To find the distribution patterns of dynamic amplification coefficients for dams subjected to earthquake, 3D seismic responses of concrete-faced rockfill dams with different heights and different shapes of river valle...To find the distribution patterns of dynamic amplification coefficients for dams subjected to earthquake, 3D seismic responses of concrete-faced rockfill dams with different heights and different shapes of river valley were analyzed by using the equivalent-linear model. Statistical analysis was also made to the seismic coefficient, and an empirical formula for calculating the maximum acceleration was provided. The results indicate that under the condition of the same dam height and the same base acceleration excitations, with the increase of the river valley width, the position of the maximum acceleration on the axis of the top of the dam moves from the center to the riversides symmetrically. For the narrow valleys, the maximum acceleration occurs in the middle of the axis at the top of the dam; for wide valleys the maximum acceleration appears near the riversides. The result negates the application of 2D dynamical computation for wide valleys, and shows that for the seismic response of high concrete-faced rockfill dams, the seismic coefficient along the axis should be given, except for that along the dam height. Seismic stability analysis of rockfill dams using pseudo-static method can be modified according to the formula.展开更多
Synthetic aperture radar （SAR） systems have become an important tool for fine-resolution mapping and other remote sensing operations. The multi-channel SAR ground moving-target indication （GMTI） must process its d...Synthetic aperture radar （SAR） systems have become an important tool for fine-resolution mapping and other remote sensing operations. The multi-channel SAR ground moving-target indication （GMTI） must process its data to produce not only the image of surveillance area but also the information of the ground moving-targets. The topic of moving-target detection in clutter has been extensively studied, and there are many methods that are used to detect moving targets, such as displaced phase center antenna （DPCA） method, along-track interfero-metric （ATI） phase, space-time adaptive processing （STAP）, or some other metrics. A canonical framework is proposed that encompasses all the multi-channel SAR-GMT methods, namely, DPCA and ATI. The statistical test metric for multi-channel SAR-GMTI is established in a simple form, via the definition of the complex central Wishart distribution, to deduce the statistics of the test metric, and the probability distribution of the test metric for multichannel SAR-GMTI has the complex central Wishart distribution of 1×1 case, namely the X^2 distribution. The theory foundation offers the possibility to construct the united multi-channel SAR-GMTI detector, and derives the constant false alarm rate （CFAR） detector tests for separating moving targets from clutter.展开更多
Crocuta and Pachycrocuta are widely regarded as the most prevalent and emblematic hyenas across Eurasia during Quaternary.They are easily distinguished by their distinctive carnassial teeth.However,the disparities in ...Crocuta and Pachycrocuta are widely regarded as the most prevalent and emblematic hyenas across Eurasia during Quaternary.They are easily distinguished by their distinctive carnassial teeth.However,the disparities in non-carnassial elements are less pronounced and have received minimal attention in previous studies.This has resulted in erroneous identifications when dealing with fragmented specimens,particularly in cases where carnassial teeth are poorly preserved or absent.Such misidentifications have the potential to give rise to erroneous inferences regarding the paleozoogeography and biochronology of the animals in question.The bone-cracking hyena specimens from Huainan,Anhui(Tseng et al.,2008)are re-examined and re-evaluated here through a series of morphological comparisons and data analyses(univariate,bivariate,and multivariate analyses etc.).The results provide unequivocal confirmation that the specimens from Xiliexi are not spotted hyenas,but belong to Pachycrocuta perrieri instead.Conversely,the specimen from Dadingshan is the only genuine representative of the spotted hyena,which is supposed to be a possible earliest fossil record for Crocuta ultima thus far in China.Furthermore,the disparities in dentognathic morphology between Crocuta and Pachycrocuta are systematically summarized and analyzed,with an explanation of their eco-functional significance.The present study hypothesizes that Pachycrocuta retains a certain degree of active predatory capability,attributable to the robustness of the canine and the symphysis of the jaw,among other factors.This finding indicates that Pachycrocuta exhibits a form of flexible foraging behavior,combining opportunistic scavenging and active hunting in a manner analogous to Crocuta.Finally,the dynamic evolutionary history of hyenas in East China since Pleistocene has also been broadly reconstructed.展开更多
