The Experts below are selected from a list of 34995 Experts worldwide ranked by ideXlab platform
Qinchuan Xin - One of the best experts on this subject based on the ideXlab platform.
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Topology-Preserving and Geometric Feature-Correction Watermarking of Vector Maps
IEEE Access, 2020Co-Authors: Xinchang Zhang, Ying Sun, Xin Jiang, Qinchuan XinAbstract:Digital watermarking is an effective method of vector map copyright protection. However, the topology and Geometric Features are potentially influenced by the disturbances of vertices caused by watermark embedding, thus reducing the availability of watermarked vector maps. In this research, we propose a post-correction method for two-dimensional vector map watermarking, by which the topology and Geometric Features of the input data can be preserved, while using only conventional watermarking techniques. In the proposed method, the Maximum Perturbation Regions (MPR) of vertices and direction angle constraints methods of adjacent lines are adopted to undergo multi-azimuth checks of watermarked vertices, which may cause changes of the Geometric Features and topology. After that, the coordinate adjustment method which is based on the homonymous vertices topology association and the MPR are combined for topology and Geometric Feature correction. For watermark embedding, two classic frequency domain watermarking techniques, Discrete Fourier Transformation (DFT) and Discrete Wavelet Transformation (DWT), phase based and low-frequency coefficient based respectively, are also adopted. The scheme was conducted on a building vector map and a road vector map. The experimental results show that the proposed method can ensure the topology consistency and Geometric Feature similarity of vector maps before and after embedding watermarks. Moreover, this method has little interference with the maps, which improves the usability of the watermarked vector map.
Yan Zhang - One of the best experts on this subject based on the ideXlab platform.
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Local Surface Geometric Feature for 3D human action recognition
Neurocomputing, 2016Co-Authors: Erhu Zhang, Wanjun Chen, Zhuomin Zhang, Yan ZhangAbstract:This paper presents a novel Local Surface Geometric Feature (LSGF) for human action recognition from video sequences captured by a depth camera. The LSGF is extracted from each skeleton joint in point cloud space to capture the static appearance and pose cues, which includes joint position, normal, and local curvature. A temporal pyramid of covariance matrix is exploited to model both pairwise relations of Features instead of Features themselves and the temporal evolution. Finally, Fisher vector encoding is imported as a global representation for a video sequence and SVM classifier is used for classification. In the extensive experiments, we achieve classification results superior to most of previous published results on three public benchmark datasets, i.e., MSR-Action3D, MSR DailyActivity3D, and UTKinect Action.
Xinchang Zhang - One of the best experts on this subject based on the ideXlab platform.
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Topology-Preserving and Geometric Feature-Correction Watermarking of Vector Maps
IEEE Access, 2020Co-Authors: Xinchang Zhang, Ying Sun, Xin Jiang, Qinchuan XinAbstract:Digital watermarking is an effective method of vector map copyright protection. However, the topology and Geometric Features are potentially influenced by the disturbances of vertices caused by watermark embedding, thus reducing the availability of watermarked vector maps. In this research, we propose a post-correction method for two-dimensional vector map watermarking, by which the topology and Geometric Features of the input data can be preserved, while using only conventional watermarking techniques. In the proposed method, the Maximum Perturbation Regions (MPR) of vertices and direction angle constraints methods of adjacent lines are adopted to undergo multi-azimuth checks of watermarked vertices, which may cause changes of the Geometric Features and topology. After that, the coordinate adjustment method which is based on the homonymous vertices topology association and the MPR are combined for topology and Geometric Feature correction. For watermark embedding, two classic frequency domain watermarking techniques, Discrete Fourier Transformation (DFT) and Discrete Wavelet Transformation (DWT), phase based and low-frequency coefficient based respectively, are also adopted. The scheme was conducted on a building vector map and a road vector map. The experimental results show that the proposed method can ensure the topology consistency and Geometric Feature similarity of vector maps before and after embedding watermarks. Moreover, this method has little interference with the maps, which improves the usability of the watermarked vector map.
Zhenyuan Jia - One of the best experts on this subject based on the ideXlab platform.
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Effect of Geometric Feature and cutting direction on variation of force and vibration in high-speed milling of TC4 curved surface
The International Journal of Advanced Manufacturing Technology, 2017Co-Authors: Zhenyuan Jia, Zhang Ning, Fuji WangAbstract:Curved surface parts with difficult-to-machine material are widely used in the industrial applications, and the three-axis NC machining with ball-end cutter is the commonly adopted method for some simple curved surface parts machining due to its high stiffness and simple operation. Due to the Geometric Feature variation for the curved surface and the bigger cutting force of the difficult-to-machine material, the cutting area and the cutting speed are changing all the time along the determined tool-path which results in a severe variation of cutting force and cutting vibration in high-speed milling process. This may not only affect the machining quality but also the tool life. In this way, the effect of the Geometric Feature of the curved surface and the cutting direction along the tool-path on the variation of force and vibration in high-speed milling of TC4 curved surface is studied. The experimental results show that both the cutting force and the cutting vibration increase when the tool-path curvature radius increases, while the cutting force decreases when the effective cutting radius increases and the cutting vibration will increase many times when the cutting area increases. Besides, the uphill cutting method for curved surface machining can obtain good machining quality and prolong milling cutter life. It can provide guidance for machining strategy selection especially for the cutting direction selection in the tool-path planning. The achievement, that can make both cutting force and cutting vibration small based on the Geometric Feature and the cutting direction, provides guidance for the machining planning of TC4 curved surface, which leads to improving machining quality and reducing tool wear.
