一级动力学反应方程参数估计中若干问题的讨论

在农药的环境行为研究中,常用一级动力学反应方程来模拟农药的降解或残留。本文论述了用线性回归分析法估计一级化学动力学方程参数时存在的初始浓度飘移和非本义最优化问题,讨论了与此相关联的试验设置、安全间隔期、分段模拟和试验数据处理等问题,提出了解决问题的初步设想。     

Long-Term Monitoring of Scots Pine Litter Decomposition Rates Throughout Sweden Indicates Formation of a More Recalcitrant Litter in the South

Decomposition studies were carried out at sites throughout Sweden, including the four Integrated Monitoring sites. Scots pine needle litterbag weight loss measurements over 3 or 5 years were determined at 26 sites and repeated up to 27 times, depending on the site. Humus layer respiration rates were determined for 20 sites in 1987–1989 and repeated in 2007–2008. Partial Least Squares (PLS) regression was used to elucidate the relative importance of climatic and soil factors. Annual needle weight losses decreased only slowly (20–10%) over 3–5 years for all northern (>60°N) sites but decreased sharply from 30 to 10% in the third year in southern (<60°N) sites. Respiration rates of southern sites were less (40% on average) than those of northern sites. Humus layer N was positively correlated to needle weight loss during the first and the second years, but negatively correlated in the third year and to respiration rates. The results indicated that litter formed in southern Sweden became more recalcitrant in later stages of decomposition compared to litter produced in northern Sweden.     

中国水资源利用效率区域差异及影响因素研究

科学客观评价我国水资源利用效率的区域差异并探讨影响区域效率的因素是备受关注的问题.本文在全要素生产框架下利用基于投入导向的数据包络分析模型,以水资源、资本和劳动力为投入,以GDP为产出,采用省级数据计算我国1998-2008年水资源利用效率.结果显示,在研究时段内我国水资源利用效率总体上呈现出先下降后上升的趋势,并且从2008年开始水资源利用效率明显下降.在空间上,我国东、中、西部水资源利用效率处于三个明显不同级别,东部省份水资源利用效率最高,平均水平为0.8左右,其次是中部,平均水平为0.6左右,西部水资源利用效率最低,平均水平为0.4左右.进一步的回归分析发现,产业结构、进出口需求以及地区水资源禀赋对水资源利用效率均有显著影响.     

中国交通基础设施与经济增长的关系实证

交通基础设施通过乘数效应、旅行效应和外部效应促进经济增长,经济增长是交通基础设施需求增加和规划建设的重要前提.使用中国1952 -2006年相关统计数据,以GDP衡量经济增长,以公路铁路运营里程和货运量衡量交通基础设施,基于协整理论和Granger因果检验方法,分析得出交通基础设施与经济增长间存在长期均衡关系,前者是后者的Granger原因,反之不成立;引入Cobb - Douglas生产函数建立回归模型,采用主成分回归法修正最小二乘回归模型易受多重共线性影响的缺点,发现交通基础设施对经济增长具有显著的促进作用,且公路交通基础设施对经济增长的贡献率显著大于铁路交通基础设施;以1978年为时间断点,运用虚拟变量法,检验样本期内交通基础设施对经济增长影响是否发生结构性变化,发现1978年前后交通基础设施对经济增长的促进作用统计上相同.     

When Ecosystem Services Crash: Preparing for Big,Fast, Patchy Climate Change

Assessments of adaptation options generally focus on incremental, homogeneous ecosystem responses to climate even though climate change impacts can be big, fast, and patchy across a region. Regional drought-induced tree die-off in semiarid woodlands highlights how an ecosystem crash fundamentally alters most ecosystem services and poses management challenges. Building on previous research showing how choice of location is linked to adaptive capacity and vulnerability, we developed a framework showing how the options for retaining desired ecosystem services in the face of sudden crashes depend on how portable the service is and whether the stakeholder is flexible with regard to the location where they receive their services. Stakeholders using portable services, or stakeholders who can move to other locations to obtain services, may be more resilient to ecosystem crashes. Our framework suggests that entering into cooperative networks with regionally distributed stakeholders is key to building resilience to big, fast, patchy crashes.     

