Regional gravity modeling in terms of spherical base functions

This article provides a survey on modern methods of regional gravity field modeling on the sphere. Starting with the classical theory of spherical harmonics, we outline the transition towards space-localizing methods such as spherical splines and wavelets. Special emphasis is given to the relations among these methods, which all involve radial base functions. Moreover, we provide extensive applications of these methods and numerical results from real space-borne data of recent satellite gravity missions, namely the Challenging Minisatellite Payload (CHAMP) and the Gravity Recovery and Climate Experiment (GRACE). We also derive high-resolution gravity field models by effectively combining space-borne and surface measurements using a new weighted level-combination concept. In addition, we outline and apply a strategy for constructing spatio-temporal fields from regional data sets spanning different observation periods.     

封闭酸溶-等离子体质谱法分析超细粒度地质样品中42个元素

采用封闭压力酸溶，电感耦合等离子体质谱法（ICP—MS）测定了超细样品的42个元素，研究了样品的粒度、分解条件、取样量对分析准确度和精密度的影响。结果表明，用超细粉碎样品（〈30μm），取样量减小至2mg仍能保证取样代表性，总用酸量可减至0．5mL，反应时间也可大大缩短。采用超细样品可更好地发挥ICP—MS技术高灵敏度的效能，从而达到保护环境、降低分析成本、提高分析效率的目的。     

Evaluating explicit and implicit routing for watershed hydro‐ecological models of forest hydrology at the small catchment scale

This paper explores the behaviour and sensitivity of a watershed model used for simulating lateral soil water redistribution and runoff production. In applications such as modelling the effects of land‐use change in small headwater catchments, interactions between soil moisture, runoff and ecological processes are important. Because climate, soil and canopy characteristics are spatially variable, both the pattern of soil moisture and the associated outflow must be represented in modelling these processes. This study compares implicit and explicit routing approaches to modelling the evolution of soil moisture pattern and spatially variable runoff production. It also addresses the implications of using different landscape partitioning strategies. This study presents the results of calibration and application of these different routing and landscape partitioning approaches on a 60 ha forested watershed in Western Oregon. For comparison, the different approaches are incorporated into a physically based hydro‐ecological model, RHESSys, and the resulting simulated soil moisture, runoff production and sensitivity to unbiased error are examined. Results illustrate that both routing approaches can be calibrated to achieve a reasonable fit between observed and modelled outflow. Calibrated values for effective watershed hydraulic conductivity are higher for the explicit routing approach, which illustrates differences between the two routing approaches in their representation of internal watershed dynamics. The explicit approach illustrates a seasonal shift in drainage organization from watershed to more local control as climate goes from a winter wet to a summer dry period. Assumptions used in the implicit approach maintain the same pattern of drainage organization throughout the season. The implicit approach is also more sensitive to random error in soil and topographic input information, particularly during wetter periods. Comparison between the two routing approaches illustrates the advantage of the explicit routing approach, although the loss of computational efficiency associated with the explicit routing approach is noted. To compare different strategies for partitioning the landscape, the use of a non‐grid‐based method of partitioning is introduced and shown to be comparable to grid‐based partitioning in terms of simulated soil moisture and runoff production. Copyright © 2001 John Wiley & Sons, Ltd.     

Representing “Neighborhood”: Growth Coalitions,Newspaper Reporting,and Gentrification in St. Louis

Newspaper reporters are important actors in promoting gentrification. This study of St. Louis examines their use of a prominent representation of neighborhood in this process: dying neighborhoods in need of middle‐class technical salvationists. We examine its use to help drive two processes to promoting gentrification: legitimating restructuring at actual or anticipated sites and isolating “revitalization‐contaminating” communities. We discover this neighborhood representation is applied primarily to legitimate restructuring at specific sites. Revitalization‐threatening neighborhoods, represented differently, indicates this representation is task specific in this city's “gentrification project.”     

遗传算法在点注记自动配置中的应用

从注记配置是一个NP难度问题这一观点出发，尝试性地将遗传算法用于点注记自动配置。在论述了遗传算法基本原理和方法的基础上，结合点注记自动配置的基本模型，讨论了基于遗传算法的点注记自动配置方法，并对其关键性的问题进行了阐述。     

Phase identification and attribute analysis of broadband seismograms at far-regional distances

A trained analyst can frequently provide a rapid assessment of a seismic record and provide identification for many seismic phases. For digital data a challenge is to find methods (or combinations of methods) which can provide equivalent levels of phase identification and attribute analysis. Until now, there have been few discussions on phase attribute analysis for broadband records, even though the character of the major phases has been recognised several decades ago. We introduce a combination of four simple methods into the analysis of broadband seismograms so as to provide a means of improving phase recognition and the full use of broadband information for far-regional distances where the seismograms are particularly complex (because of the influence of the upper mantle discontinuities). For arrival detection we can employ the energy ratios of the short term behaviour to the long-term trend, using the vertical component and horizontal components of unrotated seismic records. We also use auto-regressive analysis to endeavour to separate broadband records into three parts: the seismic signal, microseismic noise and white noise. The higher order auto- and cross-correlation coefficient (representing the similarity of waveform) can be used to identify the presence of seismic phases, by avoiding the influence of the relatively low order correlation of microseismic noise. For each broadband 3-component record a set of complex traces are constructed and then a variety of definitions of instantaneous phase and frequency can be exploited to separate the behaviour of signal and noise. The complex traces can also be used for polarisation analysis. The changes in the character of the eigenvectors are particularly helpful for recognising the phases of broadband records in the far-regional range. The individual methods are quite powerful but when used in combination can provide a very effective means of phase characterisation.     

地图符号视觉变量数学定义的研究

根据拓扑学、图论和集合论的有关定义，对形状、尺寸、方向、密度、亮度、结构、颜色和位置等8种视觉变量给出了数学定义。组合公式表明，由有限的视觉变量组成像元，再由有限的像元组成地图符号，可以获得大量的地图符号，从而说明设计与创造地图符号蕴含巨大的潜力。     

数字环境下地图综合结果自动评价模型的研究与应用

在对数字环境下地图综合的新含义和新任务进行分析的基础上 ,讨论了地图自动综合的评价标准和综合指标 ,提出了一种大比例尺地图综合结果自动评价模型 ,并利用该模型开发了一个评价模块内置到深圳市规划国土局开发研制的地图综合软件 Auto Map中。此模块可对地图各种要素进行地图综合结果自动评价分析。最后利用深圳市 32幅要综合的 1∶ 10 0 0 0的地图对本文提出的模型和开发的模块进行了全面的实验研究。     

遥感图像理解专家系统中面向对象的知识表示

阐述了在遥感图像理解专家系统中，用面向对象的方法表示知识，使得图像分类效率更高