The Fourier Integral Method: An efficient spectral method for simulation of random fields

The Fourier Integral Method (FIM) of spectral simulation, adapted to generate realizations of a random function in one, two, or three dimensions, is shown to be an efficient technique of non-conditional geostatistical simulation. The main contribution is the use of the fast Fourier transform for both numerical calculus of the density spectral function and as generator of random finite multidimensional sequences with imposed covariance. Results obtained with the FIM are compared with those obtained by other classic methods: Shinozuka and Jan Method in 1D and Turning Bands Method in 2D and 3D, the points for and against different methodologies are discussed. Moreover, with the FIM the simulation of nested structures, one of which can be a nugget effect and the simulation of both zonal and geometric anisotropy is straightforward. All steps taken to implement the FIM methodology are discussed.     

An object-oriented knowledge representation structure for exploration data integration

Knowledge representation structure and reasoning processes are very important issues in the knowledge-based approach of integrating multiple spatial data sets for resource exploration. An object-oriented knowledge representation structure and corresponding reasoning processes are formulated and tested in this research on the knowledge-based approach of integrating spatial exploration data. The map-based prototype expert system developed in this study has self-contained knowledge representation structure and inference mechanisms. It is important to distinguish between lack of information and information providing negative evidence for a map-based system because the spatial distribution of data sets are uneven in most cases. Error and uncertainty estimation is also an important component of any production expert system. The uncertainty propagation mechanisms developed here work well for this type of integrated exploration problem. Evidential bellef function theory provides a natural theoretical basis for representing and integrating spatially uneven geophysical and geological information. The prototype system is tested using real mineral exploration data sets from the Snow Lake area, northern Manitoba, Canada. The test results outline the favorable exploration areas successfully and show the effectiveness of the knowledge representation structure and inference mechanisms for the knowledge-based approach.     

对中国大陆区域地磁场提取的认识

本文从球谐函数理论的物理含义、中国地磁数据的分布情况及实际计算结果的分析,提出对当前用球谐函数拟合法提取中国大陆区域地磁异常的几点认识。     

Sampling and Discrete Choice Analysis

Samples used to estimate discrete choice models in geography and regional science are typically assumed to be simple random samples. This assumption is not always met with existing samples. Furthermore, data collection is usually less costly if a stratified sampling strategy is adopted. Existing sampling theory suggests that stratified sampling can affect the consistency of parameter estimates. This paper reviews the salient points of this theory and relates theory to practice by means of a simple example on housing choice by elderly.     

A simultaneous interpretation,by wind speed and direction,of ambient air negative ion density in Athens,Greece

A recently developed data presentation technique, the rectangular wind frequency isopleth diagram, has been applied to examine the effect of wind speed and direction, acting simultaneously, on ambient air negative ion densities. The large negative ion concentration decreases in the majority of directions and wind speed intervals, while that of the small ions increases, as the wind speed increases. The local maxima and minima, occurring in some sectors, are properly discussed.     

Time–frequency representation of earthquake accelerograms and inelastic structural response records using the adaptive chirplet decomposition and empirical mode decomposition

In this paper, the adaptive chirplet decomposition combined with the Wigner-Ville transform and the empirical mode decomposition combined with the Hilbert transform are employed to process various non-stationary signals (strong ground motions and structural responses). The efficacy of these two adaptive techniques for capturing the temporal evolution of the frequency content of specific seismic signals is assessed. In this respect, two near-field and two far-field seismic accelerograms are analyzed. Further, a similar analysis is performed for records pertaining to the response of a 20-story steel frame benchmark building excited by one of the four accelerograms scaled by appropriate factors to simulate undamaged and severely damaged conditions for the structure. It is shown that the derived joint time–frequency representations of the response time histories capture quite effectively the influence of non-linearity on the variation of the effective natural frequencies of a structural system during the evolution of a seismic event; in this context, tracing the mean instantaneous frequency of records of critical structural responses is adopted.The study suggests, overall, that the aforementioned techniques are quite viable tools for detecting and monitoring damage to constructed facilities exposed to seismic excitations.     

基于尺度的GIS空间资料表达模型

介绍了基于层的GIS空间资料表达方法易于进行空间查询与空间分析处理的优点,针对其引起的地图难以进行扩展与图像显示转换困难的缺点,提出了基于尺度(比例尺)的空间资料表达新方法.在基于尺度的空间资料表达方法中,地图可以由空间对象,区域,尺度视图三级尺度模型表达.对尺度方法下的地图结构,地图组织,指标结构,地图扩展等在理论上作了探讨,提出了基于尺度的方法与已广为使用的基于层的方法的有效集合,将有可能成为地理信息表达研究的最重要研究方向.     

p—范分布的近似表示

p-范分布是一个包含拉普拉斯分布、正态分析、均匀分布等常见分布的分布族。用p-范分布描述观测误差的统计特性，只需假定误差的分布为单峰、对称，因此、p-范分布似然平差可以避免事先假定误差的具体分布模式，而在平差过程中确定未知参数及误差的分布具有自适应的特点。但是p-范分布的密度函数比较复杂，不利于理论分析和实际应用。 的研究表明，p-范分布可以近似地表示为拉普拉斯分布与正态分析或正态分布均均匀分布的线性组全。p-范分布与本文给出的近似分布具有相的前四阶矩。由于拉普拉斯分布。正态分布。均匀分布的密度函数都比较简单，用近似分布代替p-范分布会使相关的问题得到简化。     

中国国家自然地图集Internet版的设计和研制

本文系统阐述了国家自然地图集Ｉｎｔｅｒｎｅｔ版的设计和研制过程中的若干问题,包括系统的概念设计、系统开发中的ＷｅｂＧＩＳ技术和策略,系统的主要功能和特色,以及系统维护和更新方案等。本系统从概念设计来看分为服务器端软件模块、浏览器端软件模块、国家自然地图集数据库支持等几个部分。系统开发中采取的ＷｅｂＧＩＳ技术和策略有:兼顾服务器端和客户端的综合型ＷｅｂＧＩＳ策略,基于Ｊａｖａ Ａｐｐｌｅｔ的 ＷｅｂＧＩＳ浏览器开发技术,基于Ｍａｐ Ｏｂｊｅｃｔ(ＭＯ)的ＷｅｂＧＩＳ服务器开发技术等３个方面。在系统的主要功能特色方面,本文从以下５个方面进行了论述:科学有序的内容结构、清晰精练并带导航的界面、富有特色的信息查询功能、多重表达的地图可视化效果、一定的空间信息分析和制图功能。在系统维护和更新方案上,本文从网络技术、数据更新、功能开发３个方面介绍了计划,并对今后的发展趋势进行了展望。