Estimation of growth rate in unidirectionally solidified multicrystalline silicon by the growth-induced striation method

Multicrystalline silicon was grown by unidirectional solidification method using the accelerated crucible rotation technique. The application of the accelerated crucible rotation technique in unidirectional solidification method induced growth striations across the axial direction of the grown crystal. This striation pattern was observed from carbon concentration distribution, obtained by using Fourier transform infrared spectroscopy. The generated striation pattern was found to be weak and discontinuous. Some striations were absent, probably due to back melting, caused during each crucible rotation. From the growth striations and applied time period in crucible rotation, the growth rate was estimated by using Fourier transformation analysis.     

Effects of Salt on the Orientational Order in Decylammonium Chloride/Ammonium Chloride/Water Systems

The effect of NH₄Cl on the temperature dependence of deuterium oxide splitting (water order) and proton line width (surfactant order) in decylammonium chloride (DACl), D₂O systems is reported. The molar ratio of DACl to D₂O was held constant at .085 and the molar ratio of NH₄Cl to D₂O was varied from .012 to .029. We find for the above concentration ranges that in the nematic range the relative temperature dependence of the D₂O splitting is little affected by changes on salt concentration. The slopes of the proton line widths as a function of temperature decrease with increasing salt concentration. The results are compared with earlier data on salt effects on order obtained with the disodium cromoglycate system.     

由三平行轴惯量求重心的一种方法

为了求得复杂刚体重心的位置, 根据转动惯量平行轴定理, 由已知轴转动惯量和一定的几何关系推导出用于求重心的关系式, 从理论上给出两个可能重心坐标值, 再实际判断取舍.只要用实验仪器先测量刚体对3个平行转轴的转动惯量, 就可由该关系式计算得到刚体重心的位置. 这一方法有时要比直接测量重心更为简单.     

一个有趣的力学实验

介绍一种由矿泉水瓶制作奇异转动的力学实验, 用两个互相垂直的简谐振动的合成来解释其转动的原理, 制作模型并进行验证, 得出木棒摩擦矿泉水瓶时, 瓶盖上的叶片同时参与了两个不同方向的振动, 这两个振动合成的结果使得瓶盖上的叶片发生转动的结论.     

Advancements in subsea riser analysis using quasi-rotations and the Newton–Raphson method

Beam structures undergoing finite deflections and rotations in space have extensive application in the subsea industry particularly for the analysis of holistic systems with larger numbers of mooring and riser components. In using the finite element analysis approach, there is an increasing requirement for large element sizes which preserve accuracy with regard to the coupling of axial, bending and torsion response.The authors outline a method for improving the current state of practice for the analysis of riser systems. The approach draws on the convected coordinates method, Euler–Bernoulli beam theory, the principle of virtual work and the finite element method. Two quasi-rotation measures are developed including a quasi-material rotation definition for rotational deformation relative to the convected axis of a beam and a quasi-space rotation definition to deal with the path dependent nature of rotations in three dimensions.The novel aspect of this work is to relate the rate of change of the quasi-material rotation vector along the beam axis to a linear transformation of the beam axis rate-of-rotation vector through utilising the convected coordinates axes system. In this way, incremental values of quasi-material rotation are directly linked to incremental values of nodal quasi-space rotation and a global Newton–Raphson solution technique for interconnecting beam elements is straightforward to assemble.Furthermore, this leads to accurate definitions of coupled axial, bending and torque response for beams with significant deflection. The approach has particular advantages in the analysis of subsea riser sections. Also, the accuracy of the solution is preserved for a fewer number of elements compared to alternative solutions for computationally sensitive load cases with highly non-linear loading regimes.