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12th International Conference on Computer-Aided design and Computer Graphics, CAD/Graphics 2011

作者： Hu, Kai-Mo Wang, Bin Yuan, Bin Yong, Jun-Hai School of Software Tsinghua University Beijing 100084 China Department of Computer Science and Technology Tsinghua University Beijing 100084 China Key Laboratory for Information System Security Ministry of Education Beijing 100084 China Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

ISBN: (纸本)9780769544977

Selecting the best views for 3D objects is useful for many applications. However, with the existing methods applied in CAD models, the results neither exhibit the 3D structures of the models fairly nor conform to human's browsing habits. In this paper, we present a robust method to generate the canonical views of CAD models, and the above problem is solved by considering the geometry and visual salient features simultaneously. We first demonstrate that for a CAD model, the three coordinate axes can be approximately determined by the scaled normals of its faces, such that the pose can be robustly normalized. A graph-based algorithm is also designed to accelerate the searching process. Then, a convex hull based method is applied to infer the upright orientation. Finally, four isometric views are selected as candidates, and the one whose depth image owns the most visual features is selected. Experiments on the Engineering Shape Benchmark (ESB) show that the views generated by our method are pleasant, informative and representative. We also apply our method in the calculation of model rectilinearity, and the results demonstrate its high performance. © 2011 IEEE.

关键词： Computer aided design

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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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12th International Conference on Computer-Aided design and Computer Graphics, CAD/Graphics 2011

作者： Zhang, Sen Li, Zhigang Zhang, Hui Yong, Junhai School of Software Tsinghua University Beijing 100084 China Department of Computer Science and Technology Tsinghua University Beijing 100084 China Key Laboratory for Information System Security Ministry of Education Beijing 100084 China Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

ISBN: (纸本)9780769544977

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 G1 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 Bézier patches with G1 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. © 2011 IEEE.

关键词： Reverse engineering

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An example-driven symbol recognition approach based on key features in engineering drawings

An example-driven symbol recognition approach based on key f...

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12th International Conference on Computer-Aided design and Computer Graphics, CAD/Graphics 2011

作者： Guo, Tiantian Zhang, Hui Wen, Yamei School of Software Tsinghua University Beijing 100084 China Key Laboratory for Information System Security Ministry of Education Beijing 100084 China Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

ISBN: (纸本)9780769544977

In this paper, we present an example-driven symbol recognition algorithm based on its key features in CAD engineering drawings. When user provides an example of a specific symbol, the input symbol is analyzed and its features are extracted automatically. Based on the relation representation, the constrained tree with key feature priority can be established for this type of symbol. By this means, the symbol library can be built and expanded automatically in order to handle variety engineering drawings. In the next stage of the recognition processes, we first locate the key feature nodes in drawings, and then find other elements around which satisfy the topology structure of constrained tree. If all the elements and constrains in the tree are found, the symbol object will be recognized. Because of the accurate position, unnecessary matching calculations are greatly reduced. Experimental results validate that our approach is effective. © 2011 IEEE.

关键词： Computer aided design

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PERSPECTIVES IN MECHANICS OF HETEROGENEOUS SOLIDS

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Acta Mechanica Solida Sinica 2011年第1期24卷 1-26页

作者： C.Q. Chen J.Z. Cui H.L. Duan X.Q. Feng L.H. He G.K. Hu M.J. Huang Y.Z. Huo B.H. Ji B. Liu X.H. Peng H.J. Shi Q.P. Sun J.X. Wang Y.S. Wang H.P. Zhao Y.P. Zhao Q.S. Zheng W.N. Zou Department of Engineering Mechanics AML Tsinghua University Beijing 100084 China Academy of Mathematics and Systems Sciences Chinese Academy of Sciences Beijing 100190 China State Key Laboratory for Turbulence and Complex System and Department of Mechanics and Aerospace Engineering College of Engineering Peking University Beijing 100871 China CAS Key Laboratory of Mechanical Behavior and Design of Materials University of Science and Technology of China Hefei Anhui 230026 China School of Aerospace Engineering Beijing Institute of Technology Beijing 100081 China Institute for Advanced Study Nanchang University Nanchang 330031 China Depariment of Mechanics and Engineering Sciences Fudan University 220 Handa Road Shanghai 200433 China Department of Mechanical Engineering Hong Kong University of Science and Technology Hong KongChina Department of Mechanical Engineering Hong Kong University of Science and Technology Hong Kong China Institute of Engineering Mechanics Beijing Jiaotong University Beijing 100044 China State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

