火力发电厂安全现状评价模式探讨

以火电厂现状评价为例,探索火力发电厂安全现状评价模式。     

Rethinking receiver operating characteristic analysis applications in ecological niche modeling

The area under the curve (AUC) of the receiver operating characteristic (ROC) has become a dominant tool in evaluating the accuracy of models predicting distributions of species. ROC has the advantage of being threshold-independent, and as such does not require decisions regarding thresholds of what constitutes a prediction of presence versus a prediction of absence. However, we show that, comparing two ROCs, using the AUC systematically undervalues models that do not provide predictions across the entire spectrum of proportional areas in the study area. Current ROC approaches in ecological niche modeling applications are also inappropriate because the two error components are weighted equally. We recommend a modification of ROC that remedies these problems, using partial-area ROC approaches to provide a firmer foundation for evaluation of predictions from ecological niche models. A worked example demonstrates that models that are evaluated favorably by traditional ROC AUCs are not necessarily the best when niche modeling considerations are incorporated into the design of the test.     

基于BP神经网络的苯储罐泄漏事故风险评价模型研究

为了在事故发生之前对苯储罐进行风险评价，提出1种基于BP神经网络的泄漏事故风险评价方法，利用该方法构建了苯储罐的风险评价模型，并对模型进行了训练及验证。研究结果表明:BP神经网络成功完成了建模任务，且模型训练结果较好，可利用基于BP神经网络所构建的苯泄漏事故风险评价模型对苯储罐发生泄漏事故的风险进行评价。     

Applying integrated assessment methodologies to air quality plans: Two European cases

Air pollution Integrated Assessment Models (IAM) can be used for determining how emissions should be reduced to improve air quality and to protect human health in a cost-efficient way. The application of IAM is also useful to spread information to the general public and to explain the effectiveness of proposed Air Quality Plans. In this paper, the application of the RIAT+ system to determine suitable abatement measures to improve the air quality at a regional/local level is presented for two European cases: the Brussels Capital Region (Belgium) and the Porto Urban Area (Portugal). Both regions are affected with PM10 or NO₂ concentrations that exceed the limit values specified by the European Union legislation. To properly assess air quality abatement measures a surrogate model was used, allowing the implementation of an efficient optimization procedure. This model is derived in both cases through a set of simulations performed using a Chemistry Transport Model fed with different emission reduction scenarios. In addition, internal costs (due to the implementation of emission reduction measures) and external costs (due to population exposure to air pollutant concentrations) of policy options were considered. The application of this integrated assessment modelling system in scenario (Brussels case) and optimization (Porto) modes contributes to identifying some advantages and limitations of these two approaches and also provides some guidance when urban air quality has to be assessed.     

Semi-analytical solution of two-dimensional sharp interface LNAPL transport models

In this paper, we present semi-analytical solutions for two-dimensional equations governing transport of Light Non-Aqueous Phase Liquids (LNAPL) in unconfined aquifers. The proposed model is based on sharp interface displacement and steady groundwater flow assumptions, where both the water–LNAPL interface and the LNAPL–air interface are represented as sharp interfaces. In the case of steady groundwater flow, these equations can be reduced to a two-dimensional nonlinear solute transport equation, with the LNAPL thickness in the free product lens being the primary unknown variable. The linearized form of this solute transport equation falls into the category of two-dimensional transport equation with time-dependent dispersion coefficients. This equation can be solved analytically for an infinite domain region. In this paper, the general form of the analytical solution for the transport equation, as well as the solutions for some specific cases are presented. To demonstrate the utility of the proposed solution, numerical results obtained for two example problems are discussed and presented comparatively with a finite-element solution and other more restrictive solutions available in the literature. Although the solutions discussed in this paper have some simplifying assumptions, such as sharp-interfaces between fluid phases, steady groundwater flow and homogeneous aquifer properties, the semi-analytical solutions presented in this study may be used effectively as bench mark solutions in evaluating LNAPL migration in the subsurface. These solutions are simple and cost effective to implement and may be used in the calibration of other more complex numerical solutions that can be found in the literature.     

A multiple criteria evaluation of sustainable agricultural development models using AHP

Selection of the appropriate agricultural development model has become an important issue in Iran. Using data from Fars province of Iran, the purpose of this paper is to use analytic hierarchy process (AHP) for selecting between the two competing sustainable agricultural development models, which have been developed based on the general tenets of Ecological Modernization (EM) and De-Modernization (DM) theories. Farmers, environmentalists, board members of rural cooperative, rural women and experts from Fars Agricultural (Jehad-e-Keshavarzi) Organization participated in application of AHP to this study. They applied AHP to determine the priority of DM and EM based sustainable agricultural development models. Each group determined the priority of the two models for sustainable agricultural development. The findings indicated that ecological criteria i.e. wise use of resources, environmental protection and product quality are the most important criteria for sustainable agriculture of Iran, followed by economic criterion employment and social criterion participation. A sensitivity analysis was carried out to determine the critical factors that affected the priority of alternatives. The results indicated that EM-based sustainable agricultural development model has a higher priority as the theoretical base of agricultural development of Iran. Readers should send their comments on this paper to BhaskarNath@aol.com within 3 months of publication of this issue     

森林资源经济利用的政策模拟模型应用研究

林业政策在对森林资源的培育、保护和利用方面起相当大的作用.在市场机制作用的框架下林业政策的作用更多的是通过影响市场机制传递的产品和生产要素的价格信号,进而影响生产经营主体的收益成本预期及其决策行为,最终影响到对森林资源的培育、保护和利用的效果,因此分析和认清林业政策对林业发展的作用机制和影响效果有重要的意义.本文基于市场机制.以林业经济福利为目标,把森林资源培育的第一产业环节和以森林资源为原料的第二产业发展结合一起作为完整的产业链,构建一个林业的政策模拟模型.利用该模型,对木材价格、林业税费、信贷利率和采伐限额等林业经济政策的影响进行了定量分析,着重比较了林业产权制度改革前后政策变化所产生的效应,以及所具有的激励效果,从而认识林业政策的变动和调整如何影响政策目标,为政策的制定和对合理政策进行选择提供参考的依据.