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1.
月球表面微波主被动遥感的建模模拟与反演   总被引:7,自引:0,他引:7  
探测月球和其它外星球是我国空间遥感与深空探测的又一轮新课题。研究地球遥感中星载被动遥感辐射计、主动遥感高分辨率合成孔径雷达等如何应用于月球和其它外星球的探测是一项十分有意义的工作。了解月球表层的月壤与月岩的物质状态及其分布,对于月球资源的科学认识、以及未来月球探测、登月与月球开发,以及其它外星球探测均具有十分重要的意义。先讨论微波被动遥感月球表面辐射的模拟和由微波辐射反演月壤厚度。由月球表面数字高程和月壤厚度实测点数据建立月球表面高度与月壤厚度的一种对应关系,构造整个月球表面月壤厚度的试验性分布。根据克莱门汀的紫外可见光光学数据,计算整个月球表面月壤中FeO+TiO2含量分布,给出整个月球表面月壤介电常数分布。由月球表层温度的观测结果以及月壤的导热特性,给出月尘层与月壤层温度随纬度分布的经验公式。在这些条件基础上,建立月尘、月壤、月岩3层微波热辐射模型。由起伏逸散定理,模拟计算月壤低耗散介质层多通道辐射亮度温度。以此辐射亮度温度模拟加随机噪声为理论观测值,按3层模型提出月壤层厚度反演方法。由于高频通道穿透深度小,由高频通道的辐射亮度温度按照两层尘-月壤微波热辐射模型反演月尘层与月壤层的物理温度。并以此为已知参数,由穿透深度较大的低频通道的辐射亮度温度反演月壤层厚度,对于反演的相对误差也进行了讨论。在研究微波主动遥感方面,提出低空飞行全极化L波段雷达窄脉冲探测月壤层厚与层结构的建议。此时采用一层具有上下随机粗糙界面的有耗
介质层月壤层模型,在下垫月岩粗糙界面上有一层随机分布的碎石散射体。推导了包含面散射、体散射,以及面体相互作用7种散射机制的全极化脉冲波Mueller矩阵解。以月壤特征参数(月壤层厚、FeO+TiO2金属含量、介电常数,界面粗糙度、碎石分布等)为函数,用时域Mueller矩阵解数值模拟来验证方法可行性。L波段窄脉冲极化回波波形能用于反演或估算月壤厚度与分层结构。  相似文献
2.
Observations of Lake Baikal ice from satellite altimetry and radiometry   总被引:3,自引:0,他引:3  
We demonstrate the potential of combining satellite altimetry and radiometry for lake ice studies using the example of Lake Baikal in Siberia. We show the synergy using active and passive microwave observations available from the recent satellite altimetry missions (TOPEX/Poseidon, Jason-1, ENVISAT and Geosat Follow-On), complemented by the SSM/I passive data. We assess the applicability of altimetric and radiometric data for ice/water discrimination, and discuss the drawbacks and benefits of each type of sensor. An ice discrimination method, based on the combined use of the data from the four altimetric missions and SSM/I, is proposed and validated using available in situ observations and MODIS imagery. The method is applied to the entire satellite data set and used to define specific dates of ice events (first appearance of ice, formation of stable ice cover, first appearance of open water, complete disappearance of ice) and associated uncertainties. Using these satellite-derived estimates, we can extend the existing time series of ice events in the Southern Baikal up to 2004 and provide new information on the Middle and Northern Baikal, regions where no recent in situ ice cover observations are available. Our data show that over the last 10-15 years, trends towards earlier ice formation and later ice break-up result in a tendency for longer fast ice duration over the whole Lake Baikal. The methods proposed here have been tested for Lake Baikal, but they are applicable for other lakes and water bodies with seasonal ice cover.  相似文献
3.
The backscattering and emission measured simultaneously by radar and radiometer show promise for the estimation of surface variables such as near-surface soil moisture and vegetation characteristics. In this paper, the 10.7 GHz Tropical Rainfall Measuring Mission (TRMM) microwave imager (TMI) channel and 13.8 GHz precipitation radar (PR) observations are simultaneously used for the estimation of the near-surface soil moisture and vegetation properties. The Fresnel model for soil and a simple model for vegetation are used to simulate the passive microwave emission at 10.7 GHz. To determine the PR backscatter signal from a land surface, a theoretical approach is used based on the Geometric Optics Model for simulating bare soil and a semi-empirical water-cloud model for vegetation. The model parameters required in specifying the nature of the soil and vegetation are calibrated on the basis of in situ soil moisture data combined with remotely sensed observations. The calibrated model is subsequently used to retrieve near-surface soil moisture and leaf area index for assumed values of surface roughness and temperature. Algorithm assessment using synthetic passive and active microwave data shows a nonlinearity effect in the system inversion, which results in a varying degree of error statistics in soil wetness and vegetation characteristics retrieval. The technique was applied on TRMM radar/radiometer observations from three consecutive years and evaluated against in situ near-surface (5 cm) soil moisture measurements from the Oklahoma Mesonet showing a consistent performance.  相似文献
4.
基于Internet的远程控制康复训练机械臂   总被引:1,自引:0,他引:1  
针对上肢受伤和中风病人康复医疗的需要,将力反馈遥操作机器人技术应用于上肢受伤和中风病人的康复训练,研制了一种新颖的基于Internet的远程康复训练机械臂,使得医生可远程设定康复机械臂的训练模式和控制参数,从而控制机械臂,帮助在家中或社区医院的中风病人或上肢残障人员进行康复训练,医生利用反馈的视频图像及力反馈信息监控患者的训练状况.该系统可以大大提高医生的工作效率,方便广大中风病人和上肢残障人员.  相似文献
5.
