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31 October 2016, Volume 37 Issue 5 Previous Issue    Next Issue

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Global Illumination Real-Time Rendering Based on BRDF and#br# GPU Parallel Computing Wang Fang1, Qin Leihua2 2016, 37(5): 583-591.  DOI: 10.11996/JG.j.2095-302X.2016050583 Abstract ( 140 )   PDF (2139KB) ( 382 )   While raytracing, the screen image pixel is decomposed into the combination of radiance and texture of the patches, created as scene objects intersect with the casting ray. The radiance of each patch is calculated at the linear combination of the bases of bi-directional reflectance distribution function (BRDF), and able to be accelerated by graphics processing unit (GPU) parallel rendering. This paper presents a global illumination rendering algorithm based on BRDF and GPU parallel computation. With GPU parallel acceleration, through improving the efficiency of rendering, the algorithm achieves global illumination real-time rendering of the scene including dynamic interactive material. The key research: object surface’s multiple reflection characteristic is represented by linear combination of the basis of BRDF, so transforming the nonlinear problem to a linear one, thus improve the rendering efficiency. With GPU parallel acceleration, the algorithm calculates the object surface’s radiation energy and texture mapping and their linear combination, further improving the efficiency of rendering to meet the requirement of real-time. Related Articles | Metrics

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Design and Implementation of Meteorological Symbol Library for GIS Visualization and Analysis Lu Mingyue1,3, Liu Bin1,3, Chen Min2,4, Wang Xuan1,3, Zheng Jianqin1,3, Mao Yuanxiang1,3 2016, 37(5): 592-597.  DOI: 10.11996/JG.j.2095-302X.2016050592 Abstract ( 87 )   PDF (601KB) ( 298 )   Geographic information system (GIS) can’t deal with meteorological data directly due to the shortage of necessary meteorological symbol library currently. Therefore, this article analyzes the characteristics of commonly used meteorological symbols and logically classifies the symbols into three types (symbol based on point, symbol based on line, symbol based on area) considering the professional criterion as well as the meteorological application. Then the corresponding spatial geometry models and symbol styles are also constructed to build the meteorological symbol library in the form of the “geometry+style”. All the meteorological symbols in the library are drawn successfully based on GDI+, and packaged as drawing library for GIS usage. The meteorological symbol library constructed in this paper provides support for the presentation and analysis of the meteorological information based on GIS. Related Articles | Metrics

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Registration of Planar Point Cloud and Vector Graphics Huang Fang, Ning Tao, Chen Zhitong, Shen Yunchao 2016, 37(5): 598-606.  DOI: 10.11996/JG.j.2095-302X.2016050598 Abstract ( 107 )   PDF (547KB) ( 289 )   In the optical measuring of planar parts, the registration of 2D point contour and planar vector contour is the key algorithm, the speed and precision of registration has a major impact on the speed and precision of measure result. In order to solve the problem of registration of 2D point cloud, a coarse registration algorithm based on shape feature function and a 2D iterated closest point (ICP) fine registration algorithm are researched. Through the angle-distance graph, geometry information of point contour and planar vector contour is translated to continuous function that is independent of coordinate system. The objective function of registration is calculated on account of nearest distance algorithm on planar point and curve, and analytic method of solving the objective function directly is given, which is different from traditional ICP algorithm. The efficiency of algorithm is improved significantly. Examples are exhibited to analysis the efficiency and reliability of the algorithm. Related Articles | Metrics

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An Efficient Surface Reconstruction Method for Lagrangian Particle Fluid Shao Xuqiang1, Liu Yan2, Wang Xinying1 2016, 37(5): 607-613.  DOI: 10.11996/JG.j.2095-302X.2016050607 Abstract ( 108 )   PDF (2082KB) ( 400 )   In order to simulate small-scale geometrical features of Lagrangian particle fluid surface, this paper presents an efficient octree-based adaptive fluid surface reconstruction approach. First, this approach implements the more accurate detection of fluid surface particles. Then, the approach adaptively decomposes the fluid particles’ AABB bounding boxes including fluid surface particles based on octree. Finally, the implicit distance field is only constructed in the leaf nodes including fluid surface particles. The memory consumption and computation complexity of fluid surface reconstruction depend on fluid surface not fluid volume, so our method is very suitable for large scale fluid scenes. Related Articles | Metrics

