在利用均匀网格时域有限差分法(finite-difference time domain,FDTD)计算地闪回击电磁脉冲时,空间步长选取较大会导致计算结果中后期出现震荡,所以为了计算结果的准确必须采用较小的空间步长,导致计算效率低、内存需求大。为了解决这...在利用均匀网格时域有限差分法(finite-difference time domain,FDTD)计算地闪回击电磁脉冲时,空间步长选取较大会导致计算结果中后期出现震荡,所以为了计算结果的准确必须采用较小的空间步长,导致计算效率低、内存需求大。为了解决这一问题,提出利用惠更斯亚网格技术改进计算模型,改进后的模型可以实现在距离雷电通道近、高频分量多的区域采用较小的空间步长,其余区域仍采用较大的空间步长,从而以较高的计算效率消除计算结果中后期的震荡。首先,分析了空间步长对均匀网格FDTD法的各个场分量计算结果的影响;其次,通过与均匀网格FDTD计算结果对比,深入研究了改进模型对水平电场中后期震荡的消除作用。结果表明:随着步长的增大,水平电场中后期震荡剧烈;在不同地面电导率、地闪回击速度下,改进后的计算模型均能以较高的计算效率得到准确的、无震荡的计算结果。展开更多
The techniques to forecast available parking space(APS) are indispensable components for parking guidance systems(PGS). According to the data collected in Newcastle upon Tyne, England, the changing characteristics of ...The techniques to forecast available parking space(APS) are indispensable components for parking guidance systems(PGS). According to the data collected in Newcastle upon Tyne, England, the changing characteristics of APS were studied. Thereafter, aiming to build up a multi-step APS forecasting model that provides richer information than a conventional one-step model, the largest Lyapunov exponents(largest LEs) method was introduced into PGS. By experimental tests conducted using the same dataset, its prediction performance was compared with traditional wavelet neural network(WNN) method in both one-step and multi-step processes. Based on the results, a new multi-step forecasting model called WNN-LE method was proposed, where WNN, which enjoys a more accurate performance along with a better learning ability in short-term forecasting, was applied in the early forecast steps while the Lyapunov exponent prediction method in the latter steps precisely reflect the chaotic feature in latter forecast period. The MSE of APS forecasting for one hour time period can be reduced from 83.1 to 27.1(in a parking building with 492 berths) by using largest LEs method instead of WNN and further reduced to 19.0 by conducted the new method.展开更多
A new method for edge detection based on directional space is proposed.The principle is that:firstly,the directional differential space is set up in which the ridge edge pixels and valley edge pixels are abstracted wi...A new method for edge detection based on directional space is proposed.The principle is that:firstly,the directional differential space is set up in which the ridge edge pixels and valley edge pixels are abstracted with the help of the method of logical judgments along the direction of differential function,forming a directional roof edge map;secondly,step edge pixels are abstracted between the neighboring directional ridge edge and directional valley edge along the direction of differential function;finally,the ridge edge map,valley edge map and step edge map gained along different directions are combined into corresponding ridge edge map,valley edge map and step edge map.This method is different from classical algorithms in which the gray differential values of the mutual vertical direction are combined into one gradient value.The experiment of edge detection is made for the images of nature scenery,human body and accumulative raw material,whose result is compared with the one of classical algorithms and showing the robustness of the proposed method.展开更多
基于美国Hopkins大学Gregory S. Chirikjian等人提出的永磁球形步进电动机模型,提出了一种检测空间中转子位置的方法。在转子球面上进行随机编码,采用光电传感器对转子的位置进行识别。在这种编码规则下,对传感器检测的分辨率进行了研究...基于美国Hopkins大学Gregory S. Chirikjian等人提出的永磁球形步进电动机模型,提出了一种检测空间中转子位置的方法。在转子球面上进行随机编码,采用光电传感器对转子的位置进行识别。在这种编码规则下,对传感器检测的分辨率进行了研究,建立状态空间作为表述问题的数据结构,使用图搜索方式进行单点搜索,以当前的分辨率精度得出空间中转子的位置,为以后球形电动机的闭环控制奠定了基础。展开更多
A biped walking robot should be able to keep balance even in the presence of disturbing forces. This paper presents a step strategy concept of biped walking robot that is stabilized by using reaction null space method...A biped walking robot should be able to keep balance even in the presence of disturbing forces. This paper presents a step strategy concept of biped walking robot that is stabilized by using reaction null space method. The called ＂step strategy＂ can be modeled by means of the reaction null space method that introduced earlier to tackle dynamic interaction problems of free-floating robots, or moving base robots in general. 6-DOF biped robot model simulations are used to confirm the validity.展开更多
