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29 April 2011, Volume 32 Issue 2 Previous Issue    Next Issue

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New Algorithm of Generating Regular Polygon and Circle ZHANG Bo 2011, 32(2): 1-4.  Abstract ( 139 )   PDF (505KB) ( 307 )   Recursion formula is generated and proved in connection with the calculation of vertex coordinates of a regular polygon. Based on the new formula, the algorithm for generating regular polygon and circle is put forward, whose error analysis is given. The calculation of every vertex of a regular polygon calls for multiplication and addition twice respectively. The new method is better than that of polygon approximation. The algorithm is of the characteristics of simple construction, fast execution speed and high accuracy. Related Articles | Metrics

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An Optimal Algorithm for Calculating the Width of Convex Polygons CHEN Hai, WANG Xin-min, JIAO Yu-song, LI Yan 2011, 32(2): 5-9.  Abstract ( 165 )   PDF (485KB) ( 267 )   An optimal linear time algorithm is proposed to calculate the width of convex polygons. It is proved that the width of a convex polygon only be found between the span of vertex-edge pairs. In this way, the range of calculation narrows down. Then an algorithm using distance comparison is investigated to reduce the calculation of the span. Based on the basic algorithm of vertex-edge pairs and the distance comparison, the optimal algorithm for calculating the width is proposed. The simulation results show that the proposed algorithm greatly improves the efficiency of caculating the width of convex polygons, and reduces the time complexity to O(n). Related Articles | Metrics

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A New Algorithm of Polygons’ Boolean Operations Using Interior Angle ZHU Er-xi, HE Yuan-jun 2011, 32(2): 10-19.  Abstract ( 132 )   PDF (620KB) ( 485 )   The current algorithms of the polygons’ boolean operations can give correct results rapidly enough in general cases. But there are errors when it comes to queer conditions. This paper proposes a method to analyze queer conditions using concept of graphic interior angle, and gives a new overall algorithm of queer’s treatment on the basis of the original intersection-traversal algorithms’ framework. Compared with other algorithms of polygons’ boolean operations, the algorithm in this paper is more simple and effective for analysis of queer conditions. Related Articles | Metrics

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Design and Realization of Parameterized Pile Cap Automatic Mapping System CHEN Liang-tu, WANG Ting-ting, WU Yang-yang 2011, 32(2): 20-25.  Abstract ( 147 )   PDF (456KB) ( 186 )   In the Port Engineering, there are a large number of standardized components. Parameterization and programming of the drawing of all these standardized components can not only reduce the large amount of monotonous repetitive work, but also greatly enhance the efficiency and quality of engineering drawing. The powerful VBA embedded in AutoCAD has been used to develop an Automatic Mapping System with friendly user interface for Parameterized Pile Cap. The system integrates parametric design and drawing management, and thereby significantly improves the drawing quality and efficiency in the process of pile cap design. Related Articles | Metrics

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Three-dimensional Tunnel Modeling Method Based on Parametric Technology Lü Xi-kui, ZHOU Xiao-ping, ZHANG Xue-jun, ZHOU Liang 2011, 32(2): 26-30.  Abstract ( 148 )   PDF (637KB) ( 221 )   The traditional 3D tunnel modeling methods lack interactivity and diversity. The paper proposes a new method of three-dimensional tunnel modeling and landscape simulation based on parametric technology. The tests show that the method can be used to build the three-dimensional models of various landscape tunnels quickly and effectively, and express tunnel design and 3D scene intuitively. The method fully meets the requirement of quickness diversity and interactivity of three-dimensional tunnel modeling. Related Articles | Metrics

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Development of Parts Model for Cutting the Screw Thread System LI Jing, LEI Zheng-bao, ZHU Hai-wen 2011, 32(2): 31-36.  Abstract ( 126 )   PDF (471KB) ( 216 )   Through synthesizing the menu script, user interface dialog and API programs, the parts model of CST (Cutting the Screw Thread) is automatically created in UG NX, using Visual C++ to call the functions of UG/OPEN API. The instance shows that the developing module has good correlation and can change exactly as the user inputs different parameters. The function of creating CST parts model in UG is achieved. Related Articles | Metrics

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Structure Modeling and Finite Element Analysis of SWL 550 Cross Shaft Universal Coupling TONG Ji-bin, JIN Ping 2011, 32(2): 37-43.  Abstract ( 122 )   PDF (778KB) ( 238 )   Modern design technology is used to perform structural design and strength calculation of SWL550 type cross shaft universal coupling. The load boundary conditions of important parts are obtained by using of the mechanical analysis of cross shaft universal coupling. The models of important parts are built based on CATIA, CATIA finite element analysis module is applied to perform finite element analysis of the important parts. Von Mises stresses of the dangerous sections are basically coincident with theoretical calculated values. Replacing the traditional physical coupling experiments with digital models, it simplifies design process of shaft coupling to a large extent. Related Articles | Metrics