The Micro- and Nano-mechanics Working Group of the Chinese Society of Theoretical and Applied Mechanics organized a forum to discuss the perspectives, trends, and directions in mechanics of heterogeneous materials in January 2010. The international journal, Acta Mechanica Solida Sinica, is de- voted to all fields of solid mechanics and relevant disciplines in science, technology, and engineering, with a balanced coverage on analytical, experimental, numerical and applied investigations. On the occasion of the 30TM anniversary of Acta Mechanica Solida Sinica, its editor-in-chief, Professor Q.S. Zheng invited some of the forum participants to review the state-of-the-art of mechanics of heterogeneous solids, with a particular emphasis on the recent research development results of Chinese scientists. Their reviews are organized into five research areas as reported in different sections of this paper. ~I firstly brings in fo- cus on micro- and nano-mechanics, with regards to several selective topics, including multiscale coupled models and computational methods, nanocrystal superlattices, surface effects, micromechanical damage mechanics, and microstructural evolution of metals and shape memory alloys. ~II shows discussions on multifield coupled mechanical phenomena, e.g., multi-fields actuations of liquid crystal polymer networks, mechanical behavior of materials under radiations, and micromechanics of heterogeneous materials. In ~III, we mainly address the multiscale mechanics of biological nanocomposites, biological adhesive surface mechanics, wetting and dewetting phenomena on microstructured solid surfaces. The phononic crystals and manipulation of elastic waves were elaborated in ~IV. Finally, we conclude with a series of perspectives on solid mechanics. This review will set a primary goal of future science research and engineering application on solid mechanics with the effort of social and economic development.

关键词： heterogeneous materials smart materials biological materials multiscale mechanics micro- and nano-mechanics damage and fracture constitutive relation elastic wave surface effects

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Fuzzy H∞ filtering for nonlinear singularly perturbed systems with time-varying delay

Fuzzy H∞ filtering for nonlinear singularly perturbed syste...

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2011 8th International Conference on Fuzzy systems and Knowledge Discovery, FSKD 2011, Jointly with the 2011 7th International Conference on Natural Computation, ICNC'11

作者： Li, Yaping Chen, Jinxiang Meng, Lixia He, Meiyun Beijing Information Technology College Beijing 100015 China State Key Laboratory of Hybrid Process Industry Automation System and Equipment Technology Automation Research and Design Institute of Metallurgical Industry 100071 China Department of Computer Science and Technology Tsinghua University Army Aviation College Beijing 100084 China Department of Mechanism Army Aviation College Beijing 100123 China

ISBN: (纸本)9781612841816

This paper investigates the problem of designing fuzzy H∞ filter for a class of nonlinear singularly perturbed systems (SPSs) with time-varying delay in states. The considered system is approximated by a Takagi-Sugeno (T-S) fuzzy model. By using linear matrix inequality (LMI) methods, we give a -independent sufficient condition for the existence of fuzzy H∞ filter such that, the resulting filtering error system is globally stable with guaranteed H∞ performance for sufficiently small . The gains of filter are obtained by solving a set of -independent LMIs, and therefore the ill-conditioned problem caused by can be easily avoid. The proposed method can be applied to both standard and nonstandard nonlinear SPSs. A numerical example is provided to illustrate the effectiveness of the developed method. © 2011 IEEE.

关键词： Perturbation techniques

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A linear algorithm for pseudo recognition in 3D reconstruction

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Computer-Aided design and Applications 2011年第6期8卷 827-839页

作者： Li, Qi Zhang, Hui School of Software Tsinghua University China Department of Computer Science and Technology Tsinghua University China Key Laboratory for Information System Security Ministry of Education China Tsinghua National Laboratory for Information Science and Technology China

Pseudo recognition is essential to reconstruct correct 3D models from engineering drawings. This paper proposes a novel linear algorithm to recognize pseudo elements based on the existence of non-manifold edges. First, mini face loops are defined to construct correct face loops and avoid overlapped loops, which previous loop construction methods would always result in when pseudo elements exist. Then, suspect faces whose all boundary edges are non-manifold edges, are defined to reduce the searching space of the algorithm for pseudo recognition, thus the algorithm can achieve linear time complexity. The algorithm is applicable for wireframe models including planes and basic conicoid surfaces. Experimental results are provided to demonstrate the algorithm. © 2011 CAD Solutions.

