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30 October 2014, Volume 35 Issue 5 Previous Issue    Next Issue

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An Analysis of Pure Space Adjacent Domain and its Dyeing Zhang Shiqing, Zhang Hao 2014, 35(5): 655-662.  Abstract ( 85 )   PDF (3002KB) ( 240 )   In the consubstantial N-dimensional pure spaces, the mapping relations in the pairwise adjacent domains can be built through the one-to-one projective transformation. Through the simulated experiment of the adjacent domain in computers as well as the strict proof, it is found and proved that, in the N-dimensional pure spaces, the maxima of pairwise adjacent domains in the N-1 (N minus 1) dimension is N+1 (N plus 1). In the configuration diagram of each N-1 dimension, there are at most N+1 kinds of dyeing. The building of the visible three-dimensional spherical models for "the Solid Geometry" can provide a visible "Standard Cosmic Projection Model" for the modern science. Related Articles | Metrics

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Review on Identifying Faces of Polyhedron Wireframe Models Li Xue, Gao Mantun, Zhao Jun 2014, 35(5): 663-668.  Abstract ( 153 )   PDF (254KB) ( 240 )   Wire-frame model usually appears as intermediate model in 3D reconstruction. However, the ambiguity and oversimplified information existing in this kind of model significantly restrict its practical application. It tends to be transformed into surface model and solid model. This paper mainly focuses on surface construction of 3D reconstruction, and the key points during this process are discussed. According to the source object of 3D reconstruction, this paper summarizes surface construction for wire-frame from three aspects: wire-frame transforming directly into surface model, reconstructing 3D model from a single drawing or image by wire-frame, and reconstructing 3D model from multiple projection. And on this basis, it points out the problems to be solved and the development direction for future researches. Related Articles | Metrics

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Animation of Brittle Fracture Using the Subdivided Particles Chen Feibin, Xie Buying, Ran Xiuyuan 2014, 35(5): 669-675.  Abstract ( 84 )   PDF (3330KB) ( 179 )   To simulate the brittle fracture when the solid is influenced by the external force, a method on modeling brittle fracture is proposed. Firstly the tetrahedral mesh of the solid model is bound to a series of particles. Then the smoothed particle hydrodynamics (SPH) is used to solve the equation of linear elasticity, and a subdivided scheme is adopted to generate the fracture surface. Finally, the rendering of some scene of the brittle fracture is achieved, including brick falling, brick-wall collapsing. This method can be applied for simulating the brittle fracture of solids. Related Articles | Metrics

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Transfer Function Design for Volume Rendering of Finite Element Data in 4-dimension Field Tang Yi, Huang Zhigang, Guo Zhongning 2014, 35(5): 676-681.  Abstract ( 94 )   PDF (883KB) ( 195 )   Conventional transfer function for volume rendering of finite element data is defined in 3-dimension field, while there are some 4-dimension data. In order to render them, a transfer function model in 4-dimension field is put forward. The model combines the characteristic of finite element data that the maximal data is more significant and the capability for filtering spatial data of volume rendering. It extends the forth dimension to construct time-series volume rendering and multiple volume rendering, so it enhances the flexibility of display for finite element data. Related Articles | Metrics

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Analytical Characteristics of Intersection Curve between a Cylinder and a Cone with Two Obliquely Intersected Axes and Graphical Method of Locating Special Points Liu Min, Lin Xi, Feng Juan 2014, 35(5): 682-689.  Abstract ( 77 )   PDF (515KB) ( 186 )   In general situations, there will be two spatial intersection curves generated when a cylinder and a cone are intersected with each other. This paper analyzes the various cases of the intersection curves and their special point locations when the axes of the cylinder and the cone are obliquely or perpendicularly intersected. If the intersecting curves are separated as two branches on the left and right, the distribution equation of the innermost points on the two intersection curves is obtained through theoretical analysis. The paper also analyzes the exact geometric conditions for classifying the four forms of the intersection curves and their corresponding cylinder radius distributions. The auxiliary sphere radius corresponding to the inner most point is also obtained. Finally, a graphical method of locating all the special points on the intersection curve is proposed in the paper. Related Articles | Metrics

