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排序方式: 共有951条查询结果,搜索用时 906 毫秒
331.
文章运用人工神经网络方法,选取了8个经济指标,以黑龙江省2004年统计年鉴为数据源,对年黑龙江省66个县(市)的社会经济发展水平进行评价。结果表明:黑龙江省县域经济整体发展水平不高,而且区域差异显著;根据评价结果利用聚类分析方法将黑龙江省县域经济发展水平分为5级。文章最后提出了促进县域经济发展的措施。 相似文献
332.
环境样品中多氯联苯的分析技术 总被引:4,自引:0,他引:4
作为一种持久性有机污染物,多氯联苯在地球上的分布十分广泛。然而由于多氯联苯在环境样品中残留浓度低、干扰物质多且组成复杂,必须对环境样品进行预处理。目前较为常用的含多氯联苯样品的前处理技术有:溶剂萃取技术、固相萃取技术、固相微萃取技术、超临界萃取技术、微波萃取技术和加速溶剂萃取技术等,分析经过技术处理以后的样品常用的方法有化学分析方法和生物分析方法,化学方法包括气相色谱法,气相色谱质谱分析法等;生物方法有生物传感器测定法、表面胞质团共振检测、以Ah受体为基础的生物分析法和酶联免疫检测法。中国在这方面的研究投入不够,应加大人力、财力和物力的支持,提高环境样品中多氯联苯的检测水平。 相似文献
333.
Harry X.ZHANG Shaw L.YU 《Frontiers of Environmental Science & Engineering in China》2008,2(3):267-273
One of the key challenges in the total maximum daily load (TMDL) development process is how to define the critical condition
for a receiving waterbody. The main concern in using a continuous simulation approach is the absence of any guarantee that
the most critical condition will be captured during the selected representative hydrologic period, given the scarcity of long-term
continuous data. The objectives of this paper are to clearly address the critical condition in the TMDL development process
and to compare continuous and event-based approaches in defining critical condition during TMDL development for a waterbody
impacted by both point and nonpoint source pollution. A practical, event-based critical flow-storm (CFS) approach was developed
to explicitly addresses the critical condition as a combination of a low stream flow and a storm event of a selected magnitude,
both having certain frequencies of occurrence. This paper illustrated the CFS concept and provided its theoretical basis using
a derived analytical conceptual model. The CFS approach clearly defined a critical condition, obtained reasonable results
and could be considered as an alternative method in TMDL development. 相似文献
334.
The increasing volume of CO2 embodiment in international trade adds a layer of complexity to environmental policies and has raised arguments on the traditional
production based responsibility for CO2 emissions. In order to help understand the quantity of CO2 embodiment in trade and its policy implications, this paper gives observations to recently emerging literatures that quantitatively
discuss CO2 embodiment in trade. The analytical approaches share the principle of using input and output modeling but vary dramatically
in study boundary and estimation accuracy. The calculations can be roughly categorized into three types: direct quantification
of CO2 embodiments in multiregional trade, direct quantification of CO2 embodiment in bilateral trade, and indirect analysis by comparing the scenarios with or without trade. The practical estimations
strongly rely on trade partner selection and data availability. An obvious imbalance of net CO2 embodiment in the commodity trade between major developed countries and developing economies as a whole was confirmed by
these literatures. Carbon taxes and other possible limitations on CO2 emissions have been addressed. The consistency across the calculations could be enhanced by systematic analyses in more detail
to convince the international community to take binding commitments for the reduction of global CO2 emissions. 相似文献
335.
Yang Su Ye Qi Zhouyan Xiao Yu Wei 《Frontiers of Environmental Science & Engineering in China》2009,3(1):75-90
With the development of rural pollution, its characteristic and institutional factor should be studied for pollution control
through economics and sociology. Based on the data gathered from investigations by several government sectors, rural environmental
pollution can be divided into two types by its sources: internal source type and external source type. The internal source
type is the main component of rural pollution at present, which can be further divided into three types. Research shows that
the contributing institutional factors of rural pollution issues and the effectiveness of environmental management system
over rural pollution can be summarized as distinctiveness. In essence, the rural pollution issue results from the dualism
of rural and urban areas’ inadaptability to rural modernization. In detail, the contributing factors can be summed up on three
institutional levels. There are obvious loopholes in rural environmental management system which, in the meantime, is incapable
and inadaptable to rural pollution control. There exist similar questions in the related public service system, which are
intensified by inappropriate reform which brought about incompatible incentive in the recent years. However, in the eleventh
five-year plan period, there are advantageous trends in the three institutional levels.
