This paper presents an efficient technique for processing of 3D meshed surfaces via spherical wavelets. More specifically, an input 3D mesh is firstly transformed into a spherical vector signal by a fast low distortio...This paper presents an efficient technique for processing of 3D meshed surfaces via spherical wavelets. More specifically, an input 3D mesh is firstly transformed into a spherical vector signal by a fast low distortion spherical parameterization approach based on symmetry analysis of 3D meshes. This signal is then sampled on the sphere with the help of an adaptive sampling scheme. Finally, the sampled signal is transformed into the wavelet domain according to spherical wavelet transform where many 3D mesh processing operations can be implemented such as smoothing, enhancement, compression, and so on. Our main contribution lies in incorporating a fast low distortion spherical parameterization approach and an adaptive sampling scheme into the frame for pro- cessing 3D meshed surfaces by spherical wavelets, which can handle surfaces with complex shapes. A number of experimental ex- amples demonstrate that our algorithm is robust and efficient.展开更多
无线Mesh网络(Wireless Mesh network, WMN)中,链路拥塞会导致较长的传输时延和排队时间,因此将链路负载均衡与服务质量结合起来一直是研究热点.本文针对多目标路由优化管理的关键问题,将路由问题表述为整数线性规划(Integer linear pro...无线Mesh网络(Wireless Mesh network, WMN)中,链路拥塞会导致较长的传输时延和排队时间,因此将链路负载均衡与服务质量结合起来一直是研究热点.本文针对多目标路由优化管理的关键问题,将路由问题表述为整数线性规划(Integer linear programming, ILP)模型,并将无线Mesh网络与软件定义网络(Software defined network, SDN)结合,设计了适应于SD-WMN架构的多目标函数、约束条件以及整体的网络优化模型,此外,由于该整数线性规划模型是NP完全的,本文将改进的人工蜂群的启发式优化算法引入到路由优化算法中,以获得源节点和目的节点之间传输流量的理想路径.本文所提出方法在Mininet网络模拟工具中的仿真结果证明了该算法的有效性,与OSPF、SDNR以及遗传蚁群优化(G-ACO)相比,所提出方法在丢包率、往返时间和负载均衡方面均有不错的改善.展开更多
This paper proposes the design of a novel DC current flow controller(CFC)and evaluates the control performance of balancing and regulating the DC branch currents using the DC CFC in a meshed multi-terminal HVDC(MTDC)g...This paper proposes the design of a novel DC current flow controller(CFC)and evaluates the control performance of balancing and regulating the DC branch currents using the DC CFC in a meshed multi-terminal HVDC(MTDC)grid.The DC CFC consists of two identical full bridge DC-DC converters with the capacitors of the two converters being connected in parallel.The scalability of the DC CFC is easily achievable due to the identical bridge converter topology;the cost of this DC CFC is also relatively low due to its simple physical structure and low voltage ratings.The control performance of the DC CFC is tested on a meshed 3-terminal(3-T)HVDC grid,which is based on modular multilevel converters(MMC).The DC branch current control in the meshed MTDC grid is achieved using the proposed control strategy of the DC CFC,and is verified through case studies on the real-time digital simulator(RTDS).展开更多
Controllability of DC current/power flow is essentialin multi-terminal HVDC (MTDC) grids, particularly for theMTDC grids in a meshed topology. In this paper, consideringmeshed MTDC (M2TDC) grids with the installation ...Controllability of DC current/power flow is essentialin multi-terminal HVDC (MTDC) grids, particularly for theMTDC grids in a meshed topology. In this paper, consideringmeshed MTDC (M2TDC) grids with the installation of twoline/multi-lineDC current flow controllers (CFCs), a small-signalmodel of the DC CFCs integrated M2TDC grids is derived,studying the impact of the power losses of the DC CFC andtheir influence on the analysis of energy exchanges. The systemstability analysis is analysed using the Nyquist diagram, which ismore suitable for analyzing complex nonlinear systems with morecompact and reliable indicators of stability in comparison withgain/phase margins shown in the Bode diagram. In addition, aselection method of the interconnected capacitor of the DC CFCis proposed under different operating conditions. The impact ofthe switching frequencies of the DC CFC on the control ranges ofthe DC current flows is analyzed. The effectiveness of the Nyquistanalysis and the capacitance selection method is verified bysimulation studies using PSCAD/EMTDC. The obtained control ranges of the DC CFC with different switching frequenciesand capacitances would be useful for practical engineeringapplications.展开更多
