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81.
82.
Monte L Periañez R Boyer P Smith JT Brittain JE 《Journal of environmental radioactivity》2009,100(9):779-784
This paper is aimed at presenting and discussing the methodologies implemented in state-of-the-art models for predicting the physical processes of radionuclide migration through the aquatic environment, including transport due to water currents, diffusion, settling and re-suspension. Models are briefly described, model parameter values reviewed and values recommended. The different modelling approaches are briefly classified and the advantages and disadvantages of the various model approaches and methodologies are assessed. 相似文献
83.
江苏省高宝湖区湖泊群富营养化特征分析 总被引:2,自引:0,他引:2
对江苏省高宝湖区高邮湖、宝应湖、邵伯湖和白马湖湖泊富营养化共性与差异性特征进行了分析。结果表明,2009—2014年,4个湖泊总体处于中营养—轻度富营养之间,综合富营养状态指数值在年内均呈波动变化,丰水期明显大于枯水期;主要营养因子水平在4个湖泊之间均存在较明显的差异,尤其是TN和SD 2项指标阶梯状差异较为明显,Chl-a也呈现不同程度的年内分布水平差异,并在春、夏季存在藻类暴发风险;各湖泊Chl-a与环境因子相关性差异较大,宝应湖、白马湖以及总体分析的高宝湖群Chl-a均与水温、TP相关性显著,TP应是高宝湖群藻类生长限制的主导营养因子;各湖泊富营养化特征存在差异性,总体上宝应湖与白马湖富营养化特征较为类似,与高邮湖差异较大,邵伯湖富营养化特征与高邮湖接近,又兼有与宝应湖、白马湖相似性特征。 相似文献
84.
85.
污染模型中不确定参数的精确订正对于提高模型的精度有着重要的意义。在集合Kalman滤波(EnKF)同化方法的基础上,提出了对模型中不确定参数进行订正的EnKF扩展状态变量法,将不确定参数看成和模型状态变量一样的量,根据观测资料对不确定变量进行订正,以达到订正参数的目的。采用一个简化的空气质量方程,对模型参数订正方案进行检验,结果证明,提出的方案可行和有效。同时发现,随着观测资料精度的提高,无论是参数还是模型的状态变量,估计分析值的精度也得到相应的提高。 相似文献
86.
87.
系统安全相似分析法是发掘共性事故致因,运用逻辑学和数学方法解决安全问题的方法。通过评价比较分析法、比较安全法、模糊相似分析法与系统相似分析法的优缺点,采用多隶属模糊集对系统相似分析法进行改进,克服其无法度量模糊因素相似性的缺陷,得到适用于模糊系统的系统安全相似分析法。基于此,建立系统安全相似度计算数学模型,并构建系统安全相似分析范式。将改进的分析方法应用于4起典型煤矿瓦斯爆炸事故,分析得出,越界开采、井下密闭作业、应急救援不力、密不上报、拒不撤出作业人员等是造成瓦斯爆炸事故严重程度升级的主要因素;物质流、能量流、信息流相似度接近于1,然而其对造成事故的潜在影响受到忽视,是煤矿避免瓦斯爆炸事故的极佳着手点。结果表明,这一改进有效实现了事故致因因素的相似性度量,为系统安全分析与事故预防提供了新思路与新方法。 相似文献
88.
Fault tree analysis (FTA) is an important method to analyze the failure causes of engineering systems and evaluate their safety and reliability. In practical application, the probabilities of bottom events in FTA are usually estimated according to the opinions of experts or engineers because it is difficult to obtain sufficient probability data of bottom events in fault tree. However, in many cases, there are many experts with different opinions or different forms of opinions. How to reasonably aggregate expert opinions is a challenge for the engineering application of fault tree method. In this study, a fuzzy fault tree analysis approach based on similarity aggregation method (SAM-FFTA) has been proposed. This method combines SAM with fuzzy set theory and can handled comprehensively diverse forms of opinions of different experts to obtain the probabilities of bottom events in fault tree. Finally, for verifying the applicability and flexibility of the proposed method, a natural gas spherical storage tank with a volume of 10,000 m3 was analyzed, and the importance of each bottom event was determined. The results show that flame, lightning spark, electrostatic spark, impact spark, mechanical breakdown and deformation/breakage have the most significant influence on the explosion of the natural gas spherical storage tank. 相似文献
89.
阐述了利用遗传算法优化污染损害指数评价模型中参数时的优点和不足,提出采用普适质数公式对污染损害指数评价模型中参数进行线性优化时,可以大幅简化优化过程,便于实际应用.将适用于大气质量评价的普适指数公式与通过GA优化的评价结果进行比对,证实了该公式在线性优化中的可行性. 相似文献
90.
A performance comparison between nonlinear similarity functions in bulk parameterization for very stable conditions 总被引:1,自引:0,他引:1
Three sets of nonlinear similarity functions for strong stability are selected to compare their performance in bulk parameterization.
To uncover their advantages and disadvantages, theoretical and measurement analyses are made with four profile metrics and
the Deacon number technique. Main disadvantages include the negligence of the different transfer efficiency between momentum
and heat, the flux cutoff due to the upper limit in gradient Richardson number (Ri) and the ignorance of limited stability range where the dimensionless gradient functions ( and ) approach constants. Accordingly, three suggestions are made for future improvement. First, the functions for wind velocity
and potential temperature should have the same function form, but with different coefficients. Second, and should approach constants only within a certain stability range. Third, the limit value in Ri should be avoided to widen their applicability in flux modeling. Furthermore, quantitative comparisons in transfer coefficients
for moment and sensible heat (C
D and C
H) are made among the similarity functions in the bulk Richardson number (Ri
B) range 0 < Ri
B < 1. Generally, significant discrepancy is found, which may approach a factor of two and three at large Ri
B in C
D and C
H, respectively. Finally, a new recommendation is made to one of the three sets, mainly because of its ability to predict C
D and C
H that decrease rather slowly in very stable conditions. 相似文献