约束高强度Q460钢柱抗火性能分析

为了研究高强度约束钢柱在火灾下的反应,根据高强度结构钢Q460在高温下的力学性能参数,建立了约束高强度钢柱受火分析模型,得到了高强度约束钢柱在火灾下的轴向位移、跨中挠度、最大应力以及临界温度。采用有限元分析对理论结果进行了验证,两者吻合很好。利用验证过的该文计算方法计算了2种荷栽比、长细比和约束刚度比条件下的高强钢柱的抗火性能;采用CECS200:2006的力学性能参数计算了约束普通钢柱的抗火性能。通过对高强钢和普通钢的抗火性能分析发现,轴向约束明显降低钢柱的临界温度,长细比、荷载比越大,临界温度越低;高强钢的抗火性能要优于普通钢。     

2008年低温雨雪冰冻对武汉城市公共交通的影响评估

为了对2008年低温雨雪期间气象条件对城市交通运输的影响给出定量评估,运用天气分析及统计学方法,分析了低温雨雪冰冻期间武汉市主要气候特征,利用2008年初持续低温雨雪期间武汉城市公共交通线路（包括公交车、轮渡、汽渡）逐日停运数据,定义了持续低温雨雪冰冻过程城市公共交通影响度,通过统计分析,找到了关键气象因子、关键期和低温临界指标,建立了气象评估模型。结果表明：在持续低温雨雪冰冻过程中,初发时期是公共交通影响的关键时期之一,影响度与积雪深度关系最密切,在公交车、轮渡、汽渡3种交通工具中,公交车影响度与气象要素的相关最密切,对武汉城市公交车造成明显影响的临界气温是17℃。该结论在实际的气象灾害评估业务工作中进行了运用,效果良好     

三相电力有源滤波器（APF）控制策略的研究

介绍了有源电力滤波器控制策略,提出了PWM控制技术在电网电压畸变情况下对电网中滤波电流进行连续动态补偿。建立了PWM控制的逆变系统模型并进行仿真研究,结果验证了该控制策略能有效补偿谐波电流。     

Experimental thermal storage research of organic binary phase change materials in building environment

This paper aims to reveal the heat transfer mechanism of low-temperature phase change material (PCM) and design PCM heat storage device in building heating environment. Firstly, low-temperature binary PCMs of lauric acid and stearic acid are prepared, and their thermal properties are investigated by DSC. Then, shell and tube latent heat thermal energy storage units are conducted, and heat transfer experiments are carried out to analyze the heat transfer mechanism of PCM. The results demonstrate that natural convection plays an important role in heat transfer process, and the heat storage efficiency of PCMs can be significantly enhanced by increasing the fin width and improving the inlet heat transfer fluid (HTF) temperature. Furthermore, some proposals are put forward to guide the design of PCM storage device in building heating environment.     

China's Total Emission Control Policy:a Critical Review

As part of a comprehensive environmental management system, many countries establish emission control targets for mass emissions of a pollutant. Such targets are often the key objective of an environmental policy, such as an emission trading program. In China, however, it is more than just an objective of one particular policy; it has become a concept that has influenced many national environmental policies and activities. The objective of this article is to review the implementation of the total emission c...     

Urban land use,mobility and theory of science: exploring the potential for critical realism in empirical research

Academic discussion where the adequacy of positions within theory of science is illustrated by means of examples from empirical research studies seems to be an area of neglect. The purpose of this paper is to contribute to such a debate, using examples from investigations into the relationship between urban structure and travel behaviour. The main research question of these investigations was whether, and to what extent, urban structural conditions are influencing residents' transportation activity. In other words, is there a causal relationship between urban structure and travel behaviour? Furthermore, we asked whether results from studies of the relationship between land use and transport can provide a basis for predictions about the likely consequences of alternative land-use strategies. The methodology and empirical findings of the studies are discussed in the light of the theory of science position labelled ‘critical realism’, in an attempt to relate theory of science to empirical research, but also in order to contribute to the discussion of the usefulness of this specific approach. Copyright © 2002 John Wiley & Sons, Ltd.     

矿井通风仿真系统双线图的快速自动绘制研究

在深入研究通风网络巷道连接关系的基础上,创造性地提出一种新的效率更高的通风系统双线图的快速自动绘制方法,即"假双线法"。"假双线法"与固定宽度双线法有本质的不同,其本质是将单线巷道的线型用固定宽度双线线型表示,再对交叉点进行消隐处理,无需计算双线坐标来实现双线图的快速自动绘制。该法较好地解决了传统方法的缺陷,具有普遍性,其计算量小,执行效率高,并在双线图的基础上很容易拓展生成通风系统立体图。笔者研究成果,对于研发、改进矿井通风仿真图形系统和解决其他行业类似问题具有一定的参考价值。     

Modelling plant species richness using functional groups

Conservation biologists increasingly rely on spatial predictive models of biodiversity to support decision-making. Therefore, highly accurate and ecologically meaningful models are required at relatively broad spatial scales. While statistical techniques have been optimized to improve model accuracy, less focus has been given to the question: How does the autecology of a single species affect model quality? We compare a direct modelling approach versus a cumulative modelling approach for predicting plant species richness, where the latter gives more weight to the ecology of functional species groups. In the direct modelling approach, species richness is predicted by a single model calibrated for all species. In the cumulative modelling approach, the species were partitioned into functional groups, with each group calibrated separately and species richness of each group was cumulated to predict total species richness. We hypothesized that model accuracy depends on the ecology of individual species and that the cumulative modelling approach would predict species richness more accurately. The predictors explained plant species richness by ca. 25%. However, depending on the functional group the deviance explained varied from 3 to 67%. While both modelling approaches performed equally well, the models of the different functional groups highly varied in their quality and their spatial richness pattern. This variability helps to improve our understanding on how plant functional groups respond to ecological gradients.     

Testing hypotheses on shape and distribution of ecological response curves

Niche theory with hypotheses on shape and distribution of ecological response curves is used in the studies of resource sharing of competing plant species. Predictions based on theory should be applicable when, e.g., effects of competing species on the ecological tolerances are assessed or species’ diversity along a resource gradient is evaluated. We studied the ecological response curves of competing plant species along a resource gradient in boreal forests. The study was based on nation-wide soil and vegetation data collected from 455 sample plots on boreal forests in Finland. Species response curves along a soil fertility gradient (in terms of C/N ratio) were estimated using generalized additive models. Distribution of species optima and the relationship of niche width and skewness to the location of the optimum were analyzed with new bootstrap tests. The developed tests can account for the effects of truncation observed in the response curves of several species and for the uneven distribution of observations on the gradient.The estimated response curves of the major field layer species of boreal forests were not evenly distributed along soil C/N gradient. The density of optima peaked with relatively high nitrogen availability. Species with optima at low nitrogen availability had relatively broad realized niches. Niche width was negatively correlated with the density of optima. Species optima were packed and niches were narrow at high resource levels. This result suggests that a greater number of more specialized species can occur and interspecific competition decreases niche widths at high resource levels. Species were packed in the gradient where the C/N ratio was lower than 25, i.e., in conditions where nitrification can take place. This indicates that the majority of the vascular plants of boreal forests are favoured by the availability of NO₃⁻. Those few species thriving at high C/N ratios have broader realized niches.