Main data sources in this paper: ➀ the surveys on TVEs (township and village enterprises) conducted by Township Enterprise
Bureau of Ministry of Agriculture of China in 1997 and 2002; ➁ the partial survey on rural environmental conditions by EPA
(environmental protection administration) of Zhejiang Province in 2002; ➂ the survey on the pollution of IPLFs (livestock
and poultry farms) in 23 provinces, municipalities, and directly administered cities by the State Environmental Protection
Administration of China in 2002; ➃ the research report on Mechanism of Investment and Financing for Environmental Protection
by China Council for International Environment and Development Cooperation in 2003; ➄ the third investigation on national
hygiene service in 2003; ➅ the regular monitoring of safe quality of agricultural products by the Ministry of Agriculture
of China in 2005; ➆ the investigation arranged by the Ministry of Health which finished in 2007 and showed the total situation
of rural environmental health and drinking water security of the whole country. 相似文献
336.
Analytical solutions of three-dimensional contaminant transport in uniform flow field in porous media: A library 总被引:1,自引:0,他引:1
Hongtao Wang Huayong Wu 《Frontiers of Environmental Science & Engineering in China》2009,3(1):112-128
The purpose of this study is to present a library of analytical solutions for the three-dimensional contaminant transport
in uniform flow field in porous media with the first-order decay, linear sorption, and zero-order production. The library
is constructed using Green’s function method (GFM) in combination with available solutions. The library covers a wide range
of solutions for various conditions. The aquifer can be vertically finite, semi-infinitive or infinitive, and laterally semi-infinitive
or infinitive. The geometry of the sources can be of point, line, plane or volumetric body; and the source release can be
continuous, instantaneous, or by following a given function over time. Dimensionless forms of the solutions are also proposed.
A computer code FlowCAS is developed to calculate the solutions. Calculated results demonstrate the correctness of the presented
solutions. The library is widely applicable to solve contaminant transport problems of one- or multiple- dimensions in uniform
flow fields. 相似文献
337.
Evidence in the literature suggests that employees can engage in other types of creative behavior at work beyond producing something new and useful for their organization. This paper seeks to advance our understanding of these “atypical” creative behaviors. We conceptualize a typology that encompasses both the commonly studied form of employee creativity (conventional steward‐type) and three other types of employee creativity that have not been previously theorized (critical steward‐type, cunning agent‐type, and innocent agent‐type). We then advance a conceptual model to identify situations that may lead employees to use their creative potential one way versus another. Further, we examine the different implications of these creative behaviors for the organization, employee, and society. Our conceptual framework provides a broader perspective of workplace creativity in which a wider range of behaviors, mechanisms, and outcomes must be considered. It provides new directions for future research as well as implications for managing creativity in different organizational and cultural contexts. 相似文献
338.
运用超声提取、氧化铝-硅胶组合填料层析净化、气相色谱-质谱联用(GC-MS)检测,建立了设施番茄植株根、茎、叶和果实中同时测定百菌清和毒死蜱含量的分析方法。针对设施番茄植株叶绿素含量高的特点,优化了层析柱填料和洗脱溶剂配比,并研究了两种农药在层析柱中的洗脱规律。结果表明,在番茄根、茎、叶和果实中,百菌清平均回收率分别为... 相似文献
339.
Chronic institutional failure and enhanced vulnerability to flash‐floods in the Cuenca Altadel Río Lerma,Mexico
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The dominant paradigm in disaster risk reduction (DRR) policies has been seriously contested because of its reliance on interventions based on technocratic expertise. In the Mexican context, the influence of informal practices such as clientelism and cartelisation of the political system produces environmental degradation and vulnerability to disasters within the communities in the study site. This paper contributes to understanding of failed institutional processes and parallel practices that intensify vulnerability to disasters by contrasting the discourses of agents within a peri‐urban community in central Mexico. Employing the Situational Analysis Approach as a methodological framework, the study identifies divergent views and practices within the community, leading to different responses to disasters and to different perceptions regarding institutional performance. In addition, it finds that institutional decision‐making, based only on scientific and technical expertise, has resulted in unintended consequences that influence ongoing vulnerability to floods in the site under review. 相似文献
340.
水土保持生态补偿对于我国的水土流失治理意义重大,水土保持补偿标准的确定是建立生态补偿机制的核心问题。基于潘家口水库上游东北沟流域1990年和2009年土地利用数据和气候、 土壤、 植被、 DEM及农户调查等数据,应用通用土壤侵蚀方程模型(RUSLE)计算该流域采取预防水土流失措施后的土壤侵蚀减少量,在此基础上采用环境经济学的方法核算水土保持生态功能的提供方和受益方两个主体的成本和收益,并构建了水土保持生态补偿标准计算模型,实现了水土保持生态补偿标准定量计算。结果显示:流域生态系统的年土壤保持量为6.49×104 t·a-1;水土保持服务提供方损失为24.48×104元,所得收益来自减少土地损失和肥力损失的价值共计44.21×104元;水土保持服务受益方主要指下游潘家口水库所得收益来自减少泥沙淤积和减少富营养化共计84.88×104元;流域所得的补偿介于24.48×104元(222.55元/人)到46.90×104元(426.36元/人)之间。 相似文献