Enhanced room temperature ferromagnetism and photoluminescence behavior of Cu-doped ZnO co-doped with Mn

Cu, Mn co-doped ZnO nanoparticles were successfully synthesized by the sol–gel technique. XRD pattern described that Mn-doping did not affect the hexagonal wurtzite structure of the samples and no secondary phases were found. The reduced crystallite size at Mn=2% is due to the suppression of grain surface growth by foreign impurity. The enhancement of crystal size after Mn=2% is due to the expansion of lattice volume produced by the distortion around the dopant ion. The better dielectric constant and conductivity noticed at Mn=2% are explained by charge carrier density and crystallite size. The suppression of broad UV band by Mn-doping is discussed based on the generation of non-radiative recombination centers. Hysteresis loop showed the clear room temperature ferromagnetism in all the samples and the magnetization increased with Mn-doping. Better electrical and magnetic behavior of Zn_0.94Cu_0.04Mn_0.02O sample is suggested for effective opto-magnetic devices.     

Aharonov–Bohm effect in non-uniform crater-like quantum dot with double rim

We study electron energies in a double concentric quantum ring with anisotropy in the rims heights in the presence of the external magnetic field applied along the symmetry axis. To this end, we consider a model in which the thickness grows linearly from the axis up to the inner rim with a slope different from one between the inner and the outer rims. The anisotropy in the rims heights originated by the presence in the structure of various valleys we simulate by periodic dependence of the slope on the radial direction. We show that the wave functions of the electron confined in such structure can be found analytically if the slopes in all radial directions are the same, and by using a simple exact diagonalization procedure otherwise. The behavior of the electron energies as functions of the magnetic field, rings radii and rims heights, as well as the number of the valleys and their depths is consistently described with our formalism. The entanglement of the states with different radial and orbital quantum numbers, the period and the amplitude of the Aharonov–Bohm oscillations are very sensible to any variations of the rims heights.     

Progress in improving thermodynamics and kinetics of new hydrogen storage materials

Hydrogen storage material has been much developed recently because of its potential for proton exchange membrane (PEM) fuel cell applications. A successful solid-state reversible storage material should meet the requirements of high storage capacity, suitable thermodynamic properties, and fast adsorption and desorption kinetics. Complex hydrides, including boron hydride and alanate, ammonia borane, metal organic frameworks (MOFs), covalent organic frameworks (COFs) and zeolitic imidazolate frameworks (ZIFs), are remarkable hydrogen storage materials because of their advantages of high energy density and safety. This feature article focuses mainly on the thermodynamics and kinetics of these hydrogen storage materials in the past few years.     

Radial basis functions collocation and a unified formulation for bending,vibration and buckling analysis of laminated plates,according to a variation of Murakami’s zig-zag theory

In this paper, we propose a variation of the use of Murakami’s zig-zag theory for the analysis of laminated plates. The new theory accounts for through-the-thickness deformation, by considering a quadratic evolution of the transverse displacement with the thickness coordinate. The equations of motion and the boundary conditions are obtained by the Carrera’s Unified Formulation, and further interpolated by collocation with radial basis functions. This paper considers the analysis of static deformations, free vibrations and buckling loads on laminated composite plates.     

基于投入产出方法的中国城乡居民收入分析

目前居民收入分配问题,特别是城乡居民收入差距问题已成为中国社会面临的需要高度重视和尽快解决的问题.在2007年全国投入产出表的基础上,利用多个部门的相关数据将我国居民收入划分为农村居民收入和城镇居民收入两个收入群体,对两个群体在各部门的收入分配情况进行了分析.同时,利用投入产出局部闭模型和宫泽乘数方法,对农村居民收入和城镇居民收入之间的拉动关系以及各部门最终需求的变动对农村和城镇居民收入的影响进行了定量分析.     

从客户视角研究微型付款模式对企业绩效的影响

基于客户资产理论,从客户视角研究微型付款模式影响企业绩效的机制进行研究.采用问卷设计和数据收集方式,研究共回收有效问卷2260份.通过对这2260份有效问卷进行信度和效度检验、描述性统计分析、相关分析和多元回归分析,对关于微型付款模式影响企业绩效的假设进行实证,找出客户视角微型付款模式影响企业绩效的机制.     

高频金融时间序列的模型化研究进展回顾

从高频和超高频金融数据的基本统计特征出发,回顾了(超)高频金融时间序列模型化研究的发展历程及相关特征,并详细介绍了高频数据模型研究中针对久期序列建立ACD模型族的研究与进展.对ACD模型族,介绍了两种主要类型:强ACD模型和弱ACD模型.最后展望了高频金融时间序列中ACD模型的研究.     

NIR-luminescence from ternary lanthanide [Ho, Pr and Tm] complexes with 1-(2-naphthyl)-4,4,4-trifluoro-1,3-butanedionate

The ligand 1-(2-naphthyl)-4,4,4-trifluoro-1,3-butanedionate (Htfnd) has been employed to synthesize six novel ternary-lanthanide complexes in which the synergic ligands were 1,10-phenanthroline-5,6-dione (dione) and 4,5-diazafluoren-9-one (dafone), respectively. Two series of complexes Ln(tfnd)₃dione and Ln(tfnd)₃dafone (Ln=Ho, Pr, Tm) were obtained. These complexes were characterized by elemental analysis, Fourier Transform Infrared spectra and diffused reflectance. After ligand-mediated excitation, Ln(tfnd)₃dione and Ln(tfnd)₃dafone all show the characteristic NIR luminescence of the corresponding Ln³⁺ ions (Ln=Ho, Pr, Tm). This can be attributed to the efficient energy transfer from ligands to central Ln³⁺ ions, via an antenna effect. The indirect energy transfer in the complexes has been investigated and the differences in the luminescence intensity between Ln(tfnd)₃dione and Ln(tfnd)₃dafone were discussed in detail. The excellent luminescent performances enable these NIR-luminescent complexes to have potential applications in optical amplification operating at 1300 or 1500 nm.