Hyperion, IKONOS, ALI, and ETM+ sensors in the study of African rainforests

The goal of this research was to compare narrowband hyperspectral Hyperion data with broadband hyperspatial IKONOS data and advanced multispectral Advanced Land Imager (ALI) and Landsat-7 Enhanced Thematic Mapper Plus (ETM+) data through modeling and classifying complex rainforest vegetation. For this purpose, Hyperion, ALI, IKONOS, and ETM+ data were acquired for southern Cameroon, a region considered to be a representative area for tropical moist evergreen and semi-deciduous forests. Field data, collected in near-real time to coincide with satellite sensor overpass, were used to (1) quantify and model the biomass of tree, shrub, and weed species; and (2) characterize forest land use/land cover (LULC) classes.The study established that even the most advanced broadband sensors (i.e., ETM+, IKONOS, and ALI) had serious limitations in modeling biomass and in classifying forest LULC classes. The broadband models explained only 13-60% of the variability in biomass across primary forests, secondary forests, and fallows. The overall accuracies were between 42% and 51% for classifying nine complex rainforest LULC classes using the broadband data of these sensors. Within individual vegetation types (e.g., primary or secondary forest), the overall accuracies increased slightly, but followed a similar trend. Among the broadband sensors, ALI sensor performed better than the IKONOS and ETM+ sensors.When compared to the three broadband sensors, Hyperion narrowband data produced (1) models that explained 36-83% more of the variability in rainforest biomass, and (2) LULC classifications with 45-52% higher overall accuracies. Twenty-three Hyperion narrowbands that were most sensitive in modeling forest biomass and in classifying forest LULC classes were identified and discussed.     

非接触式测量机器人的误差分析

本文介绍了一种新型的非接触式机器人测量系统,该系统以串联机器手作为主体,激光位移传感器为测量探针,对球壳类、回转类部件的几何尺寸、表面缺陷进行非接触、高精度测量。该测量系统将机器人旋转关节的角位移测量转换成弧长测量。本文详细分析了这种方法的优缺点,以及机器人运动学参数的误差对机器人末端执行器位置精度的影响。     

北京谱仪漂移室读出电子学校准电路

本文介绍的电路可同时进行时间和电荷校准,它的校准量程大,精度高,稳定性好,可输出864路指数形校准信号,并可手动或程控。它的时间校准精度优于±250ps,电荷量校准精度优于±1％。     

选区激光烧结设备成型缸传动系统及铺粉精度的研究

成型缸传动系统是影响选区激光烧结铺粉精度的关键因素,根据铺粉工艺过程,确定成型缸传动系统总体方案,并建立传动系统模型.根据铺粉参数要求,详细介绍了传动系统动力参数的计算及步进电机的选用.最后对传动系统进行了静态定位误差的分析,以确保选区激光烧结设备铺粉精度符合要求.     

基于H.26L关键算法模块软件编码器的设计与实现

继制定了H.261、H.263、H.263+等视频压缩标准后,ITU—T正在制定新的视频压缩标准H.26L,目的是为了取得更加有效的图像压缩效果和提供理想的传输接口。文章首先分析了H.26L的各个关键算法模块的原理,与H.263、H.263+进行比较分析,得出其优点;然后阐述如何用VisualC++6.0实现这些算法模块;最后通过实验证明,该文设计的软件编码器能达到更高效的压缩比、信噪比和编码速度,具有一定的实用价值。     

六自由度微动平台旋转自由度的设计

介绍六自由度微动平台的原理、结构;对旋转自由度的实现进行了设计;同时对旋转自由度的调整精度进行了分析。这种形式的六自由度微动平台具有系统简单,可操作性强,实时监控调节,性价比高等优势。     

高精度遥感在地下煤火探测中的应用研究

针对乌达矿区地下煤火的类型和特点,将火区地质模型(燃烧分带、燃烧系统、燃烧阶段等模型)认识与高精度遥感的优势相结合,通过燃烧裂隙、燃烧系统和采煤工作面等重点信息的提取,大幅度提高了煤火信息的获取水平和探测精度。     

全方位装配机器人的刚度误差分析

为了提高工作效率并节约劳动力,设计了一种可执行装配任务的全方位装配机器人,此机器人能在实际工程中执行一些简单的装配任务.为提高机器人在执行装配作业任务时的装配精度,对其刚度误差进行分析.根据机器人的结构特点并结合旋量理论对并联机构各支链进行建模,推导出机器人的刚度模型.通过仿真分析得出了支链长度以及载荷对系统刚度的理论...     

提高水质检测准确性与稳定性的方法分析

水质检测质量是水资源管理的重要组成部分,很容易受到人为、系统、随机等多方面因素影响。分析了影响水质检测准确性与稳定性的因素及应对方法,并展开探讨,希望能够为相关业内人士带来一定启发。     

微波消解法快速测定废水中的总磷

采用微波对废水中的总磷进行消解,考察了消解时间、功率等不同实验条件对标样微波消解的影响,得出本实验消解的最佳条件,即过硫酸钾溶液用量为 0.5 mL,压力为10 MPa,消解时间为 2 min：并将该法与总磷测定的常规方法进行了比较,结果表明,过硫酸钾-微波消解法操作简单,效率高,对工作环境污染小.最后对微波消解法的精密度和准确度进行验证,实验结果表明其具有良好的精密度和准确度.