Optical measurements of thermal diffusivity of a material

The measurement of thermal diffusivity of a material (in particular, a thin film) is important for various reasons, e.g., to predict the heat transfer in the solid subjected to a thermal process, to monitor surface composition or morphology, or to detect invisible subsurface defects like delaminations. This measurement can be done in a noncontact manner using various photothermal methods. Such methods typically involve pulsed heating of the surface by small amounts using a laser source; the decay of the surface temperature after this pulsed photothermal heating is then probed to provide the thermal diffusivity. Various probing methods have been developed in the literature, including the probing of reflection, refraction, and diffraction from the pulsed heated area, infrared thermal radiometry, and surface deformation. This paper provides an overview of such techniques and some examples of their applications.     

Contemporary approaches to certification of measurement provision software

Contemporary approaches to the certification of measurement provision software are considered in domestic and overseas publications. Normative documentation is analyzed and a scheme is proposed for certification that takes account of the features of programs used for metrological purposes. __________ Translated from Izmeritel’naya Tekhnika, No. 5, pp. 65–68, May, 2007.     

Teaching-Material Design Center: An ontology-based system for customizing reusable e-materials

Use of electronic teaching materials (e-material) to support teaching is a trend. e-Material design is therefore an important issue. Currently, most e-material providers offer a package of solutions for different purposes. However, not all teachers and learners need everything from a single package. A preferable alternative is to find useful material from different packages and combine them for a particular course. Currently, most educators collect the material manually, which is time-consuming and may result in missed material. In this paper, we describe a system – the Teaching-Material Design Center, which follows the standard of Sharable Content Object Reference Model – to separate e-material for use as teaching templates and learning objects and to label the material with use of semantic metadata for searching. This system can find existing teaching templates and learning objects for e-material designers and provide a convenient environment for constructing customized e-material for different requirements. We describe the implementation and evaluation of the proposed system for a course. Our system is efficient in finding teaching templates and learning objects and shortening the e-material development process.     

Lateral space-charge effects on ballistic electron transport across graded heterojunctions

Hot electron transport across graded compound semiconductor heterojunctions has been explored using a two-dimensional formulation of the self-consistent ensemble Monte Carlo method. The Al_xGa_1-xAs/GaAs heterojunction imbedded into a vertical field effect transistor with two ohmic contacts (source, drain) and two lateral Schottky gates has been used as an example. Lateral space charges modulated by the gates are shown to control ballistic injection of electrons over the heterojunction under steady state conditions. The transient response to a gate pulse is found to be determined by carrier transit from the heavily doped source contact region into the channel. A conceptual one-dimensional section model is used to explain the Monte Carlo results.     

凸非球面补偿检验的工艺球面分析解

本文从三级像差理论出发,推导了几种工艺球面检验凸二次曲面的计算公式。根据这些公式计算结果,进行了光路追迹,给出了这些公式对凸二次曲面的补偿范围;并讨论了几种特殊情况下的平面解。     

蒙特卡洛法速度谱的自动拾取

蒙特卡洛速度谱的自动拾取采用一种非线性优化的快速方法，所得叠加速度的精度可以满足常规地震资料处理中叠加的要求，转换为层速度后可用于叠前深度偏移成象，在给定初始速度模型前提下建立优化目标函数。采用蒙特卡洛非线性优化算法，以最大相似度量准则在考虑实际地质条件前提下给出速度约束条件，对初始速度模型加以扰动，自动寻找速度谱中叠加能量的全局最优解，从而获得合理的速度模型。实际地震资料处理的应用结果表明，自动拾取速度谱比常规的人工速度谱解释工作的效率大幅度提高。在SUN Ultra60机上,仅需1h即可完成2000km的地震资料的速度谱拾取任务，而且所获得的速度模型不受人为因素影响，转换所得的层速度模型用于叠前深度偏移后，获得了满意的成象效果。     

发泡金属的开发、性质及应用(Ⅰ)──发泡金属的制备方法

系统地综述了发泡金属的生产方法，包括铸造法、粉末冶金法、烧结法、沉积法和高压浸透法等。介绍了各种方法的特点及适用范围，指出了它们的优缺点及相应的改进措施，并对今后的发展方向提出了建议。     

地理环境与先秦南北饮食文化

先秦时期是我国饮食文化的形成时期，受地理环境的强烈影响，逐渐形成了以秦岭-淮河一线为界的南北两个主要的饮食文化区域：黄河中下游地区为中心的北方饮食文化区，是以旱地粮食作物黍、稷、粟等为主食，陆地动物为辅食，烧、烤、炸为主要烹饪方法的北方饮食风味；长江中下游地区为中心的南方饮食文化区，是以水田粮食作物稻米为主食，陆地动物和水产动植物为辅食，蒸、炖、煎为主要烹饪方法的南方饮食风味。