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Quick segmentation for complex curved surface with local Geometric Feature based on IGES and Open CASCADE
Advances in Engineering Software, 2015Co-Authors: Fuji Wang, Xu Qiang, Zhenyuan Jia, Yan-yu YangAbstract:A segmentation system for efficient machining of complex curved surface is proposed.Feature size of a surface patch is defined by its boundary information.Surface patches with different Feature sizes will be processed by different parameters.Experiment shows efficiency is increased by 28.18%.Estimations of other models predict efficiency can be increased by 20.14% and 12.33%. Complex curved surface parts with local Geometric Feature are usually critical parts in high-end equipments. However, the processing for this kind of parts is usually difficult or inefficient due to the adoption of difficult-to-machine material and special structure. Current approaches cannot satisfy the rapid development of high-end equipments. Due to the existence of the local Geometric Feature for the parts, processing such parts with constant machining parameters is less applicative, restricting the improvement of machining efficiency. By separating the local Geometric Feature and generating tool path for the local Geometric Feature and the remaining processing area separately, the more efficient machining with variable machining parameters will be obtained for the complex curved surface with local Geometric Feature. In this way, the quick segmentation for the complex curved surface with local Geometric Feature is of great importance to the NC machining with variable machining parameters for this kind of parts, and a quick segmentation system is developed based on Initial Graphics Exchange Specification (IGES) and Open CASCADE (OCC) platform in this study. The complex curved surface model in IGES format is firstly imported into the system and then trimmed into independent surface patches. After computing the Feature size of each surface patch, the segmentation for the complex curved surface is achieved by sorting and classifying the surface patches according to their Feature sizes. Taking the whole impeller with small splitter blades for an example, the experimental result shows that the segmentation of small splitter blades from the whole impeller is successful and a serialized processing program could be generated, and then the whole impeller could be machined precisely and efficiently with NC equipment. In the machining experiment, it is proved that the machining with various machining parameters can improve the efficiency by 28.18% in the comparison experiment, 20.14% and 12.33% in the estimation. The research provides an important foundation for the high quality and more efficient machining of the complex curved surface with local Geometric Feature.
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Feed speed scheduling method for parts with rapidly varied Geometric Feature based on drive constraint of NC machine tool
International Journal of Machine Tools and Manufacture, 2014Co-Authors: Zhenyuan Jia, Ling Wang, Kai Zhao, Wei LiuAbstract:Abstract As the existence of rapidly varied Geometric Feature and during the NC manufacturing process of this kind of parts, the actual moving speed of the workbench of the NC machine tool cannot reach the feed speed set in the NC program timely due to the drive constraint of NC machine tool. Furthermore, the machine tool would vibrate violently with the drive constraint when employing the constant machining parameter to process the parts with rapidly varied Geometric Feature, which seriously restricts the improvement of processing this kind of parts with high quality and high efficiency. In order to manufacture such parts with high quality and high efficiency, a sub-regional processing method with variable machining parameters is proposed. Firstly, the generation mechanism of the machining error is studied, and its mathematical model is built. Then the change rule of the machining error influenced by the curvature and the NC programmed feed speed is found out. Finally, taking the drive constraint and the machining error requirement into account, the relationship between the programmed feed speed and the curvature is established, and the corresponding programmed feed speeds to different curvatures are obtained. Taking the NC machining of the edge line of spiral microstrip antenna, which is an equiangular spiral, for example, the experiment results show that compared with the machining result with constant machining parameter, the maximum machining error of the sub-regional processing method with variable machining parameters decreases by 35.51% and the average value of the machining error decreases by 46.65%. For another example, the clover rose line is machined and the processing quality is also improved. This study proves that the method distributing the programmed feed speeds based on the curvature variation can improve the machining precision and ensure processing efficiency, and provides an effective method to manufacture parts with rapidly varied Geometric Feature.
Erhu Zhang - One of the best experts on this subject based on the ideXlab platform.
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Local Surface Geometric Feature for 3D human action recognition
Neurocomputing, 2016Co-Authors: Erhu Zhang, Wanjun Chen, Zhuomin Zhang, Yan ZhangAbstract:This paper presents a novel Local Surface Geometric Feature (LSGF) for human action recognition from video sequences captured by a depth camera. The LSGF is extracted from each skeleton joint in point cloud space to capture the static appearance and pose cues, which includes joint position, normal, and local curvature. A temporal pyramid of covariance matrix is exploited to model both pairwise relations of Features instead of Features themselves and the temporal evolution. Finally, Fisher vector encoding is imported as a global representation for a video sequence and SVM classifier is used for classification. In the extensive experiments, we achieve classification results superior to most of previous published results on three public benchmark datasets, i.e., MSR-Action3D, MSR DailyActivity3D, and UTKinect Action.