Inertial navigation and attitude initialization in polar areas become a hot topic in recent years in the navigation community,as the widely-used navigation mechanization of the local level frame encounters the inheren...Inertial navigation and attitude initialization in polar areas become a hot topic in recent years in the navigation community,as the widely-used navigation mechanization of the local level frame encounters the inherent singularity when the latitude approaches 90°.Great endeavors have been devoted to devising novel navigation mechanizations such as the grid or transversal frames.This paper highlights the fact that the common Earth-frame mechanization is sufficiently good to handle the singularity problem in polar areas.Simulation results are reported to demonstrate the singularity problem and the effectiveness of the Earth-frame mechanization.展开更多
The polar surface area of a molecule is currently defined as the surface sum over all polar atoms, primarily oxygen and nitrogen, also including their attached hydrogens (named PSA1 in the present study). Some authors...The polar surface area of a molecule is currently defined as the surface sum over all polar atoms, primarily oxygen and nitrogen, also including their attached hydrogens (named PSA1 in the present study). Some authors also include sulfur and phosphor (PSA3). The slight modification suggested here is based on the fact that it is difficult to consider, on a theoretical point of view, hexavalent S and pentavalents N and P as polar atoms. Indeed, in these cases, all their peripheral electrons are involved in bondings. We propose to define PSA2 using the initial definition extended to O, S, N, P, with the exception of hexavalent S and pentavalents N and P. In order to test this hypothesis, the three expressions PSA1, PSA2 and PSA3 have been applied in a QSAR to a physiological phenomenon called comfort olfactory perceived intensity, for the human responses to 186 odorants (QSAR stands for Quantitative Structure Activity Relationship). The PSA2 expression has been selected as the more suitable, associated with two other molecular properties (molar refraction and Van der Waals molecular volume).展开更多
当干扰信号的空域和极化域特征与目标信号相似时,采用空极化域联合抗干扰技术在消除干扰的同时也会抑制目标信号,导致干扰对消后信干噪比(signal to interference plus noise ratio,SINR)低于雷达系统需求,从而形成干扰对消盲区。针对...当干扰信号的空域和极化域特征与目标信号相似时,采用空极化域联合抗干扰技术在消除干扰的同时也会抑制目标信号,导致干扰对消后信干噪比(signal to interference plus noise ratio,SINR)低于雷达系统需求,从而形成干扰对消盲区。针对这一现象,通过在空域、极化域与空极化域分别建立交替极化阵列对消盲区模型,推导了对消盲区位置和大小的数学表达式,从而给出了交替极化阵列对消盲区的数学表征方法。进而分析了交替极化阵列对消盲区的分布规律与影响因素,研究发现阵元间距能够显著影响交替极化阵列对消盲区的分布,在相同条件下交替极化阵列对消盲区大于共点极化阵列对消盲区,结果表明交替极化阵列虽然通过减少天线数目降低了设备成本,但增大了阵列的对消盲区。然后,对消盲区模型进行了数值仿真,仿真结果验证了理论分析。最后,利用信道模拟器搭建了实验平台,信道模拟实验测得的对消盲区与理论值基本一致,再次证明了分析结论的有效性。展开更多
In polar regions, cloud and underlying ice-snow areas are difficult to distinguish in satellite images because of their high albedo in the visible band and low surface temperature of ice-snow areas in the infrared ban...In polar regions, cloud and underlying ice-snow areas are difficult to distinguish in satellite images because of their high albedo in the visible band and low surface temperature of ice-snow areas in the infrared band. A cloud detection method over ice-snow covered areas in Antarctica is presented. On account of different texture features of cloud and ice-snow areas, five texture features are extracted based on GLCM. Nonlinear SVM is then used to obtain the optimal classification hyperplane from training data. The experiment results indicate that this algorithm performs well in cloud detection in Antarctica, especially for thin cirrus detection. Furthermore, when images are resampled to a quarter or 1/16 of the full size, cloud percentages are still at the same level, while the processing time decreases exponentially.展开更多
The relationship between the specific surface area（SSA） of rust and the electrochemical behavior of rusted steel under wet-dry acid corrosion conditions was investigated. The results showed that the corrosion curren...The relationship between the specific surface area（SSA） of rust and the electrochemical behavior of rusted steel under wet-dry acid corrosion conditions was investigated. The results showed that the corrosion current density first increased and then decreased with increasing SSA of the rust during the corrosion process. The structure of the rust changed from single-layer to double-layer, and the γ-FeOOH content decreased in the inner layer of the rust with increasing corrosion time; by contrast, the γ-FeOOH content in the outer layer was constant. When the SSA of the rust was lower than the critical SSA corresponding to the relative humidity during the drying period, condensed water in the micropores of the rust could evaporate, which prompted the diffusion of O_2 into the rust and the following formation process of γ-FeOOH, leading to an increase of corrosion current density with increasing corrosion time. However, when the SSA of the rust reached or exceeded the critical SSA, condensate water in the micro-pores of the inner layer of the rust could not evaporate which inhibited the diffusion of O_2 and decreased the γ-FeOOH content in the inner rust, leading to a decrease of corrosion current density with increasing corrosion time.展开更多
