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Lunar surface potential and electric field
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作者 Lei Li Yi-Teng Zhang +1 位作者 Bin Zhou Yong-Yong Feng 《天文和天体物理学研究:英文版》 SCIE CAS CSCD 2019年第6期15-22,共8页
The Moon has no significant atmosphere, thus its surface is exposed to solar ultraviolet radiation and the solar wind. Photoemission and collection of the solar wind electrons and ions may result in lunar surface char... The Moon has no significant atmosphere, thus its surface is exposed to solar ultraviolet radiation and the solar wind. Photoemission and collection of the solar wind electrons and ions may result in lunar surface charging. On the dayside, the surface potential is mainly determined by photoelectrons, modulated by the solar wind;while the nightside surface potential is a function of the plasma distribution in the lunar wake. Taking the plasma observations in the lunar environment as inputs, the global potential distribution is calculated according to the plasma sheath theory, assuming Maxwellian distributions for the surface emitted photoelectrons and the solar wind electrons. Results show that the lunar surface potential and sheath scale length change versus the solar zenith angle, which implies that the electric field has a horizontal component in addition to the vertical one. By differentiating the potential vertically and horizontally, we obtain the global electric field. It is found that the vertical electric field component is strongest at the subsolar point,which has a magnitude of 1 V m-1. The horizontal component is much weaker, and mainly appears near the terminator and on the nightside, with a magnitude of several mV m-1. The horizontal electric field component on the nightside is rotationally symmetric around the wake axis and is strongly determined by the plasma parameters in the lunar wake. 展开更多
关键词 Moon-planets and SATELLITES surfaces-planets and SATELLITES FUNDAMENTAL parameters-planets and SATELLITES physical evolution
Verification of Fengyun-3D MWTS and MWHS Calibration Accuracy Using GPS Radio Occultation Data
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作者 Xueyan HOU Yang HAN +1 位作者 Xiuqing HU Fuzhong WENG 《气象学报:英文版》 SCIE CSCD 2019年第4期695-704,共10页
The newly launched Fengyun-3D(FY-3D)satellite carries microwave temperature sounder(MWTS)and microwave humidity sounder(MWHS),providing the global atmospheric temperature and humidity measurements.It is important to a... The newly launched Fengyun-3D(FY-3D)satellite carries microwave temperature sounder(MWTS)and microwave humidity sounder(MWHS),providing the global atmospheric temperature and humidity measurements.It is important to assess the in orbit performance of MWTS and MWHS and understand their calibration accuracy before using them in numerical weather prediction and many other applications such as hurricane monitoring.This study aims at quantifying the biases of MWTS and MWHS observations relative to the simulations from the collocated Global Positioning System(GPS)radio occultation(RO)data.Using the collocated FY-3C Global Navigation Satellite System Occultation Sounder(GNOS)RO data under clear-sky conditions as inputs to Community Radiative Transfer Model(CRTM),brightness temperatures and viewing angles are simulated for the upper level sounding channels of MWTS and MWHS.In order to obtain O–B statistics under clear sky conditions,a cloud detection algorithm is developed by using the two MWTS channels with frequencies at 50.3 and 51.76 GHz and the two MWHS channels with frequencies centered at 89 and 