研究毫米波雷达的地杂波特性对提高毫米波雷达的目标探测性能和大地遥感具有重要的作用。针对毫米波雷达地杂波测量问题,讨论了地杂波散射系数测量方法,对毫米波线性调频连续波(linear frequency modula-tion continuous wave,LFMCW)雷...研究毫米波雷达的地杂波特性对提高毫米波雷达的目标探测性能和大地遥感具有重要的作用。针对毫米波雷达地杂波测量问题,讨论了地杂波散射系数测量方法,对毫米波线性调频连续波(linear frequency modula-tion continuous wave,LFMCW)雷达散射计的系统校准、有效独立采样数、数据处理中软件门的应用以及减少测量误差等相关技术进行了研究;给出了Ka波段散射计测量灌木丛杂波特性的结果,结果表明在入射角小于15°范围内灌木丛的杂波幅度分布服从瑞利分布。展开更多
In this paper, a computer visualization approach is proposed for electromagnetic wave interaction with structures by mains of finite difference-time doain method (F-D) and computer graphics. By visualization of FDTD, ...In this paper, a computer visualization approach is proposed for electromagnetic wave interaction with structures by mains of finite difference-time doain method (F-D) and computer graphics. By visualization of FDTD, Phenomena such as wave propagation, penetration through structures, renection and absorption by structures are observed. Visualization of electromagnetic wave interactions with two wing-shaped structures is demonstrated. These examples indicate that the approach describe in the paper offers an effective way for investigating electromagnetic wave phenomena and is helpful to the engineers in controlling radar signature of the targets.展开更多
Concerning the PDRA (pulse doppler radar altimeter) designing and evaluation, owing to that the specifications of PDRA should be adaptively fixed according to the ETR (earth terrain return), and that in certain stages...Concerning the PDRA (pulse doppler radar altimeter) designing and evaluation, owing to that the specifications of PDRA should be adaptively fixed according to the ETR (earth terrain return), and that in certain stages of product evaluation of PDRA which means the designations of PDRA are successful or not, the usage of ETR are indispensable, so the terrain return from spherical earth is critically important. A complete analytic derivation of the antenna shot section model of PDRA and the bright section model constrained by pulse emitted from antenna are given. Furthermore, the doppler effect mode and the earth terrain RCF (radar crossing factor) model are constructively analyzed. Then, the computing methodology on PDRA, which are used to compute the scattering power, scattering doppler spectrum, and the scattering signal, is studied. Besides, in order to check the correctness and efficiency of the algorithm, computing examples of ETR (earth terrain return) under the supposing premises are furnished. Finally, the conclusion is drawn that the models and algorithm are rational, the computational precise is satisfactory, the cost of computing time is low.展开更多
A new model is proposed to estimate the significant wave heights with ERS-1/2 scatterometer data. The results show that the relationship between wave parameters and radar backscattering cross section is similar to tha...A new model is proposed to estimate the significant wave heights with ERS-1/2 scatterometer data. The results show that the relationship between wave parameters and radar backscattering cross section is similar to that between wind and the radar backscattering cross section. Therefore, the relationship between significant wave height and the radar backscattering cross section is established with a neural network algorithm, which is, if the average wave period is ≤7s, the root mean square of significant wave height retrieved from ERS-1/2 data is 0.51 m, or 0.72 m if it is >7s otherwise.展开更多
ASTEC and ICARE / CATHARE are computer codes allowing analysing severe accidents in LWRs. The applicability of these codes to Russian reactors of VVER type is a clear common IRSN-GRS objective. The current work in col...ASTEC and ICARE / CATHARE are computer codes allowing analysing severe accidents in LWRs. The applicability of these codes to Russian reactors of VVER type is a clear common IRSN-GRS objective. The current work in collaboration between IRSN and RRC K1 （Russia） aims at reaching this objective. This paper is devoted to ASTEC and ICARE / CATHARE simulations of a severe accident scenario on a VVER-1000. A Large Break LOCA （850 mm） sequence accompanied with the station blackout was selected for analysis. ICARE / CATHARE V2.2 successfully predicted main events of the accident： heat-up of the core, core degradation and melt relocation to the lower part of the core. A simulation of a complete accidental sequence was performed with ASTEC V 1.3-rev3 code： core heat-up and melting, melt relocation, reactor vessel rupture, molten corium / concrete interaction, release and distribution of steam, H2, CO, CO2, fission products and aerosols in the RCS and the containment. It must be pointed out that, as concerns the thermalhydraulics front-end phase and the in-vessel degradation phase, the ASTEC simulation exhibited consistent results with respect to the best-estimate ICARE / CATHARE ones.展开更多
