检索结果-南通市图书馆

Simulation of radar sounder echo from lunar surface and subsurface structure

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2010年第7期53卷 1043-1055页

作者： wenzhe Fa yaqiu {2. Fudan Univ Key Lab Wave Scattering & Remote Sensing Informat MOE Shanghai 200433 Peoples R China

Space-borne high frequency (HF) radar sounder is an effective tool for investigation of lunar subsurface structure in lunar exploration. The primary strategy of radar sounder technology for subsurface structure detection is utilization of the nadir echoes time delay and intensity difference from the lunar surface and subsurface. It is important to fully understand electromagnetic wave propagation, scattering, and attenuation through the lunar media in order to retrieve information of lunar layering structure from weak nadir echoes of the subsurface, which is simultaneously interfered by strong off-nadir surface clutters. Based on the Kirchhoff approximation (KA) of rough surface scattering and the ray tracing of geometric optics, a numerical simulation of radar echoes from lunar layering structures is developed. According to the lunar surface feature, the topography of mare and highland surfaces is numerically generated, and the triangulated network is employed to make digital elevations of the whole lunar surface. Scattering from the lunar surface and subsurface is numerically calculated using KA approach. Radar echoes and its range images are numerically simulated, and their dependence on the parameters of lunar layering interfaces is discussed. The approach of this paper can also be utilized to investigate subsurface structures in Mars and other planetary exploration.

关键词： radar sounder lunar layering structure echo simulation and image

The modeling analysis of microwave emission from stratified media of non-uniform lunar cratered terrain surface for Chinese Chang-E1 observation

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2011年第11期56卷 1165-1171页

作者： jin yaqiu FA {2. Key Laboratory of Wave Scattering and Remote Sensing Information (MOE) Fudan University Shanghai 200433 China

In China's first lunar exploration project,Chang-E 1,the multi-channel (3.0,7.8,19.35,37 GHz) microwave radiometers were aboard the satellite,with the purpose of measuring microwave brightness temperature from lunar surface and surveying the global distribution of lunar regolith layer thickness,and global evaluation of 3He *** analyze the modeling of microwave radiative transfer from three-layered media of lunar surface,some factors,such as the cratered lunar surface roughness,scattering of regolith particulate medium with temperature profile,are *** on the statistics of the lunar cratered terrain and using Monte Carlo (MC) method,the cratered lunar surfaces are numerically *** triangulated network is utilized to divide the undulated lunar surface into discrete triangle meshes with the size 10 m as a digital surface *** reflectivities of each plane mesh are calculated,and the average reflectivity for all MC-realized lunar surfaces is *** is found that under the spatial resolution of 30 km×30 km of Chang-E 1 radiometer observation,the lunar surface can be well modeled as a flat *** makes the predominance of the parameters,such as the regolith layer thickness and stratified structures,to be *** the radiative transfer equation of stratified media with dense scatterers,the scattering coefficient of the regolith particulate medium is found negligible,and the emission is mainly governed by the absorptive property of the *** temperature of multi-layered media,*** soil,regolith layer with temperature profile and underlying rock media,are derived and calculated,and relevant main factors to affect the modeling and emission simulation are analyzed.

关键词：月球探测工程微波发射分层介质地形表面陨石坑模型分析中国非均匀

Global inventory of Helium-3 in lunar regoliths estimated by a multi-channel microwave radiometer on the Chang-E 1 lunar satellite

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2010年第35期55卷 4005-4009页

作者： FA wenzhe jin {2. Key Laboratory of Wave Scattering and Remote Sensing Information (MOE) Fudan University Shanghai 200433 China Institut de Physique du Globe de Paris Saint Maur des Fosses 94100 France

Helium-3(3He) implanted by solar wind in the lunar regolith is a valuable resource because of its potential as a fusion *** the basis of the Apollo regolith samples,a linear relationship between 3He abundance and solar wind flux,optical maturity and TiO2.content has been *** successfully launched its first lunar exploration satellite Chang-E 1(CE-1) on October 2.,2.07.A multi-channeled microwave radiometer was aboard the satellite with the purpose of measuring microwave thermal emission from the lunar surface *** the multi-channel brightness temperature(Tb) observed by CE-1,the global distribution of the regolith thickness was inverted from the multi-channel Tb,and was used to evaluate the total amount of 3He per unit area in the lunar *** global inventory of 3He was estimated as being 6.6×108 kg;3.7×108 kg for the lunar nearside and 2.9×108 kg for the lunar farside.

