错列圆柱表面周向压力分布的试验研究

研究了正三角形排列的3排错列圆柱受到气液两相流横向冲刷时的表面周向时均压力和脉动压力的分布特性,讨论了含气率对圆柱表面时均压力系数和脉动压力系数的影响．气液两相流的流型为细泡状流,两相隙缝流雷诺数的范围为2.0×10     

气液两相流诱发顺列双圆柱升力功率谱特性研究

两相流诱发管束振动的研究尚处于起步阶段,研究气液两相流中串联双圆柱的诱发振动特性,有助于理解管束中管子之间相互影响机理,对于进一步研究复杂管束中的流体诱发振动现象具有重要意义,为此对受到垂直向上气液两相流横向冲刷的顺列双圆柱所受的升力进行了实验研究．实验中来流雷诺数的范围为１．６×１０４～８×１０４,截面含气率的范围为０～０．３０,管间距比Ｌ／Ｄ等于２．０、３．０、４．０．实验结果表明：在一定的试验范围内,在含气率小于０．１５的情况下,当管间距比等于４．０时,每个圆柱的脉动升力功率谱图都存在峰值,而管间距比等于２．０、３．０时,只有后面的圆柱升力功率谱图上有峰值;当含气率大于０．１５时,两根圆柱脉动升力功率谱图的峰值消失;雷诺数对功率谱特性的影响相对较小．     

气液两相流中错列管束上脉动升力的试验研究

采用电阻应变仪和脉动升力测量装置,在气液两相流横向冲刷三排错列排列的管束时,对其受到的脉动升力做了试验研究,测试管采用φ３０ｍｍ的有机玻璃圆柱,气流两相流的流型为细胞状流;上隙流雷诺数的范围为２．０＊１０＾４－６．０＊１０＾４;截面含气率的范围在０－０．３０,试验发现,在横向节径比小于２．０时,脉动升力系数的最大值发生在首排圆柱上,而在大于２．０时,则转移到最后一排圆柱上;脉动升力系数随含气率和雷     

气液两相流中错列圆柱上旋涡脱落规律的试验研究

通过试验,对气液两相流中相同直径的3排错列圆柱表面上旋涡的脱落与节径比、含气率的关系进行了研究,研究发现：旋涡的周期性脱落仅在含气率α小于等于0.14的范围内发生;对于横向节径比s1/d小于等于2.0的错列圆柱,隙缝流呈现双稳态的偏斜流,而横向节径比s1/d大于2.0时,双稳态的偏斜流消失;两相流斯特拉赫数随含气率的增加而减小。     

气液两相流中压力波传播的实验研究

在含气率为0-0.7 m/s,折算液速为0-1.5 m/s范围内实验研究了气液两相泡状流和弹状流中压力波的传播.利用压力信号分析了气液两相流中压力波传播的速度和衰减特性,证明气液两相流中压力波的传播具有色散特性,其传播速度和衰减系数受含气率和扰动角频率的影响很大,而工质的折算速度对压力波的传播几乎没影响.     

矩形管道内低雷诺数圆柱绕流尾迹演化特性

为了揭示有限管道壁面对圆柱绕流尾迹演化特性的影响,采用基于有限容积法的数值模拟方法,对矩形管道内雷诺数为100的三维圆柱绕流尾迹流场进行计算分析,探讨阻流比和长径比对圆柱表面和尾迹流场中压力分布的影响。研究结果表明:圆柱前、后驻点的压力系数受展向位置影响较大,后驻点压力系数与旋涡脱落状态有关;时均压力系数受管道端壁影响显著,沿前驻点至后驻点圆柱表面时均压力系数先减小后增大;在远离端壁一定区域内,尾迹流态为涡街;而在靠近端壁的一定区域内,尾迹呈现出近似双子涡形态;圆柱表面相同位置处的时均压力系数基本上随阻流比的增大而增大,随长径比的增大而减小。     

脉动流条件下的圆柱绕流特性研究

为探究脉动流对流体绕流结构物产生的影响,采用数值方法研究了脉动流条件下圆柱绕流场特性,对涡量分布、升阻力系数、升力系数频谱特性等进行分析。结果表明:脉动流作用会使圆柱尾涡剪切层变薄,提高脉动频率使尾涡长度变短、脱离加快,提高无量纲脉动振幅使主导涡的脱落速度降低,使旋涡生成区域更靠近圆柱表面;脉动频率与无量纲脉动振幅的增大使升力系数、阻力系数的振幅均增大,而且与升力系数相比,阻力系数的振幅更大,变化更快;升力系数频谱图存在多个主频,包括旋涡脱落频率和相位叠加频率,其中旋涡脱落频率的振幅随着脉动频率的增加而减小,随着无量纲脉动振幅的增加而增加。在流场中加入脉动流,可以增强流体振动促进流动混合。     

