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491.
人-机-环境系统工程在井下运输安全中的应用   总被引:6,自引:0,他引:6  
运用人-机-环境系统工程理论,对煤矿井下运输系统中的人、机、环境三大要素及其对运输事故的影响进行分析,尤其是对人为失误的原因及其控制,人的模糊可靠性,运输事故与人的因素的关系,事件树分析,事故树分析,灰色关联分析,模糊聚类分析以及灰色综合评判等进行了深入的研究,提出了相应的控制措施。  相似文献   
492.
建立了以电捕焦油器火灾爆炸为顶上事件的故障树,分析了引发该事件的主要原因,并提出了相应的防范措施和改进措施。  相似文献   
493.
The conversion of landscapes by human activities results in widespread changes in landscape spatial structure. Regardless of the type of land conversion, there appears to be a limited number of common spatial configurations that result from such land transformation processes. Some of these configurations are considered optimal or more desirable than others. Based on pattern geometry, we define ten processes responsible for pattern change: aggregation, attrition, creation, deformation, dissection, enlargement, fragmentation, perforation, shift, and shrinkage. A novelty in this contribution is the inclusion of transformation processes causing expansion of the land cover of interest. Consequently, we propose a decision tree algorithm that enables detection of these processes, based on three parameters that have to be determined before and after the transformation of the landscape: area, perimeter length, and number of patches of the focal landscape class. As an example, the decision tree algorithm is applied to determine the transformation processes of three divergent land cover change scenarios: deciduous woodland degradation in Cadiz Township (Wisconsin, USA) 1831–1950, canopy gap formation in a terra firme rain forest at the Tiputini Biodiversity Station (Amazonian Ecuador) 1997–1998, and forest regrowth in Petersham Township (Massachusetts, USA) 1830–1985. The examples signal the importance of the temporal resolution of the data, since long-term pattern conversions can be subdivided in stadia in which particular pattern components are altered by specific transformation processes.  相似文献   
494.
基于故障树分析的建设工程风险识别系统   总被引:6,自引:0,他引:6  
目前工程风险识别的效率较低,也缺少有效的风险识别方法。通过分析工程特性、风险特点和现有的风险识别方法,提出了在工程风险识别中大规模地引入故障树技术,以实现风险知识共享,提高风险识别和度量的效率。初步构建了以分部分项工程为识别单位,以故障树为主要分析模型,依托信息技术的工程风险识别和度量系统。  相似文献   
495.
针对液体推进剂贮运过程中的泄漏问题进行了研究,运用故障树分析了推进剂泄漏风险,采用三角模糊数算法定量分析了推进剂泄漏的故障率,并提出采用模糊重要度分析的方法--中值法确定了最容易发生泄漏的环节,从而为快速排除泄漏故障提供了技术依据.  相似文献   
496.
The microecosystem approach and an adequate system of quantitative methods have been used to study the relationship between the chorologic changes in the structure and functions of edificator tree stand and other components of the pine (Pinus sylvestris L.) forest cenoecosystems of the Transural and Northern Turgai regions. Significant correlations of the density of pine undergrowth with the litter thickness; of its growth with root competition, stand closeness, and, to a lower degree, photosynthetically active radiation (PAR); and of the numbers of small mammals and groups of soil mesofauna with herbaceous phytomass have been found. The possibility of the synthesis of population-ecological, synecological, and biogeocenological methods has been demonstrated.  相似文献   
497.
三峡库区古大树种资源及其保护对策   总被引:3,自引:0,他引:3  
长江三峡工程库区,蕴藏着丰富的古大树种资源,约有5000余株。作者从中挑选了树龄较大者195株作为库区重点保护对象,并提出相应的保护对策措施。  相似文献   
498.
A transient population outbreak of the Siberian larch casebearer, Coleophora sibiricella Flkv. (Lepidoptera, Coleophoridae), in a protective forest strip and its consequences for the host tree species (Larix sibirica Ledeb.) have been studied for the first time. It has been shown that one-time complete defoliation by this pest and the following infestation by xylophagous insects result in tree death, while the productivity of surviving trees decreases significantly. The results of this study indicate that the Siberian larch casebearer is a major phyllophagous pest of larch and that its populations must be monitored by specialists in forest pathology.  相似文献   
499.
ABSTRACT: Samples from 107 piñon pines (Pinns edulis) at four sites were used to develop a proxy record of annual (June to June) precipitation spanning the 1226 to 2001 AD interval for the Uinta Basin Watershed of northeastern Utah. The reconstruction reveals significant precipitation variability at interannual to decadal scales. Single‐year dry events before the instrumental period tended to be more severe than those after 1900. In general, decadal scale dry events were longer and more severe prior to 1900. In particular, dry events in the late 13th, 16th, and 18th Centuries surpass the magnitude and duration of droughts seen in the Uinta Basin after 1900. The last four decades of the 20th Century also represent one of the wettest periods in the reconstruction. The proxy record indicates that the instrumental record (approximately 1900 to the Present) underestimates the potential frequency and severity of severe, sustained droughts in this area, while over representing the prominence of wet episodes. In the longer record, the empirical probability of any decadal scale drought exceeding the duration of the 1954 through 1964 drought is 94 percent, while the probability for any wet event exceeding the duration of the 1965 through 1999 wet spell is only 1 percent. Hence, estimates of future water availability in the Uinta Basin and forecasts for exports to the Colorado River, based on the 1961 to 1990 and 1971 to 2000 “normal” periods, may be overly optimistic.  相似文献   
500.
核电站搬运核废料起重机的故障树分析   总被引:1,自引:2,他引:1  
目的 :对某核电站用于搬运核废料的桥式起重机进行了故障树分析 ;方法 :以吊物坠落为顶事件而建立了故障树 ,通过故障树特征参数的计算对该事件进行了定性分析和定量分析。根据分析结果 ,确定了该起重机的关键元 (部 )件和薄弱环节 ,提出了降低吊物坠落概率的简便有效措施。  相似文献   
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