the Runge-Kutta-Chebyshev projection scheme to integrate the DAE explicitly and to enforce the constraints by a projection. With mass lumping techniques and node-to-node matching grids, the method is fully explicit without solving any linear system. A stability analysis is presented to show the extended stability property of the method. The method is straightforward to implement and to parallelize. Numerical results demonstrate that it has excellent performance.
Kuraz, Michal
2016-06-01
Modelling the transport processes in a vadose zone, e.g. modelling contaminant transport or the effect of the soil water regime on changes in soil structure and composition, plays an important role in predicting the reactions of soil biotopes to anthropogenic activity. Water flow is governed by the quasilinear Richards equation. The paper concerns the implementation of a multi-time-step approach for solving a nonlinear Richards equation. When modelling porous media flow with a Richards equation, due to a possible convection dominance and a convergence of a nonlinear solver, a stable finite element approximation requires accurate temporal and spatial integration. The method presented here enables adaptive domain decomposition algorithm together with a multi-time-step treatment of actively changing subdomains.
Identification of the Swiss Z24 Highway Bridge by Frequency Domain Decomposition
DEFF Research Database (Denmark)
Brincker, Rune; Andersen, P.
2002-01-01
This paper presents the result of the modal identification of the Swiss highway bridge Z24. A series of 15 progressive damage tests were performed on the bridge before it was demolished in autumn 1998, and the ambient response of the bridge was recorded for each damage case. In this paper the modal...... properties are identified from the ambient responses by frequency domain decomposition. 6 modes were identified for all 15 damage cases. The identification was carried out for the full 3D data case i.e. including all measurements, a total of 291 channels, a reduced data case in 2D including 153 channels......, and finally, a 1D case including 20 channels. The modal properties for the different damage cases are compared with the modal properties of the undamaged bridge. Deviations for frequencies, damping ratios and MAC values are used as monitoring variables. From these results it can be concluded, that frequencies...
Final Report, DE-FG01-06ER25718 Domain Decomposition and Parallel Computing
Energy Technology Data Exchange (ETDEWEB)
Widlund, Olof B. [New York Univ. (NYU), NY (United States). Courant Inst.
2015-06-09
The goal of this project is to develop and improve domain decomposition algorithms for a variety of partial differential equations such as those of linear elasticity and electro-magnetics.These iterative methods are designed for massively parallel computing systems and allow the fast solution of the very large systems of algebraic equations that arise in large scale and complicated simulations. A special emphasis is placed on problems arising from Maxwell's equation. The approximate solvers, the preconditioners, are combined with the conjugate gradient method and must always include a solver of a coarse model in order to have a performance which is independent of the number of processors used in the computer simulation. A recent development allows for an adaptive construction of this coarse component of the preconditioner.
Duality-based domain decomposition with natural coarse-space for variational inequalities
Dostál, Zdenek; Neto, Francisco A. M. Gomes; Santos, Sandra A.
2000-12-01
An efficient non-overlapping domain decomposition algorithm of Neumann-Neumann type for solving variational inequalities arising from the elliptic boundary value problems with inequality boundary conditions has been presented. The discretized problem is first turned by the duality theory of convex programming into a quadratic programming problem with bound and equality constraints and the latter is further modified by means of orthogonal projectors to the natural coarse space introduced recently by Farhat and Roux. The resulting problem is then solved by an augmented Lagrangian type algorithm with an outer loop for the Lagrange multipliers for the equality constraints and an inner loop for the solution of the bound constrained quadratic programming problems. The projectors are shown to guarantee an optimal rate of convergence of iterative solution of auxiliary linear problems. Reported theoretical results and numerical experiments indicate high numerical and parallel scalability of the algorithm.
On the convergence rate of a parallel nonoverlapping domain decomposition method
Institute of Scientific and Technical Information of China (English)
QIN LiZhen; SHI ZhongCi; XU XueJun
2008-01-01
In recent years, a nonoverlapping domain decomposition iterative procedure, which is based on using Robin-type boundary conditions as information transmission conditions on the subdomain interfaces, has been developed and analyzed. It is known that the convergence rate of this method is 1 - O(h), where h is mesh size. In this paper, the convergence rate is improved to be 1 - O(h1/2H-1/2) sometime by choosing suitable parameter, where H is the subdomain size. Counter examples are constructed to show that our convergence estimates are sharp, which means that the convergence rate cannot be better than 1 - O(h1/2H-1/2) in a certain case no matter how parameter is chosen.
Kuo, Kenneth K.; Lu, Y. C.; Chiaverini, Martin J.; Harting, George C.
1994-11-01
An experimental study on the fundamental processes involved in fuel decomposition and boundary layer combustion in hybrid rocket motors is being conducted at the High Pressure Combustion Laboratory of the Pennsylvania State University. This research should provide a useful engineering technology base in the development of hybrid rocket motors as well as a fundamental understanding of the complex processes involved in hybrid propulsion. A high pressure slab motor has been designed and manufactured for conducting experimental investigations. Oxidizer (LOX or GOX) supply and control systems have been designed and partly constructed for the head-end injection into the test chamber. Experiments using HTPB fuel, as well as fuels supplied by NASA designated industrial companies will be conducted. Design and construction of fuel casting molds and sample holders have been completed. The portion of these items for industrial company fuel casting will be sent to the McDonnell Douglas Aerospace Corporation in the near future. The study focuses on the following areas: observation of solid fuel burning processes with LOX or GOX, measurement and correlation of solid fuel regression rate with operating conditions, measurement of flame temperature and radical species concentrations, determination of the solid fuel subsurface temperature profile, and utilization of experimental data for validation of a companion theoretical study (Part 2) also being conducted at PSU.
Kuo, Kenneth K.; Lu, Y. C.; Chiaverini, Martin J.; Harting, George C.
1994-01-01
An experimental study on the fundamental processes involved in fuel decomposition and boundary layer combustion in hybrid rocket motors is being conducted at the High Pressure Combustion Laboratory of the Pennsylvania State University. This research should provide a useful engineering technology base in the development of hybrid rocket motors as well as a fundamental understanding of the complex processes involved in hybrid propulsion. A high pressure slab motor has been designed and manufactured for conducting experimental investigations. Oxidizer (LOX or GOX) supply and control systems have been designed and partly constructed for the head-end injection into the test chamber. Experiments using HTPB fuel, as well as fuels supplied by NASA designated industrial companies will be conducted. Design and construction of fuel casting molds and sample holders have been completed. The portion of these items for industrial company fuel casting will be sent to the McDonnell Douglas Aerospace Corporation in the near future. The study focuses on the following areas: observation of solid fuel burning processes with LOX or GOX, measurement and correlation of solid fuel regression rate with operating conditions, measurement of flame temperature and radical species concentrations, determination of the solid fuel subsurface temperature profile, and utilization of experimental data for validation of a companion theoretical study (Part 2) also being conducted at PSU.
Minei, A. J.; Cooke, S. A.
2013-06-01
A singular value decomposition (SVD) signal processing method is newly applied to molecular free induction decays (FIDs) obtained using a time domain, broadband rotational spectrometer. It is demonstrated that for the strongest spectral transitions the SVD method can determine transition frequencies with a precision matching that of the fast Fourier transform method. Furthermore, the SVD-based analysis produces information concerning transition phase, amplitude, damping, and frequency for the strongest molecular signals. These parameters are shown as useful in regards to time-domain signal filtering. The computational expense of the SVD method is high and therefore this approach has the disadvantage that with our present computers the full molecular FID must be considerably truncated. The effects of FID truncation on the determined transition frequencies have been examined. Conversely, this truncation method illustrates that broadband spectra may be recovered from fragments as small as 1 % of the complete FID. The success of the SVD-based method is further examined in regards to weak signal detection, and frequency dependent detection. The pure rotational spectrum of 1H,1H,2H-perfluorocyclobutane is used for illustrative purposes in this study.
Lahmiri, Salim
2016-03-01
Hybridisation of the bi-dimensional empirical mode decomposition (BEMD) with denoising techniques has been proposed in the literature as an effective approach for image denoising. In this Letter, the Student's probability density function is introduced in the computation of the mean envelope of the data during the BEMD sifting process to make it robust to values that are far from the mean. The resulting BEMD is denoted tBEMD. In order to show the effectiveness of the tBEMD, several image denoising techniques in tBEMD domain are employed; namely, fourth order partial differential equation (PDE), linear complex diffusion process (LCDP), non-linear complex diffusion process (NLCDP), and the discrete wavelet transform (DWT). Two biomedical images and a standard digital image were considered for experiments. The original images were corrupted with additive Gaussian noise with three different levels. Based on peak-signal-to-noise ratio, the experimental results show that PDE, LCDP, NLCDP, and DWT all perform better in the tBEMD than in the classical BEMD domain. It is also found that tBEMD is faster than classical BEMD when the noise level is low. When it is high, the computational cost in terms of processing time is similar. The effectiveness of the presented approach makes it promising for clinical applications.
A tightly-coupled domain-decomposition approach for highly nonlinear stochastic multiphysics systems
Taverniers, Søren; Tartakovsky, Daniel M.
2017-02-01
Multiphysics simulations often involve nonlinear components that are driven by internally generated or externally imposed random fluctuations. When used with a domain-decomposition (DD) algorithm, such components have to be coupled in a way that both accurately propagates the noise between the subdomains and lends itself to a stable and cost-effective temporal integration. We develop a conservative DD approach in which tight coupling is obtained by using a Jacobian-free Newton-Krylov (JfNK) method with a generalized minimum residual iterative linear solver. This strategy is tested on a coupled nonlinear diffusion system forced by a truncated Gaussian noise at the boundary. Enforcement of path-wise continuity of the state variable and its flux, as opposed to continuity in the mean, at interfaces between subdomains enables the DD algorithm to correctly propagate boundary fluctuations throughout the computational domain. Reliance on a single Newton iteration (explicit coupling), rather than on the fully converged JfNK (implicit) coupling, may increase the solution error by an order of magnitude. Increase in communication frequency between the DD components reduces the explicit coupling's error, but makes it less efficient than the implicit coupling at comparable error levels for all noise strengths considered. Finally, the DD algorithm with the implicit JfNK coupling resolves temporally-correlated fluctuations of the boundary noise when the correlation time of the latter exceeds some multiple of an appropriately defined characteristic diffusion time.
Institute of Scientific and Technical Information of China (English)
Luo Chang
2006-01-01
In this work, system of parabolic equations with discontinuous coefficients is studied. The domain decomposition method modified by a characteristic finite element procedure is applied. A function is defined to approximate the fluxes on inner boundaries by using the solution at the previous level. Thus the parallelism is achieved. Convergence analysis and error estimate are also presented.
Energy Technology Data Exchange (ETDEWEB)
Liang, Jingang; Wang, Kan; Qiu, Yishu [Dept. of Engineering Physics, LiuQing Building, Tsinghua University, Beijing (China); Chai, Xiao Ming; Qiang, Sheng Long [Science and Technology on Reactor System Design Technology Laboratory, Nuclear Power Institute of China, Chengdu (China)
2016-06-15
Because of prohibitive data storage requirements in large-scale simulations, the memory problem is an obstacle for Monte Carlo (MC) codes in accomplishing pin-wise three-dimensional (3D) full-core calculations, particularly for whole-core depletion analyses. Various kinds of data are evaluated and quantificational total memory requirements are analyzed based on the Reactor Monte Carlo (RMC) code, showing that tally data, material data, and isotope densities in depletion are three major parts of memory storage. The domain decomposition method is investigated as a means of saving memory, by dividing spatial geometry into domains that are simulated separately by parallel processors. For the validity of particle tracking during transport simulations, particles need to be communicated between domains. In consideration of efficiency, an asynchronous particle communication algorithm is designed and implemented. Furthermore, we couple the domain decomposition method with MC burnup process, under a strategy of utilizing consistent domain partition in both transport and depletion modules. A numerical test of 3D full-core burnup calculations is carried out, indicating that the RMC code, with the domain decomposition method, is capable of pin-wise full-core burnup calculations with millions of depletion regions.
Bearing fault detection based on hybrid ensemble detector and empirical mode decomposition
Georgoulas, George; Loutas, Theodore; Stylios, Chrysostomos D.; Kostopoulos, Vassilis
2013-12-01
Aiming at more efficient fault diagnosis, this research work presents an integrated anomaly detection approach for seeded bearing faults. Vibration signals from normal bearings and bearings with three different fault locations, as well as different fault sizes and loading conditions are examined. The Empirical Mode Decomposition and the Hilbert Huang transform are employed for the extraction of a compact feature set. Then, a hybrid ensemble detector is trained using data coming only from the normal bearings and it is successfully applied for the detection of any deviation from the normal condition. The results prove the potential use of the proposed scheme as a first stage of an alarm signalling system for the detection of bearing faults irrespective of their loading condition.
Directory of Open Access Journals (Sweden)
Heon Lee
2012-01-01
Full Text Available Experimental results of photocatalysis under high dissolved oxygen (DO concentration conditions are reported. Methylene blue was used as the organic pollutant to be degraded by a novel microwave/UV/DO/TiO2 photocatalyst hybrid system. The degradation rate increased with TiO2 nanoparticle dosages and DO concentration. However, inhibition of photocatalysis due to bubbles produced by DO generator was also observed. When the DO generator was used to increase the DO concentration in the pollutant solution treated by the microwave-assisted UV-TiO2 photocatalysis, the decomposition rate constant was highest among all the experimental conditions tested in this study. This result demonstrated that high concentration of DO can enhance the photocatalytic reaction rate by causing a synergistic effect of constituent techniques.
Stability of simultaneously triangularizable switched systems on hybrid domains
Directory of Open Access Journals (Sweden)
Geoffrey Eisenbarth
2014-03-01
Full Text Available In this paper, we extend the results of [8, 15, 22], which provide sufficient conditions for the global exponential stability of switched systems under arbitrary switching via the existence of a common quadratic Lyapunov function. In particular, we extend the Lie algebraic results in [15] to switched systems with hybrid non-uniform discrete and continuous domains, a direct unifying generalization of switched systems on R and Z, and extend the results in [8, 22] to a larger class of switched systems, namely those whose subsystem matrices are simultaneously triangularizable. In addition, we explore an easily checkable characterization of our required hypotheses for the theorems. Finally, conditions are provided under which there exists a stabilizing switching pattern for a collection of (not necessarily stable linear systems that are simultaneously triangularizable and separate criteria are formed which imply the stability of the system under a given switching pattern given a priori.
HYBRID SULFUR FLOWSHEETS USING PEM ELECTROLYSIS AND A BAYONET DECOMPOSITION REACTOR
Energy Technology Data Exchange (ETDEWEB)
Gorensek, M; William Summers, W
2008-05-30
A conceptual design is presented for a Hybrid Sulfur process for the production of hydrogen using a high-temperature nuclear heat source to split water. The process combines proton exchange membrane-based SO{sub 2}-depolarized electrolyzer technology being developed at Savannah River National Laboratory with silicon carbide bayonet decomposition reactor technology being developed at Sandia National Laboratories. Both are part of the US DOE Nuclear Hydrogen Initiative. The flowsheet otherwise uses only proven chemical process components. Electrolyzer product is concentrated from 50 wt% sulfuric acid to 75 wt% via recuperative vacuum distillation. Pinch analysis is used to predict the high-temperature heat requirement for sulfuric acid decomposition. An Aspen Plus{trademark} model of the flowsheet indicates 340.3 kJ high-temperature heat, 75.5 kJ low-temperature heat, 1.31 kJ low-pressure steam, and 120.9 kJ electric power are consumed per mole of H{sub 2} product, giving an LHV efficiency of 35.3% (41.7% HHV efficiency) if electric power is available at a conversion efficiency of 45%.
Schultz, A.
2010-12-01
describe our ongoing efforts to achieve massive parallelization on a novel hybrid GPU testbed machine currently configured with 12 Intel Westmere Xeon CPU cores (or 24 parallel computational threads) with 96 GB DDR3 system memory, 4 GPU subsystems which in aggregate contain 960 NVidia Tesla GPU cores with 16 GB dedicated DDR3 GPU memory, and a second interleved bank of 4 GPU subsystems containing in aggregate 1792 NVidia Fermi GPU cores with 12 GB dedicated DDR5 GPU memory. We are applying domain decomposition methods to a modified version of Weiss' (2001) 3D frequency domain full physics EM finite difference code, an open source GPL licensed f90 code available for download from www.OpenEM.org. This will be the core of a new hybrid 3D inversion that parallelizes frequencies across CPUs and individual forward solutions across GPUs. We describe progress made in modifying the code to use direct solvers in GPU cores dedicated to each small subdomain, iteratively improving the solution by matching adjacent subdomain boundary solutions, rather than iterative Krylov space sparse solvers as currently applied to the whole domain.
Energy Technology Data Exchange (ETDEWEB)
Saas, L.
2004-05-01
This Thesis deals with sedimentary basin modeling whose goal is the prediction through geological times of the localizations and appraisal of hydrocarbons quantities present in the ground. Due to the natural and evolutionary decomposition of the sedimentary basin in blocks and stratigraphic layers, domain decomposition methods are requested to simulate flows of waters and of hydrocarbons in the ground. Conservations laws are used to model the flows in the ground and form coupled partial differential equations which must be discretized by finite volume method. In this report we carry out a study on finite volume methods on non-matching grids solved by domain decomposition methods. We describe a family of finite volume schemes on non-matching grids and we prove that the associated global discretized problem is well posed. Then we give an error estimate. We give two examples of finite volume schemes on non matching grids and the corresponding theoretical results (Constant scheme and Linear scheme). Then we present the resolution of the global discretized problem by a domain decomposition method using arbitrary interface conditions (for example Robin conditions). Finally we give numerical results which validate the theoretical results and study the use of finite volume methods on non-matching grids for basin modeling. (author)
Enhancement of Hyperspectral Real World Images Using Hybrid Domain Approach
Directory of Open Access Journals (Sweden)
Shyam Lal
2013-04-01
Full Text Available This paper presents enhancement of hyperspectral real world images using hybrid domain approach. The proposed method consists of three phases: In first phase the discrete wavelet transform is applied and approximation coefficient is selected. In second phase approximation coefficient of discrete wavelet transform of image is process by automatic contrast adjustment technique and in third phase it takes logarithmic of output of second phase and after that adaptive filtering is applied for image enhancement in frequency domain. To judge the superiority of proposed method the image quality parameters such as measure of enhancement (EME and measure of enhancement factor (EMF is evaluated. Therefore, a better value of EME and EMF implies that the visual quality of the enhanced image is good. Simulation results indicates that proposed method provides better results as compared to other state-of-art contrast enhancement algorithms for hyperspectral real world images. The proposed method is efficient and very effective method for contrast enhancement of hyperspectral real world images. This method can also be used in different applications where images are suffering from different contrast problems.
Men, Kuo; Quan, Hong; Yang, Peipei; Cao, Ting; Li, Weihao
2010-04-01
The frequency-domain magnetic resonance spectroscopy (MRS) is achieved by the Fast Fourier Transform (FFT) of the time-domain signals. Usually we are only interested in the portion lying in a frequency band of the whole spectrum. A method based on the singular value decomposition (SVD) and frequency-selection is presented in this article. The method quantifies the spectrum lying in the interested frequency band and reduces the interference of the parts lying out of the band in a computationally efficient way. Comparative experiments with the standard time-domain SVD method indicate that the method introduced in this article is accurate and timesaving in practical situations.
Pioldi, Fabio; Rizzi, Egidio
2017-07-01
Output-only structural identification is developed by a refined Frequency Domain Decomposition ( rFDD) approach, towards assessing current modal properties of heavy-damped buildings (in terms of identification challenge), under strong ground motions. Structural responses from earthquake excitations are taken as input signals for the identification algorithm. A new dedicated computational procedure, based on coupled Chebyshev Type II bandpass filters, is outlined for the effective estimation of natural frequencies, mode shapes and modal damping ratios. The identification technique is also coupled with a Gabor Wavelet Transform, resulting in an effective and self-contained time-frequency analysis framework. Simulated response signals generated by shear-type frames (with variable structural features) are used as a necessary validation condition. In this context use is made of a complete set of seismic records taken from the FEMA P695 database, i.e. all 44 "Far-Field" (22 NS, 22 WE) earthquake signals. The modal estimates are statistically compared to their target values, proving the accuracy of the developed algorithm in providing prompt and accurate estimates of all current strong ground motion modal parameters. At this stage, such analysis tool may be employed for convenient application in the realm of Earthquake Engineering, towards potential Structural Health Monitoring and damage detection purposes.
Directory of Open Access Journals (Sweden)
Carlo Ruzzo
2016-10-01
Full Text Available System identification of offshore floating platforms is usually performed by testing small-scale models in wave tanks, where controlled conditions, such as still water for free decay tests, regular and irregular wave loading can be represented. However, this approach may result in constraints on model dimensions, testing time, and costs of the experimental activity. For such reasons, intermediate-scale field modelling of offshore floating structures may become an interesting as well as cost-effective alternative in a near future. Clearly, since the open sea is not a controlled environment, traditional system identification may become challenging and less precise. In this paper, a new approach based on Frequency Domain Decomposition (FDD method for Operational Modal Analysis is proposed and validated against numerical simulations in ANSYS AQWA v.16.0 on a simple spar-type structure. The results obtained match well with numerical predictions, showing that this new approach, opportunely coupled with more traditional wave tanks techniques, proves to be very promising to perform field-site identification of the model structures.
Wang, Benfeng; Jakobsen, Morten; Wu, Ru-Shan; Lu, Wenkai; Chen, Xiaohong
2017-03-01
Full waveform inversion (FWI) has been regarded as an effective tool to build the velocity model for the following pre-stack depth migration. Traditional inversion methods are built on Born approximation and are initial model dependent, while this problem can be avoided by introducing Transmission matrix (T-matrix), because the T-matrix includes all orders of scattering effects. The T-matrix can be estimated from the spatial aperture and frequency bandwidth limited seismic data using linear optimization methods. However the full T-matrix inversion method (FTIM) is always required in order to estimate velocity perturbations, which is very time consuming. The efficiency can be improved using the previously proposed inverse thin-slab propagator (ITSP) method, especially for large scale models. However, the ITSP method is currently designed for smooth media, therefore the estimation results are unsatisfactory when the velocity perturbation is relatively large. In this paper, we propose a domain decomposition method (DDM) to improve the efficiency of the velocity estimation for models with large perturbations, as well as guarantee the estimation accuracy. Numerical examples for smooth Gaussian ball models and a reservoir model with sharp boundaries are performed using the ITSP method, the proposed DDM and the FTIM. The estimated velocity distributions, the relative errors and the elapsed time all demonstrate the validity of the proposed DDM.
Some nonlinear space decomposition algorithms
Energy Technology Data Exchange (ETDEWEB)
Tai, Xue-Cheng; Espedal, M. [Univ. of Bergen (Norway)
1996-12-31
Convergence of a space decomposition method is proved for a general convex programming problem. The space decomposition refers to methods that decompose a space into sums of subspaces, which could be a domain decomposition or a multigrid method for partial differential equations. Two algorithms are proposed. Both can be used for linear as well as nonlinear elliptic problems and they reduce to the standard additive and multiplicative Schwarz methods for linear elliptic problems. Two {open_quotes}hybrid{close_quotes} algorithms are also presented. They converge faster than the additive one and have better parallelism than the multiplicative method. Numerical tests with a two level domain decomposition for linear, nonlinear and interface elliptic problems are presented for the proposed algorithms.
Directory of Open Access Journals (Sweden)
Jafar Biazar
2015-01-01
Full Text Available We combine the Adomian decomposition method (ADM and Adomian’s asymptotic decomposition method (AADM for solving Riccati equations. We investigate the approximate global solution by matching the near-field approximation derived from the Adomian decomposition method with the far-field approximation derived from Adomian’s asymptotic decomposition method for Riccati equations and in such cases when we do not find any region of overlap between the obtained approximate solutions by the two proposed methods, we connect the two approximations by the Padé approximant of the near-field approximation. We illustrate the efficiency of the technique for several specific examples of the Riccati equation for which the exact solution is known in advance.
Modal Identification of Output-only Systems Using Frequency Domain Decomposition
DEFF Research Database (Denmark)
Brincker, Rune; Zhang, L.M.; Andersen, Palle
2001-01-01
approach where the modal parameters are estimated by simple peak picking. However, by introducing a decomposition of the spectral density function matrix, the response spectra can be separated into a set of single degree of freedom systems, each corresponding to an individual mode. By using...... this decomposition technique close modes can be identified with high accuracy even in the case of strong noise contamination of the signals. Also, the technique clearly indicates harmonic components in the response signals....
Energy Technology Data Exchange (ETDEWEB)
El-Sayed, A.M.A. [Faculty of Science University of Alexandria (Egypt)]. E-mail: amasyed@hotmail.com; Gaber, M. [Faculty of Education Al-Arish, Suez Canal University (Egypt)]. E-mail: mghf408@hotmail.com
2006-11-20
The Adomian decomposition method has been successively used to find the explicit and numerical solutions of the time fractional partial differential equations. A different examples of special interest with fractional time and space derivatives of order {alpha}, 0<{alpha}=<1 are considered and solved by means of Adomian decomposition method. The behaviour of Adomian solutions and the effects of different values of {alpha} are shown graphically for some examples.
Singular value decomposition as a denoising tool for airborne time domain electromagnetic data
Reninger, P.-A.; Martelet, G.; Deparis, J.; Perrin, J.; Chen, Y.
2011-10-01
Airborne time domain electromagnetic (TDEM) surveys are increasingly carried out in anthropized areas as part of environmental studies. In such areas, noise arises mainly from either natural sources, such as spherics, or cultural sources, such as couplings with man-made installations. This results in various distortions on the measured decays, which make the EM noise spectrum complex and may lead to erroneous inversion and subsequent misinterpretations. Thresholding and stacking standard techniques, commonly used to filter TDEM data, are less efficient in such environment, requiring a time-consuming and subjective manual editing. The aim of this study was therefore to propose an alternative fast and efficient user-assisted filtering approach. This was achieved using the singular value decomposition (SVD). The SVD method uses the principal component analysis to extract into components the dominant shapes from a series of raw input curves. EM decays can then be reconstructed with particular components only. To do so, we had to adapt and implement the SVD, firstly, to separate clearly and so identify easily the components containing the geological signal, and then to denoise properly TDEM data. The reconstructed decays were used to detect noisy gates on their corresponding measured decays. This denoising step allowed rejecting efficiently mainly spikes and oscillations. Then, we focused on couplings with man-made installations, which may result in artifacts on the inverted models. An analysis of the map of weights of the selected "noisy components" highlighted high correlations with man-made installations localized by the flight video. We had therefore a tool to cull most likely decays biased by capacitive coupling noises. Finally, rejection of decays affected by galvanic coupling noises was also possible locating them through the analysis of specific SVD components. This SVD procedure was applied on airborne TDEM data surveyed by SkyTEM Aps. over an anthropized area
HR approximation of FIR filters via discrete-time hybrid-domain vector fitting
2009-01-01
We present a discrete-time hybrid-domain vector fitting algorithm, called HD-VFz, for the HR approximation of FIR filters with an arbitrary combination of time- and frequency-sampled responses. The core routine involves a two-step pole refinement process based on a linear least-squares solve and an eigenvalue problem. Through hybrid-domain data approximation and digital partial fraction basis with relative stability consideration, HD-VFz exhibits fast computation and remarkable fitting accura...
Institute of Scientific and Technical Information of China (English)
Yi-Ci Cai; Jin Shi; Zu-Ying Luo; Xian-Long Hong
2005-01-01
This paper proposes a novel algorithm, which can be used to model and analyze mesh tree hybrid power/ground distribution networks with multiple voltage supply in time domain. Not only this algorithm enhances common method's ability on analysis of power/ground network with irregular topology, but also very high accuracy it keeps. The accuracy and stability of this algorithm is proved using strict math method in this paper. Also, the usage of both precondition technique based on Incomplete Choleskey Decomposition and fast variable elimination technique has improved the algorithm's efficiency a lot. Experimental results show that it can finish the analysis of power/ground network with enormous size within very short time. Also, this algorithm can be applied to analyze the clock network, bus network, and signal network without buffer under high working frequency because of the independence of the topology.
A hybrid method for identification of structural domains
Hua, Yongpan; Zhu, Min; Wang, Yuelong; Xie, Zhaoyang; Li, Menglong
2014-12-01
Structural domains in proteins are the basic units to form various proteins. In the protein's evolution and functioning, domains play important roles. But the definition of domain is not yet precisely given, and the update cycle of structural domain databases is long. The automatic algorithms identify domains slowly, while protein entities with great structural complexity are on the rise. Here, we present a method which recognizes the compact and modular segments of polypeptide chains to identify structural domains, and contrast some data sets to illuminate their effect. The method combines support vector machine (SVM) with K-means algorithm. It is faster and more stable than most current algorithms and performs better. It also indicates that when proteins are presented as some Alpha-carbon atoms in 3D space, it is feasible to identify structural domains by the spatially structural properties. We have developed a web-server, which would be helpful in identification of structural domains (http://vis.sculab.org/~huayongpan/cgi-bin/domainAssignment.cgi).
Energy Technology Data Exchange (ETDEWEB)
Kang, Seung Hee; Kim, Sung Jun; Shin, Eui Sup [Chonbuk National University, Jeonju (Korea, Republic of)
2012-03-15
A smart interfacing method based on domain/boundary decomposition is presented for the non-linear analysis of thermo-elastoviscoplastic damage and contact. The smart interfacing method provides adaptive reinterfacing of the subdomains and the interface as a result of changes in the viscoplasticity and damage level. Since the whole domain is divided into subdomains, interface, and contact interfaces, non-linear analyses of the problems can be localized within a few subdomains and on the contact interfaces. For the continuity constraints on the interface and the contact interfaces, a penalty method is applied to the variational formulations and finite element approximations. By applying suitable solution algorithms and adopting the smart interfacing method, the computational efficiency can be considerably improved. The important features of the proposed method were also evaluated through numerical experiments.
Bono, Valentina; Das, Saptarshi; Maharatna, Koushik
2014-01-01
In order to reduce the muscle artifacts in multi-channel pervasive Electroencephalogram (EEG) signals, we here propose and compare two hybrid algorithms by combining the concept of wavelet packet transform (WPT), empirical mode decomposition (EMD) and Independent Component Analysis (ICA). The signal cleaning performances of WPT-EMD and WPT-ICA algorithms have been compared using a signal-to-noise ratio (SNR)-like criterion for artifacts. The algorithms have been tested on multiple trials of four different artifact cases viz. eye-blinking and muscle artifacts including left and right hand movement and head-shaking.
Directory of Open Access Journals (Sweden)
Khaled Loukhaoukha
2013-01-01
Full Text Available We present a new optimal watermarking scheme based on discrete wavelet transform (DWT and singular value decomposition (SVD using multiobjective ant colony optimization (MOACO. A binary watermark is decomposed using a singular value decomposition. Then, the singular values are embedded in a detailed subband of host image. The trade-off between watermark transparency and robustness is controlled by multiple scaling factors (MSFs instead of a single scaling factor (SSF. Determining the optimal values of the multiple scaling factors (MSFs is a difficult problem. However, a multiobjective ant colony optimization is used to determine these values. Experimental results show much improved performances of the proposed scheme in terms of transparency and robustness compared to other watermarking schemes. Furthermore, it does not suffer from the problem of high probability of false positive detection of the watermarks.
Robust Domain Decomposition Preconditioners for Abstract Symmetric Positive Definite Bilinear Forms
Efendiev, Y; Lazarov, R; Willems, J
2011-01-01
An abstract framework for constructing stable decompositions of the spaces corresponding to general symmetric positive definite problems into "local" subspaces and a global "coarse" space is developed. Particular applications of this abstract framework include practically important problems in porous media applications such as: the scalar elliptic (pressure) equation and the stream function formulation of its mixed form, Stokes' and Brinkman's equations. The constant in the corresponding abstract energy estimate is shown to be robust with respect to mesh parameters as well as the contrast, which is defined as the ratio of high and low values of the conductivity (or permeability). The derived stable decomposition allows to construct additive overlapping Schwarz iterative methods with condition numbers uniformly bounded with respect to the contrast and mesh parameters. The coarse spaces are obtained by patching together the eigenfunctions corresponding to the smallest eigenvalues of certain local problems. A de...
Robust domain decomposition preconditioners for abstract symmetric positive definite bilinear forms
Efendiev, Yalchin
2012-02-22
An abstract framework for constructing stable decompositions of the spaces corresponding to general symmetric positive definite problems into "local" subspaces and a global "coarse" space is developed. Particular applications of this abstract framework include practically important problems in porous media applications such as: the scalar elliptic (pressure) equation and the stream function formulation of its mixed form, Stokes\\' and Brinkman\\'s equations. The constant in the corresponding abstract energy estimate is shown to be robust with respect to mesh parameters as well as the contrast, which is defined as the ratio of high and low values of the conductivity (or permeability). The derived stable decomposition allows to construct additive overlapping Schwarz iterative methods with condition numbers uniformly bounded with respect to the contrast and mesh parameters. The coarse spaces are obtained by patching together the eigenfunctions corresponding to the smallest eigenvalues of certain local problems. A detailed analysis of the abstract setting is provided. The proposed decomposition builds on a method of Galvis and Efendiev [Multiscale Model. Simul. 8 (2010) 1461-1483] developed for second order scalar elliptic problems with high contrast. Applications to the finite element discretizations of the second order elliptic problem in Galerkin and mixed formulation, the Stokes equations, and Brinkman\\'s problem are presented. A number of numerical experiments for these problems in two spatial dimensions are provided. © EDP Sciences, SMAI, 2012.
Hybrid time/frequency domain modeling of nonlinear components
DEFF Research Database (Denmark)
Wiechowski, Wojciech Tomasz; Lykkegaard, Jan; Bak, Claus Leth
2007-01-01
model is used as a basis for its implementation. First, the linear network part is replaced with an ideal voltage source and a time domain (EMT) simulation is performed. During the initial oscillations, harmonic content of the converter currents is calculated at every period by a fast Fourier transform...... and the periodic steady state is identified. Obtained harmonic currents are assigned to current sources and used in the frequency domain calculation in the linear network. The obtained three-phase bus voltage is then inverse Fourier transformed and assigned to the voltage source and the time domain simulation...... is performed again. This process is repeated until the change in the magnitudes and phase angles of the fundamental and low order characteristic harmonics of the bus voltage is smaller then predefined precision indexes. The method is verified against precise time domain simulation. The convergence properties...
Li, Ping
2014-05-01
A scheme hybridizing discontinuous Galerkin time-domain (DGTD) and time-domain boundary integral (TDBI) methods for accurately analyzing transient electromagnetic scattering is proposed. Radiation condition is enforced using the numerical flux on the truncation boundary. The fields required by the flux are computed using the TDBI from equivalent currents introduced on a Huygens\\' surface enclosing the scatterer. The hybrid DGTDBI ensures that the radiation condition is mathematically exact and the resulting computation domain is as small as possible since the truncation boundary conforms to scatterer\\'s shape and is located very close to its surface. Locally truncated domains can also be defined around each disconnected scatterer additionally reducing the size of the overall computation domain. Numerical examples demonstrating the accuracy and versatility of the proposed method are presented. © 2014 IEEE.
Micromagnetic simulation of thickness variation of Neel cap in hybrid Bloch-Neel domain wall
Energy Technology Data Exchange (ETDEWEB)
Lu Mai [Key Lab. of Opto-Electronic Technology and Intelligent Control, Lanzhou Jiaotong University, Ministry of Education, P.O. Box 73, 118 West Anning Road, Lanzhou 730070, Gansu (China) and Department of Signals and Systems, Chalmers University of Technology, SE-412 96, Gothenburg (Sweden)]. E-mail: m.lu@mail.edu.cn; Leonard, Paul J. [Department of Electronic and Electrical Engineering, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom)
2005-08-01
The hybrid Bloch-Neel domain wall in iron film has been investigated using three-dimensional micromagnetic calculations. Magnetization distributions in the film plane and cross-section are presented. In the film plane the rotation of magnetization in the 180 deg domain wall takes two different patterns from the bottom layer to the top layer. In cross-section the C-shaped magnetization distribution with hybrid Bloch-Neel domain wall has been found. The thickness of the top Neel cap changes from its largest value as the C-shaped magnetization distribution appears, and becomes thinner as the C-shaped magnetization distribution gradually moves and grows up. The thickness variation of the bottom Neel cap changes in a similar way, but with a reversal pattern. The results in this paper will enrich our knowledge of magnetic domain and domain wall patterns in magnetic materials.
An efficient domain decomposition strategy for wave loads on surface piercing circular cylinders
DEFF Research Database (Denmark)
Paulsen, Bo Terp; Bredmose, Henrik; Bingham, Harry B.
2014-01-01
A fully nonlinear domain decomposed solver is proposed for efficient computations of wave loads on surface piercing structures in the time domain. A fully nonlinear potential flow solver was combined with a fully nonlinear Navier–Stokes/VOF solver via generalized coupling zones of arbitrary shape...
DEFF Research Database (Denmark)
Madsen, Kristoffer Hougaard; Hansen, Lars Kai; Mørup, Morten
2009-01-01
We propose the Time Frequency Gradient Method (TFGM) which forms a framework for optimization of models that are constrained in the time domain while having efficient representations in the frequency domain. Since the constraints in the time domain in general are not transparent in a frequency...... representation we demonstrate how the class of objective functions that are separable in either time or frequency instances allow the gradient in the time or frequency domain to be converted to the opposing domain. We further demonstrate the usefulness of this framework for three different models; Shifted Non......-negative Matrix Factorization, Convolutive Sparse Coding as well as Smooth and Sparse Matrix Factorization. Matlab implementation of the proposed algorithms are available for download at www.erpwavelab.org....
Complex roles of hybrid lipids in the composition, order, and size of lipid membrane domains.
Hassan-Zadeh, Ebrahim; Baykal-Caglar, Eda; Alwarawrah, Mohammad; Huang, Juyang
2014-02-11
Hybrid lipids (HL) are phospholipids with one saturated chain and one unsaturated chain. HL are hypothesized to act as linactants (i.e., 2D surfactants) in cell membranes, reducing line tension and creating nanoscopic lipid domains. Here we compare three hybrid lipids of different chain unsaturation (16:0-18:1PC (POPC), 16:0-18:2PC (PLPC), and 16:0-20:4PC (PAPC)) in their abilities to alter the composition, line tension, order, and compactness of lipid domains. We found that the liquid-ordered (Lo) and liquid-disordered (Ld) lipid domains in PAPC/di18:0PC(DSPC)/cholesterol and PLPC/DSPC/cholesterol mixtures are micrometer-sized, and only the POPC/DSPC/cholesterol system has nanoscopic domains. The results indicate that some HLs with polyunsaturated chains are not linactants, and the monounsaturated POPC displays both properties of weak linactants and "Ld-phase" lipids such as di18:1PC (DOPC). The obtained phase boundaries from giant unilamellar vesicles (GUV) show that both POPC and PLPC partition well in the Lo phases. Our MD simulations reveal that these hybrid lipids decrease the order and compactness of Lo domains. Thus, hybrid lipids distinguish themselves from other lipid groups in this combined "partitioning and loosening" ability, which could explain why the Lo domains of GUVs, which often do not contain HL, are more compact than the raft domains in cell membranes. Our line tension measurement and Monte Carlo simulation both show that even the monounsaturated POPC is a weak linactant with only modest ability to occupy domain boundaries and reduce line tension. A more important property of HLs is that they can reduce physical property differences of Lo and Ld bulk domains, which also reduces line tension at domain boundaries.
Directory of Open Access Journals (Sweden)
Wang Zhenhua
2015-02-01
Full Text Available To improve the computational efficiency and hold calculation accuracy at the same time, we study the parallel computation for radiation heat transfer. In this paper, the discrete ordinates method (DOM and the spatial domain decomposition parallelization (DDP are combined by message passing interface (MPI language. The DDP–DOM computation of the radiation heat transfer within the rectangular furnace is described. When the result of DDP–DOM along one-dimensional direction is compared with that along multi-dimensional directions, it is found that the result of the latter one has higher precision without considering the medium scattering. Meanwhile, an in-depth study of the convergence of DDP–DOM for radiation heat transfer is made. Analyzing the cause of the weak convergence, we relate the total number of iteration steps when the convergence is obtained to the number of sub-domains. When we decompose the spatial domain along one-, two- and three-dimensional directions, different linear relationships between the number of total iteration steps and the number of sub-domains will be possessed separately, then several equations are developed to show the relationships. Using the equations, some phenomena in DDP–DOM can be made clear easily. At the same time, the correctness of the equations is verified.