基金Project(90815024) supported by the National Natural Science Foundation of China
文摘To find the distribution patterns of dynamic amplification coefficients for dams subjected to earthquake, 3D seismic responses of concrete-faced rockfill dams with different heights and different shapes of river valley were analyzed by using the equivalent-linear model. Statistical analysis was also made to the seismic coefficient, and an empirical formula for calculating the maximum acceleration was provided. The results indicate that under the condition of the same dam height and the same base acceleration excitations, with the increase of the river valley width, the position of the maximum acceleration on the axis of the top of the dam moves from the center to the riversides symmetrically. For the narrow valleys, the maximum acceleration occurs in the middle of the axis at the top of the dam; for wide valleys the maximum acceleration appears near the riversides. The result negates the application of 2D dynamical computation for wide valleys, and shows that for the seismic response of high concrete-faced rockfill dams, the seismic coefficient along the axis should be given, except for that along the dam height. Seismic stability analysis of rockfill dams using pseudo-static method can be modified according to the formula.
基金the National Natural Science Foundation of China (60472097 and 60502054)
文摘Synthetic aperture radar （SAR） systems have become an important tool for fine-resolution mapping and other remote sensing operations. The multi-channel SAR ground moving-target indication （GMTI） must process its data to produce not only the image of surveillance area but also the information of the ground moving-targets. The topic of moving-target detection in clutter has been extensively studied, and there are many methods that are used to detect moving targets, such as displaced phase center antenna （DPCA） method, along-track interfero-metric （ATI） phase, space-time adaptive processing （STAP）, or some other metrics. A canonical framework is proposed that encompasses all the multi-channel SAR-GMT methods, namely, DPCA and ATI. The statistical test metric for multi-channel SAR-GMTI is established in a simple form, via the definition of the complex central Wishart distribution, to deduce the statistics of the test metric, and the probability distribution of the test metric for multichannel SAR-GMTI has the complex central Wishart distribution of 1×1 case, namely the X^2 distribution. The theory foundation offers the possibility to construct the united multi-channel SAR-GMTI detector, and derives the constant false alarm rate （CFAR） detector tests for separating moving targets from clutter.
文摘Crocuta and Pachycrocuta are widely regarded as the most prevalent and emblematic hyenas across Eurasia during Quaternary.They are easily distinguished by their distinctive carnassial teeth.However,the disparities in non-carnassial elements are less pronounced and have received minimal attention in previous studies.This has resulted in erroneous identifications when dealing with fragmented specimens,particularly in cases where carnassial teeth are poorly preserved or absent.Such misidentifications have the potential to give rise to erroneous inferences regarding the paleozoogeography and biochronology of the animals in question.The bone-cracking hyena specimens from Huainan,Anhui(Tseng et al.,2008)are re-examined and re-evaluated here through a series of morphological comparisons and data analyses(univariate,bivariate,and multivariate analyses etc.).The results provide unequivocal confirmation that the specimens from Xiliexi are not spotted hyenas,but belong to Pachycrocuta perrieri instead.Conversely,the specimen from Dadingshan is the only genuine representative of the spotted hyena,which is supposed to be a possible earliest fossil record for Crocuta ultima thus far in China.Furthermore,the disparities in dentognathic morphology between Crocuta and Pachycrocuta are systematically summarized and analyzed,with an explanation of their eco-functional significance.The present study hypothesizes that Pachycrocuta retains a certain degree of active predatory capability,attributable to the robustness of the canine and the symphysis of the jaw,among other factors.This finding indicates that Pachycrocuta exhibits a form of flexible foraging behavior,combining opportunistic scavenging and active hunting in a manner analogous to Crocuta.Finally,the dynamic evolutionary history of hyenas in East China since Pleistocene has also been broadly reconstructed.
