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31.
汶川地震在江苏的强震动记录及地震影响场   总被引:1,自引:0,他引:1  
2008年5月12日四川汶川发生M8.0大地震,江苏数字强震动台网固定观测台站、宿迁和溧阳断层观测存放台阵共获取该次地震有效强震动事件45个,计134条加速度记录。本文介绍了这些强震动记录分析处理的基本情况及其时域与频域的一些特点;编写SICalculate谱烈度计算程序和D2InterP二维插值程序,输入所获取的汶川地震26组实测强震动记录数据,得到该次地震在江苏地区的峰值加速度与谱烈度的等值线图,并就区域内地震影响场特征进行了初步研究。  相似文献   
32.
Abstract: Conservation and restoration goals are often defined by historical baseline conditions that occurred prior to a particular period of human disturbance, such as European settlement in North America. Nevertheless, if ecosystems were heavily influenced by native peoples prior to European settlement, conservation efforts may require active management rather than simple removal of or reductions in recent forms of disturbance. We used pre‐European settlement land survey records (1859–1874) and contemporary vegetation surveys to assess changes over the past 150 years in tree species and habitat composition, forest density, and tree size structure on southern Vancouver Island and Saltspring Island, British Columbia, Canada. Several lines of evidence support the hypothesis that frequent historical burning by native peoples, and subsequent fire suppression, have played dominant roles in shaping this landscape. First, the relative frequency of fire‐sensitive species (e.g., cedar [Thuja plicata]) has increased, whereas fire‐tolerant species (e.g., Douglas‐fir [Pseudotsuga menziesii]) have decreased. Tree density has increased 2‐fold, and the proportion of the landscape in forest has greatly increased at the expense of open habitats (plains, savannas), which today contain most of the region's threatened species. Finally, the frequency distribution of tree size has shifted from unimodal to monotonically decreasing, which suggests removal of an important barrier to tree recruitment. In addition, although most of the open habitats are associated with Garry oak (Quercus garryana) at present, most of the open habitats prior to European settlement were associated with Douglas‐fir, which suggests that the current focus on Garry oak as a flagship for the many rare species in savannas may be misguided. Overall, our results indicate that the maintenance and restoration of open habitats will require active management and that historical records can provide critical guidance to such efforts.  相似文献   
33.
长江中游历来是长江流域水灾最严重的地区,研究历史时期这一地区水灾发生的变化波动并找出其与厄尔尼诺事件的遥相关,将有助于对长江中游水灾发生的预测。对这二个时间序列自1525年以来的数据进行了统计学分析。结果表明,水灾发生的主要周期比厄尔尼诺事件发生的周期要长:后者主要表现为2年和3~4年的振动,而前者的主要周期为2年、8年和40年,其显著性也没有后者明显(但都超过了0.03的置信度)。通过进一步分析历史时期长江中游水灾与厄尔尼诺事件的耦合振动,发现它们之间存在显著的遥相关。结果表明,长江中游水灾对厄尔尼诺现象的响应不仅存在着如许多中国学者相信的短期滞后(如:1年),而且还存在着比较长时间的滞后(最长可达8年)。研究结果同时表明,如果厄尔尼诺事件发生的相距时间愈短,这一时期长江中游水灾响应的滞后时间也愈短,反之亦然。  相似文献   
34.
A key measure of humanity's global impact is by how much it has increased species extinction rates. Familiar statements are that these are 100–1000 times pre‐human or background extinction levels. Estimating recent rates is straightforward, but establishing a background rate for comparison is not. Previous researchers chose an approximate benchmark of 1 extinction per million species per year (E/MSY). We explored disparate lines of evidence that suggest a substantially lower estimate. Fossil data yield direct estimates of extinction rates, but they are temporally coarse, mostly limited to marine hard‐bodied taxa, and generally involve genera not species. Based on these data, typical background loss is 0.01 genera per million genera per year. Molecular phylogenies are available for more taxa and ecosystems, but it is debated whether they can be used to estimate separately speciation and extinction rates. We selected data to address known concerns and used them to determine median extinction estimates from statistical distributions of probable values for terrestrial plants and animals. We then created simulations to explore effects of violating model assumptions. Finally, we compiled estimates of diversification—the difference between speciation and extinction rates for different taxa. Median estimates of extinction rates ranged from 0.023 to 0.135 E/MSY. Simulation results suggested over‐ and under‐estimation of extinction from individual phylogenies partially canceled each other out when large sets of phylogenies were analyzed. There was no evidence for recent and widespread pre‐human overall declines in diversity. This implies that average extinction rates are less than average diversification rates. Median diversification rates were 0.05–0.2 new species per million species per year. On the basis of these results, we concluded that typical rates of background extinction may be closer to 0.1 E/MSY. Thus, current extinction rates are 1,000 times higher than natural background rates of extinction and future rates are likely to be 10,000 times higher. Estimación de la Tasa Normal de Extinción de Especies  相似文献   
35.
