不同润滑油黏度对碰摩转子-轴承系统动力学行为的影响

在考虑非线性油膜力的基础上,建立了具有碰摩故障的转子 轴承系统的动力学模型·用Runge Kutta法详细分析了该转子 轴承系统的碰摩故障特性,发现了由倍周期分岔进入混沌运动、阵发混沌等多种进入混沌运动的道路.并深入研究了改变轴承润滑油黏度对具有碰摩故障的转子 轴承系统的动力学行为的影响,发现随着轴承润滑油黏度的降低,转子响应在二倍临界角速度以上的混沌区域扩大了,但是润滑油黏度的降低对转子系统在亚临界区域的运动状态影响不大·该结果为碰摩转子 轴承系统的安全运行和故障诊断提供了依据和参考·     

滑动轴承-转子-定子系统耦合故障的非线性动力学特性

以某型发动机转子碰摩故障为背景,建立了滑动轴承-弹性转子-定子系统碰摩故障的四质量非线性动力学模型,分析了非线性油膜力、油膜剪力和碰摩力对转子系统耦合故障响应的影响·利用数值模拟分析了考虑油膜剪力情况下该系统的分岔与混沌运动,得到了该轴承转子定子系统在某些有实际意义的参数域内的非线性响应的Poincar啨映射图、Lyapunov指数曲线图、分岔图、相轨线图、轴心轨迹图和幅值谱图,发现了该系统的丰富的非线性行为·分析结果表明,系统响应在较宽的频率范围内存在着分频周期运动、拟周期运动和混沌运动,在混沌运动区内存在大量的窄带周期窗口     

非线性摩擦力对碰摩转子-轴承系统混沌运动的影响

在考虑轴承油膜力和非线性摩擦力的基础上,构造了具有碰摩故障转子-轴承系统的动力学模型,对碰摩故障转子在运行过程中的非线性行为进行了研究,并分析了转静件间相对速度影响因数对转子分岔与混沌运动的影响·发现随着速度影响因数的增加,在亚临界转速区,拟周期和混沌运动区域增大;在超临界转速区,混沌运动区域减小,碰摩力的作用效果增大,拟周期运动逐渐演变为周期3运动·该结果为转子-轴承系统的故障诊断提供了依据和参考·     

不平衡磁拉力对碰摩转子-轴承系统的影响

针对转子-轴承系统当同时存在动偏心和静偏心时,不平衡磁拉力引起的系统振动问题,从气隙磁场能出发,推导了同时考虑两种气隙偏心时的不平衡磁拉力表达式,并将其表示为电磁刚度的形式.通过拉格朗日方程,建立了不平衡磁拉力作用下碰摩转子-轴承系统的非线性动力学方程,利用四阶龙格-库塔法求解系统微分方程并得到转子的分岔图和频谱瀑布图等,分析了电磁刚度、系统转速、初始间隙和静偏心对转子-轴承系统振动特性的影响.研究结果表明:电磁刚度的存在使碰摩现象和油膜涡动发生延迟,有利于系统在中低转速区域的安全稳定运行;在初始间隙和静偏心的变化过程中,系统会出现拟周期运动与倍周期运动交替出现的规律,且静偏心越大,系统振幅越大.     

质量慢变转子系统的碰摩分析

根据离心机转子质量慢变以及偏心量大的特点,对其在线性碰撞力和线性摩擦力作用下的碰摩动力学特性进行了理论研究,建立了相应的质量慢变碰摩运动微分方程,并应用数值方法分析了转子转速及不平衡量的变化对碰摩转子系统的振动特性的影响,分别从不同侧面描述和揭示了质量慢变转子系统的周期运动、拟周期运动,以及这些运动形式的转化与演变过程·结果表明质量慢变转子系统相当于一个具有时变阻尼和时变刚度的转子系统,该系统的显著特点是在碰摩过程中转子呈现为拟周期运动,并非像相应的恒定质量转子系统那样出现混沌运动·     

滚动轴承-转子-定子系统的碰摩故障分析

以某航空发动机实验器为基础 ,建立了轴承 转子 定子多自由度系统碰摩故障模型 ,研究了具有局部碰摩的滚动轴承 转子 定子系统的非线性特性 ,利用数值模拟分析了该系统的分岔与混沌运动 ,得到了该轴承转子定子系统在某些有实际意义的参数域内的非线性响应的Poincar啨映射图、分岔图、相轨线图、轴心轨迹图和幅值谱图 ,发现了该系统丰富的非线性混沌行为·分析结果表明 ,转子碰摩刚度与转子弯曲刚度比明显影响轴承 转子 定子系统运动特性·系统响应在较宽的刚度比范围内主要以混沌运动为主·随着刚度比的增加 ,系统响应中的混沌区域逐渐增加·在混沌运动区内存在大量的窄带周期窗口·所得结果可供高速旋转机械碰摩故障诊...     

碰摩转子系统的稳定性

为研究一个支承在油膜轴承上的单盘转子系统在发生动静件碰摩时系统的稳定性 ,假定轴承为短轴承近似和碰撞为弹性碰撞后 ,导出包括分段线性刚度和非线性油膜力的非线性运动微分方程 ;使用打靶法求系统的周期解并结合 Floquet理论分析解的稳定性 ,发现了在系统的运动中具有倍周期分岔和 Hopf分岔现象 ;研究结果对于更好地了解转子系统的碰摩故障以及其早期预测有意义     

考虑油膜力的弹性转子系统碰摩故障研究

以现代非线性动力学和转子动力学理论为基础,分析了带有碰摩故障的弹性转子系统的动力学行为·针对短轴承油膜力的强非线性特点,用RungeKutta法在较宽范围内研究了定子刚度和激励频率等参数对该碰摩转子系统动态特性的影响,发现参数变化时系统存在周期、拟周期和混沌运动等丰富的非线性现象:该碰摩转子系统在一阶临界转速附近系统响应为混沌运动,转速较高时系统响应表现为拟周期运动,定子刚度很大时系统响应处于工频状态·该研究结果为转子轴承系统故障诊断、动态设计和安全运行提供理论参考·     

含裂纹-碰摩气浮转子系统非线性动力学研究

考虑裂纹碰摩耦合故障下的转子系统,以转子动力学和非线性动力学为理论基础,建立了含有裂纹-碰摩耦合故障气浮轴承转子系统动力学模型,运用打靶法思想和四阶龙格库塔法对含有气膜力、裂纹及局部碰摩耦合转子系统进行数值模拟,发现此故障下的转子系统存在周期、拟周期以及混沌运动现象,为转子系统安全工作提供理论依据.     

圆盘偏心量变化转子的非线性动力学行为

为了研究转子圆盘偏心量对转子系统动力学行为的影响,建立了滑动轴承-转子系统的动力学模型及相应的运动方程。运用改进的Wilson-θ法并结合Floquet分岔理论研究了转子系统的稳定性及分岔行为,数值结果揭示了系统具有周期、周期2、周期4、周期8和周期5等复杂的非线性动力学现象。从计算结果可以看出,转子圆盘处的偏心量对转子系统的非线性动力学行为有着较大的影响,选择合适的参数可以提高转子的稳定性。     

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