In this paper we report a kind of fast-scale instability occurring in the single-ended primary inductance converter （SEPIC） power factor pre-regulator, which is designed to operate in discontinuous conduction mode. ...In this paper we report a kind of fast-scale instability occurring in the single-ended primary inductance converter （SEPIC） power factor pre-regulator, which is designed to operate in discontinuous conduction mode. Main results are given by exact cycle-by-cycle computer simulations as well as theoretical analysis. It is found that the instability phenomenon manifests itself as a fast-scale bifurcation at the switching period, which implies the occurrence of border collision bifurcation, or is related to the transition of the regular operating mode of the SEPIC. According to the theoretical analysis and simulation results, the effects of parameters on system stability, and the locations of the bifurcation points are confirmed. Moreover, the effects of such an instability on power factor and switching stress are also discussed. Finally, the occurrence of the asymmetric bifurcation locations is investigated. The results show that this work provides a convenient means of predicting stability boundaries which can facilitate the selection of the practical parameters.展开更多
A modified slow-fast analysis method is presented for the periodically excited non-autonomous dynamical system with an order gap between the exciting frequency and the natural frequency.By regarding the exciting term ...A modified slow-fast analysis method is presented for the periodically excited non-autonomous dynamical system with an order gap between the exciting frequency and the natural frequency.By regarding the exciting term as a slow-varying parameter,a generalized autonomous fast subsystem can be defined,the equilibrium branches as well as the bifurcations of which can be employed to account for the mechanism of the bursting oscillations by combining the transformed phase portrait introduced.As an example,a typical periodically excited Hartley model is used to demonstrate the validness of the method,in which the exciting frequency is far less than the natural frequency.The equilibrium branches and their bifurcations of the fast subsystem with the variation of the slow-varying parameter are presented.Bursting oscillations for two typical cases are considered,which reveals that,fold bifurcation may cause the the trajectory to jump between different equilibrium branches,while Hopf bifurcation may cause the trajectory to oscillate around the stable limit cycle.展开更多
A hybrid method combining simplified sub-entire domain basis function method of moment with finite element method( SSED-MoM /FEM) is accelerated for electromagnetic( EM) scattering analysis of large-scale periodic str...A hybrid method combining simplified sub-entire domain basis function method of moment with finite element method( SSED-MoM /FEM) is accelerated for electromagnetic( EM) scattering analysis of large-scale periodic structures.The unknowns are reduced sharply with non-uniform mesh in FEM. The computational complexity of the hybrid method is dramatically declined by applying conjugate gradient-fast Fourier transform( CG-FFT) to the integral equations of both electric field and magnetic field. The efficiency is further improved by using OpenMP technique. Numerical results demonstrate that the SSED-MoM /FEM method can be accelerated for more than three thousand times with large-scale periodic structures.展开更多
Based on the concepts of fast polarization, effective electric field and electron impact ionization criterion, the effect of polymer type on electric breakdown strength （EBD） on a nanosecond time scale is investigat...Based on the concepts of fast polarization, effective electric field and electron impact ionization criterion, the effect of polymer type on electric breakdown strength （EBD） on a nanosecond time scale is investigated, and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived. According to this formula, it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers. By calculating the effective relative dielectric constants for different types of polymers, the theoretical relation for the electric breakdown strengths of common polymers is predicted. To verify the prediction, the polymers of PE （polyethylene）, PTFE （polytetrafluoroethelene）, PMMA （organic glass） and Nylon are tested with a nanosecond-pulse generator. The experimental result shows EBD （PTFE） 〉 EBD （PMMA） 〉 EBD （Nylon） 〉 EBD （PE）. This result is consistent with the theoretical prediction.展开更多
针对在无人机高速运动场景下,相关滤波跟踪算法存在边界效应和滤波器退化等问题,提出了一种融合相机运动补偿的自适应时空正则化的无人机跟踪相关滤波算法。首先,在相关滤波器中设计了一种自适应空间正则化方法来缓解边界效应;其次,为...针对在无人机高速运动场景下,相关滤波跟踪算法存在边界效应和滤波器退化等问题,提出了一种融合相机运动补偿的自适应时空正则化的无人机跟踪相关滤波算法。首先,在相关滤波器中设计了一种自适应空间正则化方法来缓解边界效应;其次,为防止滤波器退化,设计了基于高置信度样本的时间正则化方法及优化更新策略,同时利用交替方向乘子法(Alternating Direction Method of Multipliers,ADMM)优化目标函数的求解,保证了算法的运行效率;然后,设计了快速尺度滤波器,实现目标尺度的快速估计;最后,提出了一种鲁棒性的跟踪不确定性规则及基于相机运动补偿的重检测器,使得目标丢失后可及时恢复。实验结果表明,提出的算法在无人机数据集上的精确度和成功率分别可达0.739和0.634,与ECO_HC(Efficient Convolution Operators-Hand Crafted)算法相比分别提升了1.65%和6.9%,与同类主流算法相比,有效地提升了跟踪时的精确度和成功率,经历快速运动、目标遮挡等情况时应用该算法的无人机也表现出良好的跟踪性能。展开更多
文摘In this paper we report a kind of fast-scale instability occurring in the single-ended primary inductance converter （SEPIC） power factor pre-regulator, which is designed to operate in discontinuous conduction mode. Main results are given by exact cycle-by-cycle computer simulations as well as theoretical analysis. It is found that the instability phenomenon manifests itself as a fast-scale bifurcation at the switching period, which implies the occurrence of border collision bifurcation, or is related to the transition of the regular operating mode of the SEPIC. According to the theoretical analysis and simulation results, the effects of parameters on system stability, and the locations of the bifurcation points are confirmed. Moreover, the effects of such an instability on power factor and switching stress are also discussed. Finally, the occurrence of the asymmetric bifurcation locations is investigated. The results show that this work provides a convenient means of predicting stability boundaries which can facilitate the selection of the practical parameters.
