由Kirchhoff方程导出压杆的临界载荷

用Kirchhoff方程讨论压杆的稳定性,导出了适合任意端部约束的、直杆的 线性化扰动方程及其通解;根据积分常数非零解的存在条件,分别导出了不同端部约束压杆 的临界载荷.     

用经典Hopkinson杆测试弹性模量的初步探讨

采用一维弹性应力波理论,实现了经典Hopkinson杆试验的计算机模拟,研究了试验"测得"(重构)的应力-应变曲线的精确度,并结合具体试验进行了分析.由于经典Hopkinson杆试验的基本计算公式中引入了"应力均匀性"假设,因此在有限应变范围内,重构的应力-应变曲线总是和输入(真实)曲线差异较大.结果表明,采用经典Hopkinson杆测量的弹性模量是不可靠的,因此实践中应慎用.     

径向辛体系一种新的差分格式

通过对Hellinger-Reissner变分原理进行坐标变换,将径向模拟为时间,导向辛体系,得到Hamilton对偶方程组.将微分形式的有限差分法引入弹性力学极坐标系下径向辛体系,把对偶方程组中的微分方程直接改用差分方程代替,推导出极坐标系下问题的辛差分方程,从而得到一种全新的径向辛体系差分格式.求解方程组,可直接得到位移和应力.编程计算曲梁等算例,结果表明该辛差分格式是有效的,丰富了弹性力学辛体系差分法的内容.     

Stability of theoretical model for catastrophic weather prediction

Stability related to theoretical model for catastrophic weather prediction, which includes non-hydrostatic perfect elastic model and anelastic model, is discussed and analyzed in detail. It is proved that non-hydrostatic perfect elastic equations set is stable in the class of infinitely differentiable function. However, for the anelastic equations set, its continuity equation is changed in form because of the particular hypothesis for fluid, so "the matching consisting of both viscosity coefficient and incompressible assumption" appears, thereby the most important equations set of this class in practical prediction shows the same instability in topological property as Navier-Stokes equation, which should be avoided first in practical numerical prediction. In light of this, the referenced suggestions to amend the applied model are finally presented.     

Anchoring properties of substrate with a grating surface

The anchoring properties of substrate with a grating surface are investigated analytically. The alignment of nematic liquid crystal (NLC) in a grating surface originates from two mechanisms, thus the anchoring energy consists of two parts. One originates from the interaction potential between NLC molecules and the molecules on the substrate surface, and the other stems from the increased elastic strain energy. Based on the two mechanisms, the expression of anchoring energy per unit area of a projected plane of this grating surface is deduced and called the equivalent anchoring energy formula. Both the strength and the easy direction of equivalent anchoring energy are a function of the geometrical parameters (amplitude and pitch) of a grating surface. By using this formula, the grating surface can be replaced by its projected plane and its anchoring properties can be described by the equivalent anchoring energy formula.     

Vibration reduction of floating elastic plates in surface waves

Based on dynamical theories of water waves and dynamics of Mindlin thick plates,the investigation of the wave-induced responses and the vibration reduction of an elastic floating plate are presented using the Wiener-Hopf technique.Without regard to the case of elastic connector,the calculated results obtained by the present method are in good agreement with those from the literature and the experiment.It can be shown that the present method is valid.Relations between the spring stiffness to be used to connect the sea bottom and the floating plate and the parameters of wave-induced responses of floating plates are investigated using the present method.Therefore, these results can be used as theoretical bases for the design stage of super floating platform systems.     

纪念钱伟长先生诞辰100周年北大核心CSCD

钱伟长（1912年10月9日-2010年7月30日） 今年10月9日,是本刊创办人钱伟长教授诞辰100周年。钱伟长教授是我国最杰出的、也是国际知名的力学和应用数学家之一。他在上世纪40年代关于弹性板壳内禀理论的工作,不仅统一了当时众说纷纭的各种板壳理论,同时也开创了理性力学的新领域。在40到50年代关于奇异摄动理论和弹性圆薄板大挠度问题的研究、60年代关于广义变分原理的研究,都是领一代风气之先的开创性工作。他不仅在应用数学和力学的各个方面作出了重要贡献,对中国力学事业发展所起的作用也是不可替代的,他是中国的第一个力学专业、第一个力学研究机构的创办人,是促进中国非线性力学发展的带头人,他被公认为中国当代力学的四位奠基人之一。     

多种气相色谱联用技术分析陕西刺五加茎挥发油的化学成分

采用气相色谱/四极杆质谱(GC/qMS)、气相色谱/正交加速飞行时间质谱(GC/oaTOFMS)和气相色谱/傅里叶变换红外光谱(GC/FTIR)联用技术,对一种陕西产刺五加Acanthopanax senticosus (Rupr. et Maxim.) Harms茎挥发油的化学成分进行了分析。基于GC/qMS谱库的检索功能,结合GC/FTIR在结构鉴别上的优势和GC/oaTOFMS对质谱碎片离子精确的质量测定功能,成功地实现了对68个色谱组分的定性分析。与使用单一的联用技术(例如GC/qMS)相比,利用多种色谱联用技术在定性分析上的互补性,可以明显提高对组成复杂的挥发油类样品分析的可靠性。     

Dependence of modulus of elasticity and thermal conductivity on reference temperature in generalized thermoelasticity for an infinite material with a spherical cavity

Introduction Thetheoryofgeneralizedthermoelasticitywithonerelaxationtimebasedonamodified Fourier’slawofheatconductionwasdevelopedbyLordandShulman[1].Thistheoryallowsfor theso_calledsecond_soundeffectsinsolids,hencethermaldisturbancespropagatewithfinite wavespeeds. Themathematicalmodelofthegeneralizedthermoelasticitytheoryisofacomplicatednature thathindersthepossibilityofderivingananalyticalsolution.Mostattemptsdealingwiththese equationsarebasedoneithershort_timesolution[2-4]. Modernstructur…     

HMX/TATB复合材料弹性性能的MD模拟

用分子动力学(MD)方法COMPASS力场, 分别在正则系综(NVT)和等温等压系综(NPT)下, 模拟计算了著名常用高能炸药HMX(环四甲撑四硝胺)与著名钝感炸药TATB (1,3,5-三氨基-2,4,6三硝基苯)所构成的混合体系在室温时的弹性性能和结合能. 结果表明, 在NVT和NPT两种系综下模拟所得结果呈平行一致的趋势; 与纯HMX相比, HMX/TATB复合材料的拉伸模量、体模量和剪切模量均有所下降; 在NVT系综下, 还完成了HMX/TATB混合体系的不同温度的MD模拟. 发现当温度在245～345 K范围时, 体系的刚性和弹性变化很小; 但当温度达到395 K时, 材料的刚性减弱, 柔性增强.