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111.
采用大涡模拟(LES)对气体羽流分层特性进行数值模拟,分析了基于LES的气体羽流模型、控制方程和数值计算方法,探讨了LES在多组分气体羽流模拟中的应用;以文献[1]中氦气在空气中形成羽流的实验数据为参考,对所建模型进行验证。利用该模型对密闭空间油气泄漏过程进行数值模拟,计算结果表明油气在泄漏发生的240 s之内,不同组分表现出显著不同的分层规律:相对于空气,密度较大的组分聚集在空间下部20%的范围内;密度较小的组分主要分散在空间上部80%的范围内。研究结果为油库油气危险源安全监测与预警、火灾预防与扑救等提供了关键参数参考和工程设计理论依据。 相似文献
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Natural resources have been blamed for inducing slow growth and sparking civil conflicts and violence. This paper first develops a model to account for the hazard of armed civil conflicts as a manifestation of the natural resource curse, which is mediated by the quality of both economic and political institutions. We then use recently published data on institutional quality and natural resource rents to measure the potential impact of the resource curse on violent civil conflicts using a panel of data for over 100 countries in the period 1970–2010. Our model explicitly accounts for the role of good economic and political institutions in deterring the recourse to violence as well as the extent to which they might weaken the resource rents effect. 相似文献
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The dependence on oil, gas, and mineral exports arguably has a negative impact on economic growth in resource-rich, developing countries. This article looks at the impact of resource dependence on adjusted net savings (ANS) as an indicator of weak sustainability. Our results, based on a panel of 104 developing countries during the recent commodity price boom, confirm a negative relationship between resource extraction and sustainable development as measured by ANS. We further look at the specific role of armed conflict and armed violence as captured by the homicide rate. Armed conflict, which is positively associated with resource dependence, negatively affects ANS per capita according to both our OLS and instrumental variables (IV) estimates. Similarly, armed violence has a detrimental effect on sustainable development. Our IV estimate suggests that a one-point increase in the homicide rate decreases ANS per capita by $60. Since education expenditures are a critical ANS component, we further examine the impact of resource dependence and violence on human capital. Consistent with previous findings, resource-dependent countries underinvest in education but armed conflict and violence do not affect the instantaneous share of education expenditures, hinting at a detrimental effect working through physical and social capital rather than education. 相似文献
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Raphael D. Marcus 《战略研究杂志》2015,38(4):500-528
This article highlights a pattern of military adaptation and tactical problem-solving utilized by the Israel Defense Forces (IDF) while engaged in protracted conflict with the Lebanese militant group Hizballah. It discusses the IDF’s recent attempts to institutionalize their historically intuitive process of ad-hoc learning by developing a formal tactical-level mechanism for ‘knowledge management’. The diffusion of this battlefield lesson-learning system that originated at lower-levels of the organization is examined, as well as its implementation and effectiveness during the 2006 Lebanon War. A nuanced analysis of IDF adaptation illustrates the dynamic interplay between both ‘top-down’ and ‘bottom-up’ processes of military innovation. 相似文献
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对二次检测立方攻击预处理阶段的提取二次表达式的算法进行了改进以优化攻击效率。将秘密变量的变化引入攻击中,使得攻击模型更加灵活;同时,利用时空折中的思想,通过存储常数项和一次项的计算结果,有效降低二次项的计算量。将改进的方法应用于简化版的PRESENT算法和Trivium算法上,攻击效率有显著提高。 相似文献
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