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30 April 2015, Volume 35 Issue 2 Previous Issue    Next Issue

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Projection Theory and Research of Ancient Chinese Graphics Liu Keming 2014, 35(2): 155-160.  Abstract ( 117 )   PDF (6310KB) ( 219 )   Demonstrating the approach to protract the figure of three-dimensional graphs with geometrical forms in two-dimensional planes, graphics is a basic technical discipline of examining protracting engineering drawings using the method of projection and addressing issues on space geometry as well as its theory and approach. Graphics is also a kind of semiotic system of writing. China boasts of rich tradition of graphics with amazing architectural drawings in Pre-Qin period, booming theories of graphics in Wei and Jin dynasties, refined protracted drawings in Song and Yuan dynasties, and graphics being regarded as important instruments in Ming and Qing dynasties when thorough apprehension were pursued in order to seek the practice of administration. It not only forms the basis for modern and contemporary graphics in China, but also shapes the future development of graphics. The projection theory of Chinese graphics not only provides information support for technical development, but also lays out theoretical foundation of rapid modernization of Chinese graphics. Related Articles | Metrics

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GSPM: A Graphics System for Pipeline Based on Management Information System Xiao Yang, Zheng Yueming, Liu Hongbin, Deng Maoyun 2014, 35(2): 161-166.  Abstract ( 71 )   PDF (530KB) ( 163 )   This paper describes the theory and method to develop a graphics system based on management information system (GSPM) through the application of the basic principles of software engineering and object-oriented programming methods and the application of the visualization and graphical data integration technology, and discusses the establishment of the framework and the design of the system and the main classes. The system uses the Windows interface and its operation is simple and convenient. Drawings can be done just by simply clicking on the corresponding buttons on the toolbar or menu bar to select the correct elements on the preparation of a variety. The system is designed to interface with the database, integrate graphical and text-based management information, and can unify management and representation to achieve a true graphical operating and graphics, data, network integration. Related Articles | Metrics

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A New Weight Constraint Precision Registration Algorithm Jiang Ruisong, Wei Fayuan, Feng Dayong, Yan Maozhen 2014, 35(2): 167-172.  Abstract ( 144 )   PDF (883KB) ( 334 )   Aiming at the precision registration, a registration algorithm with weight constraint is studied in this paper. This algorithm can ensure the registration accuracy by imposing different weights to different registration points. First, the registration model with weight constraint is established by introducing weight factor into traditional registration model. Second, in order to solve the registration model, a weight constraint SVD-ICP algorithm (wSVD-ICP) is studied based on the classical SVD-ICP algorithm. Especially, the detailed solving process of rotation matrix R and transform matrix T based on wSVD algorithm is shown. At last, two applications are presented for demonstration by using simulation data and measuring data respectively. The results indicate that the algorithm employed in this paper can improve the local registration accuracy significantly by assigning high weight to the high precision demand registration points. Moreover, the algorithm can improve the global registration accuracy and efficiency. Related Articles | Metrics

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On Selection of the Wave Spectrum in Ocean Wave Real-time Rendering Chen Lining, Jin Yicheng, Ren Hongxiang 2014, 35(2): 173-180.  Abstract ( 460 )   PDF (563KB) ( 236 )   The Phillips spectrum is widely used in ocean wave real-time rendering. First, the structure of the spectrum is analyzed. The Phillips spectrum is an instantaneous spatial spectrum. Its frequency spectrum is in accord with the spectrum form raised by Neumann and similar to the P-M spectrum. Its directional distribution function is that recommended by the international towing tank conference. On the hypothesis that the wave energy per unit area of the Phillips spectrum equals that of the P-M spectrum, the spectral constant is computed, and the spectral wind speed is clarified. In addition to the Phillips spectrum, other spectra are tried as well. The P-M spectrum and the directional distribution function of cos-2s form are used to construct an instantaneous spatial spectrum, denoted as PM-cos2s form, and the JONSWAP spectrum and the direction distribution function of Poisson form are applied for constructing an instantaneous spatial spectrum, denoted as J-Po from. The comparison of the rendering results of the three spectra shows that the wave rendered with the Phillips spectrum and PM-cos2s spectrum can reflect wind speed influence on the wave, but cannot embody the fetch length influence, while the wave rendered with J-Po spectrum can show the fetch length effect along with wind speed on the wave. With the same computer hardware, the frame rates of the three spectra are equal. For wave rendering in the nautical simulator, the wind parameter of the selected spectrum should contain the wind speed as well as fetch length, and the generated wave of the spectrum should distribute in (-,] of the wind speed. So J-Po spectrum is more suitable than the other two for the nautical simulator. The method was used in the nautical simulator. Related Articles | Metrics

