在水平层状介质模型、平面波源的情况下,通过把模型离散为旅行时相等的小薄层,可以把薄层间的波场递推关系式写成 z 变换的形式。当介质不含吸收时,可将以 z 变换形式表达的波场递推关系式改写为褶积关系式,从而可以在时间域采用褶积形...在水平层状介质模型、平面波源的情况下,通过把模型离散为旅行时相等的小薄层,可以把薄层间的波场递推关系式写成 z 变换的形式。当介质不含吸收时,可将以 z 变换形式表达的波场递推关系式改写为褶积关系式,从而可以在时间域采用褶积形式计算合成记录。与在频率域计算相比,本文的方法更加简便,运算速度快,所用计算机内存更少。该算法亦适用于计算地面一维合成记录。展开更多
We show how to apply convolution quadrature(CQ)to approximate the time domain electric field integral equation(EFIE)for electromagnetic scattering.By a suitable choice of CQ,we prove that the method is unconditionally...We show how to apply convolution quadrature(CQ)to approximate the time domain electric field integral equation(EFIE)for electromagnetic scattering.By a suitable choice of CQ,we prove that the method is unconditionally stable and has the optimal order of convergence.Surprisingly,the resulting semi discrete EFIE is dispersive and dissipative,and we analyze this phenomena.Finally,we present numerical results supporting and extending our convergence analysis.展开更多
Two algorithms for dwell time adjustment are evaluated under the same polishing conditions that involve tool and work distributions.Both methods are based on Preston’s hypothesis.The first method is a convolution alg...Two algorithms for dwell time adjustment are evaluated under the same polishing conditions that involve tool and work distributions.Both methods are based on Preston’s hypothesis.The first method is a convolution algorithm based on the Fast Fourier Transform.The second is an iterative method based on a constraint problem,extended from a one-dimensional formulation to address a two-dimensional problem.Both methods are investigated for their computational cost,accuracy,and polishing shapes.The convolution method has high accuracy and high speed.The constraint problem on the other hand is slow even when it requires larger memory and thus is more costly.However,unlike the other case a negative region in the polishing shape is not predicted here.Furthermore,new techniques are devised by combining the two methods.展开更多
提出一种仅由角速度来计算功角对故障切除时间灵敏度(sensitivity of power angle to fault clearing time,SPAFCT)的方法。通过对不同详略程度发电机模型的分析,导出SPAFCT与角速度轨迹之间的关系,由此可实现根据轨迹计算SPAFCT。研究...提出一种仅由角速度来计算功角对故障切除时间灵敏度(sensitivity of power angle to fault clearing time,SPAFCT)的方法。通过对不同详略程度发电机模型的分析,导出SPAFCT与角速度轨迹之间的关系,由此可实现根据轨迹计算SPAFCT。研究表明,SPAFCT与角速度轨迹之间的关系不随模型详略程度(模型阶数)而改变,说明在由角速度轨迹计算SPAFCT时不会受到系统模型参数误差的影响。单机系统和10机39节点系统的算例表明,所提方法具有较高的计算精度且计算简便。算例还表明SPAFCT中蕴含了丰富的电力系统暂态稳定裕度的信息。展开更多
A new computational method for solving the fifth order Korteweg-de Vries (fKdV) equation is proposed. The nonlinear partial differential equation is discretized in space using the discrete singular convolution (DSC) s...A new computational method for solving the fifth order Korteweg-de Vries (fKdV) equation is proposed. The nonlinear partial differential equation is discretized in space using the discrete singular convolution (DSC) scheme and an exponential time integration scheme combined with the best rational approximations based on the Carathéodory-Fejér procedure for time discretization. We check several numerical results of our approach against available analytical solutions. In addition, we computed the conservation laws of the fKdV equation. We find that the DSC approach is a very accurate, efficient and reliable method for solving nonlinear partial differential equations.展开更多
The dynamics of two non-coupled qubits independently interacting with their reservoirs is solved by the time convolutionless projection operator method. We study two-qubit quantum correlation dynamics for two differen...The dynamics of two non-coupled qubits independently interacting with their reservoirs is solved by the time convolutionless projection operator method. We study two-qubit quantum correlation dynamics for two different types of spectral densities, which are a Lorentzian distribution and an Ohmic spectral density with a Lorentzian–Drude cutoff function. For two qubits initially prepared in the initial Bell state, quantum discord can keep longer time and reach larger values in nonMarkovian reservoirs for the first spectral distribution or by reducing the cutoff frequency for the second case. For the initial Bell-like state, the dynamic behaviors of quantum discord and entanglement are compared. The results show that a long time of quantum correlation can be obtained by adjusting some parameters in experiment and further confirm that the discord can capture quantum correlation in addition to entanglement.展开更多
文摘在水平层状介质模型、平面波源的情况下,通过把模型离散为旅行时相等的小薄层,可以把薄层间的波场递推关系式写成 z 变换的形式。当介质不含吸收时,可将以 z 变换形式表达的波场递推关系式改写为褶积关系式,从而可以在时间域采用褶积形式计算合成记录。与在频率域计算相比,本文的方法更加简便,运算速度快,所用计算机内存更少。该算法亦适用于计算地面一维合成记录。
基金funding this research under grant number DMS-0811104.