关键词：微波辐射计月球卫星氦-3 库存估计多通道月球探测卫星聚变燃料

SAR imaging simulation for an inhomogeneous undulated lunar surface based on triangulated irregular network

在线全文

学校读者我要写书评

暂无评论

Science in China(Series F) 2009年第4期52卷 559-574页

作者： FA wenzhe XU Feng jin {2. Key Laboratory of Wave Scattering and Remote Sensing Information (MoE) Fudan University Shanghai 200433 China

Based on the statistics of the lunar cratered terrain, e.g., population, dimension and shape of craters, the terrain feature of cratered lunar surface is numerically generated. According to the inhomogeneous distribution of the lunar surface slope, the triangulated irregular network （TIN） is employed to make the digital elevation of lunar surface model. The Kirchhoff approximation of surface scattering is then applied to simulation of lunar surface scattering. The synthetic aperture radar （SAR） image for compre- hensive cratered lunar surface is numerically generated using back projection （BP） algorithm of SAR imaging. Making use of the digital elevation and Clementine UVVIS data at Apollo 15 landing site as the ground truth, an SAR image at Apollo 15 landing site is simulated. The image simulation is verified using real SAR image and echoes statistics.

关键词： cratered terrain triangulated irregular network SAR imaging back projection

Calibration of the space-borne microwave humidity sounder based on real-time thermal emission from lunar surface

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2021年第3期64卷 494-502页

作者： Niutao LIU yaqiu jin Key Laboratory of Information Science of Electromagnetic Waves(MoE) Fudan UniversityShanghai200433China

Calibration is a key issue for quantitative application of meteorological satellite data. The complex space environment may cause many uncertainties in data calibration. A highly stable and reliable calibrator in flight is needed. Because the Moon has no atmosphere and no environmental variation, the physical and chemical properties of its surface are stable in the long term. The Moon might be an ideal candidate for in-flight thermal calibration. In advanced satellite-borne microwave remote sensing such as NOAA-18, the deep space view(DSV) of the microwave humidity sounder(MHS) has viewed the Moon many times every *** the thermal-physical properties of the lunar regolith derived from the Diviner infrared(IR) brightness temperature(TB) data,we solve the one-dimensional heat conduction equation to obtain the temperature profile of the near side of the lunar regolith medium. The loss tangents of the regolith medium are retrieved from microwave TB data of the Chinese satellite Chang’e-2. The integrated radiative transfer equation is used to simulate the weighted disk-average TB of the lunar surface for the MHS channels at89, 157, and 183 GHz for the year 2.11. The Moon is taken as an extended circular target. The simulated TBs are used to correct the full width at half maximum(FWHM) fitted with the MHS counts. We analyze the influences of the distance between the satellite and the Moon, the lunar phase angle, and the FWHM of the radiometer on the inverted FWHM. The corrected TB data are compared with the simulation. This paper presents a new method for thermal calibration of spaceborne in-flight microwave and millimeter-wave radiometers with the weighted disk-average TB of the lunar surface.

关键词： Microwave humidity sounder Tb calibration Thermal emission of lunar surface FWHM

Numerical simulation of bistatic scattering from a target at low altitude above rough sea surface under an EM wave incidence at low grazing angle by using the finite element method

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2004年第3期47卷 293-304页

作者： LIU Peng jin yaqiu The Key Laboratory of Wave Scattering and Remote Sensing Information Ministry of Education Fudan University Shanghai 200433 China The Key Laboratory of Wave Scattering and Remote Sensing Information Ministry of Education Fudan University Shanghai 200433 China

To study bistatic scattering from a target at low altitude above two- dimensional (2.) randomly rough sea surface under an electromagnetic (EM) wave incidence at low grazing angle (LGA), a numerical approach of the finite element method (FEM) is developed. The conformal perfectly matched layer (PML), as the truncation boundary of the FEM, is employed to reduce the reflection error of planar PML in conventional FEM. Numerical code of our FEM is examined by available solution of the forward backward iterative (FBM) method. Bistatic and back-scattering from composite model of a target above random rough sea surface generated by Monte Carlo realization, and functional dependence upon the sea surface wind speed, target altitude, incident and scattering angles, etc. are numerically simulated and discussed. This paper presents a numerical description of the observation principle and physical insight associated with the coupling interactions of a complex volumetric target and random rough sea surface.

关键词： rough surface, low altitude target, EM scattering, LGA, FEM, PML.

