拉格朗日方程的菱形翼布局无人机建模

为建立菱形翼布局无人机的动力学模型,提出一种基于拉格朗日方程的动力学建模方法,首先选取四元数用于参数化该无人机的姿态,建立该无人机系统的约束矩阵;其次通过虚功的形式建立无人机的广义力矩阵,建立无人机的动能与势能模型;最后通过矩阵直积的概念得到与无人机系统约束矩阵乘积为零的矩阵,通过该矩阵消掉拉格朗日方程中的拉格朗日乘子,基于拉格朗日方程模块化地建立该无人机的动力学模型。为与拉格朗日方程进行对比,同样采用Kane方程和ADAMS软件建立该无人机的动力学模型。仿真结果表明,拉格朗日方程、Kane方程以及ADAMS软件的仿真结果基本一致,验证了动力学建模方法的合理性。     

圆锥杆垂直侵彻半无限厚水泥靶时应力波传播特性研究

根据动量定理和动能定律,建立了圆锥杆垂直侵彻半无限厚水泥靶时的动力学模型,并对所得到的这些非线性动力学方程进行数值求解,藉此分析了等效撞击力,进而根据牛顿第二定理建立了圆锥杆的波动方程,研究了应力波在圆锥杆中的传播特性和规律．     

临近区间隧道抗疲劳受压防火门的疲劳寿命预测

研究区间防火门的抗疲劳破坏性能对实际工程投产运营阶段消除安全隐患具有重要意义。本文基于ABAQUS有限元软件建立防火门简化数值模型和考虑接触关系的精细化模型,利用防火门性能测定试验结果比较验证了模型的准确性,并以该模型为基础计算分析了恒定风压及往复风压条件下,临近区间隧道抗疲劳受压防火门各部件的应力状态,并根据研究结果给出了防火门在往复风压下疲劳寿命预测方法。研究结果表明：防火门的高应力区主要集中在闭门锁和铰链与门体的连接区域;依据应力分布情况得当闭锁点处的预测循环寿命为3.69×105次,铰链处的预测循环寿命为1.3×106次,门体其他部分的疲劳寿命则在1×108次以上。     

机器人动力学建模

本运用Ｋａｎｅ方法，计入摩擦力和陀螺力的影响，建立通用的机器人动力学模型。该模型不仅具有Ｋａｎｅ方程的优点，而且兼有Ｌａｇｒａｎｇｅ方程的形式和Ｎｅｗｔｏｎ－Ｅｕｌｅｒ方程的递推性，它特别适用于数值计算，方程的自动生成和动力学特性分析。     

一类非线性广义系统结构稳定的李亚普诺夫判据

非线性广义系统的结构稳定性的研究有实际意义,基于李亚普诺夫方程,研究了一类非线性广义系统平衡点稳定的问题·用李亚普诺夫方法研究了此类非线性广义系统的结构稳定问题,在此基础上,得到了这类非线性广义系统结构稳定和李亚普诺夫方程的解的关系·最后,给出了这类非线性广义系统结构稳定的充要条件,并且用简单的数值算例说明了定理的可行性·     

双边塑性碰撞调谐质量阻尼器的位置控制

建立双边塑性碰撞调谐质量阻尼系统的动力学模型,根据Poincare映射图,研究了系统的周期运动和分岔,以及碰撞对结构稳定性的影响,并且分析了误差动力学方程的收敛速度与系数矩阵A的关系。利用同步反馈控制法对双边塑性碰撞调谐质量阻尼系统进行位置控制,数值计算结果验证了该方法是可行有效的。     

计入基础运动的环状周期结构振动特性分析

研究了一类工程领域广泛应用的环状周期结构的弹性振动特性,重点分析了基础运动对弹性振动稳定性和固有频率分裂的影响.首先在随动坐标系下采用Hamilton原理建立了计入基础运动和面内切向及径向弹性振动的偏微分形式的动力学模型.然后,应用伽辽金方法将其离散得到一组常微分动力学方程.根据经典振动理论,得到了系统特征值的数学表达.最后采用数值方法计算了系统的特征值.根据特征值的实虚部取值预测了不稳定域和固有频率分裂规律,并用Runge-Kutta法给出稳定性的数值验证.该研究为陀螺仪等呈现平面或空间基础运动的环状周期结构的动态性能的改善提供了理论借鉴.     

建立离散系统动力学方程的矩阵方法

本文提出了一种建立离散系统运力学方程的矩阵方法,该方法适合于完整系统及线性非完整系统。应用这一方法,不必像使用Lagrange方程那样需先建立系统的动能表达式再作繁琐的求导运算,而只需要通过简单的函数求导及矩阵的相乘运算便可建立起离散系统的动力学方程,而且这种形式的动力学的方程便于进行数值求解。     

五自由度虚拟轴机床刚—柔耦合动力学模型

针对一种用于研磨自由曲面的新型虚拟轴机床，建立基于Lagrange方程的空间刚—柔耦合动力学模型。考虑虚拟轴机床整体的刚性运动与各支链弹性变形间的相互作用或耦合，将机床的各个支链和平台看作独立的子结构，建立各自的动力学方程，根据子结构之间的约束关系建立系统约束动力学方程。该方法为虚拟轴机床动力学研究提供了新的思路。     

考虑刚-弹耦合叶片系统的稳定性分析

基于离散的方法建立了圆盘和叶片的动力学方程，该方程中包含有陀螺阵，并且陀螺阵和刚度阵是时变的矩阵，文中采用状态空间转移法对系统的稳定性进行了分析，最后对该方程进行了稳定性的数值仿真。     

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.     

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