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A Genetic Algorithm for Packing Problems Based on Bee Evolutionary Selection Operator Wang Jinmin, Zhu Liping, Zhen Shigang 2014, 35(5): 690-696.  Abstract ( 113 )   Three dimensional rectangular packing is a NP-hard problem, which is often solved by heuristic algorithms. In this paper the sequencing rules is determined by the volume of packing items, the positioning rules are determined by attractor function with the geometry feasible region of packing items in packing space. Then the parameters in the attractor function are optimized by bee evolution genetic algorithm (BEGA), the new packing genetic algorithm is formed. Finally, different benchmarks are carried out, and the paper proves the validity of the algorithm by comparing with the traditional packing genetic algorithm (SPGA) which chooses the standard proportional selection as its operator, etc. Related Articles | Metrics

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Theoretical Error Analysis and Optimal Solution for Eight-Center Arcs Ellipse Fitting Wang Guoshun, Tang Libo 2014, 35(5): 697-703.  Abstract ( 228 )   PDF (309KB) ( 263 )   Spherical tools are generally used in the field of numerical control (NC) machining. Arc fitting method has therefore been applied to machining of non-circular curved surfaces. The machining error is determined by the fitting accuracy, and arc fitting ellipse has infinite solutions. Since there is no accurate error calculation algorithm currently for fitting ellipse with eight-center arcs, accuracy of such fitting ellipse is uncertain. To resolve the issue, this research puts forward a concept of arithmetic fitting arc based on the theory of graphics. The definite solution interval of eight-center arcs for fitting ellipse has been identified. A transcendental equation has been derived for normal error of the eight-center arcs for fitting ellipse, and it is solved using dichotomy method. The process has been programmed in Visual LISP language in AutoCAD to solve for the minimum error band of the eight-center arcs for fitting ellipse in terms of normal error, so as to optimize the solution of eight-center arcs for the fitting ellipse. The paper thus provides a criterion for judging whether eight-center arcs can fit the ellipse for given form tolerances. Related Articles | Metrics

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A Method of Calculating the Hausdorff Distance betwwen Parametric Curves Lin Yi, Xue Siqi, Guo Tingting 2014, 35(5): 704-708.  Abstract ( 90 )   PDF (351KB) ( 406 )   In view of the general continuous parametric curves, a fast method of calculating the Hausdorff distance between curves is proposed in this paper. Because a curve can be indicated by its approximate polyline, many softwares use the approximate polyline to replace the original curve when drawing curves. This paper proves that we can convert calculating the Hausdorff distance between curves into the Hausdorff distance between polylines, and further into the distance between a point and a segment under any given error range. In order to improve the computational efficiency, it also supplement a pruning strategy and incremental algorithm. This method advantages in fast speed and high degree of approximation, and basically solves the problem of calculating the Hausdorff distance between parametric curves. Related Articles | Metrics

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One Effective Method of Identifying Feature Edges of Triangular Meshes Zhang Wei, Jin Tao 2014, 35(5): 709-714.  Abstract ( 87 )   PDF (1573KB) ( 251 )   Feature edges identification for triangular meshes is widely used in digital geometry processing and computer aided manufacturing (CAM) of dies. The shortcomings and corresponding origin of the existing algorithms about feature edges detection are pointed out in the paper. Furthermore, a new robust algorithm that identifies feature edges of triangular meshes is presented. The proposed algorithm is based on the identification of feature vertices of the mesh, and it can identify the edges with small dihedral angles which are often ignored by the existing algorithms. The proposed algorithm can improve the accuracy of identifying mesh edges with C1 discontinuities. This conclusion is supported by lots of examples in the paper． Related Articles | Metrics

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Stationary Internal Toroidal Gear Tooth Surface Modeling Based on B-spline Surface Interpolation Error Control Hong Mei, Yao Ligang 2014, 35(5): 715-722.  Abstract ( 122 )   PDF (1217KB) ( 219 )   A method of stationary internal toroidal gear tooth surface modeling based on B-spline surface is put forward in allusion to the difficulty of ensuring numerical control machining accuracy of stationary internal toroidal gear tooth surface. The interpolation curved surface is constructed by B-spline surface based on the theoretic tooth surface of stationary internal toroidal gear and then errors of theoretic tooth surface and interpolation curved surface are calculated. According to error distribution characteristics a set of data points can be obtained by error analysis and mesh refinement. The helical tooth surface model of stationary internal toroidal gear that meets accuracy requirement is obtained by interpolation reconstruction. In the end the validity of the modeling is verified by numerical control machining. This method provides a theoretical basis of acquiring high-accuracy stationary internal toroidal gear model. Related Articles | Metrics

