Numerical analysis of fatigue striations

A computational model was developed to numerically analyse fatigue striations. The inclined strip yield model with continuous distributions of infinitesimal dislocations was utilized to express the crack tip plasticity in this model. The fatigue crack tip blunting process was approximated by sequential activation of two slip lines under loading, and crack closure during unloading was taken into account. The plastic zone at a growing fatigue crack tip at the maximum load was independent of the crack growth up to ten cycles while the reversed plastic zone decreased in a size to one twentieth of that at the maximum load as the crack grew. The ratio of these plastic zone sizes and also the crack tip opening displacement were quite different from the simple prediction by J.R. Rice for a stationary crack. The computed striation spacings were compared with the observed ones and moderate agreement between them obtained.     

NMR spectra of oriented 2,2,2-trifluoroethanol (CF3CH2OH)

Photolysis of hydrogen sulphide in argon, nitrogen and carbon monoxide matrices at 20 K produces HS radicals and S atoms. On warming the matrix, H₂S₂ and S₂ molecules are formed as a result of recombination reactions. The latter are identified by a blue-purple emission observed during warm-up of the matrix.     

Variational principles for scattering in the generator coordinate method

The generator coordinate method (GCM) wave function is used as a trial function in a Kohn type variational principle for scattering phase shifts. It is shown that a GCM trial function is a solution of the variational equations if the Hill-Wheeler integral equation is satisfied subject to an appropriate boundary condition. A new method for introducing the scattering boundary condition is presented. There is a uniqueness theorem for the phase shift.     

RF field dependence of memory echoes in LiNbO3 and GaAs powder

Measurements of the rf electric field dependence of the amplitude of the “memory” echo in LiNbO₃ and GaAs powders are reported. Consistent with the torque-rotation model, the dependence on each of the three applied rf pulses is linear in the low power regime. At high power, more complex behavior is found including an irreversible decrease in the echo amplitude when the third applied pulse is larger than the preceeding two pulses.     

线性约束多目标规划的非单调信赖域算法

构造了一个解线性约束多目标优化问题的数值算法，该算法把一种非单调技巧与信赖域方法结合起来，从理论上分析，在一般条件下，算法全局收敛于问题的K—T点。     

基于对象演化的分形生成方法及其计算机实现

把面向对象技术应用于分形的演化生成,提出了一种基于对象演化的分形生成方法;讨论了两类基本对象──几何对象和符号对象的描述形式及其演化过程;介绍了基于对象演化生成分形的计算机实现;上机结果表明,这是一种有效的分形生成方法．     

矢量控制感应电机参数变化的影响研究

在感应电机数学模型的基础上，分析了在转子磁场定向恒磁通矢量控制感应电机控制系统中转子电阻和电机电感变化的影响，证明了电机电感的变化对电机转速和电磁转矩不产生影响，建立了考虑电机参数变化时电机矢量控制的数学模型，仿真结果表明该模型具有结构简单和分析方便等优点。     

Chemotaxonomy of the rutaceae—XII: The occurrence of severine in Atalantia monophylla and Hesperethusa crenulata. A revised structure for severine

Severine palmitate has been isolated from the fruit of Atalantiamonophylla and Hesptrethusacrenulata both of the family Rutaceae. NMR shift reagent and mass spectral studies suggest the need for revision of the structure of severine to 2. The revised structure is confirmed by the ¹³C NMR spectra of severine and its derivatives.