OPTIMIZATION OF INTERMITTENT PUMPING SCHEDULES FOR AQUIFER REMEDIATION USING A GENETIC ALGORITHM1

ABSTRACT: Using a genetic algorithm (GA), optimal intermittent pumping schedules were established to simulate pump‐and‐treat remediation of a contaminated aquifer with known hydraulic limitations and a water miscible contaminant, located within the Duke Forest in Durham, North Carolina. The objectives of the optimization model were to minimize total costs, minimize health risks, and maximize the amount of contaminant removed from the aquifer. Stochastic ground water and contaminant transport models were required to provide estimates of contaminant concentrations at pumping wells. Optimization model simulations defined a tradeoff curve between the pumping cost and the amount of contaminant extracted from the aquifer. For this specific aquifer/miscible contaminant combination, the model simulations indicated that pump‐and‐treat remediation using intermittent pumping schedules for each pumping well produced significant reductions in predicted contaminant concentrations and associated health risks at a reasonable cost, after a remediation time of two years.     

基于随机有限元可靠度的RC结构抗火设计参数优化方法

本文较详细地分析了各设计参数对RC结构抗火能力的影响。在已知结构抗火功能函数的基础上利用随机有限元可靠度的计算方法分析各参数对结构抗火能力的敏感性,根据各参数敏感性的不同,在设计时有意识地对该参数作一些较小的变动,结构的可靠度会明显的增加从而提高了结构的抗火能力。为RC结构抗火设计提供了一种参数优化的方法。     

A Question of Boundaries: The Importance of “Revenuesheds” for Watershed Protection1

Patterson, Lauren A., Jeffrey Hughes, Glenn Barnes, and Stacey I. Berahzer, 2012. A Question of Boundaries: The Importance of “Revenuesheds” for Watershed Protection. Journal of the American Water Resources Association (JAWRA) 48(4): 838‐848. DOI: 10.1111/j.1752‐1688.2012.00655.x Abstract: Watersheds transcend jurisdictional boundaries; raising important questions of who should pay for watershed protection, and how can watershed governance be funded? The responsibility and cost for watershed protection has progressively devolved to local governments, resulting in additional negative externalities and financing challenges. Watershed governance structures have formed at the scale of the watershed, but they often lack the financing mechanisms needed to achieve policy goals. Financing mechanisms via local governments provide a reliable source of revenue and the flexibility to address watershed specific issues. We develop a “revenueshed” approach to access the initial challenges local governments face when seeking to finance trans‐jurisdictional watershed governance. The revenueshed approach engages local governments into discussion and implementation of financial strategies for collaborative watershed governance. Legislation places water quality regulations primarily on local governments inside the watershed. The revenueshed approach extends the financial and stewardship discussion to include local governments outside the watershed that benefit from the watershed. We applied the revenueshed approach to the Mills River and Upper Neuse watersheds in North Carolina. Mills River had a partnership governance seeking revenue for specific projects, whereas the Upper Neuse sought long‐term financial stability to meet new water quality legislation.     

基于Monte-Carlo方法的静电除尘器除尘效率

针对经典除尘效率未考虑诸多随机因素影响的问题,提出了基于Monte-Carlo方法的效率分析模型,并通过实验数据验证其可靠性。通过该模型分析了粒径大小、电场气流速度、电晕电压、两极间距、粒子浓度等因素对收尘效率的影响规律,结果表明:基于Monte-Carlo方法的仿真结果精度更高,能有效预测静电除尘器的收尘效率,对于改进静电除尘器设计具有一定的理论意义和实用价值。     

Robustness of Meteorological Droughts in Dynamically Downscaled Climate Simulations

We examine the robustness of a suite of regional climate models (RCMs) in simulating meteorological droughts and associated metrics in present‐day climate (1971‐2003) over the conterminous United States (U.S.). The RCMs that are part of North American Regional Climate Change Assessment Program (NARCCAP) simulations are compared with multiple observations over the climatologically homogeneous regions of the U.S. The seasonal precipitation, climatology, drought attributes, and trends have been assessed. The reanalysis‐based multi‐model median RCM reasonably simulates observed statistical attributes of drought and the regional detail due to topographic forcing. However, models fail to simulate significant drying trend over the Southwest and West. Further, reanalysis‐based NARCCAP runs underestimate the observed drought frequency overall, with the exception of the Southwest; whereas they underestimate persistence in the drought‐affected areas over the Southwest and West‐North Central regions. However, global climate model‐driven NARCCAP ensembles tend to overestimate regional drought frequencies. Models exhibit considerable uncertainties while reproducing meteorological drought statistics, as evidenced by a general lack of agreement in the Hurst exponent, which in turn controls drought persistence. Water resources managers need to be aware of the limitations of current climate models, while regional climate modelers may want to fine‐tune their parameters to address impact‐relevant metrics.     