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Modeling and Real-time Rendering of Sky Illumination Effects Taking Account of Multiple Scattering Ai Zuliang, Zhang Limin, Yu Wenlong 2014, 35(2): 181-187.  Abstract ( 101 )   PDF (605KB) ( 268 )   This paper presents a method of modeling and real-time rendering of the sky illumination effects taking account of multiple scattering with atmospheric scattering based on physical models. Firstly, with the sun and the sky as light sources, the model of the sky illumination effects taking account of multiple scattering is built. Then a reasonable segmented sampling strategy based on a variety of atmospheric particle densities is adopted to simplify the integral of the sky color model to reduce the integral approximation calculation error. By analyzing the simplified model, the pre-computed 2D texture and 3D texture for optical depth are proposed to avoid a run-time calculation of optical depth. Finally, the algorithm is executed on the fragment processor of GPU so that the sky illumination effects taking account of multiple scattering are rendered with high frame rate for real-time applications. Related Articles | Metrics

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Reconstruction of Triangle Mesh for Unorganized Point Cloud Data with Reconstruction of Triangle Mesh for Unorganized Point Cloud Data with  Zhang Wei 2014, 35(2): 188-194.  Abstract ( 178 )   PDF (5378KB) ( 207 )   An approach based on the self-organizing feature map (SOFM) neural network has been developed to reconstruct Delaunay triangle mesh for the unorganized measured point cloud. However the approach suffers from approximation and boundary problems. A triangle mesh model with high approximation precision is proposed in order to reduce the approximation error and boundary error. First all the neurons of the mesh model are trained directly over the unorganized point cloud. Next the neuron location weights of the mesh model are adjusted along the normal vectors of the mesh vertices. Last only the boundary neurons of the mesh model undergo training by the boundary points of the measured point cloud. As a result of applying the proposed mesh model, the boundary error is greatly reduced and the mesh is drawn toward the sampled object with higher precision comparing with the original SOFM training algorithm. The feasibility of the developed mesh model is demonstrated on two examples. Related Articles | Metrics

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3D Modeling of Cardioid Dome Dam Zhao Haifeng, Du Tingna, Ye Rongbo, Zhao Haibo 2014, 35(2): 195-199.  Abstract ( 204 )   PDF (5153KB) ( 235 )   As the most beautiful and the most romantic curve, the cardioid is designed and applied in arch dam for the first time. In researching the geometric characteristics of cardioid, we find a length of very flat curve in it, which is suitable as the axle wire of arch dam, for it can make the resultant force direction of arch dam deflect to the mountain. Therefore, it has a certain applicable value to research cardioid as a new line type of arch dam. Based on researching various parameters of cardioid dome dam, this article establishes mathematical equations of cardioid dome dam, and adopts 3D modeling. It will provide an accurate model for finite element analysis in next step. And it will also provide more selections and meaningful reference for arch dam designing. Related Articles | Metrics

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Five-and Six-Order Trigonometric Spline Curves Yan Lanlan, Han Xuli, Huang Tao 2014, 35(2): 200-207.  Abstract ( 134 )   PDF (689KB) ( 216 )   Using trigonometric functions, two groups of functions with parameters are constructed, which consist of six and seven functions respectively. The properties of the two groups of functions are analyzed. Based on them, two kinds of new spline curves are defined, which have the same structure with quintic and sextic B-spline curves respectively. The new curves not only inherit the basic properties of B-spline curve, but also have some new advantages. For example, when the knot points are equidistant, the new curves can reach C5 continuous at the knot points, and the shape of the new curves can be adjusted by changing the value of the shape parameter with the control points unchanged. In addition, the methods of making the new curves interpolating the first and end points of the control polygon, and the methods of constructing closed curves, etc, are given. The examples in the paper show the new method is correct and feasible. Related Articles | Metrics

