Automatic Cloud Detection of GF4 Multispectral Imagery Supported by the Priori Terminal Pixel Library

The GaoFen4 (GF4) satellite is China’s first geo-synchronous orbit remote sensing satellite. With the advantages of high frequency and wide width, it can provide fast and stable optical remote sensing images for agricultural, forestry, disaster reduction, meteorology, environmental protection, water conservancy and other applications in China. Efficient image automatic cloud detection helps to further improve the utilization efficiency of GaoFen4 images. CDAG（Cloud Detection Algorihtm-Generating）Cloud detection is an automatic cloud detection algorithm based on spectral analysis of pixel components, which can effectively reduce the influence of mixed pixels, complex surface structure and atmosphere. This paper aims to explore the application of CDAG algorithm in cloud detection of GaoFen4 multispectral imagery (GF4-PMS). Firstly, different cloud types and surface cover types were selected from hyperspectral images (AVIRIS) to establish cloud pixel library and clear sky pixel library. Next, the pixel library of multispectral images was simulated based on Hyperspectral pixel library and spectral response function of GF4-PMS sensor. Then, according to the spectral difference analysis of broken cloud, thin cloud, thick cloud and non-cloud pixel, the similarity probability analysis was performed on the to-be-detected pixel of the GF4-PMS image and the terminal pixel, and the GF4-PMS image cloud detection based on the optimal threshold automatic iteration was realized. Finally, cloud detection accuracy verification was carried out from multiple indicators such as cloud pixel correct rate, clear sky pixel correct rate, false positive rate and missed rate. The results show that AVIRIS images can effectively extract terminal pixel libraries for GF4-PMS image cloud detection. Clouds of Various types on GF4-PMS images can be better identified based on the CDAG algorithm. The accuracy of detection results for broken clouds, thin clouds and thick clouds with different time phases and different underlying surfaces can reach more than 90%. Therefore, the cloud detection method based on the priori terminal pixel library has a good application value for improving the utilization efficiency of GF4-PMS images.     

设计最优调节器的混合法

本文根据Kalman最优调节器理论和Wonham极点配置理论,提出了设计最优调节器的 一种方法.文中提出了等价权阵的概念,研究了权阵与闭环极点的关系以及最优调节器综合 评价问题,从而改进了以往工程中常用的试探法.     

小型雨水积蓄工程“水窖”的施工

本文介绍了一种集雨水窖的结构型式 ,施工方法 ,注意的问题 ,及资金和劳力的来源     

The accuracy of PSNR in predicting video quality for different video scenes and frame rates

Peak Signal-to-Noise Ratio (PSNR) is widely used as a video quality metric or performance indicator. Some studies have indicated that it correlates poorly with subjective quality, whilst others have used it on the basis that it provides a good correlation with subjective data. Existing literature seems to provide conflicting evidence of the accuracy of PSNR as a video quality metric. Based on experimental results, we explain a scenario where PSNR provides a reliable indication of the variation of subjective video quality and scenarios where PSNR is not a reliable video quality metric. We show that PSNR follows a monotonic relationship with subjective quality in the case of full frame rate encoding when the video content and codec are fixed. We provide evidence that PSNR becomes an unreliable and inaccurate quality metric when several videos with different content are jointly assessed. Furthermore, PSNR is inaccurate in measuring video quality of a video content encoded at different frame rates because it is not capable of assessing the perceptual trade-off between the spatial and temporal qualities. Finally, where PSNR is not a reliable video quality metric across different video contents and frame rates, we show that a perceptual video model recently approved by the International Telecommunication Union (ITU) provides quality predictions highly correlating with subjective scores even if different video scenes coded at different frame rates are considered in the test set.     

按行程速比系数设计平面曲柄滑块机构的解析法

利用平面曲柄滑块机构中各有关点的坐标之间的关系，提出了一种按行程速比系数设计平面曲柄滑块机构的解析法。与现有解析法相比，该方法解题原理简单明了，计算简便，易于被工程设计人员所接受，具有较好的实用价值。     

A novel microstrip ring hybrid incorporating a PBG cell

An experimental investigation of a novel compact microstrip 180° ring hybrid incorporating a one-dimensional (1-D) slow-wave structure, in the form of perforations on the ring itself, is presented. The size of the hybrid is reduced by 23% due to the slow-wave effect, and this size reduction technique has potential applications in MICs and MMICs. The measured insertion loss is comparable to that of a conventional microstrip hybrid     

X-Y工作台建模与仿真

机电系统的建模与仿真是当前的研究热点之一.X-Y工作台是一种机电传动系统,文章以它为例,首先建立了数学模型,然后将其转换成Simulink仿真模型,并讨论了在忽略摩擦力情况下的仿真特性.Stribeck模型是最常用的摩擦模型,LuGre模型是目前最完善的摩擦模型,Karnopp模型是一种近似模型,适用于工程实践.我们先后建立了这三种模型的仿真模型并带入到工作台的仿真模型中,对仿真运行的结果进行分析,与文献和实验得到的结果基本相符,从而证实建模与仿真是工程分析的一种有效手段.     

新型缓蚀杀菌剂双季铵盐在油田中的应用

从双季铵盐的结构、合成以及由其特殊结构所带来的奇特界面吸附(气/液、固/液界面吸附)特性和化学性质,阐述了新型缓蚀杀菌剂双季铵盐的缓蚀、杀菌机理和作为油田注水缓蚀杀菌剂的研究现状,同时论述了其在油田其它领域(如:驱油,含油污水浮选等)中的应用前景。     

强化设备外绝缘,提高电网抗污闪能力的技术对策

大量运行经验也是建立在“一年一清扫”的绝缘配置上．所以我国电网外绝缘的配置仅是在一般天气条件下防止电网污闪事故的最低设防，而难以抵御灾害性浓雾．特别是伴有湿沉降天气的侵害．这就是上世纪90年代以来我国电网按现行污区图进行凋爬和配置后仍发生三次大面积污闪事故和局部区域污闪事故仍年年发生的根本原因。……“要真正实现把‘清扫作为绝缘裕度留给运行，的要求，这是我国电网防污闪工作方针和政策的重大调整．其最终目的是落实‘绝缘到位．留有裕度，的基本原则，真正杜绝电网大面积污闪事故．使电网的防污闪工作更有效，使输变电工程的基建和运行综合经济效益最佳。”     

淀粉-丙烯酸接枝共聚物耐盐性能研究

研究了淀粉-丙烯酸接枝共聚物的耐盐性及其改进方法.实验结果表明:淀粉-丙烯酸接枝共聚物的糊料中加入5%无水硫酸钠黏度保留值为68.5%;共聚时加入一定量的丙烯酸十八酯可以提高共聚物的耐盐性;用羟丙基淀粉代替原淀粉的共聚产物对提高耐盐性效果更明显,取代度越高耐盐性能越好;用羟丙基淀粉代替原淀粉,同时加入丙烯酸十八酯的共聚产物耐盐性能更好.用取代度0.2的羟丙基淀粉,在丙烯酸十八酯用量为丙烯酸的2%的条件下合成共聚物,在其糊液中加入5%无水硫酸钠,黏度保留值可达93.1%.