虚拟机软件在中职网络教学和实训中的应用

随着全国中等职业学校计算机技能大赛的举办,中职学校网络实训环境发生了改变,虚拟机软件在网络教学中得到了广泛的应用.通过虚拟机软件可以建立虚拟化的实训环境,模拟真实的计算机系统.使用虚拟机软件既可以克服教学资源和设备不足的困难,又可以解决实训时长不足,完成真实环境难以实现的实训任务,保证网络教学和实训的顺利进行.     

Water Adherence Factors for Human Skin

On incidental dermal exposure to chemicals in water, a key exposure factor is the amount of water adhering to skin. Although soil adherence factors have been developed for risk assessment, measurements of water adherence on human skin have not been described. In the Environmental Protection Agency's (EPA's) dermal risk assessment guidance, dermal dose from environmental exposures is based upon the flux rate across the skin, which assumes that an unlimited amount of chemical is available for absorption. This assumption is applicable to certain exposure scenarios such as swimming and bathing. However, exposures to contaminated water frequently involve scenarios where the available chemical is limited by the amount of water adhering to the skin, for example, during accidental splashes. We conducted studies in human volunteers to investigate water adherence per unit area of skin after brief contact with water. In two sets of experiments, either water was applied with a micropipette to 10‐cm² areas of the lower leg, foot, and hand, or the foot and hand were briefly immersed in water. In males, using a micropipette, water adherence ranged from 1.93 (foot) to 7.13 μL/cm² (lower leg). In females, it ranged from 1.10 (lower leg) to 4.83 μL/cm² (hand). Hand and foot immersion resulted in relatively higher values of 6.89 and 5.17 μL/cm², respectively, in males, and 5.40 and 6.39 μL/cm² in females. Water adherence was affected by amount of body hair and type of exposure. Water adherence factors can be used to calculate the applied dose per unit area for exposures involving intermittent water contact.     

基于单片机AT89C51的全自动变频恒压供水系统

介绍了一种新型的变频恒压供水系统.该系统根据供水管网的用水情况,调整水泵投入台数及转速,实行全自动恒压供水,达到高效节能的目的;其水泵用变频器软启动,对电网无冲击,能延长水泵的使用寿命.     

“水资源利用与保护”课程新型案例教学模式探讨

社会对环境类人才的能力要求越来越高，教师需要着力培养学生的创新能力，强化训练学生的实践能力。在深入研究案例教学的理论基础上，根据“水资源利用与保护”课程的知识结构、课程特点及教学目标，结合教学对象的学习需求，紧扣世界水环境急剧变化给水资源利用与保护提出的新挑战，面向西部的水资源特性及城市水环境现状，设计教学案例，制定实施案例教学流程，对“水资源利用与保护”课程的新型案例教学模式进行了探讨。     

晚唐五代时期金河黑河水系变迁与环境演变

汉代黑河(删丹河,或名张掖河,又名弱水)与北大河(金河,又名呼蚕水)交汇入注居延海,汉代以后直到唐代之前都没有记载.<元和郡县图志>记载两水分流,金河流注白亭海,张掖河流注居延海.敦煌文献记载晚唐时金河与张掖河交汇流注居延海,使居延海湖面出现一个恢复期.此外,金河和黑河流域地区居民结构变化、农业人口和用水量减少、黑河径流量增加也是居延海湖面增加的原因.     

采用汇文系统实现统编工作的探索

统一编目工作是促进图书馆业务工作自动化与标准化的重要技术,笔者从采用汇文系统进行统编工作的实践尝试中,探讨了统编工作中存在的一些实际问题,并提出了解决方案.     

致用与会通——薛凤祚水利思想蠡测

薛凤祚治学方法的特点,即＂致用＂与＂会通＂。其中,会通包含古今的会通与中西的会通。由《两河清汇》解读薛凤祚的水利思想,比较突出的是其治河和海运的思想。《两河清汇》从体例上言,可谓＂编述之体＂,薛凤祚不仅继承发扬了儒家圣贤的一些学说,也吸收了其前代潘季驯、邱濬等人的观点。观其采择去取,无不以＂致用＂为宗。而其热心译介当时西方的水利器械,可以看作他在中西会通中所作的努力。虽然如此,对于薛凤祚《两河清汇》及其水利思想不可刻意拔高。     

聚酯聚合反应分层温度控制系统

介绍了聚合釜聚酯聚合反应温度过程控制系统及其设计方法。控制系统以高性能单片机系统为直控机（DDC）,PC机为上位机（MIS）,直控机负责聚合釜釜温及夹套温度采集、分析、控制,并将参数送上位机。上位机负责控制过程的时间及温度值设定、温度监测、工作过程监控。     

纸机传动控制系统的配置与控制原理

针对纸机日益高速化、大型化的发展趋势，设计了国内先进的全数字化通信网络传动控制系统。系统采用西门子全集成自动化解决方案，实现造纸生产过程的全线集成控制。高可靠的工业现场总线PROFIBUS—DP和工业以太网相结合的网络结构，有效地实现了数据共享，全面解决了整个工艺过程的控制。文章详细介绍了控制系统的配置和功能，重点阐述了速度链、负荷分配控制、张力控制等主要控制原理。     

Agent‐Based Modeling to Simulate Contamination Events and Evaluate Threat Management Strategies in Water Distribution Systems

In the event of contamination of a water distribution system, decisions must be made to mitigate the impact of the contamination and to protect public health. Making threat management decisions while a contaminant spreads through the network is a dynamic and interactive process. Response actions taken by the utility managers and water consumption choices made by the consumers will affect the hydraulics, and thus the spread of the contaminant plume, in the network. A modeling framework that allows the simulation of a contamination event under the effects of actions taken by utility managers and consumers will be a useful tool for the analysis of alternative threat mitigation and management strategies. This article presents a multiagent modeling framework that combines agent‐based, mechanistic, and dynamic methods. Agents select actions based on a set of rules that represent an individual's autonomy, goal‐based desires, and reaction to the environment and the actions of other agents. Consumer behaviors including ingestion, mobility, reduction of water demands, and word‐of‐mouth communication are simulated. Management strategies are evaluated, including opening hydrants to flush the contaminant and broadcasts. As actions taken by consumer agents and utility operators affect demands and flows in the system, the mechanistic model is updated. Management strategies are evaluated based on the exposure of the population to the contaminant. The framework is designed to consider the typical issues involved in water distribution threat management and provides valuable analysis of threat containment strategies for water distribution system contamination events.