The paper considers application of artificial neural networks(ANNs)for fast numerical evaluation of a residual impactor velocity for a family of perforated PMMA(Polymethylmethacrylate)targets.The ANN models were train...The paper considers application of artificial neural networks(ANNs)for fast numerical evaluation of a residual impactor velocity for a family of perforated PMMA(Polymethylmethacrylate)targets.The ANN models were trained using sets of numerical results on impact of PMMA plates obtained via dynamic FEM coupled with incubation time fracture criterion.The developed approach makes it possible to evaluate the impact strength of a particular target configuration without complicated FEM calculations which require considerable computational resources.Moreover,it is shown that the ANN models are able to predict results for the configurations which cannot be processed using the developed FEM routine due to numerical instabilities and errors:the trained neural network uses information from successful computations to obtain results for the problematic cases.A simple static problem of a perforated plate deformation is discussed prior to the impact problem and preferable ANN architectures are presented for both problems.Some insight into the perforation pattern optimization using a genetic algorithm coupled with the ANN is also made and optimized perforation patterns which theoretically enhance the target impact strength are constructed.展开更多
The Blade Altering Toolbox(BAT)described in this paper is a tool designed for fast reconstruction of an altered blade geometry for design optimization purposes.The BAT algorithm is capable of twisting a given rotor’s...The Blade Altering Toolbox(BAT)described in this paper is a tool designed for fast reconstruction of an altered blade geometry for design optimization purposes.The BAT algorithm is capable of twisting a given rotor’s angle of attack and stretching the chord length along the span of the rotor.Several test cases were run using the BAT’s algorithm.The BAT code’s twisting,stretching,and mesh reconstruction capabilities proved to be able to handle reasonably large geometric alterations to a provided input rotor geometry.The test examples showed that the toolbox’s algorithm could handle any stretching of the blade’s chord as long as the blade remained within the original bounds of the unaltered mesh.The algorithm appears to fail when the net twist angle applied the geometry exceeds approximately 30 degrees,however this limitation is dependent on the initial geometry and other input parameters.Overall,the algorithm is a very powerful tool for automating a design optimization procedure.展开更多
基金Supported by the National Natural Science Foundation of China(No.61173102)the NSFC Guangdong Joint Fund(No.U0935004)+2 种基金the Fundamental Research Funds for the Central Universities(No.DUT11SX08)the Opening Foundation of Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education of China(No.93K172012K02)the Doctor Research Start-up Fund of North East Dian Li university(No.BSJXM-200912)
文摘This paper presents an efficient technique for processing of 3D meshed surfaces via spherical wavelets. More specifically, an input 3D mesh is firstly transformed into a spherical vector signal by a fast low distortion spherical parameterization approach based on symmetry analysis of 3D meshes. This signal is then sampled on the sphere with the help of an adaptive sampling scheme. Finally, the sampled signal is transformed into the wavelet domain according to spherical wavelet transform where many 3D mesh processing operations can be implemented such as smoothing, enhancement, compression, and so on. Our main contribution lies in incorporating a fast low distortion spherical parameterization approach and an adaptive sampling scheme into the frame for pro- cessing 3D meshed surfaces by spherical wavelets, which can handle surfaces with complex shapes. A number of experimental ex- amples demonstrate that our algorithm is robust and efficient.
文摘无线Mesh网络(Wireless Mesh network, WMN)中,链路拥塞会导致较长的传输时延和排队时间,因此将链路负载均衡与服务质量结合起来一直是研究热点.本文针对多目标路由优化管理的关键问题,将路由问题表述为整数线性规划(Integer linear programming, ILP)模型,并将无线Mesh网络与软件定义网络(Software defined network, SDN)结合,设计了适应于SD-WMN架构的多目标函数、约束条件以及整体的网络优化模型,此外,由于该整数线性规划模型是NP完全的,本文将改进的人工蜂群的启发式优化算法引入到路由优化算法中,以获得源节点和目的节点之间传输流量的理想路径.本文所提出方法在Mininet网络模拟工具中的仿真结果证明了该算法的有效性,与OSPF、SDNR以及遗传蚁群优化(G-ACO)相比,所提出方法在丢包率、往返时间和负载均衡方面均有不错的改善.