文摘We show how to apply convolution quadrature(CQ)to approximate the time domain electric field integral equation(EFIE)for electromagnetic scattering.By a suitable choice of CQ,we prove that the method is unconditionally stable and has the optimal order of convergence.Surprisingly,the resulting semi discrete EFIE is dispersive and dissipative,and we analyze this phenomena.Finally,we present numerical results supporting and extending our convergence analysis.
文摘Two algorithms for dwell time adjustment are evaluated under the same polishing conditions that involve tool and work distributions.Both methods are based on Preston’s hypothesis.The first method is a convolution algorithm based on the Fast Fourier Transform.The second is an iterative method based on a constraint problem,extended from a one-dimensional formulation to address a two-dimensional problem.Both methods are investigated for their computational cost,accuracy,and polishing shapes.The convolution method has high accuracy and high speed.The constraint problem on the other hand is slow even when it requires larger memory and thus is more costly.However,unlike the other case a negative region in the polishing shape is not predicted here.Furthermore,new techniques are devised by combining the two methods.
文摘提出一种仅由角速度来计算功角对故障切除时间灵敏度(sensitivity of power angle to fault clearing time,SPAFCT)的方法。通过对不同详略程度发电机模型的分析,导出SPAFCT与角速度轨迹之间的关系,由此可实现根据轨迹计算SPAFCT。研究表明,SPAFCT与角速度轨迹之间的关系不随模型详略程度(模型阶数)而改变,说明在由角速度轨迹计算SPAFCT时不会受到系统模型参数误差的影响。单机系统和10机39节点系统的算例表明,所提方法具有较高的计算精度且计算简便。算例还表明SPAFCT中蕴含了丰富的电力系统暂态稳定裕度的信息。
文摘A new computational method for solving the fifth order Korteweg-de Vries (fKdV) equation is proposed. The nonlinear partial differential equation is discretized in space using the discrete singular convolution (DSC) scheme and an exponential time integration scheme combined with the best rational approximations based on the Carathéodory-Fejér procedure for time discretization. We check several numerical results of our approach against available analytical solutions. In addition, we computed the conservation laws of the fKdV equation. We find that the DSC approach is a very accurate, efficient and reliable method for solving nonlinear partial differential equations.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11264011 and 11104113)the Natural Science Foundation of Hunan Province, China (Grant Nos. 13JJ6059 and 11JJ6007)the Natural Science Foundation of Education Department of Hunan Province, China (GrantNo. 11C1057)
文摘The dynamics of two non-coupled qubits independently interacting with their reservoirs is solved by the time convolutionless projection operator method. We study two-qubit quantum correlation dynamics for two different types of spectral densities, which are a Lorentzian distribution and an Ohmic spectral density with a Lorentzian–Drude cutoff function. For two qubits initially prepared in the initial Bell state, quantum discord can keep longer time and reach larger values in nonMarkovian reservoirs for the first spectral distribution or by reducing the cutoff frequency for the second case. For the initial Bell-like state, the dynamic behaviors of quantum discord and entanglement are compared. The results show that a long time of quantum correlation can be obtained by adjusting some parameters in experiment and further confirm that the discord can capture quantum correlation in addition to entanglement.
