计算流体力学技术在膜分离过程中的应用与进展

计算流体力学（ComputationalFluidDynamics，CFD）技术近年被广泛地应用于膜分离过程模拟中。本文评述了CFD研究膜分离过程中流体力学、膜污染机理和浓差极化等现象，以及CFD技术在微滤、超滤、反渗透中的研究进展及待解决问题等。     

A critical investigation of evaluation matrices to inform coastal adaptation and planning decisions at the local scale

Local governments are under pressure to tackle an increasing spectrum of complex contemporary problems, such as climate change, while ensuring multiple stakeholder interests are incorporated into decision processes. Multi-criteria decision tools can assist, but challenges remain in creating an enabling environment for incorporating and balancing different stakeholder perspectives. Here, we draw on interview data and a sensitivity analysis to investigate the use of an evaluation matrix to guide local coastal adaptation decision-making in South Africa. We adopt a participatory action research framework and find that decision-making is influenced by individual, departmental and institutional values that are not adequately captured in the matrix approach. Our study reveals the compromise between achieving broad stakeholder representation and utilising technical expertise, and that altering matrix assumptions can imply different decision outcomes. Suggestions are made to improve multi-criteria decision approaches to better facilitate integrated coastal management in responding to local coastal adaptation challenges.     

火灾中人员的行为及其模拟计算方法的研究

在综合分析国内外人员疏散模型和模拟软件发展现状的基础上,研究人员在火灾中的行为理论、计算机模型、模拟原理等,并介绍了目前国际上研究人员行为方面综合功能较强的Building EXODUS软件的原理和特点,最后以具体实例说明了Building EXODUS软件在人群疏散模拟分析中的具体应用.研究表明,1)在不考虑其他因素的影响下,疏散总时间与人数成正比;2)在火灾等紧急情况下,当某个出口不能通行时,可能会使大量人员在另一个出口处造成"瓶颈"现象,因此,增加备用安全出口很重要;3)疏散时间实际上是一随机变量,会因各种情况的变化而不同,如在很大程度上受人员特性(如年龄等因素)的影响,传统计算方法一般会低估疏散时间而不能作为建筑疏散设计的依据;4)利用计算机模拟软件可以对火灾中各种可能发生的情况进行评价,评价结果比传统方法更科学、可信.火灾中人员行为的研究需要从心理学和社会学角度建立人群中个人行为与社会行为的理论框架,而疏散模拟是一个由多个因素组成的复杂系统,大量人群环境的模拟需要涉及人与人、人与环境间的相互作用.     

Measuring Protected‐Area Isolation and Correlations of Isolation with Land‐Use Intensity and Protection Status

Abstract: Protected areas cover over 12% of the terrestrial surface of Earth, and yet many fail to protect species and ecological processes as originally envisioned. Results of recent studies suggest that a critical reason for this failure is an increasing contrast between the protected lands and the surrounding matrix of often highly altered land cover. We measured the isolation of 114 protected areas distributed worldwide by comparing vegetation‐cover heterogeneity inside protected areas with heterogeneity outside the protected areas. We quantified heterogeneity as the contagion of greenness on the basis of NDVI (normalized difference vegetation index) values, for which a higher value of contagion indicates less heterogeneous land cover. We then measured isolation as the difference between mean contagion inside the protected area and mean contagion in 3 buffer areas of increasing distance from the protected‐area border. The isolation of protected areas was significantly positive in 110 of the 114 areas, indicating that vegetation cover was consistently more heterogeneous 10–20 km outside protected areas than inside their borders. Unlike previous researchers, we found that protected areas in which low levels of human activity are allowed were more isolated than areas in which high levels are allowed. Our method is a novel way to assess the isolation of protected areas in different environmental contexts and regions.     

Intra‐individual variability in job complexity over time: Examining the effect of job complexity trajectory on employee job strain

Drawing on gestalt characteristics theory, we advance the literature on the effect of job complexity on employee well‐being by considering intra‐individual variability of job complexity over time. Specifically, we examine how the trend, or trajectory, of job complexity over time can explain unique variance of employee job strain. Across two longitudinal data sets, we consistently find that, with the average level of job complexity during a given period held constant, a positive job complexity trajectory (i.e., an increasing trend in complexity) is associated with higher employee job strain. Based on job‐demand‐control theory and the exposure‐reactivity model, we further establish that job autonomy and employee emotional stability jointly moderate the relationship between job complexity trajectory and employee job strain. Specifically, for employees with high emotional stability, job autonomy mitigates the job strain brought by positive job complexity trajectory, whereas for employees with low emotional stability, job autonomy does not help to reduce the adverse effect of the increasing trend. These findings not only contribute to extend the understanding of the job complexity – strain relationship, but also suggest a promising, dynamic avenue to study the effects of work characteristics on employee well‐being as well as other outcomes. Copyright © 2016 John Wiley & Sons, Ltd.     