基金supported by UK-China Smart Grid Project ERIFT via UK EPSRC,University of Birmingham SiGuang Li Scholarship and China Scholarship Council。
文摘This paper proposes the design of a novel DC current flow controller(CFC)and evaluates the control performance of balancing and regulating the DC branch currents using the DC CFC in a meshed multi-terminal HVDC(MTDC)grid.The DC CFC consists of two identical full bridge DC-DC converters with the capacitors of the two converters being connected in parallel.The scalability of the DC CFC is easily achievable due to the identical bridge converter topology;the cost of this DC CFC is also relatively low due to its simple physical structure and low voltage ratings.The control performance of the DC CFC is tested on a meshed 3-terminal(3-T)HVDC grid,which is based on modular multilevel converters(MMC).The DC branch current control in the meshed MTDC grid is achieved using the proposed control strategy of the DC CFC,and is verified through case studies on the real-time digital simulator(RTDS).
基金National Natural Science Foundation of China under Grant 51807091Natural Science Foundation of Jiangsu Province BK20180478+1 种基金the China Postdoctoral Science Foundation under Grant 2019M661846EPSRC under Grant EP/N032888/1.
文摘Controllability of DC current/power flow is essentialin multi-terminal HVDC (MTDC) grids, particularly for theMTDC grids in a meshed topology. In this paper, consideringmeshed MTDC (M2TDC) grids with the installation of twoline/multi-lineDC current flow controllers (CFCs), a small-signalmodel of the DC CFCs integrated M2TDC grids is derived,studying the impact of the power losses of the DC CFC andtheir influence on the analysis of energy exchanges. The systemstability analysis is analysed using the Nyquist diagram, which ismore suitable for analyzing complex nonlinear systems with morecompact and reliable indicators of stability in comparison withgain/phase margins shown in the Bode diagram. In addition, aselection method of the interconnected capacitor of the DC CFCis proposed under different operating conditions. The impact ofthe switching frequencies of the DC CFC on the control ranges ofthe DC current flows is analyzed. The effectiveness of the Nyquistanalysis and the capacitance selection method is verified bysimulation studies using PSCAD/EMTDC. The obtained control ranges of the DC CFC with different switching frequenciesand capacitances would be useful for practical engineeringapplications.
基金Russian Science Foundation[grant number 22-71-10019].
文摘The paper considers application of artificial neural networks(ANNs)for fast numerical evaluation of a residual impactor velocity for a family of perforated PMMA(Polymethylmethacrylate)targets.The ANN models were trained using sets of numerical results on impact of PMMA plates obtained via dynamic FEM coupled with incubation time fracture criterion.The developed approach makes it possible to evaluate the impact strength of a particular target configuration without complicated FEM calculations which require considerable computational resources.Moreover,it is shown that the ANN models are able to predict results for the configurations which cannot be processed using the developed FEM routine due to numerical instabilities and errors:the trained neural network uses information from successful computations to obtain results for the problematic cases.A simple static problem of a perforated plate deformation is discussed prior to the impact problem and preferable ANN architectures are presented for both problems.Some insight into the perforation pattern optimization using a genetic algorithm coupled with the ANN is also made and optimized perforation patterns which theoretically enhance the target impact strength are constructed.
基金NASA Glenn Research Center,Award Number,GRT00060658NSF IUCRC Smart Vehicle Concept Research Seed Program,No Award Number Provided.
文摘The Blade Altering Toolbox(BAT)described in this paper is a tool designed for fast reconstruction of an altered blade geometry for design optimization purposes.The BAT algorithm is capable of twisting a given rotor’s angle of attack and stretching the chord length along the span of the rotor.Several test cases were run using the BAT’s algorithm.The BAT code’s twisting,stretching,and mesh reconstruction capabilities proved to be able to handle reasonably large geometric alterations to a provided input rotor geometry.The test examples showed that the toolbox’s algorithm could handle any stretching of the blade’s chord as long as the blade remained within the original bounds of the unaltered mesh.The algorithm appears to fail when the net twist angle applied the geometry exceeds approximately 30 degrees,however this limitation is dependent on the initial geometry and other input parameters.Overall,the algorithm is a very powerful tool for automating a design optimization procedure.