用再生谱分析技术对立轴平磨进行动态设计

本文应用再生谱计算技术分析了立轴平磨系统中的颤振频率、颤振增长率和特征根在复平面的分布情况,并应用该技术探讨了机床工艺参数和模态参数变化对系统稳定性的影响效果。应用再生谱可非常简便直观地确定机床系统的敏感模态,并能对机床薄弱模态的修改效果给出一个定量的评价。     

用DDS方法识别机床模态频率和薄弱模态

机床是一个多自由度、多变量随机输入的复杂动态系统。机床结构动态特性的研究是机床实验、设计和验收等项工作的重要理论基础。机床加工时受到动态切削过程各因素的影响,由于机床结构和切削过程两方面因素的交互作用,常可激发颤振,引起机床稳定性问题。确定机床主要模态和模态参数,以及机床结构影响颤振的薄弱模态是问题的关键。     

薄壁零件高速铣削稳定性的分析

针对薄壁零件在铣削加工过程中存在的切削颤振问题,建立了铣削颤振理论模型,进行模态分析试验和铣削加工试验．获取系统动态性能参数和铣削力系数．在此基础上建立了薄壁结构零件铣削加工的稳定性耳瓣图,为今后的薄壁零件加工稳定性研究工作打下了基础．     

某铣床的动力学模态优化分析

为提高某型数控铣床的加工稳定性与抗振性,分别建立试验模型和有限元模型,通过试验模态分析手段识别模态参数,以模态频率相关性和模态振型相关性准则修正有限元模型,使修正后的有限元模型具有更好的仿真精度,能真实反应实际工况,从而对机床建立有效合理的有限元模型,在修正后的有限元模型中分析机床的振型与抗振性,对机床薄弱部分进行分析,提出针对性修改意见,并对改进后机床的有限元模型进行了仿真,论证了改进方法的有效性与合理性.     

柴油机气缸体组件的试验模态分析

将试验模态分析技术应用于4113柴油机的动态分析，通过对4113柴油机气缸体组件的试验模态分析，得到气缸体组件的模态频率和振型参数，并对前6阶模态振型的结果进行分析，根据试验结果，找出气缸体组件的薄弱部位并为其结构的优化提出初步的改进意见。     

单群Cq（2）的一个新刻画

记ω（G）为有限群G的元素的阶的集合．假定工为有限单群Cp（2）,G为满足条件ω（G）=ω（L）的任意一个有限群,则群G含有唯一一个非交换的合成因子,其同构于单群L;也就是说,单群Cp（2）是拟可刻画的．这个结果同时也证实了施武杰提出的猜想对于单群Cp（2）是成立的．     

机床振动系统阻尼比测定方法的探讨

机床振动系统的阻尼比通常是根据幅频特性曲线用公式 Ｄ＝（ωｂ－ωａ）／２ω０求 得的． 本文试用另外两种方法，以求在使用数字信号分析仪时．提高测定阻尼比的精确 度。为了对比用各种方法测定阻尼比的偏差大小，在铣床和一些结构模型上进行了 一系列的测试．     

机床颤振预兆早期诊断的频率矩心判别法

本文提出了一种新的机床颤振预兆早期诊断方法——频率矩心判别法。试验表明:利用频率矩心能够对颤振预兆进行早期诊断。     

依靠切削颤振试验识别品质系数

本文提出了利用切削颤振试验识别机床结构品质系数ＣＯＭ这一新方法．试验结果表明该方法测量精度高，重复性好，测得的ＣＯＭ与最小极限切削宽度之间的相关性很好．     

8维辛流形上的Seiberg—Witten方程

８维辛流形上的ＳｅｉｂｅｒｇＷｉｔｅｎ方程贾方（数学系）设（Ｍ，ω）是紧致８维辛流形．Ｍ上的一个近复结构Ｊ称为是与ω相容的，如果ｇ（Ｘ，Ｙ）＝ω（Ｘ，ＪＹ）定义了Ｍ上的一个Ｒｉｅｍａｎｎｉａｎ度量．Ｍ上这样的近复结构总是存在的．我们固定Ｍ上一个与ω...     

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