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Web Service Workflow Customization Based on Pattern Shi Yinxue, Sun Ruizhi, Yuan Gang 2014, 35(5): 723-728.  Abstract ( 84 )   PDF (376KB) ( 177 )   For the complexity of business and the uncertainty of user’s requirement, a user-oriented dynamic service workflow building and instantiation method is proposed. Firstly, Service Process Pattern constructed as knowledge description of service workflow. It abstracts and specifies the business domain knowledge and the associated service processes. Based on the service process pattern, a multi-granularity service organization model is built by multi-layer goal-pattern matching to realize the business logic customization. Then, Quality of Service analyzing is made to select the proper concrete service in order to realize the service instance customization. Finally, this method is illustrated by an emergency treatment example. Related Articles | Metrics

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A Unit-quaternion-based Attitude Matching Algorithm Applied for iGPS Measurement Xu Bihan, Sun Fulong, Zhao Gang, Xing Hongwen 2014, 35(5): 729-735.  Abstract ( 87 )   PDF (359KB) ( 180 )   During digitalized joining procedure of large-scale parts, the iGPS is more and more used as measuring equipment for 3D coordinates. Based on the features of iGPS-measured-data, a unit-quaternion-based attitude matching algorithm is proposed. Compared to other existing attitude matching methods, this algorithm is simpler and more concise in calculation, and thus more effective in programming. Correspondent verification tests and error calculation indicate the accuracy of this algorithm for large rotation angles. Related Articles | Metrics

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Research on Variable Structure Parametric Design Method Based on AFV Technology Liu Guang, Mi Caiying 2014, 35(5): 736-740.  Abstract ( 82 )   PDF (450KB) ( 205 )   The traditional parametric method is difficult to adapt to variable structure design, presented a new parametric method in varied structure designing which named as AFV (Abstract-Fuse-Verification) technology. First, the component are abstracted into different parts, forming template library; then each part can be designed separately and any combination of parts is supported, improving the ability to adapt to the design of variable structures; the dimension of each part are verified finally in accordance with the relevant standards, avoiding illegal topological variation. In addition, AFV technology support the plug-in switching CAD platforms. The railway vehicle axle plug-in based on UG platform being developed using AFV technology, shows the feasibility of this tech. Related Articles | Metrics

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An Image Inpainting Algorithm Combined of CDD Model and Criminisi Algorithm Jiang Ping, Zhang Jin 2014, 35(5): 741-746.  Abstract ( 339 )   PDF (878KB) ( 229 )   Aiming at images with a lot of missing information and scratches, this paper puts forward a new restoration algorithm by combining the advantages of CDD model and Criminisi algorithm. Specifically, this algorithm first adopts the equalized operation of detail-oriented and self-adaptive histogram to expand the dynamic range of the images, and then utilizes morphology operators to separate the scratch regions and large areas in the images that need to be restored. Subsequently, CDD model is applied to restore the scratches and then the improved priority Criminisi algorithm is used to implement subsequent restoration. Finally, the restored images corresponding to the pixel of missing areas are filled into the regions of images need restoration. As the experimental results indicate, the improved algorithm has overcome the possible deviation continuation problems in current algorithm and can make the restored images more consistent with people’s visual effect. Related Articles | Metrics

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An Image Classification Method Based on V-moments Song Ruixia, Wang Yena, Sun Honglei, Wang Xiaochun, Qi Dongxu 2014, 35(5): 747-754.  Abstract ( 77 )   PDF (960KB) ( 201 )   The V-system is a complete orthogonal function system which is composed of both continuous function and functions with discontinuities. In this paper, we propose a new kind of V-moment functions based on the V-system, and apply them on image classification. Due to the discontinuity of the basis functions of the V-system, the V-moment functions have distinct advantages in describing the shapes with a plurality of closed boundaries. When they are applied on feature extraction for complex shapes, the extracted features are fairly accurate, thus effective image classification technique can be obtained using the V-moment functions. Experiment of image classification is conducted on several benchmark databases. The results show that the proposed method has higher accuracy than Zernike moments, invariant moments and geometric center moments, and it is not sensitive to noise. Especially, the proposed method presents obvious advantage when it is applied to classify complex shapes with several closed boundaries. Related Articles | Metrics