A New Hybrid Watermarking Algorithm for Images in Frequency Domain
Directory of Open Access Journals (Sweden)
AhmadReza Naghsh-Nilchi
2008-03-01
Full Text Available In recent years, digital watermarking has become a popular technique for digital images by hiding secret information which can protect the copyright. The goal of this paper is to develop a hybrid watermarking algorithm. This algorithm used DCT coefficient and DWT coefficient to embedding watermark, and the extracting procedure is blind. The proposed approach is robust to a variety of signal distortions, such as JPEG, image cropping and scaling.
A Temporal Domain Decomposition Algorithmic Scheme for Large-Scale Dynamic Traffic Assignment
Directory of Open Access Journals (Sweden)
Eric J. Nava
2012-03-01
This paper presents a temporal decomposition scheme for large spatial- and temporal-scale dynamic traffic assignment, in which the entire analysis period is divided into Epochs. Vehicle assignment is performed sequentially in each Epoch, thus improving the model scalability and confining the peak run-time memory requirement regardless of the total analysis period. A proposed self-turning scheme adaptively searches for the run-time-optimal Epoch setting during iterations regardless of the characteristics of the modeled network. Extensive numerical experiments confirm the promising performance of the proposed algorithmic schemes.
Near-Optimal Hybrid Processing for Massive MIMO Systems via Matrix Decomposition
Ni, Weiheng; Dong, Xiaodai; Lu, Wu-Sheng
2015-01-01
For the practical implementation of massive multiple-input multiple-output (MIMO) systems, the hybrid processing (precoding/combining) structure is promising to reduce the high cost rendered by large number of RF chains of the traditional processing structure. The hybrid processing is performed through low-dimensional digital baseband processing combined with analog RF processing enabled by phase shifters. We propose to design hybrid RF and baseband precoders/combiners for multi-stream transm...
Niu, Mingfei; Wang, Yufang; Sun, Shaolong; Li, Yongwu
2016-06-01
To enhance prediction reliability and accuracy, a hybrid model based on the promising principle of "decomposition and ensemble" and a recently proposed meta-heuristic called grey wolf optimizer (GWO) is introduced for daily PM2.5 concentration forecasting. Compared with existing PM2.5 forecasting methods, this proposed model has improved the prediction accuracy and hit rates of directional prediction. The proposed model involves three main steps, i.e., decomposing the original PM2.5 series into several intrinsic mode functions (IMFs) via complementary ensemble empirical mode decomposition (CEEMD) for simplifying the complex data; individually predicting each IMF with support vector regression (SVR) optimized by GWO; integrating all predicted IMFs for the ensemble result as the final prediction by another SVR optimized by GWO. Seven benchmark models, including single artificial intelligence (AI) models, other decomposition-ensemble models with different decomposition methods and models with the same decomposition-ensemble method but optimized by different algorithms, are considered to verify the superiority of the proposed hybrid model. The empirical study indicates that the proposed hybrid decomposition-ensemble model is remarkably superior to all considered benchmark models for its higher prediction accuracy and hit rates of directional prediction.
A hybrid analysis method for linear dynamic soil-structure interaction in time and frequency domain
Institute of Scientific and Technical Information of China (English)
丁海平; 廖振鹏
2001-01-01
A hybrid analysis method in time and frequency domains for linear soil-structure interaction is presented. First, the time domain solution of the system with Rayleigh damping excited by a short time impulse is obtained by the decoupling numerical simulation technique of near-field wave motion. Then, the corresponding frequency domain solution can be got by Fourier transform. According to the relationship between damping value and dynamic re-sponse of a system, the solution of the system with complex damping can be got by Taylor expansion. The hybrid method makes the best of decoupling and explicit algorithm in time domain, and increases the calculation efficien-cy for linear soil-structure interaction analysis.
Institute of Scientific and Technical Information of China (English)
Qiu Yasong; Bai Junqiang
2015-01-01
In this paper a new flow field prediction method which is independent of the governing equations, is developed to predict stationary flow fields of variable physical domain. Predicted flow fields come from linear superposition of selected basis modes generated by proper orthogonal decomposition (POD). Instead of traditional projection methods, kriging surrogate model is used to calculate the superposition coefficients through building approximate function relationships between profile geometry parameters of physical domain and these coefficients. In this context, the problem which troubles the traditional POD-projection method due to viscosity and compress-ibility has been avoided in the whole process. Moreover, there are no constraints for the inner prod-uct form, so two forms of simple ones are applied to improving computational efficiency and cope with variable physical domain problem. An iterative algorithm is developed to determine how many basis modes ranking front should be used in the prediction. Testing results prove the feasibility of this new method for subsonic flow field, but also prove that it is not proper for transonic flow field because of the poor predicted shock waves.
Directory of Open Access Journals (Sweden)
Qiu Yasong
2015-02-01
Full Text Available In this paper a new flow field prediction method which is independent of the governing equations, is developed to predict stationary flow fields of variable physical domain. Predicted flow fields come from linear superposition of selected basis modes generated by proper orthogonal decomposition (POD. Instead of traditional projection methods, kriging surrogate model is used to calculate the superposition coefficients through building approximate function relationships between profile geometry parameters of physical domain and these coefficients. In this context, the problem which troubles the traditional POD-projection method due to viscosity and compressibility has been avoided in the whole process. Moreover, there are no constraints for the inner product form, so two forms of simple ones are applied to improving computational efficiency and cope with variable physical domain problem. An iterative algorithm is developed to determine how many basis modes ranking front should be used in the prediction. Testing results prove the feasibility of this new method for subsonic flow field, but also prove that it is not proper for transonic flow field because of the poor predicted shock waves.
Hybrid simulation of whistler excitation by electron beams in two-dimensional non-periodic domains
Energy Technology Data Exchange (ETDEWEB)
Woodroffe, J.R., E-mail: woodrofj@erau.edu; Streltsov, A.V., E-mail: streltsa@erau.edu
2014-11-01
We present a two-dimensional hybrid fluid-PIC scheme for the simulation of whistler wave excitation by relativistic electron beams. This scheme includes a number of features which are novel to simulations of this type, including non-periodic boundary conditions and fresh particle injection. Results from our model suggest that non-periodicity of the simulation domain results in the development of fundamentally different wave characteristics than are observed in periodic domains.
Yücel, Abdulkadir C.
2013-07-01
Reliable and effective wireless communication and tracking systems in mine environments are key to ensure miners\\' productivity and safety during routine operations and catastrophic events. The design of such systems greatly benefits from simulation tools capable of analyzing electromagnetic (EM) wave propagation in long mine tunnels and large mine galleries. Existing simulation tools for analyzing EM wave propagation in such environments employ modal decompositions (Emslie et. al., IEEE Trans. Antennas Propag., 23, 192-205, 1975), ray-tracing techniques (Zhang, IEEE Tran. Vehic. Tech., 5, 1308-1314, 2003), and full wave methods. Modal approaches and ray-tracing techniques cannot accurately account for the presence of miners and their equipments, as well as wall roughness (especially when the latter is comparable to the wavelength). Full-wave methods do not suffer from such restrictions but require prohibitively large computational resources. To partially alleviate this computational burden, a 2D integral equation-based domain decomposition technique has recently been proposed (Bakir et. al., in Proc. IEEE Int. Symp. APS, 1-2, 8-14 July 2012). © 2013 IEEE.
Directory of Open Access Journals (Sweden)
L.H. Yang
1992-01-01
Full Text Available A molecular dynamics algorithm for performing large-scale simulations using the Parallel C Preprocessor (PCP programming paradigm on the BBN TC2000, a massively parallel computer, is discussed. The algorithm uses a linked-cell data structure to obtain the near neighbors of each atom as time evoles. Each processor is assigned to a geometric domain containing many subcells and the storage for that domain is private to the processor. Within this scheme, the interdomain (i.e., interprocessor communication is minimized.
Directory of Open Access Journals (Sweden)
Jesús García
2012-01-01
Full Text Available The application of a 3D domain decomposition finite-element and spherical mode expansion for the design of planar ESPAR (electronically steerable passive array radiator made with probe-fed circular microstrip patches is presented in this work. A global generalized scattering matrix (GSM in terms of spherical modes is obtained analytically from the GSM of the isolated patches by using rotation and translation properties of spherical waves. The whole behaviour of the array is characterized including all the mutual coupling effects between its elements. This procedure has been firstly validated by analyzing an array of monopoles on a ground plane, and then it has been applied to synthesize a prescribed radiation pattern optimizing the reactive loads connected to the feeding ports of the array of circular patches by means of a genetic algorithm.
Energy Technology Data Exchange (ETDEWEB)
Javidi, M. [Department of Mathematics, Iran University of Science and Technology, Narmak, Tehran 16844 (Iran, Islamic Republic of)], E-mail: mo_javidi@yahoo.com; Golbabai, A. [Department of Mathematics, Iran University of Science and Technology, Narmak, Tehran 16844 (Iran, Islamic Republic of)], E-mail: golbabai@iust.ac.ir
2009-01-30
In this study, we use the spectral collocation method using Chebyshev polynomials for spatial derivatives and fourth order Runge-Kutta method for time integration to solve the generalized Burger's-Huxley equation (GBHE). To reduce round-off error in spectral collocation (pseudospectral) method we use preconditioning. Firstly, theory of application of Chebyshev spectral collocation method with preconditioning (CSCMP) and domain decomposition on the generalized Burger's-Huxley equation presented. This method yields a system of ordinary differential algebric equations (DAEs). Secondly, we use fourth order Runge-Kutta formula for the numerical integration of the system of DAEs. The numerical results obtained by this way have been compared with the exact solution to show the efficiency of the method.
Application of multi-thread computing and domain decomposition to the 3-D neutronics Fem code Cronos
Energy Technology Data Exchange (ETDEWEB)
Ragusa, J.C. [CEA Saclay, Direction de l' Energie Nucleaire, Service d' Etudes des Reacteurs et de Modelisations Avancees (DEN/SERMA), 91 - Gif sur Yvette (France)
2003-07-01
The purpose of this paper is to present the parallelization of the flux solver and the isotopic depletion module of the code, either using Message Passing Interface (MPI) or OpenMP. Thread parallelism using OpenMP was used to parallelize the mixed dual FEM (finite element method) flux solver MINOS. Investigations regarding the opportunity of mixing parallelism paradigms will be discussed. The isotopic depletion module was parallelized using domain decomposition and MPI. An attempt at using OpenMP was unsuccessful and will be explained. This paper is organized as follows: the first section recalls the different types of parallelism. The mixed dual flux solver and its parallelization are then presented. In the third section, we describe the isotopic depletion solver and its parallelization; and finally conclude with some future perspectives. Parallel applications are mandatory for fine mesh 3-dimensional transport and simplified transport multigroup calculations. The MINOS solver of the FEM neutronics code CRONOS2 was parallelized using the directive based standard OpenMP. An efficiency of 80% (resp. 60%) was achieved with 2 (resp. 4) threads. Parallelization of the isotopic depletion solver was obtained using domain decomposition principles and MPI. Efficiencies greater than 90% were reached. These parallel implementations were tested on a shared memory symmetric multiprocessor (SMP) cluster machine. The OpenMP implementation in the solver MINOS is only the first step towards fully using the SMPs cluster potential with a mixed mode parallelism. Mixed mode parallelism can be achieved by combining message passing interface between clusters with OpenMP implicit parallelism within a cluster.
Modal Identification of Output-Only Systems using Frequency Domain Decomposition
DEFF Research Database (Denmark)
Brincker, Rune; Zhang, L.; Andersen, P.
2000-01-01
In this paper a new frequency domain technique is introduced for the modal identification from ambient responses, ie. in the case where the modal parameters must be estimated without knowing the input exciting the system. By its user friendliness the technique is closely related to the classical ...
2009-05-01
monographs by Quarteroni and Valli [10] and Toselli and Widlund [11]) culminating in the increasing appli- cation of these methods for High Performance Comput...Equations, Oxford University Press, Oxford, UK, 1999. [11] Toselli , A. and Widlund, O., Domain Decomposi- tion Methods – Algorithms and Theory, Springer
Kuo, Kenneth K.; Lu, Yeu-Cherng; Chiaverini, Martin J.; Harting, George C.; Johnson, David K.; Serin, Nadir
1995-01-01
The experimental study on the fundamental processes involved in fuel decomposition and boundary-layer combustion in hybrid rocket motors is continuously being conducted at the High Pressure Combustion Laboratory of The Pennsylvania State University. This research will provide a useful engineering technology base in the development of hybrid rocket motors as well as a fundamental understanding of the complex processes involved in hybrid propulsion. A high-pressure, 2-D slab motor has been designed, manufactured, and utilized for conducting seven test firings using HTPB fuel processed at PSU. A total of 20 fuel slabs have been received from the Mcdonnell Douglas Aerospace Corporation. Ten of these fuel slabs contain an array of fine-wire thermocouples for measuring solid fuel surface and subsurface temperatures. Diagnostic instrumentation used in the test include high-frequency pressure transducers for measuring static and dynamic motor pressures and fine-wire thermocouples for measuring solid fuel surface and subsurface temperatures. The ultrasonic pulse-echo technique as well as a real-time x-ray radiography system have been used to obtain independent measurements of instantaneous solid fuel regression rates.
Directory of Open Access Journals (Sweden)
Jiani Heng
2016-01-01
Full Text Available Power load forecasting always plays a considerable role in the management of a power system, as accurate forecasting provides a guarantee for the daily operation of the power grid. It has been widely demonstrated in forecasting that hybrid forecasts can improve forecast performance compared with individual forecasts. In this paper, a hybrid forecasting approach, comprising Empirical Mode Decomposition, CSA (Cuckoo Search Algorithm, and WNN (Wavelet Neural Network, is proposed. This approach constructs a more valid forecasting structure and more stable results than traditional ANN (Artificial Neural Network models such as BPNN (Back Propagation Neural Network, GABPNN (Back Propagation Neural Network Optimized by Genetic Algorithm, and WNN. To evaluate the forecasting performance of the proposed model, a half-hourly power load in New South Wales of Australia is used as a case study in this paper. The experimental results demonstrate that the proposed hybrid model is not only simple but also able to satisfactorily approximate the actual power load and can be an effective tool in planning and dispatch for smart grids.
Directory of Open Access Journals (Sweden)
Qiuming Cheng
2007-06-01
Full Text Available The patterns shown on two-dimensional images (fields used in geosciences reflect the end products of geo-processes that occurred on the surface and in the subsurface of the Earth. Anisotropy of these types of patterns can provide information useful for interpretation of geo-processes and identification of features in the mapped area. Quantification of the anisotropy property is therefore essential for image processing and interpretation. This paper introduces several techniques newly developed on the basis of multifractal modeling in space, Fourier frequency, and eigen domains, respectively. A singularity analysis method implemented in the space domain can be used to quantify the intensity and anisotropy of local singularities. The second method, called S-A, characterizes the generalized scale invariance property of a field in the Fourier frequency domain. The third method characterizes the field using a power-law model on the basis of eigenvalues and eigenvectors of the field. The applications of these methods are demonstrated with a case study of Environment Scan Electric Microscope (ESEM microimages for identification of sphalerite (ZnS ore minerals from the Jinding Pb/Zn/Ag mineral deposit in Shangjiang District, Yunnan Province, China.
He, Jingjing; Zhou, Yibin; Guan, Xuefei; Zhang, Wei; Zhang, Weifang; Liu, Yongming
2016-08-16
Structural health monitoring has been studied by a number of researchers as well as various industries to keep up with the increasing demand for preventive maintenance routines. This work presents a novel method for reconstruct prompt, informed strain/stress responses at the hot spots of the structures based on strain measurements at remote locations. The structural responses measured from usage monitoring system at available locations are decomposed into modal responses using empirical mode decomposition. Transformation equations based on finite element modeling are derived to extrapolate the modal responses from the measured locations to critical locations where direct sensor measurements are not available. Then, two numerical examples (a two-span beam and a 19956-degree of freedom simplified airfoil) are used to demonstrate the overall reconstruction method. Finally, the present work investigates the effectiveness and accuracy of the method through a set of experiments conducted on an aluminium alloy cantilever beam commonly used in air vehicle and spacecraft. The experiments collect the vibration strain signals of the beam via optical fiber sensors. Reconstruction results are compared with theoretical solutions and a detailed error analysis is also provided.
Directory of Open Access Journals (Sweden)
Jingjing He
2016-08-01
Full Text Available Structural health monitoring has been studied by a number of researchers as well as various industries to keep up with the increasing demand for preventive maintenance routines. This work presents a novel method for reconstruct prompt, informed strain/stress responses at the hot spots of the structures based on strain measurements at remote locations. The structural responses measured from usage monitoring system at available locations are decomposed into modal responses using empirical mode decomposition. Transformation equations based on finite element modeling are derived to extrapolate the modal responses from the measured locations to critical locations where direct sensor measurements are not available. Then, two numerical examples (a two-span beam and a 19956-degree of freedom simplified airfoil are used to demonstrate the overall reconstruction method. Finally, the present work investigates the effectiveness and accuracy of the method through a set of experiments conducted on an aluminium alloy cantilever beam commonly used in air vehicle and spacecraft. The experiments collect the vibration strain signals of the beam via optical fiber sensors. Reconstruction results are compared with theoretical solutions and a detailed error analysis is also provided.
Directory of Open Access Journals (Sweden)
Nantian Huang
2016-11-01
Full Text Available Accurate wind speed forecasting is a fundamental element of wind power prediction. Thus, a new hybrid wind speed forecasting model, using variational mode decomposition (VMD, the partial autocorrelation function (PACF, and weighted regularized extreme learning machine (WRELM, is proposed to improve the accuracy of wind speed forecasting. First, the historic wind speed time series is decomposed into several intrinsic mode functions (IMFs. Second, the partial correlation of each IMF sequence is analyzed using PACF to select the optimal subfeature set for particular predictors of each IMF. Then, the predictors of each IMF are constructed in order to enhance its strength using WRELM. Finally, wind speed is obtained by adding up all the predictors. The experiment, using real wind speed data, verified the effectiveness and advancement of the new approach.
Stupfel, Bruno; Lecouvez, Matthieu
2016-10-01
For the solution of the time-harmonic electromagnetic scattering problem by inhomogeneous 3-D objects, a one-way domain decomposition method (DDM) is considered: the computational domain is partitioned into concentric subdomains on the interfaces of which Robin-type transmission conditions (TCs) are prescribed; an integral representation of the electromagnetic fields on the outer boundary constitutes an exact radiation condition. The global system obtained after discretization of the finite element (FE) formulations is solved via a Krylov subspace iterative method (GMRES). It is preconditioned in such a way that, essentially, only the solution of the FE subsystems in each subdomain is required. This is made possible by a computationally cheap H (curl)- H (div) transformation performed on the interfaces that separate the two outermost subdomains. The eigenvalues of the preconditioned matrix of the system are bounded by two, and optimized values of the coefficients involved in the local TCs on the interfaces are determined so as to maximize the minimum eigenvalue. Numerical experiments are presented that illustrate the numerical accuracy of this technique, its fast convergence, and legitimate the choices made for the optimized coefficients.
Liu, Liangbing; Tao, Chao; Liu, XiaoJun; Deng, Mingxi; Wang, Senhua; Liu, Jun
2015-10-19
Photoacoustic tomography is a promising and rapidly developed methodology of biomedical imaging. It confronts an increasing urgent problem to reconstruct the image from weak and noisy photoacoustic signals, owing to its high benefit in extending the imaging depth and decreasing the dose of laser exposure. Based on the time-domain characteristics of photoacoustic signals, a pulse decomposition algorithm is proposed to reconstruct a photoacoustic image from signals with low signal-to-noise ratio. In this method, a photoacoustic signal is decomposed as the weighted summation of a set of pulses in the time-domain. Images are reconstructed from the weight factors, which are directly related to the optical absorption coefficient. Both simulation and experiment are conducted to test the performance of the method. Numerical simulations show that when the signal-to-noise ratio is -4 dB, the proposed method decreases the reconstruction error to about 17%, in comparison with the conventional back-projection method. Moreover, it can produce acceptable images even when the signal-to-noise ratio is decreased to -10 dB. Experiments show that, when the laser influence level is low, the proposed method achieves a relatively clean image of a hair phantom with some well preserved pattern details. The proposed method demonstrates imaging potential of photoacoustic tomography in expanding applications.
Zhou, Qingping; Jiang, Haiyan; Wang, Jianzhou; Zhou, Jianling
2014-10-15
Exposure to high concentrations of fine particulate matter (PM₂.₅) can cause serious health problems because PM₂.₅ contains microscopic solid or liquid droplets that are sufficiently small to be ingested deep into human lungs. Thus, daily prediction of PM₂.₅ levels is notably important for regulatory plans that inform the public and restrict social activities in advance when harmful episodes are foreseen. A hybrid EEMD-GRNN (ensemble empirical mode decomposition-general regression neural network) model based on data preprocessing and analysis is firstly proposed in this paper for one-day-ahead prediction of PM₂.₅ concentrations. The EEMD part is utilized to decompose original PM₂.₅ data into several intrinsic mode functions (IMFs), while the GRNN part is used for the prediction of each IMF. The hybrid EEMD-GRNN model is trained using input variables obtained from principal component regression (PCR) model to remove redundancy. These input variables accurately and succinctly reflect the relationships between PM₂.₅ and both air quality and meteorological data. The model is trained with data from January 1 to November 1, 2013 and is validated with data from November 2 to November 21, 2013 in Xi'an Province, China. The experimental results show that the developed hybrid EEMD-GRNN model outperforms a single GRNN model without EEMD, a multiple linear regression (MLR) model, a PCR model, and a traditional autoregressive integrated moving average (ARIMA) model. The hybrid model with fast and accurate results can be used to develop rapid air quality warning systems.
Transonic solutions of a wing/pylon/finned store using hybrid domain decomposition
Newman, James C., III; Baysal, Oktay
1992-01-01
Transonic Euler calculations about a complex multicomponent configuration are presented. The 3D Euler equations are solved utilizing an upwind-biased, alternating direction implicit, approximately factored, multigrid algorithm. Computational results are compared to experimental data of the finned store in a carriage position.
Directory of Open Access Journals (Sweden)
Tromeur-Dervout Damien
2013-12-01
Full Text Available This paper deals with the representation of the trace of iterative Schwarz solutions at the interfaces of domain decomposition to approximate adaptively the interface error operator. This allows to build a cost-effectively accelerating of the convergence of the iterative method by extending to the vectorial case the Aitken’s accelerating convergence technique. The first representation is based on the building of a nonuniform discrete Fourier transform defined on a non-regular grid. We show how to construct a Fourier basis of dimension N+1 on this grid by building numerically a sesquilinear form, its exact accuracy to represent trigonometric polynomials of degree N / 2, and its spectral approximation property that depends on the continuity of the function to approximate. The decay of Fourier-like modes of the approximation of the trace of the iterative solution at the interfaces provides an estimate to adaptively select the modes involved in the acceleration. The drawback of this approach is to be dependent on the continuity of the trace of the iterated solution at the interfaces. The second representation, purely algebraic, uses a singular value decomposition of the trace of the iterative solution at the interfaces to provide a set of orthogonal singular vectors of which the associated singular values provide an estimate to adapt the acceleration. The resulting Aitken-Schwarz methodology is then applied to large scale computing on 3D linear Darcy flow where the permeability follows a log normal random distribution. Cet acte traite de la représentation des solutions itérées aux interfaces de la méthode de décomposition de domaine de type Schwarz afin d’approximer de manière adaptative son opérateur d’erreur aux interfaces des sous domaines. Ceci permet de construire de manière économique l’accélération de la convergence de la méthode itérative en étendant la technique d’accélération de la convergence de Aitken au cas
Energy Technology Data Exchange (ETDEWEB)
Hoekstra, R.
2003-10-01
Economic processes generate a variety of material flows, which cause resource problems through the depletion of natural resources and environmental issues due to the emission of pollutants. This thesis presents an analytical method to study the relationship between the monetary economy and the 'physical economy'. In particular, this method can assess the impact of structural change in the economy on physical throughput. The starting point for the approach is the development of an elaborate version of the physical input-output table (PIOT), which acts as an economic-environmental accounting framework for the physical economy. In the empirical application, hybrid-unit input-output (I/O) tables, which combine physical and monetary information, are constructed for iron and steel, and plastic products for the Netherlands for the years 1990 and 1997. The impact of structural change on material flows is analyzed using Structural Decomposition Analysis (SDA), whic specifies effects such as sectoral shifts, technological change, and alterations in consumer spending and international trade patterns. The study thoroughly reviews the application of SDA to environmental issues, compares the method with other decomposition methods, and develops new mathematical specifications. An SDA is performed using the hybrid-unit input-output tables for the Netherlands. The results are subsequently used in novel forecasting and backcasting scenario analyses for the period 1997-2030. The results show that dematerialization of iron and steel, and plastics, has generally not occurred in the recent past (1990-1997), and will not occur, under a wide variety of scenario assumptions, in the future (1997-2030)
Domain decomposition based iterative methods for nonlinear elliptic finite element problems
Energy Technology Data Exchange (ETDEWEB)
Cai, X.C. [Univ. of Colorado, Boulder, CO (United States)
1994-12-31
The class of overlapping Schwarz algorithms has been extensively studied for linear elliptic finite element problems. In this presentation, the author considers the solution of systems of nonlinear algebraic equations arising from the finite element discretization of some nonlinear elliptic equations. Several overlapping Schwarz algorithms, including the additive and multiplicative versions, with inexact Newton acceleration will be discussed. The author shows that the convergence rate of the Newton`s method is independent of the mesh size used in the finite element discretization, and also independent of the number of subdomains into which the original domain in decomposed. Numerical examples will be presented.
M. Genseberger (Menno)
2008-01-01
htmlabstractMost computational work in Jacobi-Davidson [9], an iterative method for large scale eigenvalue problems, is due to a so-called correction equation. In [5] a strategy for the approximate solution of the correction equation was proposed. This strategy is based on a domain decomposition
Directory of Open Access Journals (Sweden)
Jingang Liang
2016-06-01
Full Text Available Because of prohibitive data storage requirements in large-scale simulations, the memory problem is an obstacle for Monte Carlo (MC codes in accomplishing pin-wise three-dimensional (3D full-core calculations, particularly for whole-core depletion analyses. Various kinds of data are evaluated and quantificational total memory requirements are analyzed based on the Reactor Monte Carlo (RMC code, showing that tally data, material data, and isotope densities in depletion are three major parts of memory storage. The domain decomposition method is investigated as a means of saving memory, by dividing spatial geometry into domains that are simulated separately by parallel processors. For the validity of particle tracking during transport simulations, particles need to be communicated between domains. In consideration of efficiency, an asynchronous particle communication algorithm is designed and implemented. Furthermore, we couple the domain decomposition method with MC burnup process, under a strategy of utilizing consistent domain partition in both transport and depletion modules. A numerical test of 3D full-core burnup calculations is carried out, indicating that the RMC code, with the domain decomposition method, is capable of pin-wise full-core burnup calculations with millions of depletion regions.
Institute of Scientific and Technical Information of China (English)
付朝江; 张武
2006-01-01
Parallel finite element method using domain decomposition technique is adapted to a distributed parallel environment of workstation cluster. The algorithm is presented for parallelization of the preconditioned conjugate gradient method based on domain decomposition. Using the developed code, a dam structural analysis problem is solved on workstation cluster and results are given. The parallel performance is analyzed.
Meng, Xiang; Zhang, Ruifeng; Fu, Zhongheng; Zhang, Qianfan
2016-10-05
Hybrid organic-inorganic perovskites, represented by materials in the CH3NH3PbI3 series, have become one of the most promising materials for solar cells with a high power conversion efficiency and low cost. The ordered Pb-I cage in such hybrid perovskites can induce the polarized cations to form a variety of polarization domains with long-range order, which will lead to the formation of specific atomic conformations or metastable crystalline phases, unique electronic band structures and optical absorption properties. Such domain-dependent characteristics play a critical role in the phase transition and service stability of such solar cells, and also open up the opportunity of tuning their electronic structure. In the present study, we systematically investigate the band structures and optical absorption properties of different electronically ordered domains in CH3NH3PbI3. By comparing different perovskites containing various cations, we have clarified the important influence of cation polarization on domain-dependent properties. Our results provide not only a possible pathway for the manipulation of band structure by applying an external field, but also a novel scheme for improving the performance and stability of hybrid perovskites.
Identificaiton of Shc Src Homology 2 Domain-Binding Peptoid – Peptide Hybrids
Choi, Won Jun; Kim, Sung Eun; Stephen, Andrew G.; Weidlich, Iwona; Giubellino, Alessio; Liu, Fa; Worthy, Karen M.; Bindu, Lakshman; Fivash, Matthew J.; Nicklaus, Marc C.; Bottaro, Donald P.; Fisher, Robert J.; Burke, Terrence R.
2009-01-01
A fluorescence anisotropy (FA) competition – based Shc Src homology 2 (SH2) domain-binding was established using the high affinity fluorescein isothiocyanate (FITC)-containing peptide, FITC-NH-(CH2)4-CO-pY-Q-G-L-S-amide (8; Kd = 0.35 μM). Examination of a series of open – chain bis-alkenylamide containing peptides, prepared as ring – closing metathesis precursors, showed that the highest affinities were obtained by replacement of the original Gly residue with Nα-substituted Gly (NSG) “peptoid” residues. This provided peptoid-peptide hybrids of the form, “Ac-pY-Q-[NSG]-L-amide.” Depending on the NSG substituent, certain of these hybrids exhibited up to 40 – fold higher Shc SH2 domain binding affinity than the parent Gly-containing peptide (IC50 = 248 μM), (for example, N-homo-allyl analogue 50; IC50 = 6 μM). To our knowledge, this work represents the first successful example of the application of peptoid-peptide hybrids in the design of SH2 domain-binding antagonists. These results could provide a foundation for further structural optimization of Shc SH2 domain-binding peptide mimetics. PMID:19226165
Identification of Shc Src homology 2 domain-binding peptoid-peptide hybrids.
Choi, Won Jun; Kim, Sung-Eun; Stephen, Andrew G; Weidlich, Iwona; Giubellino, Alessio; Liu, Fa; Worthy, Karen M; Bindu, Lakshman; Fivash, Matthew J; Nicklaus, Marc C; Bottaro, Donald P; Fisher, Robert J; Burke, Terrence R
2009-03-26
A fluorescence anisotropy (FA) competition-based Shc Src homology 2 (SH2) domain-binding was established using the high affinity fluorescein isothiocyanate (FITC) containing peptide, FITC-NH-(CH2)4-CO-pY-Q-G-L-S-amide (8; Kd = 0.35 microM). Examination of a series of open-chain bis-alkenylamide containing peptides, prepared as ring-closing metathesis precursors, showed that the highest affinities were obtained by replacement of the original Gly residue with N alpha-substituted Gly (NSG) "peptoid" residues. This provided peptoid-peptide hybrids of the form "Ac-pY-Q-[NSG]-L-amide." Depending on the NSG substituent, certain of these hybrids exhibited up to 40-fold higher Shc SH2 domain-binding affinity than the parent Gly-containing peptide (IC50 = 248 microM) (for example, for N-homoallyl analogue 50, IC50 = 6 microM). To our knowledge, this work represents the first successful example of the application of peptoid-peptide hybrids in the design of SH2 domain-binding antagonists. These results could provide a foundation for further structural optimization of Shc SH2 domain-binding peptide mimetics.
Directory of Open Access Journals (Sweden)
Zongxi Qu
2016-01-01
Full Text Available As a type of clean and renewable energy, the superiority of wind power has increasingly captured the world’s attention. Reliable and precise wind speed prediction is vital for wind power generation systems. Thus, a more effective and precise prediction model is essentially needed in the field of wind speed forecasting. Most previous forecasting models could adapt to various wind speed series data; however, these models ignored the importance of the data preprocessing and model parameter optimization. In view of its importance, a novel hybrid ensemble learning paradigm is proposed. In this model, the original wind speed data is firstly divided into a finite set of signal components by ensemble empirical mode decomposition, and then each signal is predicted by several artificial intelligence models with optimized parameters by using the fruit fly optimization algorithm and the final prediction values were obtained by reconstructing the refined series. To estimate the forecasting ability of the proposed model, 15 min wind speed data for wind farms in the coastal areas of China was performed to forecast as a case study. The empirical results show that the proposed hybrid model is superior to some existing traditional forecasting models regarding forecast performance.
Energy Technology Data Exchange (ETDEWEB)
Clerc, S
1998-07-01
In this work, the numerical simulation of fluid dynamics equations is addressed. Implicit upwind schemes of finite volume type are used for this purpose. The first part of the dissertation deals with the improvement of the computational precision in unfavourable situations. A non-conservative treatment of some source terms is studied in order to correct some shortcomings of the usual operator-splitting method. Besides, finite volume schemes based on Godunov's approach are unsuited to compute low Mach number flows. A modification of the up-winding by preconditioning is introduced to correct this defect. The second part deals with the solution of steady-state problems arising from an implicit discretization of the equations. A well-posed linearized boundary value problem is formulated. We prove the convergence of a domain decomposition algorithm of Schwartz type for this problem. This algorithm is implemented either directly, or in a Schur complement framework. Finally, another approach is proposed, which consists in decomposing the non-linear steady state problem. (author)
The Use of Domain Decomposition in Accelerating the Convergence of Quasihyperbolic Systems
Parent, Bernard; Sislian, Jean P.
2002-06-01
This paper proposes an alternate form of the active-domain method [K. Nakahashi and E. Saitoh, AIAA J.35, 1280 (1997)] that is applicable to streamwise separated flows. Named the "marching window," the algorithm consists of performing pseudo-time iterations on a minimal width subdomain composed of a sequence of cross-stream planes of nodes. The upstream boundary of the subdomain is positioned such that all nodes upstream exhibit a residual smaller than the user-specified convergence threshold. The advancement of the downstream boundary follows the advancement of the upstream boundary, except in zones of significant streamwise ellipticity, where a streamwise ellipticity sensor ensures its continuous progress. Compared to the standard pseudo-time-marching approach, the marching window decreases the work required for convergence by up to 24 times for flows with little streamwise ellipticity and by up to eight times for flows with large streamwise separated regions. Storage is reduced by up to six times by not allocating memory to the nodes not included in the computational subdomain. The marching window satisfies the same convergence criterion as the standard pseudo-time-stepping methods, hence resulting in the same converged solution within the tolerance of the user-specified convergence threshold. The algorithm is not restricted to a discretization stencil and pseudo-time-stepping scheme in particular and is used here with the Yee-Roe scheme and block-implicit approximate factorization solving the Favre-averaged Navier-Stokes (FANS) equations closed by the Wilcox kω turbulence model. The eigenstructure of the FANS equations is also presented.
Jones, Adam; Utyuzhnikov, Sergey
2017-08-01
Turbulent flow in a ribbed channel is studied using an efficient near-wall domain decomposition (NDD) method. The NDD approach is formulated by splitting the computational domain into an inner and outer region, with an interface boundary between the two. The computational mesh covers the outer region, and the flow in this region is solved using the open-source CFD code Code_Saturne with special boundary conditions on the interface boundary, called interface boundary conditions (IBCs). The IBCs are of Robin type and incorporate the effect of the inner region on the flow in the outer region. IBCs are formulated in terms of the distance from the interface boundary to the wall in the inner region. It is demonstrated that up to 90% of the region between the ribs in the ribbed passage can be removed from the computational mesh with an error on the friction factor within 2.5%. In addition, computations with NDD are faster than computations based on low Reynolds number (LRN) models by a factor of five. Different rib heights can be studied with the same mesh in the outer region without affecting the accuracy of the friction factor. This is tested with six different rib heights in an example of a design optimisation study. It is found that the friction factors computed with NDD are almost identical to the fully-resolved results. When used for inverse problems, NDD is considerably more efficient than LRN computations because only one computation needs to be performed and only one mesh needs to be generated.
Li, Zhong-xiao; Li, Zhen-chun
2017-08-01
Adaptive multiple subtraction is an important step for successfully conducting surface-related multiple elimination in marine seismic exploration. 2D adaptive multiple subtraction conducted in the parabolic Radon domain has been proposed to better separate primaries and multiples than 2D adaptive multiple subtraction conducted in the time-offset domain. Additionally, the parabolic Radon domain hybrid demultiple method combining parabolic Radon filtering and parabolic Radon domain 2D adaptive multiple subtraction can better remove multiples than the cascaded demultiple method using time-offset domain 2D adaptive multiple subtraction and the parabolic Radon transform method sequentially. To solve the matching filter in the optimization problem with L1 norm minimization constraint of primaries, traditional parabolic Radon domain 2D adaptive multiple subtraction uses the iterative reweighted least squares (IRLS) algorithm, which is computationally expensive for solving a weighted LS inversion in each iteration. In this paper we introduce the fast iterative shrinkage thresholding algorithm (FISTA) as a faster alternative to the IRLS algorithm for parabolic Radon domain 2D adaptive multiple subtraction. FISTA uses the shrinkage-thresholding operator to promote the sparsity of estimated primaries and solves the 2D matching filter with iterative steps. FISTA based parabolic Radon domain 2D adaptive multiple subtraction reduces the computation time effectively while achieving similar accuracy compared with IRLS based parabolic Radon domain 2D adaptive multiple subtraction. Additionally, the provided examples show that FISTA based parabolic Radon domain 2D adaptive multiple subtraction can better separate primaries and multiples than FISTA based time-offset domain 2D adaptive multiple subtraction. Furthermore, we introduce FISTA based parabolic Radon domain 2D adaptive multiple subtraction into the parabolic Radon domain hybrid demultiple method to improve its computation
Zampini, Stefano
2017-08-03
Multilevel balancing domain decomposition by constraints (BDDC) deluxe algorithms are developed for the saddle point problems arising from mixed formulations of Darcy flow in porous media. In addition to the standard no-net-flux constraints on each face, adaptive primal constraints obtained from the solutions of local generalized eigenvalue problems are included to control the condition number. Special deluxe scaling and local generalized eigenvalue problems are designed in order to make sure that these additional primal variables lie in a benign subspace in which the preconditioned operator is positive definite. The current multilevel theory for BDDC methods for porous media flow is complemented with an efficient algorithm for the computation of the so-called malign part of the solution, which is needed to make sure the rest of the solution can be obtained using the conjugate gradient iterates lying in the benign subspace. We also propose a new technique, based on the Sherman--Morrison formula, that lets us preserve the complexity of the subdomain local solvers. Condition number estimates are provided under certain standard assumptions. Extensive numerical experiments confirm the theoretical estimates; additional numerical results prove the effectiveness of the method with higher order elements and high-contrast problems from real-world applications.
Higher-order brick-tetrahedron hybrid method for Maxwell's equations in time domain
Winges, Johan; Rylander, Thomas
2016-09-01
We present a higher-order brick-tetrahedron hybrid method for Maxwell's equations in time domain. Brick-shaped elements are used for large homogeneous parts of the computational domain, where we exploit mass-lumping and explicit time-stepping. In regions with complex geometry, we use an unstructured mesh of tetrahedrons that share an interface with the brick-shaped elements and, at the interface, tangential continuity of the electric field is imposed in the weak sense by means of Nitsche's method. Implicit time-stepping is used for the tetrahedrons together with the interface. For cavity resonators, the hybrid method reproduces the lowest non-zero eigenvalues with correct multiplicity and, for geometries without field singularities from sharp corners or edges, the numerical eigenvalues converge towards the analytical result with an error that is approximately proportional to h2p, where h is the cell size and p is the polynomial order of the elements. For a rectangular waveguide, a layer of tetrahedrons embedded in a grid of brick-shaped elements yields a low reflection coefficient that scales approximately as h2p. Finally, we demonstrate hybrid time-stepping for a lossless closed cavity resonator, where the time-domain response is computed for 300,000 time steps without any signs of instabilities.
Energy Technology Data Exchange (ETDEWEB)
Girardi, E
2004-12-15
A new methodology for the solution of the neutron transport equation, based on domain decomposition has been developed. This approach allows us to employ different numerical methods together for a whole core calculation: a variational nodal method, a discrete ordinate nodal method and a method of characteristics. These new developments authorize the use of independent spatial and angular expansion, non-conformal Cartesian and unstructured meshes for each sub-domain, introducing a flexibility of modeling which is not allowed in today available codes. The effectiveness of our multi-domain/multi-method approach has been tested on several configurations. Among them, one particular application: the benchmark model of the Phebus experimental facility at Cea-Cadarache, shows why this new methodology is relevant to problems with strong local heterogeneities. This comparison has showed that the decomposition method brings more accuracy all along with an important reduction of the computer time.
