In order to increase the evaluating precision of mesh reflection wave, the mesh wave impedance (MWI) is extended to the non-uniform mesh in 1-D and 2-D cases for the first time on the basis of the Yee's positional...In order to increase the evaluating precision of mesh reflection wave, the mesh wave impedance (MWI) is extended to the non-uniform mesh in 1-D and 2-D cases for the first time on the basis of the Yee's positional relation for electromagnetic field components. Lots of characteristics are obtained for different mesh sizes and frequencies. Then the reflection coefficient caused by the non-uniform mesh can be calculated according to the theory of equivalent transmission line. By comparing it with that calculated by MWI in the uniform mesh, it is found that the evaluating error can be largely reduced and is in good agreement with that directly computed by FDTD method. And this extension of MWI can be used in the error analysis of complex mesh.展开更多
传统到达角度(Angle-Of-Arrival,AOA)/接受信号强度指示(Received Signal Strength Indicator,RSSI)混合定位往往需要多个锚节点布设阵列天线以实现高精度定位,为解决在锚节点资源受限下精度较低的问题,提出了一种基于Mesh网络的混合AOA...传统到达角度(Angle-Of-Arrival,AOA)/接受信号强度指示(Received Signal Strength Indicator,RSSI)混合定位往往需要多个锚节点布设阵列天线以实现高精度定位,为解决在锚节点资源受限下精度较低的问题,提出了一种基于Mesh网络的混合AOA/RSSI协作定位方法。仅有中心主锚节点提供AOA角度的情况下,采取最小二乘法对联合真实和虚拟锚节点所对应角度和距离信息进行初步定位;利用未知节点之间的协作通信和测距信息,位置估计问题被转换为无约束非线性优化问题,给予短距离链路更高权重,通过迭代求解最终实现协作定位。仿真结果表明,所提算法在锚节点资源受限情况下有效地提升了定位精度。展开更多
In recent years, finite element analyses have increasingly been utilized for slope stability problems. In comparison to limit equilibrium methods, numerical analyses do not require any definition of the failure mechan...In recent years, finite element analyses have increasingly been utilized for slope stability problems. In comparison to limit equilibrium methods, numerical analyses do not require any definition of the failure mechanism a priori and enable the determination of the safety level more accurately. The paper compares the performances of strength reduction finite element analysis(SRFEA) with finite element limit analysis(FELA), whereby the focus is related to non-associated plasticity. Displacement-based finite element analyses using a strength reduction technique suffer from numerical instabilities when using non-associated plasticity, especially when dealing with high friction angles but moderate dilatancy angles. The FELA on the other hand provides rigorous upper and lower bounds of the factor of safety(FoS) but is restricted to associated flow rules. Suggestions to overcome this problem, proposed by Davis(1968), lead to conservative FoSs; therefore, an enhanced procedure has been investigated. When using the modified approach, both the SRFEA and the FELA provide very similar results. Further studies highlight the advantages of using an adaptive mesh refinement to determine FoSs. Additionally, it is shown that the initial stress field does not affect the FoS when using a Mohr-Coulomb failure criterion.展开更多
In representing automobile parts with mesh in the field of reverse engineering or finite element generation, the mesh reconstruction and data exchanging between different CAD/CAM systems often introduce many invisible...In representing automobile parts with mesh in the field of reverse engineering or finite element generation, the mesh reconstruction and data exchanging between different CAD/CAM systems often introduce many invisible topological and geometrical errors into mesh. These artifacts can cause serious problems in subsequent operations such as finite element analysis, reverse engineering, animation, and simulation. In this study we propose a practical method for repairing topological and geometrical errors on mesh. First, coincident vertices during mesh input are removed, fol- lowed by the identification of non-manifold vertices and edges. The non-manifold vertices are modified, and the facets having non-manifold edges are removed. Finally, faces that have the wrong orientations in the mesh are re-oriented. Experiments show that our methods can eliminate most common mesh errors quickly and effectively. The refined mesh can be properly used in subsequent operations.展开更多
