用αβ谱仪测量人工αβ放射性气溶胶体积活度的试验研究

本文介绍了用αβ谱仪系统同时测量αβ谱、实现Ｒｎ／Ｔｈ子体补偿、确定超铀α核素气溶胶体积活度及人工放射性气溶胶总β体积活度的技术途径。利用ＲａＡ、ＲａＣ′ａ峰的二段时间计数可确定空气中ＲａＡ、ＲａＢ、ＲａＣ的气溶胶体积活度，相应的，也能给出ＲａＢ、ＲａＣ对总β计数的贡献。根据一般环境条件下的平衡比，用ＴｈＣ′的。计数修正Ｔｈ子体对αβ测量的影响。￣［２３９］ｐｕ或／和￣［２４１］Ａｍ人工核素的α计数，可通过两段时间分别扣除ＲａＡ、ＲａＣ′拖尾的方法确定；β计数分别扣除Ｒｎ／Ｔｈ子体β贡献即可确定。在本文规定的测量条件下，对室内天然Ｒｎ子体水平在１５Ｂｑ／ｍ￣３以下，超铀α核素气溶胶体积活度的测量下限可达到０．１Ｂｑ／ｍ￣３；即使在７５Ｂｑ／ｍ￣３环境下，人工核素总β的测量下限也可达ｌＢｑ／ｍ￣３以下。     

Oxidation behavior and mechanism of aluminum oxynitride (AlON) at elevated temperatures

The oxidation behavior and mechanism of aluminum oxynitride (AlON) powder exposed to air at elevated temperatures between 800°C and 1300°C was investigated by X-ray diffractometry (XRD), scanning electron microscope (SEM), electron spin resonance (ESR), nuclear magnetic resonance (NMR), and simultaneous thermogravimetry, differential thermal analysis, and mass spectrometry techniques (TG-DTA-MS). The weight of AlON gradually increases to a maximum value at 1150°C and then decreases with further heating. Meanwhile, AlON powder undergoes chemical changes, as evidenced by lattice expansion, and turns eventually into alumina. ESR spectra reveal the occurrence of lone pair electrons in the oxidized products and the intensity of corresponding resonance signal increases before disappearing with the increase in temperature. Combined with the results of NMR and TG-DTA-MS, the measured data suggest that Al-N in [AlO₃N] tetrahedron and [AlO₅N] octahedron are gradually oxidized into Al-O-N group with lone pair electrons, which causes continuous weight gain and lattice expansion. Further oxidation at higher temperatures results in alumina and N₂.     

学生如何正确掌握OFFICE软件

Microsoft Office是一套由微软开发的办公软件。电脑普及之后,已成为人们生活中的“常用软件”。数字化办公,小到会议记录,大到社会统计离不开它的帮助。当今社会,办公自动化成为大趋势,对于学生而言,现在能够扎实的掌握Office软件的使用方法,对于今后的就业与工作都有着深远的意义。     

XML发布/订阅数据流系统基于共享的多查询连接算法

XML的发布/订阅系统中的XML多查询连接,涉及到多个XML文件之间关系的订阅的处理,包括了对XPath路径模式的评测,对XML文档之间的比较计算以及对系统时间进行管理等方面。基于共享的连接算法,通过适当的组织,使得多个订阅之间相同的变量连接计算结果得以被重复利用,较大程度地减少了开销很大的连接计算,从而较大地提高系统效率。实验结果表明,基于共享的算法取得了良好的实际效果,能适合于百万以上订阅的场合。     

An SPH-based mass transfer model for simulating hydraulic characteristics and mass transfer process of dammed rivers

Engineering with Computers - Aerated flow characterized by complex mass transfer processes with multiple hydraulic properties is a common enviro-hydraulics phenomenon, which have a variety of...     

动态公路自动衡器动态示值误差测量的不确定度评定

结合工作实际,阐述了在长期检测工作中发现一些影响其计量准确性的因素,它对动态公路车辆自动衡器单轴称量示值误差不确定度的影响。     

医院网络安全的技术实现与改进

随着信息科技的高速发展,网络在越来越多地为人们生活提供便利的同时,也为医院节省了大量的人力和物力,如何在现有的条件下,搞好局域网络的安全,是医院内网络管理人员的一个重要课题.本文从系统安全、网络运行安全和内部网络安全分析,并应用到实践中,以保证网络安全.