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An Image Segmentation Algorithm Based on Random Weight Particle Swarm Optimization and K-means Clustering Li Haiyang, Wen Yongge, He Hongzhou, Li Bolin 2014, 35(5): 755-761.  Abstract ( 171 )   PDF (949KB) ( 287 )   K-means clustering is widely used in image segmentation due to its simplicity and rapidity. However, it is easy to fall into local optimum, leading to poor image segmentation results. In order to overcome this disadvantage of K-means, this article proposes a mixed image segmentation algorithm based on random weight particle swarm optimization (RWPSO) and K-means clustering. In the early stages of the algorithm running, it can avoid falling into local optimal using the global search capability of RWPSO. In the later stages of the algorithm running, it can achieve fast convergence using the local search capability of the K-means clustering. Experimental results show that RWPSOK algorithm can effectively overcome the weak global search capability drawback of the K-means clustering. It can significantly improve the image segmentation results. Compared with traditional particle swarm K-means clustering algorithm (PSOK), RWPSOK algorithm has better segmentation results and higher efficiency. Related Articles | Metrics

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Visual Perception Based Rate Control Algorithm for H.264 Tian Bo, Yang Yimin, Cai Shuting 2014, 35(5): 762-767.  Abstract ( 88 )   PDF (667KB) ( 290 )   Due to that the conventional rate control algorithm for the latest video coding standard H.264 does not take into account the human visual perception and many result in video quality fluctuation, a visual perception based rate control algorithm (VP-RCA) for H.264 is proposed in this paper. First, bit allocation to frame is related to the Just Noticeable Distortion of frame and the rate control is performed by adaptive rate-distortion optimal. Second, the structural similarity index as the quality metric for rate-distortion modeling and the optimum bit allocation is performed in basic unit (BU) layer. And the value of quantization parameter (QP) is computed by exploring quadratic rate–quantization (R-Q) model. Experimental results show that the proposed rate control algorithm can reduces the bit-rate error by up to 0.2% comparisons with the typical rate control algorithms. Related Articles | Metrics

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The Study of Cloud Classification and Detection in Remote Sensing Image Zhou Xuejun, Yang Xiaofei, Yao Xingzhong 2014, 35(5): 768-773.  Abstract ( 127 )   PDF (2737KB) ( 306 )   Cloud shelter in remote sensing image may cause low date utilization rate, so the research of automatic and efficient cloud classification and detection method is increasingly important. This article proposes a high performance and high accuracy algorithm for the cloud classification and cloud edge detection based on gray character. This method finds out the mean and variance of gray value to classify cloud into three categories by dividing the image, then uses edge detection methods to remark the influence area of thick cloud. Primary testing results of 100 water remote sensing images have showed that this algorithm is valid and can satisfy the engineering requirement: the precise classification rate is 97%, the false rate is lower than 4% and the missed rate is lower than 2%. Related Articles | Metrics

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Method of License Plate Location Based on Mathematical Morphology and Color Characteristics Lian Ning, Xu Yanlei 2014, 35(5): 774-779.  Abstract ( 119 )   PDF (1087KB) ( 270 )   In order to solve the problem that the situation of single license plate localization algorithm in complex background is not ideal. A license plate location algorithm based on mathematical morphology and color characteristics is proposed. Firstly, the new method uses Ostu algorithm to select an optimal threshold, and according to the threshold carries on binary processing, then by using a new method of mathematical morphology for image edge detection. Finally combined mathematical morphology with color characteristic to locate license plate. Experiments show that this new method with higher accuracy and fewer restrictions on background is superior to traditional or a single method and can be widely used. Related Articles | Metrics

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Human Body 6 Degree of Freedom Motion Parameters BTViewer Wireless Testing System Design and Development Li Xiangchen, Li Lei, Zhang Moli, Wei Chuanmin, Zhang Jianwen 2014, 35(5): 780-786.  Abstract ( 102 )   PDF (1020KB) ( 245 )   In order to solve the test joint movement parameters of the human body in three-dimensional space, this paper puts forward a kind of independent design BTViewer six degrees of freedom motion parameters testing system of the human body. Based on the inertial sensor tracking technology, the working process of the overall design of the system platform, implement the algorithms at the same time. In order to reduce error and drift phenomenon, this experiment adopts the integrated three-axis accelerometer, the module LSM303DLH three-axis magnetometer and dynamic triaxial gyro samples data, transmitted to the computer via a wireless device, at the same time, the efficient of the collected data preprocessing, and complementary to the original data parsed into actual data after filtering, six degrees of freedom motion parameters accurately by the human body. Finally, using Qt integration of OpenGL to curve and 3D visualization display module. The design of the experiment show that the system has reached the expected requirement, 6 degree of freedom motion parameters can well track the human body. Related Articles | Metrics

