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排序方式: 共有439条查询结果,搜索用时 484 毫秒
1.
资源型城市可持续发展能力的演变与调控 总被引:16,自引:0,他引:16
作为特殊的经济区,资源型城市的衰落与振兴日益成为社会关注的热点。本文从分析资源型城市可持续发展能力入手,论述了资源型城市发展能力的成长阶段及演变特征,提出了资源城市可持续发展能力调控的模式和途径。 相似文献
2.
Based on density functional theory (DFT) and basic structure models, the chemical reactions on the surface of vanadium-titanium based selective catalytic reduction (SCR) denitrification catalysts were summarized. Reasonable structural models (non-periodic and periodic structural models) are the basis of density functional calculations. A periodic structure model was more appropriate to represent the catalyst surface, and its theoretical calculation results were more comparable with the experimental results than a non-periodic model. It is generally believed that the SCR mechanism where NH3 and NO react to produce N2 and H2O follows an Eley-Rideal type mechanism. NH2NO was found to be an important intermediate in the SCR reaction, with multiple production routes. Simultaneously, the effects of H2O, SO2 and metal on SCR catalysts were also summarized. 相似文献
3.
定量风险评价标准探讨 总被引:12,自引:0,他引:12
围绕定量评价标准对风险的度量和制定风险评价标准的基本原则等方面的进展和存在的问题进行了初步的探讨,分析归纳了国处有着的个人风险和社会风险标准,提出具有重大危害性的工业设施对员工或公众造成的风险,不应显著高于人们在日常生活中接触到其他风险;每年10^-6的死亡风险是可以忽略不计的个人风险水平等观点。 相似文献
4.
烧结砖生产中氟的逸出及钙基废渣固氟特性研究 总被引:4,自引:0,他引:4
砖坯烧制过程中,氟逸出的初始温度约为600℃,大部分氟在约800℃至砖坯发生明显烧结的温度内逸出,以CaO含量高的粘土原料制砖,氟逸出量相对较少。在此基础上,提出在制砖原料中添加适量钙基废渣抑制氟的逸出,并进行了详细的实验室和工业性试验;结果表明,在适宜添加量下,存氟率由约25%增至70%以下,且不影响砖制品质量。 相似文献
5.
Wu Rui Li Guangyi Zhang Zongyi Ren Yulong Han Weijian 《Frontiers of Environmental Science & Engineering in China》2007,1(3):292-298
Road transport produces significant amounts of emissions by using crude oil as the primary energy source. A reduction of emissions
can be achieved by implementing alternative fuel chains. The objective of this study is to carry out an economic, environmental
and energy (EEE) life cycle study on natural gas-based automotive fuels with conventional gasoline in an abundant region of
China. A set of indices of four fuels/vehicle systems on the basis of life cycle are assessed in terms of impact of EEE, in
which natural gas produces compressed natural gas (CNG), methanol, dimethylether (DME) and Fischer Tropsch diesel (FTD). The
study included fuel production, vehicle production, vehicle operation, infrastructure and vehicle end of life as a system
for each fuel/vehicle system. A generic gasoline fueled car is used as a baseline. Data have been reviewed and modified based
on the best knowledge available to Chongqing local sources. Results indicated that when we could not change electric and hydrogen
fuel cell vehicles into commercial vehicles on a large scale, direct use of CNG in a dedicated or bi-fuel vehicle is an economical
choice for the region which is most energy efficient and more environmental friendly. The study can be used to support decisions
on how natural gas resources can best be utilized as a fuel/energy resource for automobiles, and what issues need to be resolved
in Chongqing. The models and approaches for this study can be applied to other regions of China as long as all the assumptions
are well defined and modified to find a substitute automotive energy source and establish an energy policy in a specific region. 相似文献
6.
Thórólfur Matthíasson 《Natural resources forum》2003,27(1):1-18
The article outlines the development of Iceland's fishery rights and the extension of its territorial waters between the 1950s and the mid‐1970s, whereby Iceland gained exclusive control and use of the marine resources of the waters within 12, later 50, and ultimately 200 nautical miles around the island. The article concentrates on four of Iceland's main fisheries: shrimp, herring, capelin and cod. These four fisheries are discussed separately and in depth, presenting the beginnings and growth of the industry and detailing the development of management practices and the corresponding legislation and regulatory measures. Iceland's initial concern was to gain control over the marine resources surrounding the island, but once this was achieved, the focus of attention shifted to managing first the economic and soon also the ecological aspects of its tremendous resource. Informed mainly by indigenous expertise, Iceland's concern was to limit overfishing, manage its fisheries sustainably both from the economic and ecological points of view, and find the best ways to distribute the revenues from the marine harvest. The article looks at each of the four fisheries to clarify how the individual transferable quota (ITQ) system came into being, how initial quota holdings were allotted, and analyses the circumstances under which the ITQ system became the management tool of choice. For each fishery, the process of regulatory evolution was quite unique. At the same time, there is a common pattern to all the fisheries, which may be summarized as follows. Firstly, serious attempts to reform management practices only got underway when the fishery had collapsed or was close to collapse. Secondly, stakeholders invariably started the process of regulation by limiting access to the fishery. Thirdly, a variety of rules were implemented to allocate rights to participate in the fishery to additional entrants once membership had been closed. Finally, prior to the invention of the ITQ system, prices were used to manage fisheries in Iceland. It may be concluded that the management of fisheries by ITQs may be a historical accident, rather than the end point of a logical evolution. 相似文献
7.
