1.引言
早期关于拓扑发现的研究主要集中于第3层,也就是网络层的拓扑结构,但是随着网桥被广泛用于连接多个局域网段构成桥接局域网(BLAN,Bridge Local Area Network)[1]以便提高网络的可靠性、获得更大的带宽或是提供不同局域网协议之...1.引言
早期关于拓扑发现的研究主要集中于第3层,也就是网络层的拓扑结构,但是随着网桥被广泛用于连接多个局域网段构成桥接局域网(BLAN,Bridge Local Area Network)[1]以便提高网络的可靠性、获得更大的带宽或是提供不同局域网协议之间的互通[7],忽略第2层设备(网桥)之间连接关系的拓扑结构信息显得"粒度"太粗了,桥接局域网的网络管理需求使得网络拓扑结构的自动发现必须向下延伸.展开更多
This paper presents a new topology for a High Voltage （HV） 50 kV, High Frequency （HF） 20 kHz, multi-cored transformer suitable for use in pulsed power application systems. The main requirements are： high voltage ...This paper presents a new topology for a High Voltage （HV） 50 kV, High Frequency （HF） 20 kHz, multi-cored transformer suitable for use in pulsed power application systems. The main requirements are： high voltage capability, small size and weight. The HV, HF transformer is the main critical block of a high frequency power converter system. The transformer must have high electrical efficiency and in the proposed approach has to be optimized by the number of the cores. The transformer concept has been investigated analytically and through software simulations and experiments. This paper introduces the transformer topology and discusses the design procedure. Experimental measurements to predict core losses are also presented. The losses of epoxy coated nanocrystalline are compared to the losses in a new uncoated core.展开更多
We performed angle-resolved photoemission spectroscopy studies on a series of FeTe_(1-x)Se_x monolayer films grown on Sr TiO_3.The superconductivity of the films is robust and rather insensitive to the variations of t...We performed angle-resolved photoemission spectroscopy studies on a series of FeTe_(1-x)Se_x monolayer films grown on Sr TiO_3.The superconductivity of the films is robust and rather insensitive to the variations of the band position and effective mass caused by the substitution of Se by Te.However,the band gap between the electron-and hole-like bands at the Brillouin zone center decreases towards band inversion and parity exchange,which drive the system to a nontrivial topological state predicted by theoretical calculations.Our results provide a clear experimental indication that the FeTe_(1-x)Se_x monolayer materials are high-temperature connate topological superconductors in which band topology and superconductivity are integrated intrinsically.展开更多
In this work,we study the development,evolution,and migration of turbulent coherent structures in the turbulent boundary layer at Reτ=630 using time-resolved particle image velocimetry(TR-PIV).Multiple techniques,inc...In this work,we study the development,evolution,and migration of turbulent coherent structures in the turbulent boundary layer at Reτ=630 using time-resolved particle image velocimetry(TR-PIV).Multiple techniques,including multi-scale analysis,conditional averaging,cross-correlation,and spatial-temporal topological analysis are applied to extract the evolution principle,migration trajectory,and convection velocity vector of the targeted coherent structures from a Lagrangian perspective.The spanwise vortex structures with larger scale and intensity at a certain wall-normal height y were the main focus of the present study.In the statistical sense,spanwise vortex structures move away from the wall with the shape changing from a bulge to an ellipse,and finally to a circle.Two straight lines emerge from the mean transfer trajectory curve of the spanwise vortex,in which the horizontal one is located at the viscous sublayer(y^(+)<10),the other is a logarithmic straight line existing in the range of 50<y^(+)<120,and the inclination angle of the tangential migration path is fixed at around 12°.The streamwise convection velocity U_(c)of scaled spanwise vortex structures satisfies U_(c)/U_(∞)=0.5-0.6 below y=0.03δ(i.e.,U^(+)_(c)=11-13 undery^(+)=20).In particular,in the region of 50<y^(+)<120,the velocity growth curves of U_(c)and wall-normal convection velocity V_(c)follow the log-law distribution very well,and the slopes are consistent with that of the log-law region of the turbulent boundary layer.Our observations provide microscopic evidences of the logarithmic-linear distribution of the migration trajectory of spanwise vortex structures.展开更多
文摘1.引言
早期关于拓扑发现的研究主要集中于第3层,也就是网络层的拓扑结构,但是随着网桥被广泛用于连接多个局域网段构成桥接局域网(BLAN,Bridge Local Area Network)[1]以便提高网络的可靠性、获得更大的带宽或是提供不同局域网协议之间的互通[7],忽略第2层设备(网桥)之间连接关系的拓扑结构信息显得"粒度"太粗了,桥接局域网的网络管理需求使得网络拓扑结构的自动发现必须向下延伸.