150 GHz.The analysis shows that for the upper air sounding channels,the mean biases of the MWTS observations relative to the GPS RO simulations are negative for channels 5–9,with absolute values<1 K,and positive for channels 4 and 10,with values<0.5 K.For the MWHS observations,the mean biases in brightness temperature are negative for channels 2–6,with absolute values<2.6 K and relatively small standard deviations.The mean biases are also negative for channels 11–13,with absolute values<1.3 K,but with relatively large standard deviations.The biases of both MWTS and MWHS show scan-angle dependence and are asymmetrical across the scan line.The biases for the upper air MWTS and MWHS sounding channels are larger than those previously derived for the Advanced Technology Microwave Sounder. 展开更多
关键词 SATELLITES Fengyun satellites microwave sounding CROSS-CALIBRATION radio occultation
基于卫星编队的空间碎片视觉高精度导航方法 预览
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作者 杨博 王浩帆 +1 位作者 苗峻 赵晓涛 《中国空间科学技术》 CSCD 北大核心 2019年第1期40-48,共9页
视觉方法被广泛应用于空间碎片这类和卫星之间没有任何通信的非合作目标导航。针对观测过程中视觉传感器的像差偏差引起位置不确定的问题,提出了利用卫星编队的立体视觉导航方法。首先,利用卫星编队构造了长基线的视觉传感器,通过Fishe... 视觉方法被广泛应用于空间碎片这类和卫星之间没有任何通信的非合作目标导航。针对观测过程中视觉传感器的像差偏差引起位置不确定的问题,提出了利用卫星编队的立体视觉导航方法。首先,利用卫星编队构造了长基线的视觉传感器,通过Fisher矩阵对系统的可观测性进行了分析,验证了系统是可观的;其次,对视觉传感器进行了误差分析,通过安排最优视差角,使多颗卫星的观测信息融合达到最优;最后,应用卫星编队的视觉导航方法对空间碎片进行了导航仿真验证。结果表明,基于卫星编队的视觉导航方法可以显著减小观测误差,精度能达到0.1 m量级,而且编队构形简单,易于工程实现。 展开更多
关键词 空间碎片 卫星编队 立体视觉 可观测性 高精度导航
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Detecting Intensity Evolution of the Western North Pacific Super Typhoons in 2016 Using the Deviation Angle Variance Technique with FY Data
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作者 Meng YUAN Wei ZHONG 《气象学报:英文版》 SCIE CSCD 2019年第1期104-114,共11页
This paper analyzes the complete lifecycle of super typhoons in 2016 in the western North Pacific(WNP) using the deviation angle variance technique(DAV-T). Based on the infrared images from Fengyun(FY) satellites, the... This paper analyzes the complete lifecycle of super typhoons in 2016 in the western North Pacific(WNP) using the deviation angle variance technique(DAV-T). Based on the infrared images from Fengyun(FY) satellites, the DAV-T enables quantification of the axisymmetry of tropical cyclones(TCs) by using the DAV values;and thus, it helps improve the capability of TC intensity estimation. Case analyses of Super Typhoons Lionrock and Meranti were performed to explore the distribution characteristics of the DAV values at the various stages of TC evolution. The results show that the minimum DAV values(i.e., map minimum values: MMVs) gradually decreased and their locations constantly approached the circulation center with enhancement of the TC organization;however, when a ring or disk structure was formed around a TC, significant changes in MMV locations were no longer observed. Nonetheless,when large-scale non-closed deep convective cloud clusters appeared at the early stage or the dissipation stage of the typhoon, the axisymmetry of the TC was poor and the MMV locations tended to lie in the most convective region rather than in the TC circulation center. Overall, the MMVs and their locations, respectively, exhibited a strong correlation with the TC intensity and circulation center, and the correlation increased as the TCs became stronger. Combined with the China Meteorological Administration BestTrack dataset(CMA-BestTrack), statistical analysis of all research samples reveals that the correlation coefficient between the MMVs and maximum surface wind speeds(Vmax) was –0.80;the root mean square error(RMSE) of relative distance between the MMV locations and TC centers was 140.3 km;and especially, when the samples below the tropical depression(TD) intensity were removed, the RMSE of the relative distance decreased dramatically to 95.0 km. The value and location of the MMVs could be used as important indicators for estimating TC intensity and center. 展开更多
