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A Layout Optimization Method of Composite Wing Structures Based on Carrying Efficiency Criterion

Chinese Journal of Aeronautics 2011年第4期24卷 425-431页

作者： ZHAO Qun DING Yunliang JIN Haibo Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

A two-level layout optimization strategy is proposed in this paper for large-scale composite wing structures. design requirements are adjusted at the system level according to structural deformation, while the layout is optimized at the subsystem level to satisfy the constraints from system level. The approaching degrees of various failure critical loads in wing panels are employed to gauge the structure’s carrying efficiency. By optimizing the efficiency as an objective, the continuity of the problem could be guaranteed. Stiffened wing panels are modeled by the equivalent orthotropic plates, and the global buckling load is predicted by energy method. The nonlinear effect of stringers’ support elasticity on skin local buckle resistance is investigated and approximated by neural network （NN） surrogate model. These failure predictions are based on analytical solutions, which could effectively save calculation resources. Finally, the integral optimization of a large-scale wing structure is completed as an example. The result fulfills design requirements and shows the feasibility of this method.

关键词： composite wing structure layout optimization carrying efficiency buckling equivalent stiffness energy method surrogate model

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Implicit surface reconstruction based on adaptive clustering

Implicit surface reconstruction based on adaptive clustering

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

作者： Zheng, Chao Zhang, Hui 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 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. © 2011 IEEE.

关键词： Surface reconstruction

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An optimal color mapping strategy based on energy minimization for time-varying data

An optimal color mapping strategy based on energy minimizati...

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

作者： Peng, Yi Dong, Jie Chen, Li Chu, Haiyang 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

Color mapping plays a critical role in visualization of time-varying data and also sets a challenge for researchers due to the consistency of mapping and great changes in time-varying data. In order to solve this problem and generate feature-prominent animation, we present a two phase optimization technique using bilateral filtering and global energy functions. In the first phase, for each time step, we use a weighted mapping function which combines linear mapping and feature histogram. In the second phase, an optimization function taking global color mapping and minimum color difference into consideration is designed. So users can clearly distinguish between data in variable time steps and easily understand the corresponding relationships between different structures. The experiments' results show that our method can achieve high quality visualization for both static and time-varying data. © 2011 IEEE.

关键词： Visualization

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Automatic generation of canonical views for CAD models

Automatic generation of canonical views for CAD models

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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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