关键词： Three dimensional computer graphics

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Converting sectional views to three orthographic views to reconstruct 3D models

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Computer-Aided design and Applications 2011年第4期8卷 571-582页

作者： Ding, Fengqing Zhang, Hui Wen, Yamei School of Software Tsinghua University China Tsinghua National Laboratory for Information Science and Technology China Department of Computer Science and Technology Tsinghua University China Key Laboratory for Information System Security Ministry of Education

Compared with the CSG-based approach, the Brep-based approach has several advantages to construct 3D models from 2D engineering drawings, such as the structure is simpler and the domain of objects that can be handled is wider. However, this approach cannot handle sectional views directly. In this paper, a new method of converting sectional views to three orthographic views is presented. Firstly, the views which have the same projection direction are merged into one view. If the number of views is two, then a new view will be added according to the coordinate relations. Secondly, elements which have been omitted in sectional views are recovered according to the matching information of the existing edges. Finally, the existing Brepbased approach is used to reconstruct the 3D models. The algorithm can handle full sections, broken-out sections, offset sections as well as two orthographic views. The algorithm has been validated by experiments. © 2011 CAD Solutions, LLC.

关键词： Three dimensional computer graphics

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船用反应堆冷却剂泵连续调速研究

船用反应堆冷却剂泵连续调速研究

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第八届(2012)北京核学会核应用技术学术交流会

作者： LI Feng-yu 李凤宇 LU Gu-bing 陆古兵 CHEN Zhi 陈智 College of Naval Architecture&Power Naval University of Engineering Wuhan 430033 China 海军工程大学船舶与动力学院湖北武汉 430033 Science and Technology on Reactor System Design Technology LaboratoryNuclear Power Institute of China Chendu 610041 China 中国核动力研究设计院核反应堆系统设计技术重点实验室四川成都 610041

采用船用核动力装置模拟程序，对反应堆冷却剂泵转速连续调节研究进行仿真试验研究。在相同的40％满功率工况下，进行冷却剂泵转速阶跃变化与连续变化两种试验。对比了反应堆进出口温度、反应堆功率、反应堆反应性、冷却剂流量、蒸发器... 详细信息

采用船用核动力装置模拟程序，对反应堆冷却剂泵转速连续调节研究进行仿真试验研究。在相同的40％满功率工况下，进行冷却剂泵转速阶跃变化与连续变化两种试验。对比了反应堆进出口温度、反应堆功率、反应堆反应性、冷却剂流量、蒸发器蒸汽压力等参数的变化情况，对开展船用反应堆冷却剂泵连续调速设计具有重要的指导意义。

关键词：船用反应堆冷却剂泵转速调节仿真分析

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Real-Time Volume Caustics with Image-Based Photon Tracing

Real-Time Volume Caustics with Image-Based Photon Tracing

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IEEE International Conference on Computer-Aided design and Computer Graphics

作者： Yuxiang Wang Bin Wang Li Chen Key Laboratory for Information System Security Ministry of Education of China China Department of Computer Science and Technology Tsinghua University China Tsinghua National Laboratory for Information Science and Technology China

Rendering of volume caustics in participating media is often expensive, even with different acceleration approaches. Basic volume photon tracing is used to render such effects, but rather slow due to its massive quantity of photons to be traced. In this paper we present an image-based volume photon tracing method for rendering volume caustics at real-time frame rates. Motivated by multi-image based photon tracing, our technique uses multiple depth maps to accelerate the intersection test procedure, achieving a plausible and fast rendering of volume caustics. Each photon dynamically selects the depth map layer for intersection test, and the test converges to an approximate solution using image space methods in a few recursions. This allows us to compute photon distribution in participating media while avoiding massive computation on accurate intersection tests with scene geometry. We demonstrate that our technique, combined with photon splatting techniques, is able to render volume caustics caused by multiple refractions.

关键词： Photonics Rendering (computer graphics) Estimation Media Graphics processing unit Geometry Equations

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Effects of Proplet on Propeller Efficiency

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AIP Conference Proceedings 2011年第1期1376卷 165-168页

作者： J. H. Xu W. P. Song X. D. Yang National Key Laboratory of Science and Technology on Aerodynamic Design and Research School of Aeronautics Northwestern Polytechnical University Xi’an 710072 China

Many studies have proved the validation of winglets on improving aerodynamic efficiency. Similar to winglet, a suitable proplet can improve the efficiency of a propeller. The effect of proplet on propeller performance is investigated in this paper. With a cell‐centered finite‐volume scheme, Reynolds‐Averaged Navier‐Stokes (RANS) equations are solved on a chimera grid system to simulate the flow around propeller to obtain the aerodynamic performance. A propeller designed for high altitude at 20 km with a diameter of 6.8 m is used as a baseline propeller. The effect of chord length and incidence angle of proplet tip on 8the efficiency of the propeller are also considered. The simulation results demonstrate that a proper proplet leads to weaker blade tip vortex, which is helpful to improve the efficiency of the propeller.

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