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11.
Chen Bao-ming Zhang Li-qiangDepartment of Air-conditioning Refrigeration Engineering Shandong Institute of Architecture andEngineering Jinan China e-mail:chenbm @ sdai.edu.cnWang Bu-xuanDepartment of Thermal Engineering Tsinghua University Beijing China 《水动力学研究与进展(B辑)》2003,15(6)
The influences of Soret effect and Dufour effect on the natural convection and heat and mass transfer for a porous enclosure were investigated by means of the penalty finite element method. Numerical results indicate that the Soret and Dufour effects have significant influences on heat and mass transfer in the presence of large temperature gradient and concentration gradient. 相似文献
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考虑到企业信息化建设过程中知识转移的能力具有灰色性和模糊性的特点,传统的分析方法具有很大的局限性。本文采用基于信息熵权值的多层次灰色评价理论,对信息化过程中知识转移的能力的多级指标体系进行综合评判,为企业提供决策以及改进的依据,最后给出运用该方法的一个实例。该方法具有较强的实际应用价值。 相似文献
14.
Conditional probability distributions seem to have a bad reputation when it comes to rigorous treatment of conditioning. Technical arguments are published as manipulations of Radon–Nikodym derivatives, although we all secretly perform heuristic calculations using elementary definitions of conditional probabilities. In print, measurability and averaging properties substitute for intuitive ideas about random variables behaving like constants given particular conditioning information.
One way to engage in rigorous, guilt-free manipulation of conditional distributions is to treat them as disintegrating measures—families of probability measures concentrating on the level sets of a conditioning statistic. In this paper we present a little theory and a range of examples—from EM algorithms and the Neyman factorization, through Bayes theory and marginalization paradoxes—to suggest that disintegrations have both intuitive appeal and the rigor needed for many problems in mathematical statistics. 相似文献
One way to engage in rigorous, guilt-free manipulation of conditional distributions is to treat them as disintegrating measures—families of probability measures concentrating on the level sets of a conditioning statistic. In this paper we present a little theory and a range of examples—from EM algorithms and the Neyman factorization, through Bayes theory and marginalization paradoxes—to suggest that disintegrations have both intuitive appeal and the rigor needed for many problems in mathematical statistics. 相似文献
15.
Hall and Miles (1990) suggest an approach of estimating default probabilities of banks using stock market information, and in this paper we apply an aggregated version of their approach to banking sectors around the world in both developed and emerging economies. We study the market’s assessment of the probability of systemic banking crises world wide over the last decade, including the Asian crisis 1997–1998. In addition, we investigate whether there is a relationship between the failure probability and institutional features of the actual banking sector. The quality of governance and the degree of law and order in a country is found to be significantly negatively related to the market based failure probabilities as is an explicit deposit insurance during periods of crisis. 相似文献
16.
LeAnn Southward Hogan Elizabeth Marschall Carol Folt Roy A. Stein 《Journal of Great Lakes research》2007,33(1):46-61
Lake Erie's food web has been dramatically modified by exotic species. Both exotic dreissenid mussels and the round goby Neogobius melanastomus have shifted the food web from a pelagicbased to a benthic-based one, potentially creating a new pathway for contaminant transfer to top predators. Before the invasion of round gobies, few predators of dreissenids occurred in Lake Erie, allowing contaminants to be confined to these benthic organisms. The invasion of the round goby has produced a new pathway through which these contaminants can enter the food web. To characterize heavy-metal transfer through this new food web and to assess risk to humans, water, surficial sediment, dreissenid, round goby, and smallmouth bass Micropterus dolomieui samples were collected at three sites during summers, 2002 and 2003, and analyzed for total lead (Pb), total mercury (Hg), and methyl mercury (MeHg). In addition, we compared smallmouth bass Pb and Hg concentrations to those measured in 1993/1994, before round gobies were prevalent. Pb biodiminished and MeHg biomagnified through the food web to smallmouth bass; patterns were similar among our three sites. Total Pb concentrations in smallmouth bass were higher before the incorporation of round gobies into their diet. We attributed this decline to changes in food web structure, changes in contaminant burdens in prey, or declines in sediment Pb concentrations in Lake Erie. By comparison, Hg concentrations in smallmouth bass changed little, before and after the round goby invasion, possibly due to a shift in diet that increased growth. Despite a decline in sediment Hg concentrations in Lake Erie, smallmouth bass continued to accumulate Hg at historical rates possibly because of their high consumption rates of benthivorous round gobies. As smallmouth bass continue to consume round gobies during their lives, their Hg concentrations may well continue to increase, potentially increasing the risk of Hg contamination to humans. 相似文献
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为合理计算水工钢闸门主梁模糊失效概率,分别将主梁相对变形当作一个随机变量及三个变量的组合,采用积分法、当量随机化方法及蒙特卡罗法进行了计算。当相对变形为一个随机量时,采用积分法及当量随机化方法计算,两者的差别在于积分法用隶属函数描述模糊限值,当量随机化方法是将模糊限值当量作为一个随机量。当相对变形看作三个变量的组合时采用蒙特卡罗法进行计算,该方法考虑了三个变量的分布特性,更符合实际情况,模糊限值也用随机量表示。计算表明,积分法与当量随机化方法结果相近,验证了当量随机化方法的精度;蒙特卡罗法结果与相对变形服从正态分布时、用当量随机化方法计算的结果接近,故主梁相对变形服从正态分布更为合理。三种计算方法中,当量随机化方法计算失效概率相较于其它方法有计算过程简便,效率高的优点。 相似文献
18.
排污权交易(Ernission trading)是一种基于市场(Market-based)的环境政策。本文坚持以科学的发展观,来研究经济发展与环境保护的协调关系,目的是实现环境资源和环境容量的可持续利用。本文分析了企业的排污行为决策,并将环境资源和环境容量的稀缺性纳入排污权交易价格之中。通过价格这个经济杠杆去调节人们对环境资源和环境容量的利用,反映于企业为其排污行为所作的选择,进而论述企业推进排污权交易的可行性。 相似文献
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基于社会网络视角,以2010—2020年中国A股非金融类上市公司为样本,探讨共同分析师网络对于企业异地投资的影响机理及其经济后果。研究发现:共同分析师网络依靠网络中的社会资本及信息传递效应促进企业异地投资,并且这种促进作用在民营企业和第三产业企业中表现得更为明显;经济后果表明,共同分析师网络作用下的异地投资会促进企业创新并提升企业价值,有利于企业健康发展。 相似文献
20.
合成新技术在有机化学实验教学中的应用 总被引:1,自引:0,他引:1
该文设计了一个合成相转移催化剂——苄基三乙基氯化铵的教学实验。同时对有机化学实验教材中己二酸合成实验进行了改进,把合成的相转移催化剂用于己二酸合成反应,反应时间由原来的4—6小时缩短为40分钟,产率由原来的60%提高到78%。该实验满足了基础有机化学实验教学的目的和要求。多轮次的学生实验证明,此项实验教学的改革激发了学生的兴趣,取得了良好的教学效果。 相似文献