ASSESSING LAND USE IMPACTS ON WATER QUALITY USING MICROBIAL SOURCE TRACKING1

ABSTRACT: A renewed emphasis on source water protection and watershed management has resulted from recent amendments and initiatives under the Safe Drinking Water Act and the Clean Water Act. Knowledge of the impact of land use choices on source water quality is critical for efforts to properly manage activities within a watershed. This study evaluated qualitative relationships between land use and source water quality and the quantitative impact of season and rainfall events on water quality parameters. High levels of specific conductance tended to be associated with dense residential development, while organic carbon was elevated at several forested sites. Turbidity was generally higher in more urbanized areas. Source tracking indicators were detected in samples where land use types would predict their presence. Coliform levels were statistically different at the 95 percent confidence levels for winter versus summer conditions and dry versus wet weather conditions. Other water quality parameters that varied with season were organic carbon, turbidity, dissolved oxygen, and specific conductance. These results indicate that land use management can be effective for mitigating impacts to a water body; however, year‐ round, comprehensive data are necessary to thoroughly evaluate the water quality at a particular site.     

电感性本质安全电路L/R的选择原则

基于电感性本质安全电路放电电流线性衰减模型,引入最小建弧电压的概念,得到了放电时间不含未知参数的表达式,利用电感电路的本质安全性能判别式,确定了电感电阻比L/R的选取原则.     

硬盘录象机的最新技术进展

中国科学院自动化所陈龙教授,基于对电视监控技术的长期研究,推出了这篇力作.文章较为全面地概括了DVR的技术现状和发展动向,提出了颇有见地的见解:DVR有可能提升为数字监控主机;MPEG4压缩技术为DVR提供了新的用途;嵌入式网络型DVR正在出现等等.如果文中表述的观点和信息能够为企业或用户提供些许参考,那正是我们作者和编者所祈盼的.     

被控对象动力特性对人操作者手控跟踪效率的影响

人操作者的手动控制能力在人机环境系统的工效研究中具有广泛的应用价值。本文研究了人操作者的手动控制能力，以跟踪时间、跟踪误差和失误率为评价指标；分析不同被控对象动力学特性对人操作者在两自由度跟踪能力的影响。     

人的视觉注意力分配定量测试技术及其应用前景分析

介绍了人的视觉注意力分配的定量测试技术；阐述了实现测试功能的技术手段；举例说明了如何通过测试眼注视点来研究视觉信息获取和分配问题；对其应用前景进行初步分析。     

MEASURING THE CONTRIBUTION OF LAND AND WATER TO AGRICULTURE1

ABSTRACT Irrigated land outproduces dryland agriculture, especially in the western United States. Many valuable crops could not be grown without irrigation. A paucity of yield data does not allow direct measurement of the contribution from irrigated crop agriculture, nor does it allow evaluation of the contributions from livestock which are dependent upon irrigated feed. Regression results indicate that 80 percent of Idaho farm income is associated with irrigation, and that 75 percent of the farm income in the 17 western states is associated with irrigation. For the United States as a whole, results indicate that 13.7 percent of the total cropland (irrigated land) produced 41.3 percent of all cash receipts from farming in 1978. If 14 percent of the land can produce 40 percent of the value of production, can 35 percent of our land produce all our food and fiber needs? Such an allegation has several implications in terms of the adequacy of our land and water resources. It also emphasizes the role of technology in future resource use and production.     

基于地震与危化品突发事件耦合影响的人员转移安置点设置

通过对目前人员疏散转移安置点设置研究现状和问题及城镇化工园区集约发展安全隐患的分析,提出了突发事件耦合影响下人员转移安置点综合规划的必要性。首先分析了典型危化品园区内突发事件耦合的典型模式、影响特性,并基于突发事件耦合特性、影响区域提出了耦合突发事件下人员转移安置点规划的安全性、可达性、适宜性的14个关键影响因素,给出了各指标量化的标准。基于加权灰色关联法和事故影响评估方法,提出了一套安置点适宜性评估筛选、新增安置点规划的方法,给出了安置点规划的流程。利用改进的Voronoi图方法确定安置点的覆盖半径和责任服务区,进行安置点容量与责任区内核密度人口容量的对比分析,以确定安置点人口容量缺口。结合安置点可达性、安全性、适宜性进行叠加划分,确定新增安置点规划位置。最后以某区示范应用,阐述其规划应用方法和流程。以区域内安置点最大全覆盖原则,得到了在地震灾害影响下城镇人员可能受危化品泄漏威胁区域,以及区域安置点的缺口及规划方案。     

Mobile phone use while riding a motorcycle and crashes among university students

Objective: Motorcycle crashes are a significant road safety challenge, particularly in many low- and middle-income countries where motorcycles represent the vast majority of their vehicle fleet. Though risky riding behaviors, such as speeding and riding under the influence of alcohol, have been identified as important contributors to motorcycle crashes, little is understood about the effect of using a mobile phone while riding on motorcycle crash involvement. This article investigates crash involvement among motorcycle riders with risky riding behaviors, particularly using a mobile phone while riding.

Methods: Data were obtained from an online survey of university students’ risky riding behaviors in Vietnam administered between March and May 2016 (n?=?665).

Results: Results show that 40% of motorcycle riders reported to have experienced a crash/fall and nearly 24% of motorcycle riders indicated that they had been injured in a crash/fall. Effects of mobile phone use while riding on safety of motorcycle riders are highlighted. Specifically, more frequent use of a mobile phone for texting or searching for information while riding is associated with a higher chance of being involved in a crash/fall. The results also show that drink riding is associated with a higher chance of being injured.

Conclusions: Overall this article reveals significant safety issues of using a mobile phone while riding a motorcycle, providing valuable insight for designing education and publicity campaigns.