Passive convergence-permeable reactive barrier (PC-PRB): An effective configuration to enhance hydraulic performance

● A novel PRB configuration based on passive convergent flow effect was proposed. ● A 2D finite-difference hydrodynamic model, PRB-Flow, was developed. ● PC-PRB can significantly enhance the hydraulic capture capacity of PRB. ● The PRB geometric dimensions and materials cost are effectively reduced. ● The dominant influential factor of the PC-PRB capture width is pipe length, L_p. A novel permeable reactive barrier (PRB) configuration, the so-called passive convergence-permeable reactive barrier (PC-PRB), is proposed to overcome several shortcomings of traditional PRB configurations, such as high dependency to site hydrogeological characteristics and plume size. The PC-PRB is designed to make the plume converge towards the PRB due to the passive hydraulic decompression-convergent flow effect. The corresponding passive groundwater convergence (PC) system is deployed upstream of the PRB system, which consists of passive wells, water pipes, and a buffer layer. A two-dimensional (2D) finite-difference hydrodynamic code, entitled PRB-Flow, is developed to examine the hydraulic performance parameters (i.e., capture width (W) and residence time (t)) of PC-PRB. It is proved that the horizontal 2D capture width (W_h) and vertical 2D capture depth (W_v) of the PC-PRB remarkably increase compared to that of the continuous reactive barrier (C-PRB). The aforementioned relative growth values in order are greater than 50% and 25% in this case study. Therefore, the PRB geometric dimensions as well as the materials cost required for the same plume treatment lessens. The sensitivity analysis reveals that the dominant factors influencing the hydraulic performance of the PC-PRB are the water pipe length (L_p), PRB length (L_PRB), passive well height (H_w), and PRB height (H_PRB). The discrepancy between the W_h of PC-PRB and that of the C-PRB (i.e., ΔW_h) has a low correlation with PRB parameters and mainly depends on L_p, which could dramatically simplify the PC-PRB design procedure. Generally, the proposed PC-PRB exhibits an effective PRB configuration to enhance hydraulic performance.     

基于心理感知的铁路综合客运枢纽客流疏解预警研究*

为解决铁路综合客运枢纽客流疏解预警忽略旅客心理感知与焦虑问题,基于状态焦虑问卷,定量描述旅客焦虑状态,通过引入心理测量学中积极率划分客流疏解等级阈值,确定枢纽客流疏解预警等级,构建以旅客感知疏解时间为预警指标的回归预测模型。研究结果表明:模型可定量预测枢纽站各种交通接驳方式客流的感知疏解时间,准确描述枢纽站预警等级,研究结果可为管理人员选择相应疏解措施提供依据。     

Computer Usage With Cold Hands; An Experiment With Pointing Devices

Computers are used in the outdoors and in connection with cold store work. Cold hand and fingers limit data input, as studied here. Six input devices; trackballs, pens, and a mouse were tested by 19 participants in a Fitts’ target acquisition task with 2 target sizes under 2 experimental conditions; warm and cold right hand. Measures were acquisition times, number of errors, participant’s preferences, and observed handling of the devices. Effects of device, target size, and cold were significant. Learning and attempts to improve handgrip were confirmed. Large enough targets, a thick pen, and a mouse make computer work practicable in the cold. Direct visual feedback, as with pen on template with target images, shortened acquisition times by half a second.     

一种新型泡沫凝胶成胶时间及灭火特性的实验研究

为研究新型无氨泡沫凝胶的胶凝特性和灭火特点,采用倾斜试管法分别测试了不同反应物浓度、温度、pH值和发泡剂浓度等参数对新型泡沫凝胶成胶时间的影响,同时通过灭火实验对泡沫凝胶的消防特性进行了研究。结果显示：当水玻璃与促凝剂的质量比在1．33—4．0时材料成胶时间满足煤矿灭火要求;pH值在6．9—8．5时成胶最快;成胶时间随温度升高而减小;发泡剂浓度对成胶时间影响不大;泡沫凝胶灭火效果良好且有效延长了复燃周期。因此泡沫凝胶在矿井消防中有很强的实用价值,并且可通过限制反应物浓度、pH值、温度等参数,更高效的控制成胶时间。     

Disconnected futures: exploring notions of ethical responsibility in energy practices

This article aims to explore people's connections to or disconnections from the future and the implications of this for their perspectives on equity, justice and ethical issues related to energy consumption. Everything people do is embedded and extended in time across the modalities of past, present and future, making time an inescapable aspect of our existence, yet one that often remains invisible and intangible. Debates about energy and environmental equity have raised questions about the extent to which people today should bear responsibility for the consequences of their behaviour for future generations. Seemingly intractable difficulties have been identified, however, in people's abilities to connect their present actions with their potential future consequences and thus take on such responsibilities. Drawing on data from interviews about energy consumption practices, this article explores whether people's living temporal extensions through younger generations of their families influence their views and practices around energy use in both the present and anticipated future. Through exploring these issues we offer a contribution to the ethical debate around responsibility for future generations.     