Assessment Tools for Urban Catchments: Developing Biological Indicators Based on Benthic Macroinvertebrates1

Abstract: Biological indicators, particularly benthic macroinvertebrates, are widely used and effective measures of the impact of urbanization on stream ecosystems. A multimetric biological index of urbanization was developed using a large benthic macroinvertebrate dataset (n = 1,835) from the Baltimore, Maryland, metropolitan area and then validated with datasets from Cleveland, Ohio (n = 79); San Jose, California (n = 85); and a different subset of the Baltimore data (n = 85). The biological metrics used to develop the multimetric index were selected using several criteria and were required to represent ecological attributes of macroinvertebrate assemblages including taxonomic composition and richness (number of taxa in the insect orders of Ephemeroptera, Plecoptera, and Trichoptera), functional feeding group (number of taxa designated as filterers), and habit (percent of individuals which cling to the substrate). Quantile regression was used to select metrics and characterize the relationship between the final biological index and an urban gradient (composed of population density, road density, and urban land use). Although more complex biological indices exist, this simplified multimetric index showed a consistent relationship between biological indicators and urban conditions (as measured by quantile regression) in three climatic regions of the United States and can serve as an assessment tool for environmental managers to prioritize urban stream sites for restoration and protection.     

次级河流回水区叶绿素a与影响因子的多元分析——以临江河为例

为了对次级河流回水区富营养化进行深入研究,把长江次级河流之一的临江河回水区为研究对象,根据2007年10月至2008年9月临江河回水区中游叶绿素a含量及其水质理化指标的监测数据,分析了临其叶绿素a浓度的时间分布,对叶绿素a浓度及影响因子进行相关分析,找出与叶绿素a显著相关的环境因子并建立多元逐步回归模型。结果表明：临江河回水区叶绿素a浓度峰值主要集中在5月上旬至9月下旬,变化范围为227～661 mg/m3。临江河回水区叶绿素a浓度变化受多个环境因子共同影响,与水温、流速、透明度、COD、总磷之间显著相关,而与总氮相关性不显著。经过叶绿素a及其影响因子的相关分析,建立了以水温、流速和总磷为自变量,叶绿素a浓度为应变量的逐步线性回归模型,模型初步验证结果表明：多元逐步回归模型可以用来描述临江河回水区叶绿素a浓度的变化。通过对临江河回水区叶绿素a及其影响因子的分析,控制临江河回水区水体中磷含量应是其富营养化防治工作的重点,防治工作应主要在春末和整个夏季,尤其是在5、6月份。     

用于早期火灾分类的非线性决策树支持向量机

对早期火灾信息进行研究,提出了一种基于非线性决策树的支持向量机多类分类模型。该模型利用非线性映射将样本投影到高维特征空间,比较每类样本在高维空间的分布情况,进行聚类构造出一个二叉决策树,使容易区分的类别从根节点逐层分类出来,有效克服了错分积累和避免不可分情况;同时,各个节点采用二值最小二乘小波支持向量机,以获得较高的泛化能力。该文将该模型用于早期火灾分类,并与BP神经网络、K近邻法和决策树方法进行比较,实验结果表明,该模型对早期火灾的识别率更高。     

基于事故树理论的非金属矿山爆破事故致因分析

采用安全系统工程方法,以陕西省某大理石矿为例,对非金属矿山爆破事故进行了事故树分析,并绘制出爆破事故树分析图,直观地表现了各可能导致顶上事件发生的基本事件及其逻辑关系,通过对FTA的定性分析,得出了最小割集和结构重要度,并提出了相应的安全对策.     

TiO_2光催化同时脱硫脱硝效率影响因素研究

基于多元线性回归,对TiO2光催化同时脱硫、脱硝效率进行了预测研究.在最佳实验条件下,预测了不同SO2和NOx浓度的光催化脱除效率.依据正交试验结果,确定了最佳运行工况,将温度、湿度、SO2和NOx浓度对同时脱硫、脱硝效果的影响程度划分为3个等级,在此基础上有针对性地提出了可行措施.