多层频率选择表面复合吸波结构的研究

文中采用一种快速求解方法——半解析半数值法计算多层频率选择表面(Frequency Selective Surface,简称FSS)复合结构的反射系数,然后结合具体两层复合结构的实例通过测试验证了半解析半数值法的正确性,并基于复合结构吸波材料吸波频带窄的缺点,在此基础上,设计出一种新的圆形FSS复合结构吸波材料。计算和测试结果都表明,这种新的复合结构在较宽带宽内具有低反射系数。     

攀枝花市城市基础设施与土地收益关联度分析

以攀枝花市为例,综合运用GIS空间分析技术和变异系数权重分析、灰色关联度等方法建立了城市基础设施与土地收益的关联度模型,定量分析城市基础设施与土地收益的关联关系,揭示两者间的关联规律和作用机理.结果表明：①城市基础与土地收益存在较大关联性;②城市基础设施与土地收益关联度在时间序列上具有明显的波动性且呈周期性变化;③城市基础设施与土地收益关联度在空间上呈分异特征.     

低碳经济视角下的城市圈土地节约集约利用评价研究——基于遗传算法的投影寻踪模型

从低碳经济视角出发,运用基于遗传算法的投影寻踪模型对武汉城市圈低碳土地节约基于利用水平进行了评价研究.结果显示,各市低碳土地节约集约利用水平差异较大,发展极不协调,难以有效地实现城市圈协同发展.武汉城市圈应以整体效益最大化为目标,注重保护环境与经济增长相结合,大力发展低碳经济,以协同发展促进低碳土地利用.     

Bumblebee Vulnerability: Common Correlates of Winners and Losers across Three Continents

Abstract:  It is widely agreed that in many parts of the world some bumblebee ( Bombus ) species have declined, and that this has often been driven by land-use changes that cause reductions in the abundance of food plants. There is much less agreement about how changes in food plants affect some bumblebee species more than others. We sought to identify which species' characteristics are generally associated with the relative winners and losers by comparing the 3 independent bumblebee faunas from parts of Britain, Canada, and China. Using available survey data, we assessed species characteristics, including competition with congeners, climatic specialization, proximity to climatic range edge, food specialization, phenology, body size, and range size. Results of our meta-analysis of correlations showed support for the hypotheses that decline susceptibility is generally greater for species that have greater climatic specialization, for species in areas where they occur closest to the edges of their climatic ranges, and for species that have queens that become active later in the year. The latter characteristic may render a species at a particular disadvantage when they have long colony cycles if there are losses of food plants in mid to late colony development.     

Medium Scale Spatial Structures of Polycyclic Aromatic Hydrocarbons in the Topsoil of Tianjin Area

The spatial distribution patterns of Polycyclic Aromatic Hydrocarbons (PAHs) in soil are important to regional environmental assessment. In this paper, the spatial structural features of sixteen prior PAH compounds in the topsoil of Tianjin area, as well as soil properties, were studied. Results shown that medium scale spatial autocorrelations were well revealed. Spherical models with sills could be used to fit all experimental variograms. The spatial structures of PAHs contents demonstrated significant anisotropy. Air precipitation caused by the combustion of coal was the key factor in the formation of the spatial structural patterns of PAHs in the topsoil of Tianjin area.     

芳香类有机物氯化生成消毒副产物的特性研究

选择有代表性的芳香类有机物,在含有腐殖酸的水溶液中进行氯化试验.测定三卤甲烷和卤乙酸的生成特性.并分析有机物的化学结构对生成消毒副产物的影响.结果表明.各受试物氯化生成消毒副产物的活性和反应速率排序为间苯二酚>对苯二酚>邻苯二酚>苯酚>苯胺>苯甲酸>硝基苯;芳香类有机物苯环上官能团的性质、数量和位置等影响消毒副产物的生成;间苯二酚的氯化反应可分为快速反应阶段和慢速反应阶段.     