关键词 deviation angle variance technique(DAV-T) AXISYMMETRY super TYPHOON Fengyun(FY) SATELLITES
Online scheduling of image satellites based on neural networks and deep reinforcement learning
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作者 Haijiao WANG Zhen YANG +1 位作者 Wugen ZHOU Dalin LI 《中国航空学报:英文版》 SCIE EI CAS CSCD 2019年第4期1011-1019,共9页
In the ‘‘Internet Plus' era, space-based information services require effective and fast image satellite scheduling. Most existing studies consider image satellite scheduling to be an optimization problem to sol... In the ‘‘Internet Plus' era, space-based information services require effective and fast image satellite scheduling. Most existing studies consider image satellite scheduling to be an optimization problem to solve with searching algorithms in a batch-wise manner. No real-time speed method for satellite scheduling exists. In this paper, with the idea of building a real-time speed method, satellite scheduling is remodeled based on a Dynamic and Stochastic Knapsack Problem(DSKP), and the objective is to maximize the total expected profit. No existing algorithm could be able to solve this novel scheduling problem properly. With inspiration from the recent achievements in Deep Reinforcement Learning(DRL) in video games, AlphaGo and dynamic controlling,a novel DRL-based method is applied to training a neural network to schedule tasks. The numerical results show that the method proposed in this paper can achieve relatively good performance with real-time speed and immediate respond style. 展开更多
关键词 DEEP REINFORCEMENT learning Dynamic SCHEDULING IMAGE SATELLITES Neural network Online SCHEDULING
Using multi-satellite microwave remote sensing observations for retrieval of daily surface soil moisture across China 预览
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作者 Ke Zhang Li-jun Chao +6 位作者 Qing-qing Wang Ying-chun Huang Rong-hua Liu Yang Hong Yong Tu Wei Qu Jin-yin Ye 《水科学与水工程:英文版》 EI CAS CSCD 2019年第2期85-97,共13页
The objective of this study was to retrieve daily composite soil moisture by jointly using brightness temperature observations from multiple operating satellites for near real-time application with better coverage and... The objective of this study was to retrieve daily composite soil moisture by jointly using brightness temperature observations from multiple operating satellites for near real-time application with better coverage and higher accuracy.Our approach was to first apply the single-channel brightness radiometric algorithm to estimate soil moisture from the respective brightness temperature observations of the SMAP,SMOS,AMSR2,FY3B,and FY3C satellites on the same day and then produce a daily composite dataset by averaging the individual satellite-retrieved soil moisture.We further evaluated our product,the official soil moisture products of the five satellites,and the ensemble mean (i.e.,arithmetic mean) of the five official satellite soil moisture products against ground observations from two networks in Central Tibet and Anhui Province,China.The results show that our product outperforms the individual released products of the five satellites and their ensemble means in the two validation areas.The root mean square error (RMSE ) values of our product were 0.06 and 0.09 m3/m3 in Central Tibet and Anhui Province,respectively.Relative to the ensemble mean of the five satellite products,our product improves the accuracy by 9.1% and 57.7% in Central Tibet and Anhui Province,respectively.This demonstrates that jointly using brightness temperature observations from multiple satellites to retrieve soil moisture not only improves the spatial coverage of daily observations but also produces better daily composite products. 展开更多
