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Reformulation of the Stochastic BEM to improve the computational efficiency in the prediction of the vibro-acoustic behaviour of structures with uncertainties

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JOURNAL OF SOUND AND VIBRATION 2013年第9期332卷 2132-2148页

作者： D'Amico, R. Pratellesi, A. Baldanzini, N. Pierini, M. Katholieke Univ Leuven Dept Mech Engn Div PMA B-3001 Heverlee Belgium Univ Florence Dipartimento Meccan & Tecnol Ind I-50139 Florence Italy

Non-determinism plays a crucial role in the prediction of the vibro-acoustic behaviour of structures. The Stochastic Boundary Element Method (SBEM) allows computing the average response of systems with geometrical uncertainties. The method consists in including such perturbations in the standard BEM formulation and adding a set of equations representative of the energetic behaviour. Due to the presence of unknown cross-products, the addition of a set of auxiliary equation is necessary to solve the problem. As a consequence, the system dimension becomes very large and the application of the methodology is limited to small models. This paper deals with a reformulation of the SBEM approach such that the system dimension is drastically decreased and the methodology can be applied to more complex cases. Moreover, the approach is extended to predict the variance of the field variable at no additional computational cost. After a theoretical introduction, the SBEM is applied to two-dimensional examples with pressure and velocity boundary conditions. The comparison with Monte Carlo simulations shows a good agreement of the results and a reduction in the computational load is achieved. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Uncertainty MUCL1 gene Monte Carlo technique computational efficiency methodology Auxiliary equation Stochastic

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ON IMPROVING THE computational-efficiency OF DIGITAL LIGHTWAVE LINK SIMULATION

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IEEE TRANSACTIONS ON COMMUNICATIONS 1990年第11期38卷 2040-2048页

作者： TOWNSEND, JK SHANMUGAN, KS UNIV KANSAS LAWRENCEKS 66045 COMDISCO SYST INC LAWRENCEKS 66045

Monte Carlo simulation can be used to estimate the bit error rate (BER) in digital lightwave communication links. However, when the link includes an avalanche photodetector (APD) receiver and is operating at a low BER, Monte Carlo simulation requires excessive execution time unless assumptions are made about the APD statistics. In this paper, we present techniques that reduce the computational resources required to estimate the BER for these systems by two orders of magnitude. We achieve the speed-up by developing a new, more efficient random number generation algorithm for APD shot noise, and applying a tail extrapolation technique to the conditional distributions at the sample-and-decide input in the receiver. Receiver thermal noise is handled analytically. Accurate BER estimates for an NRZ direct-detection system are obtained in approximately 1.5 CPU hours on a VAXstation II using a combination of these techniques.

关键词： computational efficiency computational modeling Bit error rate Photodetectors Gaussian noise Analytical models Optical noise Intersymbol interference Statistics Noise generators

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IMPROVED STRATEGY IN ANALYTIC SURFACE CALCULATION FOR MOLECULAR-SYSTEMS - HANDLING OF SINGULARITIES AND computational-efficiency

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JOURNAL OF computational CHEMISTRY 1993年第11期14卷 1272-1280页

作者： EISENHABER, F ARGOS, P European Molecular Biology Laboratory D‐69012 Heidelberg Germany

Computer methods for analytic surface calculations of molecular systems suffer from numerical instabilities and are CPU time consuming. In this article, we present proposals toward the solution of both problems. Singularities arise when nearly collinear triples of neighboring atoms or multiple vertices are encountered during the calculation. Topological decisions in analytic surface calculation algorithms (accessibility of vertices and arcs) are based upon the comparison of distances or angles. If two such numbers are nearly equal, then currently used computer programs may not resolve this ambiguity correctly and can subsequently fail. In this article, modifications in the analytic surface calculation algorithm are described that recognize singularities automatically and treat them appropriately without restarting parts of the computation. The computing time required to execute these alterations is minimal. The basic modification consists in defining an accuracy limit within which two values may be assumed as equal. The search algorithm has been reformulated to reduce the computational effort. A new set of formulas makes it possible to avoid mostly the extraction of square roots. Tests for small- and medium-sized intersection circles and for pairs of vertices with small vertex height help recognize fully buried circles and vertex pairs at an early stage. The new program can compute the complete topology of the surface and accessible surface area of the protein crambin in 1.50-4.29 s (on a single R:3000 processor of an SGI 4D/480) depending on the compactness of the conformation where the limits correspond to the fully extended or fully folded chain, respectively. The algorithm, implemented in a computer program, will be made available on request. (C) 1993 by John Wiley & Sons, Inc.

