NiTi形状记忆合金激光气体氮化层表面特征

为改善NiTi合金的表面性能，利用2kW连续波Nd：YAG对NiTi合金进行激光气体氮化处理。采用SEM、TEM、XRD、XPS和纳米压痕研究了氮化层的显微组织及表面特征．结果表明：激光气体氮化可以在NiTi合金表面制备连续、无裂纹、厚度为2μm的TiN表面层，该表面层中基本不合有Ni元素且具有很高的硬度，其纳米压痕硬度为29．28GPa．     

Heat transfer mechanism of a swirling impinging jet in a stagnation region

Heat transfer characteristics of a swirling impinging jet have been experimentally examined using a combined particle image velocimetry (PIV) and laser‐induced fluorescence (LIF) technique for simultaneous measurement of velocity and temperature fields. The present study shows that the radial width of the jet stretches with increasing swirl intensity, and that the stretching phenomenon contributes to the maximum local heat transfer coefficient. At the stagnation region, the flow near the heated surface is mixed intermittently by reverse flows toward upstream, and spatial distributions of temperature are correlated with instantaneous velocity vector maps. The dynamic behavior of recirculation zones, attributed to swirl number Sw and impinging distance, mainly determines the turbulent heat transfer at the stagnation region. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(8): 663–673, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10120     

金属—PAN—S配合物的极谱研究——Ⅱ:Fe~(3+)—PAN—S—TEA—NH_3·H_2O—NH_4Cl体系配合吸附波

在NH_3·H_2O—NH_4Cl—三乙醇胺底液中Fe(Ⅲ)与PAN—S产生一灵敏的配合吸附波,峰电位在—0.50伏(vs.SCE)。峰电位与铁离子浓度在2.8×10~8～3.4×10~(-6)mol/L范围内线性良好,检出下限可达2.8×10~(-8)mol/L。该法用于乳粉、头发、血清等样品的测定,结果满意。     

Changes in polymer foils used in food packaging tested by using differential scanning calorimetry

This work is an experimental study of the differential scanning calorimetry characterisation of polymer materials used in food packaging materials, such as polypropylene (0.03 mm), polyethylene (0.1 and 0.03 mm), poly(D-(-)-Β-hydroxybutyrate) (powder), two-layered polypropylene (0.064 mm), and two-layered polypropylene with poly-vinylidene-chloride (0.012/0.021). The polymer stability was checked by simulation of conditions during food preparation in microwave ovens, sterilisation or rapid freezing. The materials were tested in the temperature range from 40 to 200‡C at different scan rates from 2 to 30°C min⁻¹ during heating or cooling. The enthalpies show a high correlation coefficient (0.964) with scan rate. All samples undergo phase change in the temperature range from 107 to 173°C during heating and enthalpies are in the range from 31.8 to 71.1Jg⁻¹. Upon subsequent cooling from 200°C, the temperature range of phase changes is shifted to lower temperatures from 86 to 102°C with enthalpies ranging from 30.4 to 57.8 J g⁻¹. Experiments with exposure of polymers to microwave radiation and freezing prove that the phase change considering the temperature range is very similar in all experiments.     

星间激光通信技术进展与趋势

较详细地评述了目前国外卫星间光通信技术研究的现状．根据关键单元技术的进展情况，总结了未来星间光通信系统的发展趋势。     

基于SPM技术的纳米信息存储薄膜的研究进展

扫描探针显微技术SPM可以在原子或分子尺度上对表面进行表征和修饰，应用SPM技术可以在薄膜表面形成纳米级的信息点阵，特别适合发展超高密度的信息存储，是一种非常有希望代替传统磁存储，光存储的纳米级存储技术，本文介绍了纳米信息存储薄膜的研究进展，并对其制备技术和读写机制进行了初步的探讨。     

激光二极管线阵光束变换研究

推导出激光二极管线阵光束通过透镜系统的光强分布表达式，分析了出射光束的传输特性，设计一种凹柱透镜的光束变换系统得到一维均匀光强分布。此外，给出扩展角宽度的计算公式。     

固定频率波束可调的多端口微带漏波天线

提出了一种崭新结构的多端口馈电微带漏波天线 ,实现了频率固定下的电控天线主波束逐级可调。在工作频率固定的情况下 ,通过控制双端口馈电微带天线上的中部馈电端口位置 ,使微带漏波天线主波束方向发生偏移。仿真结果表明 ,当工作频率固定为 7GHz的情况下 ,在H平面上 ,主波束扫描范围可以达到约 48°～ 88°。     

A study of the large strain deformation and failure behaviour of mixed biopolymer gels via in situ ESEM

A mixed biopolymer gel, consisting of a protein (gelatin) and polysaccharide (maltodextrin) mixture has been investigated. By controlling the composition it was possible to construct an ‘emulsion-like’ structure, with included spherical particles of one phase (maltodextrin) within a continuous matrix of the second (gelatin). Large strain deformation and failure behaviour of this system has been examined via in situ environmental scanning electron microscopy (ESEM). ESEM has been employed to explore the changes in the structure of the material, whilst allowing the sample to stay hydrated as it was subjected to tensile strain, thereby allowing simultaneous imaging and determination of stress-strain data of the native sample. Ductile behaviour was observed, which has been attributed to the stretching, tearing and fracture of gelatin ligaments and debonding at the interface between the maltodextrin particles and continuous gelatin matrix. Deformation and fracture of the maltodextrin particles during tensile testing was also observed. The interfacial fracture energy of the composite has been calculated following an elastomer composite-debonding model, although there are several limitations to this approach for the mixed gel. It was found in samples tested after different ageing times that the debonding stress and strain was decreasing with ageing leading to a lower interfacial fracture energy. Samples were also tested after successive loading cycles, which resulted in a mechanical strength decrease after each cycle.     

基于CCD的激光微位移测量系统研究

介绍了一种基于多普勒效应的可进行动态微位移测量的激光微位移测量系统。该系统以He-Ne激光器为光源,配以干涉系统移动方向判别及分频系统、CCD视频信号的高速动态采集系统、微机处理系统及干涉图处理软件包等。与传统测量方法相比,其精度、灵敏度及稳定性都有较大提高,并实现了微位移的全自动测量。