The piecewise linear recursive convolution （PLRC） finite-different time-domain （FDTD） method greatly improves accuracy over the original recursive convolution （RC） FDTD approach but retains its speed and efficie...The piecewise linear recursive convolution （PLRC） finite-different time-domain （FDTD） method greatly improves accuracy over the original recursive convolution （RC） FDTD approach but retains its speed and efficiency advantages. A PLRC-FDTD formulation for magnetized plasma which incorporates both anisotropy and frequency dispersion at the same time is presented, enabled the transient analysis of magnetized plasma media. The technique is illustrated by numerical simulations the reflection and transmission coefficients through a magnetized plasma layer. The results show that the PLRC-FDTD method has significantly improved the accuracy over the original RC method.展开更多
The absorbing boundary is the key in numerical simulation of borehole radar.Perfect match layer(PML) was chosen as the absorbing boundary in numerical simulation of GPR.But CPML(convolutional perfect match layer) appr...The absorbing boundary is the key in numerical simulation of borehole radar.Perfect match layer(PML) was chosen as the absorbing boundary in numerical simulation of GPR.But CPML(convolutional perfect match layer) approach that we have chosen has the advantage of being media independent.Beginning with the Maxwell equations in a two-dimensional structure,numerical formulas of finite-difference time-domain(FDTD) method with CPML boundary condition for transverse electric(TE) or transverse magnetic(TM) wave are presented in details.Also,there are three models for borehole-GPR simulation.By analyzing the simulation results,the features of targets in GPR are obtained,which can provide a better interpretation of real radar data.The results show that CPML is well suited for the simulation of borehole-GPR.展开更多
SiC MOSFET栅极氧化物附近存在的陷阱缺陷造成其在高温高压场景下出现许多可靠性问题。提出了完整的基于瞬态电流法的陷阱表征方案,结合贝叶斯迭代反卷积算法实现对陷阱位置、时间常数和激活能的表征。基于自建陷阱测试平台在栅极和漏...SiC MOSFET栅极氧化物附近存在的陷阱缺陷造成其在高温高压场景下出现许多可靠性问题。提出了完整的基于瞬态电流法的陷阱表征方案,结合贝叶斯迭代反卷积算法实现对陷阱位置、时间常数和激活能的表征。基于自建陷阱测试平台在栅极和漏极施加不同组合的电学偏置,表征了微秒量级的两个陷阱,其时间常数分别为2×10^(-5)s和2.5×10^(-4)s,并观察到SiC MOSFET中存在同时受栅源电压和漏源电压影响的陷阱,这种现象在沟槽型器件中尤其显著,根据此特性可以分析陷阱的位置。本研究丰富了陷阱表征的信息,为陷阱的定位和表征提供了新的思路。展开更多
在实现e^(N)方法时,需要搜索流场中的不稳定波,并大量求解当地边界层的稳定性问题,因此为高效求解当地边界层的不稳定波参数,提出了一种基于神经网络的线性稳定性分析方法(neural network-based linear stability analysis,NNLSA)。采...在实现e^(N)方法时,需要搜索流场中的不稳定波,并大量求解当地边界层的稳定性问题,因此为高效求解当地边界层的不稳定波参数,提出了一种基于神经网络的线性稳定性分析方法(neural network-based linear stability analysis,NNLSA)。采用卷积神经网络给出最不稳定波频率ω、展向波数β、流向波数αr和增长率σmax的初值对,再通过迭代法计算失稳扰动波的实际空间失稳波数和增长率。使用平板数据集训练神经网络模型,并利用平板和尖锥算例对NNLSA方法的准确性和计算效率进行验证。结果表明:神经网络部分对不稳定波参数的预测结果与线性稳定性理论的计算结果吻合较好;LSA部分可根据神经网络提供的预测值,通过迭代法找到最不稳定波;NN-LSA方法的求解效率较高,求解时间比全局搜索方法约低20~50倍,大大减小了人为因素在计算过程中的影响。本文提出的NN-LSA方法可以实现自动分析边界层流动的线性稳定性,具有一定的应用潜力。展开更多
Time resolution of multipath delay profiles measured by using autocorrelation of pseudonoise (PN) code sequence is generally limited by the chip rate of the PN code sequence. In this paper, we propose a simple method ...Time resolution of multipath delay profiles measured by using autocorrelation of pseudonoise (PN) code sequence is generally limited by the chip rate of the PN code sequence. In this paper, we propose a simple method to improve the time resolution of delay profiles measured by the PN correlation method. Effectiveness of this method is demonstrated by indoor wireless propagation experiments.展开更多
