A robust approach for iterative contaminant source location and release history recovery

Contamination source identification is a crucial step in environmental remediation. The exact contaminant source locations and release histories are often unknown due to lack of records and therefore must be identified through inversion. Coupled source location and release history identification is a complex nonlinear optimization problem. Existing strategies for contaminant source identification have important practical limitations. In many studies, analytical solutions for point sources are used; the problem is often formulated and solved via nonlinear optimization; and model uncertainty is seldom considered. In practice, model uncertainty can be significant because of the uncertainty in model structure and parameters, and the error in numerical solutions. An inaccurate model can lead to erroneous inversion of contaminant sources. In this work, a constrained robust least squares (CRLS) estimator is combined with a branch-and-bound global optimization solver for iteratively identifying source release histories and source locations. CRLS is used for source release history recovery and the global optimization solver is used for location search. CRLS is a robust estimator that was developed to incorporate directly a modeler's prior knowledge of model uncertainty and measurement error. The robustness of CRLS is essential for systems that are ill-conditioned. Because of this decoupling, the total solution time can be reduced significantly. Our numerical experiments show that the combination of CRLS with the global optimization solver achieved better performance than the combination of a non-robust estimator, i.e., the nonnegative least squares (NNLS) method, with the same solver.     

中国北方沙漠化地区生态重建的环境政策研究——基于Bioe-conomic Model

论文以内蒙古沙漠化地区为例,运用Bioe-conom ic M odel,比较自由放牧与耕垦、禁牧与禁垦、控制放牧规模与禁垦的土地利用政策情景下,引进舍饲养牛技术与信贷服务和增加非农就业机会对农户土地利用决策及其家庭收入的影响,据此探讨中国北方地区沙漠化发展的人文驱动机制以及生态重建的环境政策。结果表明:实施控制放牧规模与禁垦的环境政策,同时引进舍饲养牛技术能够有效地促进生态重建并提高农户收入;引进舍饲养牛技术需要启动基金,提供信贷服务和增加非农就业机会是贫困农户引进该技术的前提。因此,迫切需要调整宏观环境政策,提高农业集约化经营水平和城乡联系力度,从而提高农户家庭收入、减轻农民对环境的依赖性和促进农村的可持续发展。     

高层学生公寓防火体系构建

归纳总结学生高层公寓火灾伤亡事故致因因素,利用事故树分析法对其进行定性分析,得出最小径集,找出控制事故发生的途径,并利用“瑟利模型”建立防火体系,得到此类火灾事故防控措施,即一要通过培训和教育的手段,提高人感觉火灾危险的敏感性,使人处于安全状态并能够迅速、敏捷、正确地做出行为响应;二要保证物处于安全状态,确保电气设备、建筑物本质处于安全状态,并使建筑物能发挥性能化灭火作用,能在一定程度上控制火势,为疏散争取时间.本文能为高校高层学生公寓预防和控制火灾伤亡事故工作提供一定的借鉴作用.     

Assessing wetland changes in the venice lagoon by means of satellite remote sensing data

Not only does lagoon ecology represent a transitional zone between the sea and the continent but it also expresses the equilibrium belt between erosion and sedimentation processes. Within the framework of a coastal management scheme, a precise and timely mapping of morphological changes in this environment is important. This paper illustrates the possible contribution of multi-temporal satellite observations in the monitoring of the erosion/sedimentation processes of coastal zones, where landscape features are subjected to highly morphodynamical modifications. In particular, an improved mapping accuracy was obtained by the successive application of the Maximum Likelihood (MLH) classifier and the Linear Mixture Model (LMM) techniques to the satellite image classification procedure. In fact, by estimating the amount of shallow water and wetland within each satellite pixel, the LMM technique allows for an accurate mapping of the transitional zones in the lagoon environment, thus permitting an optimal separation between land and water. The study concerns the Venice lagoon (Italy) which has been sinking slowly since the beginning of this century. This has led to widespread loss of wetlands. In order to monitor the development of the land cover, four Landsat Thematic Mapper scenes were examined, during the period 1984 to 1993. The results obtained proved that the digital analysis method of multitemporal satellite imagery, applied over a selected test area, enables the evolution of an estuarine environment landscape, with its different sequences of erosion and periods of accretion, to be monitored. The significant influence of tidal stages is discussed in the data analysis.     