The technology of QoS routing has become a great challenge in Wireless Mesh Networks (WMNs). There exist a lot of literatures on QoS routing in WMNs, but the current algorithms have some deficiencies, such as high com...The technology of QoS routing has become a great challenge in Wireless Mesh Networks (WMNs). There exist a lot of literatures on QoS routing in WMNs, but the current algorithms have some deficiencies, such as high complexity, poor scalability and flexibility. To solve the problems above, a multipath routing algorithm based on traffic prediction (MRATP) is proposed in WMNs. MRATP consists of three modules including an algo-rithm on multipath routing built, a congestion discovery mechanism based on wavelet-neural network and a load balancing algorithm via multipath. Simulation results show that MRATP has some characteristics, such as better scalability, flexibility and robustness. Compared with the current algorithms, MRATP has higher success ratio, lower end to end delay and overhead. So MRATP can guarantee the end to end QoS of WMNs.展开更多
In this article, we report the derivation of high accuracy finite difference method based on arithmetic average discretization for the solution of Un=F(x,u,u′)+∫K(x,s)ds , 0 x s < 1 subject to natural boundary co...In this article, we report the derivation of high accuracy finite difference method based on arithmetic average discretization for the solution of Un=F(x,u,u′)+∫K(x,s)ds , 0 x s < 1 subject to natural boundary conditions on a non-uniform mesh. The proposed variable mesh approximation is directly applicable to the integro-differential equation with singular coefficients. We need not require any special discretization to obtain the solution near the singular point. The convergence analysis of a difference scheme for the diffusion convection equation is briefly discussed. The presented variable mesh strategy is applicable when the internal grid points of the solution space are both even and odd in number as compared to the method discussed by authors in their previous work in which the internal grid points are strictly odd in number. The advantage of using this new variable mesh strategy is highlighted computationally.展开更多
在6G通信系统中,随着天线规模的增大,菲涅尔区逐步扩展,现有的远场通信假设会引入严重的能量扩散,即角度域不再稀疏.近场通信利用球面波前进行建模,其信道模型与用户到达基站的角度和距离相关,在通信的同时可以估计角度和距离,实现通信...在6G通信系统中,随着天线规模的增大,菲涅尔区逐步扩展,现有的远场通信假设会引入严重的能量扩散,即角度域不再稀疏.近场通信利用球面波前进行建模,其信道模型与用户到达基站的角度和距离相关,在通信的同时可以估计角度和距离,实现通信感知一体化(Integrated Sensing And Communication,ISAC).本文针对近场环境下ISAC问题,提出了基于极坐标的近场模型,通过非均匀网格划分将ISAC转化为稀疏估计问题,进而提出基于稀疏贝叶斯学习模型和消息传递算法的ISAC算法,同时完成活跃用户检测、位置感知和通信.此外,所提算法采用差分调制,在通信和感知中无需利用导频,即可实现盲ISAC,有效提升通信系统的频谱效率.仿真结果表明,相对于均匀区域划分和文献现有方法,本文提出的ISAC算法可获得更高的感知精度和误码率性能.展开更多
文摘In order to increase the evaluating precision of mesh reflection wave, the mesh wave impedance (MWI) is extended to the non-uniform mesh in 1-D and 2-D cases for the first time on the basis of the Yee's positional relation for electromagnetic field components. Lots of characteristics are obtained for different mesh sizes and frequencies. Then the reflection coefficient caused by the non-uniform mesh can be calculated according to the theory of equivalent transmission line. By comparing it with that calculated by MWI in the uniform mesh, it is found that the evaluating error can be largely reduced and is in good agreement with that directly computed by FDTD method. And this extension of MWI can be used in the error analysis of complex mesh.
