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A computer implementation OF 2.5-D COMMON-SHOT INVERSION

GEOPHYSICS 1991年第9期56卷 1384-1394页

作者： DONG, WJ EMANUEL, MJ BORDING, P BLEISTEIN, N CHEVRON EXPLORAT & PROD SERV HOUSTONTX 77236 MINNESOTA SUPERCOMP CTR INC TULSAOK 74135 COLORADO SCH MINES DEPT MATH & COMP SCICTR WAVE PHENOMENAGOLDENCO 80401

The computer implementation of a two-and-one-half dimensional (2.5-D) constant density prestack inversion formalism with laterally and depth-dependent background propagation speed is a Kirchhoff-type inversion, summing data from a line of receivers over traveltime curves in the depth-dependent background medium with weights determined from Born/Kirchhoff inversion theory. This theory predicts that the output will be a reflector map with peak amplitudes on each reflector being in known proportion to the angularly dependent geometrical optics reflection coefficient. The 2.5-D feature provides for out-of-plane spreading correction consistent with the prescribed background medium. The method is applied to a synthetic data set and to a physically modeled data set generated at the Seismic Acoustic Laboratory. The graphical output demonstrates the validity of the formalism as a Kirchhoff migration. Parameter estimation for the synthetic data confirmed the theory. Parameter estimation for the experimental data was less successful, partially due to problems with amplitude control in the original experiment and partially due to the limited aperture of the common-shot data, thereby suggesting that a common-offset inversion might be more useful for parameter estimation.

关键词： .set amplitude traveltime LATERALLY reflection Kirchhoff reflector coefficient RECEIVERS formalism aperture parameter estimation prestack inversion geometrical optics computer implementation common-shot propagation speed background medium

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computer implementation in the reconstruction of 2-D flow velocity fields in ultrasound doppler color imaging

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computerS IN BIOLOGY AND MEDICINE 1995年第6期25卷 495-503页

作者： Fei, DY Fu, CT Liu, DD Biomedical Engineering Program Virginia Commonwealth University Richmond VA 23298 U.S.A.

Doppler color imaging can easily render flow information within the vessels and simultaneously provide anatomic information for diagnostic purposes. However, the angle dependence problem of the Doppler velocity measurement is a significant barrier for continuing progress toward quantitative clinical applications of this technology. This paper presents a method and the computer implementation for reconstruction of the 2-D flow velocity field (angle independent) in ultrasound Doppler color imaging. Formulae for deriving angle independent velocity amplitude and angle direction from the color images acquired with a linear array transducer are given. The hardware configuration of the data acquiring and processing system is described. Major considerations in the development of algorithms, especially the strategies for reducing the computation time are presented.

关键词： ultrasound angle independence Doppler color imaging reconstruction of flow velocity field computer implementation

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Meshless methods: A review and computer implementation aspects

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MATHEMATICS AND computerS IN SIMULATION 2008年第3期79卷 763-813页

作者： Nguyen, Vinh Phu Rabczuk, Timon Bordas, Stephane Duflot, Marc Univ Glasgow Glasgow G12 8LT Lanark Scotland Univ Canterbury Dept Mech Engn Christchurch 1 New Zealand CENAERO B-6041 Gosselies Belgium

The aim of this manuscript is to give a practical overview of meshless methods (for solid mechanics) based on global weak forms through a simple and well-structured MATLAB code, to illustrate our discourse. The source code is available for download on our website and should help students and researchers get started with some of the basic meshless methods;it includes intrinsic and extrinsic enrichment, point collocation methods, several boundary condition enforcement schemes and corresponding test cases. Several one and two-dimensional examples in elastostatics are given including weak and strong discontinuities and testing different ways of enforcing essential boundary conditions. (C) 2008 IMACS. Published by Elsevier B.V. All rights reserved.

