弦振子振动分析(Ⅱ)--双质点系统

利用拉格朗日方程建立了双质点弦振子振动方程,对其振动进行了分析;研究了双质点弦振子的模态局部化现象,找到了产生模态局部化的“阚值”。利用MAPLE9．0计算机绘图,作出了振幅比和固有频率随参数变化曲线。所得结论为振幅比与参数β无关,振幅比随参数α的增大而增大;固有频率随参数β的增大而增大,随参数α的增大而减小;双质点弦振子有模态局部化现象。     

三质点弦振子系统振动分析

利用拉格朗日方程建立了三质点弦振子振动方程,对其振动进行了分析,利用级数展开,得到了三质点弦振子的级数解,利用MAPLE9．0计算机绘图,作出了级数解和振幅比随参数变化曲线。所得结论为级数解x1随参数β和t增加而减小;级数解x^2随参数α增加而增加,随参数口增加而减小。     

反共振方法及其应用

建立了两自由度系统的振动方程及模态响应，利用计算机绘图作出了固有频率ω^2和振幅比γ随参数α和卢的变化曲线；通过具体算例对反共振现象进行分析，所得结论为除低频ω^2在α等于1时与参数β无关外，其它ω^2随参α的增加而减小，随参数卢的增加而增加．振幅比γ随参数α的增加而增加，随β的增加而减小．在工程实际中，常利用反共振现象来达到吸振的目的．     

单质点弦振子振动分析

利用拉格朗日方程建立了单质点弦振子非线性振动方程,应用微扰法与线化和校正法对单质点弦振子进行了求解;利用MAPLE9.0计算机绘图,分别作出了它们的周期近似解随振幅的变化曲线以及近似解与数值解的变化曲线.所得结论为利用线化和校正法所求得的近似解与数值解比较,具有简单实用、精度高、相对误差低等优点,在求解非线性振动中具有一定的实用价值.     

不可压缩流中板状结构的振动分析

研究了一个两跨板状结构的简单模型在不可压缩流中振动的固有特性.采用假设模态法建立了系统的运动微分方程,着重考察结构非对称对固有频率和模态局部化的影响.研究结果表明,结构非对称是导致模态局部化现象的主要因素,而结构的固有频率随流体速度的增大而减小.     

斜缝式变厚度环形振子径-扭复合振动特性仿真分析

采用有限元数值仿真方法对变厚度斜缝式环形振子的径-扭复合振动特性进行了研究;探讨了振子的共振频率及质点扭-径位移比与斜缝长度和斜角之间的关系;通过施加正弦载荷激励,得出了振子内表面质点的椭圆轨迹图.研究表明:斜缝式变厚度环形振子的第1阶共振频率随斜缝径向长度及斜角的增大而降低;而其质点扭-径位移比随斜缝径向长度及斜角的增大而增大;随着斜缝径向长度及斜角的增大,径向位移减小,而周向位移增加,模态分析与瞬态分析结果相一致.     

单质点弹性绳振动分析

利用拉格朗日方程建立了单质点弹性绳振子非线性振动方程,用逐级微扰的方法对单质点弹性绳振子进行了求解;利用MAPLE9.0计算机绘图,作出了微扰解随参数α和t变化的三维曲线。所得结论为随着参数α和t的增加,微扰解x的值逐渐减小。     

径向开槽薄圆环振子径向振动分析

为研究径向开槽圆环的径向振动特性,基于机电类比原理,建立了开槽圆环的径向振动等效电路,并得出其共振频率方程,探讨了圆环第1、第2阶共振频率及振幅放大系数与其半径比的关系.结果表明:圆环第1阶共振时振幅放大系数随半径比的增大而增大,第2阶共振时振幅放大系数随半径比的增大而下降;其共振频率随半径比的增大而单调上升;理论与有限元数值仿真结果基本一致.     

双弹簧振子横向振动的理论研究

建立了双弹簧振子横向振动的运动微分方程,该方程为一非线性方程,表明此时振子的运动不是简谐振动.然后采用同伦分析法求得了该问题的高精度近似解析解和周期,结果表明横向振动时的圆频率正比于弹簧振子作纵向简谐振动时的固有频率,在小振幅振动时该频率正比于振幅.所得近似解与数值解吻合地很好.     

Timoshenko梁的第二频谱分析

推导Timoshenko梁振动微分方程的初参数解,结合边界条件,建立简支梁的频率方程.当固有频率小于临界频率时,频率方程有双曲正弦函数与三角正弦函数之积的因式,当固有频率大于临界频率时,此因式变成为双三角正弦函数之积,此即Timoshenko梁产生第二频谱的理论原因.推导出等截面等跨径的2～3跨连续Timoshenko梁的频率方程,并从理论上预测存在第二频谱现象的其他结构.建立了简支Timoshenko梁第一、二频谱的频率计算公式.通过实例验证第二频谱的存在.通过微分方程求解,论证了临界频率是结构固有频率的有效组成部分,其对应的竖向位移模态无振幅、转角位移模态的振幅为常数;指出数值分析时,由于计算机截断误差的影响,所预测的临界频率有误差、所对应的竖向位移模态为不规则模态等特点.     

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     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with