Despite the development of information and communication technologies, mobility still remains an important factor in the development of the social capital, by promoting social interactions. However, rural African popu...Despite the development of information and communication technologies, mobility still remains an important factor in the development of the social capital, by promoting social interactions. However, rural African populations face more difficulties getting around than city dwellers. In addition, studies on mobility in Africa are relatively weak. In rural African areas, this ignorance of mobility is even more important. It is necessary to identify the characteristics and the spatial structure of mobility flows before starting any reflection on solutions, particularly in terms of spatial allocation of transport resources. Our main objective is to map the current movement flows in the Niakhar area. We chose to use the cartographic approach to analyze mobility flows. The data come from a survey carried out in 2018, as part of the French Institute of Research for Development (IRD) Niakhar Atlas project. For the data analysis, we used 4 methods: dominant flux method, net flux calculation method, directional mean statistics and areal interpolation. The results revealed differences in mobility behavior depending on the season and in space, and the existence of three dominant centers: Ngayokhème, Diohine and Toucar. They also made it possible to highlight the main directions of the flows and the scalar fields of mobility.展开更多
Based on the seismic data of near-field source from the Shandong Digital Seismic Network,this study obtained the shear-wave splitting parameters from multiple stations. The results show that dominant directions of pol...Based on the seismic data of near-field source from the Shandong Digital Seismic Network,this study obtained the shear-wave splitting parameters from multiple stations. The results show that dominant directions of polarizations of fast shear-waves reflect the spatial distribution characteristics of tectonic stress in this area,CHD and LIS stations show 2 dominant directions,and reveals that the crustal seismic anisotropy in the Shandong area is constrained by the regional stress background,local failure and structure.展开更多
文摘Inertial navigation and attitude initialization in polar areas become a hot topic in recent years in the navigation community,as the widely-used navigation mechanization of the local level frame encounters the inherent singularity when the latitude approaches 90°.Great endeavors have been devoted to devising novel navigation mechanizations such as the grid or transversal frames.This paper highlights the fact that the common Earth-frame mechanization is sufficiently good to handle the singularity problem in polar areas.Simulation results are reported to demonstrate the singularity problem and the effectiveness of the Earth-frame mechanization.
文摘The polar surface area of a molecule is currently defined as the surface sum over all polar atoms, primarily oxygen and nitrogen, also including their attached hydrogens (named PSA1 in the present study). Some authors also include sulfur and phosphor (PSA3). The slight modification suggested here is based on the fact that it is difficult to consider, on a theoretical point of view, hexavalent S and pentavalents N and P as polar atoms. Indeed, in these cases, all their peripheral electrons are involved in bondings. We propose to define PSA2 using the initial definition extended to O, S, N, P, with the exception of hexavalent S and pentavalents N and P. In order to test this hypothesis, the three expressions PSA1, PSA2 and PSA3 have been applied in a QSAR to a physiological phenomenon called comfort olfactory perceived intensity, for the human responses to 186 odorants (QSAR stands for Quantitative Structure Activity Relationship). The PSA2 expression has been selected as the more suitable, associated with two other molecular properties (molar refraction and Van der Waals molecular volume).