关键词： Meshless methods Intrinsic enrichment Extrinsic discontinuities computer implementation MATLAB

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3D Lattice Fracture Model: Theory and computer implementation

3D Lattice Fracture Model: Theory and Computer Implementatio...

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9th International Conference on Fracture and Damage Mechanics

作者： Qian, Z. Schlangen, E. Ye, G. van Breugel, K. Delft Univ Technol Microlab CEG NL-2600 AA Delft Netherlands

ISBN: (纸本)9780878492411

The lattice fracture model is presented in this paper, which is intended to simulate the fracture processes in multiphase materials to obtain the mechanical behavior in terms of load-displacement diagram and the cracks propagation. The basic procedures of lattice fracture analysis is that imposing a prescribed displacement on a lattice structure, finding the critical lattice element with the highest stress/strength ratio, removing it from the system and repeating until the system fails globally. One of the challenges in computer implementation of 3D lattice fracture model is the huge demand for computer memory. Matrix free technique is adopted to solve this problem.

关键词： Lattice Fracture Model Multiphase Materials computer implementation

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Phase field modeling and computer implementation: A review

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ENGINEERING FRACTURE MECHANICS 2022年 262卷 108234-108234页

作者： Zhuang, X. Zhou, S. Huynh, G. D. Areias, P. Rabczuk, T. Tongji Univ Coll Civil Engn Dept Geotech Engn Shanghai 200092 Peoples R China Leibniz Univ Hannover Inst Photon D-30167 Hannover Germany Bauhaus Univ Weimar Inst Struct Mech D-99423 Weimar Germany Univ Lisbon Inst Super Tecn Dept Mech Engn P-1649004 Lisbon Portugal Tongji Univ Inst Adv Study Shanghai 200092 Peoples R China

This paper presents an overview of the theories and computer implementation aspects of phase field models (PFM) of fracture. The advantage of PFM over discontinuous approaches to fracture is that PFM can elegantly simulate complicated fracture processes including fracture initiation, propagation, coalescence, and branching by using only a scalar field, the phase field. In addition, fracture is a natural outcome of the simulation and obtained through the solution of an additional differential equation related to the phase field. No extra fracture criteria are needed and an explicit representation of a crack surface as well as complex track crack procedures are avoided in PFM for fracture, which in turn dramatically facilitates the implementation. The PFM is thermodynamically consistent and can be easily extended to multi-physics problem by 'changing' the energy functional accordingly. Besides an overview of different PFMs, we also present comparative numerical benchmark examples to show the capability of PFMs.

关键词： Phase field Brittle fracture computer implementation Finite element method Hydraulic fracture

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An overview of the ANCF approach, justifications for its use, implementation issues, and future research directions

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MULTIBODY SYSTEM DYNAMICS 2023年第3-4期58卷 433-477页

作者： Shabana, Ahmed A. A. Univ Illinois Dept Mech & Ind Engn 842 West Taylor St Chicago IL 60607 USA

This paper presents an overview of the finite-element (FE) absolute nodal coordinate formulation (ANCF), provides justifications for its use, and discusses issues relevant to its proper computer implementation and interpretation of its numerical results. The paper discusses future research directions for using ANCF finite elements in new areas such as soft tissues and materials relevant to broader areas of computational engineering and science. Selection of coordinates, definitions of forces and moments, geometric interpretation of the position gradients, and noncommutativity of finite rotations are among the topics discussed. To address concerns associated with finite-rotation noncommutativity and definition of moments in flexible-body dynamics, the paper demonstrates that the interpolation order is not preserved when the finite-rotation sequence is changed. Position gradients, on the other hand, are unique and preserve the highest interpolation order. It is shown that, while the spin tensor used to define the ANCF generalized forces due to moment application is associated with a rigid frame defined by the polar decomposition theorem, explicit polar decomposition of the matrix of position-gradient vectors is not required. ANCF elements have features that distinguish them from conventional finite elements and make them suited for large-displacement analysis of multibody systems (MBS). Their displacement fields, which allow increasing interpolation order without increasing number of nodes or using noncommutative finite rotations, are the basis for developing lower-dimension consistent rotation-based formulations (CRBF) without lowering the interpolation order. Nonetheless, the continuum-kinematic description of fully parameterized ANCF elements cannot be ignored when interpreting the ANCF numerical results. This issue is particularly important when comparing ANCF results with solutions obtained using semi-continuum conventional beam and plate models and simplified an

