TREND ASSESSMENT OF WATER QUALITY TIME SERIES1

ABSTRACT A general methodology is described for identifying and statistically modeling trends which may be contained in a water quality time series. A range of useful exploratory data analysis tools are suggested for discovering important patterns and statistical characteristics of the data such as trends caused by external interventions. To estimate the entries in an evenly spaced time series when data are available at irregular time intervals, a new procedure based upon seasonal adjustment is described. Intervention analysis is employed at the confirmatory data analysis stage to rigorously model changes in the mean levels of a series which are identified using exploratory data analysis techniques. Furthermore, intervention analysis can be utilized for estimating missing observations when they are not too numerous. The effects of cutting down a forest upon various water quality variables and also the consequences of acid rain upon the alkalinity in a stream provide illustrative applications which demonstrate the effectiveness of the methodology.     

渗透文化意识提高阅读能力

影响阅读的变量主要有作者变量、语篇变量和读者变量。其中，作者变量是我们无法改变的，文化知识是读者变量中的一个重要方面。在英语教学中，培养学生对异国文化和本国文化的异同的敏感度和自觉性，即培养学生的文化意识，可以通过分析有文化内涵的词语、跨越阅读中的文化障碍、接受文学作品的熏陶等途径来实现。     

Hydrologic Model Framework for Water Resources Planning in the Santa Cruz River,Southern Arizona1

Abstract: The authors develop a model framework that includes a set of hydrologic modules as a water resources management and planning tool for the upper Santa Cruz River near the Mexican border, Southern Arizona. The modules consist of: (1) stochastic generation of hourly precipitation scenarios that maintain the characteristics and variability of a 45‐year hourly precipitation record from a nearby rain gauge; (2) conceptual transformation of generated precipitation into daily streamflow using varied infiltration rates and estimates of the basin antecedent moisture conditions; and (3) surface‐water to ground‐water interaction for four downstream microbasins that accounts for alluvial ground‐water recharge, and ET and pumping losses. To maintain the large inter‐annual variability of streamflow as prevails in Southern Arizona, the model framework is constructed to produce three types of seasonal winter and summer categories of streamflow (i.e., wet, medium, or dry). Long‐term (i.e., 100 years) realizations (ensembles) are generated by the above described model framework that reflects two different regimes of inter annual variability. The first regime is that of the historic streamflow gauge record. The second regime is that of the tree ring reconstructed precipitation, which was derived for the study location. Generated flow ensembles for these two regimes are used to evaluate the risk that the regional four ground‐water microbasins decline below a preset storage threshold under different operational water utilization scenarios.     

Estimating the Relative Efficiency of Brazilian Publicly and Privately Owned Water Utilities: A Stochastic Cost Frontier Approach1

Abstract: This paper assesses cost efficiencies of Brazilian public and private companies of water supply. To measure the efficiency, we used a stochastic frontier model derived from the translog family – a specification similar to a Cobb‐Douglas including a quadratic term in log output. The model parameters are estimated by maximum likelihood using Brazilian data for the year 2002. Statistical inference leads to the conclusion that there is no evidence that private firms and public firms are significantly different in terms of efficiency measurements.     

大水矿山DGME系统动态随机模型及风险预测

大水矿山由于含水层通常难以疏干,矿山生产常采取边疏干含水层边开采的带压开采方式进行,此类矿山实际开采环境是由排水系统及地下水系统组成,即排水-地下水的开采环境(DrainingGroundwater Mining Environment,DGME)系统。为此,根据系统论的原理,构建了大水矿山排水-地下水开采环境系统动态随机模型,并以模型为基础分析了系统水位随机变化的影响因素。结果表明:1)DGME系统动态随机模型可反映出矿山地下水系统与排水系统之间的相互关系;2)矿山地下水位变化是Wiener过程,臼水位分布符合正态分布,其数字特征取决于系统输入输出流量差的均值及方差;3)系统当前风险状态受短期内系统水位变化影响,超出一定时域,系统风险状态不可预知。     

