Floods and Climate Change: Interactions and Impacts

Whether the floods experienced during the last decade in Germany and in other European countries are triggered or worsened by human activities has been the subject of a great deal of debate. Possible anthropogenic activities leading to increased flood risk include river regulation measures, intensified land use and forestry, and emissions of greenhouse gases causing a change in the global climate. This article discusses the latter by reviewing the existing knowledge on the subject. First, the relevance, capabilities, and limitations of climate models for the simulation and analysis of flood risk under aspects of the anthropogenic climate change are described. Special consideration is given here to differences between the "typical" spatial scale of climate models and hydrological flood models. Second, observations of trends in climate variables relevant for river flooding issues are summarized. Special emphasis is put on the Rhine and other German catchment areas. Third, the possibilities of modeling the different parts of the "cascade of flood risk" are summarized, introducing the special features of meteorological, hydrological, and river hydraulic models.     

利用智能主体分析"时尚"的涌现

时尚作为一种社会现象,是由个别人物的倡导和示范,先在少数人中流行,然后迅速蔓延到社会.多数人出于新奇与从众心理而仿效.对于它的研究有助于人们把握这种社会现象的产生与蔓延过程,深入认识和控制它的发展.由于它的复杂多样性,当前还缺乏对它的定量分析与研究.论文利用基于智能主体的仿真方法,分析了时尚的涌现过程.文中建立了两种模型,用于确定公众能否接受某种时尚的临界值.一种模型基于公众能获取全部信息,另一种则基于个人只能获取邻近信息.     

Use of Markov Chain Monte Carlo Analysis with a Physiologically-Based Pharmacokinetic Model of Methylmercury to Estimate Exposures in U.S. Women of Childbearing Age

A Bayesian approach, implemented using Markov Chain Monte Carlo (MCMC) analysis, was applied with a physiologically‐based pharmacokinetic (PBPK) model of methylmercury (MeHg) to evaluate the variability of MeHg exposure in women of childbearing age in the U.S. population. The analysis made use of the newly available National Health and Nutrition Survey (NHANES) blood and hair mercury concentration data for women of age 16–49 years (sample size, 1,582). Bayesian analysis was performed to estimate the population variability in MeHg exposure (daily ingestion rate) implied by the variation in blood and hair concentrations of mercury in the NHANES database. The measured variability in the NHANES blood and hair data represents the result of a process that includes interindividual variation in exposure to MeHg and interindividual variation in the pharmacokinetics (distribution, clearance) of MeHg. The PBPK model includes a number of pharmacokinetic parameters (e.g., tissue volumes, partition coefficients, rate constants for metabolism and elimination) that can vary from individual to individual within the subpopulation of interest. Using MCMC analysis, it was possible to combine prior distributions of the PBPK model parameters with the NHANES blood and hair data, as well as with kinetic data from controlled human exposures to MeHg, to derive posterior distributions that refine the estimates of both the population exposure distribution and the pharmacokinetic parameters. In general, based on the populations surveyed by NHANES, the results of the MCMC analysis indicate that a small fraction, less than 1%, of the U.S. population of women of childbearing age may have mercury exposures greater than the EPA RfD for MeHg of 0.1 μg/kgg/day, and that there are few, if any, exposures greater than the ATSDR MRL of 0.3 μgg/kgg/day. The analysis also indicates that typical exposures may be greater than previously estimated from food consumption surveys, but that the variability in exposure within the population of U.S. women of childbearing age may be less than previously assumed.     

Development of a Screening Approach to Interpret Human Biomonitoring Data on Volatile Organic Compounds: Reverse Dosimetry on Biomonitoring Data for Trichloroethylene

A screening approach is developed for volatile organic compounds (VOCs) to estimate exposures that correspond to levels measured in fluids and/or tissues in human biomonitoring studies. The approach makes use of a generic physiologically-based pharmacokinetic (PBPK) model coupled with exposure pattern characterization, Monte Carlo analysis, and quantitative structure property relationships (QSPRs). QSPRs are used for VOCs with minimal data to develop chemical-specific parameters needed for the PBPK model. The PBPK model is capable of simulating VOC kinetics following multiple routes of exposure, such as oral exposure via water ingestion and inhalation exposure during shower events. Using published human biomonitoring data of trichloroethylene (TCE), the generic model is evaluated to determine how well it estimates TCE concentrations in blood based on the known drinking water concentrations. In addition, Monte Carlo analysis is conducted to characterize the impact of the following factors: (1) uncertainties in the QSPR-estimated chemical-specific parameters; (2) variability in physiological parameters; and (3) variability in exposure patterns. The results indicate that uncertainty in chemical-specific parameters makes only a minor contribution to the overall variability and uncertainty in the predicted TCE concentrations in blood. The model is used in a reverse dosimetry approach to derive estimates of TCE concentrations in drinking water based on given measurements of TCE in blood, for comparison to the U.S. EPA's Maximum Contaminant Level in drinking water. This example demonstrates how a reverse dosimetry approach can be used to facilitate interpretation of human biomonitoring data in a health risk context by deriving external exposures that are consistent with a biomonitoring data set, thereby permitting comparison with health-based exposure guidelines.     