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Research on Optimization of Rotation Angle and Singular Area Handling in Five-Axis Post-Processing Yu Dan, Yan Guangrong, Fan Qingxiang, Ding Tao, Xu Xiangyu 2016, 37(5): 614-619.  DOI: 10.11996/JG.j.2095-302X.2016050614 Abstract ( 135 )   PDF (431KB) ( 256 )   Post-processing is the key of the transformation from CL-Data of CAM system to NC program. Since the improper selection of rotation angle will leads to collision between cutter tool and work piece and dramatic change of rotary axis in adjacent cutter-location as well as rotary angle changes rapidly and non-linear error exceeds allowable limits in singular area. This paper proposed a method which integrates optimization of rotation angle and singular handling in five-axis post-processing. A post-processor was developed with C++ program language based on the method, which inputs the CL-Data of CATIA NC manufacturing module and outputs the NC program. The validity of the method is verified through Vericut simulation. Related Articles | Metrics

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On Computation of Distance Extremum Points Based on Exact Surface Representation and Its Application in Tool Interferance Detection Tian Sukai, Ning Tao, Chen Zhitong 2016, 37(5): 620-625.  DOI: 10.11996/JG.j.2095-302X.2016050620 Abstract ( 61 )   PDF (769KB) ( 244 )   Aiming at the problem of solving distance extreme points on trimmed surfaces in collision detection of rigid bodies which are represented by exact surface, a method is presented to obtain the initial distance extreme points using the plane vector field, which can avoid the excessive subdivision of the surface. The differential geometry conditions of the distance extreme points are discussed, and iterative formulas for obtaining distance extreme points of the analytic surface/parametric surface and parametric surface/parametric surface are given in this paper. The efficiency and reliability of the algorithm are verified by an example. Related Articles | Metrics

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A Calculation Method of Aircraft Surface Waviness Based on the Method of Point Projection on Curved Surface Zhang Li, Wu Zhonglin 2016, 37(5): 626-631.  DOI: 10.11996/JG.j.2095-302X.2016050626 Abstract ( 83 )   PDF (1041KB) ( 231 )   To measure the waviness of aircraft surface accurately and efficiently, an improved algorithm for the projection of points on parameter-curved surface is proposed. The point projection on curved surfaces is calculated by adopting the approach of elliptical torus patch approximation. Firstly, by using this algorithm, points are extracted from the surface’s massive measuring points and the offset value between measuring points and their projection on the theoretical positions is calculated. Secondly, the local extremum is extracted at the peak and valley of waviness according to the variation trend of the offset value. Then its corresponding wavelength is calculated. Finally, the waviness is calculated based on its definition. Experiments show that this method is highly efficient, and generates accurate results. Related Articles | Metrics

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The Research of Automatic Dimensioning System for Profile Extrusion Dies Li Li, Guo Shunsheng, Huang Lang, Ding Kang, Zhang Hengbo 2016, 37(5): 632-638.  DOI: 10.11996/JG.j.2095-302X.2016050632 Abstract ( 105 )   PDF (1268KB) ( 213 )   The structure of extrusion die is relatively fixed, but it has a lot of redundant waste lines in plate engineering drawings, and the processing of dimensioning is not convenient. Taking extrusion die as the research object, the automatic dimensioning system of engineering drawing for profile extrusion die is developed on Unigraphics NX (UG) platform. The following aspects are studied: proposing the method of identifying redundant line of plates to ensure automatic elimination of the lines by deletion or transformation. Presenting the method of recognizing edges for hole positioning dimensioning and adopting the method of four quadrant incremental arrangement to realize automatic arrangement for positioning dimensions. Proposing the method of hole recognition and matching to achieve automatic dimensioning of the specification, tolerance and text. The application result shows the system greatly reduces the workload and improves the efficiency of drawing dimensioning. Related Articles | Metrics

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Research on Automatic Dimensioning of the Engineering Drawing of the Calibrators Based on UG Huang Lang, Guo Shunsheng, Tang Hongtao, Li Li, Wu Rong 2016, 37(5): 639-647.  DOI: 10.11996/JG.j.2095-302X.2016050639 Abstract ( 75 )   PDF (2033KB) ( 427 )   Aimed to the problem that the shapes of the calibrator are complex and irregular, there are many internal holes, the workload of the dimensioning and layouts are large, the structural characteristics of the model are analyzed, and based on the three-dimensional software UG NX (Unigraphics NX) platform, the automatic dimensioning system for the engineering drawing of the calibrators is developed. The requirements of the dimension are summarized, and the engineering drawing templates are created. Through feature extraction, the redundant edges of automatic engineering drawings of three-dimensional models are deleted automatically. Based on the extracted mark datum, the vacuum holes, water holes, locating key are dimensioned, and according to the positions, the dimensions are laid out reasonably. A case study presented to verify the practicability of the engineering drawing automatic dimensioning system. The research simplifies the design process and improves the design efficiency. Related Articles | Metrics

