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221.
Ahlstrom U 《Journal of Safety Research》2005,36(2):159-169
INTRODUCTION: Adverse weather conditions have a major impact on National Airspace System (NAS) operations. They create safety hazards for pilots, constrain the usable airspace for air traffic control (ATC), and reduce the overall capacity of the NAS. A system-wide dissemination of weather information to controllers could theoretically improve safety and efficiency. PROBLEM: However, it is currently unclear what weather information would be beneficial for tactical operations. Furthermore, no previous research has empirically evaluated optimal presentation designs for ATC weather displays. Ill-designed weather displays can cause safety hazards by presenting redundant information (i.e., by increasing the cognitive load) and display clutter (e.g., by interfering with the visual extraction of traffic data). METHOD: In the present paper, we outline our use of cognitive work analysis (CWA) techniques for the assessment of weather information needs for terminal controllers. RESULTS: Specifically, we describe how the CWA modeling tools helped us reveal instances in the terminal domain where weather information is lacking or insufficiently disseminated. We used our CWA results to drive the development of weather display concepts and to set up a high-fidelity simulation capability. IMPACT ON INDUSTRY: By means of high-fidelity simulations, we can empirically evaluate controller weather information needs in order to propose weather displays for increased aircraft safety and efficiency of terminal operations. 相似文献
222.
Most soils contain preferential flow paths that can impact on solute mobility. Solutes can move rapidly down the preferential flow paths with high pore-water velocities, but can be held in the less permeable region of the soil matrix with low pore-water velocities, thereby reducing the efficiency of leaching. In this study, we conducted leaching experiments with interruption of the flow and drainage of the main flow paths to assess the efficiency of this type of leaching. We compared our experimental results to a simple analytical model, which predicts the influence of the variations in concentration gradients within a single spherical aggregate (SSA) surrounded by preferential flow paths on leaching. We used large (length: 300 mm, diameter: 216 mm) undisturbed field soil cores from two contrasting soil types. To carry out intermittent leaching experiments, the field soil cores were first saturated with tracer solution (CaBr2), and background solution (CaCl2) was applied to mimic a leaching event. The cores were then drained at 25- to 30-cm suction to empty the main flow paths to mimic a dry period during which solutes could redistribute within the undrained region. We also conducted continuous leaching experiments to assess the impact of the dry periods on the efficiency of leaching. The flow interruptions with drainage enhanced leaching by 10–20% for our soils, which was consistent with the model's prediction, given an optimised “equivalent aggregate radius” for each soil. This parameter quantifies the time scales that characterise diffusion within the undrained region of the soil, and allows us to calculate the duration of the leaching events and interruption periods that would lead to more efficient leaching. Application of these methodologies will aid development of strategies for improving management of chemicals in soils, needed in managing salts in soils, in improving fertiliser efficiency, and in reclaiming contaminated soils. 相似文献
223.
Engineering line diagram development from process flowsheets: Part 1: Shortfalls in current practice
S. Long P. D. B. Bujac D. C. Woodcock M. L. Preston A. G. Rushton I. W. Cumming 《Journal of Loss Prevention in the Process Industries》2000,13(6):459-465
Engineering line diagram (ELD) development forms a distinct phase in process plant design. It is a complex and expensive activity and as such warrants considerable effort to minimise costs and maximise effectiveness. In this paper, the nature of the ELD design task is analysed in order to understand how it could be carried out more effectively. A number of shortfalls in current practice are discussed. These shortfalls were identified through a combination of the following activities: a review of the literature; a survey of current practice and follow-up line diagram development exercise; and task analysis work carried out at ICI. The most significant findings of the survey of current practice are presented. It is proposed that the shortfalls identified can be overcome by introducing structure to the design task. The manner in which this can be achieved is the subject of the second part of this paper. 相似文献
224.
潘奋 《中国安全科学学报》2000,10(5):9-12
阐述安全工程学的基本内容和“安全第一 ,预防为主”的方针。针对当前企业安全生产所面临的道德、心理、安全系统、责任制、监督监察及培训教育等问题 ,探讨了安全工程学与法学、经济学的关系 ,阐明了笔者的观点和研究的思路。 相似文献
225.
罗善明 《中国安全科学学报》2001,11(6):66-68
对有限空间中的淹没非自由射流流压力场的数值解法进行了较为详细的研究和分析 ,并建立了相应的流场力学模型和压力解的第二类边界条件 ,给出了流场的矩形网格几何和边界标记。文中指出 ,精确的压力解只能从泊松形式的压力方程得到 ,且与边界相邻的点和内点应分别采用不同的方程进行求解 相似文献
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为了给工程实际应用提供科学依据,文章以煤渣、页岩陶粒、砾石、砂子为吸附剂,以苯、1,4-二氯苯、硝基苯和邻苯二甲酸二丁酯4种有机化合物为吸附质,考察了人工湿地基质对混合溶液中有机化合物的等温吸附行为。结果表明,供试基质对目标有机化合物的吸附等温线均属于Langmuir型;Freundlich方程比Langmuir方程能够更好地拟合实验结果;Langmuir方程的不同线性变换在数据拟合时表现出很大的差异性;供试基质对有机化合物的吸附具有明显的选择性,最好用混合基质来构建以去除有机化合物为目的的人工湿地。 相似文献
230.
有机污染物在HDPE膜-膨润土复合防污帷幕中的一维扩散解析解 总被引:2,自引:0,他引:2
HDPE膜-膨润土复合防污帷幕被认为是目前最为安全有效的地下污染源阻隔技术之一.针对帷幕底部嵌入不透水层和帷幕下游地下水较为活跃的工况,推导了有机污染物在HDPE膜-膨润土复合防污帷幕三层结构中的一维扩散解析解.利用本文的解析解分析了HDPE膜-膨润土复合帷幕对亲水性和疏水性两类有机污染物的阻隔效果.分析结果表明:由于亲水性有机物与HDPE膜间的分配系数低,该复合防污帷幕对其阻隔效果显著优于具有高分配系数的疏水性有机物.对于疏水性有机物,可通过增大复合帷幕中膨润土的阻滞因子和帷幕厚度来改善其阻隔效果;膨润土的阻滞因子增大10倍且帷幕厚由0.6m增大为1.0m,改进后复合帷幕对疏水性有机物的阻隔效果可达到原帷幕对低分配系数亲水性有机物的阻隔水平.工程实践中可通过对HDPE膜进行表面处理以降低其分配系数或膨润土改性以增大其阻滞因子等措施来增强该复合帷幕的阻隔效果. 相似文献