关键词： computational efficiency

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Framework of modelling concentric tube robot and comparison on computational efficiency

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MECCANICA 2017年第9期52卷 2201-2217页

作者： Liu, Shao T. Chen, Chao Monash Univ Dept Mech & Aerosp Engn Lab Mot Generat & Automat Melbourne Vic 3800 Australia

The continuum concentric tube robots (CCTRs) are infinite degree-of-freedom robots with elastic structure. The CCTRs have no distinct links/dedicated backbones and joints as the rigid-link robots and conventional continuum robots do. Their simple and flexible structure, along with the capability to be navigated actively, can benefit minimally-invasive surgical applications. However, modelling of the CCTRs is challenging due to the compliance of structure, and a significant number of frames involved. A framework is developed in this work, linking two modelling approaches. Furthermore, two variations of modelling approaches are derived by treating the key equations in different ways. The computational efficiencies of four modelling approaches are compared, in terms of the overall iteration time, number of iterations and the time for single iteration. The effect of iteration accuracy and step size on computational efficiency are investigated as well.

关键词： Concentric tube robot Kinetostatic modelling computational efficiency Continuum robot Minimally invasive surgery

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Improvement in robustness and computational efficiency of material models for finite element analysis of metal powder compaction and experimental validation

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INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY 2013年第5-8期68卷 1785-1795页

作者： Zadeh, Hossein Kashani Jeswiet, Jack Kim, Il Yong Queens Univ Dept Mat & Mech Eng Kingston ON Canada

In metal powder compaction, density nonuniformity can be a source of flaws. Material models in finite element analysis for the prediction of density distribution still lack robustness and are computationally expensive. In this work, the Drucker-Prager cap (DPC) material model is implemented into the commercial finite element (FE) software ABAQUS/Explicit using the user-subroutine VUMAT. Yield functions in this material model are pressure-dependent and the curvature of the cap yield surface is high. This can cause numerical instability. We implemented a sub-increment technique to address this instability problem in a previous paper (Kashani et al., Trans North Am Manuf Res Inst SME 38:623-631, 2010). The DPC model is also a non-smooth, multi-yield surface material model which has instability problems at the intersection of the yield surfaces;we adopted the corner region in the DPC material models for soils in order to remove instability and the results of which were presented in (Kashani et al., Trans North Am Manuf Res Inst SME 38:623-631, 2010). The computational efficiency of the DPC material model was improved using a novel technique to solve the constitutive equations analytically which was shown in a previous paper by the authors (Kashani et al., Trans North Am Manuf Res Inst SME 38:623-631, 2010). In this paper, experimental tests were conducted where cylindrically shaped parts were compacted from Distaloy AE iron-based powder to 7.0 g/cm(3) using 592 MPa of pressure. To measure local density, metallography and image processing were used to find the void area fraction of the surface. The FE results were compared to experimental results and it was shown that the FE analysis predicted local relative density within 3 % of the actual experimental measurements.

关键词： Metal powder compaction Constitutive equations Finite element method Numerical instability Numerical robustness computational efficiency

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Maximizing the computational efficiency of Temporary Housing Decision Support Following Disasters

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JOURNAL OF COMPUTING IN CIVIL ENGINEERING 2014年第1期28卷 113-123页

作者： El-Anwar, Omar Chen, Lei Univ Washington Dept Construct Management Seattle WA 98195 USA Cairo Univ Dept Struct Engn Cairo Egypt Univ Washington Dept Ind & Syst Engn Seattle WA 98195 USA

Postdisaster temporary housing has long been a challenging problem because of its interlinked socioeconomic, political, and financial dimensions. A significant need for automated decision support was obvious to address this problem. Previous research achieved considerable advancements in developing optimization models that can quantify and optimize the impacts of temporary housing decisions on the socioeconomic welfare of displaced families and total public expenditures on temporary housing as well as other objectives. However, the computational complexity of these models hindered its practical use and adoption by emergency planners. This article analyzes the computational efficiency of the current implementation of the most advanced socioeconomic formulation of the temporary housing problem, which uses integer programming. Moreover, it presents the development of a customized variant of the Hungarian algorithm that has a superior computational performance while maintaining the highest quality of solutions. An application example is presented to demonstrate the unique capabilities of the new algorithm in solving large-scale problems.