文摘当干扰信号的空域和极化域特征与目标信号相似时,采用空极化域联合抗干扰技术在消除干扰的同时也会抑制目标信号,导致干扰对消后信干噪比(signal to interference plus noise ratio,SINR)低于雷达系统需求,从而形成干扰对消盲区。针对这一现象,通过在空域、极化域与空极化域分别建立交替极化阵列对消盲区模型,推导了对消盲区位置和大小的数学表达式,从而给出了交替极化阵列对消盲区的数学表征方法。进而分析了交替极化阵列对消盲区的分布规律与影响因素,研究发现阵元间距能够显著影响交替极化阵列对消盲区的分布,在相同条件下交替极化阵列对消盲区大于共点极化阵列对消盲区,结果表明交替极化阵列虽然通过减少天线数目降低了设备成本,但增大了阵列的对消盲区。然后,对消盲区模型进行了数值仿真,仿真结果验证了理论分析。最后,利用信道模拟器搭建了实验平台,信道模拟实验测得的对消盲区与理论值基本一致,再次证明了分析结论的有效性。
基金Supported by the Antarctic Geography Information Acquisition and Environmental Change Research of China (No.14601402024-04-06).
文摘In polar regions, cloud and underlying ice-snow areas are difficult to distinguish in satellite images because of their high albedo in the visible band and low surface temperature of ice-snow areas in the infrared band. A cloud detection method over ice-snow covered areas in Antarctica is presented. On account of different texture features of cloud and ice-snow areas, five texture features are extracted based on GLCM. Nonlinear SVM is then used to obtain the optimal classification hyperplane from training data. The experiment results indicate that this algorithm performs well in cloud detection in Antarctica, especially for thin cirrus detection. Furthermore, when images are resampled to a quarter or 1/16 of the full size, cloud percentages are still at the same level, while the processing time decreases exponentially.
基金supported by the Fund of Polar Scientific Research(No.20080216) of State Ocean Administration, Chinaby Chinese Natural Science Foundation(No. 20407001,No.40701170)
基金the National Natural Science Foundation of China(Project No.51571027)for funding support
文摘The relationship between the specific surface area（SSA） of rust and the electrochemical behavior of rusted steel under wet-dry acid corrosion conditions was investigated. The results showed that the corrosion current density first increased and then decreased with increasing SSA of the rust during the corrosion process. The structure of the rust changed from single-layer to double-layer, and the γ-FeOOH content decreased in the inner layer of the rust with increasing corrosion time; by contrast, the γ-FeOOH content in the outer layer was constant. When the SSA of the rust was lower than the critical SSA corresponding to the relative humidity during the drying period, condensed water in the micropores of the rust could evaporate, which prompted the diffusion of O_2 into the rust and the following formation process of γ-FeOOH, leading to an increase of corrosion current density with increasing corrosion time. However, when the SSA of the rust reached or exceeded the critical SSA, condensate water in the micro-pores of the inner layer of the rust could not evaporate which inhibited the diffusion of O_2 and decreased the γ-FeOOH content in the inner rust, leading to a decrease of corrosion current density with increasing corrosion time.
文摘Despite the development of information and communication technologies, mobility still remains an important factor in the development of the social capital, by promoting social interactions. However, rural African populations face more difficulties getting around than city dwellers. In addition, studies on mobility in Africa are relatively weak. In rural African areas, this ignorance of mobility is even more important. It is necessary to identify the characteristics and the spatial structure of mobility flows before starting any reflection on solutions, particularly in terms of spatial allocation of transport resources. Our main objective is to map the current movement flows in the Niakhar area. We chose to use the cartographic approach to analyze mobility flows. The data come from a survey carried out in 2018, as part of the French Institute of Research for Development (IRD) Niakhar Atlas project. For the data analysis, we used 4 methods: dominant flux method, net flux calculation method, directional mean statistics and areal interpolation. The results revealed differences in mobility behavior depending on the season and in space, and the existence of three dominant centers: Ngayokhème, Diohine and Toucar. They also made it possible to highlight the main directions of the flows and the scalar fields of mobility.
基金sponsored by the Natural Science of Shandong Province(ZH2014DQ019)Earthquake Science and Technology Spark Plan(XH15026)+1 种基金Key Foundation Program of Earthquake Administration of Shandong Province(JJ1407Y)the Contract Program of Earthquake Administration of Shandong Province(15Y102)
文摘Based on the seismic data of near-field source from the Shandong Digital Seismic Network,this study obtained the shear-wave splitting parameters from multiple stations. The results show that dominant directions of polarizations of fast shear-waves reflect the spatial distribution characteristics of tectonic stress in this area,CHD and LIS stations show 2 dominant directions,and reveals that the crustal seismic anisotropy in the Shandong area is constrained by the regional stress background,local failure and structure.
