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1.
    
The objectives of the present study were to develop a new index based on remotely-sensed data for detecting the abundance of grasses in the family Poaceae, which has a high palatability for livestock in Mongolia, and to map the distribution of these grasses in the semi-arid Mongolian steppes. We measured ground-based spectral reflectance of pure plant leaves – including Poaceae grasses – and soils, as well as in-situ in the Mongolian grasslands. The hyper-spectral data, taken by a spectroradiometer, were converted into four multi-spectral bands (i.e., blue, green, red, and NIR) to simulate satellite-based imagery data. In order to magnify the characteristics of the spectral signal of Poaceae, NGBDI (Normalized Green-Blue Difference Index), NGRDI (Normalized Green-Red Difference Index), NDVI (Normalized Difference Vegetation Index), NNBDI (Normalized NIR-Blue Difference Index) were calculated from the four multi-spectral reflectance values. Poaceae Abundance Index (PAI) was derived by combining these four normalized difference indices. PAI was found out to be a good indicator to discriminate Poaceae grass from the other plant spectral data.  相似文献   
2.
文章阐述了将图像分割技术应用于雷达地形纹理分割中,用基于 FCM 图像分割方法对可见光纹理进行区域自动识别,形成互不相交的纹理区域,并借助建立的雷达材质库对区域材质进行指定,有效解决了海量地形纹理数据处理的难题,并提高了处理的准确性.  相似文献   
3.
高速走丝电火花线切割工作介质性能要求研究   总被引:7,自引:0,他引:7  
系统分析了高速走丝电火花线切割工作介质的主要性能要求,通过使用典型工作介质的切割对比,分析了线切割加工的工艺规律,指出工作介质洗涤能力是影响线切割工艺的最关键因素,对评价工作介质的优劣提出了参考意见。  相似文献   
4.
利用CAIV技术分别建立反舰导弹的作战效能模型和总拥有费用模型,并以权衡空间为约束条件,以费用最低为目标,建立保障性指标权衡优化模型。该方法可以为导弹武器装备保障性指标论证工作提供必要的理论基础和技术支持。  相似文献   
5.
地磁Ap指数滞后太阳周循环分析   总被引:3,自引:0,他引:3       下载免费PDF全文
把1932-2006年地磁Ap指数12个月流动均值分解成为(Ap)R和(Ap)I.其中(Ap)R为太阳黑子数R的线性函数,与太阳黑子数R相位相同,可能对应于日冕物质抛射(CME)等地磁控制因素. (Ap)I分量与太阳黑子数R相位相差约180°,该分量可能对应于极冕洞变化(从太阳峰年开始,由日面极区逐渐向赤道延伸).以地磁Ap指数与太阳黑子数R滞后非常严重的第20太阳周为例,证实了(Ap)I分量与极冕洞向赤道延伸循环变化相对应.因此极冕洞循环变化可能是导致地磁扰动指数与太阳周循环相位不一致,出现滞后现象的一个十分重要原因.  相似文献   
6.
针对加工工艺数据复杂、庞大、多变的特点,为解决加工工艺知识的匹配与推理的关键性技术,将模拟生态系统的模糊聚类算法应用于加工工艺知识库。提出了基于蚁群算法的工艺知识发现的概率查询方法,并建立加工工艺知识库的数学模型。通过输入关键词运行蚁群算法,描绘出索引地图,提取分析所需要的加工工艺序列。最后以铣加工工艺为例进行实例验证,结果表明,基于蚁群算法的工艺知识发现高效全面地优化了工艺序列。  相似文献   
7.
复杂曲面零件的几何特征提取对加工质量的检测及逆向重构具有重要意义。提出了一种复杂曲面零件散乱点云特征点提取方法。首先,提出了基于高斯权重的邻域主成分分析的方法,通过估计每一点邻域的局部变化程度对点云模型进行初始标记;然后,采用基于标记的自动识别法实现特征点的提取;最后,通过特征点聚类的方式去除了特征点集中的异常点,完善了提取的点云特征。该方法直接操作于散乱点云,无需任何的拓扑连接信息。试验结果表明:该方法简单、有效,不需要过多地人为调节参数,特征点提取完整。  相似文献   
8.
One minute resolution Polar Cap (PC) index was used for the analysis of magnetospheric dynamics. The 1995–2000 time series analysis revealed that the power spectrum of the PC-index fluctuations is a power law in a wide range of frequencies. However, the obtained exponents differ for low and high frequency regions. The probability distribution functions of the PC-index fluctuations show a strong non-gaussian shape, depending on the time of increment. This indicates that the PC-index exhibits intermittency, previously detected in solar wind and auroral electrojet index fluctuations. The PC-index probability distribution functions were fitted by the functional form proposed by Castaing et al. [Velocity probability density functions of high Reynolds number turbulence. Physica D. 46, 177–200, 1990] to describe intermittency phenomena in ordinary turbulent fluid flows. The agreement between the fitting parameters obtained for the PC index and those reported before for solar wind magnetic field fluctuations is within 30%; which is noticeably less than the difference between the same parameters of solar wind and the AE-index fluctuations. This fact indicates that the PC index reflects the solar wind influence on the high-latitude magnetosphere, especially during the summer.  相似文献   
9.
    
Magnetic data from a newly commissioned Indian Antarctic station Bharati (corrected geomagnetic (CGM) coordinates 74.7°S, 97.2°E) and closely-spaced IMAGE chain observatories (∼100° magnetic meridian in Northern hemisphere) has been analyzed to study the climatology of substorms which were localized poleward of the standard auroral oval. We considered four austral summers (year 2007–2010) when data from Bharati was available. Several very high latitude substorms were observed in this duration when the solar activity remained unexpectedly low for a long time. Various features of very high latitude substorms, e.g., local time dependence, interplanetary state, hemispherical asymmetry and their nightside low latitude signatures are examined. Events studied here, suggested the following properties of substorms occurring at very high latitudes: (1) maximum occurrence was observed near magnetic midnight (21:00–02:00 MLT). (2) In contradiction to earlier reports, many substorms were observed even during negative IMF Bz condition. In addition, majority of substorms occurred during low or moderate solar wind streams. (3) Magnetic signatures were often pronounced in the winter hemisphere. (4) Even if widely used standard AE indices fail to monitor very high latitude substorms, their low latitude signatures are often evident.  相似文献   
10.
针对目前提出的多载波估计算法存在的速度与精度的问题,基于模糊控制理论,改进和完善了多载波信号载频估计算法.通过对多载波时隙ALOHA网络真实卫星信号的载频频点提取,验证了该改进算法的时效性.  相似文献   
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