Resistance of Medical Gloves to Permeation by Methyl Methacrylate (MMA), Ethylene Glycol Dimethacrylate (EGDMA), and 1,4-Butanediol Dimethacrylate (1,4-BDMA)

Gloves afford hand protection by minimizing skin contact. The effectiveness of medical gloves to protect against permeation of the monomers, methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDMA), and 1,4-butanediol dimethacrylate (1,4-BDMA), was assessed focusing on permeation rates and degradation of glove materials caused by monomer contact. Fifteen different brands of gloves were tested using a European Standard procedure. Surface images of glove materials before and after exposure to the monomer mixture were obtained using a scanning electron microscope. The standard is not applicable as the only method for estimating the safety of gloves, but it is useful as guideline together with the cumulative permeation of acrylic monomers. Monomer contact on the outside resulted in substantial swelling of most glove materials, and structure changes of the inside surface.     

活性炭复合床层对动活性的影响试验

本文通过对KZ1床层、KZ2床层、KZ1和KZ2复合床层在不同床层厚度条件下,对氯化氰蒸气的动活性进行对比试验,并对试验结果进行分析,得出了后者并非前两者之和,而有了大幅提高的结论。     

Historical Groundwater Trends in Northern New England and Relations with Streamflow and Climatic Variables

Water‐level trends spanning 20, 30, 40, and 50 years were tested using month‐end groundwater levels in 26, 12, 10, and 3 wells in northern New England (Maine, New Hampshire, and Vermont), respectively. Groundwater levels for 77 wells were used in interannual correlations with meteorological and hydrologic variables related to groundwater. Trends in the contemporary groundwater record (20 and 30 years) indicate increases (rises) or no substantial change in groundwater levels in all months for most wells throughout northern New England. The highest percentage of increasing 20‐year trends was in February through March, May through August, and October through November. Forty‐year trend results were mixed, whereas 50‐year trends indicated increasing groundwater levels. Whereas most monthly groundwater levels correlate strongly with the previous month's level, monthly levels also correlate strongly with monthly streamflows in the same month; correlations of levels with monthly precipitation are less frequent and weaker than those with streamflow. Groundwater levels in May through August correlate strongly with annual (water year) streamflow. Correlations of groundwater levels with streamflow data and the relative richness of 50‐ to 100‐year historical streamflow data suggest useful proxies for quantifying historical groundwater levels in light of the relatively short and fragmented groundwater data records presently available.     

城市间运输货车行驶工况构建与应用

为研究城市间运输货车行驶工况特性与典型工况构建方法。运用车载数据采集系统采集了在珠三角区域城市间运输的货运车辆行驶车速等瞬态数据。基于13个工况特征参数解析工况特性,运用运动学片段理论将工况速度数据分成284个工况片,基于主成分分析和聚类分析法将工况片分成5类,选出12片代表工况片,按工况片平均速度从小到大的顺序排列,再将工况时长等比例压缩至1 800 s后最终构建出典型行驶工况。构建工况与实测样本的各项特征参数符合度大于80%,结果表明提出的典型工况构建方法可行,构建工况符合城市间货运车辆实际运行特性。构建工况的最大车速为80 km/h,主要分布在60~80 km/h,C-WTVC工况在0~90 km/h较均匀分布,平均车速为41.0 km/h,较构建工况低15.8%。基于构建工况进行重型货车排放性能仿真测算,得出CO_(2e)排放因子为764.81 g/km,较C-WTVC工况测算值低10.97%,表明运行工况不同导致碳排放测算值有较大差异。     

C2H6/CO2组分构成对瓦斯着火延迟时间的影响规律研究

为进一步研究多种不同性质的气体对瓦斯着火过程的影响,采用CHEMKIN-PRO Release软件,选择CH_4燃烧化学反应机理USC Mech 2.0模型对不同组分构成的C_2H_6/CO_2与甲烷混合气体进行数值模拟,然后分析不同组分下瓦斯着火延迟时间的变化趋势,并利用SENKIN程序对其进行敏感性分析。计算结果表明:当C_2H_6百分比小于CO_2百分比时,随着CO_2百分比的增加,瓦斯着火延迟时间略有增加,且其在T=1200K下延长了17.0%,在T=2200K下延长了8.4%,同时抑制CH_4生成的关键反应步敏感性系数下降幅度略大,其协同抑制瓦斯爆炸;当C_2H_6百分比大于CO_2百分比时,随着C_2H_6百分比的增加,瓦斯着火延迟时间大幅缩短,且其在T=1200K下缩短了63.7%,在T=2200K下缩短了35.5%,同时促进CH_4生成的关键反应步敏感性系数下降幅度大,其协同促进瓦斯爆炸。