Elastic waves in the seabed generated by low-frequency noise radiating from ships are known as ship seismic waves and can be used to detect and identify ships. To obtain the propagation characteristics of ship seismic...Elastic waves in the seabed generated by low-frequency noise radiating from ships are known as ship seismic waves and can be used to detect and identify ships. To obtain the propagation characteristics of ship seismic waves, an algorithm for calculating Seismic waves at the seafloor is presented based on the staggered-grid finite difference method. The accuracy of the algorithm was tested by comparison with analytical solutions. Numerical simulation of seismic waves generated by a low-frequency point sotmd source in a typical shallow sea environment was carried out. Using various source frequencies and locations in the numerical simulation, we show that the seismic waves in the near field are composed mostly of transmitted S-waves and interface waves while transmitted P-waves are weak near the seafloor. However, in the far field, the wave components of the seismic wave are mainly normal modes and interface waves, with the latter being relatively strong in the waveforms, As the source frequency decreases, the normal modes become smaller and the interface waves dominate the time series of the seismic waves.展开更多
Recent satellite altimeter observations have indicated that internal tides （ITs） from the Luzon Strait （LS） propagate more than 2 500 km into the Western Pacific （WP）. This study used a high-resolution three-dim...Recent satellite altimeter observations have indicated that internal tides （ITs） from the Luzon Strait （LS） propagate more than 2 500 km into the Western Pacific （WP）. This study used a high-resolution three-dimensional numerical model to reproduce and examine the ITs radiation process. The propagation of diurnal and semidiurnal ITs showed different patterns and variations. Diurnal ITs with lower frequency were affected more by the earth＇s rotation and they were bent more toward the equator than semidiurnal ITs. ITs phase speeds are functions of latitude and diurnal ITs showed greater distinctions of phase speeds during propagation. For M2 ITs, the wavelength remained nearly unchanged but the beam width increased significantly during propagation away from the LS. For diurnal ITs （K1 and O0, the wavelength decreased noticeably with latitude, while the beam width varied little during propagation because of blocking by land. Baroclinic energy was also examined as a complement to satellite results reported by Zhao （2014）. The magnitude of the generated baroclinic energy flux reduced remarkably within 300 km from the generation site but it then decayed slowly when propagating into abyssal sea. Baroclinic energy of diurnal ITs was found to dissipate at a slower rate than semidiurnal ITs along the main propagation path in the WP.展开更多
Since single event transient pulse quenching can reduce the SET(single event transient) pulsewidths effectively,the charge collected by passive device should be maximized in order to minimize the propagated SET.From t...Since single event transient pulse quenching can reduce the SET(single event transient) pulsewidths effectively,the charge collected by passive device should be maximized in order to minimize the propagated SET.From the perspective of the layout and circuit design,the SET pulsewidths can be greatly inhibited by minimizing the layout spacing and signal propagation delay,which sheds new light on the radiation-hardened ICs(integrated circuits) design.Studies show that the SET pulsewidths of propagation are not in direct proportion to the LET(linear energy transfer) of incident particles,thus the defining of the LET threshold should be noted when SET/SEU(single event upset) occurs for the radiation-hardened design.The capability of anti-radiation meets the demand when LET is high but some soft errors may occur when LET is low.Therefore,radiation experiments should be focused on evaluating the LET that demonstrates the worst response to the circuit.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.51179195,51679248)the National Defense Foundation of China(No.513030203-02)
文摘Elastic waves in the seabed generated by low-frequency noise radiating from ships are known as ship seismic waves and can be used to detect and identify ships. To obtain the propagation characteristics of ship seismic waves, an algorithm for calculating Seismic waves at the seafloor is presented based on the staggered-grid finite difference method. The accuracy of the algorithm was tested by comparison with analytical solutions. Numerical simulation of seismic waves generated by a low-frequency point sotmd source in a typical shallow sea environment was carried out. Using various source frequencies and locations in the numerical simulation, we show that the seismic waves in the near field are composed mostly of transmitted S-waves and interface waves while transmitted P-waves are weak near the seafloor. However, in the far field, the wave components of the seismic wave are mainly normal modes and interface waves, with the latter being relatively strong in the waveforms, As the source frequency decreases, the normal modes become smaller and the interface waves dominate the time series of the seismic waves.
基金Supported by the National Natural Science Foundation of China(Nos.41528601,41376029,U1406401,41421005)the Strategic Pioneering Research Program of CAS(Nos.XDA10020104,XDA10020101)the CAS Interdisciplinary Innovation Team“Ocean Mesoscale Dynamical Processes and ecological effect”
文摘Recent satellite altimeter observations have indicated that internal tides （ITs） from the Luzon Strait （LS） propagate more than 2 500 km into the Western Pacific （WP）. This study used a high-resolution three-dimensional numerical model to reproduce and examine the ITs radiation process. The propagation of diurnal and semidiurnal ITs showed different patterns and variations. Diurnal ITs with lower frequency were affected more by the earth＇s rotation and they were bent more toward the equator than semidiurnal ITs. ITs phase speeds are functions of latitude and diurnal ITs showed greater distinctions of phase speeds during propagation. For M2 ITs, the wavelength remained nearly unchanged but the beam width increased significantly during propagation away from the LS. For diurnal ITs （K1 and O0, the wavelength decreased noticeably with latitude, while the beam width varied little during propagation because of blocking by land. Baroclinic energy was also examined as a complement to satellite results reported by Zhao （2014）. The magnitude of the generated baroclinic energy flux reduced remarkably within 300 km from the generation site but it then decayed slowly when propagating into abyssal sea. Baroclinic energy of diurnal ITs was found to dissipate at a slower rate than semidiurnal ITs along the main propagation path in the WP.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60836004 and 61006070)
文摘Since single event transient pulse quenching can reduce the SET(single event transient) pulsewidths effectively,the charge collected by passive device should be maximized in order to minimize the propagated SET.From the perspective of the layout and circuit design,the SET pulsewidths can be greatly inhibited by minimizing the layout spacing and signal propagation delay,which sheds new light on the radiation-hardened ICs(integrated circuits) design.Studies show that the SET pulsewidths of propagation are not in direct proportion to the LET(linear energy transfer) of incident particles,thus the defining of the LET threshold should be noted when SET/SEU(single event upset) occurs for the radiation-hardened design.The capability of anti-radiation meets the demand when LET is high but some soft errors may occur when LET is low.Therefore,radiation experiments should be focused on evaluating the LET that demonstrates the worst response to the circuit.