关键词 Soil moisture RETRIEVAL Passive microwave remote sensing Multiple SATELLITES Surface HYDROLOGY SMAP SMOS AMSR2 FY3B FY3C
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SPATIAL AND TEMPORAL DISTRIBUTION OF MESOSCALE CONVECTIVE VORTICES IN EAST CHINA AND THE WESTERN PACIFIC REGION
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作者 杨程 王元 +3 位作者 冀春晓 姜瑜君 王丽吉 康丽莉 《热带气象学报:英文版》 SCIE 2018年第2期185-198,共14页
A 16-parameter GEO Broadcast Ephemeris 预览
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作者 Zhongkai ZHANG Lan DU +3 位作者 Li LIU Feng HE Yu LU Peiyuan ZHOU 《测绘学报(英文版)》 2018年第1期46-52,共7页
Currently,the broadcast ephemerides used in GEOs are same as those of the MEOs and IGSOs in the BeiDou navigation constellation.However,a trade-off strategy,i.e.an orbital inclination of 5°rotation,is needed in t... Currently,the broadcast ephemerides used in GEOs are same as those of the MEOs and IGSOs in the BeiDou navigation constellation.However,a trade-off strategy,i.e.an orbital inclination of 5°rotation,is needed in the fitting algorithm to solve the ephemeris parameters as well as the user satellite position computation for GEOs.Based on the standard broadcast ephemerides,the representations of both the orbit and its perturbation were revised according to the second class of nonsingular orbital elements.In this research,a 16-parameter broadcast ephemeris is presented specifically for GEOs,and user satellite position computation formulas were derived correspondingly.Fit simulations show that the root of mean squares(RMS)of user range error(URE)with two hour and three hour data sets are better than 0.05 m and 0.1 m,respectively. 展开更多
关键词 GEO SATELLITES broadcast EPHEMERIS parameters NONSINGULAR ORBITAL elements perturbation user range error(URE)
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A global satellite survey of density plumes at river mouths and at other environments: Plume configurations, external controls, and implications for deep-water sedimentation 预览
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作者 SHANMUGAM G 《石油勘探与开发:英文版》 2018年第4期640-661,共22页
The U. S. National Aeronautics and Space Administration(NASA) has archived thousands of satellite images of density plumes in its online publishing outlet called ’Earth Observatory’ since 1999. Although these images... The U. S. National Aeronautics and Space Administration(NASA) has archived thousands of satellite images of density plumes in its online publishing outlet called ’Earth Observatory’ since 1999. Although these images are in the public domain, there has not been any systematic compilation of configurations of density plumes associated with various sedimentary environments and processes. This article, based on 45 case studies covering 21 major rivers(e.g., Amazon, Betsiboka, Congo [Zaire], Copper, Hugli [Ganges], Mackenzie, Mississippi, Niger, Nile, Rhone, Rio de la Plata, Yellow, Yangtze, Zambezi, etc.) and six different depositional environments(i.e., marine, lacustrine, estuarine, lagoon, bay, and reef), is the first attempt in illustrating natural variability of configurations of