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181.
182.
EFFECT OF PLANETARY AND SYNOPTIC SCALE WAVES IN MAINTAINING MERIDIONAL CIRCULATIONS AT MID AND LOW LATITUDES*
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Following Wu and Chen(1989), in terms of the elliptical differential equation with mean meridional stream function, an equation similar in form to that developed by Kuo(1956) and by use of time average statistics of atmospheric circulation in wavenumber domains at the same intervals of time, a study is made of the contribution of the internal forcing of the atmosphere in two space scales to mean meridional circulation. Results show that planetary waves have considerable influence on the intensity of the upper center of the bi-Hadley cell, and, in contrast, synoptic-scale waves exert vital effect on the Ferrel cell, and that in the Northern Hamisphere(NH) such internal forcings by planetary- and synoptic-scale waves are comparable on mean meridional circulations whereas the latter contribute far more than the former in the Southern Hemisphere(SH).Further, in the northern winter(summer) the contribution of heat(angular momentum) transport of planetary waves allows the descending(ascending) branch to occur as far as around 40°N, some kind of effect that makes quite important contribution to the winter(summer) monsoon circulation in eastern Asia. 相似文献
183.
Pu Wang R. Kahawita Professor of Mechanics Lenzhou University Lanzhou China. Professor of Civil Ensineering Ecole Polytechnique de Montreal Canada. 《国际泥沙研究》1990,(1)
I. INTRODUCTIONNumerical models of estuaries incorporating simulation of the density induced circulation are consideredimPOrtant tools in the assessment of their dispersive characteristics. Most models to date have used finite difference approximations to the governing equations (see for example thericke and Hogan, 1977, Blumberg,1 977, Perrels and Karelse, 1978). A numeriCal model of estuarine circulation using a SADI (Spline Alternating Direction implicit) procedure together with a… 相似文献
184.
185.
针对地形模型随视点简化时,容易引起边界的变化,使得地物模型与地形模型简化过程中产生"裂缝"或翻转现象的问题,文章提出一种改进方法:在对三维地形和地物进行集成后,采用递进格网表示方法并在边折叠过程中采用条件约束对其简化;在边排序的基础上,根据顶点重要度进行排序。该方法优点是计算时间短,且权值定义能够很好地反映局部几何特征,能够保持三维地形、地物模型边界原始信息和格网三角面的基本方向,并消除集成模型之间的"裂缝"或悬空现象。最后通过对整个三维场景进行动态实时绘制,证明该方法具有良好的可视化效果。 相似文献
186.
187.
Chen Tieyun Liu Pu Wang Deyu Professor Shanghai Jiaotong University Shanghai . Postdoctor Shanghai Jiaotong University Shanghai 《中国海洋工程》1994,(3)
-A ring model is developed to investigate the ultimate strength of tubular X and XX joints in the case that the brace is compressed. In the present analysis, the tubular joint is made of elasto-perfectly-plastic material, and the arch element of the chord section intersecting with the brace is assumed to be rigid. It is found that when 6 plastic hinges for X joint and 8 plastic hinges Tor XX joint appear in the ring, the limit state is reached, and by means of the equivalent ring width Be formula proposed in a previous paper by the authors, the ultimate strength of tubular X and XX joints subjected to compression can be obtained. 相似文献
188.
海带类的工业利用在国外从17世纪末就开始,19世纪中叶起陆续出现了一些综合利用的方法。近20年来在这方面进行研究工作较多的国家有日本、英国、苏联等。
近几年来,我国由于大力开展了海带的人工养殖,产量猛增,为工业利用提供了必要的基础。我们在研究了海带综合利用中的两个关键性问题一一原料处理和主产品褐藻酸的提取条件——之后,接着开始了综合利用方法的研究。
国外所研究的海带综合利用要点和缺点大致是: 1. 从同一份海带中综合考虑的产品大多是褐藻酸、碘和甘露醇,而很少同时考虑氯化鉀、褐藻淀粉等其他产品; 2. 水溶性成分是用稀酸提取,这不仅消耗酸和中和用碱,而且对褐藻酸会带来很不利的影响; 3. 甘露醇和碘的分离也各有不同:高桥等推荐用铜沉淀法;英国则直接用酒精从海藻中提取甘露醇,或从稀酸提取液中加有机药品制成水不溶性甘露醇衍生物。前者所需铜盐量相当大,且对于氯化鉀、褐藻淀粉的分离研究不利;后者直接以酒精煮沸海藻,必将显著减低褐藻酸粘度,而水不溶性甘露醇沉淀的制备则成本太高,无多大实用价值。
我们认为,要寻求一个较全面、合理、轻济、简易的综合利用流程,首先应考虑: 1. 各种成分如褐藻酸、甘露醇、碘、氯化鉀、褐藻淀粉等的全面利用的流程; 2. 以水代替稀酸作提取剂;同时确定各种产品的适宜分离条件等。
综合利用流程的初步轮廓和结果已于1959年初提出。其后至1960年初这段时间内,我们对于各产品的分离条件和在各步骤中的产率等方面作了比较系统的进一步实验,并且对于先前提出的流程作了部分修正、补充。 相似文献
189.
-The formulation of ring analogy method for the prediction of static strength (ductile collapse) of tubular T, X joints under axial compression based on the limit analysis of the ring with some assumptions is presented in this papaer. The regression formula for the effective length of the chord based on test results is established by means of the least square method. The results computed by the present semi-analytic formula are compared with previous results and test data. They are quite close to each other. The accuracy of the present formula depends on the reasonable selection of the effective length of the chord, which requires numerous test data. 相似文献
190.
Hong-Jian Liao Li-Jun Su Wu-Chuan Pu Jian-Hua Yin 《Marine Georesources & Geotechnology》2003,21(3):183-200
A kind of diatomaceous soft rock and its constitutive model are studied in this article. Based on Yin and Graham's (1999) 3-D elastic viscoplastic constitutive model, the formulation under a triaxial stress state is established, and it is used to simulate the time-dependent stress-strain behavior and effective stress path of consolidated undrained triaxial tests of both normally consolidated and overconsolidated soft rock. The comparison between the model predictions and measured results shows that their agreement is good. This demonstrates that the constitutive equation established here can be used to simulate the time-dependent stress-strain behavior of the soft rock under triaxial stress condition. 相似文献