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3D Model Reconstruction and Error Analysis of Turbo Blade Mold XI Ping, HU Bi-fu 2011, 32(2): 44-48.  Abstract ( 146 )   PDF (818KB) ( 293 )   An error inspection method based on 3D Model Reconstruction is proposed for estimating the manufacturing error of turbo blade mold. Two 3D models (design model and measurement model) are constructed by design data and measurement data respectively. The design model can provide theoretical evidence for error inspection. The quantitative manufacturing error will be obtained through these two models. The outcomes of this research can be utilized in analysis of digital inspection and error analysis. Related Articles | Metrics

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3D Object Reconstruction from Three Orthographic Views ZHENG Peng-fei, LIN Da-jun, LIU Xiao-yang, WU Zhi-ting 2011, 32(2): 49-54.  Abstract ( 197 )   PDF (413KB) ( 316 )   Technique of 3D reconstruction based on three orthographic views refers to constructing a corresponding 3D object model by use of the geometric and topological information in the existing 2D engineering drawings. In this paper，a 3D object reconstruction algorithm from three orthographic views of engineering drawings is proposed and implemented, which is based on the information from AutoCAD orthographic views and DXF file format documents. According to the rules of projection, corresponding primitives are matched and recognized, 3D reconstruction is automatically finished by computer. After 2D orthographic views are moved, revolved and extruded, the 3D object model can be reconstructed by making appropriate boolean operations at last. Related Articles | Metrics

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The Application of Unique Face Model Technology in the City Digital Models ZHOU Ji, YOU Xiang 2011, 32(2): 55-59.  Abstract ( 104 )   PDF (550KB) ( 207 )   In this paper, a kind of Unique Face Model technology is set up according to different object models and Independent Mesh Model object in order to achieve the target optimization and solve the problems in vast digital model structures. This method provides solution to the establishment of large capacity model with low-level software and hardware, and working efficiency is greatly improved. The virtual objects and real images are seamlessly integrated. Related Articles | Metrics

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CAD Modeling Based on Single Gray-scale Image LIANG Fa-zhou, MA Yin-ping, LIANG Fa-yun 2011, 32(2): 60-65.  Abstract ( 125 )   PDF (438KB) ( 150 )   A surface reconstruction algorithm in CAD is used on the basis of three-dimensional shape from shading. First, use the physical surface imaging model to create a reflection map equation based on Lambertian reflectance model; second, use the finite difference method to scatter approximation of the surface gradient to obtain the function equation of the physical surface; then find its solution by using of Netwon-Raphson iterative method to obtain the function value of the reconstructed surface height. the reconstruction results in line with product model data transferring standards and then the exchange in CAD system is realized. The image restoration through three-dimensional surface shape validates the feasibility of the algorithm and the reconstruction system. Related Articles | Metrics

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Surface Reconstruction from High-density Point Cloud Based on Deformed Meshes CHEN Hui-qun, LI Jing-yan 2011, 32(2): 64-67.  Abstract ( 155 )   PDF (414KB) ( 233 )   To improve the efficiency of surface reconstruction of scattered points, a method of surface reconstruction from high-density 3D scatter point cloud is proposed. This method first sets a uniform mesh and deforms each cell of the mesh by fitting the vertex of each cell to the nearest of the input points, then constructs triangles according to the pattern of the vertexes’ state in each cell. It works fast with little memory. A case study is done to demonstrate the feasibility of this method. Related Articles | Metrics

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Surface Reconstruction Based on Points Cloud Data from CMM WU Xue-mei, WEN Jia, YU Guang-bin, LI Gui-xian, SHAN De-bin 2011, 32(2): 68-72.  Abstract ( 161 )   PDF (472KB) ( 431 )   Based on CMM data, the some critical techniques has been researched: boundary fitting, characteristic identifying, surface patch reconstructing, smooth matching considering the feature of mouse data. By employing cubic B-spline curves to fit boundary curves, differential coefficient geometry method to do surface characteristic identifying and division, and pulling and molding methods to accomplish surface patch reconstruction, the mouse model is finally fulfilled through surface patch intersecting, cutting out and transition. Related Articles | Metrics

