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International Conference on Advanced Mechatronic systems (ICAMechS)

作者： Cun-suo Pang Nan Zhang Xiang-yang Lu National Key Laboratory for Electronic Measurement Technology Key Laboratory of Instrumentation Science and Dynamic Measurement of Ministry of Education North University of China Taiyuan China Second System Design Department of the Second Research Academy of CASIC Beijing China Electrical Engineering Department Electrical Engineering Department Zhengzhou China

Without considering the echo signal power changes caused by target distance changes during the accumulated time the traditional radar equation is hardly applied. We take account of the effects of velocity, signal-to-noise ratio during the processing time; a modified radar equation is built which can be used for long-time integration of weak targets with high speed. After analyzing the relation between detection range and target velocity, integration time with processing time, we draw the constraint conditions and the corresponding conclusions.

关键词： Radar Laboratories Silicon compounds Equations Instruments Power measurement Velocity measurement

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Torus/torus intersection

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Computer-Aided design and Applications 2011年第3期8卷 465-477页

作者： Liu, Xiao-Ming Liu, Chang-Yuan Yong, Jun-Hai Paul, Jean-Claude Tsinghua University Beijing China Command and Engineering College of Chemical Defense Beijing China Key Laboratory for Information System Security Ministry of Education Beijing China Tsinghua National Laboratory for Information Science and Technology Beijing China INRIA France

This paper presents a new algorithm for torus/torus intersection. The pre-image of the intersection in the parametric space of one torus is represented by an implicit equation. The pre-image is divided into one-valued function curve segments by characteristic points. The topological feature of these characteristic points is analyzed to obtain the structure of the pre-image. Intersection curves satisfying required precision are found by a self-adaptive refinement method. Experiment results are presented to illustrate the stability and efficiency of the method. © 2011 CAD Solutions, LLC.

关键词： Topology

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A Tabu Search Approach for Optimizing Server Placement in Distributed systems

A Tabu Search Approach for Optimizing Server Placement in Di...

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International Conference on Networking and Distributed Computing (ICNDC)

作者： Biyao Wang JinLin Wang Xue Liu National Network New Media Engineering Research Center Institute of Acoustics Chinese Academy of Sciences (CAS) Beijing China Key Laboratory of Network Communication System and Control Key Laboratory of Anhui Network Communication System and Control University of Science and Technology of China Hefei China

In distributed systems, the server placement problem in which a new server has to compete with existing servers for user requests is important in planning of constructing new business service sites. In addition to minimizing cost, competition-aware server placement also needs to maximize the benefit of building a new server. This paper proposes a Tabu Search approach to optimize the problem in general graphs. Results from the simulation experiments show that it do has a better performance than both of the Greedy Add and Greedy Remove algorithms.

关键词： Servers Search problems Buildings Business Planning Algorithm design and analysis Routing

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The uncertainty optimization of vehicle occupant restraint system based on interval number programming

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Qiche Gongcheng/Automotive Engineering 2011年第1期33卷 6-10页

作者： Li, Fangyi Li, Guangyao Zhang, Jiahong Sun, Guangyong Zhang, Zheng School of Automotive and Mechanical Engineering Changsha University of Science and Technology Changsha 410114 China Hunan University State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Changsha 410082 China Autoliv Vehicle Safety System Technical Center Co. Ltd Shanghai 201807 China

The uncertainty optimization of vehicle occupant restraint system is studied in this paper based on interval number programming. Firstly a simulation model for occupant restraint system is set up using MADYMO software with the model verified by tests. Then, a weighted injury criterion is taken as objective, and the stiffness and upper anchor position of seat belt, as well as the tearing force and stretch length of force limiter etc are selected as design variables with the stiffnesses of seat and knee bolster as uncertain variables, and the uncertainty optimization is transformed into certainty optimization by using interval number programming. Next, the surrogate models for objective and constraint functions are built with Latin hypercube experiment design, and by utilizing sequential quadratic programming and genetic algorithms as the solvers for inner and outer layers respectively, an optimization is performed. Finally the approximately optimum solutions of the parameters of occupant restraint system are obtained.