湿法烟气脱硫的理论和实验研究(IV)——高雷诺数时的传质经验方程

在中试湿壁塔中,采用ＳＯ２／ＮａＯＨ和空气／Ｈ２Ｏ系统,实验研究了５０℃和高雷诺数时的气液传质速率。实验结果表明,气相雷诺数（ＲｅＧ）和液相雷诺数（ＲｅＬ）分别在７６００～１３５００和４７００～１２０００的范围内,气相舍伍德数（ＳｈＧ＝（ｋＧａｃｄｉ）／ＤＧ）分别与ＲｅＧ的１０４次方和ＲｅＬ的０２０７次方成正比。ＳｈＬ分别与ＲｅＧ的０６４次方和ＲｅＬ的０４３８次方成正比。高雷诺数时的液膜波动提高了相界面积和湍流程度,从而导致气相和液相传质系数的提高。     

管内气液两相流涡街稳定性分析

为了研究管内气液两相流涡街的内在特征,提出1个量纲为1的变量即稳定性指数,根据稳定性指数偏离稳定状态的程度,定量判断管内气液两相流涡街的稳定性。以空气和水为介质,以三角柱为旋涡发生体,在内径为50mm的水平管和垂直上升管中分别进行实验,分析雷诺数和体积含气率对气液两相流涡街稳定性的影响。研究结果表明：体积含气率对管内气液两相流涡街的稳定性起主要作用;在水平管中,当体积含气率小于15％时,涡街比较稳定,稳定性指数的取值为1．00±0．16;当体积含气率大于15％时,稳定的涡街难以维持,部分涡街的稳定性指数为2．0-3．0：在垂直上升管中,稳定的涡街体积含气率可以达22％,在此范围内,稳定性指数的取值为1．00-0．12;当体积含气率大于22％时,涡街变得不稳定,此时,部分涡街的稳定性指数为0．50～0．75。     

脉动流条件下圆柱绕流特性研究

该文数值研究了脉动流条件下圆柱绕流场特性，对涡量分布、升阻力系数、升力系数频谱特性等进行了分析。结果表明，脉动流作用会使圆柱尾涡剪切层变薄，提高脉动频率使尾涡长度变短、脱离加快，提高无量纲脉动振幅使主导涡的脱落速度降低，使旋涡生成区域更靠近圆柱表面；脉动频率与无量纲脉动振幅的增大使升、阻力系数的振幅均增大，而且与升力系数相比，阻力系数的振幅更大，变化更快；升力系数频谱图存在多个主频，包括旋涡脱落频率和相位叠加频率，其中旋涡脱落频率的振幅随着脉动频率的增加而减小，随着无量纲脉动振幅的增加而增加。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

英文诗歌中的喻类修辞

为了有助于提高英文爱好者的个人情操、文化素养和学习兴趣,以及专业人员对英语学习和研究进行多途径的探索,本文通过一些精选诗歌的引证和分析,着重论述了喻类修辞法在英文诗歌中的运用其及效果。     

Man Is Unable to Change the Miserable Life——Analysis of the Arrangement of Four Characters in The Glass Menagerie

Tennessee Williams is considered as one of the most important American playwrights since World War II.The Glass Menagerie is his first successful drama,which describes a tragic situation of family and means to say that Man is unable to change the miserable life,no matter whatever means he try,This essay focuses on the analysis of the arrangement of the four main characters:Laura.Amanda,Jim and Tom to reveal the theme.Laura is fragile.Amanda is brave.Jim is vital.Tom is sensible.And all of them develop and try the different means to struggle against life,but fail tragically.With the evidence,the paper comes to conclusion naturally that Man is unable to change the miserable life,and he dooms to fail.     

Characterization of root-nodulating bacteria on Retama raetam in arid Tunisian soils

The aim of this study is to investigate the diversity of Retama raetam root-nodule bacteria isolated from arid regions of Tunisia. Twelve isolates, chosen as representative for different 16S rRNA gene patterns, were characterized by 16S rRNA gene sequencing and phenotypic analysis. Isolates were assigned to Sinorhizobium, Rhizobium and Agrobacterium. Symbiotic properties of Sinorhizobium and Rhizobium isolates showed a large diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Strain RK 22 identified as Rhizobium was the most effective isolate.     

Features of Women''s language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Affordable Accurate Evaluation of the Binding Conformations Predicted by Molecular Docking Studies in Bio-System

正Recently,docking has been widely used to predict the binding-modes of protein-inhibitors,when the crystal complexes structure was absent.Most docking algorithms are able to generate a large number of probable conformations,it,however,is difficult to effectively evaluate these docking poses and identify the most reasonable bindingmode.In the present study,on the basis of the crystallographic data of human 3-hydroxy-3-methylglutaryl coenzyme