density plumes in modern environments. There are, at least, 24 configurations of density plumes. An important finding of this study is that density plumes are controlled by a plethora of 18 oceanographic, meteorological, and other external factors. Examples are: 1) Yellow River in China by tidal shear front and by a change in river course;2) Yangtze River in China by shelf currents and vertical mixing by tides in winter months;3) Rio de la Plata Estuary in Argentina and Uruguay by Ocean currents;4) San Francisco Bay in California by tidal currents;5) Gulf of Manner in the Indian Ocean by monsoonal currents;6) Egypt in Red Sea by Eolian dust;7) U.S. Atlantic margin by cyclones;8) Sri Lanka by tsunamis;9) Copper River in Alaska by high-gradient braid delta;10) Lake Erie by seiche;11) continental margin off Namibia by upwelling;12) Bering Sea by phytoplankton;13) the Great Bahama Bank in the Atlantic Ocean by fish activity;14) Indonesia by volcanic activity;15) Greenland by glacial melt;16) South Pacific Ocean by coral reef;17) Carolina continental Rise by pockmarks;and 18) Otsuchi Bay in Japan by internal bore. The prevailing trend in promoting a single type of river-flood triggered hyperpycnal flow is flawed because there are 16 type 展开更多
关键词 NASA satellites DENSITY PLUMES river-mouth environments controlling factors HYPERPYCNAL flows submarine fans DEEP-WATER reservoirs
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Initial orbit determination of BDS-3 satellites based on new code signals
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作者 Fei Ye Yunbin Yuan Jikun Ou 《大地测量与地球动力学:英文版》 2018年第4期342-346,共5页
For the two newly launched satellites(PRN number 27 and 28) of the future global BeiDou navigation satellite system(BDS-3), there is no available broadcast ephemeris data and other initial orbit information, but the i... For the two newly launched satellites(PRN number 27 and 28) of the future global BeiDou navigation satellite system(BDS-3), there is no available broadcast ephemeris data and other initial orbit information, but the initial orbit is the fundamental of the comprehensive analysis of the satellites and their signals. Precise orbit determination(POD) also requires determination of a priori initial value with a certain precision in order to avoid problems such as filter divergence during POD. Compared with the Newton iteration method, which relies on the initial value, this study utilizes the Bancroft algorithm to directly solve the nonlinear equations with the advantage of numerical stability. The initial orbits of these two satellites are calculated based on new code signals, and their results are analyzed and discussed. The experimental results show that, with the exception of very few epochs, when the new code signal is utilized, the median and robust variance factor of the observed residuals computed using pseudo-range observations and the solved initial orbits are less than 4 and 2 m, respectively. It also shows that this solution can be used for rapid initial orbit recovery after maneuvers of the new BeiDou satellites. 展开更多
关键词 NEW-GENERATION BEIDOU SATELLITES NEW CODE SIGNALS Initial orbit determination Bancroft
Fully Bayesian reliability assessment of multi-state systems with overlapping data 预览
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作者 Zhipeng Hao Jianbin Guo Shengkui Zeng 《系统工程与电子技术:英文版》 SCIE EI CSCD 2017年第1期187-198,共12页