基金The project was supported by the National Natural Science Foundation of China (60471002) and the Jiangxi ProvincialNatural Science Foundation (0412014)
文摘The piecewise linear recursive convolution （PLRC） finite-different time-domain （FDTD） method greatly improves accuracy over the original recursive convolution （RC） FDTD approach but retains its speed and efficiency advantages. A PLRC-FDTD formulation for magnetized plasma which incorporates both anisotropy and frequency dispersion at the same time is presented, enabled the transient analysis of magnetized plasma media. The technique is illustrated by numerical simulations the reflection and transmission coefficients through a magnetized plasma layer. The results show that the PLRC-FDTD method has significantly improved the accuracy over the original RC method.
基金Project(41174061) supported by the National Natural Science Foundation of ChinaProject(2011QNZT011) supported by the Free Exploration Program of Central South University,China
文摘The absorbing boundary is the key in numerical simulation of borehole radar.Perfect match layer(PML) was chosen as the absorbing boundary in numerical simulation of GPR.But CPML(convolutional perfect match layer) approach that we have chosen has the advantage of being media independent.Beginning with the Maxwell equations in a two-dimensional structure,numerical formulas of finite-difference time-domain(FDTD) method with CPML boundary condition for transverse electric(TE) or transverse magnetic(TM) wave are presented in details.Also,there are three models for borehole-GPR simulation.By analyzing the simulation results,the features of targets in GPR are obtained,which can provide a better interpretation of real radar data.The results show that CPML is well suited for the simulation of borehole-GPR.
基金Manuscript received February 13, 2016 accepted December 7, 2016. This work was supported by the National Natural Science Foundation of China （61362001, 61661031）, Jiangxi Province Innovation Projects for Postgraduate Funds （YC2016-S006）, the International Postdoctoral Exchange Fellowship Program, and Jiangxi Advanced Project for Post-Doctoral Research Fund （2014KY02）.
文摘在实现e^(N)方法时,需要搜索流场中的不稳定波,并大量求解当地边界层的稳定性问题,因此为高效求解当地边界层的不稳定波参数,提出了一种基于神经网络的线性稳定性分析方法(neural network-based linear stability analysis,NNLSA)。采用卷积神经网络给出最不稳定波频率ω、展向波数β、流向波数αr和增长率σmax的初值对,再通过迭代法计算失稳扰动波的实际空间失稳波数和增长率。使用平板数据集训练神经网络模型,并利用平板和尖锥算例对NNLSA方法的准确性和计算效率进行验证。结果表明:神经网络部分对不稳定波参数的预测结果与线性稳定性理论的计算结果吻合较好;LSA部分可根据神经网络提供的预测值,通过迭代法找到最不稳定波;NN-LSA方法的求解效率较高,求解时间比全局搜索方法约低20~50倍,大大减小了人为因素在计算过程中的影响。本文提出的NN-LSA方法可以实现自动分析边界层流动的线性稳定性,具有一定的应用潜力。
文摘Time resolution of multipath delay profiles measured by using autocorrelation of pseudonoise (PN) code sequence is generally limited by the chip rate of the PN code sequence. In this paper, we propose a simple method to improve the time resolution of delay profiles measured by the PN correlation method. Effectiveness of this method is demonstrated by indoor wireless propagation experiments.