关键词： Housing Computation Disasters Decision support systems Temporary structures Temporary housing computational efficiency Optimization Disaster management Integer programming

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An Application of a Higher computational efficiency Method in Thermo-Hydraulic Calculations of First Wall in Fusion Blanket

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IEEE TRANSACTIONS ON PLASMA SCIENCE 2023年第12期51卷 3688-3695页

作者： Guo, Likai Wu, Xinghua Zhao, Shengqiang Huo, Minhan Southwestern Inst Phys Chengdu 610041 Sichuan Peoples R China Tsinghua Univ Beijing 100190 Peoples R China

In the field of computer science, computational efficiency is an important indicator for measuring computational methods. The internal structure of the fusion reactor blanket is complex and has a large spatial scale, making the computational cost of the overall thermal-hydraulic calculation particularly large. Therefore, it is necessary to optimize the computational efficiency. This article introduces a method to improve the computational efficiency of thermo-hydraulic calculations and presents a preliminary validation in the context of the first wall of a blanket. By contrasting different fitting methods for the thermophysical parameters of helium coolant in a helium-cooled solid breeder blanket, it is observed that utilizing a power function to fit helium density, with a similar fitting quality, leads to a certain degree of improvement in computational efficiency compared to commonly used multiple polynomial fitting, in the same order of magnitude. Subsequently, a method employing matrix correlation analysis for dimensionality reduction is proposed to increase the computational efficiency. Notably, there is a significant optimization in computational efficiency after applying dimensionality reduction. Furthermore, the proposed method is validated using User-Defined Functions (UDFs) within the commercial software FLUENT. Finally, by comparing the results of calculations using the power function density formula and matrix dimensionality reduction with theoretical hydraulic calculations, the optimized computational approach is found to yield reliable results.

关键词： computational efficiency Fitting Helium Correlation Mathematical models computational modeling Dimensionality reduction fusion reactor matrix correlation analysis thermal-hydraulics user-defined function (UDF)

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ON HOMOGENEOUS TRANSFORMS, QUATERNIONS, AND computational-efficiency

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IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION 1990年第3期6卷 382-388页

作者： FUNDA, J TAYLOR, RH PAUL, RP IBM CORP THOMAS J WATSON RES CTR YORKTOWN HTS NY 10598 USA

Three-dimensional modeling of rotations and translations in robot kinematics is most commonly performed using homogeneous transforms. An alternate approach, using quaternion-vector pairs as spatial operators, is compared with homogeneous transforms in terms of computational efficiency and storage economy. The conclusion drawn is that quaternion-vector pairs are as efficient as, more compact than, and more elegant than their matrix counterparts. A robust algorithm for converting rotational matrices into equivalent unit quaternions is described, and an efficient quaternion-based inverse kinematics solution for the Puma 560 robot arm is presented.< >

关键词： Quaternions computational efficiency Robot kinematics Robotics and automation Manipulator dynamics Automatic control Parallel robots Matrix converters Yttrium Process design

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The new paradigm of finite element solutions with overlapping elements in CAD - computational efficiency of the procedure

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COMPUTERS & STRUCTURES 2018年第Apr.期199卷 1-17页

作者： Zhang, Lingbo Kim, Ki-Tae Bathe, Klaus-Juergen MIT Cambridge MA 02139 USA

We consider the new paradigm of finite element analysis, present an effective overlapping finite element, and study the computational efficiency of the discretization scheme. The important new ingredient in the formulation of the overlapping element is that, unlike in meshless methods, we only use local polynomial functions in the displacement interpolations. We achieve this property by replacing the Shepard functions by local polynomials. As a consequence, the bandwidth of the resulting stiffness matrix for the overlapping finite element is much reduced when compared with earlier developments. We study the distortion insensitivity of the new overlapping finite element, the convergence properties and the required computational effort when compared with the use of the traditional 4-node finite element and that element with covers. The results show the overlapping element to be very promising, in particular in the new paradigm of analysis using finite elements in CAD. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： Finite elements Overlapping finite elements CAD & CAE Geometry clean-up Meshing computational efficiency

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USING LINEAR AND NONLINEAR PREDICTORS TO IMPROVE THE computational-efficiency OF THE FD-TD ALGORITHM

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IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 1994年第10期42卷 1992-1997页

作者： CHEN, J WU, C LO, TKY WU, KL LITVA, J COM DEV LTD DEPT CORP RES & DEVCAMBRIDGEONCANADA MCMASTER UNIV INTEGRATED ANTENNA GRPHAMILTONONCANADA

It is well known that the Finite-Difference Time-Domain (FD-TD) method requires long computation times for sol,ing electromagnetic problems, especially for high-Q structures. The reason for this is because the algorithm is based on the leap-frog formula. In this paper, both linear and nonlinear predictors, which are widely used in signal processing, are introduced to reduce the computation time of the FD-TD algorithm. A short segment of an FD-TD record is used to train the predictor, As long as the predictor is set up properly, an accurate future realization can be obtained. We demonstrate, by means of numerical results, that the efficiency of the FD-TD method can be improved by up to 90%. With this result, the FD-TD algorithm becomes a much more attractive technique for solving electromagnetic problems.

关键词： computational efficiency Signal processing algorithms Signal processing Finite difference methods Time domain analysis Electromagnetic transients Frequency Fourier transforms Parameter extraction

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