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28 August 2015, Volume 36 Issue 4 Previous Issue    Next Issue

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Progressive Mesh Generation Algorithm Based on Inverse 3 Subdivision Zhang Weihua, Wang Yuhui 2015, 36(4): 495-502.  Abstract ( 121 )   PDF (846KB) ( 221 )   A progressive mesh algorithm is proposed to accelerate the transmission and display of 3D graphics based on inverse 3 subdivision. Main steps of the algorithm are as follows. Firstly, the original mesh is simplified by edge contraction. Secondly, vertexes of control mesh are modified for the purposes of their subdivision limit points which are approximate to the original mesh. Thirdly, the high-density mesh is obtained by 3 subdivision. Finally, inverse 3 subdivision is implemented. In detail, some vertexes are removed from mesh after each time of inverse 3 subdivision. The base mesh and a set of displacement values are kept for reconstructing a series of progressive meshes. For 3 subdivision, the growth rate of number of triangles is lower than some other subdivision scheme. As a result, more levels of meshes can be obtained by inverse 3 subdivision. Experiment results show that progressive meshes generated by 3 subdivision can meet the need of fast and multi-resolution display. Related Articles | Metrics

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High Identification 3D Human Body Model Reconstruction Method Based on the Depth Scanner Han Kai, Pang Zongqiang, Wang Long, Yue Dong 2015, 36(4): 503-510.  Abstract ( 123 )   PDF (4075KB) ( 511 )   The printing quality of 3D portrait in 3D printing photographic house, depend on the 3D scan of the three dimensional human body model identification. However, the traditional 3D body scanner is expensive, complicated manipulation and other reasons, 3D portraits of high printing costs, time-consuming and less accurate printing. In view of these shortcomings a method is proposed based on the deep scanner reconstruct the high degree of recognition three-dimensional human body model. The method combines with the advantages of three groups of different types of the depth scanner, collaboration, respectively to obtain high precision characters facial features and hair detail point cloud data, upper body and the body surface contour point cloud data. Then, the captured three sets of point cloud data will be aligned, replaced, registered by introducing feature points and iterated closest point. The registered of non-topological relations of point cloud data for surface reconstruction can get high precision of 3D human body model. The method of scanning time is shorter, at a relatively low cost to build the 3D portrait with high identification model. Related Articles | Metrics

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Discretely Sampling and Reconstructing Simple Planar Closed Curves Fan Lipeng, Wang Liying, Pang Mingyong 2015, 36(4): 511-515.  Abstract ( 106 )   PDF (1562KB) ( 316 )   A robust algorithm is proposed for discretely sampling continuous planar curves and reconstructing the curves from the sampled point sets. The algorithm covers two processes, sampling and reconstruction. In the sampling part, the points are evenly obtained from a given planar closed curve, and then the distances are calculated between each point and the medial-axis of the planar area surrounded by the closed curve. Subsequently, the sampling intervals are decided by the distances and finds the sampling points. In the reconstruction part, a Delaunay triangulation is first built for the sampled points, and then edges are selected from the triangulation to build the initialize graph. Finally, the reconstructed curve is obtained by modifying the graph to a new version. Experiments show that the point sets sampled by our algorithm are locally adapted to the local geometric characteristics of the curves, and the reconstructed curves can approximate the original curves well. Related Articles | Metrics

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A Collision Detection Algorithm Using Delaunay Triangulation Zhu Erxi, Xu Min, He Yuanjun 2015, 36(4): 516-520.  Abstract ( 97 )   PDF (875KB) ( 333 )   The distribution and movement of objects in virtual reality show varied complications, so that the real-time and accuracy of collision detection algorithms are difficult to meet the requirements. A real-time algorithm is presented for multi-body collision detection based on Delaunay triangulation. The algorithm uses bounding volume close fitting objects, constructs discrete aggregates using centers of bounding volume, generate Delaunay triangular mesh, implements collision detection. This algorithm avoids the unfavorable factors of bounding volume hierarchy and space division. The update operation of objects is defined in the local triangles. The experiments show that the algorithm can meet the real-time and accuracy requirements in the multi objects detection system in the presence of several moving objects. Related Articles | Metrics