文摘研究毫米波雷达的地杂波特性对提高毫米波雷达的目标探测性能和大地遥感具有重要的作用。针对毫米波雷达地杂波测量问题,讨论了地杂波散射系数测量方法,对毫米波线性调频连续波(linear frequency modula-tion continuous wave,LFMCW)雷达散射计的系统校准、有效独立采样数、数据处理中软件门的应用以及减少测量误差等相关技术进行了研究;给出了Ka波段散射计测量灌木丛杂波特性的结果,结果表明在入射角小于15°范围内灌木丛的杂波幅度分布服从瑞利分布。
文摘In this paper, a computer visualization approach is proposed for electromagnetic wave interaction with structures by mains of finite difference-time doain method (F-D) and computer graphics. By visualization of FDTD, Phenomena such as wave propagation, penetration through structures, renection and absorption by structures are observed. Visualization of electromagnetic wave interactions with two wing-shaped structures is demonstrated. These examples indicate that the approach describe in the paper offers an effective way for investigating electromagnetic wave phenomena and is helpful to the engineers in controlling radar signature of the targets.
文摘Concerning the PDRA (pulse doppler radar altimeter) designing and evaluation, owing to that the specifications of PDRA should be adaptively fixed according to the ETR (earth terrain return), and that in certain stages of product evaluation of PDRA which means the designations of PDRA are successful or not, the usage of ETR are indispensable, so the terrain return from spherical earth is critically important. A complete analytic derivation of the antenna shot section model of PDRA and the bright section model constrained by pulse emitted from antenna are given. Furthermore, the doppler effect mode and the earth terrain RCF (radar crossing factor) model are constructively analyzed. Then, the computing methodology on PDRA, which are used to compute the scattering power, scattering doppler spectrum, and the scattering signal, is studied. Besides, in order to check the correctness and efficiency of the algorithm, computing examples of ETR (earth terrain return) under the supposing premises are furnished. Finally, the conclusion is drawn that the models and algorithm are rational, the computational precise is satisfactory, the cost of computing time is low.
基金Supported by the National High Technology Research and Development Program of China (863 Program) (No.2008AA09Z102)the Canadian Space Agency (CSA) GRIP Program.
文摘A new model is proposed to estimate the significant wave heights with ERS-1/2 scatterometer data. The results show that the relationship between wave parameters and radar backscattering cross section is similar to that between wind and the radar backscattering cross section. Therefore, the relationship between significant wave height and the radar backscattering cross section is established with a neural network algorithm, which is, if the average wave period is ≤7s, the root mean square of significant wave height retrieved from ERS-1/2 data is 0.51 m, or 0.72 m if it is >7s otherwise.
文摘ASTEC and ICARE / CATHARE are computer codes allowing analysing severe accidents in LWRs. The applicability of these codes to Russian reactors of VVER type is a clear common IRSN-GRS objective. The current work in collaboration between IRSN and RRC K1 （Russia） aims at reaching this objective. This paper is devoted to ASTEC and ICARE / CATHARE simulations of a severe accident scenario on a VVER-1000. A Large Break LOCA （850 mm） sequence accompanied with the station blackout was selected for analysis. ICARE / CATHARE V2.2 successfully predicted main events of the accident： heat-up of the core, core degradation and melt relocation to the lower part of the core. A simulation of a complete accidental sequence was performed with ASTEC V 1.3-rev3 code： core heat-up and melting, melt relocation, reactor vessel rupture, molten corium / concrete interaction, release and distribution of steam, H2, CO, CO2, fission products and aerosols in the RCS and the containment. It must be pointed out that, as concerns the thermalhydraulics front-end phase and the in-vessel degradation phase, the ASTEC simulation exhibited consistent results with respect to the best-estimate ICARE / CATHARE ones.