本文运用文献计量学方法,对我国环境科学10种主要期刊(1989~1991)年间总计刊载的2584篇文献所著录的全部引文及文献著者进行一次统计调查与分析研究,从中寻找出我国环境科学研究文献引文的一般规律和我国环境科学科研作者队伍的构成及分布现状。  相似文献   
36.
安全绩效研究综述   总被引:1,自引:0,他引:1  
为探明安全绩效的研究方向,加强对安全绩效基础研究,从而为加强企业安全管理工作提供理论保障。从安全绩效的定义和范畴、安全绩效的评估、安全绩效影响因素的实证研究、安全绩效的提升等方面对国内外安全绩效相关研究进行论述和分析。提出以企业组织安全行为与员工安全行为作为研究的切入点;采用定性与定量相结合的方法;研究的重点应为更加注重过程的控制,注重安全行为的引导和安全文化的建设。  相似文献   
37.
周琳    薛宇敬阳    刘希扬   《中国安全生产科学技术》2016,12(10):185-190
组织管理原因是一类重要的事故致因,对其全面了解才能有效预防事故。就组织管理原因对事故的作用机理、定义与内容、事故分析对其研究的现状进行文献综述。通过文献梳理发现,在一维链式事故模型和系统论为基础的事故模型中,组织管理原因对事故作用机理不同,但对事故发生都具有重要作用。现阶段研究中,组织管理原因没有统一的定义和内容,但具有的区别于其他事故致因的特性能得到共识。现阶段常见的事故分析模型对组织管理原因进行定量和定性分析,但仍需继续完善。最后,对组织管理原因的研究方向提出展望。  相似文献   
38.
ABSTRACT

This article aims to list the main sustainable practices developed in the processes of metal forming, casting, heat treatment, welding and electrostatic painting. When analysed the literature about sustainable manufacturing, a predominance of studies about machining is observed and the processes mentioned are few explored in academic studies. The research strategy used to reach the objective was systematic literature review, conducted for each process cited. Many sustainable practices were identified with prominence of better materials use and energy efficiency. The authors of this article believe that the information presented here can be useful for researches in their future studies and for industry professionals interested in improving manufacturing processes.  相似文献   
39.
This paper examines the settlements and embankments of the Yellow River in central China in late imperial China (late fourteenth century to the early twentieth century) through the approach of historical geographical information system. The Yellow River frequently flooded and changed paths in the lower Yellow River area, creating a disaster-prone environment in the populous capital city, Kaifeng in Henan Province. The official policies of constructing embankments in the alluvial fan for the sake of both preventing flood and ensuring canal transportation for grains were important factors in shaping the settlements of the region. Historical data from some counties in Kaifeng Prefecture indicate that people took shelter along the embankments during floods and, as a consequence, villages steadily developed along the embankments. This is in despite official restrictions on the use of the bottomlands along the Yellow River. This historical case not only illustrates the operating modes of official flood prevention strategies in dynastic China, but also shows how archaic settlement patterns and landscapes have shaped the geography of contemporary China.  相似文献   
40.
膜-生物反应器在我国的研究与应用新进展   总被引:28,自引:2,他引:26  
膜-生物反应器(MBR)作为一种污水处理新技术,其研究和应用在我国受到了广泛关注.主要以1995-2006年发表在国内中文期刊上的关于MBR研究与应用的700多篇文献为基础,分析了与MBR构型、应用领域和研究机构等相关的文献数量分布,综述了在MBR新工艺、膜污染及其控制技术和污水处理类别等方面的研究进展,总结了MBR在污水再生利用中的应用概况,指出了未来MBR技术研究的挑战和工业应用的发展方向.  相似文献   
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