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141.
引入钢筋和混凝土的应变率效应,利用有限元分析软件ABAQUS中的显示动力分析模块ABAQUA/Explicit,对钢筋混凝土梁在不同单调加载速率下的受力性能进行了数值模拟.通过比较不同加载速率下的分析结果,探讨了地震作用下的动态荷载对钢筋混凝土梁受力性能的影响.分析结果表明,在动态荷载作用下,钢筋混凝土梁的受力性能有显... 相似文献
142.
为提高海洋油气管道外腐蚀速率预测的精度和效率,建立基于因子分析(FA)和天牛须搜索算法(BAS)的极限学习机(ELM)腐蚀速率预测模型。利用FA对影响因素数据集进行降维处理,确定预测模型的输入变量;建立ELM预测模型,并采用BAS对ELM模型的参数进行优化,避免参数取值随机性对模型预测性能的影响;以实海挂片试验为例,通过建模仿真评价模型的预测性能,并与其他模型进行对比分析。结果表明:FA-BAS-ELM预测模型的平均绝对误差(MAPE)仅为1.92%,决定系数R2高达0.994 9,相比于其他模型,该模型具有更优的预测性能。 相似文献
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A new and simple equation has been presented here for calculation of adsorption and desorption rate constants of Langmuir-Freundlich kinetic equation. The derivation of new equation is on the basis of extension and correction to the geometric method which has been presented by Kuan et al. [Kuan, W.-H., Lo, S.-L., Chang, C.M., Wang, M.K., 2000. A geometric approach to determine adsorption and desorption kinetic constants. Chemosphere 41, 1741-1747] for the kinetics of adsorption/desorption in aqueous solutions. The correction is to consider that the concentration of solute is not constant and changes as adsorption proceeds. The extension is that we applied Langmuir-Freundlich kinetic model instead of Langmuir kinetic model to consider the heterogeneity and therefore it is more applicable to the real systems. For solving Langmuir-Freundlich kinetic model, some geometric methods and also Taylor expansion were used and finally a simple and novel equation was derived (Eq. (20)) for calculation of adsorption rate constant. This new method was named "extended geometric method". The input data of the obtained equation can be simply derived from initial data of adsorption kinetics. Finally the adsorption of methyl orange onto granular activated carbon was carried out at dynamic and equilibrium conditions and the capabilities of extended geometric method were examined by the experimental data. 相似文献
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Spalinger SM von Braun MC Petrosyan V von Lindern IH 《Environmental monitoring and assessment》2007,130(1-3):57-72
House dust has been identified as a major exposure medium for lead (Pb) in children. High levels of Pb in soil and house dust
have been recorded at the Bunker Hill Superfund Site (BHSS) in northern Idaho, an historic mining and smelting district. Soil
and dust remediation at the site was required; however, regional background soil and dust Pb levels had not been well characterized.
The objective of this survey was to determine background house dust Pb levels and to compare those levels with concentrations,
and dust and Pb loading rates measured at the BHSS. Soil and house dust samples were collected in five towns demographically
similar to the BHSS but unaffected by the mining industry. The background concentrations and loading rates were significantly
lower than those observed at the site. House age was a significant factor affecting background soil and house dust Pb concentrations
and loading rates. 相似文献
148.
This paper examines the importance of the correlation between hydraulic conductivity (K) and degradation rate constant (k) during the transport of reactive contaminants in heterogeneous aquifers. We simulated reactive transport in an ensemble of two-dimensional heterogeneous aquifers. Two sets of transport simulations were conducted: one in which a perfect positive correlation was assumed between ln(K) and ln(k), and one in which a perfect negative correlation was assumed. We found that the sign of the correlation has important consequences for the contaminant transport. Qualitatively, a negative correlation leads to significantly more pronounced "fingering" of the contaminant plume than does a positive correlation, with potentially important consequences for downgradient receptors. Quantitatively, the expected behavior (as quantified by the contaminant mass remaining in the aquifer) is statistically different between the positive and negative cases: on average, more contaminant mass persists when K and k are negatively correlated. Also, the negative correlation leads to more variability between realizations of the ensemble, whereas a positive correlation induces relatively little variability between realizations. We discuss the implications of these findings for the management of contaminated aquifers. 相似文献
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Recent models of choosiness in mate choice have identified two particularly important factors: the potential reproductive
rate (PRR) of the choosing sex relative to that of the chosen sex, and the variation in quality of potential mates. This experimental
study tested how these factors affected choosiness in male and female sand gobies, Pomatoschistus minutus. We manipulated relative PRR by means of water temperature, and mate quality by means of body length. The choosing male or
female was offered a choice between two mates with either a small or a large difference in body length representing a small
or a large variation in mate quality. Choosiness was measured as (1) preference for the larger mate, and (2) as whether or
not spawning occurred with the smaller mate, while the larger mate was visible but screened off. We found that females preferred
large males, and that their level of choosiness was affected by variation in male quality, but not by their own relative PRR.
Males, on the other hand, seemed unselective in all treatments and were in general more likely than females to spawn with
their provided partner. This suggests that in the sand goby, variation in male mate quality has a greater influence than relative
PRR on facultative changes in female choosiness. However, a general difference in PRR between males and females may be one
important factor explaining the observed sex difference in choosiness.
Received: 17 April 2000 / Revised: 24 June 2000 / Accepted: 17 July 2000 相似文献