陕西省干旱灾害的农业风险评估

分析了陕西干旱发生的时空规律,以缺水率划分干旱标准,评价陕西各季农业干旱状况,并对1949～1990年共42a粮食产量序列进行滑动平均模拟,以粮食减产百分率评估全省干旱灾害等级,得出干旱损失评估模式,使陕西干旱灾害的评估由定性到定量,为其它灾害的定量评估提供了经验。     

事故致因“2-4”模型及其事故原因因素编码研究

事故致因模型是用于事故原因分析和预防的重要理论依据,模型的可操作性是决定事故预防效果的重要影响因素。对目前国内研究较为持续和系统的事故致因"2-4"模型进行了深入研究,以增强其在事故分析时的可操作性。首先,研究了事故致因"2-4"模型中组织内、外部原因的各个阶段原因因素的划分情况;其次,根据得到的各阶段原因因素划分结果,对应用事故致因"2-4"模型分析事故原因的因素进行了编码;最后,以一起重大瓦斯爆炸事故为例,对事故致因"2-4"模型原因因素编码系统的有效性进行了实证研究。划分了事故致因"2-4"模型中的各原因模块中的原因因素,并得到了不安全动作和物态、习惯性不安全行为、安全管理体系、安全文化、外部因素等5个层级原因,确定了基于事故致因"2-4"模型的30个原因因素。对事故原因因素进行系统编码,提高了应用事故致因"2-4"模型进行事故原因分析和事故预防的可操作性,增强了其应用实践性。     

HFACS与24 Model:不安全动作原因的对比研究

不安全动作的定义、分类与识别尚未有统一标准,这给事故分析与预防带来许多困难。基于此,对人因分析与分类系统(HFACS)和24 Model中的不安全动作层面进行对比研究。在不安全动作对应方面:HFACS中的不安全动作均能对应到24 Model中的不安全动作,但HFACS没有涉及24 Model中不违章、未引起事故但高风险的不安全动作,因而无法实现事前预防。在间接原因对应方面,HFACS中不安全动作的产生原因均可与24 Model中的1个或多个间接原因相对应;HFACS中不安全动作的产生涉及较多生理、心理层面的原因,而考虑到实用性原则,24 Model暂未给出该两方面原因的具体分类方法。在不安全动作发出者方面:24 Model涉及组织内各层级人员,而HFACS仅指一线员工。在实际应用方面:两种模型均可用于不安全动作原因的统计分析;24 Model给出的不安全动作分类范围较HFACS广,在事故分析时所受局限性小,但易造成不安全动作遗漏;在用24 Model进行不安全动作分析时,应尽量细化动作分类及分析的深入程度,以及动作发出者的员工层级。     

HFACS中不安全监管因素与事故致因24 Model中不安全动作因素的对比分析

为了使HFACS这种事故分析方法能够在我国各种类型事故中得到应用,研究了HFACS的不安全监管因素中各指标的定义和分类,并将其与事故致因24 Model中的不安全动作因素进行对比,得出两者的对应关系和各自特点。结果表明:HFACS中多数不安全监管因素属于24 Model中的不安全动作,这些不安全动作的发出者都是监管者;24 Model中不安全动作的发出者既可以是事故的直接引发者,也可以是监管者。从监管的范畴来看,HFACS中不安全监管因素的范围小于24 Model中的监管范围,只包括组织内部的监管。     

饮用水氯化消毒过程的动力学模型研究进展

饮用水氯化消毒的安全性问题一直是水处理领域的研究重点,其氯化消毒过程动力学过程模型的建立,对于饮用水含氯量监测、评价及生成消毒副产物的控制具有重要意义。本文概述了饮用水氯化消毒过程的有关动力学模型研究现状及进展,从模型依据的机理和表达形式等方面分析了饮用水氯化消毒过程的动力学模型研究进展,介绍了广泛应用的几种模型,如Clark自由氯衰减模型、Valentine氯胺衰减模型等,通过对相关模型的原理、异同点、优缺点、适用性的对比及对影响模型的因素分析,对氯化消毒过程中动力学模型的今后发展趋势作了展望。