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28 April 2016, Volume 37 Issue 2 Previous Issue    Next Issue

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Point-Cloud 3D Object Reconstruction by Using Adaptive Weighting Function Lin Xiao, Wang Yanling, Zhu Hengliang, Hu Ganle, Ma Lizhuang, Li Luqun 2016, 37(2): 143-148.  DOI: 10.11996/JG.j.2095-302X.2016020143 Abstract ( 228 )   PDF (1093KB) ( 402 )   3D object reconstruction based on point clouds is an important field in computer graphics which have been used in computer animation, medical image processing and so on. Many good algorithms have been developed to solve this problem such as Levenberg-Marquart algorithm based on least squares and M-Estimator based on maximum likelihood estimation. But all of these algorithms are sensitive to noise and the data number of too lager or too little. And the result of these algorithms would have a larger error, which can influence the effect of reconstruction. In order to solve these problems, we propose a new algorithm which is based on Levenberg-Marquart algorithm and M-Estimator. Our algorithm takes advantage of high convergence of Levenberg-Marquart algorithm and noise proof of M-Estimator, so it can solve two problems mentioned above. And we improved the weighting function of M-Estimator which replaces the constant value with the flexible and adaptive value. This way makes our algorithm to behave very well in large number of points and high level of noise. We apply our algorithm on ball and cylinder and compare with the latest research results. From the experimental data we can see that our algorithm behaves much well than the others. Related Articles | Metrics

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Quartic Hermite Interpolation Spline Determined by Approximating the Derivative of Cubic B-Spline Curve Guo Xiao, Han Xuli, Huang Lin 2016, 37(2): 149-154.  DOI: 10.11996/JG.j.2095-302X.2016020149 Abstract ( 93 )   PDF (630KB) ( 351 )   A method is developed to construct adjustable quartic Hermite interpolating spline curves. The extra degree of freedom can be used to adjust the quartic curve to a reasonable shape. The interpolation based on the approximation of derivatives is discussed to make quartic Hermite spline with similar shape feature of cubic B-spline. The degree freedom is determined by minimizing the proximity, which is defined by the squared difference of the derivatives of the curves. The shape of the proposed quartic spline can be adjusted to satisfy the shape-preserving requirement by changing the values of degree of freedom. Four numerical examples are presented to compare the proposed quartic Hermite spline with the standard cubic Hermite spline. Related Articles | Metrics

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G2 Hermite Interpolation by Pythagorean Hodograph of Degree Six Wang Hui, Zhu Chungang, Li Caiyun 2016, 37(2): 155-165.  DOI: 10.11996/JG.j.2095-302X.2016020155 Abstract ( 118 )   PDF (1207KB) ( 238 )   By the advantages of computing arcs and representing offsets, study of phythagorean hodograph curves is one of the hot topics in recent years. In this paper, G2 Hermite interpolation by sextic PH curves is studied. Sextic PH curves can be classified into two types and the interpolation problem can be resolved to get the control points with some free parameter in complex representation. With the analysis of arc-length, bending energy and absolute rotation number, the better interpolation curves are selected. Moreover, the sextic PH G2 Hermite interpolation is applied to approximate the 90° and 67° arcs. The best approximating curves can solve C1 Hermite interpolation by the PH sextics. And the best curves’ performance is better than the quintic G2 Hermite interpolation curves when approximating the 90° arc, and is almost same as the latter’s best curve when approximating the 67° arc. Related Articles | Metrics

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An Improved Randomized Incremental Algorithm for Generating Minimum#br# Enclosing Ball of Discrete Point Set Li Shilin, Li Hongjun 2016, 37(2): 166-171.  DOI: 10.11996/JG.j.2095-302X.2016020166 Abstract ( 100 )   PDF (988KB) ( 289 )   The minimum enclosing ball (MEB) of discrete point set in the 3D space has been widely used in many fields, such as collision detection, computational geometry, pattern recognition and so on. In order to better understand and construct MEB, its character is analyzed firstly. After analyzing the classical randomized incremental algorithm, we propose two strategies to improve time efficiency. One strategy is to construct a bigger initial enclosing ball and another strategy is to decrease the number of updating MEB. Based on the second strategy, a new algorithm called random point group-recalculation farthest point is proposed. Multi-group experimental results, whose data are both randomly generated by computer and realistic 3D model sampling, show that the random point group-recalculation farthest point algorithm can effectively improve the time efficiency compared with the classical algorithms. Related Articles | Metrics

