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ON IMPROVING THE computational-efficiency OF DIGITAL LIGHTWAVE LINK SIMULATION

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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Coarse-graining simulation approaches for polymer melts: the effect of potential range on computational efficiency

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SOFT MATTER 2018年第35期14卷 7126-7144页

作者： Dinpajooh, Mohammadhasan Guenza, Marina G. Univ Oregon Dept Chem & Biochem Eugene OR 97403 USA Univ Oregon Inst Theoret Sci Eugene OR 97403 USA

The integral equation coarse-graining (IECG) approach is a promising high-level coarse-graining (CG) method for polymer melts, with variable resolution from soft spheres to multi CG sites, which preserves the structural and thermodynamical consistencies with the related atomistic simulations. When compared to the atomistic description, the procedure of coarse-graining results in smoother free energy surfaces, longer-ranged potentials, a decrease in the number of interaction sites for a given polymer, and more. Because these changes have competing effects on the computational efficiency of the CG model, care needs to be taken when studying the effect of coarse-graining on the computational speed-up in CG molecular dynamics simulations. For instance, treatment of long-range CG interactions requires the selection of cutoff distances that include the attractive part of the effective CG potential and force. In particular, we show how the complex nature of the range and curvature of the effective CG potential, the selection of a suitable CG timestep, the choice of the cutoff distance, the molecular dynamics algorithms, and the smoothness of the CG free energy surface affect the efficiency of IECG simulations. By direct comparison with the atomistic simulations of relatively short chain polymer melts, we find that the overall computational efficiency is highest for the highest level of CG (soft spheres), with an overall improvement of the computational efficiency being about 10(6)-10(8) for various CG levels/resolutions. Therefore, the IECG method can have important applications in molecular dynamics simulations of polymeric systems. Finally, making use of the standard spatial decomposition algorithm, the parallel scalability of the IECG simulations for various levels of CG is presented. Optimal parallel scaling is observed for a reasonably large number of processors. Although this study is performed using the IECG approach, its results on the relation between the level of

关键词： computational efficiency

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An Unsupervised Clustering Method for Processing Roadside LiDAR Data With Improved computational efficiency

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IEEE SENSORS JOURNAL 2022年第11期22卷 10684-10691页

作者： Zhang, Yibin Bhattarai, Nischal Zhao, Junxuan Liu, Hongchao Xu, Hao Texas Tech Univ Dept Civil Environm & Construct Engn Lubbock TX 79409 USA Univ Nevada Dept Civil & Environm Engn Reno NV 89557 USA

In transportation, LiDAR has been primarily used in autonomous vehicles to assist self-driving until recently when people realized it could also be installed at the roadside to support connected vehicles and infrastructure systems. Unlike onboard LiDAR sensors used in autonomous vehicles, roadside applications must perform complete background filtering and clustering as well as tracking real-time traffic movements within the detection zone. This paper presents an unsupervised clustering method for roadside or infrastructure-based LiDAR applications. It first converts 3D LiDAR data points into 2D so that only target points (after background filtering) will be saved in the channel-azimuth 2D structure;then, a method combining the region growing algorithm and counted component labeling is used to perform clustering. Lastly, a merging process is conducted to enhance the connected component labeling method for better outcomes. Experimental studies demonstrate that the proposed method could reach 0.011s per frame (10 Hz sensor rotation frequency) in clustering while maintaining high accuracy.

关键词： Laser radar Sensors Roads Laser beams Data structures Point cloud compression Labeling Connected component labeling computational efficiency object clustering region growing roadside LiDAR

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Accuracy and computational efficiency of dealiasing schemes for the DNS of under resolved flows with strong gradients

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MATHEMATICS AND COMPUTERS IN SIMULATION 2021年 182卷 116-142页

作者： Sinhababu, Arijit Ayyalasomayajula, Sathyanarayana IIT Bhubaneswar Sch Mech Sci Khurja India