Yu, Yang; Zhao, Zhigang; Shi, Yanrong; Tian, Hua; Liu, Linglong; Bian, Xiaofeng; Xu, Yang; Zheng, Xiaoming; Gan, Lu; Shen, Yumin; Wang, Chaolong; Yu, Xiaowen; Wang, Chunming; Zhang, Xin; Guo, Xiuping; Wang, Jiulin; Ikehashi, Hiroshi; Jiang, Ling; Wan, Jianmin
2016-07-01
Intersubspecific hybrid sterility is a common form of reproductive isolation in rice (Oryza sativa L.), which significantly hampers the utilization of heterosis between indica and japonica varieties. Here, we elucidated the mechanism of S7, which specially causes Aus-japonica/indica hybrid female sterility, through cytological and genetic analysis, map-based cloning, and transformation experiments. Abnormal positioning of polar nuclei and smaller embryo sac were observed in F1 compared with male and female parents. Female gametes carrying S7(cp) and S7(i) were aborted in S7(ai)/S7(cp) and S7(ai)/S7(i), respectively, whereas they were normal in both N22 and Dular possessing a neutral allele, S7(n) S7 was fine mapped to a 139-kb region in the centromere region on chromosome 7, where the recombination was remarkably suppressed due to aggregation of retrotransposons. Among 16 putative open reading frames (ORFs) localized in the mapping region, ORF3 encoding a tetratricopeptide repeat domain containing protein was highly expressed in the pistil. Transformation experiments demonstrated that ORF3 is the candidate gene: downregulated expression of ORF3 restored spikelet fertility and eliminated absolutely preferential transmission of S7(ai) in heterozygote S7(ai)/S7(cp); sterility occurred in the transformants Cpslo17-S7(ai) Our results may provide implications for overcoming hybrid embryo sac sterility in intersubspecific hybrid rice and utilization of hybrid heterosis for cultivated rice improvement.
Zhao, Wei; Xing, Lei; Xie, Yaoqin; Xiong, Guanglei; Elmore, Kimberly; Zhu, Jun; Wang, Luyao; Min, James K
2016-01-01
Increased noise is a general concern for dual-energy material decomposition. Here, we develop an image-domain material decomposition algorithm for dual-energy CT (DECT) by incorporating an edge-preserving filter into the Local HighlY constrained backPRojection Reconstruction (HYPR-LR) framework. With effective use of the non-local mean, the proposed algorithm, which is referred to as HYPR-NLM, reduces the noise in dual energy decomposition while preserving the accuracy of quantitative measurement and spatial resolution of the material-specific dual energy images. We demonstrate the noise reduction and resolution preservation of the algorithm with iodine concentrate numerical phantom by comparing the HYPR-NLM algorithm to the direct matrix inversion, HYPR-LR and iterative image-domain material decomposition (Iter-DECT). We also show the superior performance of the HYPR-NLM over the existing methods by using two sets of cardiac perfusing imaging data. The reference drawn from the comparison study includes: (1) ...
Fuel decomposition and boundary-layer combustion processes of hybrid rocket motors
Chiaverini, Martin J.; Harting, George C.; Lu, Yeu-Cherng; Kuo, Kenneth K.; Serin, Nadir; Johnson, David K.
1995-01-01
Using a high-pressure, two-dimensional hybrid motor, an experimental investigation was conducted on fundamental processes involved in hybrid rocket combustion. HTPB (Hydroxyl-terminated Polybutadiene) fuel cross-linked with diisocyanate was burned with GOX under various operating conditions. Large-amplitude pressure oscillations were encountered in earlier test runs. After identifying the source of instability and decoupling the GOX feed-line system and combustion chamber, the pressure oscillations were drastically reduced from +/-20% of the localized mean pressure to an acceptable range of +/-1.5% Embedded fine-wire thermocouples indicated that the surface temperature of the burning fuel was around 1000 K depending upon axial locations and operating conditions. Also, except near the leading-edge region, the subsurface thermal wave profiles in the upstream locations are thicker than those in the downstream locations since the solid-fuel regression rate, in general, increases with distance along the fuel slab. The recovered solid fuel slabs in the laminar portion of the boundary layer exhibited smooth surfaces, indicating the existence of a liquid melt layer on the burning fuel surface in the upstream region. After the transition section, which displayed distinct transverse striations, the surface roughness pattern became quite random and very pronounced in the downstream turbulent boundary-layer region. Both real-time X-ray radiography and ultrasonic pulse-echo techniques were used to determine the instantaneous web thickness burned and instantaneous solid-fuel regression rates over certain portions of the fuel slabs. Globally averaged and axially dependent but time-averaged regression rates were also obtained and presented.
Farhat, Charbel; Rixen, Daniel
1996-01-01
We present an optimal preconditioning algorithm that is equally applicable to the dual (FETI) and primal (Balancing) Schur complement domain decomposition methods, and which successfully addresses the problems of subdomain heterogeneities including the effects of large jumps of coefficients. The proposed preconditioner is derived from energy principles and embeds a new coarsening operator that propagates the error globally and accelerates convergence. The resulting iterative solver is illustrated with the solution of highly heterogeneous elasticity problems.
Rey, Valentine; Gosselet, Pierre
2013-01-01
This paper deals with the estimation of the distance between the solution of a static linear mechanic problem and its approximation by the finite element method solved with a non-overlapping domain decomposition method (FETI or BDD). We propose a new strict upper bound of the error which separates the contribution of the iterative solver and the contribution of the discretization. Numerical assessments show that the bound is sharp and enables us to define an objective stopping criterion for the iterative solver
Liu, Zhiwen; He, Zhengjia; Guo, Wei; Tang, Zhangchun
2016-03-01
In order to extract fault features of large-scale power equipment from strong background noise, a hybrid fault diagnosis method based on the second generation wavelet de-noising (SGWD) and the local mean decomposition (LMD) is proposed in this paper. In this method, a de-noising algorithm of second generation wavelet transform (SGWT) using neighboring coefficients was employed as the pretreatment to remove noise in rotating machinery vibration signals by virtue of its good effect in enhancing the signal-noise ratio (SNR). Then, the LMD method is used to decompose the de-noised signals into several product functions (PFs). The PF corresponding to the faulty feature signal is selected according to the correlation coefficients criterion. Finally, the frequency spectrum is analyzed by applying the FFT to the selected PF. The proposed method is applied to analyze the vibration signals collected from an experimental gearbox and a real locomotive rolling bearing. The results demonstrate that the proposed method has better performances such as high SNR and fast convergence speed than the normal LMD method.
Time-domain hybrid method for simulating large amplitude motions of ships advancing in waves
Directory of Open Access Journals (Sweden)
Shukui Liu
2011-03-01
Full Text Available Typical results obtained by a newly developed, nonlinear time domain hybrid method for simulating large amplitude motions of ships advancing with constant forward speed in waves are presented. The method is hybrid in the way of combining a time-domain transient Green function method and a Rankine source method. The present approach employs a simple double integration algorithm with respect to time to simulate the free-surface boundary condition. During the simulation, the diffraction and radiation forces are computed by pressure integration over the mean wetted surface, whereas the incident wave and hydrostatic restoring forces/moments are calculated on the instantaneously wetted surface of the hull. Typical numerical results of application of the method to the seakeeping performance of a standard containership, namely the ITTC S175, are herein presented. Comparisons have been made between the results from the present method, the frequency domain 3D panel method (NEWDRIFT of NTUA-SDL and available experimental data and good agreement has been observed for all studied cases between the results of the present method and comparable other data.
An Explicit Time-Domain Hybrid Formulation Based on the Unified Boundary Condition
Energy Technology Data Exchange (ETDEWEB)
Madsen, N; Fasenfest, B J; White, D; Stowell, M; Jandhyala, V; Pingenot, J; Champagne, N J; Rockway, J D
2007-02-28
An approach to stabilize the two-surface, time domain FEM/BI hybrid by means of a unified boundary condition is presented. The first-order symplectic finite element formulation [1] is used along with a version of the unified boundary condition of Jin [2] reformulated for Maxwell's first-order equations in time to provide both stability and accuracy over the first-order ABC. Several results are presented to validate the numerical solutions. In particular the dipole in a free-space box is analyzed and compared to the Dirchlet boundary condition of Ziolkowski and Madsen [3] and to a Neuman boundary condition approach.
Strain-controlled magnetic domain wall propagation in hybrid piezoelectric/ferromagnetic structures
Lei, Na; Devolder, Thibaut; Agnus, Guillaume; Aubert, Pascal; Daniel, Laurent; Kim, Joo-Von; Zhao, Weisheng; Trypiniotis, Theodossis; Cowburn, Russell P.; Chappert, Claude; Ravelosona, Dafiné; Lecoeur, Philippe
2013-01-01
The control of magnetic order in nanoscale devices underpins many proposals for integrating spintronics concepts into conventional electronics. A key challenge lies in finding an energy-efficient means of control, as power dissipation remains an important factor limiting future miniaturization of integrated circuits. One promising approach involves magnetoelectric coupling in magnetostrictive/piezoelectric systems, where induced strains can bear directly on the magnetic anisotropy. While such processes have been demonstrated in several multiferroic heterostructures, the incorporation of such complex materials into practical geometries has been lacking. Here we demonstrate the possibility of generating sizeable anisotropy changes, through induced strains driven by applied electric fields, in hybrid piezoelectric/spin-valve nanowires. By combining magneto-optical Kerr effect and magnetoresistance measurements, we show that domain wall propagation fields can be doubled under locally applied strains. These results highlight the prospect of constructing low-power domain wall gates for magnetic logic devices.
Zheng, Xiang
2015-03-01
We present a numerical algorithm for simulating the spinodal decomposition described by the three dimensional Cahn-Hilliard-Cook (CHC) equation, which is a fourth-order stochastic partial differential equation with a noise term. The equation is discretized in space and time based on a fully implicit, cell-centered finite difference scheme, with an adaptive time-stepping strategy designed to accelerate the progress to equilibrium. At each time step, a parallel Newton-Krylov-Schwarz algorithm is used to solve the nonlinear system. We discuss various numerical and computational challenges associated with the method. The numerical scheme is validated by a comparison with an explicit scheme of high accuracy (and unreasonably high cost). We present steady state solutions of the CHC equation in two and three dimensions. The effect of the thermal fluctuation on the spinodal decomposition process is studied. We show that the existence of the thermal fluctuation accelerates the spinodal decomposition process and that the final steady morphology is sensitive to the stochastic noise. We also show the evolution of the energies and statistical moments. In terms of the parallel performance, it is found that the implicit domain decomposition approach scales well on supercomputers with a large number of processors. © 2015 Elsevier Inc.
Model of hybrid interfacial domain wall in ferromagnetic/antiferromagnetic bilayers
Zhang, Wen; Zhai, Ya; Lu, Mu; You, Biao; Zhai, Hong-Ru; Caroline, G. Morgan
2015-04-01
A general model of a hybrid interfacial domain wall (HIDW) in ferromagnetic/antiferromagnetic exchange biased bilayers is proposed, where an interfacial domain wall is allowed to extend into either the ferromagnetic or antiferromagnetic layer or across both. The proposition is based on our theoretical investigation on thickness and field dependences of ferromagnetic domain wall (FMDW) and antiferromagnetic domain wall (AFDW), respectively. Good match of the simulation to the hysteresis loops of a series of NiFe/FeMn exchange-biased bilayers confirms the existence of the HIDW, where the AFDW part is found to preferentially occupy the entire antiferromagnetic layer while the FMDW shrinks with the increased magnetic field as expected. The observed asymmetry between the ascending and descending branches of the hysteresis loop is explained naturally as a consequence of different partition ratios between AFDW and FMDW. Project supported by the National Basic Research Program, China (Grant No. 2010CB923404), the National Natural Science Foundation for Young Scientists of China (Grant No. 61306121), and the China Postdoctoral Science Foundation (Grant No. 2013M541580).
Energy Technology Data Exchange (ETDEWEB)
Zhidkov, E.P.; Mazurkevich, G.E.; Khoromsky, B.N.
1989-01-01
A method of domain decomposition with cross-points (box decomposition) is used for the solution of finite-difference elliptic boundary value problems in rectangle and in parallelepiped. Capacitance matrix and preconditioners for iterative solution of arising algebraic problem are constructed by means of Poincare-Steklov operators. The convergence properties of iterative algorithms depend on local characteristics of subdomains on the number N'' of unknowns in one direction in subdomains, and are independent of the number of subdomains and of jumps of elliptic operator coefficients as long as these jumps only occur across the subdomain boundaries. The dependence of convergence on discretization of the problem is defined by ln N'' for two-dimensional problems, by {radical}N ln N'' for three-dimensional problems. The results of numerical experiments illustrating convergence properties are presented. 18 refs., 3 figs., 4 tabs.
Optimal metal domain size for photocatalysis with hybrid semiconductor-metal nanorods.
Ben-Shahar, Yuval; Scotognella, Francesco; Kriegel, Ilka; Moretti, Luca; Cerullo, Giulio; Rabani, Eran; Banin, Uri
2016-01-01
Semiconductor-metal hybrid nanostructures offer a highly controllable platform for light-induced charge separation, with direct relevance for their implementation in photocatalysis. Advances in the synthesis allow for control over the size, shape and morphology, providing tunability of the optical and electronic properties. A critical determining factor of the photocatalytic cycle is the metal domain characteristics and in particular its size, a subject that lacks deep understanding. Here, using a well-defined model system of cadmium sulfide-gold nanorods, we address the effect of the gold tip size on the photocatalytic function, including the charge transfer dynamics and hydrogen production efficiency. A combination of transient absorption, hydrogen evolution kinetics and theoretical modelling reveal a non-monotonic behaviour with size of the gold tip, leading to an optimal metal domain size for the most efficient photocatalysis. We show that this results from the size-dependent interplay of the metal domain charging, the relative band-alignments, and the resulting kinetics.
Energy Technology Data Exchange (ETDEWEB)
Zhao, W [Huazhong University of Science & Technology, Wuhan, Hubei (China); Niu, T [Zhejiang University, Hangzhou, Zhejiang (China); Xing, L [Stanford Univ School of Medicine, Stanford, CA (United States); Xiong, G; Elmore, K; Min, J [Dalio Institute of Cardiovascular Imaging NewYork-Presbyterian Hospital and, New York, NY (United States); Zhu, J; Wang, L [Huazhong University of Science and Technology, Wuhan, Hubei (China)
2015-06-15
Purpose: To significantly improve dual energy CT (DECT) imaging by establishing a new theoretical framework of image-domain material decomposition with incorporation of edge-preserving techniques. Methods: The proposed algorithm, HYPR-NLM, combines the edge-preserving non-local mean filter (NLM) with the HYPR-LR (Local HighlY constrained backPRojection Reconstruction) framework. Image denoising using HYPR-LR framework depends on the noise level of the composite image which is the average of the different energy images. For DECT, the composite image is the average of high- and low-energy images. To further reduce noise, one may want to increase the window size of the filter of the HYPR-LR, leading resolution degradation. By incorporating the NLM filtering and the HYPR-LR framework, HYPR-NLM reduces the boost material decomposition noise using energy information redundancies as well as the non-local mean. We demonstrate the noise reduction and resolution preservation of the algorithm with both iodine concentration numerical phantom and clinical patient data by comparing the HYPR-NLM algorithm to the direct matrix inversion, HYPR-LR and iterative image-domain material decomposition (Iter-DECT). Results: The results show iterative material decomposition method reduces noise to the lowest level and provides improved DECT images. HYPR-NLM significantly reduces noise while preserving the accuracy of quantitative measurement and resolution. For the iodine concentration numerical phantom, the averaged noise levels are about 2.0, 0.7, 0.2 and 0.4 for direct inversion, HYPR-LR, Iter- DECT and HYPR-NLM, respectively. For the patient data, the noise levels of the water images are about 0.36, 0.16, 0.12 and 0.13 for direct inversion, HYPR-LR, Iter-DECT and HYPR-NLM, respectively. Difference images of both HYPR-LR and Iter-DECT show edge effect, while no significant edge effect is shown for HYPR-NLM, suggesting spatial resolution is well preserved for HYPR-NLM. Conclusion: HYPR
Su, Xiao-Xing; Wang, Yue-Sheng; Zhang, Chuanzeng
2017-05-01
A time-domain method for calculating the defect states of scalar waves in two-dimensional (2D) periodic structures is proposed. In the time-stepping process of the proposed method, the column vector containing the spatially sampled field values is updated by multiplying it with an iteration matrix, which is written in a matrix-exponential form. The matrix-exponential is first computed by using the Suzuki's decomposition based technique of the fourth order, in which the Floquet-Bloch boundary conditions are incorporated. The obtained iteration matrix is then squared to enlarge the time-step that can be used in the time-stepping process (namely, the squaring technique), and the small nonzero elements in the iteration matrix is finally pruned to improve the sparse structure of the matrix (namely, the pruning technique). The numerical examples of the super-cell calculations for 2D defect-containing phononic crystal structures show that, the fourth order decomposition based technique for the matrix-exponential computation is much more efficient than the frequently used precise integration technique (PIT) if the PIT is of an order greater than 2. Although it is not unconditionally stable, the proposed time-domain method is particularly efficient for the super-cell calculations of the defect states in a 2D periodic structure containing a defect with a wave speed much higher than those of the background materials. For this kind of defect-containing structures, the time-stepping process can run stably for a sufficiently large number of the time-steps with a time-step much larger than the Courant-Friedrichs-Lewy (CFL) upper limit, and consequently the overall efficiency of the proposed time-domain method can be significantly higher than that of the conventional finite-difference time-domain (FDTD) method. Some physical interpretations on the properties of the band structures and the defect states of the calculated periodic structures are also presented.
Energy Technology Data Exchange (ETDEWEB)
T.F. Eibert; J.L. Volakis; Y.E. Erdemli
2002-03-03
Hybrid finite element (FE)--boundary integral (BI) analysis of infinite periodic arrays is extended to include planar multilayered Green's functions. In this manner, a portion of the volumetric dielectric region can be modeled via the finite element method whereas uniform multilayered regions can be modeled using a multilayered Green's function. As such, thick uniform substrates can be modeled without loss of efficiency and accuracy. The multilayered Green's function is analytically computed in the spectral domain and the resulting BI matrix-vector products are evaluated via the fast spectral domain algorithm (FSDA). As a result, the computational cost of the matrix-vector products is kept at O(N). Furthermore, the number of Floquet modes in the expansion are kept very few by placing the BI surfaces within the computational unit cell. Examples of frequency selective surface (FSS) arrays are analyzed with this method to demonstrate the accuracy and capability of the approach. One example involves complicated multilayered substrates above and below an inhomogeneous filter element and the other is an optical ring-slot array on a substrate several hundred wavelengths in thickness. Comparisons with measurements are included.
Energy Technology Data Exchange (ETDEWEB)
Sidler, Rolf, E-mail: rsidler@gmail.com [Center for Research of the Terrestrial Environment, University of Lausanne, CH-1015 Lausanne (Switzerland); Carcione, José M. [Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Borgo Grotta Gigante 42c, 34010 Sgonico, Trieste (Italy); Holliger, Klaus [Center for Research of the Terrestrial Environment, University of Lausanne, CH-1015 Lausanne (Switzerland)
2013-02-15
We present a novel numerical approach for the comprehensive, flexible, and accurate simulation of poro-elastic wave propagation in 2D polar coordinates. An important application of this method and its extensions will be the modeling of complex seismic wave phenomena in fluid-filled boreholes, which represents a major, and as of yet largely unresolved, computational problem in exploration geophysics. In view of this, we consider a numerical mesh, which can be arbitrarily heterogeneous, consisting of two or more concentric rings representing the fluid in the center and the surrounding porous medium. The spatial discretization is based on a Chebyshev expansion in the radial direction and a Fourier expansion in the azimuthal direction and a Runge–Kutta integration scheme for the time evolution. A domain decomposition method is used to match the fluid–solid boundary conditions based on the method of characteristics. This multi-domain approach allows for significant reductions of the number of grid points in the azimuthal direction for the inner grid domain and thus for corresponding increases of the time step and enhancements of computational efficiency. The viability and accuracy of the proposed method has been rigorously tested and verified through comparisons with analytical solutions as well as with the results obtained with a corresponding, previously published, and independently benchmarked solution for 2D Cartesian coordinates. Finally, the proposed numerical solution also satisfies the reciprocity theorem, which indicates that the inherent singularity associated with the origin of the polar coordinate system is adequately handled.
Yi, Xi; Wang, Xin; Chen, Weiting; Wan, Wenbo; Zhao, Huijuan; Gao, Feng
2014-05-01
The common approach to diffuse optical tomography is to solve a nonlinear and ill-posed inverse problem using a linearized iteration process that involves repeated use of the forward and inverse solvers on an appropriately discretized domain of interest. This scheme normally brings severe computation and storage burdens to its applications on large-sized tissues, such as breast tumor diagnosis and brain functional imaging, and prevents from using the matrix-fashioned linear inversions for improved image quality. To cope with the difficulties, we propose in this paper a parallelized full domain-decomposition scheme, which divides the whole domain into several overlapped subdomains and solves the corresponding subinversions independently within the framework of the Schwarz-type iterations, with the support of a combined multicore CPU and multithread graphics processing unit (GPU) parallelization strategy. The numerical and phantom experiments both demonstrate that the proposed method can effectively reduce the computation time and memory occupation for the large-sized problem and improve the quantitative performance of the reconstruction.
Lorin, E.; Yang, X.; Antoine, X.
2016-06-01
The paper is devoted to develop efficient domain decomposition methods for the linear Schrödinger equation beyond the semiclassical regime, which does not carry a small enough rescaled Planck constant for asymptotic methods (e.g. geometric optics) to produce a good accuracy, but which is too computationally expensive if direct methods (e.g. finite difference) are applied. This belongs to the category of computing middle-frequency wave propagation, where neither asymptotic nor direct methods can be directly used with both efficiency and accuracy. Motivated by recent works of the authors on absorbing boundary conditions (Antoine et al. (2014) [13] and Yang and Zhang (2014) [43]), we introduce Semiclassical Schwarz Waveform Relaxation methods (SSWR), which are seamless integrations of semiclassical approximation to Schwarz Waveform Relaxation methods. Two versions are proposed respectively based on Herman-Kluk propagation and geometric optics, and we prove the convergence and provide numerical evidence of efficiency and accuracy of these methods.
Aagaard, Brad T; Williams, Charles A
2013-01-01
We employ a domain decomposition approach with Lagrange multipliers to implement fault slip in a finite-element code, PyLith, for use in both quasi-static and dynamic crustal deformation applications. This integrated approach to solving both quasi-static and dynamic simulations leverages common finite-element data structures and implementations of various boundary conditions, discretization schemes, and bulk and fault rheologies. We have developed a custom preconditioner for the Lagrange multiplier portion of the system of equations that provides excellent scalability with problem size compared to conventional additive Schwarz methods. We demonstrate application of this approach using benchmarks for both quasi-static viscoelastic deformation and dynamic spontaneous rupture propagation that verify the numerical implementation in PyLith.
A HYBRID TECHNIQUE FOR FREQUENCY DOMAIN IDENTIFICATION OF SERVO SYSTEM WITH FRICTION FORCE
Directory of Open Access Journals (Sweden)
SHAIK.RAFI KIRAN,
2011-03-01
Full Text Available The system identification process in servo system with frictional force seems to be a complex task becauseof its non-linear nature. For such non-linear systems, a good choice is system identification in frequencydomain. However, most of the techniques are manual and are inappropriate for determination of systemparameters. This makes system identification ineffective for servo systems with frictional force. Toovercome this issue, a hybrid technique is proposed in this paper. The proposed technique exploits neuralnetwork and genetic algorithm to determine the system parameters of servo systems with friction. In theproposed technique, the target parameters are determined from the transfer function derived for thesystem. Subsequently, the system parameters are identified by a process formed by blending the neuralnetwork and genetic algorithm techniques. Prior to performing the identification procedure, backpropagation training is given to the neural network using a pre-examined dataset. Then with thecombined operation of neural network and genetic algorithm, the system parameters that are closer tothe target parameters for the servo system with frictional force are determined. The technique isimplemented and compared with the existing frequency domain identification technique. From thecomparative results, it is evident that the proposed technique outperforms the existing technique.
Indian Academy of Sciences (India)
Mohamed Haiour; Salah Boulaaras
2011-11-01
In this paper we provide a maximum norm analysis of an overlapping Schwarz method on non-matching grids for quasi-variational inequalities related to impulse control problem with mixed boundary conditions. We provide that the discretization on every sub-domain converges in uniform norm. Furthermore, a result of approximation in uniform norm is given.
Karlova, R.B.; Weemen, W.M.J.; Naimov, S.; Ceron, J.; Dukiandjiev, S.; Maagd, de R.A.
2005-01-01
We investigated the role of domain III of Bacillus thuringiensis d-endotoxin Cry1Ac in determining toxicity against Heliothis virescens. Hybrid toxins, containing domain III of Cry1Ac with domains I and II of Cry1Ba, Cry1Ca, Cry1Da, Cry1Ea, and Cry1Fb, respectively, were created. In this way Cry1Ca,
Tiwari, S. P.; Kumar, K.; Rai, V. K.
2015-06-01
Hybrid nano-composite phosphor has been successfully synthesized through thermal decomposition method. The dual phase of samples assigned by XRD analysis shows the formation of nano-composite with crystallite size 20 nm and 12 nm for YPO4: Tm/Yb and Fe3O4@YPO4:Tm/Yb respectively. The FESEM images show the spherical shape and non agglomerated formation of nanoparticles. Three bands in upconversion emission mode were found in intense blue at 472 nm, red at 662 nm and NIR at 798 nm regions corresponding to1G4 → 3H6, 1G4 → 3F4 and 3H4 → 3H6 transition states respectively. The lifetime for1G4 → 3H6 level is found 1150 microsecond and 1400 microsecond for YPO4: Tm/Yb and Fe3O4@YPO4:Tm/Yb samples respectively.
Kuo, Kenneth K.; Lu, Yeu-Cherng; Chiaverini, Martin J.; Johnson, David K.; Serin, Nadir; Risha, Grant A.; Merkle, Charles L.; Venkateswaran, Sankaran
1996-01-01
This final report summarizes the major findings on the subject of 'Fundamental Phenomena on Fuel Decomposition and Boundary-Layer Combustion Processes with Applications to Hybrid Rocket Motors', performed from 1 April 1994 to 30 June 1996. Both experimental results from Task 1 and theoretical/numerical results from Task 2 are reported here in two parts. Part 1 covers the experimental work performed and describes the test facility setup, data reduction techniques employed, and results of the test firings, including effects of operating conditions and fuel additives on solid fuel regression rate and thermal profiles of the condensed phase. Part 2 concerns the theoretical/numerical work. It covers physical modeling of the combustion processes including gas/surface coupling, and radiation effect on regression rate. The numerical solution of the flowfield structure and condensed phase regression behavior are presented. Experimental data from the test firings were used for numerical model validation.
Zhang, Lin-Fei; Zhang, Chun-Yang
2014-01-01
Ultrathin nanosheets possess novel electronic structures and physical properties as compared with their corresponding bulk samples. However, the controlled synthesis of ultrathin monolayer nanosheets still remains a great challenge due to the lack of an intrinsic driving force for anisotropic growth of two-dimensional (2D) structures. Here we demonstrate, for the first time to our knowledge, the in situ synthesis of large-scale ultrathin single-crystalline Co0.85Se nanosheets on graphene oxide (GO) sheets, with a thickness of 3 nm. Owing to the synergetic chemical coupling effects between GO and Co0.85Se, the Co0.85Se/graphene hybrid nanosheets exhibit the highest catalytic performance among the available cobalt chalcogenide-based catalysts for the oxygen reduction reaction (ORR). Moreover, Co0.85Se/graphene hybrid nanosheets can catalyze the decomposition of hydrazine hydrate rapidly, with 97% of hydrazine hydrate being degraded in 12 min and the degradation rate remaining constant over 10 consecutive cycles, thus having great potential as long-term catalysts in wastewater treatment.Ultrathin nanosheets possess novel electronic structures and physical properties as compared with their corresponding bulk samples. However, the controlled synthesis of ultrathin monolayer nanosheets still remains a great challenge due to the lack of an intrinsic driving force for anisotropic growth of two-dimensional (2D) structures. Here we demonstrate, for the first time to our knowledge, the in situ synthesis of large-scale ultrathin single-crystalline Co0.85Se nanosheets on graphene oxide (GO) sheets, with a thickness of 3 nm. Owing to the synergetic chemical coupling effects between GO and Co0.85Se, the Co0.85Se/graphene hybrid nanosheets exhibit the highest catalytic performance among the available cobalt chalcogenide-based catalysts for the oxygen reduction reaction (ORR). Moreover, Co0.85Se/graphene hybrid nanosheets can catalyze the decomposition of hydrazine hydrate rapidly
Xue, Kai; Serohijos, Raquel C; Devare, Medha; Thies, Janice E
2011-02-01
Despite the rapid adoption of crops expressing the insecticidal Cry protein(s) from Bacillus thuringiensis (Bt), public concern continues to mount over the potential environmental impacts. Reduced residue decomposition rates and increased tissue lignin concentrations reported for some Bt corn hybrids have been highlighted recently as they may influence soil carbon dynamics. We assessed the effects of MON863 Bt corn, producing the Cry3Bb protein against the corn rootworm complex, on these aspects and associated decomposer communities by terminal restriction fragment length polymorphism (T-RFLP) analysis. Litterbags containing cobs, roots, or stalks plus leaves from Bt and unmodified corn with (non-Bt+I) or without (non-Bt) insecticide applied were placed on the soil surface and at a 10-cm depth in field plots planted with these crop treatments. The litterbags were recovered and analyzed after 3.5, 15.5, and 25 months. No significant effect of treatment (Bt, non-Bt, and non-Bt+I) was observed on initial tissue lignin concentrations, litter decomposition rate, or bacterial decomposer communities. The effect of treatment on fungal decomposer communities was minor, with only 1 of 16 comparisons yielding separation by treatment. Environmental factors (litterbag recovery year, litterbag placement, and plot history) led to significant differences for most measured variables. Combined, these results indicate that the differences detected were driven primarily by environmental factors rather than by any differences between the corn hybrids or the use of tefluthrin. We conclude that the Cry3Bb corn tested in this study is unlikely to affect carbon residence time or turnover in soils receiving these crop residues.
Oil spill characterization in the hybrid polarity SAR domain using log-cumulants
Espeseth, Martine M.; Skrunes, Stine; Brekke, Camilla; Salberg, Arnt-Børre; Jones, Cathleen E.; Holt, Benjamin
2016-10-01
Log-cumulants have proven to be an interesting tool for evaluating the statistical properties of potential oil spills in polarimetric Synthetic Aperture Radar (SAR) data within the common horizontal (H) and vertical (V) polarization basis. The use of first, second, and third order sample log-cumulants has shown potential for evaluating the texture and the statistical distributions, as well as discriminating oil from look-alikes. Log-cumulants are cumulants derived in the log-domain and can be applied to both single-polarization and multipolarization SAR data. This study is the first to investigate the differences between hybrid-polarity (HP) and full-polarimetric (FP) modes based on the sample log-cumulants of various oil slicks and open water from nine Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) scenes acquired off the coast of Norway in 2015. The sample log-cumulants calculated from the HP intensities show similar statistical behavior to the FP ones, resulting in a similar interpretation of the sample log-cumulants from HP and FP. Approximately eight hours after release the sample log-cumulants representing emulsion slicks have become more similar to the open water compared to plant oil. We find that the sample log-cumulants of the various oil slicks and open water varies between the scenes and also between the slicks and open water. This might be due to changes in ocean and wind condition, the initial slick properties, and/or the difference in the weathering process of the oil slicks.
Terzopoulou, Zoe; Bikiaris, Dimitrios N.; Triantafyllidis, Konstantinos S.; Potsi, Georgia; Gournis, Dimitrios; Papageorgiou, George Z.; Rudolf, Petra
2016-01-01
Poly(epsilon-caprolactone) (PCL) nanocomposites with hybrid clay-supported carbon nanotubes (Clay-CNT) in concentrations 0.5, 1.0 and 2.5 wt% were prepared by melt mixing. Mechanical, structural and thermal properties of the nanocomposites were studied. All nanocomposites exhibited similar stress-st
Terzopoulou, Zoe; Bikiaris, Dimitrios N.; Triantafyllidis, Konstantinos S.; Potsi, Georgia; Gournis, Dimitrios; Papageorgiou, George Z.; Rudolf, Petra
2016-01-01
Poly(epsilon-caprolactone) (PCL) nanocomposites with hybrid clay-supported carbon nanotubes (Clay-CNT) in concentrations 0.5, 1.0 and 2.5 wt% were prepared by melt mixing. Mechanical, structural and thermal properties of the nanocomposites were studied. All nanocomposites exhibited similar
Provasi, Davide; Murcia, Marta; Coller, Barry S; Filizola, Marta
2009-11-01
The beta3 integrin family members alphaIIbeta3 and alphaVbeta3 signal bidirectionally through long-range allosteric changes, including a transition from a bent unliganded-closed low-affinity state to an extended liganded-open high-affinity state. To obtain an atomic-level description of this transition in an explicit solvent, we carried out targeted molecular dynamics simulations of the headpieces of alphaIIbeta3 and alphaVbeta3 integrins. Although minor differences were observed between these receptors, our results suggest a common transition pathway in which the hybrid domain swing-out is accompanied by conformational changes within the beta3 betaA (I-like) domain that propagate through the alpha7 helix C-terminus, and are followed by the alpha7 helix downward motion and the opening of the beta6-alpha7 loop. Breaking of contact interactions between the beta6-alpha7 loop and the alpha1 helix N-terminus results in helix straightening, internal rearrangements of the specificity determining loop (SDL), movement of the beta1-alpha1 loop toward the metal ion dependent adhesion site (MIDAS), and final changes at the interfaces between the beta3 betaA (I-like) domain and either the hybrid or the alpha beta-propeller domains. Taken together, our results suggest novel testable hypotheses of intradomain and interdomain interactions responsible for beta3 integrin activation.
Direct observation of charged domain walls in hybrid improper ferroelectric (Ca,Sr)3Ti2O7
Kurushima, Kousuke; Yoshimoto, Wataru; Ishii, Yui; Cheong, Sang-Wook; Mori, Shigeo
2017-10-01
We investigated ferroelectric (FE) domain wall structures including “charged domain walls” of hybrid improper FE (Ca,Sr)3Ti2O7 at the subatomic resolution by dark-field transmission electron microscopy (TEM) and high-resolution state-of-the-art aberration-corrected high-angle annular-dark-field (HAADF) scanning transmission electron microscopy (STEM). Dark-field TEM and high-resolution HAADF-STEM images obtained in the FE phase of single crystals of Ca2.46Sr0.54Ti2O7 revealed the formation of abundant charged domain walls with the head-to-head and tail-to-tail configurations in the FE domain structure, in addition to the FE 180° domain structure. The charged domain walls with the head-to-head and tail-to-tail FE polarizations exist stably and can be characterized as the unique double arc-type displacement of Ca/Sr ions in a unit cell without charge accumulation.
A hybrid domain analysis for systems with delays in state and control
Directory of Open Access Journals (Sweden)
Razzaghi M.
2001-01-01
Full Text Available The solution of time-delay systems is obtained by using a hybrid function. The properties of the hybrid functions consisting of block-pulse functions and Chebyshev polynomials are presented. The method is based upon expanding various time functions in the system as their truncated hybrid functions. The operational matrix of delay is introduced. The operational matrices of integration and delay are utilized to reduce the solution of time-delay systems to the solution of algebraic equations. Illustrative examples are included to demonstrate the validity and applicability of the technique.
Ervik, Åsmund; Müller, Bernhard
2014-01-01
To leverage the last two decades' transition in High-Performance Computing (HPC) towards clusters of compute nodes bound together with fast interconnects, a modern scalable CFD code must be able to efficiently distribute work amongst several nodes using the Message Passing Interface (MPI). MPI can enable very large simulations running on very large clusters, but it is necessary that the bulk of the CFD code be written with MPI in mind, an obstacle to parallelizing an existing serial code. In this work we present the results of extending an existing two-phase 3D Navier-Stokes solver, which was completely serial, to a parallel execution model using MPI. The 3D Navier-Stokes equations for two immiscible incompressible fluids are solved by the continuum surface force method, while the location of the interface is determined by the level-set method. We employ the Portable Extensible Toolkit for Scientific Computing (PETSc) for domain decomposition (DD) in a framework where only a fraction of the code needs to be a...
DEFF Research Database (Denmark)
Jensen, Jonas Kjær; Ommen, Torben Schmidt; Markussen, Wiebke Brix
2014-01-01
The ammonia-water hybrid absorption-compression heat pump (HACHP) is a relevant technology for industrial heat supply, especially for high sink temperatures and high temperature glides in the sink and source. This is due to the reduced vapour pressure and the non-isothermal phase change...... of the zeotropic mixture, ammonia-water. To evaluate to which extent these advantages can be translated into feasible heat pump solutions, the working domain of the HACHP is investigated based on technical and economic constraints. The HACHP working domain is compared to that of the best possible vapour...... compression heat pump with natural working fluids. This shows that the HACHP increases the temperature lifts and heat supply temperatures that are feasible to produce with a heat pump. The HACHP is shown to be capable of delivering heat supply temperatures as high as 140 XC and temperature lifts up to 60 K...
DEFF Research Database (Denmark)
Jensen, Jonas Kjær; Ommen, Torben Schmidt; Markussen, Wiebke Brix
2015-01-01
The ammonia-water hybrid absorption-compression heat pump (HACHP) has been proposed as a relevant technology for industrial heat supply, especially for high sink temperatures and high temperature glides in the sink and source. This is due to the reduced vapour pressure and the non-isothermal phase...... change of the zeotropic mixture, ammonia-water. To evaluate to which extent these advantages can be translated into feasible heat pump solutions, the working domain of the HACHP is investigated based on technical and economic constraints. The HACHP working domain is compared to that of the best available...... vapour compression heat pump with natural working fluids. This shows that the HACHP increases the temperature lifts and heat supply temperatures that are feasible to produce with a heat pump. The HACHP is shown to be capable of delivering heat supply temperatures as high as 150 °C and temperature lifts...
Rank-based decompositions of morphological templates.
Sussner, P; Ritter, G X
2000-01-01
Methods for matrix decomposition have found numerous applications in image processing, in particular for the problem of template decomposition. Since existing matrix decomposition techniques are mainly concerned with the linear domain, we consider it timely to investigate matrix decomposition techniques in the nonlinear domain with applications in image processing. The mathematical basis for these investigations is the new theory of rank within minimax algebra. Thus far, only minimax decompositions of rank 1 and rank 2 matrices into outer product expansions are known to the image processing community. We derive a heuristic algorithm for the decomposition of matrices having arbitrary rank.
Institute of Scientific and Technical Information of China (English)
Shao Wei; Qian Zuping; Yuan Feng
2007-01-01
A robust phase-only Direct Data Domain Least Squares (D3LS) algorithm based on generalized Rayleigh quotient optimization using hybrid Genetic Algorithm (GA) is presented in this letter. The optimization efficiency and computational speed are improved via the hybrid GA composed of standard GA and Nelder-Mead simplex algorithms. First, the objective function, with a form of generalized Rayleigh quotient, is derived via the standard D3LS algorithm. It is then taken as a fitness function and the unknown phases of all adaptive weights are taken as decision variables.Then, the nonlinear optimization is performed via the hybrid GA to obtain the optimized solution of phase-only adaptive weights. As a phase-only adaptive algorithm, the proposed algorithm is simpler than conventional algorithms when it comes to hardware implementation. Moreover, it processes only a single snapshot data as opposed to forming sample covariance matrix and operating matrix inversion. Simulation results show that the proposed algorithm has a good signal recovery and interferences nulling performance, which are superior to that of the phase-only D3LS algorithm based on standard GA.
