Star sensor is an avionics instrument used toprovide the absolute 3-axis attitude of a spacecraft by utiliz-ing star observations. The key function is to recognize theobserved stars by comparing them with the referenc...Star sensor is an avionics instrument used toprovide the absolute 3-axis attitude of a spacecraft by utiliz-ing star observations. The key function is to recognize theobserved stars by comparing them with the reference cata-logue. Autonomous star pattern recognition requires thatsimilar patterns can be distinguished from each other with a small training set. Therefore, a new method based on neural network technology is proposed and a recognition systemcontaining parallel backpropagation (BP) multi-subnets isdesigned. The simulation results show that the method per-forms much better than traditional algorithms and the pro-posed system can achieve both higher recognition accuracyand faster recognition speed.展开更多
The log-polar transform （LPT） is introduced into the star identification because of its rotation invariance. An improved autonomous star identification algorithm is proposed in this paper to avoid the circular shift...The log-polar transform （LPT） is introduced into the star identification because of its rotation invariance. An improved autonomous star identification algorithm is proposed in this paper to avoid the circular shift of the feature vector and to reduce the time consumed in the star identification algorithm using LPT. In the proposed algorithm, the star pattern of the same navigation star remains unchanged when the stellar image is rotated, which makes it able to reduce the star identification time. The logarithmic values of the plane distances between the navigation and its neighbor stars are adopted to structure the feature vector of the navigation star, which enhances the robustness of star identification. In addition, some efforts are made to make it able to find the identification result with fewer comparisons, instead of searching the whole feature database. The simulation results demonstrate that the proposed algorithm can effectively acceldrate the star identification. Moreover, the recognition rate and robustness by the proposed algorithm are better than those by the LPT algorithm and the modified grid algorithm.展开更多
网红村是依托网络媒体吸引外部资金、信息和人员等资源集聚并带动该地区乡村发展的新发展模式,对完善乡村振兴投入机制,培育乡村新产业新业态具有重要意义.本文利用Python爬虫获取主流社交平台2018—2023年间有关乡村的评论文本、点赞...网红村是依托网络媒体吸引外部资金、信息和人员等资源集聚并带动该地区乡村发展的新发展模式,对完善乡村振兴投入机制,培育乡村新产业新业态具有重要意义.本文利用Python爬虫获取主流社交平台2018—2023年间有关乡村的评论文本、点赞量、转发量等信息以识别网红村,运用内容分析法、核密度分析和空间分析等方法探究网红村的空间分异特征,进而分析要素影响及作用过程,揭示其机理,最后提出网红村可持续发展的新思考.结果显示:1)2018—2023年间识别的网红村数量共有689个,其空间分异受到地形、气候和河流等内部要素的基础性作用以及受到城市群、道路交通和网络媒体等外部要素的催化作用,总体呈现“一心两带”的空间分布格局.2)利用Rost Content Ming 6提取网红村评论文本特征词可将其划分为自然景观类、文化民俗类和乡土意象类网红村.其中自然景观类网红村拥有独特的山水、气候和植物景观,在空间上形成两个高密度区和多个次高密度区的空间格局;文化民俗类网红村拥有璀璨的民族历史文化、节庆民俗等文化资源,在空间分布上形成一个团状局部高值区、四个片状组团的空间特征;乡土意象类网红村依赖村庄地方性元素和生活方式营造出中国传统乡村意境,在江浙地区、北京市、河南省以及川渝地区形成高核密度区.3)本文从自然景观类网红村应注重自然景观原生化、文化民俗类网红村应注重乡土文化体验化、乡土意象类网红村应注重乡村生活原真化这三个方面提出了从“流量”到“留量”的网红村可持续发展新思路.展开更多
文摘Star sensor is an avionics instrument used toprovide the absolute 3-axis attitude of a spacecraft by utiliz-ing star observations. The key function is to recognize theobserved stars by comparing them with the reference cata-logue. Autonomous star pattern recognition requires thatsimilar patterns can be distinguished from each other with a small training set. Therefore, a new method based on neural network technology is proposed and a recognition systemcontaining parallel backpropagation (BP) multi-subnets isdesigned. The simulation results show that the method per-forms much better than traditional algorithms and the pro-posed system can achieve both higher recognition accuracyand faster recognition speed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61172138 and 61401340)the Open Research Fund of the Academy of Satellite Application,China(Grant No.2014 CXJJ-DH 12)+3 种基金the Fundamental Research Funds for the Central Universities,China(Grant Nos.JB141303 and201413B)the Natural Science Basic Research Plan in Shaanxi Province,China(Grant No.2013JQ8040)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130203120004)the Xi’an Science and Technology Plan,China(Grant.No CXY1350(4))
文摘The log-polar transform （LPT） is introduced into the star identification because of its rotation invariance. An improved autonomous star identification algorithm is proposed in this paper to avoid the circular shift of the feature vector and to reduce the time consumed in the star identification algorithm using LPT. In the proposed algorithm, the star pattern of the same navigation star remains unchanged when the stellar image is rotated, which makes it able to reduce the star identification time. The logarithmic values of the plane distances between the navigation and its neighbor stars are adopted to structure the feature vector of the navigation star, which enhances the robustness of star identification. In addition, some efforts are made to make it able to find the identification result with fewer comparisons, instead of searching the whole feature database. The simulation results demonstrate that the proposed algorithm can effectively acceldrate the star identification. Moreover, the recognition rate and robustness by the proposed algorithm are better than those by the LPT algorithm and the modified grid algorithm.
文摘网红村是依托网络媒体吸引外部资金、信息和人员等资源集聚并带动该地区乡村发展的新发展模式,对完善乡村振兴投入机制,培育乡村新产业新业态具有重要意义.本文利用Python爬虫获取主流社交平台2018—2023年间有关乡村的评论文本、点赞量、转发量等信息以识别网红村,运用内容分析法、核密度分析和空间分析等方法探究网红村的空间分异特征,进而分析要素影响及作用过程,揭示其机理,最后提出网红村可持续发展的新思考.结果显示:1)2018—2023年间识别的网红村数量共有689个,其空间分异受到地形、气候和河流等内部要素的基础性作用以及受到城市群、道路交通和网络媒体等外部要素的催化作用,总体呈现“一心两带”的空间分布格局.2)利用Rost Content Ming 6提取网红村评论文本特征词可将其划分为自然景观类、文化民俗类和乡土意象类网红村.其中自然景观类网红村拥有独特的山水、气候和植物景观,在空间上形成两个高密度区和多个次高密度区的空间格局;文化民俗类网红村拥有璀璨的民族历史文化、节庆民俗等文化资源,在空间分布上形成一个团状局部高值区、四个片状组团的空间特征;乡土意象类网红村依赖村庄地方性元素和生活方式营造出中国传统乡村意境,在江浙地区、北京市、河南省以及川渝地区形成高核密度区.3)本文从自然景观类网红村应注重自然景观原生化、文化民俗类网红村应注重乡土文化体验化、乡土意象类网红村应注重乡村生活原真化这三个方面提出了从“流量”到“留量”的网红村可持续发展新思路.
