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991.
以NewVST塔板为基础,提出了一个计算喷射工况下塔板效率的二维传质-混合池模型,它可以通过单池液体提升量、池间液体交换分率及液体循环分率等模型参数的变化对塔板上液体的沟流、纵向返混和横向混合等现象给予体现与模拟,应用于NewVST塔板得到了满意结果. 相似文献
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994.
We present a contribution to the current debate on whether it is more appropriate to fit a Gumbel distribution to the time series of the extreme dynamic pressures (i.e. of the squares of the extreme wind speeds) than to fit an extreme value distribution to the time series of the extreme wind speeds themselves. It has been shown that the use of time series of the extreme dynamic pressures would be justified if the time series of the wind speed data taken at small intervals (e.g. 1 h) were, at least approximately, Rayleigh-distributed. We show that, according to sets of data we believe are typical, this is not the case. In addition, we show results of probability plot correlation coefficient (PPCC) analyses of 100 records of sample size 23 to 54, according to which the fit of reverse Weibull distributions to largest yearly wind speeds is considerably better than the fit of Gumbel distributions to the corresponding largest yearly dynamic pressures. We interpret the data and results presented in the paper as indicating that there is no convincing support to date for the hypothesis that the Gumbel distribution should be used as a model of extreme dynamic pressures. 相似文献
995.
Our visual landscape: Managing the landscape under special consideration of visual aspects 总被引:1,自引:0,他引:1
Comprehensive landscape valuation requires an integration of ecological, economical and social values. Landscape image does not only comprise its spatial and structural parts but also the formal visual and cultural aesthetic expression of the landscape. In accordance with this holistic image of the landscape the manifestation of these special elements and visual functions is reflective of the natural and cultural coherence and beauty of long functioning natural and cultivated landscape systems.Landscape image and identity on the one hand and its natural or cultural variety (singular appearances of elements, local peculiarities or particulars) on the other hand are the most important criteria for evaluation, classifying and protecting against possible impacts on the local and regional landscape.However, in addition to the desirability of preserving existing landscape identity, the protection of existing elements, space and functions should not blindly rule out the possibility of new developments emerging with new values.Based on this basic idea value ranking of landscape features and individual expression of partial image sectors can be performed on the level of ecological and sustainable land use and planning culture. In landscape planning it is recognised that such a ranking requires a combination with professional judgement, informed opinion and public preferences as well.To ensure the aims of preservation and development of a high-quality nature and culture beauty special methods of analysis and demonstration of the landscape structure and image are requested. The demonstrated methodical steps should correspond to the objective of a sustainable nature and landscape preservation and development on an aesthetic landscape planning level with guidelines and helpful data for the impact assessment and intervention rule (German nature conservation act). 相似文献
996.
Parametric study on flutter derivatives of bridge decks 总被引:6,自引:0,他引:6
The method for identification of flutter derivatives of bridge decks developed by the authors is first briefly described in this paper. To investigate the effects of dynamic parameters of a bridge deck model on the flutter derivatives a test of the sectional Jiangyin Bridge deck's models with different dynamic parameters was carried out in a boundary layer wind tunnel using the present identification method. In both smooth and simulated turbulent flow conditions, a plate model and the sectional deck model of the Jiangyin Bridge were tested to further survey the effects of turbulence on flutter derivatives. The identified results tend to indicate that the effects of parameters of the model and turbulence on the flutter derivatives are negligible. 相似文献
997.
The crystallization kinetics of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) (PET/PEN) blends were investigated by DSC as functions of crystallization temperature, blend composition, and PET and PEN source. Isothermal crystallization kinetics were evaluated in terms of the Avrami equation. The Avrami exponent (n) is different for PET, PEN, and the blends, indicating different crystallization mechanisms occurring in blends than those in pure PET and PEN. Activation energies of crystallization were calculated from the rate constants, using an Arrhenius‐type expression. Regime theory was used to elucidate the crystallization course of PET/PEN blends as well as that of unblended PET and PEN. The transition from regime II to regime III was clearly observed for each blend sample as the crystallization temperature was decreased. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 23–37, 2001 相似文献
998.
从不确定性量化的角度将风电出力的斜坡事件发生概率转化为一个数据驱动的鲁棒概率不等式,该不等式提供一个随机变量的概率,且其概率分布属于给定的多面体.为了解决风电输出的分布不确定性问题,考虑由可用数据构造的模糊集合中的候选分布集合,其最低要求是要包括预测值和平均绝对偏差.基于矩的模糊集由所有概率分布组成,共享相同的平均和平... 相似文献
999.
1000.
风偏角与杆塔结构对500 kV同杆双回线路绕击耐雷性能的影响 总被引:1,自引:0,他引:1
分析500kV双回输电线路的绕击耐雷性能,对EGM进行了改进。在计算过程中为考虑风的影响,引入风偏角;同时引入了雷击避雷线与雷击地面击穿强度比值随杆塔高度h变化的系数β。用暴露弧法计算每根导线绕击跳闸率,以暴露弧为0时对应的雷电流作为雷电的最大绕击电流,并分析了风偏角、杆塔结构等因素对500kV双回输电线路各导线绕击跳闸率的影响。结果表明,风偏角增大,绕击跳闸率增大;总绕击跳闸率随避雷线横担增长而减小;各导线绕击跳闸率与杆塔结构间的关系复杂,需具体计算分析。理论分析和计算验证了该方法的实用性和有效性,具有一定的工程指导意义。 相似文献