Temperature profiles provided by the Constellation Observing System for Meteorology, Ionosphere and Climate （COSMIC） global positioning system （GPS） satellite constellation were used to study an eight-year series ...Temperature profiles provided by the Constellation Observing System for Meteorology, Ionosphere and Climate （COSMIC） global positioning system （GPS） satellite constellation were used to study an eight-year series （2007 to 2015） of gravity wave （GW） potential energy in the stratosphere （18-30 kin） around the Tibetan Plateau （TP）. We found that with increasing altitude, the GW potential energy （Ep） values in the stratosphere caused by convection decreases. The importance of GWs that are stimulated by topography is enhanced in this area. In the TP, which was considered to lack strong topographical GW activity, clear activity existed in the spring and winter of all studied years. Based on the latitudinal zone of the TP, the distribution of GW potential energy is highly consistent with the elevation of the local topography. The activities of topographical GWs are strongly filtered as they propagate upward to the area of zero speed wind. The analysis indicates that in the TP, clear orographic GW excitation exists and propagates upward to the upper stratosphere, where it is greatly influenced by the wind.展开更多
To investigate the relationship between velocity structure and earthquake activity on the southeastern front of the Tibetan Plat- eau, we make use of continuous observations of seismic ambient noise data obtained at 5...To investigate the relationship between velocity structure and earthquake activity on the southeastern front of the Tibetan Plat- eau, we make use of continuous observations of seismic ambient noise data obtained at 55 broadband stations from the regional Yunnan Seismic Network. These data are used to compute Rayleigh wave Green＇s Functions by cross-correlating between two stations, extracting phase velocity dispersion curves, and finally inverting to image Rayleigh wave phase velocity with periods between 5 and 34 s by ambient noise tomography. The results tie structures in the studied region. Phase velocity anomalies show significant lateral variations in crustal and uppermost man- at short periods （5-12 s） are closely related to regional tectonic features such as sediment thickness and the depth of the crystalline basement. The Sichuan-Yunnan rhombic block, enclosed by the Honghe, Xiaojiang and Jianchuan faults, emerges as a large range of low-velocity anomalies at periods of 16-26 s, that in- verts to high-velocity anomalies at periods of 30-34 s. The phase velocity variation in the vicinity of the Sichuan-Yunnan rhombic block suggests that the low-velocity anomaly area in the middle-lower crust may correspond to lower crustal channel- ized flow of the Tibetan Plateau. The spatial distribution of strong earthquakes since 1970 reveals that the Yunnan region is inhomogeneous and shows prominent characteristics of block motion. However, earthquakes mostly occur in the upper crust, with the exception of the middle-Yunnan block where earthquakes occur at the interface zone between high and low velocity as well as in the low-velocity zones, with magnitudes being generally less than 7. There are few earthquakes of magnitude 5 at the depths of 15-30 km, where gather earthquakes of magnitude 7 or higher ones which mainly occur in the interface zone between high and low velocities with others extending to the high-velocity abnormal zone.展开更多
We study a quantum electrodynamics(QED) system made of a two-level atom and a semi-infinite rectangular waveguide, which behaves as a perfect mirror in one end. The spatial dependence of the atomic spontaneous emissio...We study a quantum electrodynamics(QED) system made of a two-level atom and a semi-infinite rectangular waveguide, which behaves as a perfect mirror in one end. The spatial dependence of the atomic spontaneous emission has been included in the coupling strength relevant to the eigenmodes of the waveguide. The role of retardation is studied for the atomic transition frequency far away from the cutoff frequencies. The atom-mirror distance introduces different phases and retardation times into the dynamics of the atom interacting resonantly with the corresponding transverse modes. It is found that the upper state population decreases from its initial as long as the atom-mirror distance does not vanish, and is lowered and lowered when more and more transverse modes are resonant with the atom. The atomic spontaneous emission can be either suppressed or enhanced by adjusting the atomic location for short retardation time.There are partial revivals and collapses due to the photon reabsorbed and re-emitted by the atom for long retardation time.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.41322029,41474129 & 41421063)the Project of Chinese Academy of Sciences(Grant Nos.KJCX2-EW-J01 & KZZD-EW-0101)+1 种基金Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2011324)the Fundamental Research Funds for the Central Universities
文摘Temperature profiles provided by the Constellation Observing System for Meteorology, Ionosphere and Climate （COSMIC） global positioning system （GPS） satellite constellation were used to study an eight-year series （2007 to 2015） of gravity wave （GW） potential energy in the stratosphere （18-30 kin） around the Tibetan Plateau （TP）. We found that with increasing altitude, the GW potential energy （Ep） values in the stratosphere caused by convection decreases. The importance of GWs that are stimulated by topography is enhanced in this area. In the TP, which was considered to lack strong topographical GW activity, clear activity existed in the spring and winter of all studied years. Based on the latitudinal zone of the TP, the distribution of GW potential energy is highly consistent with the elevation of the local topography. The activities of topographical GWs are strongly filtered as they propagate upward to the area of zero speed wind. The analysis indicates that in the TP, clear orographic GW excitation exists and propagates upward to the upper stratosphere, where it is greatly influenced by the wind.
