As the fastest integral equation solver to date, the multilevel fast multipole algorithm （MLFMA） has been applied successfully to solve electromagnetic scattering and radiation from 3D electrically large objects. Bu...As the fastest integral equation solver to date, the multilevel fast multipole algorithm （MLFMA） has been applied successfully to solve electromagnetic scattering and radiation from 3D electrically large objects. But for very large-scale problems, the storage and CPU time required in MLFMA are still expensive. Fast 3D electromagnetic scattering and radiation solvers are introduced based on MLFMA. A brief review of MLFMA is first given. Then, four fast methods including higher-order MLFMA （HO-MLFMA）, fast far field approximation combined with adaptive ray propagation MLFMA （FAFFA-ARP-MLFMA）, local MLFMA and parallel MLFMA are introduced. Some typical numerical results demonstrate the efficiency of these fast methods.展开更多
Variation of ocean environmental parameters is important to sound ray propagation. This article studies the problem of sound ray propagation in seawater by BELLHOP ray model. The sensitivities of sound ray propagation...Variation of ocean environmental parameters is important to sound ray propagation. This article studies the problem of sound ray propagation in seawater by BELLHOP ray model. The sensitivities of sound ray propagation to the variations of seabed topography and depth of sound source by simulation. The results show that the depth variation of sound source is the main cause for emerging and disappearing of surface sound channel, accumulation area and deep sound channel. The deviation of sound ray propagation is in accordance with seabed topography change.展开更多
The article considers peculiarities of underwater monitoring of moving objects in the shallow water areas, particularly seaports. These areas are characterized by a multitude of factors influencing the efficiency of d...The article considers peculiarities of underwater monitoring of moving objects in the shallow water areas, particularly seaports. These areas are characterized by a multitude of factors influencing the efficiency of detection. Nonstationarity conditions of sound propagation and specific interference caused by shipping are the major factors. The various algorithms for the space-time signal processing have been tested and some experimental results are presented. It has been shown that the use of clipped mode in conjunction with the correlation processing of wideband signals and subsequent speckle tracking allow realizing high efficiency of monitoring.展开更多
基金the National Natural Science Foundation of China (60431010, 60601008)the New CenturyExcellent Talent Support Plan of China (NCET-05-0805)+2 种基金the International Joint Research Project ("111" Project)(b07048)the"973" Programs 61360(2008CB317110)Young Doctor Displine Platform University of Electronic Science and Technology of China.
文摘As the fastest integral equation solver to date, the multilevel fast multipole algorithm （MLFMA） has been applied successfully to solve electromagnetic scattering and radiation from 3D electrically large objects. But for very large-scale problems, the storage and CPU time required in MLFMA are still expensive. Fast 3D electromagnetic scattering and radiation solvers are introduced based on MLFMA. A brief review of MLFMA is first given. Then, four fast methods including higher-order MLFMA （HO-MLFMA）, fast far field approximation combined with adaptive ray propagation MLFMA （FAFFA-ARP-MLFMA）, local MLFMA and parallel MLFMA are introduced. Some typical numerical results demonstrate the efficiency of these fast methods.
文摘Variation of ocean environmental parameters is important to sound ray propagation. This article studies the problem of sound ray propagation in seawater by BELLHOP ray model. The sensitivities of sound ray propagation to the variations of seabed topography and depth of sound source by simulation. The results show that the depth variation of sound source is the main cause for emerging and disappearing of surface sound channel, accumulation area and deep sound channel. The deviation of sound ray propagation is in accordance with seabed topography change.
文摘The article considers peculiarities of underwater monitoring of moving objects in the shallow water areas, particularly seaports. These areas are characterized by a multitude of factors influencing the efficiency of detection. Nonstationarity conditions of sound propagation and specific interference caused by shipping are the major factors. The various algorithms for the space-time signal processing have been tested and some experimental results are presented. It has been shown that the use of clipped mode in conjunction with the correlation processing of wideband signals and subsequent speckle tracking allow realizing high efficiency of monitoring.