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Surface Blending Based on Generalized B-Spline Subdivision Shen Yongchao, Fang Meie 2016, 37(2): 172-177.  DOI: 10.11996/JG.j.2095-302X.2016020172 Abstract ( 52 )   PDF (714KB) ( 215 )   This article uses generalized B-spline subdivision scheme of arbitrary order with a tension parameter to blend several surfaces, which is suitable to blending both meshes with arbitrary sizes and generalized B-spline control meshes. The shape of blending surfaces can be adjusted globally through changing the order or the tension parameter. Shape parameters are also set during computing central points and valley points. So users can adjust them to locally change the shape of blending section. In addition, we apply the proposed blending method to blend quadrics. The blending results are apparently better than those of existing methods. Related Articles | Metrics

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B-Spline Curve and Surface Fitting Using Differential Evolution Algorithm He Bingpeng, Feng Renzhong, Yu Shengjiao 2016, 37(2): 178-183.  DOI: 10.11996/JG.j.2095-302X.2016020178 Abstract ( 106 )   PDF (894KB) ( 406 )   To use B-spline curve and surface to fit data with an underlying function having discontinuous points and/or cusps, the fitting results obtained by least squares method are often bad in the vicinity of discontinuous points and cusps because of the fixed B-spline knots. In this paper, we propose a method for solving data fitting problem with cubic B-spline curve and surface by using differential evolution algorithm. Our method can set B-spline knots adaptively, so as to optimize the number and location of knots simultaneously and produce quasi-multiple knot in the vicinity of discontinuous points and cusps. With this, we can fit data with an underlying function having discontinuous points and/or cusps with high precision. Related Articles | Metrics

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Contact Analysis of Link-Fitting with High-Strength Material Based on Abaqus Li Junhui, Xu Guanghui, Chang Linjing, Song Tiechuang, Wan Shaoting, Xu Aibin 2016, 37(2): 184-188.  DOI: 10.11996/JG.j.2095-302X.2016020184 Abstract ( 73 )   PDF (789KB) ( 272 )   Contact problem is a highly nonlinear behavior. Different contact types and control factors have an important effect on the results of the simulation model. In this study, the ability of resisting to deformation of link-fitting with high-strength material was simulated by FEA, using commercial software Abaqus. Different contact types between U-shackle and its connecting part were set up. Upon comparison and analyzation of the results with different contact types, it is clear that the contact type of U-shackle is suitable for the given service condition. Through nonlinear static analysis, the stress and deformation distributions of link-fitting were obtained. According to the results, modification suggestions were put forward, which provides a scientific guidance for the design of the link-fitting. Related Articles | Metrics

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Error Analysis of Ellipse Based on Newton Iteration Method Zhou Yahui 2016, 37(2): 189-192.  DOI: 10.11996/JG.j.2095-302X.2016020189 Abstract ( 66 )   PDF (579KB) ( 209 )   The four-arcs method uses four arcs joining together similarly into an ellipse. Due to its symmetry, we take a quater graphics as the researching object and solve the equations by using dichotomy. Then we get the splicing point coordinates of the two pieces of circular arc. Then do error analysis with the actual ellipse in the two pieces of circular arc, and list the mathematical equations of the two pieces of circular arc and the ellipse polar. Then solve the actual maximum error value of the ellipse and the two pieces of circular arc with Newton iterative method. After that, figure out the approximate and actual ellipse areas, so as to work out the area error values. With the mathematical model, the calculator software is developed. It is concluded that the error of the approximated ellipse is solved through comparing the analysis list of calculating results. Related Articles | Metrics

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Top-Down Parametric Assembly Modeling Method of Missile Body Structure He Qian, Xi Ping 2016, 37(2): 193-198.  DOI: 10.11996/JG.j.2095-302X.2016020193 Abstract ( 111 )   PDF (5464KB) ( 258 )   In order to improve the design quality and efficiency of the modeling process of missile body structure, modeling process of missile body structure was studied. The structure of missile body top-down parameters assembly ligand modeling method was presented. Based on UG platform, missile body structure modeling system was developed, in which the missile body structure modeling, model rapid change and assembly parameters driving and management as the whole were realized. Used the typical structure of missile body structure as an example, the feasibility and effectiveness of the method were verified. Related Articles | Metrics