针对观测平台和运动对象间的距离参数会对传感器随机测量误差带来影响的问题,提出了一种基于模糊距离阈值的主被动传感器量测融合算法。讨论了根据距离参数选择主被动融合跟踪模式的方法,采用指数函数和模糊处理技术,利用已有信息实时改变主、被动传感器在量测融合过程中所占的权重。仿真结果表明,当传感器和运动对象间的距离对随机测量误差的影响不能忽略时,基于模糊距离阈值的主被动传感器变权重融合算法和传统的固定权重融合算法相比更加稳定,能够充分发挥主、被动传感器间的互补特性。  相似文献
6.
针对智能终端数据共享中的网络延迟问题,本文提出一种两阶段,主动预取与被动预取相结合的数据预取缓存方法,减少网络延迟,提高用户体验。该方法利用网络空闲时间预取数据,减少用户等待时间;通过两阶段预取策略减少网络带宽消耗;通过主被动配合的预取算法来预取数据,提高预取准确率和预取效率;通过一种权重更新函数来更新客户端的缓存,减少对智能终端存储空间的消耗。实验表明使用此方法能减少用户等待时间58.2%,预取命中率为92%,带来的带宽损耗小于5%。  相似文献
7.
由于无线传感器网络自身的特性,其不可避免存在热区。在LAECH及其现有改进算法的基础上提出了基于事件频度的多层次分簇算法(MCAFE)。MCAFE根据监测区域内的事件频度来确定最优簇首的数目而不是固定值。由于采用全局簇群分布式控制、局部子簇群集中式管理方法,因此在不同层次簇梯度分布、同层次簇均匀分布状态下进行簇分裂或子簇整合。最后对NS2上的仿真结果进行了分析。  相似文献
8.
阐述了温度无线传感技术在热防护系统健康监测中应用的发展与现状;概括地阐明了被动式SensorTag这种无线微传感装置的工作原理和特点,分析了该装置在高温下的工作能力和设计方面存在的问题;总结了主动式无线传感装置的发展与试验测试,比较分析了被动式和主动式无线传感装置的相同点和不同点,指出了各自的优点和不足,并总结了高温无线温度微传感装置今后努力的方向。  相似文献
9.
Aiming at the problem of low efficiency for estimating large-area forest Above-Ground Biomass(AGB) using multi-mode remote sensing, this study fully integrated multi-dimensional observation characteristics of forest AGB from active and passive remotely sensed features, in order to improve the regional estimation result. Based on an analysis on two temporal estimation results, this study disclosed the spatial patterns of the regional forest AGB changes. It could provide data supports for the scientific assessments on the regional eco-environmental protection projects (i.e., the Natural Forest Protection Project) and for improving the ability of continuous dynamic monitoring and early warning the national eco-environment by use of remote sensing. The study area is located at the Great Khingan, the Inner Monolia. Based on the active and passive multi-mode remotely sensed features extracted from the Landsat-TM5(TM) and ALOS-1 PALSAR mainly acquired in 2009,and the Gaofen-1(GF-1)and ALOS-2 PALSAR data mainly acquired in 2014, respectively, the k- Nearest Neighbor with Fast Iterative Features Selection (KNN-FIFS) method was applied to fast select the features composition to establish the optimal estimating model. The 7th and 8th National Forest resource Inventory (NFI) data were applied to training and validating (by Leave One Out method, LOO) the optimal KNN-FIFS for estimating two-temporal forest(arbor forest) AGB over study area. Based on the comparison between the two-temporal AGB results, the local forest changes from 2009 to 2014 at pixel and regional scales were quantitatively analyzed. At pixel scale, the validation based on NFI and LOO method showed that, estimates obtained a R2=0.56 and Root-Mean-Square Error (RMSE) = 25.95 t/ha, and a R2=0.64; RMSE=24.55 t/ha for 2009 and 2014, respectively. Meanwhile, as compared with NFI measurements, the average of 2009 results was over-estimated (predictions: 81.59 t/ha VS NFI measurements:78.64 t/ha), but the average of 2014 was under-estimated (predictions: 79.63 t/ha VS NFI measurements:82.48 t/ha). At regional scale, the overall averages of 2009 and 2014 were 88.33 t/ha, 94.61 t/ha respectively, with a increment of 6.28 t/ha,which were closed to those from previous studies using the Biomass Expansion Factor method, 87.14 t/ha for 2008, and 92.20 t/ha for 2013, respectively. The KNN-FIFS method used in this study, could largely improve the efficiency for selecting the optimal composition from high-dimensional multi-mode remotely sensed features. Full integration of the multi-dimensional observation characteristics from active and passive remotely sensed information, could improve the estimating accuracy and saturation level of forest AGB. Validation based the LOO method at pixel scale made the KNN-FIFS more robust with avoiding the random errors brought form the selection of training and validation data set. From 2009 to 2014, the local vegetation fractional coverage got to increase obviously, as well as the local forest AGB. Thanks to the implement of National Forest Protection Project, the situation of the local forest resource was effectively improved, although some forest fire were occasionally witnessed by the study years.  相似文献
10.
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