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An Automatic Narrow Face Error Detection Technique for Aircraft Structural CAD Model Zhou Min1, Zheng Guolei1, Chen Shulin2 2016, 37(5): 648-654.  DOI: 10.11996/JG.j.2095-302X.2016050648 Abstract ( 59 )   PDF (1812KB) ( 228 )   There are always narrow topological faces on the CAD model of aircraft structures, which is prone to lead a series of engineering operations to fail in the manufacturing process of part. To solve this problem, an automatic narrow face error detection technique for CAD model based on the analysis of parameter district boundaries is proposed. First, the common narrow faces of aircraft structural CAD model are depicted and classified. And, based on the geometrical characteristics and the engineering requirements, the narrow face error is defined. Second, the effective parameter district of each topological face on the CAD model is computed. Third, the narrow district is constructed according to reflex points. After that, the length and the width are calculated to judge if the topological face is a narrow face error. Finally, the algorithm flow of this technique is given and implemented. The experimental results are showed to prove that the presented method is both correct and effective. Related Articles | Metrics

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Parameterization Correlation Design and Rapid Adjustment of Unmanned Aerial Vehicle Structure Li Ru, Hu Bifu, Xi Ping, Jin Shihan 2016, 37(5): 655-660.  DOI: 10.11996/JG.j.2095-302X.2016050655 Abstract ( 68 )   PDF (1176KB) ( 315 )   Based on the characteristics of the composites unmanned aerial vehicle(UAV) structure, the whole design process is described in detail. According to the studying of CATIA parameterization correlation method and the top-down design with the core of “layout sketch”, parameterization assembly correlation design method of UAV structure is proposed. Model rapid adjustment will be realized on it. Finally the effectiveness of the modeling method is verified by an example of an UAV structure. Related Articles | Metrics

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An Algorithm for Circle Cutting Stock Problem Based on Trapezoid and Parallelogram Chen Yan1,2, Liu Yong1, Xie Qiqi1, Cui Yaodong1 2016, 37(5): 661-667.  DOI: 10.11996/JG.j.2095-302X.2016050661 Abstract ( 46 )   PDF (439KB) ( 214 )   A pattern of circular cutting in rectangle sheet is proposed by introducing trapezoidal stripes. Plate with two parallel dividing lines will be divided into three segments when the nesting, two segments of the same size right angle trapezoid and one parallelogram segment. Respectively recursive algorithm and dynamic programming algorithm are used to determine the optimal combination of stripes in trapezoidal section and parallelogram section, so as to determine the optimal pattern. Then combine with linear programming algorithm to solve the problem of the two-dimensional cutting pattern problem, making material utilization maximum. Finally, experiment results of a large number of randomly generated problems show the effectiveness of improving material utilization of the algorithm. Related Articles | Metrics

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Research on Simulation Method of Vehicle Pavement Roughness Excitation Xu Dongzhen1, Zhang Zufang1,2, Xia Gongchuan1 2016, 37(5): 668-674.  DOI: 10.11996/JG.j.2095-302X.2016050668 Abstract ( 68 )   PDF (709KB) ( 419 )   Analysis of road surface roughness on the three axle vehicle random excitation input, using white noise method and the transfer function method is used to derive the vehicle six rounds of road roughness input state equations are obtained. In Matlab/Simulink to build a two-dimensional pavement roughness mathematical model, and standard pavement roughness the comparison and validation, indicating the accuracy of the model to build. Through the vehicle state equation to build six rounds of pavement roughness mathematical model. The simulation results show that the with the axle of the power density of the two wheels of the spectrum differences, on the same side of the front and rear wheels of power density spectrum difference of smaller, more in line with the actual situation of multi vehicle bridge heavy truck and in order to further validate the simulation results, the correlation coefficient of the road roughness of the six round of the vehicle is analyzed, and the results are consistent with the above conclusions. Related Articles | Metrics