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A New Design of Combinational Conical Curve Gauge and Principle of Chart Shen Yijie, Chen Jinchang 2014, 35(2): 208-213.  Abstract ( 116 )   PDF (5348KB) ( 282 )   Through analyzing mathematical principles of designing the conical curve gauge (ellipse gauge, hyperbola gauge and parabola gauge), a set of design theory is put forward based on the optical and geometric properties of conical curve. By applying this theory, a new type of conical curve gauge is designed, which is composed of multiple simple linkage mechanical parts assembly, and which can help quickly draw various normative conical curves common in engineering. It makes up for the disadvantage that the function of general engineering drawing instrument is single and has a good prospect of application. Related Articles | Metrics

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Numerical Analysis and Optimization for Three-Lobe Involute Roots Blower Zhou Kaijun, Tong Yifei, Li Yenong, Xiao Yi 2014, 35(2): 214-220.  Abstract ( 112 )   PDF (1131KB) ( 235 )   In order to obtain the relationship between the changes of base circle radius on three-lobe Roots blower and the blower performance, first the influence of blower rotor involutes from the changes of base circle radius is analyzed from the perspective of geometric principles, and the available range of involute base circle radius is given as well as its influence of area utilization factor. Then based on the numerical analysis method, the blower internal pressure field, the vortex intensity variation and the inlet mass flow rate changes under the same rotor type and different base circle radius are calculated by the dynamic mesh technique. Simulation results show that: the increase of the same kind of rotor type involute base circle radius can weaken the vortex strength and speed, increase inlet mass flow, and improve efficiency of the Roots blower. The blower manufacturer should therefore choose a larger involute base circle radius. Related Articles | Metrics

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Method Research on Robot Arms Reachability Based on Dynamics Analysis Du Hang, Tang Li, Shang Jianzhong 2014, 35(2): 221-225.  Abstract ( 115 )   PDF (870KB) ( 206 )   To realize the quantitative analysis of reachability of on-orbit maintenance technology, maintenance mission can be broken down by stratification first. Based on that, maintenance mission can be proceeded of kinematic control. Remote-control command and autonomic command are emulated through PID emulator, and are transformed into kinematic performers displacement locus curve. Then the ideal maintenance kinematic emulation locus can be reached. After that, the model of the robot arms manufacture and control variations is built. At last, the reliability and validity of maintenance emulation are increased by using virtual kinematic controller to add the variations into the maintenance emulations. Related Articles | Metrics

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Resolution of Under-Constraint Problem Based on DOF Analysis Resolution of Under-Constraint Problem Based on DOF Analysis Wang Lang, Zhang Jingying, Yang Wei, Fan Qiong 2014, 35(2): 226-229.  Abstract ( 70 )   PDF (423KB) ( 197 )   Assembly is an important part in the process of mechanical manufacturing. Under-constraint often exists in the assembly process. If a part is in an under-constraint situation during a large and complex assembly process, it will bring an unexpected result to the related parts which take the surface of the part as constraint reference. To solve the under-constraint problem, the relationship between degrees of freedom (DOF) and constraints is established by building space coordinate system. Logical values can be obtained from the tables. The numbers and types of DOF are determined by logical values, and it provides a quick method to solve the under-constraint problem. Related Articles | Metrics

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Research on the Rapid Design System of Ship Structure Zhan Yiting, Fei Mengru 2014, 35(2): 230-235.  Abstract ( 118 )   PDF (931KB) ( 226 )   Based on the research of the ship structural members knowledge representation and organization mechanism, combining with digital design technique and RPD development thinking, the concept of structural model library to support rapid design and its organizational structure are put forward. Through building a ships type library by using the presentation of knowledge and encapsulating the digital design functionality of the hull structure by using model library and also using distributed database to manage the ship information, a prototype software system is developed. The system achieves rapid design and modification of the three-dimensional solid model of the ship structure, which is demonstrated with a real ship model. Related Articles | Metrics

