On the basis of the earthquake （gL I〉3.0） catalog in North China from 1970 to 2009, the pattern of temporal and spatial distribution of medium-small earthquakes in Datong and its surrounding areas is studied by cor...On the basis of the earthquake （gL I〉3.0） catalog in North China from 1970 to 2009, the pattern of temporal and spatial distribution of medium-small earthquakes in Datong and its surrounding areas is studied by correlation analysis with a focus on its anomaly before moderate and strong earthquakes. With different spatial scales, temporal scales and time steps, the spatial distribution of earthquakes is converted to a sequence, then the correlation coefficients between the spatial distribution of medium-small earthquakes in a long-term and a longer time are calculated for the analysis of anomalies before moderate and strong earthquakes. In the study region center on the epicenter of the 1989 Datong- Yanggao earthquake （Ms5. 9） within a radius of less than 0.8~, with the time length of 3600 days, the longer time length of 3700 days, and the time step of 100 days, the correlation coefficient from 1980 to 2009 is steady between 0.94 and 1.00, but there were anomalies with values less than 0. 94 in the 2 years before the 1989 Datong-Yanggao earthquake （Ms 5.9）, the 1991 Datong earthquake （ Ms 5.8） and 1999 Hunyuan earthquake （Ms 5. 6 ）, which indicates the spatial distribution of a medium-small earthquake is very different from steady background seismicity. The implication for earthquake prediction from the anomaly of the correlation coefficient is also discussed with the three conclusions： （1） Before moderate and strong earthquakes in Datong and its surrounding areas, the obvious change of spatial distribution patterns of medium-small earthquake can be a kind of seismic precursor of the 2-year time scale for the prediction of an earthquake＇s time. （2） As the study region is restricted within a radius of less than 0. 8~, the result of correlation analysis is also good for the prediction of an earthquake＇s location. （3） The method of correlation analysis in this paper helps recognize the anomaly of spatial distribution of medium-small earthquake.展开更多
An explicit demonstration of the changes in fish assemblages is required to reveal the influence of damming on fish species.However,information from which to draw general conclusions regarding changes in fish assembla...An explicit demonstration of the changes in fish assemblages is required to reveal the influence of damming on fish species.However,information from which to draw general conclusions regarding changes in fish assemblages is insufficient because of the limitations of available approaches.We used a combination of acoustic surveys,gillnet sampling,and geostatistical simulations to document the spatiotemporal variations in the fish assemblages downstream of the Gezhouba Dam,before and after the third impoundment of Three Gorges Reservoir(TGR).To conduct a hydroacoustic identification of individual species,we matched the size distributions of the fishes captured by gillnet with those of the acoustic surveys.An optimum threshold of target strength of 50 dB re 1 m 2 was defined,and acoustic surveys were purposefully extended to the selected fish assemblages(i.e.,endemic Coreius species) that was acquired by the size and species selectivity of the gillnet sampling.The relative proportion of fish species in acoustic surveys was allocated based on the composition(%) of the harvest in the gillnet surveys.Geostatistical simulations were likewise used to generate spatial patterns of fish distribution,and to determine the absolute abundance of the selected fish assemblages.We observed both the species composition and the spatial distribution of the selected fish assemblages changed significantly after implementation of new flow regulation in the TGR,wherein an immediate sharp population decline in the Coreius occurred.Our results strongly suggested that the new flow regulation in the TGR impoundment adversely affected downstream fish species,particularly the endemic Coreius species.To determine the factors responsible for the decline,we associated the variation in the fish assemblage patterns with changes in the environment and determined that substrate erosion resulting from trapping practices in the TGR likely played a key role.展开更多
Morphological evolution of the solid-liquid interface near grain boundaries has been studied during directional solidification of succinonitrile-based transparent alloys (SCN-0.9wt%DCB). Experimental results show that...Morphological evolution of the solid-liquid interface near grain boundaries has been studied during directional solidification of succinonitrile-based transparent alloys (SCN-0.9wt%DCB). Experimental results show that the grain boundary provides the starting point of morphological instability of the solid-liquid interface. The initial perturbation near the grain boundary is significantly larger than other perturbations on the interface. The initial shape of the interface and the competition between the thermal direction and preferred crystalline orientations determine the subsequent growth pattern selections. The temporal variations of the curvature radius of cell/ridge tips near the grain boundary have also been studied when the instability occurs. This process is divided into three parts. As the pulling velocity increases, dendrites at the grain boundary grow in two different directions to form a bicrystal microstructure. Side branches on either side of the dendrite exhibit different growth patterns.展开更多
