排序方式: 共有38条查询结果,搜索用时 218 毫秒
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生态安全是人类可持续发展的基石,目前,生态安全问题已成为中国经济可持续发展的瓶颈。在深入分析经济社会系统与生态系统之间关系的基础上,认为生态安全问题凸显的根源在于经济社会系统对生态系统的过度干预,且经济社会系统运行生态化和资源利用高效化是缓解经济发展与生态安全之间矛盾的关键;从系统的高度,围绕生态化与高效化剖析循环经济的内涵,并从理论上分析"3R"原则及其经济实践与生态安全的关系,认为循环经济是经济社会系统在资源利用方面的系统变革,可有效推动经济发展与生态安全协同共进。 相似文献
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Matt Gillen Author Vitae 《Journal of Safety Research》2010,41(3):289-299
The U.S. National Institute for Occupational Safety and Health (NIOSH) conducts research to improve and protect the health and safety of workers. This paper describes the experience of the NIOSH Construction Program with two recent program planning initiatives intended to improve the program: (a) an independent external review of work over the past decade and (b) the development of strategic goals organized into a “National Construction Agenda” to guide a decade of future work. These goals, developed with input from construction industry stakeholders and researchers, are a part of the NIOSH National Occupational Research Agenda (NORA) initiative. The NORA goals are intended to provide an ambitious set of goals for all construction stakeholders to work together on. Both efforts relate to insuring the relevance and impact of research, reflecting an emerging policy perspective that research programs should be judged not just by the quality and quantity of science produced, but by the industry impact and tangible benefit resulting from the research. This paper describes how views on research planning have evolved to incorporate lessons learned about how research leads to improved safety and health for workers. It also describes the process used to develop the goals and the resulting strategic and intermediate goals that comprise the National Construction Agenda. 相似文献
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澜沧江的跨境径流量变化及其对云南降水量场变化的响应 总被引:8,自引:1,他引:7
随着澜沧江-湄公河次区域经济合作等重大区域合作行动的蓬勃开展,该流域水文水资源系统的变化、规律及其影响已成为国际关注和研究的热点。为考查气候变化对澜沧江-湄公河流域水文水生态环境变化影响的基本事实,以云南境内澜沧江径流量观测数据和云南的同期降水量场观测数据为基础,应用小波变换和相关系数的统计分析方法,研究了澜沧江跨境径流量变化的多时间尺度特征及其对云南降水量场变化的响应。结论为:澜沧江上下游的年径流量变化表现出了十分明显的多时间尺度变化特征,它们之间的差异主要表现在较小的时间尺度上,而对于较大的时间尺度,它们之间的变化特征是十分相似的;澜沧江上下游的年径流量变化与云南的年降水量场变化之间存在有十分显著的相关关系;云南年降水量场变化的多时间尺度特征与澜沧江上下游的年径流量变化的多时间尺度特征是相似的。总之,澜沧江的跨境径流量变化主要是由于云南降水量场的变化造成的,特别是在较大的时间尺度上,澜沧江上下游的径流量变化都对云南降水量场的变化有极好的响应特征。 相似文献
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D301弱碱性阴离子交换树脂吸附Cr(Ⅵ)的研究 总被引:1,自引:0,他引:1
实验探索性地采用D301弱碱性阴离子交换树脂去除重金属废水中的C(rⅥ),为开发出一种高效、安全的处理、富集和回收含C(rⅥ)废水的新工艺提供理论和实验依据。静态吸附实验结果表明,该树脂对C(rⅥ)的吸附量随pH的降低而增加,在pH=2时吸附量为17.54 mg/g;吸附平衡过程符合Freundlich方程,且最大吸附量为94.34 mg/g;动力学和热力学研究表明,吸附过程为颗粒扩散控制,自发且放热的,表观吸附活化能为E(a300 mg/L)=16 243.06 kJ/mol;树脂的再生能力强,经过3次再生,树脂的平衡吸附量仅下降了8.54%;动态吸附和洗脱实验表明,以5%NaOH溶液为洗脱剂效果最佳,洗脱液浓度高达6 918.74 mg/L,浓缩了约69倍,且动态洗脱曲线没有托尾现象;该树脂尤其适合处理低浓度含C(rⅥ)废水(≤100 mg/L),且几乎不受流速限制。 相似文献
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In this paper, we focus on assessing the performance of diverse turbulence closures in the simulation of dilute sediment-laden,
open-channel flows. To that end, we base our analysis on a framework developed in a companion paper of this special issue,
which puts forward a standard sediment transport model (SSTM), a partial two-fluid model (PTFM) and a complete two-fluid model
(CTFM), in three- and one-dimensional (3D and 1D) versions. First, we propose in this paper extensions of the transport equations
for the Reynolds stresses, and of the equations of the K–ω model to two-phase flows, starting from the general two-fluid model. We consider the drag force to be the predominant force
amongst all the interactions between the two phases (water and sediment). Second, under the framework of models formed by
the SSTM, the PTFM and the CTFM, we discuss simulation results obtained by employing the Reynolds stress model (RSM), the
