In this paper, on the basis of experimental data of two kinds of chemical explosions, the piston-pushing model of spherical blast-waves and the second-order Godunov-type scheme of finite difference methods with high i...In this paper, on the basis of experimental data of two kinds of chemical explosions, the piston-pushing model of spherical blast-waves and the second-order Godunov-type scheme of finite difference methods with high identification to discontinuity are used to the numerical reconstruction of part of an actual hemispherical blast-wave flow field by properly adjusting the moving bounary conditions of a piston. This method is simple and reliable. It is suitable to the evaluation of effects of the blast-wave flow field away from the explosion center.展开更多
The relationship between the earth stress field, earth surface displacement field and the gravity variation is deduced. Algorithms based on the boundary element method to compute the earth stress variation using the e...The relationship between the earth stress field, earth surface displacement field and the gravity variation is deduced. Algorithms based on the boundary element method to compute the earth stress variation using the earth surface displacement is discussed. The stress field variation in Jiashi region, Xinjiang, China is obtained from the GPS data observed in 1997 and 1998, respectively, and the relationship among the local stress field variation, seismic activities and fault tectonic activities is discussed.展开更多
Some geophysical parameters, such as those related to gravitation and the geomagnetic field, could change during solar eclipses. In order to observe geomagnetic fluctuations, geomagnetic measurements were carded out i...Some geophysical parameters, such as those related to gravitation and the geomagnetic field, could change during solar eclipses. In order to observe geomagnetic fluctuations, geomagnetic measurements were carded out in a limited time frame during the partial solar eclipse that occurred on 2011 January 4 and was observed in Canakkale and Ankara, Turkey. Additionally, records of the geomagnetic field spanning 24 hours, obtained from another observatory （in Iznik, Turkey）, were also analyzed to check for any peculiar variations. In the data processing stage, a polynomial fit, following the application of a running average routine, was applied to the geomagnetic field data sets. Geomagnetic field data sets indicated there was a characteristic decrease at the beginning of the solar eclipse and this decrease can be well-correlated with previous geomagnetic field measurements that were taken during the total solar eclipse that was observed in Turkey on 2006 March 29. The behavior of the geomagnetic field is also consistent with previous observations in the literature. As a result of these analyses, it can be suggested that eclipses can cause a shielding effect on the geomagnetic field of the Earth.展开更多
高亮度地表上空的气溶胶光学厚度(aerosol optical depth,AOD)反演对于城市大气环境监测和污染岛研究等具有重要意义。该文综合考虑像元的光谱特性和空间特性,提出了一种基于数据场模型(data field method,DFM)的AOD反演方法。该方法基...高亮度地表上空的气溶胶光学厚度(aerosol optical depth,AOD)反演对于城市大气环境监测和污染岛研究等具有重要意义。该文综合考虑像元的光谱特性和空间特性,提出了一种基于数据场模型(data field method,DFM)的AOD反演方法。该方法基于Landsat OLI数据,开展了南京市上空AOD的反演研究,并分析不同空间结构、数据场强度和下垫面特征对DFM方法的影响,最后与传统的深蓝算法和MOD04产品等进行了对比分析。结果表明:DFM反演结果与CE318太阳光度计观测数据的相关系数为0.936,均方根误差、平均绝对误差和相对平均偏差分别为0.151,0.120和1.139,平均相对误差和误差比分别为22.7%和72.7%,与地面实测数据具有较高的一致性。地表数据场强度高于12的区域,DFM算法具有较好的反演效果,且在夏春季反演效果优于秋冬季,在乡村、工业区等下垫面变化剧烈区域具有更好的反演效果。展开更多
Regarding the rapid compensation of the influence of the Earth＇ s disturbing gravity field upon trajectory calculation,the key point lies in how to derive the analytical solutions to the partial derivatives of the st...Regarding the rapid compensation of the influence of the Earth＇ s disturbing gravity field upon trajectory calculation,the key point lies in how to derive the analytical solutions to the partial derivatives of the state of burnout point with respect to the launch data.In view of this,this paper mainly expounds on two issues：one is based on the approximate analytical solution to the motion equation for the vacuum flight section of a long-range rocket,deriving the analytical solutions to the partial derivatives of the state of burnout point with respect to the changing rate of the finalstage pitch program;the other is based on the initial positioning and orientation error propagation mechanism,proposing the analytical calculation formula for the partial derivatives of the state of burnout point with respect to the launch azimuth.The calculation results of correction data are simulated and verified under different circumstances.The simulation results are as follows：（1） the accuracy of approximation between the analytical solutions and the results attained via the difference method is higher than 90%,and the ratio of calculation time between them is lower than 0.2%,thus demonstrating the accuracy of calculation of data corrections and advantages in calculation speed;（2） after the analytical solutions are compensated,the longitudinal landing deviation of the rocket is less than 20 m and the lateral landing deviation of the rocket is less than 10 m,demonstrating that the corrected data can meet the requirements for the hit accuracy of a long-range rocket.展开更多