基金grant from Institute of Crustal Dynamics, China Earthquake Administration (No. ZDJ2011 - 01) and (No. ZDJ2010 - 26)
文摘On the basis of the earthquake （gL I〉3.0） catalog in North China from 1970 to 2009, the pattern of temporal and spatial distribution of medium-small earthquakes in Datong and its surrounding areas is studied by correlation analysis with a focus on its anomaly before moderate and strong earthquakes. With different spatial scales, temporal scales and time steps, the spatial distribution of earthquakes is converted to a sequence, then the correlation coefficients between the spatial distribution of medium-small earthquakes in a long-term and a longer time are calculated for the analysis of anomalies before moderate and strong earthquakes. In the study region center on the epicenter of the 1989 Datong- Yanggao earthquake （Ms5. 9） within a radius of less than 0.8~, with the time length of 3600 days, the longer time length of 3700 days, and the time step of 100 days, the correlation coefficient from 1980 to 2009 is steady between 0.94 and 1.00, but there were anomalies with values less than 0. 94 in the 2 years before the 1989 Datong-Yanggao earthquake （Ms 5.9）, the 1991 Datong earthquake （ Ms 5.8） and 1999 Hunyuan earthquake （Ms 5. 6 ）, which indicates the spatial distribution of a medium-small earthquake is very different from steady background seismicity. The implication for earthquake prediction from the anomaly of the correlation coefficient is also discussed with the three conclusions： （1） Before moderate and strong earthquakes in Datong and its surrounding areas, the obvious change of spatial distribution patterns of medium-small earthquake can be a kind of seismic precursor of the 2-year time scale for the prediction of an earthquake＇s time. （2） As the study region is restricted within a radius of less than 0. 8~, the result of correlation analysis is also good for the prediction of an earthquake＇s location. （3） The method of correlation analysis in this paper helps recognize the anomaly of spatial distribution of medium-small earthquake.
基金supported by the National Natural Science Foundation of China (Grant No. 51079089)Key Project of the National Twelfth-Five Year Research Program of China (Grant No.2012BAC06B04)the Ecological and Environmental Monitoring Programs of China Three Gorges Project Corporation (Grant Nos. 241202004and SXSN/2726)
文摘An explicit demonstration of the changes in fish assemblages is required to reveal the influence of damming on fish species.However,information from which to draw general conclusions regarding changes in fish assemblages is insufficient because of the limitations of available approaches.We used a combination of acoustic surveys,gillnet sampling,and geostatistical simulations to document the spatiotemporal variations in the fish assemblages downstream of the Gezhouba Dam,before and after the third impoundment of Three Gorges Reservoir(TGR).To conduct a hydroacoustic identification of individual species,we matched the size distributions of the fishes captured by gillnet with those of the acoustic surveys.An optimum threshold of target strength of 50 dB re 1 m 2 was defined,and acoustic surveys were purposefully extended to the selected fish assemblages(i.e.,endemic Coreius species) that was acquired by the size and species selectivity of the gillnet sampling.The relative proportion of fish species in acoustic surveys was allocated based on the composition(%) of the harvest in the gillnet surveys.Geostatistical simulations were likewise used to generate spatial patterns of fish distribution,and to determine the absolute abundance of the selected fish assemblages.We observed both the species composition and the spatial distribution of the selected fish assemblages changed significantly after implementation of new flow regulation in the TGR,wherein an immediate sharp population decline in the Coreius occurred.Our results strongly suggested that the new flow regulation in the TGR impoundment adversely affected downstream fish species,particularly the endemic Coreius species.To determine the factors responsible for the decline,we associated the variation in the fish assemblage patterns with changes in the environment and determined that substrate erosion resulting from trapping practices in the TGR likely played a key role.
基金supported by the National Natural Science Foundation of China (Grant Nos.61078057 and 51172183)NPU Foundation for Fundamental Research (Grant Nos.NPU-FFR-JC201048 and JC201155)+1 种基金the Science & Technology Program of Shanghai Maritime University (Grant No.20110054)the Project of the Excellent Youth of Shanghai (WANG CaiFang)
文摘Morphological evolution of the solid-liquid interface near grain boundaries has been studied during directional solidification of succinonitrile-based transparent alloys (SCN-0.9wt%DCB). Experimental results show that the grain boundary provides the starting point of morphological instability of the solid-liquid interface. The initial perturbation near the grain boundary is significantly larger than other perturbations on the interface. The initial shape of the interface and the competition between the thermal direction and preferred crystalline orientations determine the subsequent growth pattern selections. The temporal variations of the curvature radius of cell/ridge tips near the grain boundary have also been studied when the instability occurs. This process is divided into three parts. As the pulling velocity increases, dendrites at the grain boundary grow in two different directions to form a bicrystal microstructure. Side branches on either side of the dendrite exhibit different growth patterns.