In this paper,we have considered the multi-dimensional space fractional diffusion equations with variable coefficients.The fractional operators(derivative/integral)are used based on the Caputo definition.This study pr...In this paper,we have considered the multi-dimensional space fractional diffusion equations with variable coefficients.The fractional operators(derivative/integral)are used based on the Caputo definition.This study provides an analytical approach to determine the analytical solution of the considered problems with the help of the two-step Adomian decomposition method(TSADM).Moreover,new results have been obtained for the existence and uniqueness of a solution by using the Banach contraction principle and a fixed point theorem.We have extended the dimension of the space fractional diffusion equations with variable coefficients into multi-dimensions.Finally,the generalized problems with two different types of the forcing term have been included demonstrating the applicability and high efficiency of the TSADM in comparison to other existing numerical methods.The diffusion coefficients do not require to satisfy any certain conditions/restrictions for using the TSADM.There are no restrictions imposed on the problems for diffusion coefficients,and a similar procedures of the TSADM has followed to the obtained analytical solution for the multi-dimensional space fractional diffusion equations with variable coefficients.展开更多
This article introduces the computational analytical approach to solve the m-dimensional space-time variable Caputo fractional order advection–dispersion equation with the Dirichlet boundary using the two-step Adomia...This article introduces the computational analytical approach to solve the m-dimensional space-time variable Caputo fractional order advection–dispersion equation with the Dirichlet boundary using the two-step Adomian decomposition method and obtain the exact solution in just one iteration.Moreover,with the help of fixed point theory,we study the existence and uniqueness conditions for the positive solution and prove some new results.Also,obtain the Ulam–Hyers stabilities for the proposed problem.Two gen-eralized examples are considered to show the method’s applicability and compared with other existing numerical methods.The present method performs exceptionally well in terms of efficiency and simplicity.Further,we solved both examples using the two most well-known numerical methods and compared them with the TSADM solution.展开更多
文摘在利用均匀网格时域有限差分法(finite-difference time domain,FDTD)计算地闪回击电磁脉冲时,空间步长选取较大会导致计算结果中后期出现震荡,所以为了计算结果的准确必须采用较小的空间步长,导致计算效率低、内存需求大。为了解决这一问题,提出利用惠更斯亚网格技术改进计算模型,改进后的模型可以实现在距离雷电通道近、高频分量多的区域采用较小的空间步长,其余区域仍采用较大的空间步长,从而以较高的计算效率消除计算结果中后期的震荡。首先,分析了空间步长对均匀网格FDTD法的各个场分量计算结果的影响;其次,通过与均匀网格FDTD计算结果对比,深入研究了改进模型对水平电场中后期震荡的消除作用。结果表明:随着步长的增大,水平电场中后期震荡剧烈;在不同地面电导率、地闪回击速度下,改进后的计算模型均能以较高的计算效率得到准确的、无震荡的计算结果。
基金Project(2012CB725402)supported by the National Key Basic Research Program of ChinaProjects(51338003,50908051)supported by the National Natural Science Foundation of China
文摘The techniques to forecast available parking space(APS) are indispensable components for parking guidance systems(PGS). According to the data collected in Newcastle upon Tyne, England, the changing characteristics of APS were studied. Thereafter, aiming to build up a multi-step APS forecasting model that provides richer information than a conventional one-step model, the largest Lyapunov exponents(largest LEs) method was introduced into PGS. By experimental tests conducted using the same dataset, its prediction performance was compared with traditional wavelet neural network(WNN) method in both one-step and multi-step processes. Based on the results, a new multi-step forecasting model called WNN-LE method was proposed, where WNN, which enjoys a more accurate performance along with a better learning ability in short-term forecasting, was applied in the early forecast steps while the Lyapunov exponent prediction method in the latter steps precisely reflect the chaotic feature in latter forecast period. The MSE of APS forecasting for one hour time period can be reduced from 83.1 to 27.1(in a parking building with 492 berths) by using largest LEs method instead of WNN and further reduced to 19.0 by conducted the new method.