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Extension of Uniform Cubic B-Spline Curves with Multiple Shape Parameters XIA Cheng-lin, WU Hong-yi, ZHENG Xing-guo, PENG Kai-jun 2011, 32(2): 73-79.  Abstract ( 161 )   PDF (484KB) ( 262 )   Two classes of blending functions with multiple shape parameters are presented in this paper. They are the extension of uniform cubic B-spline basic functions. Based on the given blending functions, the piecewise polynomial curves with shape parameters are defined. These curves inherit the most properties of uniform cubic B-spline curves with GC1 or GC2 continuity. The position and the length of tangent vector at the end points of curve segments can be independently controlled by changing the values of the shape parameters. These curves can be adjusted totally or locally and interpolated by any given control points. Related Articles | Metrics

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Tangent Detection and Calculation for Parametric Surfaces Represented by Discrete Surfels ZENG Yang-yan, ZHENG Wen-ting, PENG Qun-sheng 2011, 32(2): 80-86.  Abstract ( 154 )   PDF (525KB) ( 221 )   A novel tangent detection and calculation algorithm is presented for parametric surfaces based on discrete surfels. The two surfaces are initially uniformly sampled into surfels. Surfels of each surface are then organized into a space octree with surfels’ normal bounding cones being built at each octree node. By checking the consistency of the normal bounding cones together with the enclosing box test, the algorithm can detect the potential tangent area between the two surfaces robustly. The candidate surfels are resampled at high resolution to ensure the accuracy of the result and then tangent operation is carried out at last. Experiments show that the algorithm is effective and easy to implement by analyzing possible tangent area to find tangent points within the error range. Related Articles | Metrics

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An Otsu Dual-threshold Value Method Based on Parallel Genetic Algorithm for Medical Image Segmentation XU Liang-feng, LIN Hui, LUO Xun, WU Dong-sheng, LI Guo-li, XU Yuan-ying, JING Jia 2011, 32(2): 88-92.  Abstract ( 115 )   PDF (497KB) ( 272 )   Medical Image Segmentation is a hot topic in the community of medical images analysis. The traditional genetic algorithm is sometimes inaccurate and instable when it is used in searching the best solutions of some functions. To solve the problem, an Otsu Dual-threshold Value Method based on parallel genetic algorithm for Medical Image Segmentation is proposed. In the algorithm, evolution is performed among different subgroups in parallel. The avoidance of premature convergence of single-species evolutionary process improves the convergence efficiency of the algorithm. The thresholds searching results for 100 times show that the algorithm presented in this paper can not only find better solutions, but also be more stable and accurate than the traditional genetic algorithm. Its convergence is improved more quickly than that of the single-species genetic algorithm. Related Articles | Metrics

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Color Image Decomposition Based on the SVD of Quaternion Matrix XING Yan, TAN Jie-qing 2011, 32(2): 93-101.  Abstract ( 190 )   PDF (1687KB) ( 354 )   The singular value decomposition of a quaternion matrix (QSVD) is discussed. The singular values of a quaternion matrix are still real and positive, but the two unitary matrices are quaternion matrices with quaternion entries. An efficient algorithm to compute QSVD by the SVD of its equivalent real matrix is presented. Finally, QSVD is applied to color image decomposition, and the experimental results on the images Fruits and Baboon are shown. By using of QSVD, many image processing methods based on SVD can be extended for color image without separating it into three channel images. Related Articles | Metrics

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Planar Contour Primitive Recognition Based on Curvature Improved by HOUGH Transform WU Ji-gang, BIN Hong-zan 2011, 32(2): 102-106.  Abstract ( 288 )   PDF (435KB) ( 278 )   According to the inspection accuracy and inspection speed, a planar contour primitive recognition method based on curvature improved by HOUGH transform is proposed. A contour point classification algorithm based on neighborhood values is developed, and a curvature threshold method is selected to filter the contour points, and a projection height method is selected to distinguish the property of the primitive and classify the contour points, and the straight line primitive and arc primitive segmentation and merging algorithms are proposed and constructed respectively by HOUGH transform. The dominant point detection accuracy and detection speed contrast experiments and dominant point detection ability test experiment of the proposed method are carried out respectively. The experimental results indicate that the proposed method can recognize primitives exactly, the inspection speed is fast and the universality is good. Related Articles | Metrics

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A Blind Image Watermark Algorithm Based on Improved Zerotree Wavelet WANG Jing-zhong, LI Dan 2011, 32(2): 107-110.  Abstract ( 119 )   PDF (403KB) ( 203 )   An adaptive watermark algorithm in wavelet domain is proposed and the hamming code is used to correct the wrong code. The whole process is based on integer wavelet transform, coding the significant coefficients which have un-scanned in intermediate frequency sub-band, and adaptively quantizing wavelet coefficients. The watermark is embedded in the perceptually important coefficients. The watermark can be detected without resorting to the original image. Experimental results show that the algorithm proposed has the characteristics of strong adaptability, fast implementation, better invisibility and strong robustness against attack such as JPEG compression, filter, noise addition and cropping. Related Articles | Metrics