Energy Technology Data Exchange (ETDEWEB)
Barbey, Carole, E-mail: carole.barbey@smbh.univ-paris13.fr [Laboratoire de Biophysique Moléculaire, Cellulaire et Tissulaire, UMR 7033, Université Paris 13, UFR SMBH, 74 Rue Marcel Cachin, 93017 Bobigny CEDEX (France); Rouhier, Nicolas [Unité Mixte de Recherches 1136 INRA UHP (Interaction Arbres Microorganismes), IFR 110, Nancy Université BP 239, 54506 Vandoeuvre-lès-Nancy CEDEX (France); Haouz, Ahmed [Plate-forme de Cristallogenèse et Diffraction des Rayons X, Institut Pasteur, 25 Rue du Dr Roux, 75724 Paris (France); Navaza, Alda [Laboratoire de Biophysique Moléculaire, Cellulaire et Tissulaire, UMR 7033, Université Paris 13, UFR SMBH, 74 Rue Marcel Cachin, 93017 Bobigny CEDEX (France); Jacquot, Jean-Pierre [Unité Mixte de Recherches 1136 INRA UHP (Interaction Arbres Microorganismes), IFR 110, Nancy Université BP 239, 54506 Vandoeuvre-lès-Nancy CEDEX (France); Laboratoire de Biophysique Moléculaire, Cellulaire et Tissulaire, UMR 7033, Université Paris 13, UFR SMBH, 74 Rue Marcel Cachin, 93017 Bobigny CEDEX (France)
2008-01-01
Crystals of the peroxiredoxin domain of a larger natural hybrid protein from T. maritima were obtained which diffracted to 2.9 Å resolution on a synchrotron source. Thermotoga maritima contains a natural hybrid protein constituted of two moieties: a peroxiredoxin domain at the N-terminus and a nitroreductase domain at the C-terminus. The peroxiredoxin (Prx) domain has been overproduced and purified from Escherichia coli cells. The recombinant Prx domain, which is homologous to bacterial Prx BCP and plant Prx Q, folds properly into a stable protein that possesses biological activity. The recombinant protein was crystallized and synchrotron data were collected to 2.9 Å resolution. The crystals belonged to the tetragonal space group I422, with unit-cell parameters a = b = 176.67, c = 141.20 Å.
Directory of Open Access Journals (Sweden)
Jingjing Yu
2013-01-01
Full Text Available Quantitative reconstruction of bioluminescent sources from boundary measurements is a challenging ill-posed inverse problem owing to the high degree of absorption and scattering of light through tissue. We present a hybrid multilevel reconstruction scheme by combining the ability of sparse regularization with the advantage of adaptive finite element method. In view of the characteristics of different discretization levels, two different inversion algorithms are employed on the initial coarse mesh and the succeeding ones to strike a balance between stability and efficiency. Numerical experiment results with a digital mouse model demonstrate that the proposed scheme can accurately localize and quantify source distribution while maintaining reconstruction stability and computational economy. The effectiveness of this hybrid reconstruction scheme is further confirmed with in vivo experiments.
Solving Problems in Various Domains by Hybrid Models of High Performance Computations
Directory of Open Access Journals (Sweden)
Yurii Rogozhin
2014-03-01
Full Text Available This work presents a hybrid model of high performance computations. The model is based on membrane system (P~system where some membranes may contain quantum device that is triggered by the data entering the membrane. This model is supposed to take advantages of both biomolecular and quantum paradigms and to overcome some of their inherent limitations. The proposed approach is demonstrated through two selected problems: SAT, and image retrieving.
Institute of Scientific and Technical Information of China (English)
Chun LiaoChong Feng∗Sen Yang; He-Yan Huang
2016-01-01
Opinion targets extraction of Chinese microblogs plays an important role in opinion mining. There has been a significant progress in this area recently, especially the method based on conditional random field (CRF). However, this method only takes lexicon-related features into consideration and does not excavate the implied syntactic and semantic knowledge. We propose a novel approach which incorporates domain lexicon with groups of syntactical and semantic features. The approach acquires domain lexicon through a novel way which explores syntactic and semantic information through Part-of-Speech, dependency structure, phrase structure, semantic role and semantic similarity based on word embedding. And then we combine the domain lexicon with opinion targets extracted from CRF with groups of features for opinion targets extraction. Experimental results on COAE2014 dataset show the outperformance of the approach compared with other well-known methods on the task of opinion targets extraction.
Efficient Mooring Line Fatigue Analysis Using a Hybrid Method Time Domain Simulation Scheme
DEFF Research Database (Denmark)
Christiansen, Niels Hørbye; Voie, Per Erlend Torbergsen; Høgsberg, Jan Becker;
2013-01-01
Dynamic analyses of mooring line systems are computationally expensive. Over the last decades an extensive variety of methods to reduce this computational cost have been suggested. One method that has shown promising preliminary results is a hybrid method which combines finite element analysis...... and slow drift motion. The method is tested on a mooring line system of a floating offshore platform. After training a full fatigue analysis is carried out. The results show that the ANN with high precision provides top tension force histories two orders of magnitude faster than a full dynamic analysis...
Ebrahimi, Farideh; Setarehdan, Seyed-Kamaledin; Ayala-Moyeda, Jose; Nazeran, Homer
2013-10-01
The conventional method for sleep staging is to analyze polysomnograms (PSGs) recorded in a sleep lab. The electroencephalogram (EEG) is one of the most important signals in PSGs but recording and analysis of this signal presents a number of technical challenges, especially at home. Instead, electrocardiograms (ECGs) are much easier to record and may offer an attractive alternative for home sleep monitoring. The heart rate variability (HRV) signal proves suitable for automatic sleep staging. Thirty PSGs from the Sleep Heart Health Study (SHHS) database were used. Three feature sets were extracted from 5- and 0.5-min HRV segments: time-domain features, nonlinear-dynamics features and time-frequency features. The latter was achieved by using empirical mode decomposition (EMD) and discrete wavelet transform (DWT) methods. Normalized energies in important frequency bands of HRV signals were computed using time-frequency methods. ANOVA and t-test were used for statistical evaluations. Automatic sleep staging was based on HRV signal features. The ANOVA followed by a post hoc Bonferroni was used for individual feature assessment. Most features were beneficial for sleep staging. A t-test was used to compare the means of extracted features in 5- and 0.5-min HRV segments. The results showed that the extracted features means were statistically similar for a small number of features. A separability measure showed that time-frequency features, especially EMD features, had larger separation than others. There was not a sizable difference in separability of linear features between 5- and 0.5-min HRV segments but separability of nonlinear features, especially EMD features, decreased in 0.5-min HRV segments. HRV signal features were classified by linear discriminant (LD) and quadratic discriminant (QD) methods. Classification results based on features from 5-min segments surpassed those obtained from 0.5-min segments. The best result was obtained from features using 5-min HRV
Orbital Hybridization of the Ferroelectric Rb2Cd2 (SO4)3: Origin of Domain Walls
Institute of Scientific and Technical Information of China (English)
DUAN Yi-Feng; YI Lin
2005-01-01
@@ We perform first-principle calculations for the study of the orthorhombic Rb2Cd2 (SO4)3 structure. Electronic energy bands, total and partial densities of states are reported and analysed. It is found that oxygen atomic 2p electrons strongly hybridize with Rb/or Cd 4d and S 2p states, resulting in two-type ionic groups with weak couplings. It is shown that macroscopic domain walls originate from such weak-coupling ionic groups, arising at the cell boundaries. The asymmetric cation bonds (Rb-O and Cd-O) and the subsequent rotations of the SO4tetrahedra can lead to the driving force of the ferroelectric behaviour. The predicted pyroelectric current effects are observed experimentally in the ferroelectric phase.
Directory of Open Access Journals (Sweden)
Si-Da Zhou
2015-01-01
Full Text Available Real-time estimation of modal parameters of time-varying structures can conduct an obvious contribution to some specific applications in structural dynamic area, such as health monitoring, damage detection, and vibration control; the recursive algorithm of modal parameter estimation supplies one of fundamentals for acquiring modal parameters in real-time. This paper presents a vector multistage recursive method of modal parameter estimation for time-varying structures in hybrid time and frequency domain, including stages of recursive estimation of time-dependent power spectra, frozen-time modal parameter estimation, recursive modal validation, and continuous-time estimation of modal parameters. An experimental example validates the proposed method finally.
Yu, You; Li, Yinan; Zhang, Yan
2016-04-01
Alzheimer's disease (AD) is a neurodegenerative disorder in which amyloid β plaques are a pathological characteristic. Little is known about the physiological functions of amyloid β precursor protein (APP). Based on its structure as a type I transmembrane protein, it has been proposed that APP might be a receptor, but so far, no ligand has been reported. In the present study, 9 proteins binding to the extracellular domain of APP were identified using a yeast two-hybrid system. After confirming the interactions in the mammalian system, mutated PLP1, members of the FLRT protein family, and KCTD16 were shown to interact with APP. These proteins have been reported to be involved in Pelizaeus-Merzbacher disease (PMD) and axon guidance. Therefore, our results shed light on the mechanisms of physiological function of APP in AD, PMD, and axon guidance.
Prakash, K Soorya; Raj, M Joseph Malvin
2010-01-01
In this paper, research on AI based modeling technique to optimize development of new alloys with necessitated improvements in properties and chemical mixture over existing alloys as per functional requirements of product is done. The current research work novels AI in lieu of predictions to establish association between material and product customary. Advanced computational simulation techniques like CFD, FEA interrogations are made viable to authenticate product dynamics in context to experimental investigations. Accordingly, the current research is focused towards binding relationships between material design and product design domains. The input to feed forward back propagation prediction network model constitutes of material design features. Parameters relevant to product design strategies are furnished as target outputs. The outcomes of ANN shows good sign of correlation between material and product design domains. The study enriches a new path to illustrate material factors at the time of new product d...
Directory of Open Access Journals (Sweden)
Agoritsa Konstanti
2013-10-01
Full Text Available Normal 0 false false false MicrosoftInternetExplorer4 In the present work, a hybrid educational methodology has been developed for approaching the cognitive domain of Built Heritage Protection in an interdisciplinary and integrated way. This domain was selected as a pilot one, presenting various remarkable characteristics, such as bringing together STEM subjects with social and human sciences, proving concrete concepts, being attractive for youth, and demanding combination of technical solutions with social aspects. The methodology had the scope to interconnect secondary with tertiary level education for the achievement of the best possible results, as the latter possesses the needed specialised knowledge, expertise and infrastructure. The methodology incorporates problem - based learning, aiming at the effective solution of real and extremely complex problems encountered in monument scale, which is combined with traditional teaching methods, such as lectures, as well as contemporary elements, such as class exercise laboratory experiments, in situ field work, promoting hands - on experience of students. The pilot application and evaluation of the hybrid methodology proved to be a valuable experience for students of secondary level education, which needs to be further exploited and optimised in order to meet the expectations of the interested parties. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"????????? ???????"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;}
Does hybridization increase evolutionary rate? Data from the 28S-rDNA D8 domain in echinoderms.
Chenuil, Anne; Egea, Emilie; Rocher, Caroline; Touzet, Hélène; Féral, Jean-Pierre
2008-11-01
The divergent domain D8 of the large ribosomal RNA is very variable and extended in vertebrates compared to other eukaryotes. We provide data from 31 species of echinoderms and present the first comparative analysis of the D8 in nonvertebrate deuterostomes. In addition, we obtained 16S mitochondrial DNA sequences for the sea urchin taxa and analyzed single-strand conformation polymorphism (SSCP) of D8 in several populations within the species complex Echinocardium cordatum. A common secondary structure supported by compensatory substitutions and indels is inferred for echinoderms. Variation mostly arises at the tip of the longest stem (D8a), and the most variable taxa also display the longest and most stable D8. The most stable variants are the only ones displaying bulges in the terminal part of the stem, suggesting that selection, rather than maximizing stability of the D8 secondary structure, maintains it in a given range. Striking variation in D8 evolutionary rates was evidenced among sea urchins, by comparison with both 16S mitochondrial DNA and paleontological data. In Echinocardium cordatum and Strongylocentrotus pallidus and S. droebachiensis, belonging to very distant genera, the increase in D8 evolutionary rate is extreme. Their highly stable D8 secondary structures rule out the possibility of pseudogenes. These taxa are the only ones in which interspecific hybridization was reported. We discuss how evolutionary rates may be affected in nuclear relative to mitochondrial genes after hybridization, by selective or mutational processes such as gene silencing and concerted evolution.
Energy Technology Data Exchange (ETDEWEB)
Hu, Zi-Yu [College of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Computational Science Research Center, Beijing 100084 (China); Shao, Xiaohong, E-mail: shaoxh@mail.buct.edu.cn, E-mail: limin.liu@csrc.ac.cn [College of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Wang, Da; Liu, Li-Min, E-mail: shaoxh@mail.buct.edu.cn, E-mail: limin.liu@csrc.ac.cn [Beijing Computational Science Research Center, Beijing 100084 (China); Johnson, J. Karl [Departments of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261 (United States)
2014-08-28
First-principles calculations are performed to investigate the adsorption of hydrogen onto Li-decorated hybrid boron nitride and graphene domains of (BN){sub x}C{sub 1−x} complexes with x = 1, 0.25, 0.5, 0.75, 0, and B{sub 0.125}C{sub 0.875}. The most stable adsorption sites for the nth hydrogen molecule in the lithium-decorated (BN){sub x}C{sub 1−x} complexes are systematically discussed. The most stable adsorption sites were affected by the charge localization, and the hydrogen molecules were favorably located above the C-C bonds beside the Li atom. The results show that the nitrogen atoms in the substrate planes could increase the hybridization between the 2p orbitals of Li and the orbitals of H{sub 2}. The results revealed that the (BN){sub x}C{sub 1−x} complexes not only have good thermal stability but they also exhibit a high hydrogen storage of 8.7% because of their dehydrogenation ability.
Dalton, Jutta C; Bätz, Ulrike; Liu, Jason; Curie, Gemma L; Quail, Peter H
2016-01-01
Transcriptional activation domains (TADs) are difficult to predict and identify, since they are not conserved and have little consensus. Here, we describe a yeast-based screening method that is able to identify individual amino acid residues involved in transcriptional activation in a high throughput manner. A plant transcriptional activator, PIF3 (phytochrome interacting factor 3), was fused to the yeast GAL4-DNA-binding Domain (BD), driving expression of the URA3 (Orotidine 5'-phosphate decarboxylase) reporter, and used for negative selection on 5-fluroorotic acid (5FOA). Randomly mutagenized variants of PIF3 were then selected for a loss or reduction in transcriptional activation activity by survival on FOA. In the process, we developed a strategy to eliminate false positives from negative selection that can be used for both reverse-1- and 2-hybrid screens. With this method we were able to identify two distinct regions in PIF3 with transcriptional activation activity, both of which are functionally conserved in PIF1, PIF4, and PIF5. Both are collectively necessary for full PIF3 transcriptional activity, but neither is sufficient to induce transcription autonomously. We also found that the TAD appear to overlap physically with other PIF3 functions, such as phyB binding activity and consequent phosphorylation. Our protocol should provide a valuable tool for identifying, analyzing and characterizing novel TADs in eukaryotic transcription factors, and thus potentially contribute to the unraveling of the mechanism underlying transcriptional activation.
Dalton, Jutta C.; Bätz, Ulrike; Liu, Jason; Curie, Gemma L.; Quail, Peter H.
2016-01-01
Transcriptional activation domains (TADs) are difficult to predict and identify, since they are not conserved and have little consensus. Here, we describe a yeast-based screening method that is able to identify individual amino acid residues involved in transcriptional activation in a high throughput manner. A plant transcriptional activator, PIF3 (phytochrome interacting factor 3), was fused to the yeast GAL4-DNA-binding Domain (BD), driving expression of the URA3 (Orotidine 5′-phosphate decarboxylase) reporter, and used for negative selection on 5-fluroorotic acid (5FOA). Randomly mutagenized variants of PIF3 were then selected for a loss or reduction in transcriptional activation activity by survival on FOA. In the process, we developed a strategy to eliminate false positives from negative selection that can be used for both reverse-1- and 2-hybrid screens. With this method we were able to identify two distinct regions in PIF3 with transcriptional activation activity, both of which are functionally conserved in PIF1, PIF4, and PIF5. Both are collectively necessary for full PIF3 transcriptional activity, but neither is sufficient to induce transcription autonomously. We also found that the TAD appear to overlap physically with other PIF3 functions, such as phyB binding activity and consequent phosphorylation. Our protocol should provide a valuable tool for identifying, analyzing and characterizing novel TADs in eukaryotic transcription factors, and thus potentially contribute to the unraveling of the mechanism underlying transcriptional activation. PMID:27379152
Optimized Mooring Line Simulation Using a Hybrid Method Time Domain Scheme
DEFF Research Database (Denmark)
Christiansen, Niels Hørbye; Voie, Per Erlend Torbergsen; Høgsberg, Jan;
2014-01-01
of mooring lines by two orders of magnitude. The present study shows how an ANN trained to perform nonlinear dynamic response simulation can be optimized using a method known as optimal brain damage (OBD) and thereby be used to rank the importance of all analysis input. Both the training and the optimization...... of the ANN are based on one short time domain simulation sequence generated by a FEM model of the structure. This means that it is possible to evaluate the importance of input parameters based on this single simulation only. The method is tested on a numerical model of mooring lines on a floating offshore...
A hybrid method of estimating pulsating flow parameters in the space-time domain
Pałczyński, Tomasz
2017-05-01
This paper presents a method for estimating pulsating flow parameters in partially open pipes, such as pipelines, internal combustion engine inlets, exhaust pipes and piston compressors. The procedure is based on the method of characteristics, and employs a combination of measurements and simulations. An experimental test rig is described, which enables pressure, temperature and mass flow rate to be measured within a defined cross section. The second part of the paper discusses the main assumptions of a simulation algorithm elaborated in the Matlab/Simulink environment. The simulation results are shown as 3D plots in the space-time domain, and compared with proposed models of phenomena relating to wave propagation, boundary conditions, acoustics and fluid mechanics. The simulation results are finally compared with acoustic phenomena, with an emphasis on the identification of resonant frequencies.
Speeding-up the hybrid video watermarking techniques in the DWT domain
Chammem, A.; Mitrea, M.; Preteux, F.
2010-01-01
The watermarking state of the art exhibits the hybrid methods combining spread spectrum and side information principles. The present study is focussed on speeding up such an algorithm (jointly patented by SFR - Vodafone Group and Institut Telecom). The dead lock on the reference method is first identified: the embedding module accounts for 90% of the whole watermarking chain and that more than 99% of this time is spent on applying an attack procedure (required in order to grant a good robustness to this method). The main issue of the present study is to deploy Monte Carlo generators accurately representing the watermarking attacks. In this respect, two difficulties should be overcome. First, accurate statistical models for the watermarking attacks should be obtained. Secondly, efficient Monte Carlo simulators should be deployed for these models. The last part of the study was devoted to the experimental validations. The mark is inserted in the (9,7) DWT representation of video sequence. Several types of attacks have been considered (linear and non-linear filters, geometrical transformations, ...). The quantitative results proved that the data payload, transparency and robustness properties have been inherited from the reference method. However, the watermarking speed was increased by a factor of 80.
Chlorogenic acid-arabinose hybrid domains in coffee melanoidins: Evidences from a model system.
Moreira, Ana S P; Coimbra, Manuel A; Nunes, Fernando M; Passos, Cláudia P; Santos, Sónia A O; Silvestre, Armando J D; Silva, André M N; Rangel, Maria; Domingues, M Rosário M
2015-10-15
Arabinose from arabinogalactan side chains was hypothesized as a possible binding site for chlorogenic acids in coffee melanoidins. To investigate this hypothesis, a mixture of 5-O-caffeoylquinic acid (5-CQA), the most abundant chlorogenic acid in green coffee beans, and (α1 → 5)-L-arabinotriose, structurally related to arabinogalactan side chains, was submitted to dry thermal treatments. The compounds formed during thermal processing were identified by electrospray ionization mass spectrometry (ESI-MS) and characterized by tandem MS (ESI-MS(n)). Compounds composed by one or two CQAs covalently linked with pentose (Pent) residues (1-12) were identified, along with compounds bearing a sugar moiety but composed exclusively by the quinic or caffeic acid moiety of CQAs. The presence of isomers was demonstrated by liquid chromatography online coupled to ESI-MS and ESI-MS(n). Pent1-2CQA were identified in coffee samples. These results give evidence for a diversity of chlorogenic acid-arabinose hybrids formed during roasting, opening new perspectives for their identification in melanoidin structures.
Pan, Xiaoyong; Shen, Hong-Bin
2017-02-28
RNAs play key roles in cells through the interactions with proteins known as the RNA-binding proteins (RBP) and their binding motifs enable crucial understanding of the post-transcriptional regulation of RNAs. How the RBPs correctly recognize the target RNAs and why they bind specific positions is still far from clear. Machine learning-based algorithms are widely acknowledged to be capable of speeding up this process. Although many automatic tools have been developed to predict the RNA-protein binding sites from the rapidly growing multi-resource data, e.g. sequence, structure, their domain specific features and formats have posed significant computational challenges. One of current difficulties is that the cross-source shared common knowledge is at a higher abstraction level beyond the observed data, resulting in a low efficiency of direct integration of observed data across domains. The other difficulty is how to interpret the prediction results. Existing approaches tend to terminate after outputting the potential discrete binding sites on the sequences, but how to assemble them into the meaningful binding motifs is a topic worth of further investigation. In viewing of these challenges, we propose a deep learning-based framework (iDeep) by using a novel hybrid convolutional neural network and deep belief network to predict the RBP interaction sites and motifs on RNAs. This new protocol is featured by transforming the original observed data into a high-level abstraction feature space using multiple layers of learning blocks, where the shared representations across different domains are integrated. To validate our iDeep method, we performed experiments on 31 large-scale CLIP-seq datasets, and our results show that by integrating multiple sources of data, the average AUC can be improved by 8% compared to the best single-source-based predictor; and through cross-domain knowledge integration at an abstraction level, it outperforms the state-of-the-art predictors by 6
Directory of Open Access Journals (Sweden)
Batakliev Todor
2014-06-01
Full Text Available Catalytic ozone decomposition is of great significance because ozone is a toxic substance commonly found or generated in human environments (aircraft cabins, offices with photocopiers, laser printers, sterilizers. Considerable work has been done on ozone decomposition reported in the literature. This review provides a comprehensive summary of the literature, concentrating on analysis of the physico-chemical properties, synthesis and catalytic decomposition of ozone. This is supplemented by a review on kinetics and catalyst characterization which ties together the previously reported results. Noble metals and oxides of transition metals have been found to be the most active substances for ozone decomposition. The high price of precious metals stimulated the use of metal oxide catalysts and particularly the catalysts based on manganese oxide. It has been determined that the kinetics of ozone decomposition is of first order importance. A mechanism of the reaction of catalytic ozone decomposition is discussed, based on detailed spectroscopic investigations of the catalytic surface, showing the existence of peroxide and superoxide surface intermediates
TAL nucleases (TALNs): hybrid proteins composed of TAL effectors and FokI DNA-cleavage domain.
Li, Ting; Huang, Sheng; Jiang, Wen Zhi; Wright, David; Spalding, Martin H; Weeks, Donald P; Yang, Bing
2011-01-01
DNA double-strand breaks enhance homologous recombination in cells and have been exploited for targeted genome editing through use of engineered endonucleases. Here we report the creation and initial characterization of a group of rare-cutting, site-specific DNA nucleases produced by fusion of the restriction enzyme FokI endonuclease domain (FN) with the high-specificity DNA-binding domains of AvrXa7 and PthXo1. AvrXa7 and PthXo1 are members of the transcription activator-like (TAL) effector family whose central repeat units dictate target DNA recognition and can be modularly constructed to create novel DNA specificity. The hybrid FN-AvrXa7, AvrXa7-FN and PthXo1-FN proteins retain both recognition specificity for their target DNA (a 26 bp sequence for AvrXa7 and 24 bp for PthXo1) and the double-stranded DNA cleaving activity of FokI and, thus, are called TAL nucleases (TALNs). With all three TALNs, DNA is cleaved adjacent to the TAL-binding site under optimal conditions in vitro. When expressed in yeast, the TALNs promote DNA homologous recombination of a LacZ gene containing paired AvrXa7 or asymmetric AvrXa7/PthXo1 target sequences. Our results demonstrate the feasibility of creating a tool box of novel TALNs with potential for targeted genome modification in organisms lacking facile mechanisms for targeted gene knockout and homologous recombination.
Jensen, Sacha A; Iqbal, Sarah; Lowe, Edward D; Redfield, Christina; Handford, Penny A
2009-05-13
The fibrillins and latent transforming growth factor-beta binding proteins (LTBPs) form a superfamily of structurally-related proteins consisting of calcium-binding epidermal growth factor-like (cbEGF) domains interspersed with 8-cysteine-containing transforming growth factor beta-binding protein-like (TB) and hybrid (hyb) domains. Fibrillins are the major components of the extracellular 10-12 nm diameter microfibrils, which mediate a variety of cell-matrix interactions. Here we present the crystal structure of a fibrillin-1 cbEGF9-hyb2-cbEGF10 fragment, solved to 1.8 A resolution. The hybrid domain fold is similar, but not identical, to the TB domain fold seen in previous fibrillin-1 and LTBP-1 fragments. Pairwise interactions with neighboring cbEGF domains demonstrate extensive interfaces, with the hyb2-cbEGF10 interface dependent on Ca(2+) binding. These observations provide accurate constraints for models of fibrillin organization within the 10-12 nm microfibrils and provide further molecular insights into how Ca(2+) binding influences the intermolecular interactions and biomechanical properties of fibrillin-1.
Directory of Open Access Journals (Sweden)
Wen Hwa Lee
Full Text Available Agonist-stimulated platelet activation triggers conformational changes of integrin αIIbβ3, allowing fibrinogen binding and platelet aggregation. We have previously shown that an octapeptide, p1YMESRADR8, corresponding to amino acids 313-320 of the β-ribbon extending from the β-propeller domain of αIIb, acts as a potent inhibitor of platelet aggregation. Here we have performed in silico modelling analysis of the interaction of this peptide with αIIbβ3 in its bent and closed (not swing-out conformation and show that the peptide is able to act as a substitute for the β-ribbon by forming a clasp restraining the β3 hybrid and βI domains in a closed conformation. The involvement of species-specific residues of the β3 hybrid domain (E356 and K384 and the β1 domain (E297 as well as an intrapeptide bond (pE315-pR317 were confirmed as important for this interaction by mutagenesis studies of αIIbβ3 expressed in CHO cells and native or substituted peptide inhibitory studies on platelet functions. Furthermore, NMR data corroborate the above results. Our findings provide insight into the important functional role of the αIIb β-ribbon in preventing integrin αIIbβ3 head piece opening, and highlight a potential new therapeutic approach to prevent integrin ligand binding.
Institute of Scientific and Technical Information of China (English)
杜其奎; 余德浩
2001-01-01
Some new domain decomposition methods based on natural boundary reduction are suggested for overlapping and non-overlapping domains. A two-dimensional scalar wave equation is taken as a model to illustrate these methods. The governing equation is discretized in time, leading to time-stepping scheme, where an exterior elliptic problem has to be solved in each time step. The Dirichlet-Neumann method and Schwartz alternating method are proposed respectively. For the Schwartz alternating method, the convergence of the algorithm and the contraction factor for exterior circular domain are given. Finally, some numerical examples are devoted to illustrate these methods.%提出了无界区域波动方程的区域分解算法.基于自然边界归化,分别研究了重叠型与非重叠型区域分解算法.首先将控制方程对时间进行离散化,得到关于时间步长离散化格式,对每一时间步长给出了Dirichlet-Neumann和Schwartz交替算法.对Schwartz交替算法,给出了算法的收敛性,对圆外区域研究了压缩因子,并给出了数值例子.
Decomposition of semigroup algebras
Boehm, Janko; Nitsche, Max Joachim
2011-01-01
Let A \\subseteq B be cancellative abelian semigroups, and let R be an integral domain. We show that the semigroup ring R[B] can be decomposed, as an R[A]-module, into a direct sum of R[A]-submodules of the quotient ring of R[A]. In the case of a finite extension of positive affine semigroup rings we obtain an algorithm computing the decomposition. When R[A] is a polynomial ring over a field we explain how to compute many ring-theoretic properties of R[B] in terms of this decomposition. In particular we obtain a fast algorithm to compute the Castelnuovo-Mumford regularity of homogeneous semigroup rings. As an application we confirm the Eisenbud-Goto conjecture in a range of new cases. Our algorithms are implemented in the Macaulay2 package MonomialAlgebras.
Institute of Scientific and Technical Information of China (English)
施建宇; 张艳宁
2012-01-01
The classification of structural domain is one of important approaches which contribute to explore the mechanism of folding and the relationship of protein structure and its biological function. First, this paper mapped spatial structure of protein domain into Ca-Ca distance matrix which could be further regarded as gray texture image. Next,it modeled two distance functions for a helix and 0 strand/sheet by considering their geometrical properties, and used to find their gray patterns in distance matrix image respectively. After that, it applied the techniques of spatial template match and pyramid decomposition to present the composition feature of a helix and ^8 strand and the multi-scale topology feature of ^3 sheet respectively. Furthermore, in terms of the hierarchy of structural classification of proteins( SCOP) , performed domain classifications on structural class and fold levels respectively and compared with other methods. Finally, the results of domain classification show that the proposed method achieves the accuracies 90.1% and 74. 6% in the first validation strategy, and 93. 8% and 78. 7% in the second validation strategy respectively. The comparison with other methods validates the presented method can perform domain classification effectively and outperform its competitors with both the higher classified accuracy and the more compacted dimension of feature vector.%首先构造结构域的距离矩阵灰度图像；其次建立典型二级结构的距离函数,并分析所呈现的灰度模式；然后基于模板匹配和塔式分解,提出了结构域特征；最后在结构类和折叠子两个层次实施结构域分类.本方法在第一种验证策略的分类精度分别为90.7％和74.6％,使用第二种验证策略的为93.8％和78.7％.相比其他方法,具有更高分类精度和更低的特征维教,说明本方法更有效.
Institute of Scientific and Technical Information of China (English)
鲍伟; 马继涛
2013-01-01
奇异值分解(SVD)是提高信噪比的一种较新的有效手段之一.本文从数学角度阐述了奇异值分解SVD滤波技术增强地震资料信噪比的原理,对比了时间域和频率域SVD技术压制随机噪声的处理效果.结果表明,时间域SVD技术只能对水平或接近水平的同相轴进行信号增强,对倾斜同相轴的处理效果较差;而频率域SVD技术既可以处理水平同相轴,也可以处理倾斜同相轴,对提高地震剖面信噪比具有很好的效果.本文用3个简单的合成地震记录和1个实际地震资料检验了SVD两种方法的应用效果.结果表明,本文方法可以达到随机噪声压制的效果.%Singular Value Decomposition (SVD) is a new and effective method for random noise suppression.The principle of the SVD filtering technique,which enhances the signal to noise ratio of seismic data,is illustrated.Then,by applying time-domain and frequency-domain SVD techniques to suppress random noise generated from a variety of seismic model data,their processing results are compared with each other.The results indicate that the time-domain SVD technique is only able to enhance fiat or near flat events.When encountering dip events,it is less effective.However,the frequency-domain SVD technique is able to enhance both flat and dip events,and improve the signal to noise ratio of seismic profile.Three simple synthetic seismograms and one real seismic data are used,and the practical effects of these two SVD methods are verified.The results show that the frequency-domain SVD is effective for suppressing the random noise.
Energy Technology Data Exchange (ETDEWEB)
Ullah, Kefayat; Ye, Shu; Zhu, Lei; Meng, Ze-Da; Sarkar, Sourav; Oh, Won-Chun, E-mail: wc_oh@hanseo.ac.kr
2014-02-15
Highlights: • Pt/graphene nanocomposites were synthesized via facile, fast, and scalable microwave irradiation method. • MB and Rh.B were used as sample dye solutions. • The Pt/graphene nanocomposites displayed distinctly enhanced photocatalytic activities. • UV–vis spectroscopic analysis was carried out to measure decomposition effect. -- Abstract: We report fast and facile synthesis of Pt/graphene nanocomposite via microwave assisted techniques. The “as-prepared” composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), UV–vis absorbance spectra analysis, diffuse reflectance spectra (DRS) analysis and Raman spectroscopic analysis. The visible light photo catalytic activities of Pt/graphene nanocomposite were tested by rhodamine B (Rh.B) and methylene blue (MB) as a standard model dyes. These analysis provide a promising development toward graphene based high efficient photocatalyst under visible light as an energy source.
DEFF Research Database (Denmark)
Dyson, Mark
2003-01-01
This PhD is based on constructing and resolving a set of modular problems. Each problem exists as a separate entity. Each has its own characteristics, yet when combined with other, related problems, provides a dimension to a story. The relationships and order between problems has priority over....... Not only have design tools changed character, but also the processes associated with them. Today, the composition of problems and their decomposition into parcels of information, calls for a new paradigm. This paradigm builds on the networking of agents and specialisations, and the paths of communication...... that are necessary to make sense out of any design situation. The hypothesis of this project, is that Design organisation, communication and CAD-information processes must be jointly reengineered to create the dynamic structures needed for the forward projection of design knowledge into this expanding Design network....
Directory of Open Access Journals (Sweden)
Ming Cheng
Full Text Available Structural and functional analyses of integrin αIIbβ3 has implicated swing-out motion of the β3 hybrid domain in αIIbβ3 activation and ligand binding. Using data from targeted molecular dynamics (TMD simulations, we engineered two disulfide-bonded mutant receptors designed to limit swing-out (XS-O. XS-O mutants cannot bind the high Mr ligand fibrinogen in the presence of an activating mAb or after introducing mutations into the αIIb subunit designed to simulate inside-out signaling. They also have reduced capacity to be "primed" to bind fibrinogen by pretreatment with eptifibatide. They can, however, bind the small RGD venom protein kistrin. Despite their inability to bind soluble fibrinogen, the XS-O mutants can support adhesion to immobilized fibrinogen, although such adhesion does not initiate outside-in signaling leading to normal cytoskeletal reorganization. Collectively, our data further define the biologic role of β3 hybrid domain swing-out in both soluble and immobilized high Mr ligand binding, as well as in priming and outside-in signaling. We also infer that swing-out is likely to be a downstream effect of receptor extension.
Kogan, Simon
2011-01-01
DHoPLLS (http://leah.haifa.ac.il/~skogan/Apache/mydata1/main.html) is a web server that identifies closed loops, which constitute a structural basis for the protein domain hierarchy. The server was created in 2005 year on basis Prof. Trifonov's lab in Genome Diversity Center, Institute of Evolution at University of Haifa. It is based on theory of loop-lock structure developed by Prof. Trifonov's group in Weizmann Institute of Science. This theory declares that all globular protein can be decomposed on set of almost closed loop with mean length about 30 aminoacids. The lock is a place, where a loop meets itself. Investigations of Trifonov's group demonstrates that some aminoacid's sequences (about 30 aminoacids) are usually exists in proteins in form of closed loops. On basis computer programs, developed for the server, we checked the simplest assumption that most of closed loop or locks in proteins have some alphabet of consensus sequences. Unfortunately our results demonstrate that such alphabet doesn't exis...
Institute of Scientific and Technical Information of China (English)
王彤; 张令弥
2006-01-01
提出了一种基于频域空间域分解(Frequency and Spatial Domain Decomposition,FSDD)的运行模态分析方法.该法将同时具有输入和输出的试验模态分析的经典方法--复模态指示因子(Complex Mode Indicator Function,CMIF)法拓展到了仅有输出响应的运行状态模态分析.FSDD法采用奇异值分解将信号空间和噪声空间分离开来,把奇异值曲线作为模态指示的依据,以奇异值向量作为加权函数得到每一阶模态的增强功率谱(Power Spectrum Density,PSD),进而在频域内对增强PSD曲线进行最小二乘拟合以得到准确的模态频率和阻尼参数.采用了一个二层楼仿真算例和在欧洲广为人知的瑞士Z24公路大桥实测算例来验证FSDD算法.
Institute of Scientific and Technical Information of China (English)
王跃; 吕林; 朱雨薇
2016-01-01
为风电场配置合适的储能系统可以平抑风电有功功率波动、提高系统电能质量。基于风电出力历史数据，提出了双层功率分解方法。第1层采用滑动平均法，在满足国家规定的风电并网要求下，分解出并网功率和混合储能系统的参考功率。第2层采用频谱分析方法，基于混合储能系统参考功率，利用傅里叶变换将其分解为低频分量和高频分量，分别分配给蓄电池和超级电容器吸收。考虑储能设备的荷电状态和蓄电池的循环使用寿命，建立混合储能系统容量配置模型，模型以其年综合成本最小为优化目标。仿真结果验证了双层功率分解方法的可行性，证明了混合储能系统较单类型储能系统在性能上和经济上的优越性。%Suitable energy storage can be configured for the wind power plant to stabilize the fluctuations of wind power and improve the power quality of wind power. Based on the historical data of wind power output, this paper proposes a double layer power decomposition method. The first layer adopts moving average method to decompose the power of the grid-connected power and hybrid energy storage system, according to the wind power grid connected indicators in China. The second layer uses spectrum analysis method and Fourier transform to decompose the reference power of hybrid energy storage system into low frequency component and high frequency component, which are distributed to the battery and the super capacitor, respectively. Considering the state of charge of energy storage equipment and the cycle life of the battery, this paper establishes the capacity optimization model of the hybrid energy storage system, which takes the minimum annual comprehensive cost as the optimization goal. The simulation results verify the feasibility of the double layer power decomposition method, and prove that the hybrid energy storage system is superior to the single type energy
Energy Technology Data Exchange (ETDEWEB)
Pingenot, J; Jandhyala, V
2007-03-01
This report summarizes the work performed for Lawrence Livermore National Laboratory (LLNL) at the University of Washington between September 2004 and May 2006. This project studied fast solvers and stability for time domain integral equations (TDIE), especially as applied to radiating boundary for a massively parallel FEM solver.
Barati, Shahram; Chegini, Fariba; Hurtado, Plinio; Rush, Robert A
2002-09-01
To study the mechanism by which genes can efficiently be transferred into specific cell types, we have constructed several novel, single-chain multicomponent proteins by recombining the nontoxic C fragment of tetanus toxin and the translocation domain of diphtheria toxin together with the DNA-binding fragment of GAL4 transcription factor, for transportation of plasmid DNA into neuronal cells. The C fragment of tetanus toxin provided neuronal selectivity, the translocation domain of diphtheria toxin permitted endosomal escape, and the GAL4 domain provided binding to DNA. To assess the cellular tasks of each component in gene transfer, different combinations of these fragments were produced by polymerase chain reaction, expressed in Escherichia coli, and purified under native conditions from the soluble proteins. We show that only fusion proteins bearing the C fragment of tetanus toxin bind to gangliosides and, followed by their specific binding to differentiated PC12 cells, are internalized within 10 min. These proteins delivered the green fluorescence protein gene to PC12 cells, with the highest transfection efficiency achieved with proteins containing both the C fragment and the translocation domain. Addition of chloroquine elevated the transfection efficiency, which was further increased by incorporation of a nuclear localization signal in the delivery system. In addition, the effect of different DNA-condensing materials (poly-L-lysine, protamine, lysine(n=8)-trytophan(n=2)-lysine(n=8)) on gene transfer was investigated.
Application of a hybrid kinetic-continuum solver to the near wall modelling
Rovenskaya, O.; Croce, G.
2014-11-01
A hybrid method dynamically coupling the direct numerical solution of the S-model kinetic equation and Navier-Stokes equations is applied to a numerical simulation of the flow through the channel of a finite length due to arbitrarily pressure ratios and for a wide range of Knudsen number. The decomposition of the physical domain into kinetic and hydrodynamic sub-domains is updated at each time step. The solution is advanced in time simultaneously in both kinetic and hydrodynamic domains: the coupling is achieved by matching half fluxes at the interface of the kinetic and Navier-Stokes domains, thus taking care of the conservation of momentum, energy and mass through the interface. Solver efficiency is increased via MPI (Message Passing Interface) parallelization. Accuracy and reliability of the method, for different decomposition criteria, are assessed via comparison with a pure kinetic solution.
Cheng, Kyle H Y; Standish, Beau A; Yang, Victor X D; Cheung, K K Y; Gu, Xijia; Lam, Edmund Y; Wong, K K Y
2010-02-01
We report the first Fourier domain modelocked (FDML) laser constructed using optical parametric amplifier (OPA) in conjunction with an erbium-doped fiber amplifier (EDFA), centered at approximately 1555 nm, to the best of our knowledge. We utilize a one-pump OPA and a C-band EDFA in serial configuration with a tunable Fabry-Perot interferometer to generate a hybrid FDML spectrum. Results demonstrate a substantially better spectral shape, output power and stability than individual configurations, with decreased sensitivity to polarization changes. We believe this technique has the potential to enable several amplifiers to complement individual deficiencies resulting in improved spectral shapes and power generation for imaging applications such as optical coherence tomography (OCT).
