在分析地面测量大气下行辐射和地表发射率之间关系的基础上，给出了针对热红外高光谱数据温度与发射率分离过程中地表温度优化的相关性判据，提出了基于相关性的温度与发射率分离算法（the Correlation Based Temperature Emissivity Se...在分析地面测量大气下行辐射和地表发射率之间关系的基础上，给出了针对热红外高光谱数据温度与发射率分离过程中地表温度优化的相关性判据，提出了基于相关性的温度与发射率分离算法（the Correlation Based Temperature Emissivity Separation Algorithm，CBTES）。该算法利用大气下行辐射和地表发射率之间的相关性优化地表温度，进而获得地表发射率。基于模拟的热红外高光谱数据，对CBTES算法的精度进行分析，结果表明CBTES算法具有较高的温度与发射率反演精度；并与光谱迭代平滑温度发射率分离算法（ISSTES）进行比较，发现CBTES算法具有和ISSTES算法相当的精度。此外，CBTES算法具有一定的抗噪性，对测量过程中大气下行辐射的变化不敏感；对于非同温像元，当其发射率定义为r-emissivity时，其辐射温度是对波数缓慢变化的，假设在比较窄的光谱区间内辐射温度近似不变，可以用CBTES算法反演非同温像元在窄光谱区间内的等效温度，在714-1250cm^-1。光谱区间内多个窄光谱区间反演的等效温度可以较好的刻画非同温像元辐射温度的变化趋势。展开更多
China placed 2 scientific experiment satellites into preset orbits atop a LM-4B launch vehicle on Sept. 9, 2004. A LM-4B blasted off at 7:14 am from Taiyuan Satellite Launch Center in Shanxi Province. Sources from the...China placed 2 scientific experiment satellites into preset orbits atop a LM-4B launch vehicle on Sept. 9, 2004. A LM-4B blasted off at 7:14 am from Taiyuan Satellite Launch Center in Shanxi Province. Sources from the Xi'an Satellite Monitor and Control Center said that one satellite,展开更多
Acoustic emission tests were performed using a split Hopkinson pressure bar system(SHPB) on 50-mm-diameter bars of granite, limestone, sandstone and skarn. The results show that the amplitude distribution of hits is n...Acoustic emission tests were performed using a split Hopkinson pressure bar system(SHPB) on 50-mm-diameter bars of granite, limestone, sandstone and skarn. The results show that the amplitude distribution of hits is not well centralized around 50 d B, and that some hits with large amplitudes, usually larger than 70 d B, occur in the early stages of each test, which is different from the findings from static and low-loading-rate tests. Furthermore, the dominant frequency range of the recorded acoustic emission waveforms is between 300 k Hz and 500 k Hz, and frequency components higher than 500 k Hz are not significant. The hit with the largest values of amplitude, counts, signal strength, and absolute energy in each test, displays a waveform with similar frequency characteristics and greater correlation with the waveform obtained from the elastic input bar of the split Hopkinson pressure bar system compared with the waveforms of the other hits. This indicates that the hit with the largest values of amplitude, counts, signal strength, and absolute energy is generated by elastic wave propagation instead of fracture within the rock specimen.展开更多
The evolution of a molecular system excited above its ionization threshold depends on a number of parameters that include the nature of the excited states and their couplings to the various continua. The general natur...The evolution of a molecular system excited above its ionization threshold depends on a number of parameters that include the nature of the excited states and their couplings to the various continua. The general nature of the processes governing this evolution depends also essentially on the complexity of the molecule, more precisely on its size, density of states, and strength of the couplings among the various internal degrees of freedom. In this paper we address the question of the transition between autoionization that prevails in small molecules, and delayed ionization occurring in larger molecules or clusters. This transition is illustrated by autoionization of Na2 Rydberg states on one hand, delayed ionization in fullerene C60, and delayed detachment in small cluster anions on the other hand. All processes are studied in the case of nanosecond laser excitation, corresponding to a rather slow deposition of the internal energy.展开更多
A Direction Of Arrival(DOA) estimator based on the signal separation principle is introduced, and one of representative multidimensional estimators is established by introducing Matrix Operator projection signal steer...A Direction Of Arrival(DOA) estimator based on the signal separation principle is introduced, and one of representative multidimensional estimators is established by introducing Matrix Operator projection signal steering Vector Excision(MOVE) operation. Thanks to Alternating Separation (AS) technique, the multidimensional problem is transformed into a series of one-dimensional optimal ones. Furthermore, an equivalent simplified implementation of the AS is obtained. Finally the definiteness and uniqueness of the estimator are analyzed.展开更多
The hazard caused by the fragments of damaged structures is usually significant in acci-dental explosions or hostile blast events.A reliable and efficient method to estimate probable fragment size,velocity and launch ...The hazard caused by the fragments of damaged structures is usually significant in acci-dental explosions or hostile blast events.A reliable and efficient method to estimate probable fragment size,velocity and launch distance will be useful to assess and design countermeasures to mitigate the possible fragment hazards.This paper presents a numerical method for predicting the size and launch distance of the fragments caused by explosive damage of masonry wall.Numerical simulations with different scaled distances are carried out,and the statistical distribution functions of the fragment size and launch distance in terms of the scaled distance are derived.展开更多
