地影模型对导航卫星轨道数值积分的影响及改进     

陈刘成 《武汉大学学报(信息科学版)》2007,32(5):450-453

以RKF7（8）和Adams12阶PECE方法为例，分析了单步法积分器和多步法积分器在圆柱体、双锥形地影模型下，地影边界对导航卫星轨道积分的影响，并提出了相应的改进方法。改进方法原理简单，在3d积分弧段内最大误差优于cm级。  相似文献   

光压摄动计算中地影间断的处理     

王歆  刘林 《紫金山天文台台刊》2000,19(1):19-24

人卫精密定轨中受摄星历（或称精密星历,即状态转移）,可由分析解或数值解提供,相应的定轨方法亦有分析法定轨与数值法定轨之称。对于后者,在一般情况下,现有的常微分方程数值解法（或称积分器）已能满足精度要求,除长弧定轨外,有一定问题是值得注意的,即地影“间断”问题的处理,这关系到如何在保证星历精度的前提下提高计算效率的问题。本文针对这一问题,给出了相应的改进算法,并通过数值验证表明算法的有效性。  相似文献   

雨影区对海南岛西部土地沙漠化影响的风洞实验研究   总被引：6，自引：5，他引：1  

李森  刘贤万  孙武 《中国沙漠》2006,26(2):165-171

风洞系列实验证明,山体雨影区与垂直平板绕流后回流区的作用原理是一致的, 山体雨影区的宽度是山体高度的15 H。据实验结果分析,海南岛西部雨影区形成的原因是季风气流沿山脉迎风坡面爬升冷却,坡脚形成热低压,在背风面回流收敛形成暖高压,气流变性为焚风。海南岛中南部多道山脉的雨影区和中南半岛长山山脉雨影区叠加、交汇后,强化了海南岛西部的干热化并形成热带半干旱气候环境,始终影响着土地沙漠化发展演变。  相似文献   

Fault tectonic analysis of Kii peninsula,Southwest Japan: Preliminary approach to Neogene paleostress sequence near the Nankai subduction zone     

POM‐YONG CHOI  SATOSHI NAKAE  HYEONCHEOL KIM 《Island Arc》2011,20(4):455-476

The southern part of the Outer Zone of Southwest Japan including the Kii peninsula belongs to the tectonic ‘shadow zone’, where fewer conspicuous active faults and less Quaternary sediments develop than in the Nankai subduction zone and Inner Zone of Southwest Japan. In order to study the paleostress sequence of the Kii peninsula, we analyzed fault‐slip data and tension gashes at pilot sites of Early–Middle Miocene forearc sediments and Late Cretaceous accretionary complex. According to the results, six faulting events are reconstructed in sequence: (i) east–west extension (normal faulting); (ii) east–west compression and north–south extension (strike‐slip faulting); (iii) NNW–SSE compression and ENE–WSW extension (strike‐slip faulting); (iv) northeast–southwest compression and northwest–southeast extension (strike‐slip faulting); (v) WNW–ESE compression (strike‐slip or reverse faulting); and (vi) NNE–SSW extension. The north–south to NNW–SSE trending dyke swarm of Middle Miocene age in the Kii peninsula is thought to be related to Event 3, implying that Event 3 was active at least during the Middle Miocene. Because Event 6 is recognized solely at a site, the overall latest faulting event seems to be Event 5. Assuming that the compression results from the motion of the crust or plate, the compression direction of Event 5 is in good accordance with the present‐day WNW crustal velocity vectors of the Kii peninsula. The stress trajectory map of Southeast Korea and Southwest Japan reveals that the current compression directions of the Kii peninsula correspond to the combinatory stress fields of the Himalayan and Philippine Sea tectonic domains.  相似文献   

MAPPING SOLAR ACCESS IN HIGH RELIEF AREAS FOR REGIONAL ENERGY PLANNING*     

Charles C. Ryerson 《The Professional geographer》1984,36(3):345-352

Access to the sun for space heating of structures is controlled, in part, by topographic shadowing in high-relief regions. A simple graphic procedure is presented for mapping shadows on topographic maps for any date and time of day. Comparisons of computed shadows and shadows measured from aerial photography confirm that the mapping procedure is reliable and accurate. Use of the procedure as a solar access inventory tool is illustrated in an area of the Green Mountains, VT.  相似文献   

Theory of edge diffraction in terms of dynamic ray tracing     

P. M. Bakker 《Geophysical Journal International》1990,102(1):177-189

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空间碎片天基光电光学可见条件与预报   总被引：1，自引：0，他引：1  

桑思武  许尤楠  刘艳华  叶小宝 《天文研究与技术》2006,3(3):271-274

随着航天活动的增加，产生的空间碎片也越来越多，空间环境日趋恶化，已经对人类的空间活动构成了威胁。监视测量这些空间碎片，天基光电比地基光电更为有利，而天基光电的光学可见条件与地基光电相比，有相似的，也有不同的，针对天基光电，给出了空间碎片的光学可见条件，即日光条件、地影条件、地光条件、地球背景条件、月光条件。在天基光电轨道特征、光学可见条件及天基光电坐标系已知的情况下，建立起天基光电预报方法。既可用于空间碎片预报，也可以用于空间碎片的轨道识别。  相似文献   

战场环境仿真中基于图像的实时阴影技术     

万刚  曹雪峰  李锋  张挺 《测绘科学技术学报》2007,24(1):18-21

阴影是战场环境仿真中增强真实感的重要手段.分析战场环境中阴影的特点,将其分为静态阴影和动态阴影,根据战场环境仿真对阴影效果实时性和真实感的要求,采用改进的快速光线跟踪算法和预烘焙方法生成光照图,分别实现静态阴影中的地形和地物阴影,采用光源空间透视阴影图技术,改善阴影边缘走样,实时渲染真实的动态阴影.实验结果表明,实现的阴影效果达到了较好的实时性和真实感.  相似文献   

A comparison of usefulness of 2D and 3D representations of urban planning     

Grant Herbert 《制图学和地理信息科学》2013,40(1):22-32

Very little existing literature has addressed the issues of the perceived usefulness of 3D visualizations over 2D and the use of cartographic shadow representations in the planning community. Urban planning has moved toward a 3D, geographic-information-system-centric, and functional decision support framework. This study aims to examine the preferences of urban planning professionals with respect to 2D and 3D visualizations in a case study. The authors built a 3D representation of a proposed building along with the existing urban environment in Queenstown, New Zealand and conducted a usefulness test through a survey and interview. Based on the survey, the study evaluated the degree of task utility perceived in each visualization method, the effect on the mental image, and shadow representation preferences. The findings support the literature that the benefits of using a 2D or 3D model are closely related to the types of planning tasks undertaken. The findings also reveal a complex view of planning activities, suggesting that planners themselves cannot be treated as a single group for research purposes.  相似文献   

基于Matlab的最小相位滤波在处理影区地震中的初步研究     

隆爱军  夏仕安  陈海博  王燚坤 《地震地磁观测与研究》2012,33(5):362-365

研究基于Matlab的最小相位滤波器在处理影区地震中的应用。使用共轭倒序法设计滤波器对合肥地震台记录的中国台湾影区地震进行滤波处理,有效抑制地动噪声干扰,突出地震信号特征,为地震分析提供较好的帮助。  相似文献