中国经济发展方式的转变动力及其作用途径

以全要素生产率增长动力作为经济发展方式的转变动力,本文采用1989-2013年4组省际面板数据经由可行广义最小二乘法实证估计了10个动力因素对全要素生产率增长率的贡献水平与作用途径。研究发现:技术创新水平、市场化水平、人力资本存量水平、异质性企业集聚水平和对外开放度的综合指数对中国全要素生产率增长率的回归估计系数分别为0.575 7,0.212 5,0.136 8,0.064 4和0.018,表明技术创新、市场化改革、人力资本积累、异质性企业集聚和对外开放是促进中国经济发展方式转变的直接动力因素。进一步的研究结果显示:技术创新和异质性企业集聚通过提高前沿技术进步率和生产效率变化率以及规模报酬收益率途径,市场化改革通过提高前沿技术进步率途径,人力资本积累与对外开放通过提高前沿技术进步率和规模报酬收益率途径,促进了中国全要素生产率增长。虽然产业结构变迁、城市化、基础设施建设、区域经济政策实施和金融发展对中国全要素生产率的增长表现为负向或拖累作用,但是,产业结构变迁与城市化能够提高前沿技术进步率,基础设施建设和区域经济政策能够提高规模报酬收益率,金融发展能够提高生产效率增长率和规模报酬收益率,这5项动力因素对促进中国全要素生产率增长的正向贡献有待提高。依据上述研究结论,本文提出尽快攻克制约生产率增长的核心技术,统筹考虑产业结构升级、城市化、基础设施建设和区域经济政策实施以及加快金融领域改革等政策建议,以期加快我国经济发展方式转变进程。     

基于Petri网的铁路车站安全防护系统建模及可靠性分析

采用单一的随机Petri网对车站线路结构、列车运行过程及车站防护系统建模,基于欧洲电工标准委员会定义的安全目标,确定车站安全防护系统的可靠性需求。对无防护系统的列车入站进行建模和分析,然后基于防护系统功能及可靠性特性,结合列车入站动态特性,对防护系统的功能和可靠性进行建模,并根据安全目标与车站事故率之间的数学关系进行系统的安全分析和可用性分析。其结果表明,车站防护系统的可靠性与乘客的个人风险存在着定量的关系,从而可以依据个人风险的标准来确定防护系统可靠性需求。     

Downward Migration of Dense Bottom Currents

The focus of this paper is on the dynamics of a dense current flowing along the continental slope, and the frictionally induced downward motion it experiences. In particular, the movement of the lateral boundaries where the isopycnals meet the bottom are considered. The current is taken to be wide compared to the Rossby radius, which is in accordance with observations and makes the dynamics quasigeostrophic. The time development of the plume thickness is studied, using three different parameterisations for the bottom friction.Independently of the choice of parameterisation, the following results are obtained: In the central part of the plume friction acts as a diffusive process to minimise the curvature of the upper surface of the plume. At the upper edge the plume quickly approaches a state with small slope, i.e. small geostrophic velocity and small frictionally induced downward flow. At the lower edge a tongue of dense water shoots out creating a widening layer. The thickness of the migrating layer is approximately equal to the boundary layer depth and its downward speed is comparable to the along-slope geostrophic velocity. The downslope end of the migrating layer may form a steep front which requires some precautions in the numerical procedure.     

前沿技术进步、技术效率和区域经济差距

采用1998-2009年中国30个省市的人均GDP与当年全国人均GDP的差值作为区域经济差距指标,运用核密度估计方法观察了我国区域经济差距的变动状况。从核密度图可知,我国区域经济呈现出收敛的态势;通过随机前沿模型从全要素生产率中分解出前沿技术进步和技术效率,利用1998-2009年28个省市的面板数据,检验了全要素生产率对区域经济差距的影响。实证结果显示,前沿技术进步能够显著的缩小区域经济差距,其中对于东部地区的效果较为显著,技术效率则能够扩大东部地区的经济差距,对于中部和西部地区的影响不显著。政策含义是缩小东部地区经济差距的主要途径是加大对科技创新领域的投入,加强对欠发达地区的技术支持;对于中部地区和西部地区而言,则应该是加大市场化水平、对外开放水平和地方支出比重。     

一个水质风险率计算的随机模型

将水质当作随机变量，基于随机点过程理论，构造了水质超阈值风险分析的成丛随机点过程复合（ＣＳＰＰＣ）模型，并应用于深圳市深圳河河口段水体ＤＯ、ＣＯＤ浓度超阈值的风险率估算，由实际资料对河段水体ＤＯ、ＣＯＤ浓度超阈值点过程的分布进行了拟合优度试验，获得满意计算结果。