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231.
M. de Vries G. J. Klaassen N. Struiksma Professor Delft University of Technology. The Netherlands. Delft Hydraulics. The Netherlands. 《国际泥沙研究》1990,(1)
I. INTRODUCTIONMore than a decade ago, under tile auspices of DELFT HYDRAULICS an overview on the use ofmodels for river problems was given (de Vries & van der Zwaard. 1975). Since then a better understanding of morphological processes in rivers has been obtained, their mathematical formulation hasbeen improved and computer facilities have been expended. Scale models and mathematical models arein use. but their field of application is gradually changing. It seems that the better ma… 相似文献
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在科拉半岛和北乌拉尔的碱性岩中近来发现了五种新矿物.莫斯科大学结晶学系在近三年的时间里测定了这些矿物的结构.本篇评论概述了这些矿物的结构测定结果.Grumantite(Na[Si_2O_4(OH)].H_2O),产于Lovezero碱性岩块,其结构中存在一种新型的间断骨架,这种骨架是四面体络合基(T_2O_5)的非典型的结构形式.它的形式与(OH)-基的存在有关,羟基使得每个配位四面体内的平均负电荷减少.Clinobehoite[Be(OH)_2],产于北乌拉尔的脱硅伟晶岩内,与其他Be矿物:硅铍钙石、锂铍脆云母及富铁高岭石共生.它的结构由三层Be四面体层组成的结构单元层之间以氢键相连而构成.在Clinobehoite的红外光谱中明确地揭示出不同类型的氢键的存在. 相似文献
235.
This article identifies some issues of importance in understanding China's policy of population control. This article presents evidence of trends in fertility, population policy, family planning, and socioeconomic change; and then discusses the conflict between fertility preferences and policy that is evident from studies of ideal family size and sex ratios. Some issues that are identified as "uncertain" include the extent of spread of family planning service delivery and its associated insurance schemes, local family planning policies and cadre responsibility systems, the demand for children, the demand for female children, the economic and environmental consequences of population growth, the fairness of reproductive restrictions and their application, and the extent of coercion in the later-longer-fewer policy era. It is argued that an ethical framework for analyzing China's population policy should include answers to questions about the harm to welfare from population growth, the government's right to demand voluntary reproductive sacrifice or to impose demographic or reproductive restrictions and punishment, and the government's right to impose coercion. If it is accepted that population growth in China has adverse consequences and its control would be beneficial to all, then it must be determined what the nature of the relationship should be between the state and the individual. The author refers to Walzer's (1983) position that the legitimacy of Chinese state power depends in part on whether political leaders at all levels are competent and not corrupt. The rights and duties of the government and individuals must be understood not just in terms of political legitimacy but also in terms of social justice. Social justice is dependent upon the degree of horizontal and vertical consultation and accountability, utilitarian consequences, and protected spheres of individual judgement. Utilitarian theories justify the one-child policy, while deontological theories support reproductive freedom as an absolute right. 相似文献
236.
Presence of the outer perforated cylinder reduces the direct wave impact on the inner cylinder, which has been testified by many researchers. However, the force reduction mechanism, which is complicated due to the wave-porous structure interaction, needs to be addressed in detail. The present study explains the mechanism with the aid of the computational fluid dynamics (CFD) tool STAR CCM+. This package is chosen for its capabilities to simulate viscous and turbulence effects caused by passage of waves. For the present study, flow fields around the twin cylinders with different orientations are examined with and without the outer perforated cover. Mechanism contributing to the reduction of force on the existing structure is explained in physical terms, and force reduction is quantified. The present study has direct application in the retrofitting application of offshore members. 相似文献
237.
Post‐ore Modification and Preservation of the Indosinian Porphyry Copper Deposit in Geza Arc,Yunnan, SW China 总被引:1,自引:0,他引:1
正Objective The post-ore modification and preservation of porphyry copper deposits is controlled and influenced by various geological processes,and the regional uplift and denudation is the most important factors.This study used 相似文献
238.
正Occurrence of mafic dykes in Himalaya has been intriguing and debated since long because of its difficulty to ascent and emplacement through a thickened crust.Mafic dykes in Kumaun Lesser Himalaya(KLH)of central Indian 相似文献
239.
正 INTRODUCTION The term Tsinling is used here in its broadest sense, which is even broader than that defined by Chao and Huang. It includes the Tapashan and is a general region in which are situated the catchment areas and the headwaters of the Wei, the Han 相似文献
240.