Hexane dehydrogenation to hexenes: a general indicator for deactivation of Pt catalysts in “skeletal” reactions

The comparative evaluation of dehydrogenation yields and selectivities of skeletal reactions from n-hexane reactions on monofunctional Pt catalysts is a good universal indicator of catalyst deactivation, independently of the presence and the nature of the support. Four regions could be defined with increasing carbon accumulation, causing "beneficial", "selective", "nonselective" and "severe" deactivation.     

Lamb wave tomography of pipe-like structures

Lamb waves are guided ultrasonic plate waves that can follow the curvature of pipe-like structures. By transmitting and receiving many helically propagating Lamb waves via longitudinal transducers in contact with the surface of a pipe, crosshole tomographic geometries can be mimicked and tomographic reconstructions performed in order to locate and size flaws. We describe here a meridional-array scheme which mimics a single line of transducers along the exterior surface of the pipe in the axial direction, and show proof of concept results on a pipe sample with an internal wall-thinning. We also demonstrate improved reconstructions for the other helical ultrasound tomography geometry where the transmitters and receivers lie along parallel circumferential rings. We find frequency compounding smoothes out some of the noise and artifacts that appear in the reconstructions.     

Influence of Deviation on Optical Transmission through Aperiodic Superlattices

We propose a deviation model and study the influences of the relative error and sensitivity of a machine on the transmission coefficients （TCs） of Fibonacci superlattices. It is found that for a system with fewer layers, the influence of deviation can be ignored. When superlattices become more complicated, they may be fabricated by a machine with suitable relative error and possess the designed value of TO. However, when the number of system layers exceeds some critical value, superlattices should be manufactured only by precise machines. The influence of the sensitivity is also discussed.     

Inverse relation between photocurrent and absorption layer thickness in polymer solar cells

Organic solar cells based on polymer–fullerene bulk heterojunctions were optimised with respect to the short circuit photocurrent by means of optical modelling. Due to interference effects present in the thin film multilayer device, an inverse relation between active layer thickness and photocurrent was predicted and experimentally verified. Optimised photovoltaic devices yield power conversion efficiencies of 4%. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

表面杂质对NO+CO/Pt(100)反应体系振荡动力学的影响

提出了一个格气模型， 探讨催化表面的惰性杂质对NO+CO/Pt(100)反应体系振荡动力学行为的影响．研究发现表面杂质较少时，反应进程中表面重构能够形成相连通的1*1相和持续的振荡行为．当表面杂质不断增加时，反应进程中1*1相只能形成许多孤立的畴，从而在1*1相形成的随机的局域振荡的空间关联被削弱，因而体系全局的持续振荡行为演变为衰减振荡行为．当表面吸附的CO和NO的扩散速率增加时，局域振荡的空间协同又得到加强，体系又呈现出持续振荡行为．     

Growth kinetics of metastable (3 3 1) nanofacet on Au and Pt(1 1 0) surfaces

A theoretical epitaxial growth model with realistic barriers for surface diffusion is investigated by means of kinetic Monte Carlo simulations to study the growth modes of metastable (3 3 1) nanofacets on Au and Pt(1 1 0) surfaces. The results show that under experimental atomic fluxes, the (3 3 1) nanofacets grow by 2D nucleation at low temperature in the submonolayer regime. A metastable growth phase diagram that can be useful to experimentalists is presented and looks similar to the one found for the stationary growth of the bcc(0 0 1) surface in the kinetic 6-vertex model.     

Fabrication of electrode Pt nanotubes for semiconductor capacitors

Template-wetting process was used to fabricate Pt electrode nanotubes for the further application in 3D nanotube capacitors. Anodic alumina oxide (AAO) was used as a template, which can be fabricated by means of two-step anodization process. After the wetting process, released Pt nanotubes have been obtained by selective etching of the template using KOH solution. Pt nanotubes formation and tube walls morphology were investigated by FE-SEM technique. Furnace annealing (FA) effects at temperatures ranging from 200 to 600 °C with 100^oC step on nucleation and crystal growth condition of Pt nanotubes have been examined. Crystallization of the Pt nanotube inside the template has been examined by step-by-step annealing at different temperatures, and confirmed by XRD.     

Spin-orbit-like terms in semileptonic weak Hamiltonian

It is shown that new spin-orbit-like terms appear in the effective nonrelativistic weak Hamiltonian for nucleon provided that nuclear potential is taken into account. Arguments for their considerable enhancement, in particular, in relativistic nuclear model of Walecka are advanced. Received: 29 July 1999     

双核铂的Pt2（CN）4（CNC4H9）4的发光机制及Pt...Pt间互作用的从头计算研究

利用从头算ＭＰ２方法优化了Ｐｔ（ＣＮ）２（ＣＮＣＨ３）２，Ｐｔ（ＣＮ）２（ＣＮＣＨ３）２－（ＮＣＣＨ３）２．「Ｐｔ（ＣＮ）２．（ＣＮＣＨ３）２」２的在态几何结构，利用单激发的组态相互作用方法（ＣＩＳ）计算了固态和乙氰溶液中标题化合物的发射光谱，并对激发态的几何结构进行了优化，结果表明，基态时，Ｐｔ．．．ＮＣＣＨ３之间的距离较大（０．４０６ｎｍ），说明溶剂分子与Ｐｔ原子之间存在较小的范德华作用；而激发时，Ｐｔ．．．ＮＣＣＨ３之间的距离减小（０．２５７ｎｍ），说明此时Ｐｔ．．．ＮＣＣＨ３之间相互作用较强，由于这种作用使乙氰溶液中该物质的发光性质与不考虑溶剂效应时相比差异较大，其发射光谱不可我谱区，固态时，此化合物为直线链状结构，ＭＰ２计算得到：基态时「Ｐｔ（ＣＮ）２（ＣＮＣＨ３）２」２中Ｐｔ．．．Ｐｔ之间的距离为０