Stress evolution and lattice distortion induced by thickness variation and lattice misfit in La0.67Sr0.33MnO3−δ films

La_0.67Sr_0.33MnO_3?δ thin films with different thicknesses are prepared in order to investigate the structural variation induced by film thickness and lattice misfit. The X-ray diffraction results show the in-built stress evolution from a full strained thin layer (～10 nm) to a completely relaxed thick layer (～150 nm), which can be well explained by the Poisson effect. Raman spectroscopy measurements reveal the complicated correlation between the Jahn–Teller (JT) distortion and film thickness. Important octahedron modes reflecting JT distortion are completely caused by the relaxed layer. It is observed that broad JT bands are formed in the films with large thickness of the relaxed layer and the residual stress in the layer leads to an obvious blue shift. In contrast, for films with the thin relaxed layer, JT modes are present as a sharper structure and move to low frequency, indicating towards a much better oxygen stoichiometry.     

Microstructure and high-temperature corrosion behaviors of aluminide coatings by low-temperature pack aluminizing process

Aluminide coatings were produced on carbon steel and Fe-5Cr-Mo alloy at a relatively lower temperature below 600 °C in shorter treatment time by a combination of surface refinement process and pack aluminizing process. Repetitive ball impact, generated by mechanical vibration, caused the top-layer refinement of substrates in a conventional pack aluminizing process. The effects of temperature and treatment time on the formation of aluminide coatings were analyzed. The microstructure of the coatings was investigated by SEM, AFM and XRD. The aluminide coatings were one-layer, compacted structure with ultrafine grains and uniform elemental distribution. High-temperature oxidation and sulphidation tests were carried out at 600 °C in air for 200 h and 10% SO₂ + Ar gas mixture atmosphere for 50 h, respectively. The mass gains and spallation indicated that the aluminide coatings significantly improved the high-temperature oxidation and sulphidation resistance.     

Deposition of quasi-crystal Al-doped ZnO thin films for photovoltaic device applications

Quasi-crystal aluminum-doped zinc oxide (AZO) films were prepared by in situ radio frequency (RF) magnetron sputtering (sputtering without annealing) on glass substrates. The influence of deposition parameters on the optoelectronic and structural properties of the in situ deposited quasi-crystal AZO films was investigated in order to compare resulting samples. X-ray diffraction (XRD) patterns show that the quasi-crystal AZO thin films have excellent crystallization improved with increase of the RF power and substrate temperature, with an extremely preferential c-axis orientation exhibit sharp and narrow XRD pattern similar to that of single-crystal. Field emission scanning electron microscopy (FESEM) images show that quasi-crystal AZO thin films have uniform grains and the grain size increase with the increase of RF power and substrate temperature. Craters of irregular size with the columnar structure are observed in the quasi-crystal AZO thin films at a lower substrate temperature while many spherical shaped grains appeared at a higher substrate temperature. The average optical transmittance of all the quasi-crystal AZO films was over 85% in the 400-800 nm wavelength range. The resistivity of 4.176 × 10⁻⁴ Ω cm with the grain size of 76.4891 nm was obtained in the quasi-crystal AZO thin film deposited at 300 °C, under sputtering power of 140 W.     

Core/shell structured ZnO/SiO2 nanoparticles: Preparation, characterization and photocatalytic property

ZnO nanoparticles were prepared by a simple chemical synthesis route. Subsequently, SiO₂ layers were successfully coated onto the surface of ZnO nanoparticles to modify the photocatalytic activity in acidic or alkaline solutions. The obtained particles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectrometry (EDS) and zeta potential. It was found that ultrafine core/shell structured ZnO/SiO₂ nanoparticles were successfully obtained. The photocatalytic performance of ZnO/SiO₂ core/shell structured nanoparticles in Rhodamine B aqueous solution at varied pH value were also investigated. Compared with uncoated ZnO nanoparticles, core/shell structured ZnO/SiO₂ nanoparticles with thinner SiO₂ shell possess improved stability and relatively better photocatalytic activity in acidic or alkaline solutions, which would broaden its potential application in pollutant treatment.     

A class of permutation quadrinomials

In this paper, we investigate the permutation behavior of a class of quadrinomials. Each term of these quadrinomials has a Niho-type exponent, and two sets of coefficient triples making the quadrinomials to be permutations are obtained. We use a substitution to transform the permutation problem into the root distribution problem in the unit circle of certain quadratic and cubic equations.     

Wavelet estimations for mixed densities under multiplicative censoring

Using compactly supported wavelets, Chaubey et al consider L²-risk estimation for mixed density under multiplicative censoring (Chaubey YP, Chesneau C, Doosti H. Adaptive wavelet estimation of a density from mixtures under multiplicative censoring. Statistics, 2015, 49: 638-659). In this paper, we try to discuss L^p-risk (1 ≤ p<∞) estimation for that statistical model of the linear and nonlinear wavelet estimators respectively. Our results can be seen as an extension of the work of Chaubey et al.     

基于熵值法和神经网络模型的股价评估分析

股票价格的变化主要依赖于两个方面,一个是股票内在价值,另一个就是系统风险对股票价值的影响.通过使用神经网络的方法来分析股票的系统风险,用熵值法来分析股票的内在价值,从而全面的分析股票的投资价值,结果表明这种评估方法是可靠并且具有较大的获利空间.     

PCS-环与扩张

结合ACS环和p.q-Baer环的定义,本文将p.q-Baer环推广到PCS环,这样在p.q-Baer环和ACS环之间存在一类新的环,PCS环.环R称为PCS-环,如果R的每个主理想的右零化子作为右理想在一个由幂等元生成的右理想中是本质的.PCS-环包括所有的右p.q-Baer环,所有的右FI-扩展环,以及所有的交换的ACS-环.通过研究环主右理想的零化子的性质和模的本质子模的性质,研究了三种环之间的关系,推广了p.q-Baer环的结果,得到了ACS环所没有的结果,同时研究了环的扩张问题,证明了强PCS性质是Morita等价性质.     

Hamilton–Souplet–Zhang's gradient estimates and Liouville theorems for a nonlinear parabolic equation

In this paper, we study Hamilton–Souplet–Zhang's gradient estimates for positive solutions to the nonlinear parabolic equation

$u_t=\mathrm{\Delta }u+\lambda u^{\alpha }$

on noncompact Riemannian manifolds, where $\lambda ,\alpha$ are two real constants. As an application, we obtain a Liouville-type theorem.     

The mean curvature flow in Minkowski spaces

Studying the geometric flow plays a powerful role in mathematics and physics. In this paper, we introduce the mean curvature flow on Finsler manifolds and give a number of examples of the mean curvature flow. For Minkowski spaces, a special case of Finsler manifolds, we prove the short time existence and uniqueness for solutions of the mean curvature flow and prove that the flow preserves the convexity and mean convexity. We also derive some comparison principles for the mean curvature flow.