The failure data at the system level are often limited,resulting in high uncertainty to system reliability assessment. Integrating data drawn from various structural levels of the target system (e.g. the system, subsy... The failure data at the system level are often limited,resulting in high uncertainty to system reliability assessment. Integrating data drawn from various structural levels of the target system (e.g. the system, subsystems, assemblies and components),i.e. the multi-level data, through Bayesian analysis can improve the precision of system reliability assessment. However, if the multi-level data are overlapping, it is challenging for Bayesian integration to develop the likelihood function. Especially for multistate systems (MSS), the Bayesian integration with overlapping data is even more difficult. The major disadvantage of previous approaches is the intensive computation for the development of the likelihood function caused by the workload to opt the appropriate combinations of the vectors of component states consistent with the overlapping data. An improved fully Bayesian integration approach from a geometric perspective is proposed for the reliability assessment of MSS with overlapping data. In this method, a specific combination of component states is regarded as a state vector, which leads to a specific system state of the MSS, and all state vectors generate a system state space. The overlapping data are regarded as the constraints which create hyperplanes in the system state space. And a point in a hyperplane corresponds to a particular combination of the state vectors. In the light of the features of the constraints, the proposed approach introduces space partition and hyperplane segmentation, which reduces the selection workload significantly and simplifies the likelihood function for overlapping data. Two examples demonstrate the feasibility and efficiency of the proposed approach. 展开更多
关键词 BAYESIAN INTEGRATION OVERLAPPING DATA MULTI-STATE systems
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带挠性附件卫星转动惯量的在轨辨识 预览 被引量:1
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作者 兰聪超 谭述君 +1 位作者 吴志刚 李文博 《振动与冲击》 EI CSCD 北大核心 2017年第8期16-21,33共7页
针对大型卫星的挠性附件振动会影响质量特性参数辨识精度和准确性的问题,提出了带挠性附件卫星转动惯量参数在轨辨识的递推算法。基于带挠性附件卫星动力学模型,导出了转动惯量参数辨识的最小二乘描述形式;与挠性附件振动模态估计的卡... 针对大型卫星的挠性附件振动会影响质量特性参数辨识精度和准确性的问题,提出了带挠性附件卫星转动惯量参数在轨辨识的递推算法。基于带挠性附件卫星动力学模型,导出了转动惯量参数辨识的最小二乘描述形式;与挠性附件振动模态估计的卡尔曼滤波算法相结合,提出了一种适用于带挠性附件卫星转动惯量参数辨识的并发递推算法。通过仿真算例验证了卫星挠性附件振动对转动惯量参数辨识的影响和文中递推算法的有效性。 展开更多
关键词 卫星 转动惯量 参数辨识 递推算法 挠性附件
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日本空间力量建设现状和发展研究 预览
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作者 李悦 王京 张成勇 《航天电子对抗》 2017年第3期59-64,共6页
日本空间力量长期以来藏军于民,但却拥有宏大的工业基础和雄厚的技术支撑,空间“动员能力”很强。重点对日本空间力量部署和作战能力进行了研究,对空间力量发展规律提出看法,为应对日本国家安全战略转变提供了参考。
关键词 日本 卫星 空间力量
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无拖曳航天器连续推力分配的伪逆法二次优化方案 预览
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作者 刘睿 周军 《西北工业大学学报》 CSCD 北大核心 2017年第6期948-953,共6页
主要研究了应用伪逆法进行无拖曳航天器连续推力分配时的二次优化方法。首先,根据伪逆法初值求取方法,得出其解存在推力为负和超出执行机构约束饱和限制情况的结论;然后提出了伪逆法二次优化两步方案,针对推力为负提出了利用推力器... 主要研究了应用伪逆法进行无拖曳航天器连续推力分配时的二次优化方法。首先,根据伪逆法初值求取方法,得出其解存在推力为负和超出执行机构约束饱和限制情况的结论;然后提出了伪逆法二次优化两步方案,针对推力为负提出了利用推力器间的关联关系进行替代的方法,针对推力器约束饱和限制确定了约束上下限。最后,通过干扰跟踪仿真和推力输出仿真,此二次优化方案满足了推力器输出为正和输出限幅的要求,并且计算简单,可以实现在轨实时分配,也可应用于其他需要连续推力的航天器推力分配任务。 展开更多
关键词 无拖曳航天器 推力分配 伪逆法 二次优化
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利用局部高空间分辨率大气数据计算GRACE大气去混频模型 预览
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作者 游为 《测绘学报》 EI CSCD 北大核心 2017年第3期316-324,共9页
在计算GRACE重力场反演中的大气去混频模型时,针对ECMWFop或ERA-Interim大气数据空间水平分辨率不足的问题,提出了一种局部区域高空间水平分辨率大气数据与全球大气数据合理拼接融合的方法。利用欧洲局部区域的大气数据与ERA-Interim大... 在计算GRACE重力场反演中的大气去混频模型时,针对ECMWFop或ERA-Interim大气数据空间水平分辨率不足的问题,提出了一种局部区域高空间水平分辨率大气数据与全球大气数据合理拼接融合的方法。利用欧洲局部区域的大气数据与ERA-Interim大气数据融合计算了一组改进的大气去混频模型,从谱域、空域及星间距离变率残差角度分析了改进大气去混频模型的质量。结果表明改进大气去混频模型相对于常规大气去混频模型的质量提高最大比例为1.87%,与AOD1BRL05相对于RL04的提高比例2.27%相当,验证了高空间水平分辨率大气数据确实有助于提高大气去混频模型质量的结论,为改进GRACE提取局部区域特定质量变化信号提供了一种方法。 展开更多