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A Fast and Lossy Compression Algorithm for Point-Cloud Models Based on#br# Data Type Conversion Lv Shuai, Da Feipeng, Huang Yuan 2016, 37(2): 199-205.  DOI: 10.11996/JG.j.2095-302X.2016020199 Abstract ( 97 )   PDF (780KB) ( 291 )   In order to solve computer storage and transmission problem due to massive 3D point cloud, a fast and lossy compression algorithm for point-cloud models based on data type conversion is proposed. Firstly, a data type conversion rule-FtoI rule is designed. According to the FtoI rule, float-point type point cloud is converted to integer type point cloud, then the integer type point-based surface is split into many sized surface patches, the points of every patches construct a minimum spanning tree, which is encoded in breadth first order. Besides we encode the difference between father node and son node according to the minimum spanning tree, the difference is split into two parts, one is sign, another is absolute value, which is encoded by arithmetic coding. Experiments show that this compression algorithm has a nice compression speed and compression ratio without losing the quality of point-cloud model. Related Articles | Metrics

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An Efficient Mesh Editing for Component-Based 3D Garment Generation Liu Li, Fu Xiaodong, Wang Ruomei, Luo Xiaonan 2016, 37(2): 206-213.  DOI: 10.11996/JG.j.2095-302X.2016020206 Abstract ( 84 )   PDF (1518KB) ( 257 )   Directly modeling 3D garments from scratch is often difficult and professional. To simplify the complicated manipulation for 3D garment modeling for untrained users, this paper proposes an efficient editing method for component-based 3D garment generation. The key idea in this work is to model the new models in given garments using segmentation and merging of mesh editing techniques. We decompose the given garments into meaningful components w.r.t. clothing prototypes. Then, the merging of new garments with components is performed interactively. Finally, we obtain the best merging results for each garment model by applying mean-value coordinates, with advantageous in terms of speed, ease of implementation. Experimental results show that our algorithm can effectively generate new garment shapes with small memory footprint. Related Articles | Metrics

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Face Recognition Methods Fusing Gabor Feature and#br# Projective Dictionary Pair Learning Fu Yuxian, Peng Liangyu, Peng Hui 2016, 37(2): 214-217.  DOI: 10.11996/JG.j.2095-302X.2016020214 Abstract ( 92 )   PDF (1326KB) ( 528 )   In order to obtain better face features and enhance the recognition rate of algorithm, a face recognition algorithm based on Gabor feature and projective dictionary pair learing named G-DPL is proposed in this paper. The local feature of face image are extracted by Gabor wavelet and PCA and LDA scheme is used to reduce the feature dimension. Projective dictionary pair learning algorithm and dimensionality reduced Gabor feature are fused to identify the classification. The recognition rate of G-DPL algorithm can reach 99.00% under ORL database. Feature dimensionality is 39. G-DPL can reach 96.14% on AR database. Feature dimensionality is 99. The proposed G-DPL algorithm can obtain higher recognition rate while taking up less space, which has certain reference value for practical application. Related Articles | Metrics

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Realization of Cartoon Effects Based on Non-Photorealistic Rendering Qian Wenhua, Xu Dan, Pu Yuanyuan, Xu Jin, He Lei, Liao Dongwei 2016, 37(2): 218-223.  DOI: 10.11996/JG.j.2095-302X.2016020218 Abstract ( 101 )   PDF (849KB) ( 275 )   An effective method for non-photorealistic rendering for computer generated images with cartoon artistic works from 2D images is provided in this paper. The proposed methods is inspired by bilateral filter and DOG filter. The color space of source image is transferred from RGB to LAB, and bilateral filter can be used to reduce contrast in low contrast regions, and increase contrast in high contrast regions. Further, the color can be abstracted by soft color quantization to create cartoon-like effects. In addition, DOG filter and threshold are applied to obtain continuous and clear edge image, and this edge information can be merged to the cartoon-like effects finally. Experimental results show that our proposed method is simple and effective. Related Articles | Metrics

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Research on Aerial Target Recognition and Tracking Based on Gray and#br# Textural Features Li Hongan, Du Zhuoming, Li Zhanli, Kang Baosheng 2016, 37(2): 224-229.  DOI: 10.11996/JG.j.2095-302X.2016020224 Abstract ( 99 )   PDF (855KB) ( 261 )   In recent years, the technology of video surveillance, widely used in the field of spaceflight, has become an important technical means in spaceflight safety and management. This paper gives a method to firstly detects change region of moving targets through background subtraction and temporal difference. Detect moving targets through binarization and morphological filtering, thus moving targets are identified combining with gray and textural features. Then Mean-Shift method to recognize and track moving targets is adopted. Lastly an experiment video example to monitor is given. The result shows that the feature of target has achieved good effect in the process of recognition. For the tracking of spaceflight moving target the method has better robustness, and is feasible. Related Articles | Metrics

