运用硼同位素进行古气候重建的研究进展

海水中硼的同位素组成受海水pH控制,海洋生物碳酸盐形成过程中海水的硼主要以B(OH)4-形式进入碳酸盐晶格,该过程不产生同位素分馏,因此海洋生物碳酸盐的硼同位素组成能够反映海水中B(OH)4-的硼同位素组成,进而指示当时海水的pH值,再根据海水与大气间CO2溶解平衡关系可以间接获得当时大气CO2分压。最近十多年来成功地运用生物碳酸盐硼同位素研究了过去20 Ma以来不同时间段古海水pH演化历史以及大气CO2分压的变化历史,使得硼同位素成为研究古气候的新方法。由于大气CO2分压对海水pH变化的响应非常灵敏,必须对各参数的取值进行严格的论证,而且模型本身的合理性及精确性也要进一步讨论。本文详细地介绍了硼同位素-pH方法的理论模型以及近年来运用该方法研究古气候取得的主要成果,同时对模型本身的研究进展也进行了阐述。     

A TREE-RING RECONSTRUCTION OF DROUGHT IN SOUTHERN CALIFORNIA1

ABSTRACT: Indices of annual diameter growth of trees were used to reconstruct drought in southern California back to A.D. 1700. A regional Palmer Drought Index served as predictand and tree-ring indices from eight sites as predictors in multiple linear regression analyses that yielded the prediction (reconstruction) equations. The regression explained 69 percent of the variance in Palmer Index in the period of calibration. The long-term reconstruction indicated that drought was rare in the first half of the current century relative to other discrete 50-year periods, and that based on evidence to date the last half of the 20th century may well turn out to be the most drought prone since A.D. 1700 in southern California.     

洞穴次生化学碳酸盐沉积物-石笋的气候替代指标的意义与不确定性因素

洞穴次生化学碳酸盐(CaCO3)沉积物-石笋、钙华和流石,是一个具有丰富的陆地古气候信息的档案库。洞穴碳酸盐(CaCO3)-石笋古环境重建常用的代用指标有碳、氧稳定同位素、生长速度、纹层厚度和灰度、有机质荧光、微量元素等,利用多种替代指标的环境解译,增加了古气候环境重建的可靠性。本文从测年方法和石笋年代学的研究入手,对石笋的生长速度,沉积速率、纹层厚度、稳定同位素、微量元素等各代用指标指代的气候意义进行了简述,同时,也对洞穴次生化学碳酸盐(CaCO3)沉积物-石笋中各单一代用指标存在的不确定性影响因素进行了探讨。因此,我们认为洞穴动态监测可为洞穴碳酸盐(CaCO3)沉积物的各替代指标的解译提供可靠的依据,充分利用现代洞穴监测的碳酸盐(CaCO3)沉积物的各替代指标,并与现代器测气象资料进行相互对比、并用以校正,是精确或定量解释石笋气候替代指标的关键。     

Risk factors for mortality during the 2002 landslides in Chuuk, Federated States of Micronesia

This study examines health effects resulting from landslides in Chuuk during Tropical Storm Chata'an in July 2002, and suggests strategies to prevent future mortality. In August 2002, we conducted a cross-sectional survey to identify risk factors for mortality during landslides, which included 52 survivors and 40 surrogates for 43 decedents to identify risk factors for death. Findings suggest that 1) females had a higher mortality rate from this event than males, and 2) children aged 5–14 years had a 10-fold increase in mortality when compared with annual mortality rates from all causes. Awareness of landslides occurring elsewhere and knowledge of natural warning signs were significantly associated with lower risks of death; being outside during landslides was not associated with reduced mortality. In Chuuk, improving communication systems during tropical storms and increasing knowledge of natural warnings can reduce the risk for mortality during landslides.     

