粘土矿物在过去环境变化研究中的应用

粘土矿物是一种广泛分布于地表的沉积物,其组合及含量的变化记录了源区过去气候环境变化的信息。因此,可以根据粘土矿物的含量和组合变化等信息推知其形成时期的气候环境,重建古环境,揭示气候环境演变的规律。粘土矿物是一种研究古环境演化重要的代用指标,在过去气候环境变化研究中有广阔的应用前景。     

跨平台地图缓存一体化研究与应用

地图缓存技术是WebGIS中广泛采用的关键技术,然而不同平台的地图缓存应用给数据的生产和维护更新带来了诸多不便.针对此问题,本文从地图缓存的生成算法出发,研究了跨平台地图缓存一体化技术路线和实现方法,分别探讨了服务器端一体化和客户端一体化两种方式,旨在提高基础数据生成和应用服务的效率.结果表明本文的成果为实现跨平台缓存一体化提供了一种可行有效地解决办法.     

中国过去3ka冷暖千年周期变化的自然证据及其集成分析

基于集成分析的思想，对不同时间分辨率的自然信息所反映的过去 3ka我国冷暖变化进行综合分析，划分了百年尺度上过去 3ka冷暖变化的阶段，进而发现冷暖变化呈现 1．3～1.35ka的重现周期，每个周期包含相继出现的 4冷暖阶段：持续300～350 a的暖期、550～600 a的冷期、 200～250 a的暖期和200 a左右的冷期。每个冷暖期中发生的相对冷暖事件也服从 1．3～1．35ka周期。在冷暖变化幅度上，300～350 a的暖期较200～250 a的暖期显著，550～600 a的冷期较200 a左右的冷期显著。目前处在长度为200～250 a的暖期中，其特点可以与2．7～2．5kaBP和 1．40～1．15kaBP的暖期相类比。     

采用条件分位数调整法合并二类气候代用资料的初步分析*

本文采用条件分位数调整法,对二类气候代用资料,华山树木年轮年表和西安旱涝等级序列进行合并尝试,既最大限度地利用在年轮资料中的连续变化信息,又能使历史文献资料可以与其相互补充、校准,从而使得合并出来的序列更有助于对过去气候的重建。     

Sr的地球化学指示意义及其应用

综述了Sr元素及其同位素在地球化学各主要研究领域的应用 ,基本反映了其在近期最新的研究进展。Sr在地球化学领域应用广泛 ,对于解决当前该领域许多悬而未决的问题有着不可替代的作用 ,是一种重要的研究手段与方法。尤其对于Sr在黄土沉积研究中的应用 ,笔者结合自己的实际工作 ,提出了自己的见解。     

最低成本Internet实验室的建设

介绍一种最低成本 Internet实验室的建设方案。该方案适用于一般的大、中、小学 ,核心是使目前广泛使用的 Novell网支持 TCP/ IP协议 ,采用代理服务器通过拨号方式进入 Internet,使建设费和使用费大大降低。     

Dinosterol δD values in stratified tropical lakes (Cameroon) are affected by eutrophication

In freshwater settings, dinosterol (4α,23,24-trimethyl-5α-cholest-22E-en-3β-ol) is produced primarily by dinoflagellates, which encompass various species including autotrophs, mixotrophs and heterotrophs. Due to its source specificity and occurrence in lake and marine sediments, its presence and hydrogen isotopic composition (δD) should be valuable proxies for paleohydrological reconstruction. However, because the purity required for hydrogen isotope measurements is difficult to achieve using standard wet chemical purification methods, their potential as a paleohydrological proxy is rarely exploited. In this study, we tested δD values of dinosterol in both particulate organic matter (POM) and sediments of stratified tropical freshwater lakes (from Cameroon) as a paleohydrological proxy, the lakes being characterized by variable degrees of eutrophication. In POM and sediment samples, the δD values of dinosterol correlated with lake water δD values, confirming a first order influence of source water δD values. However, we observed that sedimentary dinosterol was D enriched from ca. 19 to 54‰ compared with POM dinosterol. The enrichment correlated with lake water column conditions, mainly the redox potential at the oxic–anoxic interface (E_h OAI). The observations suggest that paleohydrologic reconstruction from δD values of dinosterol in the sediments of stratified tropical lakes ought to be sensitive to the depositional environment, in addition to lake water δD values, with more positive dinosterol δD values potentially reflecting increasing lake eutrophication. Furthermore, in lake sediments, the concentration of partially reduced vs. non-reduced C₃₄ botryococcenes, stanols vs. stenols, and bacterial (diploptene, diplopterol and ββ-bishomohopanol) vs. planktonic/terrestrial lipids (cholesterol, campesterol and dinosterol) correlated with E_h OAI. We suggest using such molecular proxies for lake redox conditions in combination with dinosterol δD values to evaluate the effect of lake trophic status on sedimentary dinosterol δD values, as a basis for accurately reconstructing tropical lake water δD values.     

Urban social vulnerability assessment with physical proxies and spatial metrics derived from air- and spaceborne imagery and GIS data

Risk management in urban planning is of increasing importance to mitigate the growing amount of damage and the increasing number of casualties caused by natural disasters. Risk assessment to support management requires knowledge about present and future hazards, elements at risk and different types of vulnerability. This article deals with the assessment of social vulnerability (SV). In the past this has frequently been neglected due to lack of data and assessment difficulties. Existing approaches for SV assessment, primarily based on community-based methods or on census data, have limited efficiency and transferability. In this article a new method based on contextual analysis of image and GIS data is presented. An approach based on proxy variables that were derived from high-resolution optical and laser scanning data was applied, in combination with elevation information and existing hazard data. Object-oriented image analysis was applied for the definition and estimation of those variables, focusing on SV indicators with physical characteristics. A reference Social Vulnerability Index (SVI) was created from census data available for the study area on a neighbourhood level and tested for parts of Tegucigalpa, Honduras. For the evaluation of the proxy-variables, a stepwise regression model to select the best explanatory variables for changes in the SVI was applied. Eight out of 47 variables explained almost 60% of the variance, whereby the slope position and the proportion of built-up area in a neighbourhood were found to be the most valuable proxies. This work shows that contextual segmentation-based analysis of geospatial data can substantially aid in SV assessment and, when combined with field-based information, leads to optimization in terms of assessment frequency and cost.     

利用插值法建立历史旱涝格点资料的可行性

主要利用《中国近五百年旱涝分布图集》等历史文献旱涝等级资料,采用气候学分析中常用的插值方法,建立中国东部地区(106°—122°E、25°—41°N)历史时期旱涝等级格点场资料,试图从大尺度的时空变化上,分析比较插值前后资料的结构和特征方面的异同,以说明采用格点资料对中国东部地区进行古气候分析的可行性。采用普通Kriging插值法,对1470—2000年中国东部地区旱涝等级资料进行空间插值。通过交叉验证,分析了站点实际值与估算值间的平均绝对误差,说明采用Kriging插值法将站点旱涝等级资料网格化是可行的;在获取插值结果后,采用数理统计分析方法,比较了插值前站点资料与插值后网格点资料的要素场时空特征,其时间变化趋势的一致性及空间分布的无漂移,进一步说明采用该插值方法是可行的。