性能化设计标准在火灾安全设计中的应用 总被引:10,自引:3,他引:10
随着建筑向着高层化、大型化的趋势发展 ,目前世界上许多国家的建筑设计正逐步地从处方式规范转换到性能化规范。性能化规范的成功实施需要建立性能化设计标准。在建筑火灾安全设计中 ,使用的性能化设计标准包括确定性设计标准和偶然性设计标准。确定性设计标准主要与火灾的发生、发展和蔓延等级 ,以及生命安全等级有关。偶然性设计标准主要关心火灾发生的可能性及产生的后果。文章最后对性能化设计标准的应用情况进行了讨论和总结 相似文献
8.
James F. Saunders Marylee Murphy Martyn Clark William M. Lewis 《Journal of the American Water Resources Association》2004,40(5):1339-1349
ABSTRACT: Historical flow records are used to estimate the regulatory low flows that serve a key function in setting discharge permit limits through the National Pollutant Discharge Elimination System, which provides a nationwide mechanism for protecting water quality. Use of historical records creates an implicit connection between water quality protection and climate variability. The longer the record, the more likely the low flow estimate will be based on a broad set of climate conditions, and thus provides adequate water quality protection in the future. Unfortunately, a long record often is not available at a specific location. This analysis examines the connection between climate variability and the variability of biologically based and hydrologically based low flow estimates at 176 sites from the Hydro‐Climatic Data Network, a collection of stream gages identified by the USGS as relatively free of anthropogenic influences. Results show that a record of 10 to 20 years is necessary for satisfactory estimates of regulatory low flows. Although it is possible to estimate a biologically based low flow from a record of less than 10 years, these estimates are highly uncertain and incorporate a bias that undermines water quality protection. 相似文献
9.
We designed 3 image‐based field guides to tropical forest plant species in Ghana, Grenada, and Cameroon and tested them with 1095 local residents and 20 botanists in the United Kingdom. We compared users’ identification accuracy with different image formats, including drawings, specimen photos, living plant photos, and paintings. We compared users’ accuracy with the guides to their accuracy with only their prior knowledge of the flora. We asked respondents to score each format for usability, beauty, and how much they would pay for it. Prior knowledge of plant names was generally low (<22%). With a few exceptions, identification accuracy did not differ significantly among image formats. In Cameroon, users identifying sterile Cola species achieved 46–56% accuracy across formats; identification was most accurate with living plant photos. Botanists in the United Kingdom accurately identified 82–93% of the same Cameroonian species; identification was most accurate with specimens. In Grenada, users accurately identified 74–82% of plants; drawings yielded significantly less accurate identifications than paintings and photos of living plants. In Ghana, users accurately identified 85% of plants. Digital color photos of living plants ranked high for beauty, usability, and what users would pay. Black and white drawings ranked low. Our results show the potential and limitations of the use of field guides and nonspecialists to identify plants, for example, in conservation applications. We recommend authors of plant field guides use the cheapest or easiest illustration format because image type had limited bearing on accuracy; match the type of illustration to the most likely use of the guide for slight improvements in accuracy; avoid black and white formats unless the audience is experienced at interpreting illustrations or keeping costs low is imperative; discourage false‐positive identifications, which were common; and encourage users to ask an expert or use a herbarium for groups that are difficult to identify. Pruebas Empíricas de Guías de Campo de Plantas Hawthorne, Cable & Marshall 相似文献
10.
Use of the arts in international aid is common in an ad hoc form, but it has not been systematically theorised or evaluated. The arts have the potential to be a culturally contextualised and sustainable intervention for adults and children in the aftermath of war or disaster. On the micro level, the arts are a method to enable the retrieval and reprocessing of traumatic memories that are often encoded in images rather than in words. On a macro level, they can help to reconstruct a group narrative of a disaster as well as mobilise people back into control of their lives. This paper researches a long‐term project using arts in Sri Lanka following the civil war and tsunami. A central finding is the need to understand arts within their cultural context, and their usefulness in strengthening the voices and problem‐solving capacities of the victims of the disaster. 相似文献