计算机网络安全中的防火墙技术研究

介绍一些经常性的网络安全问题,以及用一种相应的防御对策——网络防火墙,它技术的核心思想是在不安全的网络环境中构造一个相对安全的子网环境．讨论了实现防火墙的两种主要技术手段：一种是基于分组过滤技术（Packet filtering）,它的代表是在筛选路由器上实现的防火墙功能;一种是基于代理技术（Proxy）,它的代表是应用层网关上实现的防火墙功能．参5．     

经济发展与环境退化的动态演进——环境库兹涅茨曲线研究进展

环境库兹涅茨曲线（EKC）阐述了经济发展和环境退化之间的动态演进过程，即随着经济的发展环境先不断恶化，到达顶点后逐渐改善。从实证研究、计量模型和分解分析三条线索回顾总结了国内外研究成果。随着EKC研究的发展，环境指标从污染指标扩展到资源生态指标和环境效率指标，而实证研究表明并非所有的环境指标和经济变量之间都存在“倒U型”关系。目前计量模型以简化式为多，结构式较少。由于分解分析方法能够定量化各种影响因素对污染排放变化的贡献率，因而在EKC成因研究中日益受到重视。尽管研究取得了较大进展，但生态环境阈值、污染的时空转移、数据处理与模型方法、环境控制政策和管理等方面仍需进一步研究，关键要在数据处理和模型构建方面取得突破。     

ON THE MISMATCH BETWEEN DATA AND MODELS OF HYDROLOGIC AND WATER RESOURCE SYSTEMS1

ABSTRACT: Many difficulties exist in the matching of models with data. This paper identifies elements of this problem and discusses considerations involved in model evaluation. The well known multivariate linear regression model is used to illustrate the distinctions between accuracy and precision and between estimation and prediction (because the model is commonly misused.) No amount of additional data will improve the accuracy of a poor model. A high R², while indicative of a good matching between the observed data and model estimates, is a poor criterion for judging adequacy of the model to make good predictions of future events. Model evaluation also includes the problem of introducing secondary data and proxy variables into a model. Secondary data frequently enter, for example, the mass, energy and water budget equations because of difficulties in measuring the primary variables. Proxy variables arise because of a desire to collapse a vector of incomparable values, say, of water quality into a single number. Review of the above issues indicates that model evaluation is a multi-criterion problem, often imbedded in a larger framework where models are intended to meet multiple objectives. The mismatch of models and data has increasing legal and social consequences.     

防火墙在企业网络安全中的应用

信息网络的安全已成为目前企业至关重要的问题,防火墙技术是保护企业信息安全中最基本、最成熟的一种.本文简要介绍了防火墙的主要技术、防火墙体系结构,并对防火墙的选择方案提出了建议.     

A new market instrument for sustainable economic and environmental development

The regenerative capacity of ecosystems provides a regulatory basis for sustainable economic growth and development. A natural valuation of an ecosystem's services will arise in a market for developmental rights in the ecosystem using a unit of tradable 'right': E-Scrip. The amount of e-scrip needed for a development may be set by Environmental Assessment. The capacity of the ecosystem to regenerate with developmental pressure may be represented by an independent trader or Factor Proxy for the Environment who provides e-scrip to the market.     

徐州钢铁厂附近土壤中重金属及硫的垂向分布特征与磁学响应

对取自徐州钢铁厂附近的土壤样芯进行了比较系统的磁学测量和化学分析.结果表明,土壤样芯中Pb、Cu、Zn、Cd、Bi、Se、Hg、Fe、Mn的含量与磁学参数x、SOFT、SiRM、xARM数值存在着十分相似的垂向变化特征,指示了土壤样芯中高浓度的磁性矿物和重金属是由外源输入引起的;样品中重金属元素含量与磁学参数呈显著相关.土壤样芯中元素S与磁学参数的相关性非常显著,表明土壤中的S与磁性矿物来源相同,但是,是否可以利用土壤的磁学参数作为预测大气中SO2污染程度的代用指标仍需进一步探讨.土壤中铁锰氧化物结合态在一定程度上控制了土壤中Pb、Cu、Zn、Cd、Bi、Se、Hg等重金属元素的生物地球化学循环.