凸轮的变异研究和电子凸轮发展

普通直动、摆动从动件盘形凸轮机构,借助凸轮轮廓形状,由凸轮转动来实现预期的从动件运动;通过对凸轮机构的演化、变异,可以创造出新的凸轮机构形式,运用“变速驱动”的理念设计凸轮,可得到变速凸轮,采用将传统机械凸轮与电子技术结合,派生了电子凸轮,种种柔性化设计思想和方法的探讨,其宗旨是扩大凸轮的应用范围,弥补和克服传统机械凸轮轮廓形状不可改变、运动方式不可调节等不足,为凸轮的更广泛使用创造契机。     

发动机配气机构凸轮-从动件接触应力分析

配气机构中凸轮与从动件是一对重要的摩擦副,较易出现磨损、擦伤、劈裂等破坏。针对凸轮与从动件之间容易产生破坏的情况,通过改变气门弹簧的预紧力与刚度,以降低凸轮与从动件之间的接触应力,减少凸轮从动件间的接触破坏。利用AVL EXCITE Timing Drive建立某发动机配气机构单阀系动力学模型,对不同转速下的模型进行动力学分析。在Design Explorer中进行拉丁超立方试验设计,再通过Nelder-Mead算法对得到的试验数组进行优化,得出最佳的接触应力、弹簧预紧力与刚度的组合。试验与优化过程中,通过设置接触损失角和气门落座速度两个约束条件对优化结果进行约束,以防止弹簧预紧力与刚度的变化对机构整体的影响。优化得到的弹簧预紧力与刚度使得不同转速下最大接触应力均有所降低,且未出现飞脱现象。     

直动从动件凸轮机构误差的影响

视凸轮机构中各构件的尺寸误差为随机变量，应用根据概率理论建立的凸轮机构误差分析模型，分析了直动从动件凸轮机构中各构件尺寸误差对从动件运动的影响，确定了不同运动规律对误差的敏感性。     

按许用压力角确定摆杆盘形凸轮基本尺寸

基于平面凸轮机构与平面四杆机构运动和动力特性相似原理,导出摆动从动件盘形凸轮机构最大压力角作用位置与从动件运动规律的关系式。由关系式可知,最大压力角的位置仅与运动规律有关,与基本尺寸无关;最大压力角大小不仅与运动规律有关,而且与基本尺寸有关,在给定许用压力角的条件下,可确定凸轮基本尺寸,比其它方法简捷方便。     

单圆弧盘型凸轮机构特性的比较研究

提出了用高副低代的化归方法研究单圆弧对心直动滚子从动件盘型凸轮机构的特性．论证了化归后的机构瞬时速度、加速度和压力角与原机构等价，在此基础上讨论了原机构的运动特性．并以最大无量纲速度和加速度为标准，将凸轮机构从动件常用运动规律特性与该圆弧凸轮的从动件运动规律特性加以比较，指出其适用场合为中、高速轻载。     

盘形凸轮机构直动从动件导路系统尺度综合

现有凸轮机构基本尺寸综合方法不考虑从动件、导路系纯尺度的影响,方法欠妥.本文提出一种从动件、导路系统尺度综合方法,丰富了凸轮机构基本尺寸综合理论.     

考虑轴承间隙的凸轮机构的动力学分析

在研究带有轴承间隙的凸轮机构的动力学特性中,可以依据测定的间隙角及其一、二阶导数,求出满足间隙角基本方程的条件。本文以有直线段的凸轮及滚子为从动件的凸轮机构为例介绍这一动力学分析过程。结论是：凸轮机构的加速度、力和扭矩的剧变实质上是由旋转间隙引起的;剧变的程度取决于间隙的大小、凸轮轴的转速,而凸轮和从动件的尺寸大小对凸轮机构的加速度、力和扭矩的影响相对要小得多。     

确定摆动从动件盘形凸轮机构基圆半径的一种解析法

分析了摆动从动件盘形凸轮机构的压力角与基本尺寸之间的关系，提出了一种求解摆动从动件盘形凸轮机构基圆半径的方法，该方法对任意形式的从动件函数，即可直接作图求解，也容易推导解析方程求解。     

考虑轴承间隙的凸轮机构的动力学分析

在研究带有轴承间隙的凸轮机构的动力学特性中,可以依据测定的间隙角及其一,二阶导数,求出满足间隙角基本方程的条件。本文以有直线段的凸轮及滚子为从动件的凸轮机构为例介绍这一动力学分析过程。结论是：凸轮机构的加速度,力和扭矩的变实质上是由旋转间隙引起的;剧变的程度取决于间隙的大小,凸轮轴的转速,而凸轮和从动件的尺寸大小对凸轮机构的加速度,力和扭矩的影响相对要小得多。     

直动从动件六圆弧盘形凸轮机构的运动学研究

建立了直动从动件六圆弧盘形凸轮机构从动件运动规律及压力角的表达式,分析了有关几何参数对运动特性的影响,可用于尖底及滚子接触直动从动件六圆弧盘形凸轮机构的优化设计．     

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