基金supported by the National Natural Science Foundation of China(Grants11632008 and 11872189)
文摘A modified slow-fast analysis method is presented for the periodically excited non-autonomous dynamical system with an order gap between the exciting frequency and the natural frequency.By regarding the exciting term as a slow-varying parameter,a generalized autonomous fast subsystem can be defined,the equilibrium branches as well as the bifurcations of which can be employed to account for the mechanism of the bursting oscillations by combining the transformed phase portrait introduced.As an example,a typical periodically excited Hartley model is used to demonstrate the validness of the method,in which the exciting frequency is far less than the natural frequency.The equilibrium branches and their bifurcations of the fast subsystem with the variation of the slow-varying parameter are presented.Bursting oscillations for two typical cases are considered,which reveals that,fold bifurcation may cause the the trajectory to jump between different equilibrium branches,while Hopf bifurcation may cause the trajectory to oscillate around the stable limit cycle.
基金Supported by the Aeronautical Science Foundation of China(20121852031)
文摘A hybrid method combining simplified sub-entire domain basis function method of moment with finite element method( SSED-MoM /FEM) is accelerated for electromagnetic( EM) scattering analysis of large-scale periodic structures.The unknowns are reduced sharply with non-uniform mesh in FEM. The computational complexity of the hybrid method is dramatically declined by applying conjugate gradient-fast Fourier transform( CG-FFT) to the integral equations of both electric field and magnetic field. The efficiency is further improved by using OpenMP technique. Numerical results demonstrate that the SSED-MoM /FEM method can be accelerated for more than three thousand times with large-scale periodic structures.
文摘Based on the concepts of fast polarization, effective electric field and electron impact ionization criterion, the effect of polymer type on electric breakdown strength （EBD） on a nanosecond time scale is investigated, and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived. According to this formula, it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers. By calculating the effective relative dielectric constants for different types of polymers, the theoretical relation for the electric breakdown strengths of common polymers is predicted. To verify the prediction, the polymers of PE （polyethylene）, PTFE （polytetrafluoroethelene）, PMMA （organic glass） and Nylon are tested with a nanosecond-pulse generator. The experimental result shows EBD （PTFE） 〉 EBD （PMMA） 〉 EBD （Nylon） 〉 EBD （PE）. This result is consistent with the theoretical prediction.
文摘针对在无人机高速运动场景下,相关滤波跟踪算法存在边界效应和滤波器退化等问题,提出了一种融合相机运动补偿的自适应时空正则化的无人机跟踪相关滤波算法。首先,在相关滤波器中设计了一种自适应空间正则化方法来缓解边界效应;其次,为防止滤波器退化,设计了基于高置信度样本的时间正则化方法及优化更新策略,同时利用交替方向乘子法(Alternating Direction Method of Multipliers,ADMM)优化目标函数的求解,保证了算法的运行效率;然后,设计了快速尺度滤波器,实现目标尺度的快速估计;最后,提出了一种鲁棒性的跟踪不确定性规则及基于相机运动补偿的重检测器,使得目标丢失后可及时恢复。实验结果表明,提出的算法在无人机数据集上的精确度和成功率分别可达0.739和0.634,与ECO_HC(Efficient Convolution Operators-Hand Crafted)算法相比分别提升了1.65%和6.9%,与同类主流算法相比,有效地提升了跟踪时的精确度和成功率,经历快速运动、目标遮挡等情况时应用该算法的无人机也表现出良好的跟踪性能。
