非等温空腔法确定固体材料的比辐射率

本文讨论一种确定固体材料比辐射率的方法。在被测材料的表面开一个圆柱形空腔,并在其背面均匀加热。联立求解腔壁的辐射换热和体内的热传导方程,求得温度场分布和腔底的有效辐射。结果表明,腔底的有效辐射是比辐射率、腔深和半径之比以及一个表示温度梯度的参数的函数。文中讨论了能量辐射和光子辐射两种情况。在实验中,用热象仪测量材料表面和腔底的有效辐射。由理论分析结果和实验测定的有效辐射,求得材料的比辐射率。     

Optimal Taxation in an Endogenous Growth Model with Multiple Levels of Governments

This paper presents a framework with federal income tax, federal transfer, and local taxes in an dynamic growth model with multiple levels of governments and public capital formation. It derives the rate of endogenous growth and, with both simulations and special examples, examines how the rate of endogenous growth changes with respect to federal income tax, local taxes, and federal transfers.     

Formation of highly crystalline maghemite nanoparticles from ferrihydrite in the liquid phase

Fe₅O₇(OH)·4H₂O ferrihydrite is a low-crystallinity antiferromagnetic material. γ-Fe₂O₃ (maghemite) magnetic nanoparticles were prepared from a ferrihydrite precursor, by chemically induced transformation in FeCl₂/NaOH solution. The magnetization, morphology, crystal structure and chemical composition of the products were determined by vibrating sample magnetometry, transmission electron microscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy (XPS). Ferrihydrite underwent aggregation growth and transformed into α-FeO(OH) (goethite) particles, which subsequently transformed into γ-Fe₂O₃ nanoparticles, that became coated with NaCl. The γ-Fe₂O₃ particles had a flake-like morphology, when prepared from 0.01 mol/L FeCl₂ and a FeCl₂:NaOH molar ratio of 0.4. The γ-Fe₂O₃ particles were more spherical, when prepared from a FeCl₂:NaOH molar ratio of 0.6. The Fe content of the flake-like particles was lower than that of the spherical particles. Their magnetizations were similar, and the coercivity of the flake-like particles was larger. The differences in morphology and magnetization were attributed to the surface effect, and the difference in coercivity to the shape effect.     

The influence of molar ratios of Ce/Zr on the selective catalytic reduction of NOx with NH3 over Fe2O3-WO3/CexZrl-xO2 （0 〈 x 〈 1） monolith catalyst

A series of CexZrl_xO2 （0 ≤ x ≤ 1） with dif- ferent molar ratios of Ce/Zr were syhthesized via coprecip- itation method, and Fe2O3-WO3/CexZrl-xO2 monolithic catalysts were prepared, for selective catalytic reduction of nitrogen oxides by ammonia （NH3-SCR）. The structural properties and redox behavior of the catalysts were com- prehensively characterized by N2 physisorption, X-ray diffraction （XRD）, X-ray photoelectron spectra （XPS）, H2-temperature programmed reduction （H2-TPR） and activity measurement for NH3-SCR. The results showed that the NH3-SCR activities of the catalysts were gradually enhanced by increasing the molar ratios of Ce/Zr, especially the low- temperature catalytic activity and the reaction temperature window. Fe2O3-WO3/Ceo.68Zro.3202 monolithic catalyst presented the best NH3-SCR activity among the investigated catalysts, more than 90 % NOx could be removed in the temperature range of 247-454 ℃ on the catalyst under the gas hourly space velocities of 30,000 h- 1. And it always held more than 99 % N2 selectivity and less than 20 ppm （1 ppm =10-6 L/L ） N20 generation concentration between 200 and 500 ℃, the catalyst also displayed its strong resistance of H20 and SO2. Good textural and structural properties, more surface Fe, Ce and active oxygen were together contributed to the excellent NH3-SCR performance of Fe2O3-WO3/ Ce0.68Zr0.32O2 catalyst.     

平底结构砰击作用下具有自由表面限制水域的流体动力特性

本文采用VOF方法、考虑限制水域边界条件的约束因素,利用CFD商业软件FLUENT通过求解脉冲砰击压力作用下具有自由表面限制水域上的Navier-Stokes方程来分析与观察大型平底结构从一定的高度自由落下砰击限制水域的水面所引起的三维流体动力现象。数值模拟结果表明采用本文所提出的数值方法可以对脉冲砰击压力作用于考虑自由表面效应的封闭或开放水域的水面所激发起的水面波动和水下压力场变化进行有效的数值模拟。这一数值方法为工程上分析大型平底结构砰击限制水域水面所产生的水动力现象提供了一种实用的手段。     

平底结构砰击作用下限制水域的流体动力特性

采用流体体积函数法VOF方法,考虑限制水域边界条件的约束因素,利用计算流体力学(CFD)商业软件Fluent求解脉冲砰击压力作用下具有自由表面限制水域的Navier-Stokes方程,以分析与观察大型平底结构从一定的高度自由落下砰击限制水域的水面所引起的三维流体动力现象.结果表明,采用文中所提出的数值方法可以对脉冲砰击压力作用于封闭或开放水域的水面所激发的水面波动和水下压力场变化进行有效的数值模拟.这一数值方法为工程上分析大型平底结构砰击限制水域水面所产生的水动力现象提供了一种实用的手段.     

掺铕(铽)多孔硅的制备及其光致发光

采用了一种新的掺杂方法——溶胶-凝胶法将稀土配合物掺入多孔硅中．研究结果表明：“溶胶-凝胶法”可有效地把稀土掺入多孔硅中,所制得的杂化材料中,观察到Eu^3＋、Tb^3＋特征的橙红色、绿色室温光致发光．而且,通过SiO2对掺入稀土的包裹作用和对多孔硅层的覆盖,提高了多孔硅的稳定性,部分减少了多孔硅的发光猝灭．     

面阵CCD对汞灯衍射光谱的采集与实时测量

设计了一个面阵CCD光谱采集测量系统,提出了一种波长和频率测量的新方法.运用衍射光栅得到汞灯的衍射光谱线,利用面阵CCD采集光谱图像,编写程序对采集图像进行处理,得出各谱线的波长和频率.该方法可实现实时测量且具有较高的测量精度.     

（Ca1-xNdx）[（Li1／3Nb2／3）0．95Zr0．15]O3＋δ微波介电特性陶瓷

研究了A位Nd3 取代对(Ca1-xNdx)[(Li1/3Nb2/3)0.95Zr0.15]3 δ(0.0≤x≤0.2,CNLNZ)陶瓷的微观结构及微波介电特性的影响.当0.00≤x≤0.03时,体系为单一钙钛矿相,随Nd3 摩尔分数的增加,品质因素的值先增大,然后因B位l∶2有序度在x=0.02处下降而开始减小.分析了谐振频率温度系数随容忍因子的变化关系.当x=0.03时,陶瓷微波介电性能最佳:相对介电常数为32.7,品质因素为15 880 GHz,谐振频率温度系数为-6.4×10-6/℃.     

对高校和谐图书馆建设的几点思考

建设和谐图书馆是构建和谐校园的一项重要内容.高校建设和谐图书馆要树立正确的和谐发展观、以人为本的管理理念和服务理念,培育良好机制,处理好馆内外人际关系,增强图书馆的凝聚力,营造图书馆良好的文化环境,从而使图书馆事业健康和谐地发展.