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Development of the Visualization and Sharing System on Collaborative Simulation Information WANG Xu, TIAN Ling, WEN Ying-yi 2011, 32(2): 111-117.  Abstract ( 118 )   PDF (1000KB) ( 176 )   A feasible solution is proposed to implement the visualization of heterogeneous simulation information. The macro programming interface of Tecplot is employed to provide visualization service, which is web-based, uniform and exquisite, to heterogeneous simulation data generated by different software tools. The mechanism of data transmission in Internet is designed by means of Ajax (Asynchronous JavaScript and XML), which is asynchronous and real-time, to fulfill the demand of the complicated data interactivity. A client integrated AutoVue and VRML browser is implemented to provide sharing show of the other structured simulation information. J2EE and B/S architecture are used, and an actual visualization sample is presented, which shows the validity of the system. Related Articles | Metrics

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Construction of Engineering Drawing Meta-cognitive Training Model LIN Qing-fu 2011, 32(2): 118-121.  Abstract ( 121 )   PDF (386KB) ( 180 )   The essence of meta-cognitive training on students is training and developing meta-cognitive ability. Meta-cognitive training model is to learn the students’ reflections when they suffer from difficulties, to identify the problem in order to take the most appropriate learning process, to enable students to understand how to learn. Therefore, in drawing teaching, teachers must first teach students some general mapping ideas, train students to improve the efficiency and ability of solving problems using mapping mind, guide students to take the initiative to summarize different problem-solving strategies, improve students learning ability and learning quality. Related Articles | Metrics

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Development of Web Virtual Model Library of Engineering Drawing Based on X3D MIAO Jun, CHU Jun, ZHANG Gui-mei 2011, 32(2): 122-126.  Abstract ( 105 )   PDF (565KB) ( 212 )   Web virtual model library has a widespread use in the teaching of engineering drawing. Compared to VRML, X3D is a new generation of network programming language and has more mature standard. This paper introduces with emphasis the process and key technology of a web virtual model library developed by using X3D, and illustrates methods of building 3D model and making realization process virtual. Web virtual model library not only compensates the shortcoming of in-class teaching and study, but also is a good tool for distance learning. Related Articles | Metrics

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Nephogram Characterization of Boundary Face Method’s Numerical Results SONG Min, ZHANG Jian-ming, QIN Xian-yun 2011, 32(2): 127-131.  Abstract ( 123 )   PDF (541KB) ( 186 )   The newly developed boundary face method comes into the advantage of the conventional Boundary Element Method, and the boundary faces of the geometry are discretized by patches in parametric space. These constitute advantages over standard mesh-based methods in some special areas such as moving boundaries, large deformation simulation, high gradient problems etc. But they make post-processing of the numerical results an issue which needs additional effort. In this paper, on the basis of the corresponding color of the nodes’ numerical values of each background triangle with advancing front technique, a filling method for Nephogram characterization of boundary face method’s numerical results is presented and realized by means of OpenGL. It is demonstrated that the proposed approach is feasible and efficient. Related Articles | Metrics

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Study of the Computational Methods of Focus of Expansion ZHANG Zheng-wu 2011, 32(2): 132-137.  Abstract ( 79 )   PDF (556KB) ( 183 )   The computation of cross ratio by use of image coordinates will cause computational breakdown or deterioration of accuracy, and the N-vector formula for computing cross ratio is established if the points and lines on the image plane are represented in terms of N-vectors. The N-vector computational methods of a pure translation motion focus of expansion are constructed on the basis of the above study. The formula only needs the images of a space point at three different moments or its N-vector, N-rate and N-acceleration. The experimental result shows that this algorithm is more reliable. Related Articles | Metrics

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Adaptive Plotting for AutoCAD Drawings Using ObjectARX CHEN Zhi-yuan, WANG Li-ping 2011, 32(2): 138-144.  Abstract ( 148 )   PDF (717KB) ( 242 )   Based on studying the plotting mechanism in the AutoCAD paper space, and by using VC++6.0 and ObjectARX, a fast and flexible plotting method has been developed by consulting AutoCAD drawings, plotting media and operating process, which can intelligently create layout, create viewport and output drawings according to different plotting condition. In addition, working principle, workflow and key technology are described in detail and the given instances prove its strong adaptability and high efficiency. Related Articles | Metrics