筒仓效应观测仪的设计及其应用

设计并制作了观测静态颗粒物质筒仓效应的实验系统,应用该装置研究了筒仓效应的尺寸依赖性.实验结果表明:圆柱形容器中的颗粒物质对于容器底部的饱和压力依赖于容器直径的3次方,而改变填入颗粒的直径时则饱和压力并无明显改变.     

固体材料反斯托克斯荧光制冷的理论研究及其最新进展

本文首先回顾了反斯托克斯荧光制冷的历史发展,简单讨论了激光制冷的循环过程及其制冷条件;其次,概述了反斯托克斯Raman散射、反斯托克斯荧光制冷的热力学理论和热力学限制,重点介绍了适用于各种制冷材料(如稀土离子掺杂玻璃、半导体和晶体等)反斯托克斯荧光制冷研究的理论模型,并简单讨论了激光制冷实验中各种测量温度变化的实验方法及其基本原理。最后,就反斯托克斯荧光制冷的一种最新应用及其前景进行了简单介绍与展望。     

Effect of composition,thickness and temperature on non-linear I–V curves in vanadium phosphate glasses

Summary Glass layers of (V₂O₅)_1−x (P₂O₅) _x were prepared by melting appropriate mixtures of V₂O₅ and P₂O₅ powders. The measurements ofI–V characteristic curves show three regions of conduction, namely high-resistance state, turnover point with zero-differential resistance region (∂V/∂I=0) and differential negative-resistance region. The turnover point is strongly dependent on composition, sample thickness and temperature. It is found that the increase of the ratio of phosphorus/vanadium reduces conductance as well as it raises the field required to produce turnover behaviour. The data in the range up to the turnover point are discussed on the basis of an electrothermal process. Results of the negative-resistance state could be explained in terms of a hopping mechanism.     

连续CO2激光对红外窗口材料损伤研究

研究了连续ＣＯ２激光对几种红外窗口材料的表面损伤特性，研究表明，损伤机制在于杂质缺陷吸收造成的热冲击应力破坏。深入研究了杂质缺陷密度、焦斑与材料损伤阈值的关系，并建立了一个损伤模型。同时分析了热冲击应力破坏方式。     

用于预测疏松材料冲击压缩特性的热力学模型

 在一定的假设条件下，从基本的热力学关系出发，导出了一个新的物态方程表达式。利用这一新形式特态方程所建立的热力学模型，可预测疏松材料的冲击压缩行为。以低、中、高冲击阻抗的铝、铜和钨为示例，将本模型的理论计算曲线与实验冲击压缩数据比较，表明本模型的在宽广的压力范围内具有良好的普活性；对不同初妈密度，疏松材料的冲击压缩行为均显示出较为满意的理论经历测能力；与现有的其它疏松材料物态方程模型相比，本模型在理论上和实际应用中均具有较大的优越性。     

食品微生物对超高压处理的逆境响应

 超高压（High Hydrostatic Pressure,HHP）作为一种非热杀菌技术,在食品工业中有着很广泛的应用,与传统的热加工处理相比,在保持食品品质、杀菌、钝酶等方面都有其明显的优势。通过对国内外相关文献的分析,对HHP处理后处于亚致死状态食品微生物的细胞膜、遗传与结构物质、机体代谢等方面,以及大部分食品微生物在应对外界的多种刺激时而进行的普遍性调控机制的研究进行了总结,探讨了经过HHP处理后处于亚致死状态的食品微生物在逆境下存活的应激反应。     

Bessel and annular beams for materials processing

Non‐Gaussian beam profiles such as Bessel or annular beams enable novel approaches to modifying materials through laser‐based processing. In this review paper, properties, generation methods and emerging applications for non‐conventional beam shapes are discussed, including Bessel, annular, and vortex beams. These intensity profiles have important implications in a number of technologically relevant areas including deep‐hole drilling, photopolymerization and nanopatterning, and introduce a new dimension for materials optimization and fundamental studies of laser‐matter interactions.     

Hydrothermal synthesis and characterization of ZnS hierarchical microspheres

In the present work, wurtzite ZnS hierarchical microsphere nanostructures composed of nanowires were synthesized through hydrothermal method. The morphologies and microstructures of the as obtained wurtzite ZnS sample were investigated by scanning electron microscopy and transmission electron microscopy. The results show that the diameter of the nanowires is about 10 nm, the length is about 500 nm, growing along the [0 0 1] direction. UV–visible spectroscopy shows that the band gap of the as obtained ZnS hierarchical microspheres is 3.4 eV. Room temperature photoluminescence measurements reveals a strong green emission peak at around 516 nm. The N₂ adsorption–desorption isotherms experiment at 77 K exhibits that the surface area of the ZnS sample is 99.87 m² g⁻¹.     

Effect of Al incorporation on the structural,morphological, optoelectronic and transport properties of PbS thin films

Doping of PbS thin films with different metal atoms produce considerable changes in structural and material properties that make them useful in the technology of thin film devices. The goal of this work is to study the effects of doping on the structural, morphological, optoelectronic and transport properties of PbS thin films as a function of Al³⁺ concentration. Thin films of pure and Al doped PbS nanoparticles are prepared on soda lime glass substrates by chemical bath deposition technique. The Al content in aqueous solution is varied from 0 to 20 mg. XRD analysis of the films revealed significant enhancement in crystallinity and crystallite size up to an optimum concentration of doping. Films are polycrystalline with crystallite size 19–32 nm, having face centered cubic structure. The optical band gap energy exhibits a decreasing trend and is shifted from 2.41 to 1.34 eV with increasing Al content. The room temperature conductivity of the as-deposited PbS films is in the range of 0.78×10⁻⁸ to 0.67×10⁻⁶(Ω cm)⁻¹ with a maximum for optimum Al content. The Al doped PbS thin film, which we synthesize with optimum Al concentration of 15 mg is found to be a most suitable material for solar control coating applications.     

Tuning exchange bias through zero field cooling from different remanent states above blocking temperature in Ni50Mn36Sb14 alloy

Changing remanent states above blocking temperature (T_B) in Ni₅₀Mn₃₆Sb₁₄ alloy has been proven to be an effective way of tuning the value and sign of exchange bias (EB) field. The hysteresis loops at 5 K exhibit double shifted shape, indicating that there are two opposite EB signs resulting from an imprint of domain pattern of ferromagnetic (FM) regions into anti‐ferromagetic (AFM) ones during cooling. All the results demonstrate that the interfacial spin configuration plays a crucial role on the origin of EB, while the high cooling field not only induces a single FM domain state above T_B but also tunes the fractions of FM and AFM interactions through martensitic transition. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)