基金supported by National Natural Science Foundation of China(Grant No.41174042)China National Special Fund for Earthquake Scientific Research in Public Interest(Grant No.201008001)
文摘To investigate the relationship between velocity structure and earthquake activity on the southeastern front of the Tibetan Plat- eau, we make use of continuous observations of seismic ambient noise data obtained at 55 broadband stations from the regional Yunnan Seismic Network. These data are used to compute Rayleigh wave Green＇s Functions by cross-correlating between two stations, extracting phase velocity dispersion curves, and finally inverting to image Rayleigh wave phase velocity with periods between 5 and 34 s by ambient noise tomography. The results tie structures in the studied region. Phase velocity anomalies show significant lateral variations in crustal and uppermost man- at short periods （5-12 s） are closely related to regional tectonic features such as sediment thickness and the depth of the crystalline basement. The Sichuan-Yunnan rhombic block, enclosed by the Honghe, Xiaojiang and Jianchuan faults, emerges as a large range of low-velocity anomalies at periods of 16-26 s, that in- verts to high-velocity anomalies at periods of 30-34 s. The phase velocity variation in the vicinity of the Sichuan-Yunnan rhombic block suggests that the low-velocity anomaly area in the middle-lower crust may correspond to lower crustal channel- ized flow of the Tibetan Plateau. The spatial distribution of strong earthquakes since 1970 reveals that the Yunnan region is inhomogeneous and shows prominent characteristics of block motion. However, earthquakes mostly occur in the upper crust, with the exception of the middle-Yunnan block where earthquakes occur at the interface zone between high and low velocity as well as in the low-velocity zones, with magnitudes being generally less than 7. There are few earthquakes of magnitude 5 at the depths of 15-30 km, where gather earthquakes of magnitude 7 or higher ones which mainly occur in the interface zone between high and low velocities with others extending to the high-velocity abnormal zone.
基金Supported by National Natural Science Foundation of China under Grant Nos.11374095,11422540,11434011,and 11575058National Fundamental Research Program of China(the 973 Program)under Grant No.2012CB922103Hunan Provincial Natural Science Foundation of China under Grant No.11JJ7001
文摘We study a quantum electrodynamics(QED) system made of a two-level atom and a semi-infinite rectangular waveguide, which behaves as a perfect mirror in one end. The spatial dependence of the atomic spontaneous emission has been included in the coupling strength relevant to the eigenmodes of the waveguide. The role of retardation is studied for the atomic transition frequency far away from the cutoff frequencies. The atom-mirror distance introduces different phases and retardation times into the dynamics of the atom interacting resonantly with the corresponding transverse modes. It is found that the upper state population decreases from its initial as long as the atom-mirror distance does not vanish, and is lowered and lowered when more and more transverse modes are resonant with the atom. The atomic spontaneous emission can be either suppressed or enhanced by adjusting the atomic location for short retardation time.There are partial revivals and collapses due to the photon reabsorbed and re-emitted by the atom for long retardation time.
