Assessing the population-level conservation effects of marine protected areas

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.     

三峡生态屏障区农户退耕受偿意愿的调查分析

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.     

基于优先度的城市避难场所最优投资规划

由于地质条件、人口密度、救灾可达性和灾害风险等不同，需要对城市各个区域避难场所的投资建设进行优先度排序。如何利用有限资金既能保证优先投资区域的避难容量达到规定目标，又能实现整个城市防灾避难规模的最大化，是城市防灾规划建设的重要问题。运用最优化计算理论，给出了基于优先度的最优投资双层规划模型，并举例验证了该模型的可行性。     

数控机床的故障诊断

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。     

浅谈安全工程专业学历教育

从安全工程师应具备的知识结构出发，主要讨论了安全工程专业学历教育中的课程设置及办学过程中存在的一些的问题。     

广州市供水水源面临的问题和对策

通过分析广州市现有的水资源情况和饮用水的供水情况、地表水源和地下水水源概况等资料,针对广州市饮用水源面临的严峻形势,提出广州市应建设以地下水作为应急饮用水源,构建复合水源体系的规划。     

Land-use choices: the case of conservation reserve program (CRP) re-enrollment in Kansas,USA

Among the important alternatives for land conservation is the US Conservation Reserve Program (CRP) that celebrated its 30th anniversary in 2015. This paper explores how landowners decide on alternative land-use choices made available by the expiration of CRP contracts in Kansas. The study uses survey data and multinomial Logit models to predict land-use choices. Two models were tested. The first model does not incorporate variables concerning farmer perceptions and attitudes about land-use choices, while the second model does. The results show that CRP re-enrollment depends on factors, such as years of experience in cropping and percent of cropland irrigated. However, when perception variables are added, the models become more robust in explaining other land choice alternatives. The results suggest that as the perception of unfairness of more inflexible environmental policy rises, these farmers may be more likely to re-enroll their marginal land in the CRP program.     

基于作业成本管理在建筑企业施工中的应用研究

以作业成本管理理论为基础,研究了建筑施工企业的作业成本核算以及计算模型,通过对作业成本管理应用和导入作业成本管理理论与方案设计的分析,比较了施工企业与项目管理作业.结果表明,其作业成本管理模式完全适用于建筑施工企业作业成本的管理,并能够有效地对建筑施工企业的作业成本进行有效控制.图1,参5.     

层次分析法在生活垃圾处置方案优选中的应用

对于如城市生活垃圾处置技术方案优选这类多目标、多方案决策问题,特别是在决策缺乏充分的信息支持前提时,AHP分析法的若干特点,显示其作为一种系统工程的理论工具具有一定的客观性、准确性和有效性,是一种简易而且可行的理论方法和手段。通过以某经济开发区生活垃圾处置方案的优选为例进行了探讨。