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Algorithm for Generating Five Block Mode Cutting Patterns of Single Rectangular Items Yi Xiangyang, Pan Weiping, Zhang Junhui 2015, 36(4): 521-525.  Abstract ( 110 )   PDF (427KB) ( 237 )   It is widely appears in manufacturing field of plate segmentation and the logistics industry field of pallet loading that how to finding a maximal layout for identical small rectangles on a larger rectangle. The large rectangle is divided into five blocks using five-block mode, then the problem is solved to arrange the identical small rectangular into each blocks. Firstly, the dynamic programming method is used to generate the entire layout of rectangular in blocks in once. Then, the enumeration method is used to consider all of five blocks combination. The combination is selected to generate the final pattern which have the maximal number of rectangular. Several examples are used to test the proposed algorithm, and comparing the algorithm with other 4 kinds of single layout algorithm. The experimental results show that the algorithm is efficient in both the layout utilization rate and the cutting process with a reasonable computing time. Related Articles | Metrics

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Optimization Algorithm for Rectangle Packing Based on Improved Lowest Horizontal Line Method and Genetic Algorithm Liu Haiming, Zhou Jiong, Wu Xinsheng, Luo Jiaxiang 2015, 36(4): 526-531.  Abstract ( 196 )   PDF (349KB) ( 394 )   For the issue of rectangle packing problem, traditional lowest horizontal line method might generate certain empty blocks that were not used, which would cause unnecessary waste of material. To solve the problem, heuristic estimate is introduced into search process to achieve rectangle filling for the empty blocks and improve utilization. For optimization packing sequence of rectangles using genetic algorithm, a new strategy of setting different genetic factors by stages of evolution process is applied to improve algorithm performance. The two improved methods are combined in union to solve the rectangle packing problem. The test data of packing show that the proposed algorithm can effectively improve packing results and improve utilization of material. Related Articles | Metrics

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Optimal Parameter Values of the Curves with Shape Parameters Liu Chengzhi, Li Juncheng, Yang Lian 2015, 36(4): 532-536.  Abstract ( 100 )   PDF (370KB) ( 203 )   Although the curve with shape parameters has become one of the most popular topics in the curve modeling, but the values of shape parameters are always given as intervals, while in practice, the optimal parameter values is often needed to ensure that the curves have good fairness and smoothness. According to this problem, firstly, a automatic mathematical model which is based on the fairing criterion is established to obtain the optimal parameters, and then the concrete steps of genetic algorithm is given to solve the model. At the last, two classes of curves are used as examples to illustrate the effectiveness of our methods. Related Articles | Metrics

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Analysis of Rolling Friction Contact between Free Single Abrasive and Optical Element Chen Weiping, Gao Chenghui, Ren Zhiying, Lin Chunsheng 2015, 36(4): 537-545.  Abstract ( 67 )   PDF (14367KB) ( 76 )   In order to study the deficiency of the friction and wear mechanism analysis and how to effectively control the impact of the subsurface damage during the process of rolling contact between free abrasive and optical element. Based on the rolling contact theory, a rolling contact model of dual fractal surfaces is established between single free abrasive and optical element, and the simulation of the microscopic dynamic rolling contact process is achieved by the use of the FEM simulative analysis. Through the analysis of the contact force, contact stress, abrasive angles and related stress fields under different shear strength, showed that, with the shear strength increased, the friction coefficient of the contact interface between the grain and optical surface will be decreased, the best grinding abrasive angle is 105°–120°, the influence of the fractal abrasives on subsurface damage is greater than the spherical grains, the necessity and importance of the research about the free fractal abrasive in rolling contact is indicated, and a certain significance for deeper understanding of the friction mechanism during the contact process is provided. Related Articles | Metrics

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Finite Element Analysis of Dynamics of High Speed Bearing Zhang Li, Qi Huaming, Xu Juan, Ji Zhijun 2015, 36(4): 546-550.  Abstract ( 108 )   PDF (968KB) ( 446 )   High speed bearings are key components for safe operation of high-speed train. There is a close relationship between rolling contact behavior and the service life of roller bearing. A 3D virtual model for high speed railway double row tapered roller bearing is established using automatic surface to surface contact between minimum component, and a finite element analysis of dynamic contact characteristics of the bearing under straight-line driving and minimum radius steering under scheduled velocity is conducted respectively using ANSYS/LS-DYNA. Speed, acceleration of bearing, load distribution of roller, time-history curve of contact element about second principal stress and vibration of holder is studied. The results can serve as reference in design and construction of high speed bearing. Related Articles | Metrics

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Classification of Cultural Relic Fragments Based on Salient Geometric Features Kang Xinyue, Zhou Mingquan, Geng Guohua 2015, 36(4): 551-556.  Abstract ( 136 )   PDF (2364KB) ( 260 )   Identifying culture relic fragments which shapes are severely damaged has low accuracy by use of the traditional classification method based on shape features of culture relic fragments. There are some regular salient geometric features on the surface of culture relics which is embossed or marked, and extracting such structures can descript shape features of damaged culture relics better. A classification method of culture relic fragments is presented based on salient geometric features. Frist, the definition of salient geometric feature is proposed, and the local surface description is given. Secondly, salient geometric features on the surface of Terra-Cotta Warriors fragments are extracted by clustering local surface descriptions. At last, salient geometric features are matched using EMD method, and the classification is identified. The experiment results indicate this method has high accuracy for the classification of Terra-Cotta Warriors fragments. Related Articles | Metrics

