二自由度振动系统矩阵复指数算法的改进

当位移阻抗矩阵的行列式为零时，利用矩阵复指数算法不能求解出多自由度振动系统的强迫振动解析解．以二自由度无阻尼系统为例，在分析外激励力频率与特征方程关系的基础上，提出了求解共振时强迫振动的方法，并分析了共振时的振幅变化情况．     

一类二阶振动矩阵方程的求解

研究了一类二阶振动矩阵方程的求解问题,该方程在振动控制领域得到广泛应用。针对具有约当对角标准型的特征值情形,提出了一种求解该二阶振动矩阵方程的参数化方法。该参数化方法给出了该矩阵方程中两个未知矩阵的完全参数化表达式,其含有自由参量为二阶振动矩阵方程的解提供了全部自由度。最后,利用所提出的二阶振动矩阵方程的参数化方法对数值算例进行了求解,结果表明该参数化方法的简单和有效性。     

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．     

具有非线性扰动与外部干扰的结构系统鲁棒H∞控制

针对一类具有非线性不确定及外部扰动的结构系统,提出一种基于线性矩阵不等式的鲁棒H∞主动控制策略.当结构系统质量矩阵中存在摄动时,将其描述为一种中立不确定的动态模型系统,通过鲁棒H∞控制方法同时保证了结构系统在模型和参数摄动下以及在控制变量和扰动存在非线性不确定性时的鲁棒稳定.最后通过对一个单自由度建筑结构模型在地震波作用下的主动振动控制仿真证明了该方法的有效性.     

基于摄动法的不确定性汽车悬架振动控制特征值的凸模型分析

对含有不确定性参数悬架系统的振动控制问题进行研究.应用多维椭球凸模型理论将区间不确定参数悬架系统的振动控制问题转化为确定性问题来处理.基于矩阵摄动法利用凸模型理论分析不确定参数对汽车悬架系统的影响,推导具有不确定参数闭环系统特征值的上、下界计算公式.计算结果表明:所提出方法对两自由度汽车悬架系统有效.     

线性阻尼系统设计的新途径——模态阻尼比矩阵理论的应用

本文应用多自由度系统临界阻尼矩阵和模态阻尼比矩阵理论,提出了设计线性阻尼振动系统的新途径。根据已知系统质量矩阵、刚度矩阵和所希望得到的系统振动状态,适当选择、配置阻尼即可达到欲想的设计效果。这种设计思想是在振动控制方面的一个尝试。本文以二自由度和四自由度为例,介绍了利用临界阻尼矩阵和模态阻尼比矩阵理论设计各模态为临界阻尼和过阻尼的振动系统的设计方法。     

阻尼系统的特征

严格证明矩阵复指数法.用传递函数和复频响应函数,推导有阻尼多自由度系统的强迫振动解析解.有阻尼多自由度系统强迫振动解析解的构建,有助于分析主阻尼矩阵不为对角阵的情况.     

基于二元三次B样条拟插值的反应-扩散方程数值解

反应-扩散方程在科学和工程的许多分支中有着重要的应用,对此类方程数值解的研究具有重要意义.鉴于计算域的复杂形状、大量的自由度等导致计算非常困难,提出张量积型二元三次B样条法求解一类分数阶反应-扩散方程和交叉反应扩散系统,首先计算得出二元三次B样条拟插值的矩阵表达式,然后利用Matlab进行数值模拟,最后将数值模拟解与精确解进行对比.研究表明,当变量t的迭代次数较低时,所提方法行之有效.     

多自由度线性周期系统的振动研究

本文采用摄动法研究含有小参数的多自由度线性周期系统的振动稳定性和在外激励作用下的强迫振动响应计算问题,并提出了改善系统振动性能的方法.     

双摆振动系统的同相振动性

采用MIRONENKO的反射函数法研究了双摆振动系统x′=A(t)x与y′=B(t)y的同相振动性,其中A(t)=(aij(t))2×2,B(t)=(bij(t))2×2.假设F(t),G(t)分别为x′=A(t)x,y′=B(t)y的反射矩阵,当A(t+2ω)=A(t),B(t+2ω)=B(t)时,矩阵F(-ω),G(-ω)分别相似于x′=A(t)x,y′=B(t)y的根本矩阵.若特征方程|λE-F(-ω)|=0与|μE-G(-ω)|=0具有相同的特征根,则x′=A(t)x与y′=B(t)y的稳定性相同.文中给出了特征方程|λE-F(-ω)|=0与|μE-G(-ω)|=0具有相同特征根的充分条件.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

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-