文摘传统到达角度(Angle-Of-Arrival,AOA)/接受信号强度指示(Received Signal Strength Indicator,RSSI)混合定位往往需要多个锚节点布设阵列天线以实现高精度定位,为解决在锚节点资源受限下精度较低的问题,提出了一种基于Mesh网络的混合AOA/RSSI协作定位方法。仅有中心主锚节点提供AOA角度的情况下,采取最小二乘法对联合真实和虚拟锚节点所对应角度和距离信息进行初步定位;利用未知节点之间的协作通信和测距信息,位置估计问题被转换为无约束非线性优化问题,给予短距离链路更高权重,通过迭代求解最终实现协作定位。仿真结果表明,所提算法在锚节点资源受限情况下有效地提升了定位精度。
文摘In recent years, finite element analyses have increasingly been utilized for slope stability problems. In comparison to limit equilibrium methods, numerical analyses do not require any definition of the failure mechanism a priori and enable the determination of the safety level more accurately. The paper compares the performances of strength reduction finite element analysis(SRFEA) with finite element limit analysis(FELA), whereby the focus is related to non-associated plasticity. Displacement-based finite element analyses using a strength reduction technique suffer from numerical instabilities when using non-associated plasticity, especially when dealing with high friction angles but moderate dilatancy angles. The FELA on the other hand provides rigorous upper and lower bounds of the factor of safety(FoS) but is restricted to associated flow rules. Suggestions to overcome this problem, proposed by Davis(1968), lead to conservative FoSs; therefore, an enhanced procedure has been investigated. When using the modified approach, both the SRFEA and the FELA provide very similar results. Further studies highlight the advantages of using an adaptive mesh refinement to determine FoSs. Additionally, it is shown that the initial stress field does not affect the FoS when using a Mohr-Coulomb failure criterion.
文摘In representing automobile parts with mesh in the field of reverse engineering or finite element generation, the mesh reconstruction and data exchanging between different CAD/CAM systems often introduce many invisible topological and geometrical errors into mesh. These artifacts can cause serious problems in subsequent operations such as finite element analysis, reverse engineering, animation, and simulation. In this study we propose a practical method for repairing topological and geometrical errors on mesh. First, coincident vertices during mesh input are removed, fol- lowed by the identification of non-manifold vertices and edges. The non-manifold vertices are modified, and the facets having non-manifold edges are removed. Finally, faces that have the wrong orientations in the mesh are re-oriented. Experiments show that our methods can eliminate most common mesh errors quickly and effectively. The refined mesh can be properly used in subsequent operations.
文摘The technology of QoS routing has become a great challenge in Wireless Mesh Networks (WMNs). There exist a lot of literatures on QoS routing in WMNs, but the current algorithms have some deficiencies, such as high complexity, poor scalability and flexibility. To solve the problems above, a multipath routing algorithm based on traffic prediction (MRATP) is proposed in WMNs. MRATP consists of three modules including an algo-rithm on multipath routing built, a congestion discovery mechanism based on wavelet-neural network and a load balancing algorithm via multipath. Simulation results show that MRATP has some characteristics, such as better scalability, flexibility and robustness. Compared with the current algorithms, MRATP has higher success ratio, lower end to end delay and overhead. So MRATP can guarantee the end to end QoS of WMNs.
文摘In this article, we report the derivation of high accuracy finite difference method based on arithmetic average discretization for the solution of Un=F(x,u,u′)+∫K(x,s)ds , 0 x s < 1 subject to natural boundary conditions on a non-uniform mesh. The proposed variable mesh approximation is directly applicable to the integro-differential equation with singular coefficients. We need not require any special discretization to obtain the solution near the singular point. The convergence analysis of a difference scheme for the diffusion convection equation is briefly discussed. The presented variable mesh strategy is applicable when the internal grid points of the solution space are both even and odd in number as compared to the method discussed by authors in their previous work in which the internal grid points are strictly odd in number. The advantage of using this new variable mesh strategy is highlighted computationally.
文摘在6G通信系统中,随着天线规模的增大,菲涅尔区逐步扩展,现有的远场通信假设会引入严重的能量扩散,即角度域不再稀疏.近场通信利用球面波前进行建模,其信道模型与用户到达基站的角度和距离相关,在通信的同时可以估计角度和距离,实现通信感知一体化(Integrated Sensing And Communication,ISAC).本文针对近场环境下ISAC问题,提出了基于极坐标的近场模型,通过非均匀网格划分将ISAC转化为稀疏估计问题,进而提出基于稀疏贝叶斯学习模型和消息传递算法的ISAC算法,同时完成活跃用户检测、位置感知和通信.此外,所提算法采用差分调制,在通信和感知中无需利用导频,即可实现盲ISAC,有效提升通信系统的频谱效率.仿真结果表明,相对于均匀区域划分和文献现有方法,本文提出的ISAC算法可获得更高的感知精度和误码率性能.