文摘在分析地面测量大气下行辐射和地表发射率之间关系的基础上，给出了针对热红外高光谱数据温度与发射率分离过程中地表温度优化的相关性判据，提出了基于相关性的温度与发射率分离算法（the Correlation Based Temperature Emissivity Separation Algorithm，CBTES）。该算法利用大气下行辐射和地表发射率之间的相关性优化地表温度，进而获得地表发射率。基于模拟的热红外高光谱数据，对CBTES算法的精度进行分析，结果表明CBTES算法具有较高的温度与发射率反演精度；并与光谱迭代平滑温度发射率分离算法（ISSTES）进行比较，发现CBTES算法具有和ISSTES算法相当的精度。此外，CBTES算法具有一定的抗噪性，对测量过程中大气下行辐射的变化不敏感；对于非同温像元，当其发射率定义为r-emissivity时，其辐射温度是对波数缓慢变化的，假设在比较窄的光谱区间内辐射温度近似不变，可以用CBTES算法反演非同温像元在窄光谱区间内的等效温度，在714-1250cm^-1。光谱区间内多个窄光谱区间反演的等效温度可以较好的刻画非同温像元辐射温度的变化趋势。
文摘China placed 2 scientific experiment satellites into preset orbits atop a LM-4B launch vehicle on Sept. 9, 2004. A LM-4B blasted off at 7:14 am from Taiyuan Satellite Launch Center in Shanxi Province. Sources from the Xi'an Satellite Monitor and Control Center said that one satellite,
基金Projects(51204206,41272304,41372278) supported by the National Natural Science Foundation of ChinaProject(20110162120057) supported by Ph D Program Foundation of Ministry of Education ChinaProject(201012200232) supported by the Freedom Explore Program of Central South University,China
文摘Acoustic emission tests were performed using a split Hopkinson pressure bar system(SHPB) on 50-mm-diameter bars of granite, limestone, sandstone and skarn. The results show that the amplitude distribution of hits is not well centralized around 50 d B, and that some hits with large amplitudes, usually larger than 70 d B, occur in the early stages of each test, which is different from the findings from static and low-loading-rate tests. Furthermore, the dominant frequency range of the recorded acoustic emission waveforms is between 300 k Hz and 500 k Hz, and frequency components higher than 500 k Hz are not significant. The hit with the largest values of amplitude, counts, signal strength, and absolute energy in each test, displays a waveform with similar frequency characteristics and greater correlation with the waveform obtained from the elastic input bar of the split Hopkinson pressure bar system compared with the waveforms of the other hits. This indicates that the hit with the largest values of amplitude, counts, signal strength, and absolute energy is generated by elastic wave propagation instead of fracture within the rock specimen.
文摘The evolution of a molecular system excited above its ionization threshold depends on a number of parameters that include the nature of the excited states and their couplings to the various continua. The general nature of the processes governing this evolution depends also essentially on the complexity of the molecule, more precisely on its size, density of states, and strength of the couplings among the various internal degrees of freedom. In this paper we address the question of the transition between autoionization that prevails in small molecules, and delayed ionization occurring in larger molecules or clusters. This transition is illustrated by autoionization of Na2 Rydberg states on one hand, delayed ionization in fullerene C60, and delayed detachment in small cluster anions on the other hand. All processes are studied in the case of nanosecond laser excitation, corresponding to a rather slow deposition of the internal energy.
基金Partially supported by the National Natural Science Foundation of China(No.60372036), Natural Science Foundation of Shaanxi Province (2002F24) and Funds from the Information Industry Ministry of China (2002XK610039)
文摘A Direction Of Arrival(DOA) estimator based on the signal separation principle is introduced, and one of representative multidimensional estimators is established by introducing Matrix Operator projection signal steering Vector Excision(MOVE) operation. Thanks to Alternating Separation (AS) technique, the multidimensional problem is transformed into a series of one-dimensional optimal ones. Furthermore, an equivalent simplified implementation of the AS is obtained. Finally the definiteness and uniqueness of the estimator are analyzed.
基金Supported by the Australian Research Council (ARC,No.DP0774061)National Natural Science Foundation of China (No.50638030 and 50528808).
文摘The hazard caused by the fragments of damaged structures is usually significant in acci-dental explosions or hostile blast events.A reliable and efficient method to estimate probable fragment size,velocity and launch distance will be useful to assess and design countermeasures to mitigate the possible fragment hazards.This paper presents a numerical method for predicting the size and launch distance of the fragments caused by explosive damage of masonry wall.Numerical simulations with different scaled distances are carried out,and the statistical distribution functions of the fragment size and launch distance in terms of the scaled distance are derived.