Mode decomposition evolution equations.
Wang, Yang; Wei, Guo-Wei; Yang, Siyang
2012-03-01
Partial differential equation (PDE) based methods have become some of the most powerful tools for exploring the fundamental problems in signal processing, image processing, computer vision, machine vision and artificial intelligence in the past two decades. The advantages of PDE based approaches are that they can be made fully automatic, robust for the analysis of images, videos and high dimensional data. A fundamental question is whether one can use PDEs to perform all the basic tasks in the image processing. If one can devise PDEs to perform full-scale mode decomposition for signals and images, the modes thus generated would be very useful for secondary processing to meet the needs in various types of signal and image processing. Despite of great progress in PDE based image analysis in the past two decades, the basic roles of PDEs in image/signal analysis are only limited to PDE based low-pass filters, and their applications to noise removal, edge detection, segmentation, etc. At present, it is not clear how to construct PDE based methods for full-scale mode decomposition. The above-mentioned limitation of most current PDE based image/signal processing methods is addressed in the proposed work, in which we introduce a family of mode decomposition evolution equations (MoDEEs) for a vast variety of applications. The MoDEEs are constructed as an extension of a PDE based high-pass filter (Europhys. Lett., 59(6): 814, 2002) by using arbitrarily high order PDE based low-pass filters introduced by Wei (IEEE Signal Process. Lett., 6(7): 165, 1999). The use of arbitrarily high order PDEs is essential to the frequency localization in the mode decomposition. Similar to the wavelet transform, the present MoDEEs have a controllable time-frequency localization and allow a perfect reconstruction of the original function. Therefore, the MoDEE operation is also called a PDE transform. However, modes generated from the present approach are in the spatial or time domain and can be
Gonnet, Pedro
2014-01-01
This paper describes a new fast and implicitly parallel approach to neighbour-finding in multi-resolution Smoothed Particle Hydrodynamics (SPH) simulations. This new approach is based on hierarchical cell decompositions and sorted interactions, within a task-based formulation. It is shown to be faster than traditional tree-based codes, and to scale better than domain decomposition-based approaches on hybrid shared/distributed-memory parallel architectures, e.g. clusters of multi-cores, achieving a $40\\times$ speedup over the Gadget-2 simulation code.
Alexandrakis, G; Farrell, T J; Patterson, M S
2000-05-01
We propose a hybrid Monte Carlo (MC) diffusion model for calculating the spatially resolved reflectance amplitude and phase delay resulting from an intensity-modulated pencil beam vertically incident on a two-layer turbid medium. The model combines the accuracy of MC at radial distances near the incident beam with the computational efficiency afforded by a diffusion calculation at further distances. This results in a single forward calculation several hundred times faster than pure MC, depending primarily on model parameters. Model predictions are compared with MC data for two cases that span the extremes of physiologically relevant optical properties: skin overlying fat and skin overlying muscle, both in the presence of an exogenous absorber. It is shown that good agreement can be achieved for radial distances from 0.5 to 20 mm in both cases. However, in the skin-on-muscle case the choice of model parameters and the definition of the diffusion coefficient can lead to some interesting discrepancies.
Damping Estimation by Frequency Domain Decomposition
DEFF Research Database (Denmark)
Brincker, Rune; Ventura, C. E.; Andersen, P.
2001-01-01
frequencies can be accurately estimated without being limited by the frequency resolution of the discrete Fourier transform. It is explained how the spectral density matrix is decomposed into a set of single degree of freedom systems, and how the individual SDOF auto spectral density functions are transformed...
Chura-Chambi, Rosa Maria; Arcuri, Helen Andrade; Lino, Felipe; Versati, Natan; Palma, Mario Sergio; Favaro, Denize C; Morganti, Ligia
2017-05-01
Endostatin (ES) is an antiangiogenic protein that exhibits antitumor activity in animal models. However, the activity observed in animals was not observed in human clinical trials. ES-BAX is a fusion protein composed of two functional domains: ES, which presents specificity and is internalized by activated endothelial cells and the proapoptotic BH3 domain of the protein BAX, a peptide inductor of cellular death when internalized. We have previously shown (Chura-Chambi et al., Cell Death Dis, 5, e1371, 2014) that ES-BAX presents improved antitumor activity in relation to wild-type ES. Secondary and tertiary structures of ES-BAX are similar to ES, as indicated by homology-modeling studies and molecular dynamics simulations. Tryptophan intrinsic fluorescence and circular dichroism spectroscopy corroborate these data. (15) N HSQC NMR indicates that ES-BAX is structured, but some ES residues have suffered chemical shift perturbations, suggesting that the BH3 peptide interacts with some parts of the ES protein. ES and ES-BAX present similar stability to thermal denaturation. The production of stable hybrid proteins can be a new approach to the development of therapeutic agents presenting specificity for tumoral endothelium and improved antitumor effect. © 2016 International Union of Biochemistry and Molecular Biology, Inc.
Jongruja, Nujarin; You, Dong-Ju; Kanaya, Eiko; Koga, Yuichi; Takano, Kazufumi; Kanaya, Shigenori
2010-11-01
Thermotoga maritima ribonuclease H (RNase H) I (Tma-RNase HI) contains a hybrid binding domain (HBD) at the N-terminal region. To analyze the role of this HBD, Tma-RNase HI, Tma-W22A with the single mutation at the HBD, the C-terminal RNase H domain (Tma-CD) and the N-terminal domain containing the HBD (Tma-ND) were overproduced in Escherichia coli, purified and biochemically characterized. Tma-RNase HI prefers Mg(2+) to Mn(2+) for activity, and specifically loses most of the Mg(2+)-dependent activity on removal of the HBD and 87% of it by the mutation at the HBD. Tma-CD lost the ability to suppress the RNase H deficiency of an E. coli rnhA mutant, indicating that the HBD is responsible for in vivo RNase H activity. The cleavage-site specificities of Tma-RNase HI are not significantly changed on removal of the HBD, regardless of the metal cofactor. Binding analyses of the proteins to the substrate using surface plasmon resonance indicate that the binding affinity of Tma-RNase HI is greatly reduced on removal of the HBD or the mutation. These results indicate that there is a correlation between Mg(2+)-dependent activity and substrate binding affinity. Tma-CD was as stable as Tma-RNase HI, indicating that the HBD is not important for stability. The HBD of Tma-RNase HI is important not only for substrate binding, but also for Mg(2+)-dependent activity, probably because the HBD affects the interaction between the substrate and enzyme at the active site, such that the scissile phosphate group of the substrate and the Mg(2+) ion are arranged ideally.
2013-01-01
The main goal of this book is to provide a state of the art of hybrid metaheuristics. The book provides a complete background that enables readers to design and implement hybrid metaheuristics to solve complex optimization problems (continuous/discrete, mono-objective/multi-objective, optimization under uncertainty) in a diverse range of application domains. Readers learn to solve large scale problems quickly and efficiently combining metaheuristics with complementary metaheuristics, mathematical programming, constraint programming and machine learning. Numerous real-world examples of problems and solutions demonstrate how hybrid metaheuristics are applied in such fields as networks, logistics and transportation, bio-medical, engineering design, scheduling.
Hybrid Parallel Programming Models for AMR Neutron Monte-Carlo Transport
Dureau, David; Poëtte, Gaël
2014-06-01
This paper deals with High Performance Computing (HPC) applied to neutron transport theory on complex geometries, thanks to both an Adaptive Mesh Refinement (AMR) algorithm and a Monte-Carlo (MC) solver. Several Parallelism models are presented and analyzed in this context, among them shared memory and distributed memory ones such as Domain Replication and Domain Decomposition, together with Hybrid strategies. The study is illustrated by weak and strong scalability tests on complex benchmarks on several thousands of cores thanks to the petaflopic supercomputer Tera100.
Martin, R.; Gonzalez Ortiz, A.
momentum exchange forces and the interphase heat exchanges are 1 treated implicitly to ensure stability. In order to reduce one more time the computa- tional cost, a decomposition of the global domain in N subdomains is introduced and all the previous algorithms applied to one block is performed in each block. At the in- terface between subdomains, an overlapping procedure is used. Another advantage is that different sets of equations can be solved in each block like fluid/structure interac- tions for instance. We show here the hydrodynamics of a two-phase flow in a vertical conduct as in industrial plants of fluid catalytical cracking processes with a complex geometry. With an initial Richardson number of 0.16 slightly higher than the critical Richardson number of 0.1, particles and water vapor are injected at the bottom of the riser. Countercurrents appear near the walls and gravity effects begin to dominate in- ducing an increase of particulate volumic fractions near the walls. We show here the hydrodynamics for 13s. 2
Spectral Decomposition Algorithm (SDA)
National Aeronautics and Space Administration — Spectral Decomposition Algorithm (SDA) is an unsupervised feature extraction technique similar to PCA that was developed to better distinguish spectral features in...
ANALYSIS OF AUGMENTED THREE-FIELD MACRO-HYBRID MIXED FINITE ELEMENT SCHEMES
Institute of Scientific and Technical Information of China (English)
Gonzalo Alduncin
2009-01-01
On the basis of composition duality principles, augmented three-field macro-hybrid mixed variational problems and finite element schemes are analyzed. The compati-bility condition adopted here, for compositional dualization, is the coupling operator surjec-tivity, property that expresses in a general operator sense the Ladysenskaja-Babuska-Brezzi inf-sup condition. Variational macro-hybridization is performed under the assumption of decomposable primal and dual spaces relative to nonoverlapping domain decompositions. Then, through compositional dualization macro-hybrid mixed problems are obtained, with internal boundary dual traces as Lagrange multipliers. Also, "mass" preconditioned aug-mentation of three-field formulations are derived, stabilizing macro-hybrid mixed finite element schemes and rendering possible speed up of rates of convergence. Dual mixed incompressible Darcy flow problems illustrate the theory throughout the paper.
Sun, Qiming; Xu, Qian; Dong, Xiangbai; Cao, Lin; Huang, Xiaofeng; Hu, Qingang; Hua, Zi-Chun
2008-08-15
Directional and controllable degradation of extracellular matrix mediated by the uPA-uPA receptor (uPAR) system is ubiquitously implicated in tumor establishment, invasion and metastasis. Targeting the excessive activation of this system as well as the proliferation of the tumor vascular endothelial cell would be expected to prevent tumor neovasculature and halt the tumor development. In this study, we created a fusion protein (ALV), comprising the aminoterminal fragment (ATF) of urokinase and VAS, the antiangiogenic functional domain of vasostatin. The antitumor activity of this hybrid molecule was evaluated with both in vitro and in vivo experiments. Cell adhesion and motility assays demonstrated that ALV, owing to its ATF moiety, could interact with uPAR on the tumor cell surface with high affinity and specificity, and thereby might competitively inhibit the plasmin activation by localized urokinase and contribute to the suppression of tumor invasion. These results and speculations were validated by zymography assay and Matrigel invasion assay. In addition, ALV exhibited an improved inhibitory efficacy against endothelial cell (EC) proliferation and capillary vessel formation in a 3D angiogenesis model, proving that ATF and VAS, when fused into a chimeric molecule, cooperatively inhibited angiogenesis by targeting both the interaction of uPA and uPAR on cell surface (by ATF) and EC proliferation (mainly by VAS). Animal model confirmed that, at the same molar dose, ALV produced significantly higher therapeutic benefit than VAS and ATF in terms of tumor growth delay and mice survival prolongation. Conclusively coupling VAS with the uPAR ligand ATF resulted in an improved antineoplastic activity, which may show a novel avenue for the design of tumor therapeutic drugs. (c) 2008 Wiley-Liss, Inc.
A DECOMPOSITION METHOD OF STRUCTURAL DECOMPOSITION ANALYSIS
Institute of Scientific and Technical Information of China (English)
LI Jinghua
2005-01-01
Over the past two decades,structural decomposition analysis(SDA)has developed into a major analytical tool in the field of input-output(IO)techniques,but the method was found to suffer from one or more of the following problems.The decomposition forms,which are used to measure the contribution of a specific determinant,are not unique due to the existence of a multitude of equivalent forms,irrational due to the weights of different determinants not matching,inexact due to the existence of large interaction terms.In this paper,a decomposition method is derived to overcome these deficiencies,and we prove that the result of this approach is equal to the Shapley value in cooperative games,and so some properties of the method are obtained.Beyond that,the two approaches that have been used predominantly in the literature have been proved to be the approximate solutions of the method.
Eigenvalue Decomposition-Based Modified Newton Algorithm
Directory of Open Access Journals (Sweden)
Wen-jun Wang
2013-01-01
Full Text Available When the Hessian matrix is not positive, the Newton direction may not be the descending direction. A new method named eigenvalue decomposition-based modified Newton algorithm is presented, which first takes the eigenvalue decomposition of the Hessian matrix, then replaces the negative eigenvalues with their absolute values, and finally reconstructs the Hessian matrix and modifies the searching direction. The new searching direction is always the descending direction. The convergence of the algorithm is proven and the conclusion on convergence rate is presented qualitatively. Finally, a numerical experiment is given for comparing the convergence domains of the modified algorithm and the classical algorithm.
Multiresolution signal decomposition schemes
J. Goutsias (John); H.J.A.M. Heijmans (Henk)
1998-01-01
textabstract[PNA-R9810] Interest in multiresolution techniques for signal processing and analysis is increasing steadily. An important instance of such a technique is the so-called pyramid decomposition scheme. This report proposes a general axiomatic pyramid decomposition scheme for signal analysis
Multiresolution signal decomposition schemes
Goutsias, J.; Heijmans, H.J.A.M.
1998-01-01
[PNA-R9810] Interest in multiresolution techniques for signal processing and analysis is increasing steadily. An important instance of such a technique is the so-called pyramid decomposition scheme. This report proposes a general axiomatic pyramid decomposition scheme for signal analysis and synthes
Daverman, Robert J
2007-01-01
Decomposition theory studies decompositions, or partitions, of manifolds into simple pieces, usually cell-like sets. Since its inception in 1929, the subject has become an important tool in geometric topology. The main goal of the book is to help students interested in geometric topology to bridge the gap between entry-level graduate courses and research at the frontier as well as to demonstrate interrelations of decomposition theory with other parts of geometric topology. With numerous exercises and problems, many of them quite challenging, the book continues to be strongly recommended to eve
Dominant modal decomposition method
Dombovari, Zoltan
2017-03-01
The paper deals with the automatic decomposition of experimental frequency response functions (FRF's) of mechanical structures. The decomposition of FRF's is based on the Green function representation of free vibratory systems. After the determination of the impulse dynamic subspace, the system matrix is formulated and the poles are calculated directly. By means of the corresponding eigenvectors, the contribution of each element of the impulse dynamic subspace is determined and the sufficient decomposition of the corresponding FRF is carried out. With the presented dominant modal decomposition (DMD) method, the mode shapes, the modal participation vectors and the modal scaling factors are identified using the decomposed FRF's. Analytical example is presented along with experimental case studies taken from machine tool industry.
Litter Decomposition Rates, 2015
U.S. Geological Survey, Department of the Interior — This data set contains decomposition rates for litter of Salicornia pacifica, Distichlis spicata, and Deschampsia cespitosa buried at 7 tidal marsh sites in 2015....
Spectral proper orthogonal decomposition
Sieber, Moritz; Paschereit, Christian Oliver
2015-01-01
The identification of coherent structures from experimental or numerical data is an essential task when conducting research in fluid dynamics. This typically involves the construction of an empirical mode base that appropriately captures the dominant flow structures. The most prominent candidates are the energy-ranked proper orthogonal decomposition (POD) and the frequency ranked Fourier decomposition and dynamic mode decomposition (DMD). However, these methods fail when the relevant coherent structures occur at low energies or at multiple frequencies, which is often the case. To overcome the deficit of these "rigid" approaches, we propose a new method termed Spectral Proper Orthogonal Decomposition (SPOD). It is based on classical POD and it can be applied to spatially and temporally resolved data. The new method involves an additional temporal constraint that enables a clear separation of phenomena that occur at multiple frequencies and energies. SPOD allows for a continuous shifting from the energetically ...
Blankertz, Raoul
2011-01-01
This diploma thesis is concerned with functional decomposition $f = g \\circ h$ of polynomials. First an algorithm is described which computes decompositions in polynomial time. This algorithm was originally proposed by Zippel (1991). A bound for the number of minimal collisions is derived. Finally a proof of a conjecture in von zur Gathen, Giesbrecht & Ziegler (2010) is given, which states a classification for a special class of decomposable polynomials.
Weighted Decomposition Estimates for Differential Forms
Directory of Open Access Journals (Sweden)
Yong Wang
2010-01-01
Full Text Available After introducing the definition of Ar,λβ-weights, we establish the Ar(Ω-weighted decomposition estimates and Ar,λβ(Ω-weighted Caccioppoli-type estimates for A-harmonic tensors. Furthermore, by Whitney covering lemma, we obtain the global results in domain Ω⊂Rn. These results can be used to study the integrability of differential forms and to estimate the integrals for differential forms.
DEFF Research Database (Denmark)
Jamison, Andrew; Christensen, Steen Hyldgaard; Botin, Lars
contexts, or sites, for mixing scientific knowledge and technical skills from different fields and social domains into new combinations, thus fostering what the authors term a “hybrid imagination”. Such a hybrid imagination is especially important today, as a way to counter the competitive and commercial...
Collins, P.J.
2005-01-01
In this paper, we present a general framework for describing and studying hybrid systems. We represent the trajectories of the system as functions on a hybrid time domain, and the system itself by its trajectory space, which is the set of all possible trajectories. The trajectory space is given a na
Innocenti, M. E.; Norgren, C.; Newman, D.; Goldman, M.; Markidis, S.; Lapenta, G.
2016-05-01
The newly developed fully kinetic, semi-implicit, adaptive multi-level multi-domain (MLMD) method is used to simulate, at realistic mass ratio, the development of the lower hybrid drift instability (LHDI) in the terrestrial magnetotail over a large wavenumber range and at a low computational cost. The power spectra of the perpendicular electric field and of the fluctuations of the parallel magnetic field are studied at wavenumbers and times that allow to appreciate the onset of the electrostatic and electromagnetic LHDI branches and of the kink instability. The coupling between electric and magnetic field fluctuations observed by Norgren et al. ["Lower hybrid drift waves: Space observations," Phys. Rev. Lett. 109, 055001 (2012)] for high wavenumber LHDI waves in the terrestrial magnetotail is verified. In the MLMD simulations presented, a domain ("coarse grid") is simulated with low resolution. A small fraction of the entire domain is then simulated with higher resolution also ("refined grid") to capture smaller scale, higher frequency processes. Initially, the MLMD method is validated for LHDI simulations. MLMD simulations with different levels of grid refinement are validated against the standard semi-implicit particle in cell simulations of domains corresponding to both the coarse and the refined grid. Precious information regarding the applicability of the MLMD method to turbulence simulations is derived. The power spectra of MLMD simulations done with different levels of refinements are then compared. They consistently show a break in the magnetic field spectra at k⊥di˜30 , with di the ion skin depth and k⊥ the perpendicular wavenumber. The break is observed at early simulated times, Ωcit <6 , with Ωci the ion cyclotron frequency. It is due to the initial decoupling of electric and magnetic field fluctuations at intermediate and low wavenumbers, before the development of the electromagnetic LHDI branch. Evidence of coupling between electric and magnetic
Díaz, B G; Gross, S; Assfalg-Machleidt, I; Pfeiler, D; Gollmitzer, N; Gabrijelcic-Geiger, D; Stubbs, M T; Fritz, H; Auerswald, E A; Machleidt, W
2001-01-01
Within the cystatin superfamily, only kininogen domain 2 (KD2) is able to inhibit mu- and m-calpain. In an attempt to elucidate the structural requirements of cystatins for calpain inhibition, we constructed recombinant hybrids of human stefin B (an intracellular family 1 cystatin) with KD2 and deltaL110 deletion mutants of chicken cystatin-KD2 hybrids. Substitution of the N-terminal contact region of stefin B by the corresponding KD2 sequence resulted in a calpain inhibitor of Ki = 188 nM. Deletion of L110, which forms a beta-bulge in family 1 and 2 cystatins but is lacking in KD2, improved inhibition of mu-calpain 4- to 8-fold. All engineered cystatins were temporary inhibitors of calpain due to slow substrate-like cleavage of a single peptide bond corresponding to Gly9-Ala10 in chicken cystatin. Biomolecular interaction analysis revealed that, unlike calpastatin, the cystatin-type inhibitors do not bind to the calmodulin-like domain of the small subunit of calpain, and their interaction with the mu-calpain heterodimer is completely prevented by a synthetic peptide comprising subdomain B of calpastatin domain 1. Based on these results we propose that (i) cystatin-type calpain inhibitors interact with the active site of the catalytic domain of calpain in a similar cystatin-like mode as with papain and (ii) the potential for calpain inhibition is due to specific subsites within the papain-binding regions of the general cystatin fold.
Institute of Scientific and Technical Information of China (English)
薛青娜; 校江超
2011-01-01
In order to achieve the phase-inversion symmetric and spread spectrum communication, according to the relativity of noise in time domain and the anti-noise theory of time domain phase-inversions hybrid structure of time domain phase-inversion symmetric and spread spectrum is proposed. The simulation and experimental results show that time domain phase-inversion symmetric and spread spectrum system can get higher output SNR and under the same transmission conditions, the phase-inversion symmetric spread spectrum technology is superior to the general spread spectrum technology. This method can find a wide use in mobile communications.%为了实现反相对称扩频通讯技术,根据噪声在时域上的相关性以及反相对称法的抗噪原理,将反相对称法与扩频通信相结合实现了一种新的扩频通信方法.仿真结果表明:时域反相对称扩频技术系统能获得较高的输出信噪比,且在相同的传输条件下,反相对称扩频技术的性能优于一般的扩频技术,该通信方法可以在移动通讯中推广应用.
DEFF Research Database (Denmark)
Haberland, Hartmut
2005-01-01
The domain concept, originally suggested by Schmidt-Rohr in the 1930’s (as credited in Fishman’s writings in the 1970s), was an attempt to sort out different areas of language use in multilingual societies, which are relevant for language choice. In Fishman’s version, domains were considered...... not described in terms of domains, and recent research e.g. about the multilingual communities in the Danish-German border area seems to confirm this....
Decomposing Nekrasov Decomposition
Morozov, A
2015-01-01
AGT relations imply that the four-point conformal block admits a decomposition into a sum over pairs of Young diagrams of essentially rational Nekrasov functions - this is immediately seen when conformal block is represented in the form of a matrix model. However, the q-deformation of the same block has a deeper decomposition - into a sum over a quadruple of Young diagrams of a product of four topological vertices. We analyze the interplay between these two decompositions, their properties and their generalization to multi-point conformal blocks. In the latter case we explain how Dotsenko-Fateev all-with-all (star) pair "interaction" is reduced to the quiver model nearest-neighbor (chain) one. We give new identities for q-Selberg averages of pairs of generalized Macdonald polynomials. We also translate the slicing invariance of refined topological strings into the language of conformal blocks and interpret it as abelianization of generalized Macdonald polynomials.
Decomposing Nekrasov decomposition
Morozov, A.; Zenkevich, Y.
2016-02-01
AGT relations imply that the four-point conformal block admits a decomposition into a sum over pairs of Young diagrams of essentially rational Nekrasov functions — this is immediately seen when conformal block is represented in the form of a matrix model. However, the q-deformation of the same block has a deeper decomposition — into a sum over a quadruple of Young diagrams of a product of four topological vertices. We analyze the interplay between these two decompositions, their properties and their generalization to multi-point conformal blocks. In the latter case we explain how Dotsenko-Fateev all-with-all (star) pair "interaction" is reduced to the quiver model nearest-neighbor (chain) one. We give new identities for q-Selberg averages of pairs of generalized Macdonald polynomials. We also translate the slicing invariance of refined topological strings into the language of conformal blocks and interpret it as abelianization of generalized Macdonald polynomials.
Symmetric tensor decomposition
Brachat, Jerome; Mourrain, Bernard; Tsigaridas, Elias
2009-01-01
We present an algorithm for decomposing a symmetric tensor, of dimension n and order d as a sum of rank-1 symmetric tensors, extending the algorithm of Sylvester devised in 1886 for binary forms. We recall the correspondence between the decomposition of a homogeneous polynomial in n variables of total degree d as a sum of powers of linear forms (Waring's problem), incidence properties on secant varieties of the Veronese Variety and the representation of linear forms as a linear combination of evaluations at distinct points. Then we reformulate Sylvester's approach from the dual point of view. Exploiting this duality, we propose necessary and sufficient conditions for the existence of such a decomposition of a given rank, using the properties of Hankel (and quasi-Hankel) matrices, derived from multivariate polynomials and normal form computations. This leads to the resolution of polynomial equations of small degree in non-generic cases. We propose a new algorithm for symmetric tensor decomposition, based on th...
Guillaumot, Damien; Lelu-Walter, Marie-Anne; Germot, Agnès; Meytraud, Fanny; Gastinel, Louis; Riou-Khamlichi, Catherine
2008-06-16
Two APETALA2 domain transcription factors were characterized first in angiosperms, and, recently, in several gymnosperms. These proteins are involved in several processes, from flowering to embryogenesis in Arabidopsis thaliana. We extrapolated this result to hybrid larch (Larixxmarschlinsii Coaz) resulting from a cross between European (Larix decidua) and Japanese (Larix kaempferi) larches. Somatic embryogenesis is well described and controlled for this Pinaceae. We characterized two-AP2 domain genes: LmAP2L1 and LmAP2L2. Phylogenetic analysis confirmed that LmAP2L1 and LmAP2L2 were orthologous to Norway spruce PaAP2L1 and PaAP2L2 and that L1 forms appeared to be specific to Pinaceae. RT-PCR analysis showed that larch APETALA2 was differentially expressed during late somatic embryogenesis and during the first steps of germination. Whereas LmAP2L2 was constitutively expressed during this process, LmAP2L1 expression appeared only during late somatic embryogenesis, when embryos were able to germinate. Further, LmAP2L1 appeared to be the preferentially expressed form during embryo germination. Thus, LmAP2L1 seems to be a valuable molecular marker for hybrid larch late somatic embryogenesis and could play a role during post-embryonic development.
Mueller matrix differential decomposition.
Ortega-Quijano, Noé; Arce-Diego, José Luis
2011-05-15
We present a Mueller matrix decomposition based on the differential formulation of the Mueller calculus. The differential Mueller matrix is obtained from the macroscopic matrix through an eigenanalysis. It is subsequently resolved into the complete set of 16 differential matrices that correspond to the basic types of optical behavior for depolarizing anisotropic media. The method is successfully applied to the polarimetric analysis of several samples. The differential parameters enable one to perform an exhaustive characterization of anisotropy and depolarization. This decomposition is particularly appropriate for studying media in which several polarization effects take place simultaneously. © 2011 Optical Society of America
Decomposition of residue currents
Andersson, Mats; Wulcan, Elizabeth
2007-01-01
Given a submodule $J\\subset \\mathcal O_0^{\\oplus r}$ and a free resolution of $J$ one can define a certain vector valued residue current whose annihilator is $J$. We make a decomposition of the current with respect to Ass$(J)$ that correspond to a primary decomposition of $J$. As a tool we introduce a class of currents that includes usual residue and principal value currents; in particular these currents admit a certain type of restriction to analytic varieties and more generally to construct...
Hybrid Finite Element and Volume Integral Methods for Scattering Using Parametric Geometry
DEFF Research Database (Denmark)
Volakis, John L.; Sertel, Kubilay; Jørgensen, Erik
2004-01-01
n this paper we address several topics relating to the development and implementation of volume integral and hybrid finite element methods for electromagnetic modeling. Comparisons of volume integral equation formulations with the finite element-boundary integral method are given in terms of accu...... of vanishing divergence within the element but non-zero curl. In addition, a new domain decomposition is introduced for solving array problems involving several million degrees of freedom. Three orders of magnitude CPU reduction is demonstrated for such applications....
Tree decompositions with small cost
Bodlaender, H.L.; Fomin, F.V.
2002-01-01
The f-cost of a tree decomposition ({Xi | i e I}, T = (I;F)) for a function f : N -> R+ is defined as EieI f(|Xi|). This measure associates with the running time or memory use of some algorithms that use the tree decomposition. In this paper we investigate the problem to find tree decompositions
Further validation of the hybrid particle-mesh method for vortex shedding flow simulations
Directory of Open Access Journals (Sweden)
Lee Seung-Jae
2015-11-01
Full Text Available This is the continuation of a numerical study on vortex shedding from a blunt trailing-edge of a hydrofoil. In our previous work (Lee et al., 2015, numerical schemes for efficient computations were successfully implemented; i.e. multiple domains, the approximation of domain boundary conditions using cubic spline functions, and particle-based domain decomposition for better load balancing. In this study, numerical results through a hybrid particle-mesh method which adopts the Vortex-In-Cell (VIC method and the Brinkman penalization model are further rigorously validated through comparison to experimental data at the Reynolds number of 2 × 106. The effects of changes in numerical parameters are also explored herein. We find that the present numerical method enables us to reasonably simulate vortex shedding phenomenon, as well as turbulent wakes of a hydrofoil.
Formal Language Decomposition into Semantic Primes
Directory of Open Access Journals (Sweden)
Johannes FÄHNDRICH
2014-10-01
Full Text Available This paper describes an algorithm for semantic decomposition. For that we surveys languages used to enrich contextual information with semantic descriptions. Such descriptions can be e.g. applied to enable reasoning when collecting vast amounts of information. In particular, we focus on the elements of the languages that make up their semantic. To do so, we compare the expressiveness of the well-known languages OWL, PDDL and MOF with a theory from linguistic called the Natural Semantic Metalanguage. We then analyze how the semantic of the language is build up and describe how semantic decomposition based on the semantic primes can be used for a so called mental lexicon. This mental lexicon can be used to reason upon semantic service description in the research domain of service match making.
Hybridization of DCT and SVD in the Implementation and Performance Analysis of Video Watermarking
Directory of Open Access Journals (Sweden)
Ved Vyas Dwivedi
2012-06-01
Full Text Available In this Paper, We worked and documented the implementation and performance analysis of digital video watermarking that uses the hybrid features of two of the most powerful transform domain processing of the video and fundamentals of the linear algebra. We have taken into the account fundamentals of Discrete Cosine Transform and Singular Value Decomposition for the development of the proposed algorithm. We first used the Singular Value Decomposition and then used the singular values for the insertion of the message behind the video. Finally we used two of the visual quality matrices for the analysis purpose. We also applied various attacks on the video and found the proposed scheme more robust.
Zeng, Xiao-Li; Tang, Kun; Zhou, Nan; Zhou, Ming; Hou, Harvey J M; Scheer, Hugo; Zhao, Kai-Hong; Noy, Dror
2013-09-11
The phycobilisomes of cyanobacteria and red-algae are highly efficient peripheral light-harvesting complexes that capture and transfer light energy in a cascade of excitation energy transfer steps through multiple phycobilin chromophores to the chlorophylls of core photosystems. In this work, we focus on the last step of this process by constructing simple functional analogs of natural phycobilisome-photosystem complexes that are based on bichromophoric protein complexes comprising a phycobilin- and a chlorophyll- or porphyrin-binding domain. The former is based on ApcE(1-240), the N-terminal chromophore-binding domain of the phycobilisome's L(CM) core-membrane linker, and the latter on HP7, a de novo designed four-helix bundle protein that was originally planned as a high-affinity heme-binding protein, analogous to b-type cytochromes. We fused a modified HP7 protein sequence to ApcEΔ, a water-soluble fragment of ApcE(1-240) obtained by excising a putative hydrophobic loop sequence of residues 77-153. HP7 was fused either to the N- or the C-terminus of ApcEΔ or inserted between residues 76 and 78, thereby replacing the native hydrophobic loop domain. We describe the assembly, spectral characteristics, and intramolecular excitation energy transfer of two unique systems: in the first, the short-wavelength absorbing zinc-mesoporphyrin is bound to the HP7 domain and serves as an excitation-energy donor to the long-wavelength absorbing phycocyanobilin bound to the ApcE domain; in the second, the short-wavelength absorbing phycoerythrobilin is bound to the ApcE domain and serves as an excitation energy donor to the long-wavelength absorbing zinc-bacteriochlorophyllide bound to the HP7 domain. All the systems that were constructed and tested exhibited significant intramolecular fluorescence resonance energy transfer with yields ranging from 21% to 50%. This confirms that our modular, covalent approach for studying EET between the cyclic and open chain tetrapyrroles is
Institute of Scientific and Technical Information of China (English)
2015-01-01
网络怨恨既是一种情感体验，也是一种生存状态。越来越多的虚拟社会现象表明，网络怨恨已经出现了一定程度上的弥散，虚拟公共领域秩序建构因而面临着无法回避的现实梗阻。网络怨恨导致无直接利益冲突的网络暴力频现，基于网络民粹主义的阶层对抗遭遇激化，同时网络空间出现颠覆性的价值位移。究其根源，网络怨恨与网络世界的平等理念、现代社会的竞争意识和难以克服的现实困境密切相关。需要通过提升虚拟公共领域的公共理性，适度满足网络怨恨的宣泄需求，构建包容性发展的网络监督体系，纠正虚拟公共领域中的价值位移等途径，才能真正消解网络怨恨，实现虚拟公共领域的秩序化运行。%Network hatred is not only an emotional experience , but also a living state.It is suggested by more and more virtual social phenomenon that network hatred has been dispersing in the new public domain and has become virtual social emotions in the keynote.Thus, order construction in the virtual public domain has been ex-posed to practical obstructions which cannot be evaded.As a result of network hatred , network violence , which has no direct conflict of interests , frequently shows up , and network populism-based hierarchical confrontation is triggered , and concurrently , subversive value displacement shows up in network space.Tracing to the source , network hatred is closely related to the equality philosophy of network world , the sense of competition in the modern society and the insurmountable practical difficulties.Only by such channels as improving public reason of the virtual public domain , moderately satisfying the needs for unbosoming network hatred , constructing net-work supervision system under inclusive development and correcting value displacement in the virtual public do -main, can network hatred be truly decomposed and regularized operation of the
Bibolini, M J; Scerbo, M J; Roth, G A; Monferran, C G
2014-09-26
Multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), are crucially dependent on the invasion of activated autoreactive lymphocytes and blood macrophages into the central nervous system (CNS). Proinflammatory mononuclear cells and activated local microglia mediate inflammation, demyelination and axonal damage at the target organ. Previously, we observed that the administration of a hybrid between the synapsin ABC domains and the B subunit of Escherichia coli heat labile-enterotoxin (LTBABC) to rats with EAE ameliorated disease by modulating the peripheral Th1 response to myelin basic protein (MBP). In the present study, we investigated the effect of LTBABC administration on proinflammatory cell frequency in the CNS of rats with EAE. Treatment with the hybrid in the inductive phase of EAE attenuated disease severity and diminished histological inflammatory infiltrates and demyelination in the spinal cord of rats with acute EAE. Lower frequencies of infiltrating and local macrophages as well as CD4+ T cells that produce the proinflammatory cytokines interferon-gamma (IFN-γ) and interleukin (IL)-17 were found at the target organ. Concomitantly, low levels of INF-γ and IL-17 and increased levels of IL-10 were measured in cultures of CNS infiltrating cells and spinal cord tissue. An increased frequency of CD4+CD25+Foxp3 cells was observed at the disease peak and at the beginning of the recovery stage. These results provide further evidence for the immunomodulatory properties of the fusion protein LTBABC in autoimmune demyelinating disease affecting the central nervous system.
基于Gabor特征分解的高斯混合非线性滤波算法%Gauss Hybrid Nonlinear Filter Design Based on Gabor Feature Decomposition
Institute of Scientific and Technical Information of China (English)
高菲菲
2015-01-01
传统的窄带信号检测滤波器采用IIR自适应线谱增强滤波算法,对信号特征分解的阶数要求高,导致非线性失真,提出一种基于Gabor特征分解的高斯混合非线性滤波器设计算法,在IIR滤波器设计的基础上,对信号进行尺度和时延估计,构建自适应高阶累积量滤波设计方法,采用高阶累积量对窄带信号进行均方一致估计,对Gabor特征函数Taylor级数展开,求得高斯混合非线性滤波器的带宽参数,最后实现高斯混合非线性滤波器设计改进,提高对窄带信号的检测性能.仿真结果表明,该算法具有较好的滤波性能,可以明显地抑制色噪声的影响,提高信号增益达到20 dB.%Narrow band signal detection filter is used in the traditional IIR adaptive line enhancement algorithm, order de-composition on signal feature requirements, resulting in nonlinear distortion, this paper puts forward a Gabor feature decom-position algorithm based on Gauss mixture nonlinear filter design, based on IIR filter design, scale and time delay estima-tion of signal, to construct an adaptive high order cumulants filter design method, using high order cumulant of mean square consistent estimation of narrowband signals, the characteristic function expansion on the Gabor Taylor series, the band-width parameter obtained Gauss mixed nonlinear filter, finally realize the Gauss improvement of mixed nonlinear filter de-sign, improve the detection performance of the narrowband signal. The simulation results show that the proposed algorithm has good filtering performance and can obviously suppress the color noise and improve the signal gain of 20 dB.
The Harmonic Decomposition Reconstruction for the Exponential Radon Transform
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The exponential Radon transform, a generalization of the Radon transform, is defined andstudied as a mapping of function spaces. It is represented in terms of Fourier transform of its domain andrange, and this leads to the harmonic decomposition reconstruction. The results are similar results of Tre-tiak and Metz.
Linear round bit-decomposition of secret-shared values
Veugen, P.J.M.
2015-01-01
In the field of signal processing in the encrypted domain, linear operations are usually easy to perform, whereas multiplications, and bitwise operations like comparison, are more costly in terms of computation and communication. These bitwise operations frequently require a decomposition of the sec
Adaptive Integrand Decomposition
Mastrolia, Pierpaolo; Primo, Amedeo; Bobadilla, William J Torres
2016-01-01
We present a simplified variant of the integrand reduction algorithm for multiloop scattering amplitudes in $d = 4 - 2\\epsilon$ dimensions, which exploits the decomposition of the integration momenta in parallel and orthogonal subspaces, $d=d_\\parallel+d_\\perp$, where $d_\\parallel$ is the dimension of the space spanned by the legs of the diagrams. We discuss the advantages of a lighter polynomial division algorithm and how the orthogonality relations for Gegenbauer polynomilas can be suitably used for carrying out the integration of the irreducible monomials, which eliminates spurious integrals. Applications to one- and two-loop integrals, for arbitrary kinematics, are discussed.
Clustering via Kernel Decomposition
DEFF Research Database (Denmark)
Have, Anna Szynkowiak; Girolami, Mark A.; Larsen, Jan
2006-01-01
Methods for spectral clustering have been proposed recently which rely on the eigenvalue decomposition of an affinity matrix. In this work it is proposed that the affinity matrix is created based on the elements of a non-parametric density estimator. This matrix is then decomposed to obtain...... posterior probabilities of class membership using an appropriate form of nonnegative matrix factorization. The troublesome selection of hyperparameters such as kernel width and number of clusters can be obtained using standard cross-validation methods as is demonstrated on a number of diverse data sets....
Symmetric Tensor Decomposition
DEFF Research Database (Denmark)
Brachat, Jerome; Comon, Pierre; Mourrain, Bernard
2010-01-01
of polynomial equations of small degree in non-generic cases. We propose a new algorithm for symmetric tensor decomposition, based on this characterization and on linear algebra computations with Hankel matrices. The impact of this contribution is two-fold. First it permits an efficient computation...... of total degree d as a sum of powers of linear forms (Waring’s problem), incidence properties on secant varieties of the Veronese variety and the representation of linear forms as a linear combination of evaluations at distinct points. Then we reformulate Sylvester’s approach from the dual point of view...
