我国地球空间数据框架的设计思想、技术路线及若干理论问题讨论   总被引：7，自引：1，他引：6  

胡鹏  胡毓钜  杨传勇  吴艳兰 《武汉大学学报(信息科学版)》2002,27(3):283-288

根据当前我国基础地理信息系统的发展趋势,讨论了1;1万,1：5万,1：25万及1：100万金字塔多层,多分辨率基础地理信息系统的设计思路,即基于数字影像,数字栅格地图（DRG）和DEM及若干层数字线划图的矢,栅集成（2维或3维）框架结构系统,提出了建设可持续发展的全国及各省级基础地理信息系统技术路线;讨论了这一技术流程中涉及的重要的GIS理论问题。  相似文献   

AE指数非线性预报的探讨   总被引：2，自引：2，他引：0  

周荣茂  高玉芬 《地震地磁观测与研究》1997,18(2):45-52

本文运用径向基函数法和邻点加权拟合法构造预测模型，利用ＡＢ指数对地磁活动的非线性预测的可能性进行了探讨。  相似文献   

An elliptical basis function network for classification of remote sensing images     

Jian-Cheng?LuoEmail author  Yee?Leung  Jiang?Zheng  Jiang-Hong?Ma 《Journal of Geographical Systems》2004,6(3):219-236

An elliptical basis function (EBF) network is employed in this study for the classification of remotely sensed images. Though similar in structure, the EBF network differs from the well-known radial basis function (RBF) network by incorporating full covariance matrices and employing the expectation-maximization (EM) algorithm to estimate the basis functions. Since remotely sensed data often take on mixture-density distributions in the feature space, the network not only possesses the advantage of the RBF mechanism, but also utilizes the EM algorithm to compute the maximum likelihood estimates of the mean vectors and covariance matrices of a Gaussian mixture distribution in the training phase. Experimental results show that the EM-based EBF network is more effective in training and simpler in structure than an RBF network constructed for the same task.The research was supported by grant 40101021 from the Natural Science Foundation of China, and grant 2002AA135230 from Hi-Tech research and development program of China. The authors would like to thank the reviewers for their valuable comments.  相似文献   

ODD AND EVEN SYMMETRY OF ATMOSPHERIC CIRCULATION—THEORETICAL BASIS AND CLIMATIC CHARACTERISTICS          下载免费PDF全文

管兆勇)  徐建军  王盘兴) 《Acta Meteorologica Sinica》1994,(2)

Analysis is done of the distribution of odd and even symmetric components of circulations on a global basis in termsof observations and technique for the odd/even symmetry,indicating that climatic features of the component patternsand their temporal evolution are able to reveal their influence of land-sea discrepancy in the Northern and SouthernHemispheres,the time scale of atmospheric response to radiation heating,circulation waveform structure and seasonaladjustment of global circulation.  相似文献   

Statistical analysis in classification of bituminous coal     

Gui Zhen Men 《Mathematical Geology》1991,23(1):71-76

Hundreds of samples and 17 variables collected from coalfields of major coal-bearing strata over China except for Tibet and Taiwan, were used in this study. The dry, ash-free basis volatile matter (V ^r) and caking index (G _(RI)) were chosen by means of correlation analysis and stepwise discriminatory analysis as major indices of a new classification. By means of the optimum section, the boundary value of the axis of ordinate (G _(RI)) and axis of abscissas (V ^r) can be determined in the classification system. Thus, aV ^r –G _(RI) classification scheme diagram was formed and bituminous coal was divided into nine classes. Use of correspondence analysis reduced dimensions of sample-expressive space without losing initial information. The trend on the factor surface of samples shows that the classification obtained from correspondence analysis conforms to theV ^r –G _(RI) classification result and further verified the dependability of classification by two indices. At the same time, a certain relationship between the properties of a great variety of coal and their attributes can be explained. Hence, bituminous coal classification becomes more scientific, reasonable, and practical than before.  相似文献   

