磁功能性TiO2光催化剂的制备及特性

采用溶胶-凝胶法以Fe₃O₄为磁核制备了磁功能性光催化剂,以甲基橙为模拟污染物,考察了掺杂Fe比例、催化剂煅烧温度以及煅烧时间对催化剂活性的影响.催化剂的最佳制备条件为:Fe₃O₄掺杂Fe含量为5%,煅烧温度为450 ℃,煅烧时间为2 h.通过TG-DTA、XRD、UV-Vis、TEM对催化剂进行了表征,结果表明:制备的催化剂具有明显的核壳结构,原Fe₃O₄磁核经过高温煅烧被氧化;TiO₂包覆在磁核表面;催化剂的吸收带边发生红移,在可见光区的吸收强度有所增强;催化剂颗粒的平均粒径为20 nm.     

多孔碳负载纳米TiO2光催化性能研究

采用溶胶-凝胶法在多孔碳表面负载纳米TiO2光催化剂.探讨了不同浸泡时间、热处理温度和热处理时间对样品光催化性能的影响.采用XRD、SEM和紫外-可见光分光光度测试手段对所制备的材料进行表征,并分析各因素对光催化性能的影响.SEM的分析结果表明TiO2是以颗粒或者层的形式覆盖到多孔碳的孔道结构上的,且负载情况良好;光催化正交优化实验得到了各因素对多孔碳负载TiO2光催化性能影响的主次顺序:浸泡时间＞热处理温度＞热处理时间;优化后的实验工艺方案为:浸泡时间60 min、热处理温度700℃、热处理时间60 min.     

Sm∶YAG晶体生长与吸收光谱研究

采用提拉法生长了掺杂3.0at;,5.0at;和10.0at;浓度的Sin∶ YAG晶体.采用ICP-AES方法初步测试了Sm离子在晶体中的浓度,并根据测试结果计算了Sm离子在晶体中的分凝系数,探讨了生长高掺杂浓度晶体的生长条件,测试了其在可见光及近红外光波段的吸收光谱.结果表明,Sin∶ YAG晶体在80 ～900 nm处几乎完全透明,在Nd∶ YAG晶体的发射波段,可有效吸收1064 nm的近红外光,且随着掺杂浓度的增加,其吸收效果越强.这表明Sin∶ YAG晶体对于高功率Nd∶ YAG激光器工作过程中产生的放大自发辐射现象引起的寄生振荡具有较好的抑制作用.     

一种考虑中介交易态度的买卖双边匹配决策方法

电子中介的出现,为商品交易提供新的交易平台。本文以基于电子中介下的商品交易为背景,研究了考虑不同中介交易态度的买卖双边匹配决策问题。首先,给出买卖双边匹配决策问题的描述,然后,根据牟利型、服务型和折中型等3种交易态度中介的特点,以最大化匹配对价值、交易价格和达成度等为目标,分别建立了3种中介下的买卖双边匹配模型。进一步地,通过求解上述模型确定双边买卖匹配决策的结果。最后,通过一个实例分析说明出方法的有效性和可行性。本文进一步完善了买卖双边匹配的决策方法,具有实际应用价值。     

Enhanced Kerr nonlinearity in a left-handed three-level atomic system driven by a bichromatic field

Enhanced Kerr nonlinearity in a left-handed atomic system consisting of three levels driven by a bichromatic field is presented in this paper.Based on bichromatic field coherence,the real parts of the permittivity and permeability can obtain negative values simultaneously in the same detuning frequency region.By adjusting the frequency difference and the Rabi frequencies of the bichromatic field,the multi-band left-handed behavior of the presented atomic metamaterial is exhibited.Meanwhile,the enhanced Kerr nonlinearity can be realized in this multi-band left-handed three-level atomic system.It is shown that the third-order susceptibility possesses focusing or defocusing properties in the same frequency band.     

Effect of elastic strain energy on grain growth and texture in AZ31 magnesium alloy by phase-field simulation

A phase-field model is modified to investigate the grain growth and texture evolution in AZ31 magnesium alloy during stressing at elevated temperatures. The order parameters are defined to represent a physical variable of grain orientation in terms of three angles in spatial coordinates so that the grain volume of different order parameters can be used to indicate the texture of the alloy. The stiffness tensors for different grains are different because of elastic anisotropy of the magnesium lattice. The tensor is defined by transforming the standard stiffness tensor according to the angle between the (0001) plane of a grain and the direction of applied stress. Therefore, different grains contribute to different amounts of work under applied stress. The simulation results are well-explained by using the limited experimental data available, and the texture results are in good agreement with the experimental observations. The simulation results reveal that the applied stress strongly influences AZ31 alloy grain growth and that the grain-growth rate increases with the applied stress increasing, particularly when the stress is less than 400 MPa. A parameter (△d) is introduced to characterize the degree of grain-size variation due to abnormal grain growth; the △d increases with applied stress increasing and becomes considerably large only when the stress is greater than 800 MPa. Moreover, the applied stress also results in an intensive texture of the 〈0001〉 axis parallel to the direction of compressive stress in AZ31 alloy after growing at elevated temperatures, only when the applied stress is greater than 500 MPa.     

YBa2Cu3O7-δ的低温摩擦学性能

随着超导体的出现,人们一直致力于超导摩擦学的研究,取得了显著的进步,但对其减摩抗磨机理还不清楚。该文利用相关资料,介绍了低温摩擦学的主要研究方法、重点总结了超导转变对高温超导陶瓷YBa2Cu3O7-δ摩擦行为的影响,并探讨了超导摩擦的机理。     

基于离散流的微全分析系统

针对基于连续流的微全分析系统的弊端,详细研究了几种基于离散流的微分分析系统的原理及结构。     

Ca0.9Sr0.1S:Bi3+,Tm3+荧光材料的光学性质

Ｃａ０．９Ｓｒ０．１Ｓ：Ｂｉ＾３＋,Ｔｍ＾３＋是一种复合掺杂复合基质荧光材料。在此给出了４４０ｎｍ和５２０ｎｍ发射的激发谱,２５０ｎｍ到３５０ｎｍ的激发的发射谱,以及４００ｎｍ到５２０ｎｍ的荧光衰减谱。紫外光区域的激发谱表明,Ｃａ０．９Ｓｒ０．１Ｓ：Ｂｉ＾３＋,Ｔｍ＾３＋有两个主要的能量传递体系,３２５ｎｍ的复合掺杂中心Ｔｍ＾３＋的ＣＴ跃迁激发体系,和Ｂｉ＾３＋的自身激发体系。紫外激发的荧光发射谱     

几种非光学显微镜介绍

电子显微镜（ｅｌｅｃｔｒｏｎ ｍｉｃｒｏｓｃｏｐｅ） 电子显微镜是一种利用电子束照射物体并形成像的非光学显微镜．电子束通过作为电子折射媒质的静电透镜或磁透镜进行聚焦,通过加速电压,能够产生波长比普通光要短若干倍的电子波．根据显微镜原理,波长愈短,其分辨本领愈大．所以电子显微镜的放大倍数是普通光学显微镜的放大倍数的几千至数十万倍．电子显微镜一般有：透射电子显微镜、扫描电子显微镜和发射式电子显微镜等多种．透射电子显微镜的原理如图１所示． 它由以下几部分构成：产生等速电子束的电子源,把电子集中在样品上的…