关键词 地球重力场 GRACE 大气去混频模型 星间距离变率残差
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卫星故障诊断系统智能研制技术研究 预览
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作者 李洪珏 董云峰 《上海航天》 CSCD 2017年第3期52-59,共8页
为解决卫星故障诊断系统研制周期长、重复性工作量大的缺点,针对基于平行系统和数字卫星概念设计的卫星故障诊断系统,提出一种智能研制技术。建立包含参数、接口、原理模型、误差模型、故障模型和三维模型的数字部件库,利用数字装配技... 为解决卫星故障诊断系统研制周期长、重复性工作量大的缺点,针对基于平行系统和数字卫星概念设计的卫星故障诊断系统,提出一种智能研制技术。建立包含参数、接口、原理模型、误差模型、故障模型和三维模型的数字部件库,利用数字装配技术实现对卫星的规范化描述,基于逻辑维分形结构将源代码书写规范分为确定性规则、有限规则和推理规则,采用机器学习的方法完成源代码书写规则的推理和实施,实现包括子系统部件、姿轨控软件、星务软件、耦合场计算、其他文件和地面测控系统等的数字卫星、遥测遥控系统与配套工具的源代码自动书写、编译及部署。针对多颗卫星进行故障诊断系统研制,系统运行结果表明了智能研制技术在提高系统研制效率方面的可行性和有效性。 展开更多
关键词 卫星 故障诊断 平行系统 智能研制 数字装配 机器学习 逻辑维 分形
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基于GF-1卫星数据的冬小麦叶片氮含量遥感估算 预览 被引量:8
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作者 李粉玲 常庆瑞 +1 位作者 申健 王力 《农业工程学报》 EI CAS CSCD 北大核心 2016年第9期157-164,共8页
以陕西关中地区大田和小区试验下的冬小麦为研究对象,探讨基于国产高分辨率卫星GF-1号多光谱数据的冬小麦叶片氮含量估算方法和空间分布格局。基于GF-1号光谱响应函数对地面实测冬小麦冠层高光谱进行重采样,获取GF-1号卫星可见光-近红... 以陕西关中地区大田和小区试验下的冬小麦为研究对象,探讨基于国产高分辨率卫星GF-1号多光谱数据的冬小麦叶片氮含量估算方法和空间分布格局。基于GF-1号光谱响应函数对地面实测冬小麦冠层高光谱进行重采样,获取GF-1号卫星可见光-近红外波段的模拟反射率,并构建光谱指数,利用与叶片氮含量在0.01水平下显著相关的8类光谱指数,分别建立叶片氮含量的一元线性、一元二次多项式和指数回归模型。通过光谱指数与叶片氮含量的敏感性分析,以及所建模型的综合对比分析,获取适合冬小麦叶片氮含量估算的最佳模型。结果表明:模拟卫星宽波段光谱反射率和卫星实测光谱反射率间的相关系数高于0.95,具有一致性;改进型的敏感性指数综合考虑了模型的稳定性、敏感性和变量的动态范围,敏感性分析表明比值植被指数对叶片氮含量的变化响应能力最强;综合模拟方程决定系数、模型敏感性分析、精度检验和遥感制图的结果,认为基于比值植被指数建立的叶片氮含量估算模型适用性最强,模拟结果与实际空间分布格局最为接近,为基于GF-1卫星数据的区域性小麦氮素营养监测提供了理论依据和技术支持。 展开更多
关键词 卫星 敏感性分析 GF-1 冬小麦
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卫星典型复合材料蜂窝结构板的冲击定位方法 预览 被引量:1
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作者 赵发刚 周春华 +2 位作者 梁大开 刘曌 史瑞 《振动.测试与诊断》 EI CSCD 北大核心 2016年第6期1204-1209,共6页
针对一种典型复合材料蜂窝夹芯结构,构建了光纤Bragg光栅传感系统,实时监测材料冲击响应信号,对信号进行了小波包分解获得其能量谱。结果表明,第16阶小波包能量对冲击敏感。利用能量幅值比进行冲击定位,平均误差为1.87cm。该方法能够有... 针对一种典型复合材料蜂窝夹芯结构,构建了光纤Bragg光栅传感系统,实时监测材料冲击响应信号,对信号进行了小波包分解获得其能量谱。结果表明,第16阶小波包能量对冲击敏感。利用能量幅值比进行冲击定位,平均误差为1.87cm。该方法能够有效判定冲击位置,为卫星结构健康监测提供了一定的依据。 展开更多
关键词 复合材料蜂窝板 光纤布拉格光栅 冲击定位 小波包分析
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卫星遥感和积温-辐射模型预测区域冬小麦成熟期 预览 被引量:3
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作者 黄健熙 牛文豪 +2 位作者 马鸿元 苏伟 朱德海 《农业工程学报》 EI CAS CSCD 北大核心 2016年第7期152-157,共6页
准确预测区域尺度的小麦成熟期,指挥麦收机械化作业有序开展,具有十分重要的社会和经济效益。该文针对目前区域冬小麦成熟期预测中时效性差、缺乏空间分布以及缺少定量描述等突出问题,选择华北地区河北、河南和山东3省冬小麦为研究对象... 准确预测区域尺度的小麦成熟期,指挥麦收机械化作业有序开展,具有十分重要的社会和经济效益。该文针对目前区域冬小麦成熟期预测中时效性差、缺乏空间分布以及缺少定量描述等突出问题,选择华北地区河北、河南和山东3省冬小麦为研究对象,首先基于S-G滤波后的2013年冬小麦生育期时间序列MODIS LAI,采用动态阈值法获取抽穗期具体日期,即叶面积指数(LAI)达到峰值时的具体日期;然后基于由2008-2012年农业气象资料与地面气象资料构建的抽穗-成熟期有效积温模型和总辐射模型,逐个栅格单元计算MODIS LAI获取的抽穗期具体日期到当前日期的积温、太阳辐射总量,并结合全球多模式集合预报(THORPEX Interactive Grand Global Ensemble,TIGGE)资料对当前日期(5月10号至6月8号)之后的16 d冬小麦成熟期进行逐日动态预测以得到全部区域的成熟期预测值;最后采用农业气象站点的成熟期观测值对预测结果进行验证,结果表明:冬小麦成熟期预测值与观测值的决定系数R2为0.92,均方根误差RMSE约为3 d,两者具有良好的相关性。该研究方法对其他大区域的农作物成熟期预测具有借鉴价值。 展开更多
关键词 卫星 遥感 太阳辐射 抽穗期 有效积温 成熟期预报 冬小麦
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上电时间对卫星单机设计的影响分析 预览
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作者 钱威 张国勇 +2 位作者 董房 徐锡杰 卢丹 《航天器环境工程》 2016年第1期82-85,共4页
卫星整星测试时系统接口多,供电环境复杂,工作时需要严格按照时序进行开关机控制.文章结合典型故障案例进行了上电时间对单机设计、工作的影响分析,发现2 类常见的异常现象:1)上电欠压引起的状态不可确定问题;2)上电时序不合理造成... 卫星整星测试时系统接口多,供电环境复杂,工作时需要严格按照时序进行开关机控制.文章结合典型故障案例进行了上电时间对单机设计、工作的影响分析,发现2 类常见的异常现象:1)上电欠压引起的状态不可确定问题;2)上电时序不合理造成的单机数据异常问题.最后给出实用的排查方法供工程设计人员参考. 展开更多
关键词 卫星 上电时间 故障树分析 整星测试
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