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41.
结合涉外企业投入与产出所处市场的分割程度或一体化程度,分析了当地企业、进口企业、出口企业或全球经营企业所面临的货币经营风险;对计量涉外企业货币经营风险的方法进行比较,认为管理层估计法对于计量货币经营风险以及制定相应的竞争对策有着重要作用;分别从金融性套期保值、经营性套期保值和营销策略等视角讨论货币经营风险的管理。笔者认为:金融性套期保值通过锁定涉外企业的外币现金流出或流入,可部分抵消涉外企业的货币经营风险暴露;经营性套期保值通过调整企业的经营业务并尽可能多地增加经营现金流,可从根本上提高涉外企业适应汇率变化的能力;通过影响涉外企业及其竞争对手所处的经营环境,营销策略有助于降低涉外企业的货币经营风险暴露。 相似文献
42.
地铁运营系统安全综合评价指标体系研究 总被引:1,自引:4,他引:1
分析地铁运营系统的特点、运营模式、系统故障模式,并运用系统工程的理论原则,从系统外部因素、系统指挥因素、设备设施因素、运营管理因素4个方面,确立地铁运营系统安全综合评价指标体系,利用模糊数学综合评价法,建立了地铁运营系统安全综合评价模型,并通过典型实例进行综合分析评价,进而证明将模糊数学理论应用于地铁安全综合评价的可行性。通过地铁运营系统安全指标体系和评价方法的研究和探索,对正确评价地铁系统运营安全现状,修正偏差,提高地铁系统安全总体水平具有十分重要的意义。 相似文献
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中国船舶机舱火灾研究现状 总被引:16,自引:1,他引:16
分析了船舶机舱失火的原因和机舱火灾的特点 ,对我国船舶机舱火灾的研究现状进行了综述 ,对机舱火灾的研究前景进行了展望 ,提出了机舱火灾基础研究和应用研究面临的主要课题 ,表达了船舶机舱火灾研究的重要意义。 相似文献
44.
探讨了列车牵引力学条件下的铁路列车安全操纵问题 ,开发了一套可用于不同运行条件下的列车安全操纵仿真软件。重点介绍了系统的主体结构、功能模块以及列车安全操纵的计算模型 ,详细描述了在一个时间步长内如何确定列车的工况、手柄位以及停车制动的仿真算法 ,并在实际线路上对电力机车进行了实例分析。系统计算速度快 ,人工干预方便 ,效果良好 ,可以满足现场的实际需求。 相似文献
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Ton H. Snelder Barry J.F. Biggs Mark A. Weatherhead 《Journal of the American Water Resources Association》2004,40(1):1-13
ABSTRACT: A method is demonstrated for the development of nutrient concentration criteria and large scale assessment of trophic state in environmentally heterogeneous landscapes. The method uses the River Environment Classification (REC) as a spatial framework to partition rivers according to differences in processes that control the accrual and loss of algae biomass. The method is then applied to gravel bed rivers with natural flow regimes that drain hilly watersheds in New Zealand's South Island. An existing model is used to characterize trophic state (in terms of chlorophyll a as a measure of maximum biomass) using nutrient concentration, which controls the rate of biomass accrual, and flood frequency, which controls biomass loss. Variation in flood frequency was partitioned into three classes, and flow data measured at 68 sites was used to show that the classes differ with respect to flood frequency. Variation in nutrient concentration was partitioned at smaller spatial scales by subdivision of higher level classes into seven classes. The median of flood frequency in each of the three higher level classes was used as a control variable in the model to provide spatially explicit nutrient concentration criteria by setting maximum chlorophyll a to reflect a desired trophic state. The median of mean monthly soluble reactive phosphorus and soluble inorganic nitrogen measured at 68 water quality monitoring sites were then used to characterize the trophic state of each of the seven lower level classes. The method models biomass and therefore allows variation in this response variable to provide options for trophic state and the associated nutrient concentrations to achieve these. Thus it is less deterministic than using reference site water quality. The choice from among these options is a sociopolitical decision, which reflects the management objectives rather than purely technical considerations. 相似文献
48.
地铁运营系统危险有害因素辨识分析 总被引:4,自引:4,他引:4
地铁系统发生事故,后果不堪设想。笔者在对国内外63起地铁典型事故分析的基础上,确定了地铁火灾、列车脱轨、拥挤踩踏、中毒窒息、列车撞车等危险有害因素,并对影响事故的后果严重度和发生频率进行了分析,给出了危险度计算查阅赋值表,从而确定了影响地铁运营的危险度,作出了量化分级,同时对可能导致事故的危险有害因素进行了分析,并对危险有害因素的防治对策进行了探讨。 相似文献
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Small body size is generally correlated with r‐selected life‐history traits, including early maturation, short‐generation times, and rapid growth rates, that result in high population turnover and a reduced risk of extinction. Unlike other classes of vertebrates, however, small freshwater fishes appear to have an equal or greater risk of extinction than large fishes. We explored whether particular traits explain the International Union for Conservation of Nature (IUCN) Red List conservation status of small‐bodied freshwater fishes from 4 temperate river basins: Murray‐Darling, Australia; Danube, Europe; Mississippi‐Missouri, North America; and the Rio Grande, North America. Twenty‐three ecological and life‐history traits were collated for all 171 freshwater fishes of ≤120 mm total length. We used generalized linear mixed‐effects models to assess which combination of the 23 traits best explained whether a species was threatened or not threatened. We used the best models to predict the probability of 29 unclassified species being listed as threatened. With and without controlling for phylogeny at the family level, small body size—among small‐bodied species—was the most influential trait correlated with threatened species listings. The k‐folds cross‐validation demonstrated that body size and a random effect structure that included family predicted the threat status with an accuracy of 78% (SE 0.5). We identified 10 species likely to be threatened that are not listed as such on the IUCN Red List. Small body size is not a trait that provides universal resistance to extinction, particularly for vertebrates inhabiting environments affected by extreme habitat loss and fragmentation. We hypothesize that this is because small‐bodied species have smaller home ranges, lower dispersal capabilities, and heightened ecological specialization relative to larger vertebrates. Trait data and further model development are needed to predict the IUCN conservation status of the over 11,000 unclassified freshwater fishes, especially those under threat from proposed dam construction in the world's most biodiverse river basins. 相似文献