Evaluating the Impacts of Environmental Flow Alternatives on Reservoir and Recreational Operations Using System Dynamics Modeling

Providing environmental flows is increasingly a management obligation in many water resource systems. Evaluating the impacts of environmental flow alternatives on other water uses in a basin can be a challenge, especially when collaborating with stakeholders. We demonstrate the use of system dynamics (SD) modeling to assess the impacts of four environmental flow alternatives in the Rio Chama, New Mexico. The model was developed to examine impacts of each alternative on reservoir storage and releases, hydropower production and revenue, and whitewater boating access. We simulated each alternative within a stochastic framework in order to explicitly incorporate hydrologic uncertainty into the analyses. The environmental flow alternatives were developed at a collaborative workshop of geomorphology, hydrology, and ecology experts. Results from the model indicate that the proposed flow recommendations on the Rio Chama will generally decrease annual reservoir storage, increase median flows, and have minimal impacts on hydropower production and whitewater rafting on the system. The Rio Chama case study is a promising example of how SD modeling can be used in the early stages of environmental flow studies and why it is compatible with collaborative modeling.     

均质土坝非平稳随机地震反应分析

考虑地震荷载的随机性及强度、频率的非平稳性,基于作者提出的适用于非平稳随机过程的一般随机地震动模型,采用虚拟激励法,建立了非平稳随机地震反应分析方法,并将其应用于某实际均质土坝动力分析中。土石坝及坝基体系采用整体有限元离散,坝体和坝基材料的动力非线性性能以等效线性化方法考虑。首先,基于目标加速度时程的强度和能量信息,确定了作为输入的加速度时—频演变功率谱密度;其次,比较了确定性时程动力分析和非平稳随机分析的结果,探讨了频率非平稳随机地震激励下的土石坝地震反应特性;最后,比较了2种不同坝基条件下的土石坝非平稳随机地震反应,探讨了频率非平稳随机激励下的土石—坝基动力相互作用。分析结果表明:地震动的频率非平稳性对土石坝动力反应有一定影响;坝体—坝基动力相互作用在地震过程中的不同阶段表现有所不同,主震阶段的相互作用显著。     

基于贝叶斯随机评价方法的小城镇灾害易损性分析

为了准确评价小城镇灾害易损性所处的状态,进而为制定小城镇防灾减灾规划提供科学依据,提出了基于贝叶斯公式的小城镇灾害易损性随机评价方法。该方法通过计算小城镇灾害易损性单个指标属于某个评价级别的概率,由最大似然分类原则确定单个易损性指标的评价级别,进而采用最大加权概率原则推求其综合评价级别。通过实例计算分析,并与模糊评估方法、可拓物元评价方法进行比较验证,说明了该方法的可行性及其简单、实用的特点。     

高速公路交通应急救援资源的配置

针对交通事故与救援资源存在随机性的特点,建立了交通救援资源配置的随机模型。根据高速公路特有的道路条件与交通机理,确定了模型中救援服务水平、事故概率的权重,配置点至事故点的权值以及随机资源等参数值。将所建立的模型与参数用于河南省高速公路的救援资源配置,研究表明,新的配置方案较好满足了交通事故高概率区域的救援需求,并且合理减少了救援需求区域的资源配置数量,为目前高速公路交通应急资源的科学配置提供了重要的参考依据。     

A performance indicator for ranked set sampling using ranking error probability matrix

Ranked set sampling (RSS) is a sampling procedure that has been shown to provide more efficient procedures than simple random sampling, in particular the Mann-Whitney-Wilcoxon (MWW) statistic and the empirical distribution function (EDF). We briefly review the work of Bohn (1992) and Stokes and Sager (1988) on the effect of imperfect ranking on the RSS-based MWW test and on the RSS-based EDF, respectively. We propose a model for a ranking error probability matrix which we hope will become a useful tool for evaluating RSS-based statistical procedures