Hydrogen peroxide catalytic decomposition
Parrish, Clyde F. (Inventor)
2010-01-01
Nitric oxide in a gaseous stream is converted to nitrogen dioxide using oxidizing species generated through the use of concentrated hydrogen peroxide fed as a monopropellant into a catalyzed thruster assembly. The hydrogen peroxide is preferably stored at stable concentration levels, i.e., approximately 50%-70% by volume, and may be increased in concentration in a continuous process preceding decomposition in the thruster assembly. The exhaust of the thruster assembly, rich in hydroxyl and/or hydroperoxy radicals, may be fed into a stream containing oxidizable components, such as nitric oxide, to facilitate their oxidation.
Spectral Tensor-Train Decomposition
DEFF Research Database (Denmark)
Bigoni, Daniele; Engsig-Karup, Allan Peter; Marzouk, Youssef M.
2016-01-01
The accurate approximation of high-dimensional functions is an essential task in uncertainty quantification and many other fields. We propose a new function approximation scheme based on a spectral extension of the tensor-train (TT) decomposition. We first define a functional version of the TT.......e., the “cores”) comprising the functional TT decomposition. This result motivates an approximation scheme employing polynomial approximations of the cores. For functions with appropriate regularity, the resulting spectral tensor-train decomposition combines the favorable dimension-scaling of the TT...... decomposition with the spectral convergence rate of polynomial approximations, yielding efficient and accurate surrogates for high-dimensional functions. To construct these decompositions, we use the sampling algorithm \\tt TT-DMRG-cross to obtain the TT decomposition of tensors resulting from suitable...
MACH: Fast Randomized Tensor Decompositions
Tsourakakis, Charalampos E
2009-01-01
Tensors naturally model many real world processes which generate multi-aspect data. Such processes appear in many different research disciplines, e.g, chemometrics, computer vision, psychometrics and neuroimaging analysis. Tensor decompositions such as the Tucker decomposition are used to analyze multi-aspect data and extract latent factors, which capture the multilinear data structure. Such decompositions are powerful mining tools, for extracting patterns from large data volumes. However, most frequently used algorithms for such decompositions involve the computationally expensive Singular Value Decomposition. In this paper we propose MACH, a new sampling algorithm to compute such decompositions. Our method is of significant practical value for tensor streams, such as environmental monitoring systems, IP traffic matrices over time, where large amounts of data are accumulated and the analysis is computationally intensive but also in "post-mortem" data analysis cases where the tensor does not fit in the availa...
Nonlinear vibrating system identification via Hilbert decomposition
Feldman, Michael; Braun, Simon
2017-02-01
This paper deals with the identification of nonlinear vibration systems, based on measured signals for free and forced vibration regimes. Two categories of time domain signal are analyzed, one of a fast inter-modulation signal and a second as composed of several mono-components. To some extent, this attempts to imitate analytic studies of such systems, with its two major analysis groups - the perturbation and the harmonic balance methods. Two appropriate signal processing methods are then investigated, one based on demodulation and the other on signal decomposition. The Hilbert Transform (HT) has been shown to enable effective and simple methods of analysis. We show that precise identification of the nonlinear parameters can be obtained, contrary to other average HT based methods where only approximation parameters are obtained. The effectiveness of the proposed methods is demonstrated for the precise nonlinear system identification, using both the signal demodulation and the signal decomposition methods. Following the exposition of the tools used, both the signal demodulation as well as decomposition are applied to classical examples of nonlinear systems. Cases of nonlinear stiffness and damping forces are analyzed. These include, among other, an asymmetric Helmholtz oscillator, a backlash with nonlinear turbulent square friction, and a Duffing oscillator with dry friction.
Nuclear driven water decomposition plant for hydrogen production
Parker, G. H.; Brecher, L. E.; Farbman, G. H.
1976-01-01
The conceptual design of a hydrogen production plant using a very-high-temperature nuclear reactor (VHTR) to energize a hybrid electrolytic-thermochemical system for water decomposition has been prepared. A graphite-moderated helium-cooled VHTR is used to produce 1850 F gas for electric power generation and 1600 F process heat for the water-decomposition process which uses sulfur compounds and promises performance superior to normal water electrolysis or other published thermochemical processes. The combined cycle operates at an overall thermal efficiency in excess of 45%, and the overall economics of hydrogen production by this plant have been evaluated predicated on a consistent set of economic ground rules. The conceptual design and evaluation efforts have indicated that development of this type of nuclear-driven water-decomposition plant will permit large-scale economic generation of hydrogen in the 1990s.
Patterson, Brian D; Gao, Yi; Seeger, Thomas; Kliewer, Christopher J
2013-11-15
We introduce a multiplex technique for the single-laser-shot determination of S-branch Raman linewidths with high accuracy and precision by implementing hybrid femtosecond (fs)/picosecond (ps) rotational coherent anti-Stokes Raman spectroscopy (CARS) with multiple spatially and temporally separated probe beams derived from a single laser pulse. The probe beams scatter from the rotational coherence driven by the fs pump and Stokes pulses at four different probe pulse delay times spanning 360 ps, thereby mapping collisional coherence dephasing in time for the populated rotational levels. The probe beams scatter at different folded BOXCARS angles, yielding spatially separated CARS signals which are collected simultaneously on the charge coupled device camera. The technique yields a single-shot standard deviation (1σ) of less than 3.5% in the determination of Raman linewidths and the average linewidth values obtained for N(2) are within 1% of those previously reported. The presented technique opens the possibility for correcting CARS spectra for time-varying collisional environments in operando.
Application of sparse time-frequency decomposition to seismic data
Institute of Scientific and Technical Information of China (English)
Wang Xiong-Wen; Wang Hua-Zhong
2014-01-01
The Gabor and S transforms are frequently used in time-frequency decomposition methods. Constrained by the uncertainty principle, both transforms produce low-resolution time-frequency decomposition results in the time and frequency domains. To improve the resolution of the time-frequency decomposition results, we use the instantaneous frequency distribution function (IFDF) to express the seismic signal. When the instantaneous frequencies of the nonstationary signal satisfy the requirements of the uncertainty principle, the support of IFDF is just the support of the amplitude ridges in the signal obtained using the short-time Fourier transform. Based on this feature, we propose a new iteration algorithm to achieve the sparse time-frequency decomposition of the signal. The iteration algorithm uses the support of the amplitude ridges of the residual signal obtained with the short-time Fourier transform to update the time-frequency components of the signal. The summation of the updated time-frequency components in each iteration is the result of the sparse time-frequency decomposition. Numerical examples show that the proposed method improves the resolution of the time-frequency decomposition results and the accuracy of the analysis of the nonstationary signal. We also use the proposed method to attenuate the ground roll of field seismic data with good results.
A hybrid algorithm for parallel molecular dynamics simulations
Mangiardi, Chris M
2016-01-01
This article describes an algorithm for hybrid parallelization and SIMD vectorization of molecular dynamics simulations with short-ranged forces. The parallelization method combines domain decomposition with a thread-based parallelization approach. The goal of the work is to enable efficient simulations of very large (tens of millions of atoms) and inhomogeneous systems on many-core processors with hundreds or thousands of cores and SIMD units with large vector sizes. In order to test the efficiency of the method, simulations of a variety of configurations with up to 74 million atoms have been performed. Results are shown that were obtained on multi-core systems with AVX and AVX-2 processors as well as Xeon-Phi co-processors.
A hybrid algorithm for parallel molecular dynamics simulations
Mangiardi, Chris M.; Meyer, R.
2017-10-01
This article describes algorithms for the hybrid parallelization and SIMD vectorization of molecular dynamics simulations with short-range forces. The parallelization method combines domain decomposition with a thread-based parallelization approach. The goal of the work is to enable efficient simulations of very large (tens of millions of atoms) and inhomogeneous systems on many-core processors with hundreds or thousands of cores and SIMD units with large vector sizes. In order to test the efficiency of the method, simulations of a variety of configurations with up to 74 million atoms have been performed. Results are shown that were obtained on multi-core systems with Sandy Bridge and Haswell processors as well as systems with Xeon Phi many-core processors.
Autonomous Gaussian Decomposition
Lindner, Robert R; Murray, Claire E; Stanimirović, Snežana; Babler, Brian L; Heiles, Carl; Hennebelle, Patrick; Goss, W M; Dickey, John
2014-01-01
We present a new algorithm, named Autonomous Gaussian Decomposition (AGD), for automatically decomposing spectra into Gaussian components. AGD uses derivative spectroscopy and machine learning to provide optimized guesses for the number of Gaussian components in the data, and also their locations, widths, and amplitudes. We test AGD and find that it produces results comparable to human-derived solutions on 21cm absorption spectra from the 21cm SPectral line Observations of Neutral Gas with the EVLA (21-SPONGE) survey. We use AGD with Monte Carlo methods to derive the HI line completeness as a function of peak optical depth and velocity width for the 21-SPONGE data, and also show that the results of AGD are stable against varying observational noise intensity. The autonomy and computational efficiency of the method over traditional manual Gaussian fits allow for truly unbiased comparisons between observations and simulations, and for the ability to scale up and interpret the very large data volumes from the up...
Erbium hydride decomposition kinetics.
Energy Technology Data Exchange (ETDEWEB)
Ferrizz, Robert Matthew
2006-11-01
Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report are analyzed quantitatively using Redhead's method to yield kinetic parameters (E{sub A} {approx} 54.2 kcal/mol), which are then utilized to predict hydrogen outgassing in vacuum for a variety of thermal treatments. Interestingly, it was found that the activation energy for desorption can vary by more than 7 kcal/mol (0.30 eV) for seemingly similar samples. In addition, small amounts of less-stable hydrogen were observed for all erbium dihydride films. A detailed explanation of several approaches for analyzing thermal desorption spectra to obtain kinetic information is included as an appendix.
Differentially Private Spatial Decompositions
Cormode, Graham; Shen, Entong; Srivastava, Divesh; Yu, Ting
2011-01-01
Differential privacy has recently emerged as the de facto standard for private data release. This makes it possible to provide strong theoretical guarantees on the privacy and utility of released data. While it is well-known how to release data based on counts and simple functions under this guarantee, it remains to provide general purpose techniques to release different kinds of data. In this paper, we focus on spatial data such as locations and more generally any data that can be indexed by a tree structure. Directly applying existing differential privacy methods to this type of data simply generates noise. Instead, we introduce a new class of "private spatial decompositions": these adapt standard spatial indexing methods such as quadtrees and kd-trees to provide a private description of the data distribution. Equipping such structures with differential privacy requires several steps to ensure that they provide meaningful privacy guarantees. Various primitives, such as choosing splitting points and describi...
An Improved Hybrid Method for Inverse Obstacle Scattering Problems
Institute of Scientific and Technical Information of China (English)
LIU JUAN; MA FU-MING
2011-01-01
An improved hybrid method is introduced in this paper as a numerical method to reconstruct the scatterer by far-field pattern for just one incident direction with unknown physical properties of the scatterer.The improved hybrid method inherits the idea of the hybrid method by Kress and Serranho which is a combination of Newton and decomposition method,and it improves the hybrid method by introducing a general boundary condition.The numerical experiments show the feasibility of this method.
DEFF Research Database (Denmark)
Hjørland, Birger
2017-01-01
The domain-analytic approach to knowledge organization (KO) (and to the broader field of library and information science, LIS) is outlined. The article reviews the discussions and proposals on the definition of domains, and provides an example of a domain-analytic study in the field of art studie....... Varieties of domain analysis as well as criticism and controversies are presented and discussed....
Texture of lipid bilayer domains
DEFF Research Database (Denmark)
Jensen, Uffe Bernchou; Brewer, Jonathan R.; Midtiby, Henrik Skov
2009-01-01
chains. By imaging the intensity variations as a function of the polarization angle, we map the lateral variations of the lipid tilt within domains. Results reveal that gel domains are composed of subdomains with different lipid tilt directions. We have applied a Fourier decomposition method......We investigate the texture of gel (g) domains in binary lipid membranes composed of the phospholipids DPPC and DOPC. Lateral organization of lipid bilayer membranes is a topic of fundamental and biological importance. Whereas questions related to size and composition of fluid membrane domain...... are well studied, the possibility of texture in gel domains has so far not been examined. When using polarized light for two-photon excitation of the fluorescent lipid probe Laurdan, the emission intensity is highly sensitive to the angle between the polarization and the tilt orientation of lipid acyl...
Ungchusri, T; Kettman, J R; Forman, J
1997-07-01
The CD8 co-receptor interacts with nonpolymorphic residues on class I molecules. LQ3, a laboratory engineered Ld molecule bearing an alpha 3 domain derived from Q7 (Qa-2), interacts poorly with anti-Ld CD8-dependent T cells. 2C TCR transgenic mice bear a receptor specific for the p2Ca peptide bound to Ld. The authors show that although this peptide interacts with LQ3, LQ3 APC fail to activate splenic 2C CD8 T cells in vitro in the absence of IL-2, while control Ld APC do. The authors have used this receptor ligand pair to examine negative selection within the thymus of (B6 x C3H.Ld)F1 versus (B6 x C3H.LQ3)F1 radiation chimeras repopulated with 2C bone marrow cells. While positive selection occurs normally in (B6 x C3H)F1 chimeras, animals expressing either Ld or LQ3 fail to generate 2C CD8+ cells. Thus, either CD8 is not required for negative selection of this TCR or a weak interaction of CD8 with LQ3 is sufficient. TSA-1, a developmentally regulated marker, was used to follow the process of negative selection. The results show that deletion of 2C T cells does not occur until thymocytes reach the double positive (DP) stage. Furthermore, the authors noted a small population of DP TSA-1hi cells remains, while DP TSA-1int and TSA-1lo cells are absent. These data support the notion that thymocytes either reach a particular stage of development or locate in an appropriate intrathymic compartment before they undergo negative selection.
Decomposition methods for unsupervised learning
DEFF Research Database (Denmark)
Mørup, Morten
2008-01-01
This thesis presents the application and development of decomposition methods for Unsupervised Learning. It covers topics from classical factor analysis based decomposition and its variants such as Independent Component Analysis, Non-negative Matrix Factorization and Sparse Coding to their genera......This thesis presents the application and development of decomposition methods for Unsupervised Learning. It covers topics from classical factor analysis based decomposition and its variants such as Independent Component Analysis, Non-negative Matrix Factorization and Sparse Coding...... methods and clustering problems is derived both in terms of classical point clustering but also in terms of community detection in complex networks. A guiding principle throughout this thesis is the principle of parsimony. Hence, the goal of Unsupervised Learning is here posed as striving for simplicity...... in the decompositions. Thus, it is demonstrated how a wide range of decomposition methods explicitly or implicitly strive to attain this goal. Applications of the derived decompositions are given ranging from multi-media analysis of image and sound data, analysis of biomedical data such as electroencephalography...
Directory of Open Access Journals (Sweden)
Liao Li
2010-10-01
Full Text Available Abstract Background Protein-protein interaction (PPI plays essential roles in cellular functions. The cost, time and other limitations associated with the current experimental methods have motivated the development of computational methods for predicting PPIs. As protein interactions generally occur via domains instead of the whole molecules, predicting domain-domain interaction (DDI is an important step toward PPI prediction. Computational methods developed so far have utilized information from various sources at different levels, from primary sequences, to molecular structures, to evolutionary profiles. Results In this paper, we propose a computational method to predict DDI using support vector machines (SVMs, based on domains represented as interaction profile hidden Markov models (ipHMM where interacting residues in domains are explicitly modeled according to the three dimensional structural information available at the Protein Data Bank (PDB. Features about the domains are extracted first as the Fisher scores derived from the ipHMM and then selected using singular value decomposition (SVD. Domain pairs are represented by concatenating their selected feature vectors, and classified by a support vector machine trained on these feature vectors. The method is tested by leave-one-out cross validation experiments with a set of interacting protein pairs adopted from the 3DID database. The prediction accuracy has shown significant improvement as compared to InterPreTS (Interaction Prediction through Tertiary Structure, an existing method for PPI prediction that also uses the sequences and complexes of known 3D structure. Conclusions We show that domain-domain interaction prediction can be significantly enhanced by exploiting information inherent in the domain profiles via feature selection based on Fisher scores, singular value decomposition and supervised learning based on support vector machines. Datasets and source code are freely available on
Xin, Xuegang; Wang, Di; Han, Jijun; Feng, Yanqiu; Feng, Qianjin; Chen, Wufan
2012-07-01
The numerical optimization of a three-channel radiofrequency (RF) coil with a physical aperture for the open, vertical-field, MR-guided, focused ultrasound surgery (MRgFUS) system using the hybrid method of moment (MoM)/finite difference time domain (FDTD) method is reported. The numerical simulation of the current density distribution on an RF coil with a complicated irregular structure was performed using MoM. The electromagnetic field simulation containing the full coil-tissue interactions within the region of interest was accomplished using the FDTD method. Huygens' equivalent box with six surfaces smoothly connected the MoM and FDTD method. An electromagnetic model of the human pelvic region was reconstructed and loaded in the FDTD zone to optimize the three-channel RF coil and compensate for the lower sensitivity at the vertical field. In addition, the numerical MoM was used to model the resonance, decoupling and impedance matching of the RF coil in compliance with engineering practices. A prototype RF coil was constructed to verify the simulation results. The results demonstrate that the signal-to-noise ratio and the homogeneity of the B(1) field were both greatly improved compared with previously published results.
Institute of Scientific and Technical Information of China (English)
王建勋; 刘会金; 韩丰收; 王占雷
2012-01-01
To detect interharmonics whose frequencies are near to those of harmonics and fundamental harmonic, a hybrid time-frequency domain method is proposed to analyze harmonics and interharmonics. Firstly, the detection of harmonics and fundamental harmonic in time-domain is performed by parallel enhanced phase-locked loop (PLL) structure, in which the main PLL is used to measure fundamental component signal with higher amplitude and the measured fundamental component is input to parallel sub-PLL structure to segregate harmonic components; then in frequency-domain the post-segregation signals, in which only interharmonics are contained, are analyzed by interpolated fast Fourier transformation (IFFT), thus accurate parameters of interharmonics whose frequencies are near to those of harmonics and fundamental harmonic can be attained when the spectral leakage of harmonics and fundamental harmonic are excluded. An online monitoring platform of harmonics and fundamental harmonic based on the proposed method is implemented by Lab VIEW software, and both results from experiments and simulation show that the proposed method is effective.%为了检测靠近基波和谐波的间谐波,提出了一种时频混合方法来分析谐波和间谐波.首先在时域上通过并联的加强锁相环结构进行基波与谐波检测,该结构通过主锁相环测量幅值较大的基频分量,并将测得的基频输入到并行的子锁相环结构以完成对各谐波分量的分离;然后在频域上对分离所得的只含间谐波的信号使用插值快速傅里叶变换的方法进行分析,能在排除基波与谐波频谱泄漏影响的情况下得到靠近基波和谐波的间谐波的精确参数.在LabVIEW上实现了基于所提方法的谐波、间谐波在线监测平台,仿真和实验证明了所提方法的有效性.
Decomposition of the Security Requirements for Connected Information Domains
Schotanus, H.A.; Boonstra, D.; Broenink, E.G.
2011-01-01
The introduction of network enabled capabilities (NEC) changed the way defence organisations look at their IT infrastructure. Finding the right balance between security and duty-to-share has proven to be a difficult challenge. The situations are complex and may lead to high security requirements t
Multigrid and multilevel domain decomposition for unstructured grids
Energy Technology Data Exchange (ETDEWEB)
Chan, T.; Smith, B.
1994-12-31
Multigrid has proven itself to be a very versatile method for the iterative solution of linear and nonlinear systems of equations arising from the discretization of PDES. In some applications, however, no natural multilevel structure of grids is available, and these must be generated as part of the solution procedure. In this presentation the authors will consider the problem of generating a multigrid algorithm when only a fine, unstructured grid is given. Their techniques generate a sequence of coarser grids by first forming an approximate maximal independent set of the vertices and then applying a Cavendish type algorithm to form the coarser triangulation. Numerical tests indicate that convergence using this approach can be as fast as standard multigrid on a structured mesh, at least in two dimensions.
Decomposition of the Security Requirements for Connected Information Domains
Schotanus, H.A.; Boonstra, D.; Broenink, E.G.
2011-01-01
The introduction of network enabled capabilities (NEC) changed the way defence organisations look at their IT infrastructure. Finding the right balance between security and duty-to-share has proven to be a difficult challenge. The situations are complex and may lead to high security requirements t
Thermal decomposition of lutetium propionate
DEFF Research Database (Denmark)
Grivel, Jean-Claude
2010-01-01
The thermal decomposition of lutetium(III) propionate monohydrate (Lu(C2H5CO2)3·H2O) in argon was studied by means of thermogravimetry, differential thermal analysis, IR-spectroscopy and X-ray diffraction. Dehydration takes place around 90 °C. It is followed by the decomposition of the anhydrous ...... of the oxycarbonate to the rare-earth oxide proceeds in a different way, which is here reminiscent of the thermal decomposition path of Lu(C3H5O2)·2CO(NH2)2·2H2O...
AUTONOMOUS GAUSSIAN DECOMPOSITION
Energy Technology Data Exchange (ETDEWEB)
Lindner, Robert R.; Vera-Ciro, Carlos; Murray, Claire E.; Stanimirović, Snežana; Babler, Brian [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Heiles, Carl [Radio Astronomy Lab, UC Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States); Hennebelle, Patrick [Laboratoire AIM, Paris-Saclay, CEA/IRFU/SAp-CNRS-Université Paris Diderot, F-91191 Gif-sur Yvette Cedex (France); Goss, W. M. [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville, Socorro, NM 87801 (United States); Dickey, John, E-mail: rlindner@astro.wisc.edu [University of Tasmania, School of Maths and Physics, Private Bag 37, Hobart, TAS 7001 (Australia)
2015-04-15
We present a new algorithm, named Autonomous Gaussian Decomposition (AGD), for automatically decomposing spectra into Gaussian components. AGD uses derivative spectroscopy and machine learning to provide optimized guesses for the number of Gaussian components in the data, and also their locations, widths, and amplitudes. We test AGD and find that it produces results comparable to human-derived solutions on 21 cm absorption spectra from the 21 cm SPectral line Observations of Neutral Gas with the EVLA (21-SPONGE) survey. We use AGD with Monte Carlo methods to derive the H i line completeness as a function of peak optical depth and velocity width for the 21-SPONGE data, and also show that the results of AGD are stable against varying observational noise intensity. The autonomy and computational efficiency of the method over traditional manual Gaussian fits allow for truly unbiased comparisons between observations and simulations, and for the ability to scale up and interpret the very large data volumes from the upcoming Square Kilometer Array and pathfinder telescopes.
A Hybrid Algorithm of Automatic Domain Concept Taxonomy Construction%一种混合的领域概念分类体系自动构建算法
Institute of Scientific and Technical Information of China (English)
罗年洁; 吕钊
2014-01-01
领域概念分类体系自动构建在人工智能、自然语言处理和信息检索等领域具有重要作用，但现有研究较多关注通用知识，面向特定领域的研究较少，且存在领域概念间关系抽取准确率以及自动构建算法效率较低等问题。为此，提出一种混合的领域概念分类体系自动构建算法，该算法主要包括领域概念间关系抽取模块和分类体系构建模块。领域概念间关系抽取模块设计考虑中文自身的特点，采取句法树和基于规则相结合的方法，以提高抽取领域概念间关系的查准率和查全率；分类体系构建模块设计采取改进的BRT算法，从而在降低算法复杂度的同时，提高领域分类体系构建的查准率。在通信、金融和计算机领域的实验结果均表明，与BRT算法相比，该算法的构建效果较好，查准率最高可达到89.3%。%Domain concept taxonomy automatic construction plays an important role in artificial intelligence,natural language processing and information retrieval. Existing approaches pay more attention on common knowledge, while there are fewer reports about domain concepts. Two main challenges of domain concept taxonomy automatic construction are identifying relationships between concepts and less efficiency of current algorithms. In this paper,a Hybrid algorithm of Automatic Domain concept Taxonomy construction(HADT) is proposed,which has two main modules:extracting relationships between domain concepts and automatic taxonomy construction. Considering Chinese characteristics,the first module uses syntax tree method and rule-based method together,to get the aim of higher precision and higher recall. The second module uses an improved BRT algorithm to reduce time complexity and to improve taxonomy construction precision. The experiments conducted on three datasets of mobile,financial and computer show the HADT algorithm is effectiveness compared with the BRT algorithm
Institute of Scientific and Technical Information of China (English)
张翌晖; 王贺; 胡志坚; 王凯; 黄东山; 宁文辉; 张承学
2014-01-01
This paper proposes a new short-term combination prediction model of wind speed by means of ensemble empirical mode decomposition (EEMD) and improved extreme learning machine (IELM). Firstly, wind speed series is decomposed into several components with different frequency bands by EEMD to reduce the series non-stationary. Secondly, the phase space of each component is reconstructed in order to solve the randomness and component information lost of input dimensionality selection of extreme learning machine, and then an IELM model of each component is established. Finally, the forecast result of each component is superimposed to get the final result. The simulation result verifies that the hybrid model has higher prediction accuracy of wind speed.%提出一种基于集合经验模态分解（Ensemble empirical mode decomposition）和改进极限学习机（Improved Extreme Learning Machine，IELM）的新型短期风速组合预测模型。采用集合经验模态分解将风速序列分解成不同频段的分量，以降低序列的非平稳性。使用改进极限学习机对各分量分别建模预测，为避免极限学习机输入维数选取的随意性和分量信息丢失等问题，先对各分量重构相空间，最后将各分量预测结果叠加得到最终预测结果。实例研究表明，所提的组合预测模型具有较高的预测精度。
Visualizing domain wall and reverse domain superconductivity.
Iavarone, M; Moore, S A; Fedor, J; Ciocys, S T; Karapetrov, G; Pearson, J; Novosad, V; Bader, S D
2014-08-28
In magnetically coupled, planar ferromagnet-superconductor (F/S) hybrid structures, magnetic domain walls can be used to spatially confine the superconductivity. In contrast to a superconductor in a uniform applied magnetic field, the nucleation of the superconducting order parameter in F/S structures is governed by the inhomogeneous magnetic field distribution. The interplay between the superconductivity localized at the domain walls and far from the walls leads to effects such as re-entrant superconductivity and reverse domain superconductivity with the critical temperature depending upon the location. Here we use scanning tunnelling spectroscopy to directly image the nucleation of superconductivity at the domain wall in F/S structures realized with Co-Pd multilayers and Pb thin films. Our results demonstrate that such F/S structures are attractive model systems that offer the possibility to control the strength and the location of the superconducting nucleus by applying an external magnetic field, potentially useful to guide vortices for computing application.
Decomposition of indwelling EMG signals
2008-01-01
Decomposition of indwelling electromyographic (EMG) signals is challenging in view of the complex and often unpredictable behaviors and interactions of the action potential trains of different motor units that constitute the indwelling EMG signal. These phenomena create a myriad of problem situations that a decomposition technique needs to address to attain completeness and accuracy levels required for various scientific and clinical applications. Starting with the maximum a posteriori probab...
TREE DECOMPOSITIONS OF MULTIGRAPHS
Institute of Scientific and Technical Information of China (English)
SHI Minyong
1999-01-01
For a graph G, ifE(G) can be partitioned into several pairwise disjointsets as { E1, E2,……,El} such thatthe subgraph induced by Ei is a tree of orderki, (i=1,2, ……, l), then G is said to have a {k1,k2,……, kl}-tree-decomposition, denoted by {k1,k2,……, kl}∈G.For k≥1 and l≥0, a collection(G)(k,l) is the setof multigraphs such that G∈(G)(k,l) if and only if ε(G) = k(|G|-1)-l and ε(H)≤max{(k-1)(|H|-1), k(|H|-1)-l} for any subgraph H of G.We prove that (1) If k≥2, 0≤l≤3 and G∈(G)(k,l) of order n≥l+1, then {n,n,……, n-l}∈ G. (2) If k≥2 and G∈(G)(k,2) oforder n≥3, then {n,n,……, n,n-2}∈G and {n,n,……, n,n-1,n-1}∈G. (3) If k3 and G∈(G)(k,3) oforder n≥4, then {n,n,……, n,n-3}∈G ,{ n,n,……, n,n-1,n-2}∈ G and {n,n, ……, n,n-1,n-1,n-1}∈G.
Decomposition of indwelling EMG signals.
Nawab, S Hamid; Wotiz, Robert P; De Luca, Carlo J
2008-08-01
Decomposition of indwelling electromyographic (EMG) signals is challenging in view of the complex and often unpredictable behaviors and interactions of the action potential trains of different motor units that constitute the indwelling EMG signal. These phenomena create a myriad of problem situations that a decomposition technique needs to address to attain completeness and accuracy levels required for various scientific and clinical applications. Starting with the maximum a posteriori probability classifier adapted from the original precision decomposition system (PD I) of LeFever and De Luca (25, 26), an artificial intelligence approach has been used to develop a multiclassifier system (PD II) for addressing some of the experimentally identified problem situations. On a database of indwelling EMG signals reflecting such conditions, the fully automatic PD II system is found to achieve a decomposition accuracy of 86.0% despite the fact that its results include low-amplitude action potential trains that are not decomposable at all via systems such as PD I. Accuracy was established by comparing the decompositions of indwelling EMG signals obtained from two sensors. At the end of the automatic PD II decomposition procedure, the accuracy may be enhanced to nearly 100% via an interactive editor, a particularly significant fact for the previously indecomposable trains.
Numeric Modified Adomian Decomposition Method for Power System Simulations
Energy Technology Data Exchange (ETDEWEB)
Dimitrovski, Aleksandar D [ORNL; Simunovic, Srdjan [ORNL; Pannala, Sreekanth [ORNL
2016-01-01
This paper investigates the applicability of numeric Wazwaz El Sayed modified Adomian Decomposition Method (WES-ADM) for time domain simulation of power systems. WESADM is a numerical method based on a modified Adomian decomposition (ADM) technique. WES-ADM is a numerical approximation method for the solution of nonlinear ordinary differential equations. The non-linear terms in the differential equations are approximated using Adomian polynomials. In this paper WES-ADM is applied to time domain simulations of multimachine power systems. WECC 3-generator, 9-bus system and IEEE 10-generator, 39-bus system have been used to test the applicability of the approach. Several fault scenarios have been tested. It has been found that the proposed approach is faster than the trapezoidal method with comparable accuracy.
The inner structure of empirical mode decomposition
Wang, Yung-Hung; Young, Hsu-Wen Vincent; Lo, Men-Tzung
2016-11-01
The empirical mode decomposition (EMD) is a nonlinear method that is truly adaptive with good localization property in the time domain for analyzing non-stationary complex data. The EMD has been proven useful in a wide range of applications. However, due to the nonlinear and complex nature of the sifting process, the most essential step of the EMD, a firm mathematical foundation or a transparent physical description are still lacked for EMD. Here, we embark on constructing a mathematical theory of the sifting operator. We first show that the sifting operator can be expressed as the data plus the sum of the responses to the impulses (multiplied by the data value) at the extrema. Such an expression of the sifting operator is then used to investigate the adaptive nature and the localizing effect of the EMD. Alternatively, the sifting operator can also be represented by a sifting matrix, which depends nonlinearly on the extrema distribution. Based on the eigen-decomposition of the sifting matrix, the transfer function of the sifting process is analyzed. Finally we answer what an intrinsic mode function (IMF) is from the wave perspective by exploring the physical basis of the IMFs.
Covariance NMR spectroscopy by singular value decomposition.
Trbovic, Nikola; Smirnov, Serge; Zhang, Fengli; Brüschweiler, Rafael
2004-12-01
Covariance NMR is demonstrated for homonuclear 2D NMR data collected using the hypercomplex and TPPI methods. Absorption mode 2D spectra are obtained by application of the square-root operation to the covariance matrices. The resulting spectra closely resemble the 2D Fourier transformation spectra, except that they are fully symmetric with the spectral resolution along both dimensions determined by the favorable resolution achievable along omega2. An efficient method is introduced for the calculation of the square root of the covariance spectrum by applying a singular value decomposition (SVD) directly to the mixed time-frequency domain data matrix. Applications are shown for 2D NOESY and 2QF-COSY data sets and computational benchmarks are given for data matrix dimensions typically encountered in practice. The SVD implementation makes covariance NMR amenable to routine applications.
Page, P R
2003-01-01
We review the status of hybrid baryons. The only known way to study hybrids rigorously is via excited adiabatic potentials. Hybrids can be modelled by both the bag and flux-tube models. The low-lying hybrid baryon is N 1/2^+ with a mass of 1.5-1.8 GeV. Hybrid baryons can be produced in the glue-rich processes of diffractive gamma N and pi N production, Psi decays and p pbar annihilation.
Real interest parity decomposition
Directory of Open Access Journals (Sweden)
Alex Luiz Ferreira
2009-09-01
Full Text Available The aim of this paper is to investigate the general causes of real interest rate differentials (rids for a sample of emerging markets for the period of January 1996 to August 2007. To this end, two methods are applied. The first consists of breaking the variance of rids down into relative purchasing power pariety and uncovered interest rate parity and shows that inflation differentials are the main source of rids variation; while the second method breaks down the rids and nominal interest rate differentials (nids into nominal and real shocks. Bivariate autoregressive models are estimated under particular identification conditions, having been adequately treated for the identified structural breaks. Impulse response functions and error variance decomposition result in real shocks as being the likely cause of rids.O objetivo deste artigo é investigar as causas gerais dos diferenciais da taxa de juros real (rids para um conjunto de países emergentes, para o período de janeiro de 1996 a agosto de 2007. Para tanto, duas metodologias são aplicadas. A primeira consiste em decompor a variância dos rids entre a paridade do poder de compra relativa e a paridade de juros a descoberto e mostra que os diferenciais de inflação são a fonte predominante da variabilidade dos rids; a segunda decompõe os rids e os diferenciais de juros nominais (nids em choques nominais e reais. Sob certas condições de identificação, modelos autorregressivos bivariados são estimados com tratamento adequado para as quebras estruturais identificadas e as funções de resposta ao impulso e a decomposição da variância dos erros de previsão são obtidas, resultando em evidências favoráveis a que os choques reais são a causa mais provável dos rids.
Bouton, Sophie; Viau, Laure; Lelièvre, Eric; Limami, Anis M
2005-03-01
A gene MtPPRD1, encoding a protein of 132 amino acids containing a proline-rich domain (PRD), has been revealed by suppressive subtractive hybridization (SSH) with two mRNA populations of embryo axes harvested immediately before and after radicle emergence. Although at the protein level MtPPRD1 showed low homology with plant lipid transfer proteins (LTPs), it did exhibit the eight cysteine residues conserved in all plant LTPs, a characteristic signature that allows the formation of a hydrophobic cavity adapted for loading hydrophobic molecules. Expression studies of MtPPRD1 have been carried out by quantitative real time RT-PCR throughout germination and post-germination processes in control seeds and seeds in which germination was delayed by abscisic acid (ABA) or the glutamine synthetase inhibitor methionine sulphoximine (MSX) treatments. The results showed that MtPPRD1 expression is developmentally regulated, induced in the embryo axis immediately before radicle emergence, reaches its maximum expression and declines during the early post-germination phase. Organ specificity studies showed that, except for a low and probably constitutive expression in roots, MtPPRD1 is specifically expressed in the embryo axis. Based on both experimental and in silico studies several putative roles are proposed for MtPPRD1 in Medicago truncatula, this protein can intervene (i) as an LTP in membrane biogenesis and regulation of the intracellular fatty acid pool by binding and transferring fatty acids and phospholipids between membranes, (ii) in the control of a developmental process specific to late germination and to early phases of post-germination, and (iii) and/or pathogen defence.
Techno-economic comparison of series hybrid, plug-in hybrid, fuel cell and regular cars
van Vliet, O.P.R.|info:eu-repo/dai/nl/288519361; Kruithof, T.; Turkenburg, W.C.|info:eu-repo/dai/nl/073416355; Faaij, A.P.C.|info:eu-repo/dai/nl/10685903X
2010-01-01
We examine the competitiveness of series hybrid compared to fuel cell, parallel hybrid, and regular cars. We use public domain data to determine efficiency, fuel consumption, total costs of ownership and greenhouse gas emissions resulting from drivetrain choices. The series hybrid drivetrain can be
Techno-economic comparison of series hybrid, plug-in hybrid, fuel cell and regular cars
van Vliet, O.P.R.; Kruithof, T.; Turkenburg, W.C.; Faaij, A.P.C.
2010-01-01
We examine the competitiveness of series hybrid compared to fuel cell, parallel hybrid, and regular cars. We use public domain data to determine efficiency, fuel consumption, total costs of ownership and greenhouse gas emissions resulting from drivetrain choices. The series hybrid drivetrain can be
Decomposition of Fuzzy Soft Sets with Finite Value Spaces
Jun, Young Bae
2014-01-01
The notion of fuzzy soft sets is a hybrid soft computing model that integrates both gradualness and parameterization methods in harmony to deal with uncertainty. The decomposition of fuzzy soft sets is of great importance in both theory and practical applications with regard to decision making under uncertainty. This study aims to explore decomposition of fuzzy soft sets with finite value spaces. Scalar uni-product and int-product operations of fuzzy soft sets are introduced and some related properties are investigated. Using t-level soft sets, we define level equivalent relations and show that the quotient structure of the unit interval induced by level equivalent relations is isomorphic to the lattice consisting of all t-level soft sets of a given fuzzy soft set. We also introduce the concepts of crucial threshold values and complete threshold sets. Finally, some decomposition theorems for fuzzy soft sets with finite value spaces are established, illustrated by an example concerning the classification and rating of multimedia cell phones. The obtained results extend some classical decomposition theorems of fuzzy sets, since every fuzzy set can be viewed as a fuzzy soft set with a single parameter. PMID:24558342
Decomposition of fuzzy soft sets with finite value spaces.
Feng, Feng; Fujita, Hamido; Jun, Young Bae; Khan, Madad
2014-01-01
The notion of fuzzy soft sets is a hybrid soft computing model that integrates both gradualness and parameterization methods in harmony to deal with uncertainty. The decomposition of fuzzy soft sets is of great importance in both theory and practical applications with regard to decision making under uncertainty. This study aims to explore decomposition of fuzzy soft sets with finite value spaces. Scalar uni-product and int-product operations of fuzzy soft sets are introduced and some related properties are investigated. Using t-level soft sets, we define level equivalent relations and show that the quotient structure of the unit interval induced by level equivalent relations is isomorphic to the lattice consisting of all t-level soft sets of a given fuzzy soft set. We also introduce the concepts of crucial threshold values and complete threshold sets. Finally, some decomposition theorems for fuzzy soft sets with finite value spaces are established, illustrated by an example concerning the classification and rating of multimedia cell phones. The obtained results extend some classical decomposition theorems of fuzzy sets, since every fuzzy set can be viewed as a fuzzy soft set with a single parameter.
Institute of Scientific and Technical Information of China (English)
张全; 李双田
2015-01-01
In the singular value decomposition de-noising algorithm,the choice of the effective rank order is of great impor-tance to influence the performance of the de-noising algorithm.To select a more accurate effective rank order,this paper studied the difference of singular value sequence,proposed a new method to determine the effective rank order,applied it to de-noise the time domain transient electromagnetic signal,and raised the output signal-to-noise ratio.Differs from exist-ing rank-determining algorithms,the proposed method cares about the peaks but not the maximum of the normalized differ-ence,chooses the appropriate peak and determines the rank order together with the difference ratio of the singular value se-quence.In simulation experiments we found that for two similar peaks of the singular value difference,the one whose differ-ence ratio is smaller,is more appropriate to be the effective rank order.The proposed method can keep the waveform fea-ture of the desired signal and decrease distortion while de-noising.%奇异值分解降噪算法中，有效秩阶次的判断对降噪算法的性能的影响至关重要。为选取更准确的有效秩阶次，本文研究了奇异值序列的差分，提出判断奇异值分解重构的有效秩阶次的新方法，并应用其对时间域瞬变电磁信号降噪，提高输出信号的信噪比。与现有判断有效秩阶次的算法不同，本文算法考察奇异值序列的归一化差分的峰值而不是最大值，通过选择归一化差分的合适峰值，并综合差分比序列以判断阶次。实验中发现，对于两个大小相近的尖峰，其中差分比小的，更适合作为有效秩阶次。本文算法在降噪的同时，能较好地保留有用信号的波形特征，减小失真。
Institute of Scientific and Technical Information of China (English)
陈刚; 吴小辰; 柳勇军; 李鹏; 廖瑞金; 王予疆; 何潜
2011-01-01
Frequency Domain Decomposition(FDD) is introduced to identify low-frequency oscillation modes by analysis of steady-state ambient measurements in power system and some modifications to FDD are made.The relation expression between maximum singular value of PSD matrix and system eigenvalue under poorly damped mode is presented by detailed derivation of the relations among frequency response funcfion(FRF), output power spectral density (PSD), and system eigenvalues.Modal Amplitude Coherence (MAC) is used to determine mode area size in the neighborhood of peak point on maximum SVD curve.Finally, the exact modal frequency and damping ratio can be estimated using least square method.The technique is illustrated on linear time-invariant system, WECC 9-bus system and ambient PMU measurements, to show its effectiveness.The suggested method is suitable for identification of poorly damped oscillatory modes, and is robust to noise, and has important value for real-time application.%对广域稳态量测信号将频域分解方法引入电网低频振荡模式辨识并进行了改进完善.推导了系统的频响函数、输出功率谱密度矩阵、特征量之间的关系,给出了弱阻尼模式下功率谱密度矩阵的最大奇异值与特征量之间的关系表达式;采用模态幅值相干系数以确定奇异值曲线谱峰附近单模态区域大小,最后采用最小二乘方法求取准确的模式频率和阻尼系数.线性时不变系统时域仿真、WECC 9节点系统时域仿真以及实测PMU数据分析表明,所提方法适用于弱阻尼振荡模式辨识,对噪声具有较强鲁棒性,是一种极具实用价值的在线应用方法.