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Classification and Solution of 3D Assembly Geometric Constraint System Between Two Rigid Bodies Huang Xueliang, Li Na, Chen Liping 2014, 35(2): 236-242.  Abstract ( 108 )   PDF (622KB) ( 171 )   It is a key problem to solve the geometric constraint system between two rigid bodies(GCSBTRD) efficiently and stably when 3D geometric constraint system has been decomposed into a series of GCSBTRDs using equivalent constraint substitution method. In this paper, the decoupling conditions to separately solve angle constraints and distance constraints of GCSBTRDs are presented after analyzing the parametric structure of angle constraints and distance constraints. Then, with the geometric analysis of GCSBTRDs, it is found that the GCSBTRDs consisting of the geometric constraints with more than one constraint degrees can be divided into dozens of patterns, which can all be solved analytically by geometric reasoning method. Subsequently, the adverse impact on numerical solution of GCSBTRDs from additional direction constraint, redundant constraint and contradictory constraint is addressed to demonstrate the advantage of geometric reasoning method. Finally, a hybrid solving strategy based on the classification of constraint combinations is proposed to solve GCSBTRDs, whose effectiveness has been validated by a practical example. Related Articles | Metrics

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The Application of CAD Technology in the Process of Aircraft Bionic Design Zhao Wendi, Liu Jinghua, Liang Jianhong, Wang Tianmiao, Yang Xingbang, Yao Guocai 2014, 35(2): 243-249.  Abstract ( 184 )   PDF (907KB) ( 320 )   Unmanned amphibious aircrafts have become a hot topic in recent researches. In order to make aircrafts achieve 3 navigation states which include travelling underwater, travel state transition from water to air, and flying in the sky, we need to solve several technical matters such as variable density, structural transformation, power conversion and so on. Meanwhile, the studies on hydromechanics, dynamics of interface, aerodynamics are also crucial. Australasian gannets, like many other seabird species, locate pelagic prey from the air and perform rapid plunge dives for their capture. This kind of birds can fly through both the water and the air, so the research on its actions is of great immense significance to the study of the unmanned amphibious aircrafts. The processes of bionic design methods for the unmanned amphibious aircraft are introdeced, and the functions of CAD techniques using in the bionic design process are explained. Related Articles | Metrics

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Research on the Industrial Design Reform for NCP-400L CNC Lathe Zhu Yan, Cao Meng 2014, 35(2): 250-255.  Abstract ( 239 )   PDF (1310KB) ( 213 )   A lot of electromechanical products in China have been close to the world advanced level in technology, but insufficient attention is given to industrial design, which directly affects the competitiveness of our products on the market at home and abroad. Through design and practice of the NCP-400L CNC lathe industrial design improvement, the article discusses the method of industrial design in the premise of maintaining the basic structure of the product and the original processing equipment unchanged. By adjusting the proportion of form, color and human-computer interaction design means, the harmonization between visual image and the inherent quality of the products is realized. Related Articles | Metrics

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A Key Pose Frame Extraction Approach Combined with Trajectory from Weightlifting Video Wang Xiangdong, Zhang Jingwen, Wu Lifang, Xu Wenquan 2014, 35(2): 256-261.  Abstract ( 99 )   PDF (1824KB) ( 268 )   In this paper, a trajectory guided scheme is proposed to extract the key poses frame automatically. First, the barbell trajectory is extracted from the weight lifting sport video. Then the barbell trajectory and poselet are combined for pose extraction. Some key poses are extracted from the extreme point of the barbell trajectory. But the other poses are extracted by using the poselet based algorithm. SVM(Support Vector Machine) classifiers based HOG(Histogram of Gradient) is trained for each pose. Then the pose is detected in the multi-scale images. Statistical similarity is computed in multi-scale to measure the possibility and determine which is the best key frame. It resolves the problem of higher inter-frame similarity. The experimental results show that the proposed scheme can improve both the precision and performance of pose extraction. Related Articles | Metrics

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Highly Adaptive Image Retrieval Technology Based on Fast Wavelet Transform Liu Jun, Ru Qingyun 2014, 35(2): 262-267.  Abstract ( 97 )   PDF (651KB) ( 171 )   In the existing research in the field of content-based image retrieval, image features obtained by adaptive wavelet transform have a wide range of applications. There is a common problem in these methods that different query images are described with the same wavelet basis. In order to improve the adaptive capacity of image retrieval techniques, different wavelet bases are designed for different query images. Different wavelet bases can be used in adjusting retrieval performance for different query images, and the extraction time does not significantly increase. The experimental results show that this new image retrieval technology has a high adaptive capacity and its retrieval performance is also greatly improved. Related Articles | Metrics

