Emissivity Measurements on Metallic Surfaces with Various Degrees of Roughness: A Comparison of Laser Polarimetry and Integrating Sphere Reflectometry

Both integrating sphere reflectometry (ISR) as well as laser polarimetry have their advantages and limitations in their ability to determine the normal spectral emissivity of metallic samples. Laser polarimetry has been used for years to obtain normal spectral emissivity measurements on pulse-heated materials. The method is based on the Fresnel equations, which describe reflection and refraction at an ideally smooth interface between two isotropic media. However, polarimetry is frequently used with surfaces that clearly deviate from this ideal condition. Questions arise with respect to the applicability of the simple Fresnel equations to non-specular surfaces. On the other hand, reflectometry utilizing integrating spheres provides a measurement of the hemispherical spectral reflectance, from which the normal spectral emissivity can be derived. ISR provides data on spectral-normal-hemispherical reflectance and, hence, normal spectral emissivity for a variety of surfaces. However, the resulting errors are minimal when both the sample and the reference have a similar bidirectional reflectance distribution function (BRDF). In an effort to explore the limits of polarimetry in terms of surface roughness, room temperature measurements on the same samples with various degrees of roughness were performed using both ISR and a laser polarimeter. In this paper the two methods are briefly described and the results of the comparison are discussed.     

A correlation for predicting diffusion coefficients in alkanes

A correlation was developed for predicting limiting mutual diffusion coefficients of gaseous and liquid solutes in normal alkane solvents with carbon numbers ranging from 7 to 28 at temperatures to 570 K. The functional form of the correlation is based on the rough hard sphere theory. The parameters needed in the correlation are the molecular weights and hard sphere diameters of the solute and solvent molecules and molar volume of the solvent. The data used in the development of the correlation included 143 measurements with solute/solvent molecular mass ratios ranging from 0.005 to 2.26 and size ratios ranging from 0.3 to 1.3. The average absolute error in predictions was only 6.3%. When the correlation was used to predict literature values for binary n-alkane systems, the average absolute error was 16.7%.     

塑料颜料的性能及在涂布纸中的应用

主要对塑料颜料的生产方法、运输和存储、输送、化学物理性质、作用机理等方面进行了阐述，并对今后塑料颜料的运用进行了展望。     

蜂窝状蓄热体与蓄热小球混装结构在蓄热式加热炉上的应用

通过工程改造项目介绍了蜂窝状蓄热体和蓄热小球混装的新型蓄热体结构,分析得出新型结构成本低,蓄热能力可提高20％以上,对于全新蓄热式加热炉蓄热室的设计具有指导和借鉴意义.实践表明,采用此种结构具有高效、优质、节能和低污染等诸多优点,具有广阔的开发应用前景.     

单分散SiO_2胶体光子晶体的自组装制备与表征(英文)

使用Stber法化学合成了粒径在200-350nm之间的单分散SiO2,采用垂直沉积技术自组装制备了胶体晶体薄膜。通过扫描电镜与分光光度计对样品的微观结构与透过光谱进行了表征,结果表明,组成胶体晶体的SiO2微球呈面心立方结构,膜层的厚度可以通过胶体溶液的浓度加以控制,胶体膜层透射光谱中出现的峰值位置取决于SiO2微球的大小,并且与布拉格定律理论计算的结果相一致,透射光谱中光学阻带的深度可以通过改变胶体悬浮液中SiO2颗粒的体积分数来调控。     

一种改进的球形解码算法

提出了算法根据累积分布函数得到一个阈值,在搜索到叶子节点后,将累积度量值和阈值进行比较来判断是否找到最大似然解,从而降低了球形解码算法在高信噪比范围内的复杂度.阈值的选取对球形解码算法的性能有一定的影响,在取值时,可以根据不同的信噪比范围对性能和复杂度做一个权衡.仿真结果表明,所提出算法的展开节点数在高信噪比范围内收敛于m.     

锂离子电池球形正极材料的研究进展

球形化可以提高锂离子正极材料的压实密度、体积比容量并改善其加工性能和极片的质量。简要介绍了球形材料的特点,综述了球形LiCoO2、LiNixM1-xO2、LiMn2O4、LiFePO4等的制备及其性能,展望了球形正极材料的应用前景。     

Effects of the precursor size on the morphologies and properties of γ-Ce_2S_3 as a pigment

Ceria spheres with different sizes and sulfurized products with corresponding morphology were prepared by hydrothermal and gas-solid reaction method at 600–800 °C under CS2 atmosphere for a short time, respectively. Dimensional effect in preparation of γ-Ce2S3 was firstly investigated by means of techniques such as scanning electron microscopy(SEM), X-ray diffraction(XRD), thermal gravimetric analysis(TGA) and spectrophotometer. The results showed that when ceria nanoparticles with small size were used as precursors, the γ-Ce2S3 could be prepared at the lower temperature and the badly sintered products were obtained; when ceria nanoparticles with large size were employed as precursors, pure γ-Ce2S3 was difficultly obtained even if the temperature was up to 800 °C and the products tended to keep their original size. The heat-resistance property of the γ-Ce2S3 with large size was better than the smaller one, and the pure γ-Ce2S3 prepared from precursor with small size had a good pigmentary performance.