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。     

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。     

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...     

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.     

Optimal Control of Two-Stage Discrete Event Systems with Real-Time Constraints

We consider discrete event systems (DES) involving tasks with real-time constraints and seek to control processing times so as to minimize a cost function subject to each task meeting its own constraint. When tasks are processed over a single stage, it has been shown that there are structural properties of the optimal sample path that lead to very efficient solutions of such problems. When tasks are processed over multiple stages and are subject to end-to-end real-time constraints, these properties no longer hold and no obvious extensions are known. We consider a two-stage problem with homogeneous cost functions over all tasks at each stage and derive several new optimality properties. These properties lead to the idea of introducing “virtual” deadlines at the first stage, thus partially decoupling the stages so that the known efficient solutions for single-stage problems can be used. We prove that the solution obtained by an iterative virtual deadline algorithm (VDA) converges to the global optimal solution of the two-stage problem and illustrate the efficiency of the VDA through numerical examples.

青龙瀑布景区游客满意度实证研究

随着旅游业竞争的日趋激烈,旅游景点如何在竞争中脱颖而出,对顾客满意度影响因素分析和研究至关重要。文章以万州青龙大瀑布为例,通过对影响万州青龙大瀑布顾客满意度因素的问卷调查,将影响满意度的19个变量因素运用SPSS软件进行整理分析,运用因子分析法将19个变量归为四大公共因子,分别是旅游服务、旅游保障、景区宣传、景区管理四大类,并对其进行信度检测,随后构建了顾客满意度综合评价模型,最后对如何提高顾客满意度提出对策建议,以促进旅游景点服务质量的有效提高。     

PC/104总线工控机及其在饲料配料控制中的应用

通过一个应用实例来说明ＰＣ／１０４总线工控机不仅在结构、硬件、软件上与标准ＰＣ总线工控机完全兼容，而且由于采用模块化设计方法使之体积更紧凑、可靠性更高、功耗更低。