关键词： Stiffness

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Implicit Surface Reconstruction Based on Adaptive Clustering

Implicit Surface Reconstruction Based on Adaptive Clustering

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IEEE International Conference on Computer-Aided design and Computer Graphics

作者： Chao Zheng Hui Zhang Tsinghua University Beijing Beijing CN Key Laboratory for Information System Security Ministry of Education Beijing China School of Software Tsinghua University Beijing China Tsinghua National Laboratory for Information Science and Technology Beijing China

This paper presents an efficient method to reconstruct an implicit surface from a point cloud based on adaptive clustering. First, a novel approach, based on a hierarchical clustering tree with variation and normal constraints, is proposed for normal estimation of the point cloud. It simplifies the point cloud and reduces the amount of direction propagation paths in normal orientation. Second, an implicit surface is computed from the clustering tree by a feature preserving method, using adaptive plane fitting that considers the local feature and sharp areas of the point cloud. Finally, the results demonstrate the efficiency of our method for open, closed and unorganized models, and show that the resulting surfaces preserve the sharp features.

关键词： Surface reconstruction Computational modeling Least squares approximation Estimation Octrees Principal component analysis

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Multi-resolution Mesh Fitting by B-spline Surfaces for Reverse Engineering

Multi-resolution Mesh Fitting by B-spline Surfaces for Rever...

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IEEE International Conference on Computer-Aided design and Computer Graphics

作者： Sen Zhang Zhigang Li Hui Zhang Junhai Yong Tsinghua University Beijing Beijing CN Key Laboratory for Information System Security Ministry of Education Beijing China School of Software Tsinghua University Beijing China Tsinghua National Laboratory for Information Science and Technology Beijing China

This paper presents a new multi-resolution mesh fitting algorithm, extending the adaptive patch-based fitting scheme where each underlying quadrilateral is recursively subdivided into four sub-patches. In this paper, the G 1 continuity constraints, which mainly consist of perpendicular constraints and twist compatibility constraints, are deduced for B-spline patches. In order to construct a unique B-spline patch for each quadrilateral, the mesh vertices are applied in a least-square approximation, and the energy functions associated with a patch are minimized. In contrast to the original algorithm, this paper fits the mesh into B-spline patches instead of Bezier patches with G 1 continuity. The B-spline patches make the algorithm have more free control points to be used for optimizing the shape of the quadrilateral patches to achieve higher flexible patch control and less recursive times.

关键词： Spline Vectors Surface treatment Shape Adaptation models Equations design automation

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Prediction of the critical heat flux in subcooled flow boiling in round tube using an improved mechanistic model

Prediction of the critical heat flux in subcooled flow boili...

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18th International Conference on Nuclear Engineering, ICONE18

作者： Na, Yu Yu, Zhang National Key Laboratory of Science and Technology on Reactor System Design Technology Nuclear Power Institute of China Chengdu Sichuan 610041 China

ISBN: (纸本)9780791849323

Among the existing CHF models, the bubble crowding model and the liquid sublayer dryout model have been well accepted for subcooled flow boiling. But both of the two models couldn't give explanation about some details in the boiling crisis phenomenon according to photographic result. The aim of the present paper is to provide an improved synthesized model containing the characteristic of the above two models and then to give a comprehensive explanation about CHF. In the present model, the conservation equations of mass and energy are solved to derive the CHF formula. The length and velocity of the vapor blanket and the thickness of the liquid sublayer are needed. The quality and void fraction in bubble region and the core region are calculated by a homogeneous assumption. The vapor blanket length is thought to be equal to the Helmholtz wavelength and it is obtained from several parameters in the bubble region. The velocity of the vapor blanket is connected to the flow velocity of the bubble layer. The thickness of the sublayer is determined by a force balance on the vapor blanket, which is also related to the condition of the bubble region. About 1100 experimental points have been selected to verify the proposed model. Comparison between the predictions by the proposed model and the experimental result shows a good agreement that more than 90% of these data are predicted within ±20%. © 2010 by ASME.