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Robust Image Fingerprint Algorithm Based on Image Normalization and Watson Visual Model Zheng Shuli, Zhang Yunling, Hu Donghui, Li Dandan 2015, 36(4): 557-562.  Abstract ( 80 )   PDF (828KB) ( 275 )   With the development of multimedia application, digital images are easy to be manipulated or tampered illegally. A novel image fingerprint algorithm is proposed which can be used for image authentication and identification. The image is firstly normalized to make it robust against any affine transforms. Then the normalized image is divided into 8×8 blocks and discrete cosine transform is applied to each block. The DCT coefficients are weighted by the contrast masking matrix of Watson visual model. Then weighted DCT coefficients is quantified to be bit sequences to form the image fingerprint. Since a key is used in the algorithm, the fingerprint is hard to be forged. The experimental results indicate that the proposed method is robust against modification including geometric transformation such as rotation and scaling. Related Articles | Metrics

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An Image Segmentation Method by Combining Fuzzy C-Means Clustering with Graph Cuts Optimization for Multiphase Level Set Algorithms Song Lin, Gao Mantun, Wang Sanmin, Wang Shuxia 2015, 36(4): 563-569.  Abstract ( 120 )   PDF (2333KB) ( 233 )   Multiphase level set model is sensitive to initial contour curve and has huge computation in the process of the multiple objectsʹ segmentation. A novel Image segmentation method is presented for multiphase scenario, which initializes the multiphase level set function by coarse image segmentation using fuzzy C-means clustering algorithm and applies graph cuts algorithm to acquire multiphase output image. The method can effectively reduce the sensitivity of the multiphase level set algorithm to initial contour and is easier to gain the multiphase output image by graph cuts algorithm. At the same time, the multiphase level set function quickly converge to the minimum energy value with small amount of calculation and high computational efficiency using the graph cuts algorithm. The experiments show that this method has better segmentation effect and higher efficiency of image segmentation. Related Articles | Metrics

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A Otsu Threshold Segmentation Method Based on Rebuilding and Dimension Reduction of the Two-Dimensional Histogram Chen Jinwei, Wu Bing 2015, 36(4): 570-575.  Abstract ( 124 )   PDF (464KB) ( 258 )   The issue of poor resistance to noise and unreasonable is pointed out based on two-dimensional histogram regional straight points method. A new threshold segmentation method is proposed, and the calculation formula of the method is deduced. Firstly, in this method, noise interference weakened for threshold′s segmentation through the reconstruction of two-dimensional histogram based on detailed analysis of noise distribution in the two-dimensional histogram, and then, the region division is transfered from eight partitions into two partitions in two-dimensional histogram. Thus the two-dimension search space of threshold is reduced to one-dimension. Finally, simulation results of existing two-dimensional histogram segmentation algorithm and our method are given respectively. Theoretical analysis and experimental results show that our method could be used in nearly all the two-dimensional histogram threshold segmentation, especially in threshold segmentation with the contaminated image. It makes the inner part uniform, the edge accurate in the threshold image and has better tolerance capability to noise. The running time is significantly reduced. Related Articles | Metrics

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Improved Diamond Motion Estimation Algorithm Based on Search Prediction and Threshold Decision Liu Yan 2015, 36(4): 576-580.  Abstract ( 92 )   PDF (479KB) ( 210 )   To improve the compression efficiency of the video, a self-adaptive diamond search algorithm is put forward based on traditional diamond search algorithm. The algorithm is improved in the prediction of the beginning search spot, diamond search mode and search suspended algorithm by bringing in dynamic threshold. It realizes the self-adaptive search, which reduces the internal redundant SAD operation and skips all the irrelevant blocks in the search area. The experiment result shows that the self-adaptive diamond search algorithm suits all kinds of motional video sequence, especially those sequences changing poignantly in movement. Comparing to the FS algorithm, the improved algorithm decreases approximately 95% of the motion estimation time (MET) of all the sequences under the condition that the PSNR and the code rate value are very close to FS algorithm. The motion estimation time is greatly decreased. Related Articles | Metrics