地球重力场是开展地球相关科学研究中的一种重要物理场,获得高精度的地球重力场模型也是航天飞行器轨道精密测轨、定轨的关键。介绍了地球重力场模型的发展历程,以及地面跟踪卫星、卫星跟踪卫星等重力场反演数据的获取方法。论述了一种...地球重力场是开展地球相关科学研究中的一种重要物理场,获得高精度的地球重力场模型也是航天飞行器轨道精密测轨、定轨的关键。介绍了地球重力场模型的发展历程,以及地面跟踪卫星、卫星跟踪卫星等重力场反演数据的获取方法。论述了一种基于卫星轨道数据的能量法地球重力场模型反演方法,并推导了能量法地球重力场反演方程。采用龙格-库塔方法对仿真轨道数据进行积分,基于美国国家地理空间情报局发布的全球超高阶地球重力场模型(Earth gravitational model 2008,EGM2008),设计了重力场反演算法,反演解算了20阶地球重力场的球谐系数。将反演得到的重力场模型与背景重力场模型进行对比分析,反演算法的精度整体在10~(-16)的量级,反演结果达到了预期。展开更多
文摘In this paper, on the basis of experimental data of two kinds of chemical explosions, the piston-pushing model of spherical blast-waves and the second-order Godunov-type scheme of finite difference methods with high identification to discontinuity are used to the numerical reconstruction of part of an actual hemispherical blast-wave flow field by properly adjusting the moving bounary conditions of a piston. This method is simple and reliable. It is suitable to the evaluation of effects of the blast-wave flow field away from the explosion center.
基金State Natural Science Foundation of China !(49774214)the State Key Project !(96-913-07).
文摘The relationship between the earth stress field, earth surface displacement field and the gravity variation is deduced. Algorithms based on the boundary element method to compute the earth stress variation using the earth surface displacement is discussed. The stress field variation in Jiashi region, Xinjiang, China is obtained from the GPS data observed in 1997 and 1998, respectively, and the relationship among the local stress field variation, seismic activities and fault tectonic activities is discussed.
文摘Some geophysical parameters, such as those related to gravitation and the geomagnetic field, could change during solar eclipses. In order to observe geomagnetic fluctuations, geomagnetic measurements were carded out in a limited time frame during the partial solar eclipse that occurred on 2011 January 4 and was observed in Canakkale and Ankara, Turkey. Additionally, records of the geomagnetic field spanning 24 hours, obtained from another observatory （in Iznik, Turkey）, were also analyzed to check for any peculiar variations. In the data processing stage, a polynomial fit, following the application of a running average routine, was applied to the geomagnetic field data sets. Geomagnetic field data sets indicated there was a characteristic decrease at the beginning of the solar eclipse and this decrease can be well-correlated with previous geomagnetic field measurements that were taken during the total solar eclipse that was observed in Turkey on 2006 March 29. The behavior of the geomagnetic field is also consistent with previous observations in the literature. As a result of these analyses, it can be suggested that eclipses can cause a shielding effect on the geomagnetic field of the Earth.
文摘Regarding the rapid compensation of the influence of the Earth＇ s disturbing gravity field upon trajectory calculation,the key point lies in how to derive the analytical solutions to the partial derivatives of the state of burnout point with respect to the launch data.In view of this,this paper mainly expounds on two issues：one is based on the approximate analytical solution to the motion equation for the vacuum flight section of a long-range rocket,deriving the analytical solutions to the partial derivatives of the state of burnout point with respect to the changing rate of the finalstage pitch program;the other is based on the initial positioning and orientation error propagation mechanism,proposing the analytical calculation formula for the partial derivatives of the state of burnout point with respect to the launch azimuth.The calculation results of correction data are simulated and verified under different circumstances.The simulation results are as follows：（1） the accuracy of approximation between the analytical solutions and the results attained via the difference method is higher than 90%,and the ratio of calculation time between them is lower than 0.2%,thus demonstrating the accuracy of calculation of data corrections and advantages in calculation speed;（2） after the analytical solutions are compensated,the longitudinal landing deviation of the rocket is less than 20 m and the lateral landing deviation of the rocket is less than 10 m,demonstrating that the corrected data can meet the requirements for the hit accuracy of a long-range rocket.
文摘地球重力场是开展地球相关科学研究中的一种重要物理场,获得高精度的地球重力场模型也是航天飞行器轨道精密测轨、定轨的关键。介绍了地球重力场模型的发展历程,以及地面跟踪卫星、卫星跟踪卫星等重力场反演数据的获取方法。论述了一种基于卫星轨道数据的能量法地球重力场模型反演方法,并推导了能量法地球重力场反演方程。采用龙格-库塔方法对仿真轨道数据进行积分,基于美国国家地理空间情报局发布的全球超高阶地球重力场模型(Earth gravitational model 2008,EGM2008),设计了重力场反演算法,反演解算了20阶地球重力场的球谐系数。将反演得到的重力场模型与背景重力场模型进行对比分析,反演算法的精度整体在10~(-16)的量级,反演结果达到了预期。