关键词： Absolute nodal coordinate formulation (ANCF) computer implementation Noncommutativity of finite rotations Consistent rotation-based formulations (CRBF) Position-gradient vectors

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BAYES LINEAR COMPUTATION - CONCEPTS, implementation AND PROGRAMS

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STATISTICS AND COMPUTING 1995年第4期5卷 327-341页

作者： GOLDSTEIN, M WOOFF, DA UNIV DURHAM DEPT MATH SCIDURHAM DH1 3LEENGLAND

We demonstrate how Bayes linear methods, based on partial prior specifications, bring us quickly to the heart of otherwise complex problems, giving us natural and systematic tools for evaluating our analyses which are not readily available in the usual Bayes formalism. We illustrate the approach using an example concerning problems of prediction in a large brewery. We describe the computer language [B/D] (an acronym for beliefs adjusted by data), which implements the approach. [B/D] incorporates a natural graphical representation of the analysis, providing a powerful way of thinking about the process of knowledge formulation and criticism which is also accessible to non-technical users.

关键词： BAYES LINEAR METHODS computer implementation BELIEF ADJUSTMENT INFLUENCE DIAGRAMS MODELING INFORMATION FLOW VISUALIZING COMPLEX STRUCTURES MULTIVARIATE TIME SERIES PARTIAL PRIOR SPECIFICATIONS

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implementation of a variance reduction-based lower bound in a branch-and-bound algorithm for the quadratic assignment problem

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SIAM JOURNAL ON OPTIMIZATION 1997年第1期7卷 280-294页

作者： Pardalos, PM Ramakrishnan, KG Resende, MGC Li, Y UNIV FLORIDA DEPT IND & SYST ENGN GAINESVILLE FL 32611 USA AT&T BELL LABS MURRAY HILL NJ 07974 USA AT&T RES MURRAY HILL NJ 07974 USA SANWA FINANCIAL PROD CO NEW YORK NY 10055 USA

The efficient implementation of a branch-and-bound algorithm for the quadratic assignment problem (QAP), incorporating the lower bound based on variance reduction of Li, Pardalos, Ramakrishnan, and Resende (1994), is presented. A new data structure for efficient implementation of branch-and-bound algorithms for the QAP is introduced. Computational experiments with the branch-and-bound algorithm on different classes of QAP test problems are reported. The branch-and-bound algorithm using the new lower bounds is compared with the same algorithm utilizing the commonly applied Gilmore-Lawler lower bound. Both implementations use a greedy randomized adaptive search procedure for obtaining initial upper bounds. The algorithms report all optimal permutations. Optimal solutions for previously unsolved instances from the literature, of dimensions n = 16 and n = 20, have been found with the new algorithm. In addition, the new algorithm has been tested on a class of large data variance problems, requiring the examination of much fewer nodes of the branch-and-bound tree than the same algorithm using the Gilmore-Lawler lower bound.

