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961.
962.
为提高通信系统维修性评价的实用性和可操作性,提出了一种基于PCA-LINMAP-FCE 的维修性评价方法.在构建简化的维修性评价指标体系的基础上,将PCA-LINMAP与模糊综合评判(FCE)方法相结合,从定量和定性的角度对维修性进行评价.实例仿真分析表明,该方法可操作性强,且有效地降低了评价的主观随意性,使维修设计和作业人员全面掌控通信系统装备维修性的影响因素,能够为科学制定设计方案和维修实施决策方案提供决策信息. 相似文献
963.
双线偏振雷达差分反射率因子系统误差订正 总被引:3,自引:0,他引:3
差分反射率因子ZDR易受雷达系统自身的影响而产生明显偏差,这种偏差是不随空间积累而改变的.为了保证雷达资料及其产品的质量,根据中国气象科学研究院灾害天气国家重点实验室车载C波段双线偏振多普勒雷达(C-band Polarimetric Doppler Radar on Wheel,CPDRW)的外场试验,对观测的ZDR进行了分析,并以垂直扫描数据的订正结果为参考,重点讨论了以体扫模式最高仰角下的小雨和干雪这两种自然目标物为订正对象得到的订正结果.结果表明,高仰角体扫资料的这两种自然目标物都能较好地订正ZDR的系统误差.但相较于小雨,干雪的订正效果更加稳定,是进行ZDR系统误差订正的最优气象目标物,而利用高仰角体扫资料的干雪粒子进行ZDR系统误差订正也就成为垂直扫描订正法的最佳替代方法. 相似文献
964.
本文主要利用黔东南榕江双偏振多普勒天气雷达、常规观测和加密自动站观测等资料,对黔东南2020年5月31日及6月8日两次暖区暴雨天气过程的雷达回波特征进行分析,结果表明:(1)月亮山区暖区暴雨的雷达回波主要以积状云回波为主,地形对回波具有明显强迫抬升作用;(2)回波演变主要分为三个阶段,对流回波的“合并增强”,单体后向传播形成长时间的“列车效应”,造成了月亮山区的暴雨过程;(3)径向速度场往往配合逆风区及γ中尺度的气旋式辐合;回波顶高、垂直积分液态含水量伴随跃增现象;(4)暖区暴雨由低质心+高质心回波共同影响造成,发展旺盛的单体生消较快,对流性特征显著;(5)随着质心高度、最大垂直液态水含量及最大回波强度的升高,雨强也会随之增强,但是三者与雨强变化之间存在一定的滞后关系;(6)暴雨以上降水以大雨滴为主,降水强度强,雨滴浓度大;(7)雷达估测的1h累积降水量、3h累积水量及风暴总降水量产品的演变与对应的自动站观测到的实际雨量变化趋势较为一致,但与实况均存在一定的偏差,且随着雨强的增大,误差随之增大;3h累积水量及风暴总降水量两个产品能较好地反映出强降水落区。 相似文献
965.
966.
阐述了非量测数码相机内方位元素的概念、测定的原理和方法,以及在成像过程中产生误差的来源。使用共线条件方程的基本原理,选取合适的模型,利用澳大利亚墨尔本大学的Australis软件解算得到内方位元素,并分析结果的可靠性。 相似文献
967.
This paper will discuss strategies for trinocular image rectification and matching for linear object tracking. It is well known that a pair of stereo images generates two epipolar images. Three overlapped images can yield six epipolar images in situations where any two are required to be rectified for the purpose of image matching. In this case, the search for feature correspondences is computationally intensive and matching complexity increases. A special epipolar image rectification for three stereo images, which simplifies the image matching process, is therefore proposed. This method generates only three rectified images, with the result that the search for matching features becomes more straightforward. With the three rectified images, a particular line-segment-based correspondence strategy is suggested. The primary characteristics of the feature correspondence strategy include application of specific epipolar geometric constraints and reference to three-ray triangulation residuals in object space. 相似文献
968.
Three transformation models (Bursa-Wolf, Molodensky, and WTUSM) are generally used between two data systems transformation. The linear models are used when the rotation angles are small; however, when the rotation angles get bigger, model errors will be produced. In this paper, we present a method with three main terms: the traditional ? rotation angles θ, φ, ψ are substituted with a,b,c which are three respective values in the anti-symmetrical or Lodrigues matrix; ? directly and accurately calculating the formula of seven parameters in any value of rotation angles; and ? a corresponding adjustment model is established. This method does not use the triangle function. Instead it uses addition, subtraction, multiplication and division, and the complexity of the equation is reduced, making the calculation easy and quick. 相似文献
969.
The objective of this article is to evaluate the effectiveness of various algorithms for estimating impervious surfaces. Linear spectral mixture analysis (LSMA) and multi-layer perceptron (MLP) network using original and spectral normalized images were applied to two ASTER images acquired on 31 August and 9 April 2004, respectively. Accuracy assessment was performed with a Quickbird image. Root-mean-square errors (RMSEs) were calculated and compared. Results indicated that LSMA with original images provided the poorest results. RMSE was 14.8% for the August image and 22.4% for the April image. Results from LSMA with normalized images improved significantly with RMSE of 12.6% for the August image and 18.9% for the April image. The MLP modelling with original images generated slightly better results with RMSE of 12.2% and 18.4% for each image. The MLP modelling of normalized images provided the best estimation, yielding a RMSE of 12.1% for the August image and 18.2% for the April image. 相似文献
970.
ABSTRACTNowadays, mathematical models are widely used to predict climate processes, but little has been done to compare the models. In this study, multiple linear regression (MLR), multi-layer perceptron (MLP) network and adaptive neuro-fuzzy inference system (ANFIS) models were compared for precipitation forecasting. The large-scale climate signals were considered as inputs to the applied models. After selecting the most effective climate indices, the effects of large-scale climate signals on the seasonal standardized precipitation index (SPI) of the Maharlu-Bakhtaran catchment, Iran, simultaneously and with a delay, was analysed using a cross-correlation function. Hence, the SPI time series was forecasted up to four time intervals using MLR, MLP and ANFIS. The results showed that most of the indices were significant with SPI of different lag times. Comparison of the SPI forecast results by MLR, MLP and ANFIS models showed better performance for the MLP network than the other two models (RMSE = 0.86, MAE = 0.74 for the first step ahead of SPI forecasting).
Editor D. Koutsoyiannis; Associate editor F. Pappenberger 相似文献