关键词： Void fraction

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Wheel slip-sinkage and its prediction model of lunar rover

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Journal of Central South University 2010年第1期17卷 129-135页

作者：丁亮高海波邓宗全陶建国 Aerospace Mechanism and Control Key Laboratory of Fundamental Science for National Defense Harbin Institute of Technology State Key Laboratory of Robotics and System Ha rbin Institute of Technology

In order to investigate wheel slip-sinkage problem, which is important for the design, control and simulation of lunar rovers, experiments were carried out with a wheel-soil interaction test system to measure the sinkage of three types of wheels in dimension with wheel lugs of different heights and numbers under a series of slip ratios (0-0.6). The curves of wheel sinkage versus slip ratio were obtained and it was found that the sinkage with slip ratio of 0.6 is 3-7 times of the static sinkage. Based on the experimental results, the slip-sinkage principle of lunar's rover lugged wheels (including the sinkage caused by longitudinal flow and side flow of soil, and soil digging of wheel lugs) was analyzed, and corresponding calculation equations were derived. All the factors that can cause slip sinkage were considered to improve the conventional wheel-soil interaction model, and a formula of changing the sinkage exponent with the slip ratio was established. Mathematical model for calculating the sinkage of wheel according to vertical load and slip ratio was developed. Calculation results show that this model can predict the slip-sinkage of wheel with high precision, making up the deficiency of Wong-Reece model that mainly reflects longitudinal slip-sinkage.

关键词： lunar rover slip-sinkage loose lunar soil stress distribution slip ratio

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Parallel Spatial Hashing for Collision Detection of Deformable Surfaces

Parallel Spatial Hashing for Collision Detection of Deformab...

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IEEE International Conference on Computer-Aided design and Computer Graphics

作者： Wenshan Fan Bin Wang Jianliang Zhou Jiaguang Sun Tsinghua University Beijing Beijing CN Key Laboratory for Information System Security Ministry of Education of China China School of Software Tsinghua University China Tsinghua National Laboratory for Information Science and Technology China Beijing AeroSpace Control Center China

We present a fast collision detection method for deformable surfaces with parallel spatial hashing on GPU architecture. The efficient update and access of the uniform grid are exploited to accelerate the performance in our method. To deal with the inflexible memory system, which makes the building of stream data a challenging task on GPU, we propose to subdivide the whole workload into irregular segments and design an efficient evaluation algorithm, which employs parallel scan and stream compaction, to build the stream data in parallel. The load balancing is a key aspect that needs to be considered in the SIMD parallelism. We break the heavy and irregular collision computation down into lightweight part and heavyweight part, ensuring the later perfectly run in load balancing manner with each concurrent thread processes just a single collision. In practice, our approach can perform collision detection in tens of milliseconds on a PC with NVIDIAGTX 260 graphics card on benchmarks composed of millions of triangles. The results highlight our speedups over prior CPU-based and GPU-based algorithms.

关键词： Graphics processing unit Computational modeling Arrays Benchmark testing Compaction Deformable models Buildings

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Research on the influence of ocean condition on the oscillation in parallel double-channel

Research on the influence of ocean condition on the oscillat...

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18th International Conference on Nuclear Engineering, ICONE18

作者： Zhou, Linglan Hong, Zhang Department of Physic Engineering Tsinghua University China National Key Laboratory of Science and Technology on Reactor System Design Technology Nuclear Power Institute Of China China

ISBN: (纸本)9780791849323

In this paper, the flow oscillation in the parallel multichannel system has been studied under ocean condition with RELAP5/MC. A double-channel boiling system model is built using the code RELAP5/MC and it is proved to be capable of simulating the instable phenomena. The influences of rolling, heaving and inclination on the flow oscillation have been analyzed. The result shows that the effect of lengthways rolling on the oscillation in parallel channels can be ignored. The influence of athwartships rolling and heaving reveals resonance effect, that is, when the rolling cycle is close to the oscillation cycle and half cycle respectively, the oscillation would happen earlier, when the difference between the cycles is large, the impact of rolling can also be ignored. The influence of inclination on the oscillation in parallel channels is feeble. © 2010 by ASME.

关键词： Oscillating flow

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