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Research on Methods of Feature Extraction and Recognition of Two-Dimensional Phonocardiogram Cheng Xiefeng, Cai Huamin 2014, 35(2): 268-273.  Abstract ( 166 )   PDF (2711KB) ( 230 )   The one-dimensional heart sound signal is converted into a two-dimensional phonocardiogram, then image feature of heart sounds based on image processing technology in a two-dimensional phonocardiogram is extracted. Firstly the wavelet noise reduction and amplitude normalization of one-dimensional heart sound by one-dimensional signal processing method are realized, and then heart sounds after the treatment are converted into two-dimensional phonocardiogram with uniformity and comparability, and pretreatment. And the image characteristics of two-dimensional phonocardiogram are analyzed, which is characterization of heart sounds’ physiological information combining with heart sounds’ physiological significance and two-dimensional phonocardiogram’s image features, and the focus is on vertical and horizontal ratio of coordinate and sequence code of inflection point. At last, the feasibility of classification and identification is explored of 2D-PCG using Euclidean distance and Support Vector Machine (SVM) based on vertical and horizontal ratio of coordinate, sequence code of inflection point and wavelet coefficients. Experimental results show that the three features can achieve the classification and recognition of the two-dimensional phonocardiogram, and inflection point sequence code gets the highest recognition rate. The method of 2D-PCG classification and identification based on a two- image processing has the feasibility and practical applicability, and has broad application prospects. Related Articles | Metrics

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The Shape Recognition of Tyre Marking Points Based on Support Vector Machine Wang Yong, Guo Hui 2014, 35(2): 274-279.  Abstract ( 76 )   PDF (606KB) ( 318 )   The tyre marking points play an important role in the tyre classification. However, manual recognition is laborious and is easily influenced by physiological factors. A method of shape recognition of tyre marking points based on Support Vector Machine(SVM) is proposed in this paper. Firstly, the image of tyre marking points will be denoised by median filter and segmented based on the gray level histogram. Then the edge of tyre marking points will be detected by Canny algorithm, and the detected edge will be represented by Fourier transform. Lastly, those Fourier coefficients will be used as input to SVM classifier for distinguishing shapes of tyre marking points. The experimental results show that the proposed method can achieve high correct shape recognition rate and improve the efficiency of recognition of tyre marking points. Related Articles | Metrics

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Desktop Haptic Virtual Assembly Lu Liting, Liu Lin, Xiong Wei 2014, 35(2): 280-284.  Abstract ( 148 )   PDF (5529KB) ( 227 )   Since the workspace of PHANToM Desktop is not big enough, an improved method of dynamic space matching and a viewpoint navigation technique whenever the proxy moving outside the frustum are proposed in this paper. Firstly, the three-dimensional space matching is considered when the device space is matched with the view frustum, so that a high operating precision near the viewpoint and a large visual range at the far viewpoint area is implemented. Then the workspace outside the mapping area in device space is elaborately utilized for viewpoint navigation, so the bigger visual range can be obtained. During the virtual assembly process, the contact force computed real-time can be applied to perceive the shape and hardness of virtual objects for users. Additionally, the constraint force generated according to mass-spring model can be used to locate parts. Related Articles | Metrics

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A Real Time Fingertip Detection Method Combining Curvature and Paralleled-Vector Wang Yun, Gan Quan, Li Lin 2014, 35(2): 285-289.  Abstract ( 101 )   PDF (873KB) ( 309 )   According to the feature of the fingers' geometry being roughly parallel, this paper proposes a new method based on curvature and paralleled-vector for fingertip detection. This method first uses depth image information from complex background environment to segment hand quickly, and then based on morphological operations and median filter for smoothing, edges can be extracted. Subsequently, we can use curvature to locate the position of the virtual fingertips. Finally the paralleled-vector feature is adopted to rule out error detection points. The experimental results show that the method in different finger motions, different light intensities, and complex environment can locate the position of the fingertips. Besides, the fingertips detection rate can reach 98.64%. Related Articles | Metrics

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Exploration of Virtual Model Size Measurement Methods Wang Chenggang, Zhao Qiping, You Xianfeng 2014, 35(2): 290-295.  Abstract ( 117 )   PDF (1429KB) ( 194 )   This paper analyzes the status of practice teaching of model measuring, draws up three modes of the dimensional measurement of model measuring in accordance with the characte ristics of the model measuring training, explores the concrete implementation method of dimensional measurementbased on eDrawings browser virtual model, then applies it in teaching of "Engineering Graphics" course. It also provides a best practice for virtual model measuring method and some application examples, which include important ways and approaches to improve and strengthen students’ hands-on and model measuring abilities. Related Articles | Metrics