信贷环境与类型差异情景下的PPP项目政府经济承诺决策

为破解政府在PPP项目中存在的"承诺不足"与"承诺过度"决策难题，基于项目类型和信贷环境差异构建四种决策情景，融合优化决策与实物期权理论构建政府经济承诺决策模型，通过Kuhn-Tucker条件分析模型解的条件与边界并设计计算机求解算法，以W市城东污水处理项目为例进行数值模拟探讨政府经济承诺决策规律。结果表明：情景差异将会影响政府经济承诺决策；政府经济承诺可以提升项目价值，但较高的经济承诺未必导致较高的承诺成本；政府应对收益波动型项目给予更低的经济承诺，应在信贷收紧时给予更高的经济承诺，反之亦然；政府可以通过转移收益分配权和增加投资额来降低经济承诺，且不同情景效果具有差异。本文系统刻画了信贷环境与类型差异对经济承诺决策的影响，对于明晰经济承诺的决策成本及其后果、控制PPP项目金融风险、优化我国政府经济承诺决策等具有积极价值。     

辽中北洼锦州A 区东营组浊积扇地震描述研究

针对渤海油田辽中北洼锦州A 区东二下段不同类型浊积扇内部反射结构及其地震响应特征认识难度大的问 题，开展了浊积扇地震描述研究。从浊积扇形成机理出发，根据围区钻遇浊积扇体不同部位探井的相应井段的岩性及 组合结构等典型特征，对不同浊积扇沉积亚相的沉积特征、岩性结构、测井和地震响应特征进行了系统的分析和描述。 在此基础上，建立不同类型浊积扇模型进行地震正演模拟，并对其地震响应特征进行了深入研究，最后利用地震多属 性预测技术对浊积扇的内幕进行了精细地刻画。预测了辽中北洼锦州A 区东营组浊积扇有利储层发育部位，研究结 果对该区浊积扇岩性油气藏勘探具有指导意义。     

试论在高师院校《实变函数》教学中引入现代数学思想的必要性及可能的途径

阐述了在高师院校实变函数教学中引入现代数学思想的必要性 ;指出目前在实变函数教学中较系统和全面地介绍分形的数学思想和应用是一个非常好的课题 ,并给出了具体的理由和可供操作的可能途径     

Assessing program impact using latent growth modeling: a primer for the evaluator

Latent growth modeling (LGM) has emerged as a flexible analytic technique for modeling change over time because it can describe developmental processes at both the inter- and intra-individual levels. The LGM method can also provide a means for testing the contribution of other variables in order to explain variability in growth trajectories. This paper didactically illustrates the use of LGM as an analytical tool in program evaluation. Specifically, a hypothetical evaluation of a high school drug prevention program was used to demonstrate: (a) how LGM can be used to assess the longitudinal impact of a prevention program by comparing treatment and control populations with respect to individual differences in initial status and in rate of change; and (b) how predictors of initial status (post-intervention) and growth selected on the basis of a particular program theory can be incorporated in the model to explain program impact. Some advantages and limitations of using LGM in program evaluation are highlighted.     

数学的文化观念与数学教育改革

论述了数学在人类文化中的地位和作用，强调了数学的文化观念对于数学教育改革的重要意义，并就若干问题提出了作者本人的见解．     

An individual-based model for competingDrosophila populations

An individual-based model forDrosophila is formulated, based on competition amongst larvae consuming the same batch of food. The predictions of the model are supported by data for single speciesDrosophila populations reared in the laboratory. The model is used to build a simple discrete model for the dynamics ofDrosophila populations that are kept over a number of generations. The dynamics of a single species is shown to give either a stable equilibrium or fluctuations which can be periodic or chaotic. When the dynamics of a species in the absence of the other is periodic or chaotic, we found coexistence or two alternative states, on neither of which the species can coexist.