Piecewise-adaptive decomposition methods
Energy Technology Data Exchange (ETDEWEB)
Ramos, J.I. [Room I-320-D, E.T.S. Ingenieros Industriales, Universidad de Malaga, Plaza El Ejido, s/n, 29013 Malaga (Spain)], E-mail: jirs@lcc.uma.es
2009-05-30
Piecewise-adaptive decomposition methods are developed for the solution of nonlinear ordinary differential equations. These methods are based on some theorems that show that Adomian's decomposition method is a homotopy perturbation technique and coincides with Taylor's series expansions for autonomous ordinary differential equations. Piecewise-decomposition methods provide series solutions in intervals which are subject to continuity conditions at the end points of each interval, and their adaption is based on the use of either a fixed number of approximants and a variable step size, a variable number of approximants and a fixed step size or a variable number of approximants and a variable step size. It is shown that the appearance of noise terms in the decomposition method is related to both the differential equation and the manner in which the homotopy parameter is introduced, especially for the Lane-Emden equation. It is also shown that, in order to avoid the use of numerical quadrature, there is a simple way of introducing the homotopy parameter in the two first-order ordinary differential equations that correspond to the second-order Thomas-Fermi equation. It is also shown that the piecewise homotopy perturbation methods presented here provide more accurate results than a modified Adomian decomposition technique which makes use of Pade approximants and the homotopy analysis method, for the Thomas-Fermi equation.
A multiconfigurational hybrid density-functional theory
DEFF Research Database (Denmark)
Sharkas, Kamal; Savin, Andreas; Jensen, Hans Jørgen Aagaard
2012-01-01
We propose a multiconfigurational hybrid density-functional theory which rigorously combines a multiconfiguration self-consistent-field calculation with a density-functional approximation based on a linear decomposition of the electron-electron interaction. This gives a straightforward extension ...
A multiconfigurational hybrid density-functional theory
DEFF Research Database (Denmark)
Sharkas, Kamal; Savin, Andreas; Jensen, Hans Jørgen Aagaard
2012-01-01
We propose a multiconfigurational hybrid density-functional theory which rigorously combines a multiconfiguration self-consistent-field calculation with a density-functional approximation based on a linear decomposition of the electron-electron interaction. This gives a straightforward extension ...
Institute of Scientific and Technical Information of China (English)
沈金松; 汪轩; 魏帅帅; 李曼
2015-01-01
In marine controlled-source electromagnetic (MCSEM)exploration,the influence on the EM response of the airwave has been paid great attention by the industry and the air wave is one kind of EM signal from the horizontal electric dipole (HED)source that is reflected from or travels along the air-sea interface and return back to receivers.In shallow water domains,the airwave dominates over the effective signal from seabed sediments, and makes it very difficult to identify the hydrocarbon reservoirs.On the basis of the layer model,we have derived airwave expression of half space resistivity model by using the mode decomposition theory of the EM field and the air wave in the sea water layer is approximately expressed as a series of wave reverberations that travel down and backward between the sea surface and the seabed.According to the propagations of EM field near sources and receivers,we have obtained airwave expression of a finite water layer.In order to compare the effectiveness of the various air wave mitigation methods,we have adopted the decomposition method of EM fields into upgoing and downgoing components,and have acuired larger anomaly of several times than that of the raw EM field above the resistive formation,and indicated the favorable effect of airwave attenuation by using of wave separation. Finally, simulation results of electromagnetic responses from different background and reservoir models have been used to check the effectiveness and adaptability of the two air wave mitigation methods of wave reverberations approximation and wave field decomposition,numerical results show that for model of horizontal layers,the latter is more effective,however,the former is applicable to rugged sea floor formation and the latter only fits for horizontal layers.%可控源海洋电磁(MCSEM)勘探中空气波对海底电磁响应的影响已为业界所重视，它是由水平电偶极子源发射的电磁信号沿空气海水界面传播与来自海底地层的有
Energy Technology Data Exchange (ETDEWEB)
Sitaraman, Hariswaran [National Renewable Energy Lab. (NREL), Golden, CO (United States); Grout, Ray [National Renewable Energy Lab. (NREL), Golden, CO (United States)
2015-10-30
The load balancing strategies for hybrid solvers that involve grid based partial differential equation solution coupled with particle tracking are presented in this paper. A typical Message Passing Interface (MPI) based parallelization of grid based solves are done using a spatial domain decomposition while particle tracking is primarily done using either of the two techniques. One of the techniques is to distribute the particles to MPI ranks to whose grid they belong to while the other is to share the particles equally among all ranks, irrespective of their spatial location. The former technique provides spatial locality for field interpolation but cannot assure load balance in terms of number of particles, which is achieved by the latter. The two techniques are compared for a case of particle tracking in a homogeneous isotropic turbulence box as well as a turbulent jet case. We performed a strong scaling study for more than 32,000 cores, which results in particle densities representative of anticipated exascale machines. The use of alternative implementations of MPI collectives and efficient load equalization strategies are studied to reduce data communication overheads.
Chen, Linfei; Gao, Xiong; Chen, Xudong; He, Bingyu; Liu, Jingyu; Li, Dan
2016-04-01
In this paper, a new optical image cryptosystem is proposed based on two-beam coherent superposition and unequal modulus decomposition. Different from the equal modulus decomposition or unit vector decomposition, the proposed method applies common vector decomposition to accomplish encryption process. In the proposed method, the original image is firstly Fourier transformed and the complex function in spectrum domain will be obtained. The complex distribution is decomposed into two vector components with unequal amplitude and phase by the common vector decomposition method. Subsequently, the two components are modulated by two random phases and transformed from spectrum domain to spatial domain, and amplitude parts are extracted as encryption results and phase parts are extracted as private keys. The advantages of the proposed cryptosystem are: four different phase and amplitude information created by the method of common vector decomposition strengthens the security of the cryptosystem, and it fully solves the silhouette problem. Simulation results are presented to show the feasibility and the security of the proposed cryptosystem.
Distributed k-Core Decomposition
Montresor, Alberto; Miorandi, Daniele
2011-01-01
Among the novel metrics used to study the relative importance of nodes in complex networks, k-core decomposition has found a number of applications in areas as diverse as sociology, proteinomics, graph visualization, and distributed system analysis and design. This paper proposes new distributed algorithms for the computation of the k-core decomposition of a network, with the purpose of (i) enabling the run-time computation of k-cores in "live" distributed systems and (ii) allowing the decomposition, over a set of connected machines, of very large graphs, that cannot be hosted in a single machine. Lower bounds on the algorithms complexity are given, and an exhaustive experimental analysis on real-world graphs is provided.
Thermal decomposition of ammonium hexachloroosmate
DEFF Research Database (Denmark)
Asanova, T I; Kantor, Innokenty; Asanov, I. P.
2016-01-01
Structural changes of (NH4)2[OsCl6] occurring during thermal decomposition in a reduction atmosphere have been studied in situ using combined energy-dispersive X-ray absorption spectroscopy (ED-XAFS) and powder X-ray diffraction (PXRD). According to PXRD, (NH4)2[OsCl6] transforms directly...... to metallic Os without the formation of any crystalline intermediates but through a plateau where no reactions occur. XANES and EXAFS data by means of Multivariate Curve Resolution (MCR) analysis show that thermal decomposition occurs with the formation of an amorphous intermediate {OsCl4}x with a possible...... polymeric structure. Being revealed for the first time the intermediate was subjected to determine the local atomic structure around osmium. The thermal decomposition of hexachloroosmate is much more complex and occurs within a minimum two-step process, which has never been observed before....
Limits to acoustic sensing and modal decomposition using FBGs
Norman, Patrick; Davis, Claire; Rosalie, Cédric; Rajic, Nik
2016-04-01
Lamb-wave based structural health monitoring (SHM) approaches are typically constrained to operate below the first cut-off frequency to simplify the interpretation of the wave field in the time-domain. However from a diagnostic perspective, it is desirable to unlock the additional information encoded in the higher-order Lamb wave spectrum. Wave-mode decomposition is necessary for the extraction of useful information from multi-modal acoustic wave fields, which requires spatially dense sampling over the field. The instrument of choice for this task is the laser Doppler vibrometer, which is capable of producing detailed spectral decompositions. However vibrometry is not suited to in-situ measurement for SHM. Fibre Bragg gratings (FBGs) are capable of sensing Lamb waves and detection of higher order modes using FBGs has been previously demonstrated. The ability to multiplex multiple short-length gratings along a single fibre to create an FBG array gives rise to an in-situ sensor with sufficiently dense spatial sampling of an acoustic wave field to perform useful wave-mode decomposition. This paper explores some of the fundamental limits to modal decomposition resolution and bandwidth that exist for such sensors. Potential sources of noise and distortion encountered due to limitations of the sensor fabrication and interrogation methods are also discussed. In addition, modal decomposition of Lamb waves with frequencies up to 1.25 MHz is demonstrated in a laboratory experiment using an array of sixteen ~1 mm long gratings bonded to an aluminium plate. At least four modes are distinguishable in the resulting spectral decomposition.
The ecology of carrion decomposition
Carrion, or the remains of dead animals, is something that most people would like to avoid. It is visually unpleasant, emits foul odors, and may be the source of numerous pathogens. Decomposition of carrion, however, provides a unique opportunity for scientists to investigate how nutrients cycle t...
Microbial interactions during carrion decomposition
This addresses the microbial ecology of carrion decomposition in the age of metagenomics. It describes what is known about the microbial communities on carrion, including a brief synopsis about the communities on other organic matter sources. It provides a description of studies using state-of-the...
Wavefront reconstruction by modal decomposition
CSIR Research Space (South Africa)
Schulze, C
2012-08-01
Full Text Available We propose a new method to determine the wavefront of a laser beam based on modal decomposition by computer-generated holograms. The hologram is encoded with a transmission function suitable for measuring the amplitudes and phases of the modes...
Stepwise decomposition in controlpath synthesis
Berg, ten A.J.W.M.
1990-01-01
A method is presented for the synthesis of the microarchitecture of controlpaths. This method is called stepwise decomposition. It focuses primarily on controlpaths of instruction set processors, however it is also applicable for more general Finite State Machine synthesis. Many of the current contr
Stepwise decomposition in controlpath synthesis
ten Berg, A.J.W.M.; ten Berg, A.J.W.M.
1990-01-01
A method is presented for the synthesis of the microarchitecture of controlpaths. This method is called stepwise decomposition. It focuses primarily on controlpaths of instruction set processors, however it is also applicable for more general Finite State Machine synthesis. Many of the current contr
Modular Decomposition of Boolean Functions
J.C. Bioch (Cor)
2002-01-01
textabstractModular decomposition is a thoroughly investigated topic in many areas such as switching theory, reliability theory, game theory and graph theory. Most appli- cations can be formulated in the framework of Boolean functions. In this paper we give a uni_ed treatment of modular decompositio
Modular Decomposition of Boolean Functions
J.C. Bioch (Cor)
2002-01-01
textabstractModular decomposition is a thoroughly investigated topic in many areas such as switching theory, reliability theory, game theory and graph theory. Most appli- cations can be formulated in the framework of Boolean functions. In this paper we give a uni_ed treatment of modular
Thermal Decomposition of Dicyclopentadienylarylvanadium Compounds
Boekel, C.P.; Jelsma, A.; Teuben, J.H.; Liefde Meijer, H.J. de
1977-01-01
The thermolysis of compounds of the type Cp2VR (R = aryl) in the solid state has been studied. A distinct increase in thermal stability is observed upon substitution of the ortho-position of the aryl group. Thermal decomposition occurs with formation of RH, Cp2V, a vanadocene homologue with the
Multiple Descriptions Using Sparse Decompositions
DEFF Research Database (Denmark)
Jensen, Tobias Lindstrøm; Østergaard, Jan; Dahl, Joachim
2010-01-01
In this paper, we consider the design of multiple descriptions (MDs) using sparse decompositions. In a description erasure channel only a subset of the transmitted descriptions is received. The MD problem concerns the design of the descriptions such that they individually approximate the source...
Energy Technology Data Exchange (ETDEWEB)
West, J.G.W. [Electrical Machines (United Kingdom)
1997-07-01
The reasons for adopting hybrid vehicles result mainly from the lack of adequate range from electric vehicles at an acceptable cost. Hybrids can offer significant improvements in emissions and fuel economy. Series and parallel hybrids are compared. A combination of series and parallel operation would be the ideal. This can be obtained using a planetary gearbox as a power split device allowing a small generator to transfer power to the propulsion motor giving the effect of a CVT. It allows the engine to run at semi-constant speed giving better fuel economy and reduced emissions. Hybrid car developments are described that show the wide range of possible hybrid systems. (author)
Gauss decomposition for quantum groups and duality
Damaskinsky, E V; Lyakhovsky, V D; Sokolov, M A
1995-01-01
The Gauss decomposition of quantum groups and supergroups are considered. The main attention is paid to the R-matrix formulation of the Gauss decomposition and its properties as well as its relation to the contraction procedure. Duality aspects of the Gauss decomposition are also touched. For clarity of exposition a few simple examples are considered in some details.
Functionality Decomposition by Compositional Correctness Preserving Transformation
Brinksma, Hendrik; Langerak, Romanus
1995-01-01
We present an algorithm for the decomposition of processes in a process algebraic framework. Decomposition, or the refinement of process substructure, is an important design principle in the top-down development of concurrent systems. In the approach that we follow the decomposition is based on a
Nonlinear mode decomposition: A noise-robust, adaptive decomposition method
Iatsenko, Dmytro; McClintock, Peter V. E.; Stefanovska, Aneta
2015-09-01
The signals emanating from complex systems are usually composed of a mixture of different oscillations which, for a reliable analysis, should be separated from each other and from the inevitable background of noise. Here we introduce an adaptive decomposition tool—nonlinear mode decomposition (NMD)—which decomposes a given signal into a set of physically meaningful oscillations for any wave form, simultaneously removing the noise. NMD is based on the powerful combination of time-frequency analysis techniques—which, together with the adaptive choice of their parameters, make it extremely noise robust—and surrogate data tests used to identify interdependent oscillations and to distinguish deterministic from random activity. We illustrate the application of NMD to both simulated and real signals and demonstrate its qualitative and quantitative superiority over other approaches, such as (ensemble) empirical mode decomposition, Karhunen-Loève expansion, and independent component analysis. We point out that NMD is likely to be applicable and useful in many different areas of research, such as geophysics, finance, and the life sciences. The necessary matlab codes for running NMD are freely available for download.
Nonlinear mode decomposition: a noise-robust, adaptive decomposition method.
Iatsenko, Dmytro; McClintock, Peter V E; Stefanovska, Aneta
2015-09-01
The signals emanating from complex systems are usually composed of a mixture of different oscillations which, for a reliable analysis, should be separated from each other and from the inevitable background of noise. Here we introduce an adaptive decomposition tool-nonlinear mode decomposition (NMD)-which decomposes a given signal into a set of physically meaningful oscillations for any wave form, simultaneously removing the noise. NMD is based on the powerful combination of time-frequency analysis techniques-which, together with the adaptive choice of their parameters, make it extremely noise robust-and surrogate data tests used to identify interdependent oscillations and to distinguish deterministic from random activity. We illustrate the application of NMD to both simulated and real signals and demonstrate its qualitative and quantitative superiority over other approaches, such as (ensemble) empirical mode decomposition, Karhunen-Loève expansion, and independent component analysis. We point out that NMD is likely to be applicable and useful in many different areas of research, such as geophysics, finance, and the life sciences. The necessary matlab codes for running NMD are freely available for download.
Fractional Fourier Transform for Ultrasonic Chirplet Signal Decomposition
Directory of Open Access Journals (Sweden)
Yufeng Lu
2012-01-01
Full Text Available A fractional fourier transform (FrFT based chirplet signal decomposition (FrFT-CSD algorithm is proposed to analyze ultrasonic signals for NDE applications. Particularly, this method is utilized to isolate dominant chirplet echoes for successive steps in signal decomposition and parameter estimation. FrFT rotates the signal with an optimal transform order. The search of optimal transform order is conducted by determining the highest kurtosis value of the signal in the transformed domain. A simulation study reveals the relationship among the kurtosis, the transform order of FrFT, and the chirp rate parameter in the simulated ultrasonic echoes. Benchmark and ultrasonic experimental data are used to evaluate the FrFT-CSD algorithm. Signal processing results show that FrFT-CSD not only reconstructs signal successfully, but also characterizes echoes and estimates echo parameters accurately. This study has a broad range of applications of importance in signal detection, estimation, and pattern recognition.
Directory of Open Access Journals (Sweden)
Mohamed Elkawkagy
2013-11-01
Full Text Available Although planning techniques achieved a significant progress during recent years, solving many planning problem still difficult even for modern planners. In this paper, we will adopt landmark concept to hybrid planning setting - a method that combines reasoning about procedural knowledge and causalities. Land-marks are a well-known concept in the realm of classical planning. Recently, they have been adapted to hierarchical approaches. Such landmarks can be extracted in a pre-processing step from a declarative hierarchical planning domain and problem description. It was shown how this technique allows for a considerable reduction of the search space by eliminating futile plan development options before the actual planning. Therefore, we will present a new approach to in¬tegrate landmark pre-processing technique in the context of hierarchical planning with landmark technique in the classical planning. This integration allows to incorporate the ability of using extracted landmark tasks from hierarchical domain knowledge in the form of HTN and using landmark literals from classical planning. To this end, we will construct a transformation technique to transform the hybrid planning domain into a classical domain model. The method¬ologies in this paper have been implemented successfully, and we will present some experimental results that give evidence for the consid-erable performance increase gained through planning system.
Variance decomposition in stochastic simulators
Le Maître, O. P.
2015-06-28
This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.
Variance decomposition in stochastic simulators.
Le Maître, O P; Knio, O M; Moraes, A
2015-06-28
This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.
Variance decomposition in stochastic simulators
Le Maître, O. P.; Knio, O. M.; Moraes, A.
2015-06-01
This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.
Electrochemical decomposition of chlorinated hydrocarbons
McGee, Gerard Anthony
1993-01-01
This work involves the characterisation of the electrochemical decomposition of chlorinated hydrocarbons. A variety of methods were employed involving the use of catalytic reagents to enhance the rate at which chlorinated organic compounds are reduced. The first reagent used was oxygen which was electrochemically reduced to superoxide in nonaqueous solvents. Superoxide is a reactive intermediate and decomposes chlorinated hydrocarbons. However it was found that since the rate of reaction betw...
Physics-based hybrid method for multiscale transport in porous media
Yousefzadeh, Mehrdad; Battiato, Ilenia
2017-09-01
Despite advancements in the development of multiscale models for flow and reactive transport in porous media, the accurate, efficient and physics-based coupling of multiple scales in hybrid models remains a major theoretical and computational challenge. Improving the predictivity of macroscale predictions by means of multiscale algorithms relative to classical at-scale models is the primary motivation for the development of multiscale simulators. Yet, very few are the quantitative studies that explicitly address the predictive capability of multiscale coupling algorithms as it is still generally not possible to have a priori estimates of the errors that are present when complex flow processes are modeled. We develop a nonintrusive pore-/continuum-scale hybrid model whose coupling error is bounded by the upscaling error, i.e. we build a predictive tightly coupled multiscale scheme. This is accomplished by slightly enlarging the subdomain where continuum-scale equations are locally invalid and analytically defining physics-based coupling conditions at the interfaces separating the two computational sub-domains, while enforcing state variable and flux continuity. The proposed multiscale coupling approach retains the advantages of domain decomposition approaches, including the use of existing solvers for each subdomain, while it gains flexibility in the choice of the numerical discretization method and maintains the coupling errors bounded by the upscaling error. We implement the coupling in finite volumes and test the proposed method by modeling flow and transport through a reactive channel and past an array of heterogeneously reactive cylinders.
Thermal decomposition of natural dolomite
Indian Academy of Sciences (India)
S Gunasekaran; G Anbalagan
2007-08-01
Thermal decomposition behaviour of dolomite sample has been studied by thermogravimetric (TG) measurements. Differential thermal analysis (DTA) curve of dolomite shows two peaks at 777.8°C and 834°C. The two endothermic peaks observed in dolomite are essentially due to decarbonation of dolomite and calcite, respectively. The TG data of the decomposition steps have also been analysed using various differential, difference-differential and integral methods, viz. Freeman–Carroll, Horowitz–Metzger, Coats–Redfern methods. Values of activation entropy, Arrhenius factor, and order of reaction have been approximated and compared. Measured activation energies vary between 97 and 147 kJ mol-1. The large fluctuation in activation energy is attributed to the presence of impurities such as SiO2, Al2O3, Fe2O3, Cl- etc in the samples. FTIR and XRD analyses confirm the decomposition reaction. SEM observation of the heat-treated samples at 950°C shows cluster of grains, indicating the structural transformation.
A Lagrangian Dynamic Mode Decomposition
Sesterhenn, Jörn
2016-01-01
Temporal or spatial structures are readily extracted from complex data by modal decompositions like POD or DMD. Subspaces of that decompositions serve as reduced order models and define spatial structures in time or temporal structures in space. Convecting phenomena pose a major problem to those decompositions. A structure travelling with a certain group velocity will be perceived as a plethora of modes in time or space respectively. This manifests itself for example in poorly decaying Singular Values when using a POD. The poor decay is very counter-intuitive, since we expect a single structure to be represented by a few modes. The intuition proves to be correct and we show that in a properly chosen reference frame along the characteristic defined by the group velocity, a POD or DMD reduces moving structures to a few modes, as expected. Beyond serving as a reduced model, the re- sulting entity can be used to define a constant or minimally changing structure in turbulent flows. This can be interpreted as an em...
The thermal decomposition of nitrocellulose
Energy Technology Data Exchange (ETDEWEB)
Jones, D. E. G.; Turcotte, R.; Acheson, B.; Kwok, Q. S. M.; Vachon, M. [Natural Resources Canada, CANMET Canadian Explosives Research Laboratory, Ottawa, ON (Canada)
2003-03-01
In the past, the thermal decomposition of nitrocellulose, the main high-energy component of explosives and solid rocket propellant compositions, was studied using DSC, thermogravimetry and accelerating rate calorimetry. This paper discusses new results obtained by accelerating rate calorimetry (ARC), heat flux calorimetry (HFC), simultaneous thermogravimetry (TG) and differential thermal analysis (DTA) coupled to FTIR and mass spectrometry (MS). Experiments with ARC showed that both the onset temperature and the activation energy for the thermal decomposition depend on sample mass. Evaluating the thermal decomposition of nitrocellulose using HFC at various pressures of argon between ambient and 27 MPa showed that the true onset temperature and the width of the corresponding exotherms are a strong function of the initial pressure. Also presented are the results of investigations conducted using TG-DTA-FTIR-MS in air and in helium. Corresponding to the sharp exotherm observed in helium, many gaseous product species were detected in a narrow band in FTIR and MS spectra. The main species observed by FTIR were carbon dioxide, formic acid, carbon monoxide and trace amounts of formaldehyde, nitrous oxide and water. In comparison, the products detected in air were found to occur in a much wider temperature range. Absorbances of carbon dioxide, nitrogen dioxide and water were observed to have been strongly enhanced in air, while organic species such as formic acid and formaldehyde were significantly depressed. 13 refs., 1 tab., 8 figs.
Li, Lei; Wang, Linyuan; Yan, Bin; Zhang, Hanming; Zheng, Zhizhong; Zhang, Wenkun; Lu, Wanli; Hu, Guoen
2016-01-01
Dual-energy computed tomography (DECT) has shown great potential and promising applications in advanced imaging fields for its capabilities of material decomposition. However, image reconstructions and decompositions under sparse views dataset suffers severely from multi factors, such as insufficiencies of data, appearances of noise, and inconsistencies of observations. Under sparse views, conventional filtered back-projection type reconstruction methods fails to provide CT images with satisfying quality. Moreover, direct image decomposition is unstable and meet with noise boost even with full views dataset. This paper proposes an iterative image reconstruction algorithm and a practical image domain decomposition method for DECT. On one hand, the reconstruction algorithm is formulated as an optimization problem, which containing total variation regularization term and data fidelity term. The alternating direction method is utilized to design the corresponding algorithm which shows faster convergence speed com...
DEFF Research Database (Denmark)
Hjorth, Theis Solberg; Torbensen, Rune
2012-01-01
that enables secure end-to-end communication with home automation devices, and it supports device revocations as well as a structure of intersecting sets of nodes for scalability. Devices in the Trusted Domain are registered in a list that is distributed using a robust epidemic protocol optimized...
DEFF Research Database (Denmark)
Schraefel, M. C.; Rouncefield, Mark; Kellogg, Wendy
2012-01-01
In CSCW, how much do we need to know about another domain/culture before we observe, intersect and intervene with designs. What optimally would that other culture need to know about us? Is this a “how long is a piece of string” question, or an inquiry where we can consider a variety of contexts a...
Spatial fractal characteristic of spinodal decomposition in Fe-Cr-Ni duplex stainless steel
Energy Technology Data Exchange (ETDEWEB)
Shek, C.H.; Wong, K.W.; Lai, J.K.L. [City Univ. of Hong Kong (Hong Kong). Dept. of Physics and Materials Science; Shao, Y.Z. [Zhongshan Univ., Guangzhou (China). Dept. of Physics
1997-08-15
Owing to the extensive use of duplex stainless steels in areas like chemical and petrochemical industries, considerable interest has arisen concerning the thermal degradation of these materials during service, and the consequent changes on the mechanical properties. The embrittlement of these steels is basically due to the decomposition of the ferrite phase at elevated temperatures, and duplex steels are seldom used at temperatures above 300 C. Although the microstructure of spinodal decomposition has been studied extensively using atom probe, it is interesting to investigate the development of fractal characteristics in the microstructure during spinodal decomposition. In this paper the authors present part of their recent results in this aspect on a duplex stainless steel. The {alpha} and {alpha}{prime} domains evolved from the primary ferrite phase during spinodal decomposition have different morphologies. The {alpha} (Fe-rich) forms the matrix while the {alpha}{prime} (Cr-rich) domains are developed in the form of discrete regions embedded within the {alpha} matrix. The distribution of these domains follows the fractal-growth characteristics with fractal dimensions ranging from 0.1 to 0.2. In addition, there exists a lower critical dimension beyond which the self-similarity of the domains breaks down.
Adaptive Fourier Decomposition Based Time-Frequency Analysis
Institute of Scientific and Technical Information of China (English)
Li-Ming Zhang
2014-01-01
The attempt to represent a signal simultaneously in time and frequency domains is full of challenges. The recently proposed adaptive Fourier decomposition (AFD) offers a practical approach to solve this problem. This paper presents the principles of the AFD based time-frequency analysis in three aspects: instantaneous frequency analysis, frequency spectrum analysis, and the spectrogram analysis. An experiment is conducted and compared with the Fourier transform in convergence rate and short-time Fourier transform in time-frequency distribution. The proposed approach performs better than both the Fourier transform and short-time Fourier transform.
Spinodal Decomposition in Mixtures Containing Surfactants
Melenekvitz, J.
1998-03-01
Spinodal decomposition in mixtures containing two immiscible liquids (A and B) plus surfactant was investigated using a recently developed (J. Melenkevitz and S. H. Javadpour, J. Chem. Phys., 107, 623 (1997).) 3-component Ginzburg-Landau model. The time dependent Ginzburg-Landau (TDGL) equations governing the evolution of structure were numerically integrated in 2-dimensions. We found the growth rate of the average domain size, R(t), decreased with increasing surfactant concentration over a wide range of relative amounts of A and B. This can be attributed to the surfactant accumulating at the growing interface between the immiscible liquids, which leads to a reduction in the surface tension. At late times, the growth rate was noticeably altered when thermal fluctuations were added to the numerical simulations. In this case, power law behavior was observed for R(t) at late times, R(t) ~ t^α, with the exponent α decreasing as the amount of surfactant increased. The dynamics at early times were determined by linearizing the TDGL equations about a uniformly mixed state. The growth rate at ealry times was found to be strongly dependent on the model parameters describing the surfactant miscibility in A and B and the surfactant strength. Comparison with recent measurements on SBR / PB mixtures with added PB-SBR diblock copolymer will also be presented.
Modelling volatility by variance decomposition
DEFF Research Database (Denmark)
Amado, Cristina; Teräsvirta, Timo
on the multiplicative decomposition of the variance is developed. It is heavily dependent on Lagrange multiplier type misspecification tests. Finite-sample properties of the strategy and tests are examined by simulation. An empirical application to daily stock returns and another one to daily exchange rate returns...... illustrate the functioning and properties of our modelling strategy in practice. The results show that the long memory type behaviour of the sample autocorrelation functions of the absolute returns can also be explained by deterministic changes in the unconditional variance....
Azimuthal decomposition of optical modes
CSIR Research Space (South Africa)
Dudley, Angela L
2012-07-01
Full Text Available of Optical Modes Angela Dudley1, Igor Litvin1, Filippus S. Roux1 and Andrew Forbes1,2,3 1 CSIR National Laser Centre, Pretoria, South Africa 2 School of Physics, University of KwaZulu-Natal, Durban, South Africa 3 Laser Research Institute, University... of Stellenbosch, Stellenbosch, South Africa Presented at the 2012 South African Institute of Physics Conference University of Pretoria Pretoria, South Africa 12 July 2012 To decompose the azimuthal modes we need two steps: generation and decomposition...
Non-isothermal decomposition kinetics of magnesite
Maitra, S; Mukherjee, S.; Saha, N; Pramanik, J
2007-01-01
Kinetics of thermal decomposition of Indian magnesite was studied by thermo-gravimetric analysis under non-isothermal condition. Coats and Redfern Integral approximation method was used to determine the kinetic parameters. Using the kinetic parameters different kinetic functions were analyzed with the experimental data to ascertain the decomposition mechanism of magnesium carbonate and it was observed that the decomposition reaction followed a contracting sphere kinetic mechanism.
An operational modal analysis method in frequency and spatial domain
Wang, Tong; Zhang, Lingmi; Tamura, Yukio
2005-12-01
A frequency and spatial domain decomposition method (FSDD) for operational modal analysis (OMA) is presented in this paper, which is an extension of the complex mode indicator function (CMIF) method for experimental modal analysis (EMA). The theoretical background of the FSDD method is clarified. Singular value decomposition is adopted to separate the signal space from the noise space. Finally, an enhanced power spectrum density (PSD) is proposed to obtain more accurate modal parameters by curve fitting in the frequency domain. Moreover, a simulation case and an application case are used to validate this method.
An operational modal analysis method in frequency and spatial domain
Institute of Scientific and Technical Information of China (English)
Wang Tong; Zhang Lingmi; Tamura Yukio
2005-01-01
A frequency and spatial domain decomposition method (FSDD) for operational modal analysis (OMA) is presented in this paper, which is an extension of the complex mode indicator function (CMIF) method for experimental modal analysis (EMA). The theoretical background of the FSDD method is clarified. Singular value decomposition is adopted to separate the signal space from the noise space. Finally, an enhanced power spectrum density (PSD) is proposed to obtain more accurate modal parameters by curve fitting in the frequency domain. Moreover, a simulation case and an application case are used to validate this method.
A multiconfigurational hybrid density-functional theory
Sharkas, Kamal; Jensen, Hans Jørgen Aa; Toulouse, Julien; 10.1063/1.4733672
2012-01-01
We propose a multiconfigurational hybrid density-functional theory which rigorously combines a multiconfiguration self-consistent-field calculation with a density-functional approximation based on a linear decomposition of the electron-electron interaction. This gives a straightforward extension of the usual hybrid approximations by essentially adding a fraction \\lambda of exact static correlation in addition to the fraction \\lambda of exact exchange. Test calculations on the cycloaddition reactions of ozone with ethylene or acetylene and the dissociation of diatomic molecules with the Perdew-Burke-Ernzerhof (PBE) and Becke-Lee-Yang-Parr (BLYP) density functionals show that a good value of \\lambda is 0.25, as in the usual hybrid approximations. The results suggest that the proposed multiconfigurational hybrid approximations can improve over usual density-functional calculations for situations with strong static correlation effects.
Highly Scalable Matching Pursuit Signal Decomposition Algorithm
National Aeronautics and Space Administration — In this research, we propose a variant of the classical Matching Pursuit Decomposition (MPD) algorithm with significantly improved scalability and computational...
On Schubert decompositions of quiver Grassmannians
Lorscheid, Oliver
2014-02-01
In this paper, we introduce Schubert decompositions for quiver Grassmannians and investigate certain classes of quiver Grassmannians with a Schubert decomposition into affine spaces. The main theorem puts the cells of a Schubert decomposition into relation to the cells of a certain simpler quiver Grassmannian. This allows us to extend known examples of Schubert decompositions into affine spaces to a larger class of quiver Grassmannians. This includes exceptional representations of the Kronecker quiver as well as representations of forests with block matrices of the form (0100). Finally, we draw conclusions on the Euler characteristics and the cohomology of quiver Grassmannians.
Direct observation of nanowire growth and decomposition
DEFF Research Database (Denmark)
Rackauskas, Simas; Shandakov, Sergey D; Jiang, Hua
2017-01-01
knowledge, so far this has been only postulated, but never observed at the atomic level. By means of in situ environmental transmission electron microscopy we monitored and examined the atomic layer transformation at the conditions of the crystal growth and its decomposition using CuO nanowires selected...... as a model object. The atomic layer growth/decomposition was studied by varying an O2 partial pressure. Three distinct regimes of the atomic layer evolution were experimentally observed: growth, transition and decomposition. The transition regime, at which atomic layer growth/decomposition switch takes place...
Decomposition methods in turbulence research
Directory of Open Access Journals (Sweden)
Uruba Václav
2012-04-01
Full Text Available Nowadays we have the dynamical velocity vector field of turbulent flow at our disposal coming thanks advances of either mathematical simulation (DNS or of experiment (time-resolved PIV. Unfortunately there is no standard method for analysis of such data describing complicated extended dynamical systems, which is characterized by excessive number of degrees of freedom. An overview of candidate methods convenient to spatiotemporal analysis for such systems is to be presented. Special attention will be paid to energetic methods including Proper Orthogonal Decomposition (POD in regular and snapshot variants as well as the Bi-Orthogonal Decomposition (BOD for joint space-time analysis. Then, stability analysis using Principal Oscillation Patterns (POPs will be introduced. Finally, the Independent Component Analysis (ICA method will be proposed for detection of coherent structures in turbulent flow-field defined by time-dependent velocity vector field. Principle and some practical aspects of the methods are to be shown. Special attention is to be paid to physical interpretation of outputs of the methods listed above.
Thermal decomposition of mercuric sulfide
Energy Technology Data Exchange (ETDEWEB)
Leckey, J.H.; Nulf, L.E.
1994-10-28
The rate of thermal decomposition of mercuric sulfide (HgS) has been measured at temperatures from 265 to 345 C. These data have been analyzed using a first-order chemical reaction model for the time dependence of the reaction and the Arrhenius equation for the temperature dependence of the rate constant. Using this information, the activation energy for the reaction was found to be 55 kcal/mol. Significant reaction vessel surface effects obscured the functional form of the time dependence of the initial portion of the reaction. The data and the resulting time-temperature reaction-rate model were used to predict the decomposition rate of HgS as a function of time and temperature in thermal treatment systems. Data from large-scale thermal treatment studies already completed were interpreted in terms of the results of this study. While the data from the large-scale thermal treatment studies were consistent with the data from this report, mass transport effects may have contributed to the residual amount of mercury which remained in the soil after most of the large-scale runs.
Decomposition of Diethylstilboestrol in Soil
DEFF Research Database (Denmark)
Gregers-Hansen, Birte
1964-01-01
The rate of decomposition of DES-monoethyl-1-C14 in soil was followed by measurement of C14O2 released. From 1.6 to 16% of the added C14 was recovered as C14O2 during 3 months. After six months as much as 12 to 28 per cent was released as C14O2.Determination of C14 in the soil samples after the e...... not inhibit the CO2 production from the soil.Experiments with γ-sterilized soil indicated that enzymes present in the soil are able to attack DES.......The rate of decomposition of DES-monoethyl-1-C14 in soil was followed by measurement of C14O2 released. From 1.6 to 16% of the added C14 was recovered as C14O2 during 3 months. After six months as much as 12 to 28 per cent was released as C14O2.Determination of C14 in the soil samples after...
Efficient Delaunay Tessellation through K-D Tree Decomposition
Energy Technology Data Exchange (ETDEWEB)
Morozov, Dmitriy; Peterka, Tom
2017-08-21
Delaunay tessellations are fundamental data structures in computational geometry. They are important in data analysis, where they can represent the geometry of a point set or approximate its density. The algorithms for computing these tessellations at scale perform poorly when the input data is unbalanced. We investigate the use of k-d trees to evenly distribute points among processes and compare two strategies for picking split points between domain regions. Because resulting point distributions no longer satisfy the assumptions of existing parallel Delaunay algorithms, we develop a new parallel algorithm that adapts to its input and prove its correctness. We evaluate the new algorithm using two late-stage cosmology datasets. The new running times are up to 50 times faster using k-d tree compared with regular grid decomposition. Moreover, in the unbalanced data sets, decomposing the domain into a k-d tree is up to five times faster than decomposing it into a regular grid.
Advances in audio watermarking based on singular value decomposition
Dhar, Pranab Kumar
2015-01-01
This book introduces audio watermarking methods for copyright protection, which has drawn extensive attention for securing digital data from unauthorized copying. The book is divided into two parts. First, an audio watermarking method in discrete wavelet transform (DWT) and discrete cosine transform (DCT) domains using singular value decomposition (SVD) and quantization is introduced. This method is robust against various attacks and provides good imperceptible watermarked sounds. Then, an audio watermarking method in fast Fourier transform (FFT) domain using SVD and Cartesian-polar transformation (CPT) is presented. This method has high imperceptibility and high data payload and it provides good robustness against various attacks. These techniques allow media owners to protect copyright and to show authenticity and ownership of their material in a variety of applications. · Features new methods of audio watermarking for copyright protection and ownership protection · Outl...
Wong, Un-Hong; Aoki, Takayuki; Wong, Hon-Cheng
2014-07-01
Modern graphics processing units (GPUs) have been widely utilized in magnetohydrodynamic (MHD) simulations in recent years. Due to the limited memory of a single GPU, distributed multi-GPU systems are needed to be explored for large-scale MHD simulations. However, the data transfer between GPUs bottlenecks the efficiency of the simulations on such systems. In this paper we propose a novel GPU Direct-MPI hybrid approach to address this problem for overall performance enhancement. Our approach consists of two strategies: (1) We exploit GPU Direct 2.0 to speedup the data transfers between multiple GPUs in a single node and reduce the total number of message passing interface (MPI) communications; (2) We design Compute Unified Device Architecture (CUDA) kernels instead of using memory copy to speedup the fragmented data exchange in the three-dimensional (3D) decomposition. 3D decomposition is usually not preferable for distributed multi-GPU systems due to its low efficiency of the fragmented data exchange. Our approach has made a breakthrough to make 3D decomposition available on distributed multi-GPU systems. As a result, it can reduce the memory usage and computation time of each partition of the computational domain. Experiment results show twice the FLOPS comparing to common 2D decomposition MPI-only implementation method. The proposed approach has been developed in an efficient implementation for MHD simulations on distributed multi-GPU systems, called MGPU-MHD code. The code realizes the GPU parallelization of a total variation diminishing (TVD) algorithm for solving the multidimensional ideal MHD equations, extending our work from single GPU computation (Wong et al., 2011) to multiple GPUs. Numerical tests and performance measurements are conducted on the TSUBAME 2.0 supercomputer at the Tokyo Institute of Technology. Our code achieves 2 TFLOPS in double precision for the problem with 12003 grid points using 216 GPUs.
