Pulsed laser deposition of NiTi shape memory effect thin films

2 O₃(100) substrates. We also produced free-standing NiTi films by deposition on KBr substrates and subsequent substrate removal by immersion in water. The presence of the solid-solid phase transformation responsible for the shape memory effect has been demonstrated through temperature-dependent X-ray diffraction and four-probe resistance versus temperature measurements. On cooling the deposited film, the austenite-martensite transformation was measured at around 195 K; on heating the film the reverse transformation was around 250 K. Evidence of the shape-memory effect for free-standing films was obtained in a bending deformation-shape recovery experiment. Received: 31 July 1996/Accepted: 6 January 1997     

非饱和土-隧道系统动力响应计算的波函数法

针对非饱和地基土中埋置隧道的三维动力响应计算问题, 提出了波函数法.采用无限长的Flügge薄壁圆柱壳模拟圆形隧道衬砌,采用流、固、气组成的三相介质模拟非饱和地基土体.分别采用分离变量法以及Helmholtz矢量分解定理求解薄壁圆柱壳的振动控制方程与非饱和土的波动方程.根据隧-土交界面与地表面处的应力、位移以及孔隙流体压力等边界条件,利用平面波与柱面波的转换性质,实现了隧道内作用单位简谐载荷时隧道衬砌与土体系统动力响应的耦合求解.通过与既有单相弹性介质2.5维有限元-边界元法、两相饱和多孔介质2.5维有限元-边界元法以及三相非饱和介质Pip in Pip半解析法的计算结果进行对比, 验证了本文计算方法的可靠性. 最后,基于该方法, 通过算例分析了不同饱和度下非饱和土-隧道系统的动力响应特征.结果表明, 饱和度对土体动位移与超孔隙水压力的幅值响应有较大影响.该方法的非饱和地基土参数退化后,也可用来计算和分析饱和地基土或单相弹性地基土与隧道系统的动力响应.      

The Effect of Methylammonium Iodide on the Supersaturation and Interfacial Energy of the Crystallization of Methylammonium Lead Triiodide Single Crystals

It is very important to study the crystallization of hybrid organic–inorganic perovskites because their thin films are usually prepared from solution. The investigation on the growth of perovskite films is however limited by their polycrystallinity. In this work, methylammonium lead triiodide single crystals grown from solutions with different methylammonium iodide (MAI):lead iodide (PbI₂) ratios were investigated. We observed a V‐shaped dependence of the crystallization onset temperature on the MAI:PbI₂ ratio. This is attributed to the MAI effects on the supersaturation of precursors and the interfacial energy of the crystal growth. At low MAI:PbI₂ ratio (<1.7), more MAI leads to the supersaturation of the precursors at lower temperature. At high MAI:PbI₂ ratio, the crystal growing plans change from (100)‐plane dominated to (001)‐plane dominated. The latter have higher interfacial energy than the former, leading to a higher crystallization onset temperature.     

VIBRATION AND STABILITY OF RING-STIFFENED THIN-WALLED CYLINDRICAL SHELLS CONVEYING FLUID

Based on the Flügge shell theory,equations of motion of ring-stiffened thin-walled cylindrical shells conveying fluid are developed with the aid of the Hamilton's principle.Analysis is carried out on t...