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3D CT Defects Segmentation of Solid Rocket Motor Based on the Morphology and Otsu Chen Peixing, Wang Mingquan, Li Shihu, Hou Huiling, Wang Yu 2015, 36(4): 581-586.  Abstract ( 101 )   PDF (1313KB) ( 367 )   In order to accurately judge the nature of the defect on solid rocket motor and the possible damage to the engine, it is needed to observe and analyze problems in the three dimensional space. However, the defects is usually determined by observing the two-dimensional slice CT image sequences and judging by subjective analysis of two-dimensional images in traditional defect analysis, and it requires abundant experience of the user. In order to analyze the defect structure more accurately and stereoscopically, the solid rocket motor industrial CT 3D volume data is used to extract defects by using of the combination of morphological and Otsu threshold segmentation method to segment. The 3D volume data of the defect structure is reconstructed herein. Finally, 3D visualization tools are used to display the volume data. The experiment results indicate that this method is effective and accurate to segment and extract the solid rocket motor 3D CT image defects, and it has pretty strong robustness. Related Articles | Metrics

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Smoke Detection Based on Multi-Feature Fusion Wu Dongmei, Li Baiping, Shen Yan, Wang Jing, He Rong 2015, 36(4): 587-592.  Abstract ( 125 )   PDF (1325KB) ( 449 )   A new smoke detection method based on video is researched due to the weakness of the traditional fire detection technology. Firstly, according to the characteristic of the smoke color, the suspect smoke regions are extracted in video sequences. Then, looking for three dynamic characteristics of smoke in the suspected smoke area, there are three features extracted, which respectively are the growth of the area in the smoke spread, irregular contour feature of the smoke region and the background to blurred when smoke appeared. And those three dynamic characteristics are fused by a BP neural network to determine smoke or not. Test results show that the multi-feature fusion smoke detection algorithm can identify smoke in video accurately, real-time and effectively. Related Articles | Metrics

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Image Denoising Based on Adaptive Contraction Function Contourlet Transform Niu Weihua, Meng Jianliang, Wang Ze, Cui Kebin 2015, 36(4): 593-602.  Abstract ( 114 )   PDF (968KB) ( 203 )   To solve some problems on image denoising, such as losing details and falling into poor effects, a method of image denoising is proposed based on adaptive contraction function Contourlet transform algorithm. According to the basic Contourlet transform form and combing the soft threshold and hard threshold contraction function, the adaptive contraction function is defined. Experimental results show that the proposed method can greatly remove noise, effectively improve peak signal to noise ratio, mean squared error and image enhancement factor of image quality index. After combining the improved threshold function, the image has better visual quality. Related Articles | Metrics

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The Power Allocation Strategy for Plug-in Hybrid Electric Vehicle Hybrid Power System Gao Jianping, Zhao Jinbao, Ge Jian, Xi Jianguo 2015, 36(4): 603-608.  Abstract ( 65 )   PDF (809KB) ( 236 )   According to the vehicle performance requirements and driving cycle, the original single power system of a plug-in hybrid electric vehicle is transformed into hybrid power system which is consist of battery and super-capacitor that are matched by decoupling the requirement of energy and power. The power allocation strategy of hybrid power is built in Matlab/simulink. The simulation results show that the hybrid power system can reduce the battery charge cycles, effectively avoid the impact of battery from the large current and can give full play to high power characteristics of super-capacitor. Comparing with the former, the fuel economy and pure electric mileage are increased by 3.4% and 1.3%. Related Articles | Metrics

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Design and Simulation of Transplanting Mechanism with Planetary Spur Gears and Non-Circular Gear Zhang Kai, Tao Ye, Gao Kuan, Lin Huizhou 2015, 36(4): 609-614.  Abstract ( 210 )   PDF (1043KB) ( 298 )   Transplanting mechanism with planetary spur gears and non-circular gear was developed, in which planetary gear train with eccentric gears and non-circular gear is used. The mathematical model of eccentric gear and non-circular gear′s pitch curve was established and the gear pitch curve equation was obtained. Combining the KISSSOFT with MATLAB software to design the non-circular gear, kinematic models of the transplanting mechanism are established, and optimized the parameters of the mechanism by using self-compiled packages based on MATLAB. Virtual prototype simulation in ADAMS was performed after finishing the 2D and 3D design of the transplanting mechanism. The static trajectory and dynamic trajectory of the needle tip are obtained, and compared these with those of theoretical analysis. The results verify the feasibility of transplanting mechanism with planetary spur gears and non-circular gear which was applied on transplanter. Related Articles | Metrics

