基于支持向量机的地震灾害自动成图方法

地震灾害风险评估中有许多定性图件,目前常用的成图方法是根据研究区的离散点钻孔结果人工勾画,费时费力;或对离散点钻孔结果强制赋予0、1数值,然后进行插值成图,其从逻辑上不能真实反映场地的客观情况。基于支持向量机技术,该文提出了使用分类工具SVC,将不同结果的离散点钻孔在空间上进行合理分类的自动成图方法。相较于传统方法,该方法效率高,成本低。     

基于城区行人安全的无人机运行风险评估

为保证无人机(UAV)在城市区域安全运行,建立基于城区行人安全的UAV运行风险评估模型。首先,分析UAV在城区运行时对行人造成的威胁,进行风险建模;其次,引入风险衡量标准,建立风险成本计算指标;然后,生成UAV城区运行风险地图;最后,以基于风险规避的UAV路径规划为应用场景,求解UAV在城区中的飞行任务路径。结果表明:不同区域的风险成本区别明显,风险程度与人群密度、环境遮蔽效果有关;与传统的距离最短路径规划方法相比,考虑运行风险的路径规划方法能够使UAV的飞行路径避开危险程度较高的区域,提高UAV在城区运行的安全性。     

应急社会动员研究热点与趋势的知识图谱分析

为更准确地为应急社会动员研究提供参考方向,以中国知网(CNKI)数据库中中文社会科学引文索引(CSSCI)期刊收录的296篇应急社会动员研究文献为样本,综合运用文献计量、知识图谱等可视化分析方法,系统分析该领域研究的历年发文数量、期刊分布、发文机构、研究议题与热点、变化趋势等情况。结果表明:2003年以来,应急社会动员研究的年发文数量经历3个阶段的发展,期刊分布日渐广泛,发文机构比较松散;研究议题愈来愈多,主要集中在突发事件响应阶段应急社会动员的触发情景、实施机制和功能效果;热点议题不断涌现,深度广度持续拓展,研究方法相对局限;后续研究发展空间较大,可侧重于应急社会动员的多方法、全过程、智慧化等研究内容。     

A mathematical structure for analyzing maps

The growing use of computers in environmental management is profoundly changing data collection procedures, analytic processes, and even the decision-making environment itself. The emerging technology of geographic information systems (GIS) is expanding this revolution to integrate spatial information fully into research, planning, and management of land. In one sense, this technology is similar to conventional map processing involving traditional maps and drafting aids, such as pens, rub-on shading, rulers, planimeters, dot grids, and acetate sheets for light-table overlays. In another sense, these systems provide advanced analytic capabilities, enabling managers to address complex issues in entirely new ways. This report discusses a fundamental approach to computer-assisted map analysis that treats entire maps as variables. The set of analytic procedures for processing mapped data forms a mathematical structure analogous to traditional statistics and algebra. All of the procedures discussed are available for personal computer environments.     

DEFINING REGIONAL POPULATIONS OF LAKES FOR THE ASSESSMENT OF SURFACE WATER QUALITY1

ABSTRACT: Topographic maps are commonly used to define populations of lakes in regional surveys of surface water quality. To illustrate the effect of different maps on that process, we compared the lakes represented on the 1:250,000-scale maps used for the Northeast Region of the Eastern Lake Survey—Phase I (ELS-I) to the lakes on a sample of large-scale maps (1:24,000 or 1:62,500). Lake areas at or near the lower limit of representation delimited “smallest-lake” values for the compared 1:250,000-scale maps. The regional median for these values was 4.5 hectares (ha) and ranged from 0.6 to 24.8 ha. Lake representation is influenced by cartographic limitations such as map scale, age, and complexity as well as the inherent variability of waterbodies (e.g., water level fluctuations or the creation of reservoirs, beaver impoundments, and oxbows). The total number of lakes on large-scale maps increased markedly as lake area decreased. Approximately 15,700 of the estimated 29,000 lakes in the EPA's Northeast Region were 1 to 4 ha in area. Because maps affect the size distribution of lakes included in a regional survey and because lake areas are thought to modify lake chemistry, maps ultimately affect the estimates of regional surface water quality.     

PCA-SOM耦合模型在湖泊水质评价中的应用

富营养化是湖泊沼泽化进程加快的重要因素之一,而湖泊富营养化的预防与治理已经成为世界性的难题。湖泊富营养化评价是湖泊治理的基础,它可以为治理工作提供科学的依据。该文以乌梁素海为例,采用主成分——SOM人工神经网络耦合模型进行富营养化评价。先建立富营养化评价指标体系,然后用主成分分析剔除存在相关性、信息重叠的指标,再将利用主成分分析得到的具有代表性的主成分指标代替原来的评价指标,输入到自组织特征映射网络模型中,最后对富营养化状况进行聚类分析。所得结果与实际相吻合。该方法能根据实测资料对湖泊富营养化状况客观地分类并计算出评价权值,避免了选取评价指标时的主观随意性。     

Statistical selection of perimeter-area models for patch mosaics in multiscale landscape analysis

This paper presents a statistical method for detecting distinct scales of pattern for mosaics of irregular patches, by means of perimeter–area relationships. Krummel et al. (1987) were the first to develop a method for detecting different scaling domains in a landscape of irregular patches, but this method requires investigator judgment and is not completely satisfying. Grossi et al. (2001) suggested a modification of Krummel's method in order to detect objectively the change points between different scaling domains. Their procedure is based on the selection of the best piecewise linear regression model using a set of statistical tests. Even though the change points were estimated, the null distributions used for testing purposes were those appropriate for known change points. The present paper investigates the effect that estimating the change points has on the underlying distribution theory. The procedure we suggest is based on the selection of the best piecewise linear regression model using a likelihood ratio (LR) test. Each segment of the piecewise linear model corresponds to a fractal domain. Breakpoints between different segments are unknown, so the piecewise linear models are non-linear. In this case, the frequency distribution of the LR statistic cannot be approximated by a chi-squared distribution. Instead, Monte Carlo simulation is used to obtain an empirical null distribution of the LR statistic. The suggested method is applied to three patch types (CORINE biotopes) located in the Val Baganza watershed of Italy.