Numerical simulation of the EM scattering and Doppler spectrum of a low flying target above dynamic oceanic surface by using the FEMDDM method

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2004年第5期47卷 597-611页

作者： LIU Peng jin yaqiu Key Laboratory of Wave Scattering and Remote Sensing Information Ministry of Education Fudan University Shanghai 200433 China Key Laboratory of Wave Scattering and Remote Sensing Information Ministry of Education Fudan University Shanghai 200433 China

To study the Doppler (DP) spectrum of a flying target above the dynamic oceanic surface, a two-level quasi-stationary algorithm (TLQSA) of the finite element method (FEM) with domain decomposition (DDM) is developed. The DP spectrum of a fast-moving target requires a small time-sampling rate. At most time steps, scattering from the flying target is solved by the FEM solution in only one sub-domain; meanwhile the interactions between the target and rough sea surface in other sub-domains are obtained by solving the global DDM coupling matrices. The slowly moving sea surface is evolved at a larger time step and the DP of oceanic clutter is obtained through all-subdomain FEM calculation. Numerical simulations of the DP spectrum from a target flying above the dynamic oceanic surface with and without a ship presence are obtained. The functional dependence of the DP spectrum in both the time and frequency domains upon the sea surface wind speed, target altitude, observation angle etc. are demon- strated and discussed.

关键词： Doppler spectrum, rough surface and target, electromagnetic scattering, domain decomposition method, finite element method.

Fast iterative approach to the difference scattering from a dielectric target above a rough surface

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2005年第6期48卷 723-738页

作者： YE Hongxia jin yaqiu Key Laboratory of Wave Scattering and Remote Sensing Information Education Ministry of China Fudan University Shanghai 200433 China Key Laboratory of Wave Scattering and Remote Sensing Information Education Ministry of China Fudan University Shanghai 200433 China

The difference field RCS (d-RCS) has been defined to analyze the scattering from the target above a rough surface. The electric field integral equations (EFIEs) of the difference induced current Jsd on the rough surface, the induced electric current Jo and magnetic current Ko on the dielectric target under a TE wave incidence are derived. A small portion of the rough surface towards the target along the specular direction is taken to compute the scattering contribution Es0 from the rough surface towards the target, which improves the computation speed. A numerical iterative approach is developed to solve the EFIEs and bistatic d-RCS. The surface length for iterations is dependent on the scattering angle and discussed for comparison with Johnson’s method. Using the Monte-Carlo method to generate the Pierson-Morkowitz (P-M) ocean-like rough surface, bistatic d-RCS of the dielectric target, e.g. a cylinder or a square column, above the rough surface is numerically simulated. The induced electric and magnetic currents on the dielectric target and the difference induced current on the rough surface are numerically discussed.

关键词： dielectric target, rough surface, difference scattering, iterative method.

西宁市丁香属植物小枝茎构型对展叶效率的影响

在线全文

学校读者我要写书评

暂无评论

生态学杂志 2024年第2期43卷 424-432页

作者：鲁进李峥冯真周文哲王立陈国鹏甘肃农业大学林学院兰州730070 中铁第一勘察设计院集团有限公司西安710043

小枝茎的大小影响着着生其上的叶片数量和大小,探究小枝茎构型与展叶效率间的关系对认识植物资源利用策略具有重要意义。本研究以西宁市火烧沟9种丁香属(Syringa spp.)植物为材料,以小枝基径、茎长和生物量表征茎构型,以展叶系数、叶片... 详细信息

小枝茎的大小影响着着生其上的叶片数量和大小,探究小枝茎构型与展叶效率间的关系对认识植物资源利用策略具有重要意义。本研究以西宁市火烧沟9种丁香属(Syringa spp.)植物为材料,以小枝基径、茎长和生物量表征茎构型,以展叶系数、叶片密度、总叶面积、平均单叶面积表征展叶效率,分析了丁香属植物茎构型与展叶效率间的关系。结果表明:9种丁香属植物小枝茎构型和展叶效率关系的种间差异明显,茎长基径和茎生物量能更好地反映小枝茎构型对展叶效率的影响;随着茎长的增加,小枝展叶系数和叶片密度呈降低趋势、总叶面积和平均单叶面积呈增加趋势,但这种影响的强度在不同物种间存在差异。小枝茎长显著影响展叶效率,同属异源植物在适应高寒环境过程中存在明显的策略分化。

关键词：植物小枝叶面积展叶效率茎长丁香属植物