algebraic stress model (ASM), and the K–rc="/content/4g4637863864125r/10652_2008_9118_Article_IEq1.gif" alt="$$\varepsilon$$" align="middle" border="0"> and the K–ω models (in their standard and extended versions), paired with each member of the framework. To assess the accuracy of the
models, we compare numerical results with the experimental datasets of Vanoni, Trans ASCE 111:67–133, 1946; Coleman, Water
Resour Res 22(10):1377–1384, 1986; Muste and Patel, J Hydraul Eng 123(9):742–751, 1997; Nezu and Azuma, J Hydraul Eng 130:988–1001,
2004; Muste et al. Water Resour Res 41:W10402, 2005 . Third, we obtain from those comparisons the values of the Schmidt number
that facilitate the agreement of model predictions with data. We conclude that the standard K–rc="/content/4g4637863864125r/10652_2008_9118_Article_IEq2.gif" alt="$$\varepsilon$$" align="middle" border="0"> model, the ASM and the K–ω models all provide satisfactory descriptions of flow variables and sediment concentrations in open-channel flows; further,
we show that the more complicated RSM does not provide much improvement in dilute sediment transport as compared to those
previous models, even when it is paired with the CTFM. We also show that the inclusion of model extensions in the turbulence
closures does not improve the predictions for dilute mixtures either. We find that our values for the Schmidt number agree
well with available data, and we provide an explanation for the variation of the Schmidt number with the ratio of the fall
velocity and the wall-friction (shear) velocity. Finally, we corroborate that the Schmidt number is the key parameter to obtain
satisfactory predictions of sediment transport in suspension. 相似文献
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Conservation efforts are often motivated by the threat of global extinction. Yet if conservationists had more information suggesting that extirpation of individual species could lead to undesirable ecological effects, they might more frequently attempt to protect or restore such species across their ranges even if they were not globally endangered. Scientists have seldom measured or quantitatively predicted the functional consequences of species loss, even for large, extinction‐prone species that theory suggests should be functionally unique. We measured the contribution of Asian elephants (Elephas maximus) to the dispersal of 3 large‐fruited species in a disturbed tropical moist forest and predicted the extent to which alternative dispersers could compensate for elephants in their absence. We created an empirical probability model with data on frugivory and seed dispersal from Buxa Tiger Reserve, India. These data were used to estimate the proportion of seeds consumed by elephants and other frugivores that survive handling and density‐dependent processes (Janzen‐Connell effects and conspecific intradung competition) and germinate. Without compensation, the number of seeds dispersed and surviving density‐dependent effects decreased 26% (Artocarpus chaplasha), 42% (Careya arborea), and 72% (Dillenia indica) when elephants were absent from the ecosystem. Compensatory fruit removal by other animals substantially ameliorated these losses. For instance, reductions in successful dispersal of D. indica were as low as 23% when gaur (Bos gaurus) persisted, but median dispersal distance still declined from 30% (C. arborea) to 90% (A. chaplasha) without elephants. Our results support the theory that the largest animal species in an ecosystem have nonredundant ecological functionality and that their extirpation is likely to lead to the deterioration of ecosystem processes such as seed dispersal. This effect is likely accentuated by the overall defaunation of many tropical systems. 相似文献