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An Novel Image Resizing Method Based on Important Area Maintain Zou Panpan, Lu Ping, Zhu Hengliang, Dong Zhenjiang, Jia Xia, Lin Xiao, Ma Lizhuang 2016, 37(2): 230-236.  DOI: 10.11996/JG.j.2095-302X.2016020230 Abstract ( 64 )   PDF (1161KB) ( 253 )   Scaling and seam carving are commonly used algorithm in image resizing, but scaling is not suitable for the case that the resize ratio is not uniformity, seam carving will also has a bad effect on important area in some cases. In this paper we proposed a novel algorithm which is based on important region maintain. Firstly, we make a corner detection based on difference of Gaussian, then Graham-scan algorithm is applied to do an important region detection, after that we will add different weights between important region and unimportant region. The experimental result shows our method is better than other image resizing algorithms in maintaining the important area. Related Articles | Metrics

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Sharpness Assessment for Remote Sensing Image Based on Maximum Gradient Liu Yamei 2016, 37(2): 237-242.  DOI: 10.11996/JG.j.2095-302X.2016020237 Abstract ( 111 )   PDF (1545KB) ( 856 )   The image acquired by the remote sensing camera will appear to be a certain fuzzy phenomenon after transmitted it to the ground. It will get high quality image after restoration, and it is necessary to use some methods to assess the quality of recovery image. This paper proposes a sharpness assessment for remote sensing image, which picks up gradient from images, calculates the number of the pixels on the region of maximum gradient and the data is used as sharpness parameter. We get the upgrade rate after comparing the sharpness parameters between the fuzzy image and the recovered image. We demonstrate the validity of this new method through some experiments. The experimental results show that the method can accurately assess the sharpness upgrade rate of the restored image, and get better results in the inhibiting effect of weak ringing ripples and the anti-noise performance when the signal noise ratio over 22 dB. Related Articles | Metrics

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Real-Time Simulation of Accident Effects in Virtual Flight Scene Wang Xinxiang, Zhao Gang, Xiao Wenlei 2016, 37(2): 243-248.  DOI: 10.11996/JG.j.2095-302X.2016020243 Abstract ( 73 )   PDF (726KB) ( 248 )   In order to enhance the sense of reality in accident scenes of flight simulation, a method based on particle system and combined with dynamical model is adopted for rendering special effects, including fire, smoke, explosion, and so on. The traditional point particles are replaced by the quadrilateral ones. The texture mapping method is presented for the particle system. Each quadrilateral particle is mapped with the texture of real effect, and the textures are blended with the background according to a given alpha value. As a result, the special effects have an improved sense of reality and a good real-time performance. The method of particles’ collision detection is applied to simulate the smoke spreading and collision with the aircraft’s cabin. Finally, a virtual system of flight accident simulation is implemented, which is able to simulate the fire and smoke phenomenon happened inside the cabin and the explosion happened on the engine with a strong sense of reality. Related Articles | Metrics

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Research on Representation and Management of#br# IFC-Based Building Components Shi Pingwang, Lin Liangfan, Deng Xueyuan 2016, 37(2): 249-256.  DOI: 10.11996/JG.j.2095-302X.2016020249 Abstract ( 100 )   PDF (751KB) ( 400 )   Industry foundation classes (IFC) is the standard for BIM data storage, which defines all kinds classes and objects for the whole life cycle of construction projects. In this paper, through the example of a building element, IFC Beam, the representation of IFC-based building components described in detail. In addition, the management of IFC-based building component, including element creation, modification and deletion, is studied in detail. The research achievement can be utilized for the construction of IFC-based component library. Related Articles | Metrics