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Using Virtual Computer Analysis to Optimize the Forklift Vision Zhao Chuan, Yu Suihuai, Li Bingchao, Zhang Shuai 2016, 37(5): 675-680.  DOI: 10.11996/JG.j.2095-302X.2016050675 Abstract ( 118 )   PDF (1124KB) ( 238 )   Good vision is a important safety factors in operation forklift. This paper have studied on the visual field forklift truck. A virtual driving operation model for forklift truck was proposed by means of sight box-plot method and applying ergonomic simulation software-Jack based on the 5th percentile Chinese adults body size. And Identified the drawbacks of present forklift truck existing in its front view and rear view and while loading and unloading goods at a certain height. Then we proposed corresponding suggestions on how to improve this and optimize its design, such as install onboard visual system and optimize the roof of forklift. Furthermore, the results of optimisation was validated by means of a case study, demonstrating its capacity to reduce blind angle of sights, which is of some significance for forklift design. Related Articles | Metrics

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Research of Coating Design of Construction Machinery Based on Color Image Zhang Zongdeng1,2, Zhang Hongying2 2016, 37(5): 681-687.  DOI: 10.11996/JG.j.2095-302X.2016050681 Abstract ( 103 )   PDF (777KB) ( 261 )   Excess capacity is a major problem faced by the engineering equipment industry, which can be solve this problem by design. This article uses of the basic theory of color, color psychology, kansei engineering, market research, statistical analysis and other methods, to solve the problem of color matching and color matching on construction machinery, and getting three kinds of color matching scheme (numbered A4-4, B2-4, C2-4) and then, taking excavator as an example, the color scheme is verified, achieving the desired results. Hope to provide reference for the coating design of construction machinery products. Related Articles | Metrics

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Apple Identification and Calibration Based on the Texture Characteristics and HSI Space Li Dahua, Zhao Xiangfei, Xu Liang, Yu Bo 2016, 37(5): 688-693.  DOI: 10.11996/JG.j.2095-302X.2016050688 Abstract ( 107 )   PDF (6424KB) ( 409 )   This paper, after analyzing different image segmentation methods, presents an image segmentation algorithm based on color and texture features in order to enable an apple picking robot to separate targets from complex backgrounds. Texture features of grayscale images are analyzed to obtain ground launched cruise missile for feature extraction and to segment images by support vector machine. Besides, in combination with chromatic aberration in HSI color space, targets are effectively separated from their backgrounds. By comparison with the methods of color analysis and texture analysis, this algorithm provides higher rate of recognition and ever better result in separating fruits with similar colors to backgrounds. Related Articles | Metrics

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Image Recognition Algorithm of Convolutional Neural Networks Based on Matrix 2-Norm Pooling Yu Ping, Zhao Jisheng 2016, 37(5): 694-701.  DOI: 10.11996/JG.j.2095-302X.2016050694 Abstract ( 108 )   PDF (1103KB) ( 503 )   The pooling operation in convolutional neural networks can achieve the scale invariance of image transformations, and has better robustness to noise and clutter. In view of the problem that pooling operation ignores the energy information hidden in the image when it extracts local features for image recognition, according to the relationship between energy of the image and singular value of the matrix, and taking into account the image information of the energy mainly concentrates on the larger singular value, a pooling method based on matrix 2-norm was proposed. The former feature map of convolutional layer is divided into several non-overlapping sub blocks, and then singular value of the matrix is calculated. The maximum value is used as the statistical results of each pooling region. Various numerical experiments has been carried out based on Cohn-Kanade, Caltech-101, MNIST and CIFAR-10 database using different kinds of pooling method. Experimental results show that the proposed method is superior in both recognition rate and robustness compared with other methods. Related Articles | Metrics

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Study of the Computational Methods of Vanishing Points Zhang Zhengwu 2016, 37(5): 702-706.  DOI: 10.11996/JG.j.2095-302X.2016050702 Abstract ( 116 )   PDF (358KB) ( 313 )   The comprehensive and recognition of 3D scene by using vanishing points (lines) has been one of the most important research areas in computer vision fields. The conventional computational methods based on the image homogeneous coordinates will cause deterioration of accuracy when they become too large or too small, because the homogeneous coordinates of the same image points have different representations by the scaling factor. The computation methods by use of the characteristics of coordinates vector and harmonic range are proposed from the perspective of computational processes in this paper. The results of examples show that this algorithm is more utility and reliable than traditional algorithms. Related Articles | Metrics