Cetorelli, Nicola
2014-01-01
I introduce the concept of hybrid intermediaries: financial conglomerates that control a multiplicity of entity types active in the "assembly line" process of modern financial intermediation, a system that has become known as shadow banking. The complex bank holding companies of today are the best example of hybrid intermediaries, but I argue that financial firms from the "nonbank" space can just as easily evolve into conglomerates with similar organizational structure, thus acquiring the cap...
CSIR Research Space (South Africa)
Jacob John, Maya
2009-04-01
Full Text Available effect was observed for the elongation at break of the hybrid composites. The impact strength of the hybrid composites increased with the addition of glass fibres. The tensile and impact properties of thermoplastic natural rubber reinforced short... panels made from conventional structural materials. Figure 3 illustrates the performance of cellular biocomposite panels against conventional systems used for building and residential construction, namely a pre- cast pre-stressed hollow core concrete...
Structure-preserving sparse decomposition for facial expression analysis.
Taheri, Sima; Qiang Qiu; Chellappa, Rama
2014-08-01
Although facial expressions can be decomposed in terms of action units (AUs) as suggested by the facial action coding system, there have been only a few attempts that recognize expression using AUs and their composition rules. In this paper, we propose a dictionary-based approach for facial expression analysis by decomposing expressions in terms of AUs. First, we construct an AU-dictionary using domain experts' knowledge of AUs. To incorporate the high-level knowledge regarding expression decomposition and AUs, we then perform structure-preserving sparse coding by imposing two layers of grouping over AU-dictionary atoms as well as over the test image matrix columns. We use the computed sparse code matrix for each expressive face to perform expression decomposition and recognition. Since domain experts' knowledge may not always be available for constructing an AU-dictionary, we also propose a structure-preserving dictionary learning algorithm, which we use to learn a structured dictionary as well as divide expressive faces into several semantic regions. Experimental results on publicly available expression data sets demonstrate the effectiveness of the proposed approach for facial expression analysis.
Uncertainty propagation in orbital mechanics via tensor decomposition
Sun, Yifei; Kumar, Mrinal
2016-03-01
Uncertainty forecasting in orbital mechanics is an essential but difficult task, primarily because the underlying Fokker-Planck equation (FPE) is defined on a relatively high dimensional (6-D) state-space and is driven by the nonlinear perturbed Keplerian dynamics. In addition, an enormously large solution domain is required for numerical solution of this FPE (e.g. encompassing the entire orbit in the x-y-z subspace), of which the state probability density function (pdf) occupies a tiny fraction at any given time. This coupling of large size, high dimensionality and nonlinearity makes for a formidable computational task, and has caused the FPE for orbital uncertainty propagation to remain an unsolved problem. To the best of the authors' knowledge, this paper presents the first successful direct solution of the FPE for perturbed Keplerian mechanics. To tackle the dimensionality issue, the time-varying state pdf is approximated in the CANDECOMP/PARAFAC decomposition tensor form where all the six spatial dimensions as well as the time dimension are separated from one other. The pdf approximation for all times is obtained simultaneously via the alternating least squares algorithm. Chebyshev spectral differentiation is employed for discretization on account of its spectral ("super-fast") convergence rate. To facilitate the tensor decomposition and control the solution domain size, system dynamics is expressed using spherical coordinates in a noninertial reference frame. Numerical results obtained on a regular personal computer are compared with Monte Carlo simulations.
Non-equilibrium theory of arrested spinodal decomposition
Energy Technology Data Exchange (ETDEWEB)
Olais-Govea, José Manuel; López-Flores, Leticia; Medina-Noyola, Magdaleno [Instituto de Física “Manuel Sandoval Vallarta,” Universidad Autónoma de San Luis Potosí, Álvaro Obregón 64, 78000 San Luis Potosí, SLP (Mexico)
2015-11-07
The non-equilibrium self-consistent generalized Langevin equation theory of irreversible relaxation [P. E. Ramŕez-González and M. Medina-Noyola, Phys. Rev. E 82, 061503 (2010); 82, 061504 (2010)] is applied to the description of the non-equilibrium processes involved in the spinodal decomposition of suddenly and deeply quenched simple liquids. For model liquids with hard-sphere plus attractive (Yukawa or square well) pair potential, the theory predicts that the spinodal curve, besides being the threshold of the thermodynamic stability of homogeneous states, is also the borderline between the regions of ergodic and non-ergodic homogeneous states. It also predicts that the high-density liquid-glass transition line, whose high-temperature limit corresponds to the well-known hard-sphere glass transition, at lower temperature intersects the spinodal curve and continues inside the spinodal region as a glass-glass transition line. Within the region bounded from below by this low-temperature glass-glass transition and from above by the spinodal dynamic arrest line, we can recognize two distinct domains with qualitatively different temperature dependence of various physical properties. We interpret these two domains as corresponding to full gas-liquid phase separation conditions and to the formation of physical gels by arrested spinodal decomposition. The resulting theoretical scenario is consistent with the corresponding experimental observations in a specific colloidal model system.
Evidence of convective heat transfer enhancement induced by spinodal decomposition.
Poesio, P; Lezzi, A M; Beretta, G P
2007-06-01
Spinodal decomposition can be driven by either diffusion or self-induced convection; the importance of convection relative to diffusion depends on the Péclet number, defined as the ratio between convective and diffusive mass fluxes. Diffusion is the dominating mechanism of phase segregation when the Péclet number is small - i.e., when viscosity and diffusivity are large - or when the domain characteristic size is small. For low-viscosity mixtures, convection is the dominating process and the segregation is very rapid as it takes a few seconds compared to the hours needed in the case of pure diffusion. In such cases, strong convective motion of the phase segregating domains is generated even in small-size systems and is almost independent of the temperature difference as long as it is below the transition value. We study experimentally the enhancement of heat transfer in a 1-mm -thick cell. A water-acetonitrile-toulene mixture is quenched into a two-phase region so as to induce convection-driven spinodal decomposition. The heat transfer rate is measured and compared to that obtained in the absence of convective motion. A substantial reduction in the cooling time obtains in the case of spinodal decomposition. The heat transfer enhancement induced by this self-induced, disordered but effectively convective effect may be exploited in the cooling or heating of small-scale systems whereby forced convection cannot be achieved because of the small sizes involved. A scaling analysis of the data based on the diffuse interface H model for a symmetric mixture near the equilibrium point yields very encouraging agreement and insights.
Jodin, Gurvan; Scheller, Johannes; Rouchon, Jean-François; Braza, Marianna; Mit Collaboration; Imft Collaboration; Laplace Collaboration
2016-11-01
A quantitative characterization of the effects obtained by high frequency-low amplitude trailing edge actuation is performed. Particle image velocimetry, as well as pressure and aerodynamic force measurements, are carried out on an airfoil model. This hybrid morphing wing model is equipped with both trailing edge piezoelectric-actuators and camber control shape memory alloy actuators. It will be shown that this actuation allows for an effective manipulation of the wake turbulent structures. Frequency domain analysis and proper orthogonal decomposition show that proper actuating reduces the energy dissipation by favoring more coherent vortical structures. This modification in the airflow dynamics eventually allows for a tapering of the wake thickness compared to the baseline configuration. Hence, drag reductions relative to the non-actuated trailing edge configuration are observed. Massachusetts Institute of Technology.
Parallel Computing Characteristics of CUPID code under MPI and Hybrid environment
Energy Technology Data Exchange (ETDEWEB)
Lee, Jae Ryong; Yoon, Han Young [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Jeon, Byoung Jin; Choi, Hyoung Gwon [Seoul National Univ. of Science and Technology, Seoul (Korea, Republic of)
2014-05-15
In this paper, a characteristic of parallel algorithm is presented for solving an elliptic type equation of CUPID via domain decomposition method using the MPI and the parallel performance is estimated in terms of a scalability which shows the speedup ratio. In addition, the time-consuming pattern of major subroutines is studied. Two different grid systems are taken into account: 40,000 meshes for coarse system and 320,000 meshes for fine system. Since the matrix of the CUPID code differs according to whether the flow is single-phase or two-phase, the effect of matrix shape is evaluated. Finally, the effect of the preconditioner for matrix solver is also investigated. Finally, the hybrid (OpenMP+MPI) parallel algorithm is introduced and discussed in detail for solving pressure solver. Component-scale thermal-hydraulics code, CUPID has been developed for two-phase flow analysis, which adopts a three-dimensional, transient, three-field model, and parallelized to fulfill a recent demand for long-transient and highly resolved multi-phase flow behavior. In this study, the parallel performance of the CUPID code was investigated in terms of scalability. The CUPID code was parallelized with domain decomposition method. The MPI library was adopted to communicate the information at the neighboring domain. For managing the sparse matrix effectively, the CSR storage format is used. To take into account the characteristics of the pressure matrix which turns to be asymmetric for two-phase flow, both single-phase and two-phase calculations were run. In addition, the effect of the matrix size and preconditioning was also investigated. The fine mesh calculation shows better scalability than the coarse mesh because the number of coarse mesh does not need to decompose the computational domain excessively. The fine mesh can be present good scalability when dividing geometry with considering the ratio between computation and communication time. For a given mesh, single-phase flow
Wavelet De-noising of Speech Using Singular Spectrum Analysis for Decomposition Level Selection
Institute of Scientific and Technical Information of China (English)
CAI Tie; ZHU Jie
2007-01-01
The problem of speech enhancement using threshold de-noising in wavelet domain was considered. The appropriate decomposition level is another key factor pertinent to de-noising performance. This paper proposed a new wavelet-based de-noising scheme that can improve the enhancement performance significantly in the presence of additive white Gaussian noise. The proposed algorithm can adaptively select the optimal decomposition level of wavelet transformation according to the characteristics of noisy speech. The experimental results demonstrate that this proposed algorithm outperforms the classical wavelet-based de-noising method and effectively improves the practicability of this kind of techniques.
Tree decompositions and social graphs
Adcock, Aaron B; Mahoney, Michael W
2014-01-01
Recent work has established that large informatics graphs such as social and information networks have non-trivial tree-like structure when viewed at moderate size scales. Here, we present results from the first detailed empirical evaluation of the use of tree decomposition (TD) heuristics for structure identification and extraction in social graphs. Although TDs have historically been used in structural graph theory and scientific computing, we show that---even with existing TD heuristics developed for those very different areas---TD methods can identify interesting structure in a wide range of realistic informatics graphs. Among other things, we show that TD methods can identify structures that correlate strongly with the core-periphery structure of realistic networks, even when using simple greedy heuristics; we show that the peripheral bags of these TDs correlate well with low-conductance communities (when they exist) found using local spectral computations; and we show that several types of large-scale "...
Nonnegative Decomposition of Multivariate Information
Williams, Paul L
2010-01-01
Of the various attempts to generalize information theory to multiple variables, the most widely utilized, interaction information, suffers from the problem that it is sometimes negative. Here we reconsider from first principles the general structure of the information that a set of sources provides about a given variable. We begin with a new definition of redundancy as the minimum information that any source provides about each possible outcome of the variable, averaged over all possible outcomes. We then show how this measure of redundancy induces a lattice over sets of sources that clarifies the general structure of multivariate information. Finally, we use this redundancy lattice to propose a definition of partial information atoms that exhaustively decompose the Shannon information in a multivariate system in terms of the redundancy between synergies of subsets of the sources. Unlike interaction information, the atoms of our partial information decomposition are never negative and always support a clear i...
Regular Decompositions for H(div) Spaces
Energy Technology Data Exchange (ETDEWEB)
Kolev, Tzanio [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Applied Scientific Computing; Vassilevski, Panayot [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Applied Scientific Computing
2012-01-01
We study regular decompositions for H(div) spaces. In particular, we show that such regular decompositions are closely related to a previously studied “inf-sup” condition for parameter-dependent Stokes problems, for which we provide an alternative, more direct, proof.
Complete azimuthal decomposition of optical fields
CSIR Research Space (South Africa)
Dudley, Angela L
2013-02-01
Full Text Available By using digital holograms, we present a simple technique for performing a complete azimuthal decomposition of an arbitrary laser mode. The match-filter, used to perform the azimuthal decomposition, is bounded by an annular ring, allowing us...
Some Aspects of Thermochemical Decomposition of Peat
Directory of Open Access Journals (Sweden)
Y. A. Losiuk
2008-01-01
Full Text Available The paper considers peculiar features of thermochemical decomposition of peat as a result of quick pyrolysis. Evaluation of energy and economic expediency of the preliminary peat decomposition process for obtaining liquid and gaseous products has been made in the paper. The paper reveals prospects pertaining to application of the given technology while generating electric power and heat.
Some Aspects of Thermochemical Decomposition of Peat
Y. A. Losiuk; S. V. Gibric; S. V. Korchinenko
2008-01-01
The paper considers peculiar features of thermochemical decomposition of peat as a result of quick pyrolysis. Evaluation of energy and economic expediency of the preliminary peat decomposition process for obtaining liquid and gaseous products has been made in the paper. The paper reveals prospects pertaining to application of the given technology while generating electric power and heat.
Climate history shapes contemporary leaf litter decomposition
Michael S. Strickland; Ashley D. Keiser; Mark A. Bradford
2015-01-01
Litter decomposition is mediated by multiple variables, of which climate is expected to be a dominant factor at global scales. However, like other organisms, traits of decomposers and their communities are shaped not just by the contemporary climate but also their climate history. Whether or not this affects decomposition rates is underexplored. Here we source...
Decompositions of Revised Monotone Signed Fuzzy Measures
Institute of Scientific and Technical Information of China (English)
张强; 刘克
2003-01-01
The concept of fuzzy measure was introduced by Sugeno in 1974. A notion of signed fuzzy measure is introduced in this paper, and its elementary properties are briefly discussed. An analogue of Hahn decomposition theorem is established under the null-null-additive condition. A version of the Jordan decomposition theorem is proved under the null-additive condition.
Helmholtz Hodge decomposition of scalar optical fields.
Bahl, Monika; Senthilkumaran, P
2012-11-01
It is shown that the vector field decomposition method, namely, the Helmholtz Hodge decomposition, can also be applied to analyze scalar optical fields that are ubiquitously present in interference and diffraction optics. A phase gradient field that depicts the propagation and Poynting vector directions can hence be separated into solenoidal and irrotational components.
A global HMX decomposition model
Energy Technology Data Exchange (ETDEWEB)
Hobbs, M.L.
1996-12-01
HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) decomposes by competing reaction pathways to form various condensed and gas-phase intermediate and final products. Gas formation is related to the development of nonuniform porosity and high specific surface areas prior to ignition in cookoff events. Such thermal damage enhances shock sensitivity and favors self-supported accelerated burning. The extent of HMX decomposition in highly confined cookoff experiments remains a major unsolved experimental and modeling problem. The present work is directed at determination of global HMX kinetics useful for predicting the elapsed time to thermal runaway (ignition) and the extent of decomposition at ignition. Kinetic rate constants for a six step engineering based global mechanism were obtained using gas formation rates measured by Behrens at Sandia National Laboratories with his Simultaneous Modulated Beam Mass Spectrometer (STMBMS) experimental apparatus. The six step global mechanism includes competition between light gas (H[sub 2]Awe, HCN, CO, H[sub 2]CO, NO, N[sub 2]Awe) and heavy gas (C[sub 2]H[sub 6]N[sub 2]Awe and C[sub 4]H[sub 10]N0[sub 2]) formation with zero order sublimation of HMX and the mononitroso analog of HMX (mn-HMX), C[sub 4]H[sub 8]N[sub 8]Awe[sub 7]. The global mechanism was applied to the highly confined, One Dimensional Time to eXplosion (ODTX) experiment and hot cell experiments by suppressing the sublimation of HMX and mn-HMX. An additional gas-phase reaction was also included to account for the gas-phase reaction of N[sub 2]Awe with H[sub 2]CO. Predictions compare adequately to the STMBMS data, ODTX data, and hot cell data. Deficiencies in the model and future directions are discussed.
Directed Graphs, Decompositions, and Spatial Linkages
Shai, Offer; Whiteley, Walter
2010-01-01
The decomposition of a system of constraints into small basic components is an important tool of design and analysis. Specifically, the decomposition of a linkage into minimal components is a central tool of analysis and synthesis of linkages. In this paper we prove that every pinned 3-isostatic (minimally rigid) graph (grounded linkage) has a unique decomposition into minimal strongly connected components (in the sense of directed graphs) which we call 3-Assur graphs. This analysis extends the Assur decompositions of plane linkages previously studied in the mathematical and the mechanical engineering literature. These 3-Assur graphs are the central building blocks for all kinematic linkages in 3-space. They share a number of key combinatorial and geometric properties with the 2-Assur graphs, including an associated lower block-triangular decomposition of the pinned rigidity matrix which provides a format for extending the motion induced by inserting one driver in a bottom Assur linkage to the joints of the e...
Multilinear operators for higher-order decompositions.
Energy Technology Data Exchange (ETDEWEB)
Kolda, Tamara Gibson
2006-04-01
We propose two new multilinear operators for expressing the matrix compositions that are needed in the Tucker and PARAFAC (CANDECOMP) decompositions. The first operator, which we call the Tucker operator, is shorthand for performing an n-mode matrix multiplication for every mode of a given tensor and can be employed to concisely express the Tucker decomposition. The second operator, which we call the Kruskal operator, is shorthand for the sum of the outer-products of the columns of N matrices and allows a divorce from a matricized representation and a very concise expression of the PARAFAC decomposition. We explore the properties of the Tucker and Kruskal operators independently of the related decompositions. Additionally, we provide a review of the matrix and tensor operations that are frequently used in the context of tensor decompositions.
Hybrid lipids increase nanoscale fluctuation lifetimes in mixed membranes
Palmieri, Benoit; Safran, Samuel A.
2013-09-01
A recently proposed ternary mixture model is used to predict fluctuation domain lifetimes in the one phase region. The membrane is made of saturated, unsaturated, and hybrid lipids that have one saturated and one unsaturated hydrocarbon chain. The hybrid lipid is a natural linactant which can reduce the packing incompatibility between saturated and unsaturated lipids. The fluctuation lifetimes are predicted as a function of the hybrid lipid fraction and the fluctuation domain size. These lifetimes can be increased by up to three orders of magnitude compared to the case of no hybrids. With hybrid, small length scale fluctuations have sizable amplitudes even close to the critical temperature and, hence, benefit from enhanced critical slowing down. The increase in lifetime is particularly important for nanometer scale fluctuation domains where the hybrid orientation and the other lipids composition are highly coupled.
Hybrid Airy Plasmons with Dynamically Steerable Trajectories
Li, Rujiang; Lin, Xiao; Wang, Huaping; Xu, Zhiwei; Chen, Hongsheng
2016-01-01
With the intriguing properties of diffraction-free, self-accelerating, and self-healing, Airy plasmons are promising to be used in the trapping, transporting, and sorting of micro-objects, imaging, and chip scale signal processing. However, the high dissipative loss and the lack of dynamical steerability restrict the implementation of Airy plasmons in these applications. Here we reveal the hybrid Airy plasmons for the first time by taking a hybrid graphene-based plasmonic waveguide in the terahertz (THz) domain as an example. Due to the coupling between an optical mode and a plasmonic mode, the hybrid Airy plasmons can have large propagation lengths and effective transverse deflections, where the transverse waveguide confinements are governed by the hybrid modes with moderate quality factors. Meanwhile, the propagation trajectories of hybrid Airy plasmons are dynamically steerable by changing the chemical potential of graphene. These hybrid Airy plasmons may promote the further discovery of non-diffracting be...
Hybrid Airy plasmons with dynamically steerable trajectories.
Li, Rujiang; Imran, Muhammad; Lin, Xiao; Wang, Huaping; Xu, Zhiwei; Chen, Hongsheng
2017-01-26
With their intriguing diffraction-free, self-accelerating, and self-healing properties, Airy plasmons show promise for use in the trapping, transporting, and sorting of micro-objects, imaging, and chip scale signal processing. However, high dissipative loss and lack of dynamical steerability restrict the implementation of Airy plasmons in these applications. Here we reveal hybrid Airy plasmons for the first time by taking a hybrid graphene-based plasmonic waveguide in the terahertz (THz) domain as an example. Due to coupling between optical modes and plasmonic modes, the hybrid Airy plasmons can have large propagation lengths and effective transverse deflections, where the transverse waveguide confinements are governed by the hybrid modes with moderate quality factors. Meanwhile, the propagation trajectories of the hybrid Airy plasmons are dynamically steerable by changing the chemical potential of graphene. These hybrid Airy plasmons may promote the further discovery of non-diffracting beams along with the emerging developments of optical tweezers and tractor beams.
Dossa, Gbadamassi G. O.; Paudel, Ekananda; Cao, Kunfang; Schaefer, Douglas; Harrison, Rhett D.
2016-01-01
Organic matter decomposition represents a vital ecosystem process by which nutrients are made available for plant uptake and is a major flux in the global carbon cycle. Previous studies have investigated decomposition of different plant parts, but few considered bark decomposition or its role in decomposition of wood. However, bark can comprise a large fraction of tree biomass. We used a common litter-bed approach to investigate factors affecting bark decomposition and its role in wood decomposition for five tree species in a secondary seasonal tropical rain forest in SW China. For bark, we implemented a litter bag experiment over 12 mo, using different mesh sizes to investigate effects of litter meso- and macro-fauna. For wood, we compared the decomposition of branches with and without bark over 24 mo. Bark in coarse mesh bags decomposed 1.11–1.76 times faster than bark in fine mesh bags. For wood decomposition, responses to bark removal were species dependent. Three species with slow wood decomposition rates showed significant negative effects of bark-removal, but there was no significant effect in the other two species. Future research should also separately examine bark and wood decomposition, and consider bark-removal experiments to better understand roles of bark in wood decomposition. PMID:27698461
Strain phase separation: Formation of ferroelastic domain structures
Xue, Fei; Li, Yongjun; Gu, Yijia; Zhang, Jinxing; Chen, Long-Qing
2016-12-01
Phase decomposition is a well-known process leading to the formation of two-phase mixtures. Here we show that a strain imposed on a ferroelastic crystal promotes the formation of mixed phases and domains, i.e., strain phase separation with local strains determined by a common tangent construction on the free energy versus strain curves. It is demonstrated that a domain structure can be understood using the concepts of domain/phase rule, lever rule, and coherent and incoherent strain phase separation, in a complete analogy to phase decomposition. The proposed strain phase separation model is validated using phase-field simulations and experimental observations of PbTi O3 and BiFe O3 thin films as examples. The proposed model provides a simple tool to guide and design domain structures of ferroelastic systems.
Parallel Algorithms for Graph Optimization using Tree Decompositions
Energy Technology Data Exchange (ETDEWEB)
Sullivan, Blair D [ORNL; Weerapurage, Dinesh P [ORNL; Groer, Christopher S [ORNL
2012-06-01
Although many $\\cal{NP}$-hard graph optimization problems can be solved in polynomial time on graphs of bounded tree-width, the adoption of these techniques into mainstream scientific computation has been limited due to the high memory requirements of the necessary dynamic programming tables and excessive runtimes of sequential implementations. This work addresses both challenges by proposing a set of new parallel algorithms for all steps of a tree decomposition-based approach to solve the maximum weighted independent set problem. A hybrid OpenMP/MPI implementation includes a highly scalable parallel dynamic programming algorithm leveraging the MADNESS task-based runtime, and computational results demonstrate scaling. This work enables a significant expansion of the scale of graphs on which exact solutions to maximum weighted independent set can be obtained, and forms a framework for solving additional graph optimization problems with similar techniques.
Parallel Algorithms for Graph Optimization using Tree Decompositions
Energy Technology Data Exchange (ETDEWEB)
Weerapurage, Dinesh P [ORNL; Sullivan, Blair D [ORNL; Groer, Christopher S [ORNL
2013-01-01
Although many NP-hard graph optimization problems can be solved in polynomial time on graphs of bounded tree-width, the adoption of these techniques into mainstream scientific computation has been limited due to the high memory requirements of required dynamic programming tables and excessive running times of sequential implementations. This work addresses both challenges by proposing a set of new parallel algorithms for all steps of a tree-decomposition based approach to solve maximum weighted independent set. A hybrid OpenMP/MPI implementation includes a highly scalable parallel dynamic programming algorithm leveraging the MADNESS task-based runtime, and computational results demonstrate scaling. This work enables a significant expansion of the scale of graphs on which exact solutions to maximum weighted independent set can be obtained, and forms a framework for solving additional graph optimization problems with similar techniques.
General Services Administration — This dataset offers the list of all .gov domains, including state, local, and tribal .gov domains. It does not include .mil domains, or other federal domains outside...
Institute of Scientific and Technical Information of China (English)
黄源源; 李建平
2011-01-01
提出一种新的人脸特征描述方法.使用 Contourlet 变换提取人脸图像低频子带,并对子带图像适当分块从而减少图像局部扭曲对识别的影响,利用混合投影函数和图像熵提取特征从而构建混合投影特征矩阵.在 ORL、Yale、CMU PIE 人脸数据库的实验表明该方法具有一定的优势.%This paper proposes a new facial image feature description method.This method uses the Contourlet transform to get the low frequency sub-band and divides the sub-band image into several appropriate non-overlapping blocks so that the local image distortion will less affect the recognition result. It uses the hybrid projection function and image entropy to extract the features and construct the hybrid projection feature vector. The experimental results on ORL, Yale and CMU PIE face databases demonstrate that the new method is competitive.
时域反相对称与扩频技术的混合技术研究%Hybrid Technology of Time Domain Phase-inversion Symmetry and Spread Spectrum
Institute of Scientific and Technical Information of China (English)
冯德武; 谭旭
2011-01-01
According to the relativity of noise in time domain and the antinoise principle of time domain phase-inversion symme-tric method, a novel spread spectrum communication method is proposed in combination with phase-inversion symmetric method and spread spectrum communication. The simulation and experimental verification indicate that the time domain phase-inversion symmetric and spread spectrum system can get higher output SNR, and under the same transmission conditions, capability of phase-inversion symmetric spread spectrum technology is superior to the general spread spectrum technology.%根据噪声在时域上的相关性以及反相对称法的抗噪原理,将反相对称法与扩频通信相结合,提出了一种新的扩频通信方法.通过仿真和实验验证表明,时域反相对称扩频技术能使系统获得较高的输出信噪比,且在相同的传输条件下,反相对称扩频技术的性能优于一般的扩频技术.
A direct product decomposition of QMV algebras
Institute of Scientific and Technical Information of China (English)
LU Xian; SHANG Yun; LU RuQian
2012-01-01
We study the direct product decomposition of quantum many-valued algebras (QMV algebras)which generalizes the decomposition theorem of ortholattices (orthomodular lattices).In detail,for an idempotent element of a given QMV algebra,if it commutes with every element of the QMV algebra,it can induce a direct product decomposition of the QMV algebra.At the same time,we introduce the commutant C(S) of a set S in a QMV algebra,and prove that when S consists of idempotent elements,C(S) is a subalgebra of the QMV algebra.This also generalizes the cases of orthomodular lattices.
On a Decomposition Model for Optical Flow
Abhau, Jochen; Belhachmi, Zakaria; Scherzer, Otmar
In this paper we present a variational method for determining cartoon and texture components of the optical flow of a noisy image sequence. The method is realized by reformulating the optical flow problem first as a variational denoising problem for multi-channel data and then by applying decomposition methods. Thanks to the general formulation, several norms can be used for the decomposition. We study a decomposition for the optical flow into bounded variation and oscillating component in greater detail. Numerical examples demonstrate the capabilities of the proposed approach.
Solid state exchange reactions and thermal decomposition
Energy Technology Data Exchange (ETDEWEB)
Albarran, G.; Archundia, C.; Maddock, A.G.
1982-01-01
A further study of exchange of the cobalt atoms in solid Co(H/sub 2/O)/sub 6/(Co EDTA)/sub 2/ x 4H/sub 2/O has been made. The exchange is more easily measured when the compound has been ..gamma.. irradiated before heating. Without irradiation the exchange is complicated by substantial concurrent thermal decomposition. Vacuum dehydration to the tetrahydrate can be effected at 366 K without appreciable exchange. A relation between exchange, annealing of radiolytic decomposition and thermal decomposition in such compounds is suggested.
Hermann, Verena; Käser, Martin; Castro, Cristóbal E.
2011-02-01
We present a Discontinuous Galerkin finite element method using a high-order time integration technique for seismic wave propagation modelling on non-conforming hybrid meshes in two space dimensions. The scheme can be formulated to achieve the same approximation order in space and time and avoids numerical artefacts due to non-conforming mesh transitions or the change of the element type. A point-wise Gaussian integration along partially overlapping edges of adjacent elements is used to preserve the schemes accuracy while providing a higher flexibility in the problem-adapted mesh generation process. We describe the domain decomposition strategy of the parallel implementation and validate the performance of the new scheme by numerical convergence test and experiments with comparisons to independent reference solutions. The advantage of non-conforming hybrid meshes is the possibility to choose the mesh spacing proportional to the seismic velocity structure, which allows for simple refinement or coarsening methods even for regular quadrilateral meshes. For particular problems of strong material contrasts and geometrically thin structures, the scheme reduces the computational cost in the sense of memory and run-time requirements. The presented results promise to achieve a similar behaviour for an extension to three space dimensions where the coupling of tetrahedral and hexahedral elements necessitates non-conforming mesh transitions to avoid linking elements in form of pyramids.
Unimolecular thermal decomposition of dimethoxybenzenes
Robichaud, David J.; Scheer, Adam M.; Mukarakate, Calvin; Ormond, Thomas K.; Buckingham, Grant T.; Ellison, G. Barney; Nimlos, Mark R.
2014-06-01
The unimolecular thermal decomposition mechanisms of o-, m-, and p-dimethoxybenzene (CH3O-C6H4-OCH3) have been studied using a high temperature, microtubular (μtubular) SiC reactor with a residence time of 100 μs. Product detection was carried out using single photon ionization (SPI, 10.487 eV) and resonance enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry and matrix infrared absorption spectroscopy from 400 K to 1600 K. The initial pyrolytic step for each isomer is methoxy bond homolysis to eliminate methyl radical. Subsequent thermolysis is unique for each isomer. In the case of o-CH3O-C6H4-OCH3, intramolecular H-transfer dominates leading to the formation of o-hydroxybenzaldehyde (o-HO-C6H4-CHO) and phenol (C6H5OH). Para-CH3O-C6H4-OCH3 immediately breaks the second methoxy bond to form p-benzoquinone, which decomposes further to cyclopentadienone (C5H4=O). Finally, the m-CH3O-C6H4-OCH3 isomer will predominantly follow a ring-reduction/CO-elimination mechanism to form C5H4=O. Electronic structure calculations and transition state theory are used to confirm mechanisms and comment on kinetics. Implications for lignin pyrolysis are discussed.
Geometric decompositions of collective motion
Mischiati, Matteo; Krishnaprasad, P. S.
2017-04-01
Collective motion in nature is a captivating phenomenon. Revealing the underlying mechanisms, which are of biological and theoretical interest, will require empirical data, modelling and analysis techniques. Here, we contribute a geometric viewpoint, yielding a novel method of analysing movement. Snapshots of collective motion are portrayed as tangent vectors on configuration space, with length determined by the total kinetic energy. Using the geometry of fibre bundles and connections, this portrait is split into orthogonal components each tangential to a lower dimensional manifold derived from configuration space. The resulting decomposition, when interleaved with classical shape space construction, is categorized into a family of kinematic modes-including rigid translations, rigid rotations, inertia tensor transformations, expansions and compressions. Snapshots of empirical data from natural collectives can be allocated to these modes and weighted by fractions of total kinetic energy. Such quantitative measures can provide insight into the variation of the driving goals of a collective, as illustrated by applying these methods to a publicly available dataset of pigeon flocking. The geometric framework may also be profitably employed in the control of artificial systems of interacting agents such as robots.
Thermal Decomposition Kinetics of HMX
Energy Technology Data Exchange (ETDEWEB)
Burnham, A K; Weese, R K
2004-11-18
Nucleation-growth kinetic expressions are derived for thermal decomposition of HMX from a variety of thermal analysis data types, including mass loss for isothermal and constant rate heating in an open pan and heat flow for isothermal and constant rate heating in open and closed pans. Conditions are identified in which thermal runaway is small to nonexistent, which typically means temperatures less than 255 C and heating rates less than 1 C/min. Activation energies are typically in the 140 to 165 kJ/mol range for open pan experiments and about 150 to 165 kJ/mol for sealed pan experiments. Our activation energies tend to be slightly lower than those derived from data supplied by the University of Utah, which we consider the best previous thermal analysis work. The reaction clearly displays more than one process, and most likely three processes, which are most clearly evident in open pan experiments. The reaction is accelerated in closed pan experiments, and one global reaction appears to fit the data well. Comparison of our rate measurements with additional literature sources for open and closed low temperature pyrolysis from Sandia gives a likely activation energy of 165 kJ/mol at 10% conversion.
Thermal Decomposition Kinetics of HMX
Energy Technology Data Exchange (ETDEWEB)
Burnham, A K; Weese, R K
2004-05-05
Nucleation-growth kinetic expressions are derived for thermal decomposition of HMX from a variety of types of data, including mass loss for isothermal and constant rate heating in an open pan, and heat flow for isothermal and constant rate heating in open and closed pans. Conditions are identified in which thermal runaway is small to nonexistent, which typically means temperatures less than 255 C and heating rates less than 1 C/min. Activation energies are typically in the 140 to 150 kJ/mol regime for open pan experiments and about 160 kJ/mol for sealed pan experiments. Our activation energies are about 10% lower than those derived from data supplied by the University of Utah, which we consider the best previous work. The reaction clearly displays more than one process, and most likely three processes, which are most clearly evident in open pan experiments. The reaction is accelerated for closed pan experiments, and one global reaction appears to fit the data well.
Thermal Decomposition Kinetics of HMX
Energy Technology Data Exchange (ETDEWEB)
Burnham, A K; Weese, R K
2005-03-17
Nucleation-growth kinetic expressions are derived for thermal decomposition of HMX from a variety of types of data, including mass loss for isothermal and constant rate heating in an open pan, and heat flow for isothermal and constant rate heating in open and closed pans. Conditions are identified in which thermal runaway is small to nonexistent, which typically means temperatures less than 255 C and heating rates less than 1 C/min. Activation energies are typically in the 140 to 165 kJ/mol regime for open pan experiments and about 150-165 kJ/mol for sealed-pan experiments. The reaction clearly displays more than one process, and most likely three processes, which are most clearly evident in open pan experiments. The reaction is accelerated for closed pan experiments, and one global reaction fits the data fairly well. Our A-E values lie in the middle of the values given in a compensation-law plot by Brill et al. (1994). Comparison with additional open and closed low temperature pyrolysis experiments support an activation energy of 165 kJ/mol at 10% conversion.
A four-stage hybrid model for hydrological time series forecasting.
Di, Chongli; Yang, Xiaohua; Wang, Xiaochao
2014-01-01
Hydrological time series forecasting remains a difficult task due to its complicated nonlinear, non-stationary and multi-scale characteristics. To solve this difficulty and improve the prediction accuracy, a novel four-stage hybrid model is proposed for hydrological time series forecasting based on the principle of 'denoising, decomposition and ensemble'. The proposed model has four stages, i.e., denoising, decomposition, components prediction and ensemble. In the denoising stage, the empirical mode decomposition (EMD) method is utilized to reduce the noises in the hydrological time series. Then, an improved method of EMD, the ensemble empirical mode decomposition (EEMD), is applied to decompose the denoised series into a number of intrinsic mode function (IMF) components and one residual component. Next, the radial basis function neural network (RBFNN) is adopted to predict the trend of all of the components obtained in the decomposition stage. In the final ensemble prediction stage, the forecasting results of all of the IMF and residual components obtained in the third stage are combined to generate the final prediction results, using a linear neural network (LNN) model. For illustration and verification, six hydrological cases with different characteristics are used to test the effectiveness of the proposed model. The proposed hybrid model performs better than conventional single models, the hybrid models without denoising or decomposition and the hybrid models based on other methods, such as the wavelet analysis (WA)-based hybrid models. In addition, the denoising and decomposition strategies decrease the complexity of the series and reduce the difficulties of the forecasting. With its effective denoising and accurate decomposition ability, high prediction precision and wide applicability, the new model is very promising for complex time series forecasting. This new forecast model is an extension of nonlinear prediction models.
Collective identity formation in hybrid organizations.
Boulongne, Romain; Boxenbaum, Eva
2015-01-01
International audience; The present article examines the process of collective identity formation in the context of hybrid organizing. Empirically, we investigate hybrid organizing in a collaborative structure at the interface of two heterogeneous organizations in the domain of new renewable energies. We draw on the literature on knowledge sharing across organizational boundaries, particularly the notions of transfer, translation and transformation, to examine in real time how knowledge shari...
The decomposition of estuarine macrophytes under different ...
African Journals Online (AJOL)
2013-04-29
Apr 29, 2013 ... versity and recreational value (Hanisak, 1993; Pedersen and. Borum, 1996 ... in providing organic matter to detrital food chains, or alter- natively ..... Moreover, when assessing the SRP released during decomposition for each.
Directional Filters for Cartoon + Texture Image Decomposition
Directory of Open Access Journals (Sweden)
Antoni Buades
2016-05-01
Full Text Available We present in this article a detailed analysis and implementation of the cartoon+texture decomposition algorithm proposed in [A. Buades, J.L. Lisani, 'Directional filters for color cartoon + texture image and video decomposition', Journal of Mathematical Imaging and Vision, 2015]. This method follows the approach proposed by [A. Buades, T. Le, J-M. Morel, L. Vese, 'Cartoon+Texture Image Decomposition', IPOL 2011], based on low/high-pass filtering, but replaces the isotropic filters by a bank of low-pass directional filters. The cartoon image is obtained by filtering in the direction that leads to the largest local total variation rate reduction. This permits to improve the performance of the decomposition near image discontinuities, where an halo effect was produced by the previous method.
Gravity localization on hybrid branes
Energy Technology Data Exchange (ETDEWEB)
Veras, D.F.S., E-mail: franklin@fisica.ufc.br [Universidade Federal do Ceará (UFC), Departamento de Física, Campus do Pici, Caixa Postal 6030, 60455-760, Fortaleza, Ceará (Brazil); Cruz, W.T., E-mail: wilamicruz@gmail.com [Instituto Federal de Educação, Ciência e Tecnologia do Ceará (IFCE), Campus Juazeiro do Norte, 63040-540 Juazeiro do Norte, Ceará (Brazil); Maluf, R.V., E-mail: r.v.maluf@fisica.ufc.br [Universidade Federal do Ceará (UFC), Departamento de Física, Campus do Pici, Caixa Postal 6030, 60455-760, Fortaleza, Ceará (Brazil); Almeida, C.A.S., E-mail: carlos@fisica.ufc.br [Universidade Federal do Ceará (UFC), Departamento de Física, Campus do Pici, Caixa Postal 6030, 60455-760, Fortaleza, Ceará (Brazil)
2016-03-10
This work deals with gravity localization on codimension-1 brane worlds engendered by compacton-like kinks, the so-called hybrid branes. In such scenarios, the thin brane behavior is manifested when the extra dimension is outside the compact domain, where the energy density is non-trivial, instead of asymptotically as in the usual thick brane models. The zero mode is trapped in the brane, as required. The massive modes, although not localized in the brane, have important phenomenological implications such as corrections to the Newton's law. We study such corrections in the usual thick domain wall and in the hybrid brane scenarios. By means of suitable numerical methods, we attain the mass spectrum for the graviton and the corresponding wavefunctions. The spectra possess the usual linearly increasing behavior from the Kaluza–Klein theories. Further, we show that the 4D gravitational force is slightly increased at short distances. The first eigenstate contributes highly for the correction to the Newton's law. The subsequent normalized solutions have diminishing contributions. Moreover, we find out that the phenomenology of the hybrid brane is not different from the usual thick domain wall. The use of numerical techniques for solving the equations of the massive modes is useful for matching possible phenomenological measurements in the gravitational law as a probe to warped extra dimensions.