环境中氚和碳-14

本文介绍了加拿大恰克河实验室有关氚和碳－14在环境中行为和评价的研究。     

由光率体求导折射率及振动方向的新方法

从光率体出发，利用坐标轴旋转，导出了光在晶体中传播时折射率及振动方向的公式。     

分布式光纤喇曼放大技术及其在WDM系统中的应用

介绍了分布式光纤喇曼放大技术的原理、特点和应用 ,并从受此影响的 WDM传输系统的信噪比、噪声指数和品质因数三个方面讨论了光纤喇曼放大技术在提升光纤通信系统性能方面的重要作用。     

中国石油未来油气勘探重点领域分析

根据近几年来的研究认识与勘探成果分析,未来几年中国石油油气勘探主要集中于如下五大重点领域:大面积低渗透岩性油气藏、成熟区复杂隐蔽油气藏、前陆盆地复杂构造油气藏、海相碳酸盐岩油气藏和渤海湾滩海第三系油气藏。     

Nondestructive evaluation of the characteristics of degraded materials using backward radiated ultrasound

The frequency dependency of Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in two kinds of degraded specimens by scuffing or corrosion. Then, the frequency dependency is compared with the residual stress distribution or the corrosion-fatigue characteristics for the scuffed or corroded specimens, respectively. The width of the backward radiation profile increases with the increase of the variation in residual stress distribution for the scuffed specimens. In the corroded specimens, the profile width decreases with the increase of the effective aging layer thickness and is inversely proportional to the exponent, m, in the Paris’ law that can predict the crack size increase due to fatigue. The result observed in this study demonstrates high potential of backward radiated ultrasound as a tool for nondestructive evaluation of subsurface gradient of material degradation generated by scuffing or corrosion.     

长距离油、气、水混输管道内壁流动腐蚀的研究进展

就近几十年来，多相流管线的流动腐蚀（CO2腐蚀，H2S腐蚀，腐蚀/冲蚀协同作用），腐蚀/冲蚀数学模型和设计准则，腐蚀检测，腐蚀防护与控制技术等方面的研究进展进行了综述。指出了当前研究中所存在的一些问题，就多相流的研究方向提出了相应的建议。     

啤酒酵母菌种的石蜡保藏技术

啤酒酵母菌种用液体石蜡技术保藏具有设备简单、操作方便,成活率高,变异少,优良种性能保持较长时间的优点,实用价值高。本文从液体石蜡保藏菌种的机理、保藏效果、保藏等具体技术操作及其使用方法都作了较为详细的介绍,相信能为啤酒菌种的保藏带来较大的好处。     

Onset of buoyancy-driven convection in melting from below

When a horizontal homogeneous solid is melted from below, convection can be induced in a thermally unstable melt layer. In this study the onset of buoyancy-driven convection during time-dependent melting is investigated by using similarly transformed disturbance equations. The critical Rayleigh numbers based on the melt-layer thickness are found numerically for various conditions. For small superheats, the present predictions approach the well known results of classical Rayleigh-Bénard problems, that is, critical Rayleigh numbers are located between 1,296 and 1,708, regardless of the Prandtl number. However, for high superheats the critical Rayleigh number increases with an increase in phase change rate but with decrease in Prandtl number.     

Characteristics of Milk Powders Produced by Spray Freeze Drying

Skim and whole milk powders were manufactured at lab scale by spray freeze drying (SFD), using liquid nitrogen as the cryogen. The polydispersity of droplet/particle sizes was limited using an encapsulator nozzle to atomize the feed. Particle morphology was examined using a scanning electron microscope. Samples were compared with equivalent spray-dried powders in tests of wettability and dissolution in water. The spray freeze-dried powders were found to be highly porous, with a uniform structure of pores throughout the entire particles. When tested in water, SFD skim milk powders wetted roughly three times as fast as industrially spray-dried agglomerated skim milk powders and were observed to dissolve rapidly by breaking down into smaller particles.