In this paper, we have studied the effect of residual aliasing error of the second order Runge-Kutta (RK2) based Random Phase Shift Method (RPSM) which shows smoothing effect in the solution of under-resolved flows involving strong gradients. Firstly, we show that RPSM is almost as accurate as the fully dealiased 3/2 Padding scheme but with similar computational cost as the fast 2/3 Truncation scheme. Secondly, we show that RPSM has high accuracy in the case of under-resolved shear layer and Surface Quasi-Geostrophic (SQG) flows. Further, we show that the 2/3 Truncation scheme turns more computationally expensive than 3/2 Padding or RPSM when we try to achieve the same level of accuracy. Filtering based dealiasing schemes are found to be an inappropriate choice for a variety of flow problems because they are prone to unphysical parasitic currents. For the first time error norm based computational efficiency, i.e., high accuracy at the lower computational cost of RPSM scheme is shown. Although some artifacts of dealiasing remain due to Fourier windowing in RPSM, it is found to be numerically stable even in under-resolved conditions at later simulation time. We have validated our numerical results with the analytical ones and also with the previous literature. (C) 2020 International Association for Mathematics and Computers in Simulation (IMACS). Published by Elsevier B.V. All rights reserved.

关键词： Strong gradients Shear layers Strong shocks Dealiasing computational efficiency DNS

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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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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 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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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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Improving the computational efficiency of highway alignment optimization models through a stepwise genetic algorithms approach

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TRANSPORTATION RESEARCH PART B-METHODOLOGICAL 2005年第4期39卷 339-360页

作者： Kim, E Jha, MK Son, B Morgan State Univ Dept Civil Engn Baltimore MD 21251 USA Univ Incheon Dept Civil & Environm Syst Engn Inchon 402749 South Korea Yonsei Univ Dept Urban Planning & Engn Yonsei South Korea

In this paper we propose a stepwise genetic algorithms approach for optimizing highway alignments for improving computational efficiency and quality of solutions. Our previous work in highway alignment optimization has demonstrated that computational burden is a significant issue when working with a geographic information system (GIS) database requiring numerous spatial analyses. For solving real-world problems working directly with real maps through a GIS is highly desirable. Further-more. saving computation time can enhance adoptability of a model especially when a study area is relatively large. or involves many sensitive properties, or if locating complex structures such as intersections. bridges and tunnels is necessary. It is well acknowledged that in many optimization processes subdividing large problems into smaller pieces can decrease the computation time and produce a better solution. In this research two different population sizes are used to develop a stepwise alignment optimization when employing genetic algorithms in suitably subdivided study areas. An example study shows that the proposed stepwise optimization gives more efficient results than the existing methods and also improves quality of solutions. (C) 2004 Elsevier Ltd. All rights reserved.

关键词： stepwise optimization genetic algorithms computational efficiency highway alignment optimization geographic information system segmentation

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Improving computational efficiency in global river models by implementing the local inertial flow equation and a vector-based river network map

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WATER RESOURCES RESEARCH 2013年第11期49卷 7221-7235页

作者： Yamazaki, Dai de Almeida, Gustavo A. M. Bates, Paul D. Univ Bristol Sch Geog Sci Bristol BS8 1SS Avon England

Global river models are an essential tool for both earth system studies and water resources assessments. As advanced physical processes have been implemented in global river models, increasing computational cost has become problematic for executing ensemble or long-term simulations. To improve computational efficiency, we here propose the use of a local inertial flow equation combined with a vector-based river network map. A local inertial equation, a simplified formulation of the shallow water equations, was introduced to replace a diffusion wave equation. A vector-based river network map which flexibly discretizes river segments was adopted in order to replace the traditional grid-based map which is based on a Cartesian grid coordinate system. The computational efficiency of the proposed flow routing and river network map was tested by executing hydrodynamic simulations with the CaMa-Flood global river model. The simulation results suggest that the computational efficiency can be improved by more than 300% by applying the local inertial equation. It can be improved by a further 60% by implementing the vector-based river network map instead of a grid-based map. It is found that the vector-based map with evenly distributed flow distances between calculation units allows longer time steps compared to the grid-based map because the latter has very short flow distances between calculation units at high latitudes which critically limit time step length. Considering the improvement in simulation speed, the local inertial equation, and a vector-based river network map are preferable in global hydrodynamic simulations with high computational demands such as ensemble or long-term experiments.

关键词： global river model inertial equation vector-based map computational efficiency

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