非线性变速轴向运动黏弹性梁稳态响应

研究了非线性变速轴向运动梁稳态幅频响应.变速轴向运动梁的控制微分方程被建立,黏弹性本构关系引入了物质时间导数,考虑了由均匀轴向运动梁变形的影响而导致梁轴向伸长而引起的附加力,并以轴向张力平均值代替梁上各点的精确值,建立了积分一偏微分非线性轴向运动梁的控制方程.轴向运动梁两端的边界为带有扭转弹簧的套筒铰支的混杂边界条件,同时认为轴向运动速度在平均速度附近做微小简谐脉动.应用渐进摄动法直接求解非线性变速轴向运动梁的控制方程并导出了当扰动速度的频率接近未扰系统任意两个固有频率之和时所发生的组合参数共振的稳态幅频响应方程和振幅方程.数值结果给出了轴向运动梁的黏弹性、扰动振幅、非线性对稳态幅频响应的影响.结果显示,轴向运动梁的材料的黏弹性增大时,零平衡位置的失稳区域会减小;当梁的轴向扰动速度幅值增大时,零平衡位置的失稳区域随之增大;稳定及非稳定的两条非零解曲线的振幅都会因为非线性系数的增大而减小.零解失稳范围则不受非线性项的影响.     

热环境中功能梯度材料Euler梁的自由振动

研究功能梯度材料Euler梁在温度场作用下的屈曲和自由振动行为.在精确考虑轴线伸长基础上,建立功能梯度Euler梁在热载荷作用下的几何非线性控制方程.将控制方程的响应分解为热过屈曲静态解和振动解两部分,得到功能梯度材料梁在热过屈曲构型附近小振幅线性自由振动的微分方程.其中,假设功能梯度的材料性质沿厚度方向按照幂函数连续变化,采用打靶法数值求解所得强非线性边值问题,获得在横向升温场内两端固定Euler梁的热过屈曲平衡路径以及前三阶固有频率的数值解.分析和讨论梁的材料梯度参数、温度场分布参数等因素对过屈曲变形和振动响应的影响.     

热-机载荷作用下弹性梁大振幅振动的混沌响应

考虑几何非线性和外阻尼效应,导出弹性梁大振幅振动的动力学控制方程,研究两端不可移简支梁在横向周期载荷和非均匀热载荷共同作用下的混沌运动.采用Galerkin变分原理将问题的非线性偏微分方程转化为二自由度的Hamilton系统,由Melnikov方法解析给出系统发生混沌运动的临界条件;数值计算出Lyapunov指数和分形维数,并绘制出反映系统运动特征的相平面图、位移波形图以及功率谱图,分析梁的非线性动力学行为.结果表明,在热轴力大于临界值后梁的运动会呈现混沌性态.     

高阶剪切理论下梯度直梁在热环境中的静动态响应分析

基于高阶剪切变形梁理论研究了两端不可移简支功能梯度梁在横向非均匀升温下的热屈曲和自由振动问题。首先依据高阶剪切变形梁理论和Hamilton原理建立了功能梯度梁受热-机载荷共同作用下的几何非线性动力学控制方程;在研究静态热屈曲问题时,把方程退化成强非线性边值问题,采用打靶法数值求解该边值问题,获得了横向非均匀升温下梁的屈曲构型,绘出了梁的变形随温度载荷及材料梯度参数变化的特征关系曲线;研究动态响应时,采用Navier方法数值求解所建立的动力学控制方程,获得了横向非均匀升温下梁的自由振动响应,数值比较了不同剪切理论下梁的前3解固有频率随跨高比、材料梯度参数变化的规律。结果表明,剪切变形、梁的跨高比、材料的非均匀性、温度变化对于高阶剪切功能梯度材料梁的变形及固有频率有很显著的影响。     