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Research on Practice-leading Modes of Engineering Graphics Teaching for Mechanical Engineering Undergraduates Li Fuping, Yang Wentong, Wang Jianhua 2014, 35(5): 787-790.  Abstract ( 98 )   PDF (221KB) ( 223 )   From the point of view of practical training, according to the requirements of the "excellence engineers training plan", metalworking training courses, and "the reduction gear box" drawing project, this paper proposes an improved teaching method which takes task as driving force, and the students as the main body of the teaching method in the engineering graphics practice teaching process. This method combines the knowledge and practice of engineering graphics, and puts this practice in whole university teaching. It is helpful to cultivate the engineering consciousness and innovation ability of the students. Related Articles | Metrics

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Exploration of Enhancing Students′ Ability of Drawing Engineering Graphics and Engineering Concepts in Engineering Graphics Teaching Li Yutong, Wang Yuxin 2014, 35(5): 791-797.  Abstract ( 119 )   PDF (584KB) ( 257 )   Based on author′s accumulated experiences in the enterprise, exploration for enhancing students′ ability of drawing engineering graphics and engineering concepts in engineering graphics teaching has been made. Through pieces of engineering knowledge and experience about engineering design, and use of every bit teaching time, the corresponding engineering knowledge for rational engineering drawing has been inserted in the corresponding sections of the teaching course in the form of expanding students′ knowledge and skill. And then in the assembly drawing design of practice teaching course, it is encouraged that students apply the learning knowledge of engineering practice to the structure design and the engineering drawing expression of parts. Consequently, the students′ consciousness considering engineering background of products while carrying out the design is cultivated gradually through the process of engineering drawings and expressions. This kind of consciousness will be helpful for students to draw out engineering graphics in according with the requirements of engineering practices. Related Articles | Metrics

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The Selection of Software and Teaching Design for Course of CAD in Mechanical Drawing Tang Yongyong, Feng Jian, Chen Guomin, Du Zhenhua, Chen Ming 2014, 35(5): 798-803.  Abstract ( 101 )   PDF (372KB) ( 307 )   To solve the inconsistency between short periods and excessive teaching contents, an integration teaching method of simplifying teaching contents and emphasizing practical operation synchronously is proposed. The functions and characteristics of domestic and overseas 2D drawing softwares are studied synthetically. On the premise of satisfying the configuration request of software and hardware, the teaching software ought to be characteristic of wide application, easy adaptation and friendly operation interface so on. In addition, the view that teaching software should embody the advanced idea of design thinking separating from expression format. The teaching practice shows that the CAD teaching method taking operation ability as goal can conform to the requirements of periods and abilities. And the knowledge field of students can be spread. Related Articles | Metrics

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Finite Element Fast Modeling of Clinching Joints Based on HyperMesh Secondary Development Lu Shanbin, Lv Jie, Chen Wei, Feng Zhaoxuan, Qi Guiyue, Ye Hui 2014, 35(5): 804-808.  Abstract ( 192 )   PDF (1119KB) ( 513 )   At present, the constraint element SPR2 is applied to establish a simplified finite element model of clinching joints for its simple way for modeling and accurate simulation. However, HyperMesh 12.0 version can not support SPR2 modeling, which leads to the low efficiency of vehicle modeling. Therefore the Tcl/Tk and the built-in function of HyperWorks are used to develop finite element fast modeling for the vehicle clinching joint of SPR2. A certain car riveting modeling is taken as an example to verify the availability of the module. The module can automatically identify the connected plates according to the nodes selected, which greatly improves the modeling efficiency, avoids the software updates and saves the cost, and it provides a reference method for other new joints fast modeling. Related Articles | Metrics

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A Study of Processing Technology of the Prints in Chinese Woodblock New Year Prints Lei Hongyuan 2014, 35(5): 809-814.  Abstract ( 103 )   PDF (4685KB) ( 189 )   Aimed at the digital protection of Chinese woodblock new year prints, this paper, using the woodblock new year prints with chromatographic print of Zhuxian town as examples of processing, extracts the line prints and color prints from the new year prints with the technology of image processing. The procedure of processing is divided into 4 parts, i.e. pre-processing, line print extracting, color print extracting and after-processing. First, we should figure out the greyscale with the RGB of pixel and CMY color components ratio and transform most different colors of the new year prints into white so as to remove the colors; then after using the threshold processing, morphological image processing and line smoothing we can obtain the black line prints of the new year prints. We gain the color prints by K-means clustering method. The results of these processing can demonstrate the original appearance of new year prints and the processing procedure proposed in this paper is of great value to the digital protection of Chinese woodblock new year prints. Related Articles | Metrics