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Research on the Reform of “Electrical Engineering Drawing” Course Based on Innovative Practice Ability Wang Xichu1, Zhang Shuhong1, Fan Hong2 2016, 37(5): 707-710.  DOI: 10.11996/JG.j.2095-302X.2016050707 Abstract ( 111 )   PDF (312KB) ( 251 )   Innovative talent training mode is the key of teaching reform, and “electrical engineering drawing” is an important professional basic course of electrical engineering specialty, and it has an inescapable responsibility for the cultivation of innovative talents. This article obtains from curriculum reform of “electrical engineering drawing”, the content of the curriculum teaching, teaching mode, assessment methods are in-depth researched and reformed，and the students ability of innovation and practice is improved, the effect is good. Related Articles | Metrics

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The Reform and Practice of Engineering Drawing Courses Syllabus Under the Background of Engineering Education Professional Certification Mu Haozhi1,2, Xue Lijun1,2, Niu Xinghua1,2 2016, 37(5): 711-717.  DOI: 10.11996/JG.j.2095-302X.2016050711 Abstract ( 118 )   PDF (269KB) ( 302 )   According to the standards of the mechanical engineering education professional certification, considering the requirements of Tianjin regional economic development and the specialty characteristics of the School of Mechanical Engineering of Tianjin of University of Technology, with the course of “engineering drawing” as an example, a reform of the teaching syllabus, which can construct the corresponding matrix of the index point of graduation requirements and the courses, fusing the index point with the teaching contents, is elaborated. This reform reflects the education guidance of “student-centred”, and provides some necessary references on promoting the certification of engineering education in colleges and universities, training engineering and technical personnel to adapt to the regional development and meet the needs of internationalization. Related Articles | Metrics

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Engineering Graphics Course Construction and Teaching Practice Based on “Online and Offline Hybridized Education Mode” Zhang Zongbo, Wang Min, Wu Baogui, Liu Guangdou 2016, 37(5): 718-725.  DOI: 10.11996/JG.j.2095-302X.2016050718 Abstract ( 112 )   PDF (803KB) ( 367 )   Online education represented by MOOC has shown great advantages and societal values in resent years. It will become the inexorable trend of future education. Course construction and teaching reformation of engineering graphics for online education is studied in this paper. The main work includes constructing and utilizing of online course resources, organizing teaching activities and coordinating of online and classroom teaching. Therefore, an new online and offline hybridized education mode formed with both advantages of online education and traditional education. Based on teaching practice, the main features, critical processes, feasibility and effectiveness of this education mode are studied. So it is a beneficial exploration and try for the hybridization of engineering graphics education and modern information technology. Related Articles | Metrics

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Arbitrary Section Display of Full-3D Gas-Assisted Injection Molding Numerical Simulation Results Ren Qinghai1, Geng Tie2 2016, 37(5): 726-730.  DOI: 10.11996/JG.j.2095-302X.2016050726 Abstract ( 58 )   PDF (620KB) ( 178 )   Arbitrary section display is an important technology of full-3D gas-assisted injection molding numerical simulation post-process. By studying the spacial position relation of the tetrahedral element and the cutting plane, a new method is presented that is based on the pure space geometrical analysis for obtaining the arbitrary section and high quality rendering color contour map on the section. That is by means of traversal to determine the “effective element”, intersection solution by class filter, and physical quantity interpolation, color mapping to obtain the physical quantity on the section, and then to realize the rendering and display of color contour map of data distribution on the arbitrary section with OpenGL technology. Verified by example, the method can accurately and clearly draw the gas-assisted injection molding numerical simulation results distribution on the arbitrary section. And it is helpful for people to understand and analyze the simulation results more effectively. Related Articles | Metrics

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Research on NC Lathe Turning Automatic Programming Graphic Input System Based on DXF Shaft Parts Feature Liu Xin 2016, 37(5): 731-739.  DOI: 10.11996/JG.j.2095-302X.2016050731 Abstract ( 78 )   PDF (836KB) ( 185 )   In computer aided numerical control (NC) lathe turning automatic programming system, fast and accurate parts graphic input is the primary link of realizing CNC automatic programming. Based on the feature of DXF shaft parts graphic information, through in-depth analysis of DXF file structure, data structure was set up based on the data of shaft parts (including geometry information and process information). Graphic element intersection algorithm was adopted to extract and put in the feature information of each figure, and users could click on the feature of graphic element on the screen and enter the corresponding process information, and then data processed will be stored in the database by using dynamic binding technology. Different feature of the graphic element will produce different types of table. It can input part graphics through the way of opening the database, and finally it outputs data structure required by the system. Results show that the developed application system can rapidly and accurately input DXF shaft parts graphics, and data structure generated meets the demands of calculating tool locus, which is able to provide technical supports for virtual NC machining simulation. Related Articles | Metrics