关键词： combinatorial optimization quadratic assignment problem branch-and-bound GRASP computer implementation data structures hashing function hash table lower bound test problems

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Animal Shapes, Modal Analysis, and Visualization of Motion (IV): Geometric Constructions and implementation

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JOURNAL OF GEOMETRIC ANALYSIS 2023年第10期33卷 1-39页

作者： Yang, Jing Chen, Goong Wei, Chunqiu Sergeev, Alexey Huang, Jingtong Kaya Scully, Matthew M. Krantz, Steven G. Yao, Pengfei Guo, Tiexin Wang, Junmin Yang, Zhichun Chen, Ming-Chieh Beijing Inst Technol Sch Math & Stat Beijing 100081 Peoples R China Texas A&M Univ Dept Math College Stn TX 77843 USA Texas A&M Univ Inst Quantum Sci & Engn College Stn TX 77843 USA Natl Tsing Hua Univ Natl Ctr Theoret Sci Hsinchu Branch Hsinchu Taiwan Beijing Univ Civil Engn & Architecture Dept Math & Data Sci Beijing 100044 Peoples R China Washington Univ St Louis Dept Math St Louis MO 63130 USA Shanxi Univ Sch Math Key Lab Complex Syst & Data Sci Minist Educ Taiyuan 030006 Shanxi Peoples R China Cent South Univ Sch Math & Statistice Changsha 410075 Hunan Peoples R China Chongqing Normal Univ Sch Math & Statistice Chongqing 401331 Peoples R China Cheng Shiu Univ Dept Mech Engn Kaohsiung Taiwan

We address computer implementation and technology issues in geometric constructions for mathematical and computational modeling purposes, especially regarding 3D finite-element mesh generation for large scale scientific computation of partial differential equations in applications. This mesh generation process for irregular shapes is time-consuming and cannot be done by hand, and has long been recognized as a major bottle-neck in large-scale scientific computing. Significant computer skills and proficiency are required for the applied mathematicians and numerical analysts engaged in the process of 3D-geometry mesh generations. But these days specialty software packages are available that can expedite geometric constructions. Their applications are now the canonical way to carry out the needed numerics of grids. In fact, new technologies such as laser scan are now available which generate a point cloud that, through further processing to remedy some common types of defects, can further expedite the generation of mesh of high quality for complex geometries. In this paper, we use Geomagic Design X as the basic platform to construct CAD containing the underlying geometry from a point cloud. From this CAD, we can then generate finite element mesh by HyperMesh for solving partial differential equations. This paper is mostly survey and tutorial in nature in the hope of providing a somewhat self-contained account for the researcher working on shape analysis and geometric designs. Step-by-step procedures of computer work are explained, with four instances of concrete examples. Trouble-shooting for common mesh generation problems, whether from a point cloud or CAD such as the repair of overlapping regions, mutually penetrating finite elements, gaps and holes, are also indicated.

关键词： Geometric constructions Mesh generation computer implementation

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implementation issues concerning optimal operation control algorithms in low voltage microgrids 5

Implementation issues concerning optimal operation control a...

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5th International Symposium on Electrical and Electronics Engineering (ISEEE)

作者： Parol, Rafal Parol, Miroslaw Rokicki, Lukasz Warsaw Univ Technol Inst Theory Elect Engn Measurement & Informat Sys Warsaw Poland Warsaw Univ Technol Inst Elect Power Engn Warsaw Poland

ISBN: (纸本)9781538620595

This paper addresses the problem of optimal operation control of low voltage microgrids situated in rural areas. An approach basing on centralized control is presented. The concept relies on the Particle Swarm Optimization algorithm as a practical method to optimize the operating points in all controllable devices and on the power flow calculations carried out with the use of Newton-Raphson algorithm making it possible to ensure the non-violation of constraints. The main attention is paid to the issue of considering all the necessary implementation and deployment details, which is often underestimated and perceived as an easy and straightforward task, especially in comparison with the process of development of theoretical approach. The base for all considerations are the experiences gained during the work on RIGRID (Rural Intelligent Grid) project, aiming to provide the practical realization of microgrid concept working in real conditions in a rural area. First, the optimization problem formulation is shortly reviewed. Second, the issues of software application integration, proper cooperation between different software units and optimization program software architecture are addressed and discussed in detail. Then, some comments on other implementation details are given. Last but not least, summary and final conclusions are included.

关键词： low voltage microgrid optimal operation control rural areas centralized control logic computer implementation

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