基金supported by the Science and Technology Foundation of Liaoning Province(No.2001101022).
文摘A new method for edge detection based on directional space is proposed.The principle is that:firstly,the directional differential space is set up in which the ridge edge pixels and valley edge pixels are abstracted with the help of the method of logical judgments along the direction of differential function,forming a directional roof edge map;secondly,step edge pixels are abstracted between the neighboring directional ridge edge and directional valley edge along the direction of differential function;finally,the ridge edge map,valley edge map and step edge map gained along different directions are combined into corresponding ridge edge map,valley edge map and step edge map.This method is different from classical algorithms in which the gray differential values of the mutual vertical direction are combined into one gradient value.The experiment of edge detection is made for the images of nature scenery,human body and accumulative raw material,whose result is compared with the one of classical algorithms and showing the robustness of the proposed method.
文摘基于美国Hopkins大学Gregory S. Chirikjian等人提出的永磁球形步进电动机模型,提出了一种检测空间中转子位置的方法。在转子球面上进行随机编码,采用光电传感器对转子的位置进行识别。在这种编码规则下,对传感器检测的分辨率进行了研究,建立状态空间作为表述问题的数据结构,使用图搜索方式进行单点搜索,以当前的分辨率精度得出空间中转子的位置,为以后球形电动机的闭环控制奠定了基础。
基金supported by the National Natural Science Foundation of China (No.50675016)the Science and Technology Innovation Fund for the Doctor (No.48030)
文摘A biped walking robot should be able to keep balance even in the presence of disturbing forces. This paper presents a step strategy concept of biped walking robot that is stabilized by using reaction null space method. The called ＂step strategy＂ can be modeled by means of the reaction null space method that introduced earlier to tackle dynamic interaction problems of free-floating robots, or moving base robots in general. 6-DOF biped robot model simulations are used to confirm the validity.
文摘In this paper,we have considered the multi-dimensional space fractional diffusion equations with variable coefficients.The fractional operators(derivative/integral)are used based on the Caputo definition.This study provides an analytical approach to determine the analytical solution of the considered problems with the help of the two-step Adomian decomposition method(TSADM).Moreover,new results have been obtained for the existence and uniqueness of a solution by using the Banach contraction principle and a fixed point theorem.We have extended the dimension of the space fractional diffusion equations with variable coefficients into multi-dimensions.Finally,the generalized problems with two different types of the forcing term have been included demonstrating the applicability and high efficiency of the TSADM in comparison to other existing numerical methods.The diffusion coefficients do not require to satisfy any certain conditions/restrictions for using the TSADM.There are no restrictions imposed on the problems for diffusion coefficients,and a similar procedures of the TSADM has followed to the obtained analytical solution for the multi-dimensional space fractional diffusion equations with variable coefficients.
文摘This article introduces the computational analytical approach to solve the m-dimensional space-time variable Caputo fractional order advection–dispersion equation with the Dirichlet boundary using the two-step Adomian decomposition method and obtain the exact solution in just one iteration.Moreover,with the help of fixed point theory,we study the existence and uniqueness conditions for the positive solution and prove some new results.Also,obtain the Ulam–Hyers stabilities for the proposed problem.Two gen-eralized examples are considered to show the method’s applicability and compared with other existing numerical methods.The present method performs exceptionally well in terms of efficiency and simplicity.Further,we solved both examples using the two most well-known numerical methods and compared them with the TSADM solution.