文摘This paper presents a new topology for a High Voltage （HV） 50 kV, High Frequency （HF） 20 kHz, multi-cored transformer suitable for use in pulsed power application systems. The main requirements are： high voltage capability, small size and weight. The HV, HF transformer is the main critical block of a high frequency power converter system. The transformer must have high electrical efficiency and in the proposed approach has to be optimized by the number of the cores. The transformer concept has been investigated analytically and through software simulations and experiments. This paper introduces the transformer topology and discusses the design procedure. Experimental measurements to predict core losses are also presented. The losses of epoxy coated nanocrystalline are compared to the losses in a new uncoated core.
基金supported by grants from the Ministry of Science and Technology of China(2015CB921000,2016YFA0401000,2015CB921301,2016YFA0300300)the National Natural Science Foundation of China(11574371,11274362,1190020,11334012,11274381,11674371)
文摘We performed angle-resolved photoemission spectroscopy studies on a series of FeTe_(1-x)Se_x monolayer films grown on Sr TiO_3.The superconductivity of the films is robust and rather insensitive to the variations of the band position and effective mass caused by the substitution of Se by Te.However,the band gap between the electron-and hole-like bands at the Brillouin zone center decreases towards band inversion and parity exchange,which drive the system to a nontrivial topological state predicted by theoretical calculations.Our results provide a clear experimental indication that the FeTe_(1-x)Se_x monolayer materials are high-temperature connate topological superconductors in which band topology and superconductivity are integrated intrinsically.
基金the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.11802195)the National Natural Science Foundation of China(Grant Nos.12172242,and 11972251)+2 种基金the Key Program of the National Natural Science Foundation of China(Grant No.11732010)Sino-German International Cooperation Project supported by Sino-German Science Center(GZ1575)the Natural Science Foundation for Young Scientists of Shanxi Province,China(Grant No.201801D221027).
文摘In this work,we study the development,evolution,and migration of turbulent coherent structures in the turbulent boundary layer at Reτ=630 using time-resolved particle image velocimetry(TR-PIV).Multiple techniques,including multi-scale analysis,conditional averaging,cross-correlation,and spatial-temporal topological analysis are applied to extract the evolution principle,migration trajectory,and convection velocity vector of the targeted coherent structures from a Lagrangian perspective.The spanwise vortex structures with larger scale and intensity at a certain wall-normal height y were the main focus of the present study.In the statistical sense,spanwise vortex structures move away from the wall with the shape changing from a bulge to an ellipse,and finally to a circle.Two straight lines emerge from the mean transfer trajectory curve of the spanwise vortex,in which the horizontal one is located at the viscous sublayer(y^(+)<10),the other is a logarithmic straight line existing in the range of 50<y^(+)<120,and the inclination angle of the tangential migration path is fixed at around 12°.The streamwise convection velocity U_(c)of scaled spanwise vortex structures satisfies U_(c)/U_(∞)=0.5-0.6 below y=0.03δ(i.e.,U^(+)_(c)=11-13 undery^(+)=20).In particular,in the region of 50<y^(+)<120,the velocity growth curves of U_(c)and wall-normal convection velocity V_(c)follow the log-law distribution very well,and the slopes are consistent with that of the log-law region of the turbulent boundary layer.Our observations provide microscopic evidences of the logarithmic-linear distribution of the migration trajectory of spanwise vortex structures.