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Exploration and Practice of Teaching Reform of Engineering Drawing Xiong Wei, Liu Lin, Chen Jinchang 2014, 35(2): 296-300.  Abstract ( 156 )   PDF (1163KB) ( 363 )   Some ideas and methods for class teaching reform on current problems of multimedia teaching are proposed. Based on constructivist learning theory, following the students' cognitive psychology, engineering drawing classroom teaching process is designed. Based on traditional teaching, a new multimedia teaching method is established. By the melange of "chalk blackboard" and multimedia technology, a real hand-drawing process context can be simulated. By the cooperation of gesture and animation, a configuration process scenarios can be achieved. By the use of physical models and graphics software, an interactive learning environment can be brought about. The evaluation of students and peers proves that this novel method is a useful attempt to reform classroom teaching on engineering drawing. Related Articles | Metrics

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Study on Applied Game Evaluation Index Based on Didactical Events Wang Qing, Chen Hong, Zhao Haiying, Liu Yan, Zhu Dehai 2014, 35(2): 301-307.  Abstract ( 159 )   PDF (686KB) ( 230 )   Applied game aims to help player acquire knowledge, improve skills and enhance emotional quotient through game playing process. However, evaluation for effects of combining playing and learning is still open. This study investigates correlations between game and learning and proposes a methodology for applied game evaluation index by extending information procession model to nine didactical events accordingly integrating learning processes into game playing. The evaluation method involves examining an applied game’s capability of supporting the nine didactical events and its proposed pedagogical purpose and gives the degree of practical value for the game. It is expected that the evaluation index for applied game can provide a practical reference specification for applied game assessment. Related Articles | Metrics

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Topology Preserving Word Cloud Visualization Algorithm for Cross-Language Replacing Lu Qiang, Tang Liang, Ma Kunle, Liang Chong 2014, 35(2): 307-312.  Abstract ( 78 )   PDF (732KB) ( 272 )   The word cloud may be unstable when replacing some words or even all words from it. This paper presents a visualization algorithm to solve the problem and ensure that the fial topology of the cloud will be totally consistent with the original one. The algorithm can be congcluded as follows. Firstly, all the words are scattered in the cloud to avoid overlapping. Secondly, the Delaunay Triangulation may be used on the words to obtain the mesh which can make sure the topology not be destructed after the last step being executed. Fingally, the words are compacted on the basis of the comtrol mesh to reduce the empty space. Then the final layouts of the word cloud may be formed.This paper may take the situation that all the words may be translated in other language for example to introduce the method in detail. The algorithm is a new breakthrough in keeping the stability and topology of the word clouds. Related Articles | Metrics

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Research of 3D Annotation Information Management Method Liu Ronglai, Wu Yuguang 2014, 35(2): 313-318.  Abstract ( 107 )   PDF (808KB) ( 283 )   An information management method of 3D annotation is proposed, which aims at handling the condition of "hedgehog" in 3D annotation information. The annotated features related by geometric dimension and tolerance are grouped by the association relationship graph, the 3D annotation symbols of a part are categorized and displayed with the association relationship graph. The definition and the establishment method of the 3D annotation information graph are studied and the graph search algorithm of the association relationship is established. A prototype software of category management and display of 3D annotation is conducted by the UG/NX7.5 platform and VC++ Language, and a lot of example parts are tested on the software, it proves that the method is feasible and effective. Related Articles | Metrics

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MID-Based Mobile Law Enforcement Applications Model for Inspection and Quarantine Bao Xianyu, Li Jun, Wang Yang, Wu Yan 2014, 35(2): 319-324.  Abstract ( 63 )   PDF (766KB) ( 192 )   To solve the problems of the existing mobile law enforcement system in software, function implementation and information security, a mobile enforcement application model is provided for the inspection and quarantine using the MID terminal. The composition of the hierarchical model is described in detail, and a suitable information security mechanism for the model and the realization of security mechanism respectively from terminal side, network side and client side are given. The actual application shows that the model is practical and effective, which can effectively enhance the inspection and quarantine information law enforcement level and law enforcement efficiency. Related Articles | Metrics