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。     

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。     

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。     

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。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

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 Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the