Operating systems

The objectives and stages of operating systems introduced in Part 1 are continued here. Four major components —process management, input-output (I/O) device management, memory management, file management and protection are discussed.     

Should Science be Taught in Early Childhood?

This essay considers the question of why we should teach science to K-2. After initial consideration of two traditional reasons for studying science, six assertions supporting the idea that even small children should be exposed to science are given. These are, in order: (1) Children naturally enjoy observing and thinking about nature. (2) Exposing students to science develops positive attitudes towards science. (3) Early exposure to scientific phenomena leads to better understanding of the scientific concepts studied later in a formal way. (4) The use of scientifically informed language at an early age influences the eventual development of scientific concepts. (5) Children can understand scientific concepts and reason scientifically. (6) Science is an efficient means for developing scientific thinking. Concrete illustrations of some of the ideas discussed in this essay, particularly, how language and prior knowledge may influence the development of scientific concepts, are then provided. The essay concludes by emphasizing that there is a window of opportunity that educators should exploit by presenting science as part of the curriculum in both kindergarten and the first years of primary school.     

虫媒登革病毒的研究——Ⅱ.登革病毒非结构蛋白NS1的纯化、鉴定及其在临床检测应用

本文从纯化Den2 NS1,Mab入手,自制了Mab亲和层析系统,从感染Den2的细胞膜中,分离提取了天然的Den 2 NS1双体,比较其NGC株与我国地方株(H-87)NS1的理化性质及组成,并对某些重要的生物学性质进行了综合性研究。同时,利用上述研究结果建立了检测DF病人血清特异NS1抗体的新方法,探索其协助临床诊断及研究的可能性。     

J2EE平台在行政审批服务系统中的应用

本文分析了电子政务对国民经济所起的重大作用,简要介绍了当前流行的J2EE架构的分布式对象结构特点。设计了一个J2EE架构下的行政审批服务系统,它由客户层、中间层和企业信息系统层等三个层次组成。同时,对系统的设计方法、软件结构及实现技术进行了探讨。     

基于Unity3D反恐排爆机器人虚拟仿真设计

基于虚拟现实技术开发软件对反恐排爆机器人虚拟实验系统进行功能开发,该系统应用于反恐排爆机器人教学,建立D-H机械臂坐标系,实现反恐排爆机器人结构认知、装配操作、工作空间、关节运动控制,实现人机交互,利用D-H参数法建立反恐排爆机器人运动学模型,进行了正、逆运动学求解及轨迹规划。系统有着较好的沉浸性与交互性,能够完成反恐排爆机器人的虚拟实践教学。     

Thermodynamic Analysis and Comparison on Low Temperature CO_2-NH_3 Cascade Refrigeration Cycle

Intheapplicationsofindustrialandcommercialrefrig erationsystem ,iftherequiredrefrigerationtemperatureisverylow ,theconventionalvaporcompressionsystemisdiffi culttomeettherequirementbecausewhenthedifferencebe tweentheevaporatingtemperatureandthecondensingtemper atureissohighthatitishardtofindarefrigeranttomeettheneedsasthecondensingpressureisnottoohighandtheevap oratingpressureisnottoolow .Whentherefrigeratingtemper atureisverylow ,thecascaderefrigerationcycleissuitabletobeused .Itcannotonlysat…     

武清地热热储数值模拟

采用 AU TOU GH2热储计算软件对天津市武清县地热热储进行数值模拟计算 ,分析热储在不同开发利用条件下的特征 .主要针对无回灌和有回灌两种生产情况 ,分析地热热储的温度、压力随时间和距离的变化 ,还分析随地热水的生产 ,地热热储的生产能力、水位和压力的变化以及回灌对生产井的冷却效应     

有奖储蓄中奖号码的计算机分析

本文根据K.Pearson X~2的检验法,对中国工商银行浙江省分行1981年1月～1987年12月所有的由摇奖机摇出的有奖储蓄的中奖号码,利用电子计算机进行了统计分析.运算结果肯定了中国工商银行浙江省分行目前的摇奖方法是可靠的.也就是说,每个月在全省的某一地、市、县轮流用不同的摇奖机、不同的号珠,由不同的操作人员摇出中奖号码的方法,是行得通的.同时也指出,广大储户完全没有必要去择号购奖券,甚至买好以后再去调换所谓“中意的奖券,因为相对于信度10%而言,我们肯定了假设H:0～9这十个号珠中的每一个被摇奖机摇出的概率是相等的.”     

Cu-ZnO/Al2O3催化仲丁醇制备甲乙酮

用Cu-ZnO/Al2O3催化仲丁醇制备甲乙酮。研究了催化剂的焙烧温度和焙烧时间、仲丁醇脱氢反应的温度和压力以及仲丁醇的流量对仲丁醇转化率和甲乙酮选择性的影响。结果表明,催化剂的焙烧温度为300-400℃,焙烧时间为6h,脱氢反应的温度为300℃,压力为0.2Mpa,仲丁醇的流量为140mL/h时,仲丁醇的转化率和甲乙酮的选择性较好。     

Hydrogenation properties of mechanically milled Mg2Nio.8Cr0.2-CoO/Al2O3 composites

Mg2Ni0.8Cr0.2-x wt.% CoO/Al2O3 (x=0.5, 1, 2 and 3) composites were prepared by mechanically milling sintered Mg2Ni0.8Cr0.2 alloy and CoO/Al2O3 compound for 45 h. The addition of CoO/Al2O3 compound resulted in the good kinetics properties of hydriding/dehydriding reaction of the composites. The composite with 1.0 wt.% CoO/Al2O3 catalyst could reach the maximum hydrogen absorption capacity (2.9 wt.%) within 5 min at 393 K under H2 pressure of 4 MPa, and can desorb rapidly at 493 K. The decomposition and synthesis of hydrogen molecule on Mg2Ni0.8Cr0.2 alloy surface was promoted by addition of CoO/Al2O3 catalyst. In addition, the formation of metallic Ni particles, strain and defects during the ball milling process also resulted in the improved hydrogenation performance of Mg2Ni-based alloys.