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Research on Data Conversion Method for Eccentric#br# Member of Structural Analysis Model Zou Shuai, Lai Huahui, Deng Xueyuan 2016, 37(2): 257-264.  DOI: 10.11996/JG.j.2095-302X.2016020257 Abstract ( 56 )   PDF (957KB) ( 346 )   The XML-based structure general format had been built in the early stage to carry out basic model data conversion among several different structural models such as SGF, SAP2000, ETABS and IFC. However the conversion of complex eccentrically components was not achieved in most existing platforms which caused negative influence to the results of structural analysis. This research analyzed the eccentric data structures from different structure software applications, and summarized the data expression of eccentric structural members. Moreover, the mapping relationship between SGF and eccentric data was established, and then an eccentric structure analytical model conversion algorithm was proposed to implement the transformation of eccentric components of structure models. Finally the algorithm was validated through a case of model conversion for a typical framework with eccentric members. Related Articles | Metrics

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A Practical Teaching Method Improving Students’ Autonomous Learning Ability#br# for Intersecting Lines Learning Wang Yongquan, Wang Shenghuai 2016, 37(2): 265-268.  DOI: 10.11996/JG.j.2095-302X.2016020265 Abstract ( 82 )   PDF (540KB) ( 265 )   The learning contents of intersecting lines are the important and difficult parts in the course of the graphics. The theoretical teaching method for this learning contents was the main and the single teaching model for many years. For improving the current teaching situation, a practical teaching method improving students’ autonomous learning ability for intersecting lines learning is presented in this paper. On the basis of using the self-developed instrument for drawing intersecting lines, practical teaching program, plans and learning evaluation system are made for this teaching method. The preliminary implementation of this practical teaching method in our school shows that the students’ learning enthusiasm and interest in learning this difficult content are inspired greatly. Because of the choice of the exercises and the practical operation by the students themselves, the students can understand the contents more easily and have more impressive for them. Related Articles | Metrics

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Finite Element Simulation Analysis of 900 t Girder Hoisting Machine#br# Based on ANSYS Chen Shitong, Cui Chenguang, Li Yuan, Li Yiqiang 2016, 37(2): 269-274.  DOI: 10.11996/JG.j.2095-302X.2016020269 Abstract ( 105 )   PDF (841KB) ( 359 )   To ensure the operation safety of 900 t girder hoisting machine, the ANSYS is used to set up the whole 3D model for the girder hoisting machine, the finite element analysis for the girder hoisting machine is analyzed base on the working condition. The structure composition, functional characteristics and working condition of girder hoisting machine are introduced, then the modeling principle and method of finite element model are proposed for girder hoisting machine. Through the element simulation analysis, the equivalent stress and structural deformation for different working conditions are presented, and the finite element results and the test results are discussed in details, the result demonstrates that the simulation analysis results are consistent with the test results. Then the cause for deviation of the finite element results and the test results are analyzed. The research results is helpful for the design and manufacture of the girder hoisting machine. Related Articles | Metrics

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Solving Spatial Arbitrary Force System with Projection Plane#br# Transforming Method Yang Menghong, Lin Meimei, Wang Dawei, Xu Jiaping 2016, 37(2): 275-279.  DOI: 10.11996/JG.j.2095-302X.2016020275 Abstract ( 65 )   PDF (2418KB) ( 192 )   The projection plane transforming method can change the spatial geometric element’s position relative to the plane of projection in the descriptive geometry and the new projection is more conductive to solving problems. In the statics, the vector force can show in a straight line, the equilibrium problem of spatial arbitrary force system can turn into the diagram and legend among the line, this paper tries to combine the strengthen of projection plane transforming method into solving of the equilibrium problem of spatial arbitrary force system in a direct way. Using CAD as a drawing tool can ensure the mapping precision and speed, which is a practical and effective method to solve the spatial arbitrary force system. Related Articles | Metrics

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Rectangular Optimal Layout Based on Best Sub Segments Jiang Yongliang, Zhou Jun 2016, 37(2): 280-284.  DOI: 10.11996/JG.j.2095-302X.2016020280 Abstract ( 39 )   PDF (425KB) ( 287 )   To effectively solve the long board rectangular optimal layout problems which is often encountered in the actual production of enterprises, rectangular optimal layout algorithms were studied and a rectangular optimal layout algorithm based on the best sub segments was proposed, which effectively solve long board rectangular optimal layout problems in actual production. Firstly based on dynamic programming algorithm all sub optimal layout modes were solved which is less than the shear blade length. Secondly with the best sub segments as layout parts, these segments were optimized on the long board and the rectangular optimal layout problems were converted to knapsack problems completely. Finally the integer programming algorithm based on branch and bound technique was used to solve the long board rectangular optimal layout problems. Enterprise’s practical application showed that the algorithm in solving the long board rectangular optimization problems is better than other algorithms. Related Articles | Metrics