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排序方式: 共有275条查询结果,搜索用时 851 毫秒
91.
探讨了项目财务评价结果和项目敏感性分析技术的应用方法,为某公司唐山中厚板厂污水处理回用项目融资方案和运营方案的决策提供依据.介绍了唐山中厚板材有限公司废水回收利用工程项目概况;确定了该项目的基础数据,进行财务分析,这是进行后续敏感性分析的基础.对此项目进行敏感性分析,找出影响该项目收益的敏感性因素,为该项目执行时的风险管理提供一定依据. 相似文献
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为充分发挥前兆数字化数据在地震预报中的作用 ,研制了基于SQL网络数据库的通用接口程序。该程序通过ODBC数据源直接从网上对数据库进行存取 ,并通过数据导出和日期格式的转换而形成前兆分析人员所需的数据格式。 相似文献
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Importance of dispersal routes that minimize open‐ocean movement to the genetic structure of island populations 下载免费PDF全文
E. L. Harradine M. E. Andrew J. W. Thomas R. A. How L. H. Schmitt P. B. S. Spencer 《Conservation biology》2015,29(6):1704-1714
Islands present a unique scenario in conservation biology, offering refuge yet imposing limitations on insular populations. The Kimberley region of northwestern Australia has more than 2500 islands that have recently come into focus as substantial conservation resources. It is therefore of great interest for managers to understand the driving forces of genetic structure of species within these island archipelagos. We used the ubiquitous bar‐shouldered skink (Ctenotus inornatus) as a model species to represent the influence of landscape factors on genetic structure across the Kimberley islands. On 41 islands and 4 mainland locations in a remote area of Australia, we genotyped individuals across 18 nuclear (microsatellite) markers. Measures of genetic differentiation and diversity were used in two complementary analyses. We used circuit theory and Mantel tests to examine the influence of the landscape matrix on population connectivity and linear regression and model selection based on Akaike's information criterion to investigate landscape controls on genetic diversity. Genetic differentiation between islands was best predicted with circuit‐theory models that accounted for the large difference in resistance to dispersal between land and ocean. In contrast, straight‐line distances were unrelated to either resistance distances or genetic differentiation. Instead, connectivity was determined by island‐hopping routes that allow organisms to minimize the distance of difficult ocean passages. Island populations of C. inornatus retained varying degrees of genetic diversity (NA = 1.83 – 7.39), but it was greatest on islands closer to the mainland, in terms of resistance‐distance units. In contrast, genetic diversity was unrelated to island size. Our results highlight the potential for islands to contribute to both theoretical and applied conservation, provide strong evidence of the driving forces of population structure within undisturbed landscapes, and identify the islands most valuable for conservation based on their contributions to gene flow and genetic diversity. 相似文献
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Daniel Ovando Jennifer E. Caselle Christopher Costello Olivier Deschenes Steven D. Gaines Ray Hilborn Owen Liu 《Conservation biology》2021,35(6):1861-1870
Marine protected areas (MPAs) cover 3–7% of the world's ocean, and international organizations call for 30% coverage by 2030. Although numerous studies show that MPAs produce conservation benefits inside their borders, many MPAs are also justified on the grounds that they confer conservation benefits to the connected populations that span beyond their borders. A network of MPAs covering roughly 20% of the Channel Islands National Marine Sanctuary was established in 2003, with a goal of providing regional conservation and fishery benefits. We used a spatially explicit bioeconomic simulation model and a Bayesian difference-in-difference regression to examine the conditions under which MPAs can provide population-level conservation benefits inside and outside their borders and to assess evidence of those benefits in the Channel Islands. As of 2017, we estimated that biomass densities of targeted fin-fish had a median value 81% higher (90% credible interval: 23–148) inside the Channel Island MPAs than outside. However, we found no clear effect of these MPAs on mean total biomass densities at the population level: estimated median effect was –7% (90% credible interval: –31 to 23) from 2015 to 2017. Our simulation model showed that effect sizes of MPAs of <30% were likely to be difficult to detect (even when they were present); smaller effect sizes (which are likely to be common) were even harder to detect. Clearly, communicating expectations and uncertainties around MPAs is critical to ensuring that MPAs are effective. We provide a novel assessment of the population-level effects of a large MPA network across many different species of targeted fin-fish, and our results offer guidance for communities charged with monitoring and adapting MPAs. 相似文献
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三峡生态屏障区农户退耕受偿意愿的调查分析 总被引:4,自引:0,他引:4
运用参与式农户评估方法,对三峡生态屏障区内农户退耕还林的受偿意愿进行了调查.分析表明,退耕还林的生态效益受到普遍认可,但其可持续性令人担忧.1355份有效问卷中,愿意接受补偿的占74%,对未来生计的预期与土地相关性低的农户更愿意退耕.受偿意愿的形成具有明显的社会异质性和区域差异性.受访者性别、耕地面积、家庭年收入、帮扶形式、是否移民对受偿意愿值具有显著影响.屏障区平均补偿意愿为1014元/(亩×a).万州、秭归、渝北的受偿意愿值高于平均水平.建立基于区域的生态补偿标准和多元化的生态补偿方式,可以弥补目前均一型生态补偿标准和方式的不足,促进退耕还林工程和区域的可持续发展. 相似文献
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数控机床的故障诊断 总被引:1,自引:0,他引:1
白恩远 《中国安全科学学报》1996,6(3):48-52
针对数控机床的故障特点,主要介绍了数控机床机械类故障和电气类故障的诊断程序和诊断方法。 相似文献