Purification and magnetic properties of carbon nanotubes

Received: 5 January 1998     

Zn_（1－x）Mg_xS_ySe_（1－y）四元半导体合金的拉曼散射光谱研究

用分子束外延方法在ＧａＡｓ（１００）衬底上生长了Ｚｎ１－ｘＭｇｘＳｙＳｅ１－ｙ四元半导体合金薄膜．用Ｘ－射线衍射方法确定了外延层的结构和晶格常数．测量了这些样品在平行和垂直两种不同几何配置下的拉曼散射光谱并对其特性做了研究。从实验上观察到了四类不同的晶格振动模：类ＺｎＳｅ的ＴＯ和ＬＯ模以及类ＺｎＳ和类ＭｇＳ的ＬＯ模，实验发现：在ＺｎＳｅ和ＺｎＳＳｅ中加入Ｍｇ使得类ＺｎＳｅ的ＴＯ和ＬＯ模的振动频率下降；同时，也使类ＺｎＳ模的频率随Ｓ的增加率减小。     

Nanosecond-time-resolution thermal emission measurement during pulsed excimer-laser interaction with materials

A nanosecond-time-resolution pyrometer has been developed for measuring the transient surface temperature of a solid material heated by pulsed excimer-laser irradiation. Fast germanium diodes are employed to capture the transient thermal emission signals in the wavelength range between 1.2 and 1.6 pm. The surface temperature is derived from the measured spectral thermal emission. The directional spectral emissivity is determined in situ by measuring the transient directional spectral reflectivity and applying Kirchhoffs law. The experimental results are in good agreement with numerical thermal modeling predictions. The pyrometric thermal emission measurement also yields the solid/liquid interface temperature during the pulsed excimer-laser-induced melting. The relation between the measured interface superheating temperature and the interface velocity reveals the melting kinetic relation during the high-power, short-pulse laser-induced phase-change processes.     

A boundary integral formulation for elastically deformable particles in a viscous fluid

This paper reports a formulation and implementation of a mixed (both direct and indirect) boundary element method using the double layer and its adjoint in a form suitable for solving Stokes flow problems involving elastically deformable particles. The formulation is essentially the Completed Double Layer Boundary Element Method for solving an exterior traction problem for the surrounding fluid or solid phase, followed by an interior displacement, and a mobility problem (if required) for the elastic particles. At the heart of the method is a deflation procedure that allows iterative solution strategies to be adopted, effectively opens the way for large-scale simulations of suspensions of deformable particles to be performed. Several problems are considered, to illustrate and benchmark the method. In particular, an analytical solution for an elastic sphere in an elongational flow is derived. The stresslet calculations for an elastic sphere in shear and elongational flows indicate that elasticity of the inclusions can potentially lead to positive second normal stress difference in shear flow, and an increase in the tensile resistance in elongational flow.This work is supported by a grant from the Australian Research Grant Council. X-J F wishes to acknowledge the support of the National Natural Science Foundation of China.     

Convex composite multi-objective nonsmooth programming

This paper examines nonsmooth constrained multi-objective optimization problems where the objective function and the constraints are compositions of convex functions, and locally Lipschitz and Gâteaux differentiable functions. Lagrangian necessary conditions, and new sufficient optimality conditions for efficient and properly efficient solutions are presented. Multi-objective duality results are given for convex composite problems which are not necessarily convex programming problems. Applications of the results to new and some special classes of nonlinear programming problems are discussed. A scalarization result and a characterization of the set of all properly efficient solutions for convex composite problems are also discussed under appropriate conditions.This research was partially supported by the Australian Research Council grant A68930162.This author wishes to acknowledge the financial support of the Australian Research Council.     

LEED crystallographic investigation of ultrathin films formed by deposition of Sn on the Pt(111) surface

Deposition of Sn on the Pt(111) surface followed by annealing at 1000 K leads to the formation of ordered phases showing (2 × 2 and ( LEED patterns, depending on the surface coverage of Sn. Both these phases were studied by LEED dynamical analysis. The best agreement between experimental and calculated I–V curves was obtained by means of models based on the formation of mixed Pt-Sn layers on the surface where Pt and Sn atoms are nearly coplanar with a slight upward buckling of Sn atoms. The structures of these phases are similar to those already observed for the Pt₃Sn(111) surface.     

掺杂纳米半导体超微粒ZnS:Mn2+光学特性研究

九十年代对纳米尺寸(nanoscale)材料的光物理性质的深入研究,导致了介于微观与宏观物理间的新的学科一介观物理(mesoscopic physics)的产生.其科学义在于建立和发展介于原子分子和固体之间所谓介观系统(mesoscopic system)的量子理论,揭示介观物质特性及其相互作用本质,并利用介观特性探索新型结构和功能材料.以往对纳米半导体超微粒材料的研究主要集中于与本征特性相关的量子尺寸效应,或缺陷对超微粒本征特性的影响[1,2].超微粒中过渡金属离子中心发光性质研究首次报道于1993年[3,4]并指出这可能成为崭新的一类发光材料.