SHORT COMMUNICATION CHEMOMETRIC ASPECTS OF AN ENVIRONMENTAL STUDY

The application of several chemometric topics in connection with an environmental study is described.Atwo-way ANOVA is used to show the irregularity of the distribution of heavy metals in the rural soilsaround a lead smelter.Multivariate statistical methods are also applied to show significant correlationsbetween metals and the wind direction.Principal components analysis and Varimax rotation seem toconfirm the validity of the conclusions.     

Sampling variation of principal components

The convenience of reducing the dimension of a data matrix by principal component analysis invites substantive interpretation of the coefficients of the components. To test the consistency of component coefficients, 10 samples of approximately 25, 50, 100, and 200 items each were randomly drawn, with replacement, from a source sample consisting of 2086 subalkaline asalt analyses. From each sample principal components were calculated using 9 major oxides as variables. Although the eigenvalues are remarkably consistent, both across and within sample size groups, the coefficients of the eigenvectors are subject to considerable sample variance. It is sometimes assumed that the coefficients of the components calculated from small samples are well enough known to be used in detailed petrological interpretation. Our results indicate that the validity of this assumption should be tested in each specific research even when rather large samples are used. The testing procedure used here is suitable of a sufficiently large reservoir of sample items is available; in the absence of such a reservoir complete simulation could be used.     

GPS/GLONASS卫星导航系统组合定位的定权方法研究

正确合理地确定观测值的权是GPS/GLONASS导航系统组合定位中的一个关键技术问题。本文对GPS/GLONASS导航系统组合定位中几种常用的定权方法进行了比较分析,并以GPS/GLONASS的实测数据为例进行了实验,结果表明:在GPS/GLONASS导航系统组合定位中等精度定权的定位结果精度较差,卫星高度角定权和误差分布律概率密度函数定权后的定位结果精度相当,但较等精度定权法的定位精度都有所提高,赫尔默特方差分量估计法定权的定位结果精度最优。     

Work,Home, and Market: The Social Transformation of Housing Space in Guangzhou,China

Principal components analysis of small-area data provided by China's 2000 Population Census shows that major new economic and social forces largely shape the spatial composition of housing in Guangzhou. This is generally manifested in a series of concentric rings: the old urban core, the middle zone of reform housing, and the outer ring of new commodity housing. In addition, urban villages punctuate the metropolitan landscape. Corresponding analysis of sociodemographic attributes depict a metropolis in transition, with market elements and choice-based housing decisions beginning to impinge on the urban fabric. However, the deeply entrenched socialist institutions established during the early years of the People's Republic ensure the continuing dominance of the workplace and occupational attributes as factors structuring China's metropolitan space.     

Using Cooperative Water Quality Data for a Holistic Understanding of Rivers and Streams: A Study of the Neponset River,Massachusetts

Water quality studies seeking to identify modes or processes of river systems often use targeted, research-designed, high-frequency data, whereas most water quality data today are collected for monitoring and reporting requirements are of low frequency and are collected through cooperative and volunteer programs. There exists in this situation an information gap between the science of understanding river system dynamics and the collection of data in most of these systems. Using data collected by volunteers in the Neponset Watershed (Massachusetts, U.S.), we demonstrate that multivariate analysis is a viable option for enhancing the use and information of spatially distributed, long-term monitoring data sets common in the United States. Additionally, the geographic, environmental, and time line information inherent in these community-maintained data leads to a more complete picture of river and stream dynamics. Principal component analyses of three distinct reaches with different channel characteristics and surrounding environments demonstrate differences in dominant modes, with undeveloped stretches driven by seasonal processes, and other stretches exhibiting organic or nutrient sources. This type of information can bridge gaps from problem identification or monitoring to a more complete understanding of river system processes influencing water quality, thereby leading to better stewardship of resources.     

Integrative inversion of land surface component temperature

Land surface temperature (LST) was a key parame-ter in the study of energy fluxes and substance ex-change between the atmosphere and the ground. Re-trieving LST accurately was the main task of infrared remote sensing these years. According to the request of environmental monitor and global change study, the target was specified that the sea surface temperature (SST) should be accurate to 0.3 K, and the land sur-face temperature (LST) should be accurate to 1K in the near future[1]. Sea su…     

An empirical discriminant method applied to sedimentary-rock classification from major-element geochemistry

Classification of sandstones, greywackes, pelites, limestones, dolomites, and acid-igneous and basicigneous rocks, using a literature sample of 183 post-1920 analyses for the 11 major oxides has achieved an 80-percent success rate. The method is based on nonparametric estimation of a probability density function for each category to be classified, using the Bayes decision rule. The method is suitable for use with small training sets and gives much improved results over a linear discriminant function. Classification following data compression using principal components also has given satisfactory recognition rates.     

A fuzzy–random analysis model for seismic performance of framed structures incorporating structural and non‐structural damage

Past earthquake experiences indicate that most buildings designed in accordance with modern seismic design codes could survive moderate‐to‐strong earthquakes; however, the financial loss due to repairing cost and the subsequent business interruption can be unacceptable. Designing building structures to meet desired performance targets has become a clear direction in future seismic design practice. As a matter of fact, the performance of buildings is affected by structural as well as non‐structural components, and involves numerous uncertainties. Therefore, appropriate probabilistic approach taking into account structural and non‐structural damages is required. This paper presents a fuzzy–random model for the performance reliability analysis of RC framed structures considering both structural and non‐structural damages. The limit state for each performance level is defined as an interval of inter‐storey drift ratios concerning, respectively, the non‐structural and structural damage with a membership function, while the relative importance of the two aspects is reflected through the use of an appropriate cost function. To illustrate the methodology, herein the non‐structural damage is represented by infill masonry walls. The probabilistic drift limits for RC components and masonry walls from the associated studies are employed to facilitate the demonstration of the proposed model in an example case study. The results are compared with those obtained using classical reliability model based on single‐threshold performance definition. The proposed model provides a good basis for incorporating different aspects into the performance assessment of a building system. Copyright © 2005 John Wiley & Sons, Ltd.     

主成分分析法在地质灾害危险性综合评价中的应用

介绍了主成分分析法的分类原理和实施步骤以及多指标体系中指标的选取,针对地质灾害的危险性,建立了评价的多指标体系和分级特征,同时分析了该方法在地质灾害危险性综合评价中的应用方法与过程.并通过对某高速公路沿线地质灾害危险性进行分段综合评价,给出了建设工程可能诱发或加剧的地质灾害和建设工程本身可能遭受的地质灾害危害的程度.证明该方法在地质灾害危险性综合评价中是切实可行的.