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Logical Frame and Its Application in Graphics Education for Architecture Ichnography Yao Ji 2015, 36(4): 615-621.  Abstract ( 101 )   PDF (507KB) ( 352 )   Education logical frame should be established as the teaching method and thinking mode for architecture engineering graphics education. The frame is composed of knowledge logic, graphic logic and education logic which were discussed in the article. There exists the internal strict knowledge logic in engineering graphics curriculum content. Teachers can make students understand engineering graphics faster by application of logic frame. Classroom education can be conducted by revealing relationships between different knowledge points and making students read and understand engineering drawings stage by stage. The methodology advocated in the article is significant to the inspiration of thinking mode, consolidation of previous knowledge and acceptance of new knowledge. Related Articles | Metrics

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The Practice and Enlightenment of Short Course of Technical Drawing &CAD by American Professor Zhu Keqian, Liu Shanshu, Ding Jianning, Zhang Lin, Yuan Huixin, Lu Zhangping, Yuan Ningyi, Cai Yongmao 2015, 36(4): 622-625.  Abstract ( 104 )   PDF (935KB) ( 244 )   Changzhou University invited an American professor to give a short course of technical drawing & CAD to the students majored in process equipment. The curriculum content, course organization, textbook and characteristics of teaching are discussed in detail in this paper. Some useful references to us are also illustrated. Related Articles | Metrics

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Research and Practice of Cartography Curriculum Based on ＂One Body with Wings＂ Luo Huafeng 2015, 36(4): 626-630.  Abstract ( 84 )   PDF (340KB) ( 209 )   The curriculum system of modern cartography based on the practical ability raise is raised in order that the theory and practice are influenced by each other. The one body conceive with two wings is proposed on the base of the reform of cartography curriculum at home and abroad. The theoretical study is the one body, and computer virtual simulation and field practice are the two wings. The teaching practices have proved that modern cartography curriculum based on the practical ability not only trains students′ practical ability and scientific research ability, but also improves their ability of self-regulated learning and innovation. Related Articles | Metrics

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Improving Innovative Education for Mechanical Drawing by "Skill Competition and Skill Examination" Xu Guoyu, Zhang Meng, Lan Chaofeng 2015, 36(4): 631-637.  Abstract ( 76 )   PDF (319KB) ( 236 )   Aiming at the demand for innovative education reform on mechanical drawing, "Promoting studying and teaching by the competition and examination" is put forward. On the one hand, the students' are promoted to study the curriculum by initiative "blended learning" and to participate in the innovative activity of science and technology. On the other hand, teachers are guided to reform the curriculum system, content, teaching material, teaching mode and aided learning mode. The results show that "Promoting studying and teaching by the competition and examination" is good for improving learning effect, innovative ability and practice skills of student, and ultimately it is contribute to the cultivation of high-skilled creative talents. Related Articles | Metrics

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The Combination Learning of Engineering Technical Basis Courses of Based on Constructivism Theory Guan Qiaojuan 2015, 36(4): 638-643.  Abstract ( 75 )   PDF (243KB) ( 216 )   The higher vocational education needs to not only lay the foundation of sustainable development for students, but also cultivate the ability of sustainable development for those applied talents. Exploring a combined learning method of the basic technical courses in high vocational college by the theory of constructivism, the characteristics and the construction feature of these courses and state the idea, feature and strategy are introduced in the procedure of promoting combined learning. Related Articles | Metrics

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Operation Simulation and Preliminary Research on Control Accuracy of Hand Operation Affected by Vibration Wang Dongyang, Yang Guang 2015, 36(4): 644-649.  Abstract ( 91 )   PDF (1111KB) ( 356 )   In operations controlled by hands and arms, vibration transmitted from controller to hand and arm would have an impact on the accuracy of operation. The effects of vibrations are investigated with different parameters on operation accuracy, with the help of a program to simulate a path tracing operation in virtual space. A programmable haptic device is used as the controller. Vibration frequency has a nonlinear effect on operation errors, and significant effects occur in the vicinity of 2 Hz. Vibration amplitude has an approximate linear effect on operation errors, and operation errors can also be affected by vibration direction. Related Articles | Metrics

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Image Matching Algorithm Based on SURF Feature Extraction and FLANN Search Feng Yidong, Sun Yue 2015, 36(4): 650-654.  Abstract ( 125 )   PDF (1164KB) ( 1075 )   The traditional algorithm of image matching exist the problems of little feature information and high rate false match. An image matching algorithm is presented based on SURF feature extraction and FLANN search. Firstly, the extremum value of local image is gotten using the Hessian matrix. Secondly, the feature vector is simultaneously processed in multilayer image scale space by using of different size feature description. Finally, the FLANN algorithm is used for feature matching. The experiments show that this algorithm is better than the traditional algorithm of image matching in the aspect of effectiveness and efficiency. Related Articles | Metrics