An optimized airfoil geometry for vertical-axis wind turbine applications

ABSTRACT

In this work, a new airfoil shape optimized for vertical-axis wind turbine applications is proposed. Different airfoil shapes have been analyzed with JavaFoil, a panel method software. Then, the results from the analysis have been used to optimize the performance of the new airfoil shape. Afterward, Computational Fluid Dynamics (CFD) simulations of the proposed airfoil, UO-17-LDA, are run for different angles of attack to provide insight into the flow field and the mechanisms related to this increase in performance. The UO-17-LDA airfoil presents a high lift-to-drag ratio and a delayed stall angle with respect to the original FX-63-137 airfoil, making it suitable for vertical-axis wind turbine applications. This increase in performance has been verified by comparing two VAWT designs with the original and the proposed airfoil using a double-multiple streamtube model. Finally, the practicality of JavaFoil for the comparison of different airfoil geometries has been verified, as it is capable of obtaining results for a wide number of flow conditions in small computational times and with a user-friendly interface. Nevertheless, the results diverge from the actual solution for high angles of attack (beyond stall). Hence, the time and effort required to perform CFD simulations is justified to gain insight into the actual behavior of a particular airfoil, as well as to obtain a richer analysis of the flow field and the mechanisms related to the airfoil performance.     

建筑风载数值模拟的影响因素

通过对建筑物周围风场的计算流体动力学(CFD)模拟计算与原型试验结果的比较,分析了在应用CFD计算时应该考虑的计算区域、进口边界条件、湍流模型和网格划分等各种相关因素对CFD数值模拟结果准确度的影响.结果表明,在各种影响因素中,计算区域影响相对较小,而进口边界条件、网格划分和湍流模型的影响相对较大;而且进口边界条件中速度分布对计算结果的影响大于湍流强度分布对计算结果的影响,是进口边界条件中的关键部分.同时,根据上述比较,建议在网格划分中,对几何外形简单的单个建筑的数值模拟计算,优先采用结构化网格划分方法;对于湍流模型的选择,一般的工程应用中,建议在初步设计阶段选择RNGκ-ε湍流模型,而在最终设计阶段采用雷诺应力模型.     

Search and rescue in collapsed structures: engineering and social science aspects

This paper discusses the social science and engineering dimensions of search and rescue (SAR) in collapsed buildings. First, existing information is presented on factors that influence the behaviour of trapped victims, particularly human, physical, socioeconomic and circumstantial factors. Trapped victims are most often discussed in the context of structural collapse and injuries sustained. Most studies in this area focus on earthquakes as the type of disaster that produces the most extensive structural damage. Second, information is set out on the engineering aspects of urban search and rescue (USAR) in the United States, including the role of structural engineers in USAR operations, training and certification of structural specialists, and safety and general procedures. The use of computational simulation to link the engineering and social science aspects of USAR is discussed. This could supplement training of local SAR groups and USAR teams, allowing them to understand better the collapse process and how voids form in a rubble pile. A preliminary simulation tool developed for this purpose is described.     

邻避型PPP项目的运营模式与居民环境行为研究

运营模式的科学设计以及居民环境行为的有效管理是邻避型PPP项目能否成功的关键。针对邻避项目存在的低收益和居民环境行为转变难两大问题,本文基于计算实验理论与方法构建邻避型PPP项目的运营模式与居民环境行为模型。通过对利益相关主体的社会属性与行为变化规律分析,进而设计运营商、政府、居民和从业人员等主体的计算实验交互规则。模型与计算实验研究了邻避型PPP项目的运营状态和居民环境行为在自负盈亏与统一价格、最小收益保证与统一价格、固定收益率与统一价格、自负盈亏与阶梯价格、最小收益保证与阶梯价格、最小收益保证与阶梯价格以及固定收益率与阶梯价格等六种情景下的演变规律。研究发现:(1)阶梯价格能在短期内改善邻避型PPP项目的运营状况,统一价格机制更有利于项目长远发展。(2)自负盈亏并不是邻避型PPP项目的一个理想方案,收益担保是一个相对稳妥可行的选择,而固定收益率是一个对政府财政有高要求的优化模式,可优化居民环境行为并降低PPP项目的邻避效应。(3)自负盈亏模式下运营商无心开展环境教育和提高从业人员待遇,固定收益率模式有利于推行环境教育并提高从业人员待遇。(4)邻避型PPP项目的环境投入-环境意愿-环境行为之间存在时滞效应。这意味着,较难通过收益模式与价格机制的调整实现系统的最优化,市场的力量无法协调邻避型PPP项目目前存在的矛盾与冲突,需要政府统一管理价格并保证社会资本的回报。同时,改善居民环境行为和管理邻避项目是一个复杂系统工程,需要有系统的筹划与长期时间的积累。     

一种新的结构可靠度通用计算方法

根据可靠度指标β的几何定义,运用具有全局优化能力的改进遗传算法,提出一种新的结构可靠度通用计算方法。针对可靠度几何优化模型搜索区域大而可行区域小的特点,在可靠区域和失效区域分别产生初始种群,在两种群之间通过不断迭代的二分法,使二分点不断接近极限状态曲面(线),从而产生可行解。对可行解进行选择、交叉、变异,最后求出全局最优解。该方法不需要使用结构功能函数的偏导数,对于功能函数不能明确表达的可靠度问题尤为适用;对于功能函数可以明确表达但求导复杂的问题,可省去求导过程;可任意设定初始值,且不受结构功能函数凹凸性的限制;通过算例验证,所提方法具有较高的精度和效率。