玉屏厂址地区龙卷风参数估算与分析          下载免费PDF全文

黄晨然  朱军  向淑君  李霄  夏阳 《中低纬山地气象》2023,47(4):46-50

利用玉屏核电站厂址周围3个经纬度区域范围内1950-2021年期间的龙卷风调查资料,采用富士达F等级划分法评定龙卷风级别,按照《核电厂厂址选择的极端气象事件（HAD101/10）》的规定,估算出核电站设计基准龙卷风相关参数和设计基准等级。结果表明：玉屏核电站厂址区域设计基准龙卷风最大风速估算值为63.9m/s（对应10-7概率值）,总压降为29.5hPa,压降速率为7.1hPa/s,最大旋转风速为51.8m/s,最大平移速度为12.1m/s,设计基准等级为F2。计算结果为项目设计和建设提供重要理论参考依据。  相似文献   

Response of base‐isolated nuclear structures for design and beyond‐design basis earthquake shaking     

Yin‐Nan Huang  Andrew S. Whittaker  Robert P. Kennedy  Ronald L. Mayes 《地震工程与结构动力学》2013,42(3):339-356

The American Society of Civil Engineers (ASCE) 43‐05 presents two performance objectives for the design of nuclear structures, systems and components in nuclear facilities: (1) 1% probability of unacceptable performance for 100% design basis earthquake (DBE) shaking and (2) 10% probability of unacceptable performance for 150% DBE shaking. To aid in the revision of the ASCE 4‐98 procedures for the analysis and design of base‐isolated nuclear power plants and meet the intent of ASCE 43‐05, a series of nonlinear response‐history analyses was performed to study the impact of the variability in both earthquake ground motion and mechanical properties of isolation systems on the seismic responses of base‐isolated nuclear power plants. Computations were performed for three representative sites (rock and soil sites in the Central and Eastern United States and a rock site in the Western United States) and three types of isolators (lead rubber, Friction Pendulum and low‐damping rubber bearings) using realistic mechanical properties for the isolators. Estimates were made of (1) the ratio of the 99th percentile (90th percentile) response of isolation systems computed using a distribution of spectral demands and distributions of isolator mechanical properties to the median response of isolation systems computed using best‐estimate properties and 100% (150%) spectrum‐compatible DBE ground motions; (2) the number of sets of three‐component ground motions to be used for response‐history analysis to develop a reliable estimate of the median response of isolation systems. The results of this study provide the technical basis for the revision of ASCE Standard 4‐98. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

地表水资源量分析计算     

刘英学 《地下水》2014,(4):153-153

地表水资源量是指河流、湖泊、冰川等地表水体中由当地降水形成的、可以逐年更新的动态水量,用河川天然径流量表示,阐述区域地表水资源量的计算方法,分析了地表水资源量及其分布规律,为加强水资源管理,掌握水资源动态,为决策部门对水资源调度、利用提供依据。  相似文献   

基于数据包络分析的统计预测模型有效性评价          下载免费PDF全文

毛晓敏  尚松浩 《水科学进展》2010,21(5):690-695

统计预测模型是进行中长期水文预报的主要手段之一,在统计预测模型建模过程中面临的一个重要问题是如何从诸多待选模型中挑选出一个预测投入较低、预测精度较高的模型。针对这一多属性综合评价问题,提出了利用数据包络分析中的CCR模型进行水文统计预测模型综合评价的方法。模型的输入指标包括预测因子指标和模型参数指标,输出指标为模型精度评价指标,评价结果为模型的相对效率。作为典型案例,对参考作物腾发量预测的20个径向基函数网络模型的有效性进行了评价,结果表明该评价方法是可行的。模型中预测旬参考作物腾发量的关键因子是最高、最低温度,其次是风速,再次是日照时数;将预测时段所属的旬序号作为网络输入可显著提高模型预测精度和相对效率。  相似文献   

新国际地层表简介     

陈殿义  闫玉英  陆浩 《吉林地质》2007,26(2):67-70

2004年国际地层委员会将地球上的岩石划分成两大部分,即显生宇和前寒武系。两者划分的依据不同,显生宇是依据"全球层型剖面和层型点",而前寒武系则是依据"全球标准地层年龄"。为了建立一个"自然的"前寒武纪地质年代表,人们提出了2004~2008年前寒武系划分参考方案,它指明了前寒武纪的研究方向。  相似文献