Effect of Widespread Agricultural Chemical Use on Butterfly Diversity across Turkish Provinces

Although agricultural intensification is thought to pose a significant threat to species, little is known about its role in driving biodiversity loss at regional scales. I assessed the effects of a major component of agricultural intensification, agricultural chemical use, and land‐cover and climatic variables on butterfly diversity across 81 provinces in Turkey, where agriculture is practiced extensively but with varying degrees of intensity. I determined butterfly species presence in each province from data on known butterfly distributions and calculated agricultural chemical use as the proportion of agricultural households that use chemical fertilizers and pesticides. I used constrained correspondence analyses and regression‐based multimodel inference to determine the effect of environmental variables on species composition and richness, respectively. The variation in butterfly species composition across the provinces was largely explained (78%) by the combination of agricultural chemical use, particularly pesticides, and climatic and land‐cover variables. Although overall butterfly richness was primarily explained by climatic and land‐cover variables, such as the area of natural vegetation cover, threatened butterfly richness and the relative number of threatened butterfly species decreased substantially as the proportion of agricultural households using pesticides increased. These findings suggest that widespread use of agricultural chemicals, or other components of agricultural intensification that may be collinear with pesticide use, pose an imminent threat to the biodiversity of Turkey. Accordingly, policies that mitigate agricultural intensification and promote low‐input farming practices are crucial for protecting threatened species from extinction in rapidly industrializing nations such as Turkey. Efectos del Uso Extensivo de Agroquímicos sobre la Diversidad de Mariposas en Provincias Turcas     

Lichen Conservation in Heavily Managed Boreal Forests

Lichens are an important component of the boreal forest, where they are long lived, tend to accumulate in older stands, and are a major food source for the threatened woodland caribou (Rangifer tarandus caribou). To be fully sustainable, silvicultural practices in the boreal forest must include the conservation of ecological integrity. Dominant forest management practices, however, have short‐term negative effects on lichen diversity, particularly the application of herbicides. To better understand the long‐term effects of forest management, we examined lichen regeneration in 35 mixed black spruce (Picea mariana) and jack pine (Pinus banksiana) forest stands across northern Ontario to determine recovery following logging and postharvest silvicultural practices. Our forest stands were 25–40 years old and had undergone 3 common sivilcultural treatments that included harvested and planted; harvested, planted, and treated with N‐[phosphonomethyl] glycine (glyphosate); and harvested, planted, and treated with 2,4‐dichlorophenoxyacetic acid (2,4‐D). Forest stands with herbicide treatments had lower lichen biomass and higher beta and gamma diversity than planted stands that were not treated chemically or control stands. In northwestern Ontario, planted stands that were not treated chemically had significantly greater (p < 0.05) alpha diversity than stands treated with herbicides or control stands. Our results show that common silvicultural practices do not emulate natural disturbances caused by wildfires in the boreal forest for the lichen community. We suggest a reduction in the amount of chemical application be considered in areas where lichen biomass is likely to be high and where the recovery of woodland caribou is an objective. Conservación de Líquenes en Bosques Boreales Manejados Intensivamente     

A feasibility and cost comparison of perchloroethylene dry cleaning to professional wet cleaning: case study of Silver Hanger Cleaners, Bellingham, Massachusetts

The Toxics Use Reduction Institute (TURI) has been working with the dry cleaning sector for over 10 years - focusing on the ultimate goal of eliminating the use of perchloroethylene in this sector due to the availability of less toxic, feasible alternatives. Professional wet cleaning has been identified as one of these alternatives and has been a focus of the Institute in recent years. In 2008, the Institute provided a matching grant to Silver Hanger Cleaners in Bellingham, Massachusetts to convert their operations from perchloroethylene-based to water-based processes. Two years of data have been collected from the facility, reflecting one year of solvent use and one year of dedicated professional wet cleaning. The analysis of that data is presented here, including capital costs, performance data and associated costs, operational costs, and resource use and associated costs.     

基于协调发展视角的区域发展差异研究

20世纪90年代以来，区域差异研究成为学术界和政府管理者关注的热点领域。长期以来学者们主要以单一经济指标或复合经济指标作为衡量因子，分析区域经济差异时空演变及差异背后的自然、社会、经济驱动机理。从可持续发展的角度看，区域发展不单是区域经济的发展，而应是社会、经济与资源环境三方面的协调。基于这一理解，从可持续协调发展入手，建立了区域发展综合评价指标体系，选取了表征社会进步、经济发展和资源环境支持3个方面的27个因素作为评价指标，分析了区域综合发展的测算方法，提出了综合发展指数和发展协调指数。在案例分析中运用所设计的测度方法对江苏省内县级行政单位的综合发展进行了评价和分析。