基于压阻反馈信号纳米梁非线性振动控制

研究了基于硅压阻效应纳米梁非线性振动控制方法。在纳米梁固定端上表面粘贴硅压阻膜片,压阻膜片的电阻值随着纳米梁的振动发生变化。利用惠斯通电桥电路提取振动信号作为电压反馈控制信号,控制纳米梁的非线性振动。用多尺度法求解方程,得到系统主共振的幅频响应方程。由幅频响应方程分析系统非线性振动方程解的稳定性,研究了交流激励电压幅值、阻尼、反馈增益参数对系统稳定性和振幅的影响规律。研究结果表明:激励电压由0.25 V减小至0.1 V时,最大振幅衰减60%。无量纲阻尼由0.058 5增加至0.087 8时,最大振幅衰减40%。增大阻尼和反馈增益参数可以减弱甚至消除纳米梁振动的非线性特性。该研究成果为纳米梁非线性振动控制及信号提取提供了一种理论方法。     

一类时滞反馈非线性系统的分岔与控制

考虑含参数激励的广义Van der Pol方程的Hopf分岔与控制问题。通过设计线性位移和速度时滞反馈控制器构造了受控系统,着重研究了控制器对该类参数激励系统的1/2亚谐共振的分岔响应控制。采用多尺度法从理论上推导出时滞动力系统的分岔响应方程,并进一步得到Hopf 分岔的存在条件。通过数值模拟,验证了所设计的控制器不仅能控制极限环的幅值,也能控制Hopf 分岔的产生。     

冲击载荷作用下夹层扁锥壳的非线性动力屈曲

研究了夹层扁锥壳在三角脉冲冲击载荷作用下的非线性动力屈曲问题。基于Reissner假设和Hamilton原理,导出了夹层扁锥壳在冲击载荷作用下的非线性动力控制方程;采用Galerkin方法和Runge-Kutta方法对控制方程进行数值求解,得到非线性动力响应曲线;应用Budiansky-Roth准则确定了冲击屈曲的临界荷载;讨论了壳体几何尺寸和物理参数对夹层扁锥壳冲击屈曲的影响;数值算例表明本文方法是可行的。     

纳米梁非线性振动隧道电流反馈控制

针对纳米梁振动中出现的非线性问题,提出了基于隧道电流反馈控制的纳米梁振动控制方法。将电子隧道效应理论应用于纳米梁的振动信号检测中,以提高信号提取的准确性,通过位移和速度两种电流反馈所产生的两种控制电压信号对纳米梁非线性振动进行控制,建立基于隧道电流反馈控制的纳米梁主共振非线性振动方程,并应用多尺度方法求得主共振幅频响应方程,研究了直流和交流激励电压、振动控制参数、阻尼值、控制电压等与纳米梁主共振幅频响应之间的关系,分析了影响系统振动非线性的因素。研究结果表明,减小直流激励电压至1. 5 V或交流激励电压降至1. 0 V,系统振幅峰值分别衰减50%和58%,振动非线性减弱;增大阻尼、减小系统控制电压以及选择适当的振动控制参数均可以使纳米梁主共振幅频响应得到有效控制,同时可以降低系统振动的非线性。     

水轮发电机定子磁固耦合电磁激发的分岔与混沌

为研究水轮发电机定子系统磁固耦合电磁激发非线性振动，以双壳系统模型作为水轮发电机定子系统的数学模型，应用非线性多尺度法分析水轮发电机定子双壳系统在电磁力作用下的主共振问题，并进行数值计算．结果表明，随着激励幅值的增大和阻尼的减小，系统主共振稳态响应的振幅增大．按照奇异性方法得到系统主共振分岔响应方程在开折参数和物理参数平面的转迁集和分岔图．利用Melnikov方法得到系统可能出现混沌运动的临界值．     

速度反馈中时滞参数对多自由度微陀螺动态响应的影响

将速度反馈控制器引入到微机械陀螺仪中,建立系统控制简化模型,通过对加入非线性刚度的系统动力学方程进行求解分析,进一步研究了时滞参数对多自由度微陀螺系统的影响规律。结果表明：时滞参数能有效调节系统检测响应的峰值和谐振频率,并消除非线性的影响,使系统趋于稳定。速度反馈增益的取值不会改变时滞参数对检测响应幅值的周期性规律,在不同的驱动周期下,检测响应的幅值随着反馈增益逐渐地增大或减小。     

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.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

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.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

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.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to