粒径对多孔介质中悬浮颗粒迁移—沉积特性的影响

粒径变化对悬浮颗粒在多孔介质中迁移—沉积过程影响的研究有重要意义。利用自主研发的砂层迁移—沉积模拟试验系统,研究不同粒径的悬浮颗粒在不同尺寸多孔介质中的迁移—沉积特性。结果表明,对于相同尺寸的多孔介质,随着悬浮颗粒粒径的增加,到达相对浓度峰值时间增加,而对应的相对浓度峰值降低;同时,对于相同粒径的悬浮颗粒,随着多孔介质尺寸增大,相对浓度峰值增加;另外,相对于多孔介质,悬浮颗粒粒径的变化对其迁移—沉积过程影响更为显著;随着多孔介质与悬浮颗粒粒径比增大,相对浓度的峰值和终值增大;根据粒径比不同将悬浮颗粒在多孔介质中的迁移—沉积类型划分为“滤饼过滤型”、“迁移—沉积型”、“自由迁移型”3种。研究结果为水源热泵回灌过程中悬浮颗粒在地层中的迁移—沉积特性进一步研究奠定了基础。     

浙江大学新校区体育馆钢屋盖结构设计

浙江大学新校区体育馆钢结构屋盖是由桅杆斜拉索网系统、钢结构屋盖系统、周边支承钢柱系统以及低屋面周边挑檐系统四部分构成,整个结构新颖独特,体系比较复杂。采用多个计算软件对该结构体系进行整体及局部的计算和分析,较为准确地得到了结构体系的受力特征和变形情况,合理布置各处截面,优化了设计。     

北京中关村软件园“光盘”结构分析

中关村软件园光盘结构由四根悬臂柱悬吊巨型双层钢结构盘面组成。采用ANSYS有限元计算软件,分析了88种不同荷载组合下结构的主要受力和变形特性,结构的静力计算结果表明,结构各构件的受力和变形均满足设计控制目标要求。通过动力分析可以发现,结构的第一振型为竖向振动,动力分析结果也满足抗震要求,说明结构形式是合理可行的。     

悬灌连续梁跨越既有道路安全防护措施

以京津城际延伸线(天津至于家堡工程跨蓟港津山联络线)悬灌连续梁施工为工程实例,介绍了采取的安全防护方案,既确保了既有线铁路或等级公路的运营安全,又满足了施工需要。具体介绍了挂篮防护、棚架防护、综合防护方案。     

Seasonal temperature-related variation of humus tank settlement efficiency

This study uses several years of effluent quality data from 43 sites where online monitoring has been operational for many years resulting in the accumulation of high-resolution data sets. The data show a highly repeatable, seasonal dependence of effluent turbidity on temperature. This has been modelled with simple techniques producing a generic model that is neither data hungry nor requires site calibration. Viscosity-based mechanisms are proposed and discussed. These mechanisms differ from conventional assumptions of suspended solids peaks being solely flow related and or ascribed to ‘spring sloughing’. The proposal is that the organic loading of the filter and the physical temperature effects on settlement velocity are both as influential as hydraulic loading in determining effluent suspended solids concentration. Application of the models enables improved design for new/upgraded units and more accurate capacity assessment of trickling filters and humus tanks enabling improved operational risk management of compliance failure.     

室内悬浮颗粒的数值模拟

应用多流体模型和小滑移模型模拟了一个1000级洁净厂房的流场、温度场和颗粒分布,并与实测数据进行了比较,认为在一定条件下多流体模型比小滑移模型更适合模拟洁净室中稀疏悬浮颗粒。     

铝板吊顶、柱、墙面的特点及安装技术

中关村科贸中心电子商场大堂采用静电粉末喷涂银灰色铝合金单板,该板具有表面不易污染、可做成多种形状、安装方便、防火性能好、颜色可调、价格适中等特点,在吊顶、柱、墙面等部位安装后,效果良好。     

城市污水中有机污染物的分布

以城市污水为对象，以0．45μm滤膜，对水中污染物进行分类，利用高效液相色谱(HPIC)对污水中的溶解态有机物分子量分布进行分析，指出该采用的分析方法具有实用价值，研究结果可为城市污水处理工艺的选择提供依据。     

A study of reactive oxygen species in mainstream of cigarette

Reactive oxygenated species (ROS) not only exist in living organisms, they also exist in our environment. Combustion process and photochemical reactions are the major source of environmental ROS, and combustion process produced ROS has been gradually gaining attention in recent years. The purpose of this study is to determine the concentrations of ROS in the mainstream smoke of cigarettes sold in the marketplace using the DCFH2 fluorescence method and to understand particulate and gaseous concentrations of ROS. This research will also discuss the relationship between ROS and nicotine, found in popular cigarette brands, as well as the effectiveness of cigarette filters to remove ROS. Results indicate that the ROS concentration of mainstream smoke is 18.64-54.81 nmol H2O2/l while the correlation coefficients of nicotine and tar to total ROS are 0.959 and 0.909, respectively. Gaseous ROS concentrations are 14.32-39.03 nmol H2O2/l, and make up 71.21-85.99% of the total. It can be clearly seen therefore, that ROS exist mainly in the gaseous phase. Particulate ROS is dominant at PM2.5 (ROS(TSP)/ROS(PM2.5) is 0.652-0.959). The experimental results involving the tobacco leaves and cigarette ash show that ROS in mainstream smoke comes from the combustion process and not from the tobacco leaves. There is no effective means of eliminating ROS from mainstream smoke, regardless of whether a cigarette filter contains active charcoal. PRACTICAL IMPLICATIONS: This study showed that cigarette combustion will produce high concentration of ROS, and this high concentration of ROS in mainstream cigarette smoke probably is one major factor contributing to a high incidence of lung cancer in smokers. Environmental tobacco smoke (ETS) or second-hand smoke is a major indoor air pollutant that could potentially harm non-smokers. We will try to determine the ROS in ETS in the future.     

Gravel Bed Hydroponic Systems Used for Secondary and Tertiary Treatment of Sewage Effluent

Gravel bed hydroponic (GBH) systems planted with
emergent hydrophytes, such as Phragmites australis (the common reed), treat domestic sewage effluents to acceptable environmental standards in an economic and efficient manner. Biochemical oxygen demand (BOD), ammonia, and coliform bacteria can be reduced by over 90% and dissolved oxygen (DO) substantially increased. In temperate zones, such as Europe, GBH systems can be used to replace conventional small rural treatment works, and for tertiary treatment of final effluents. In tropical and arid zones, GBH systems can provide locally-managed, cost-effective alternatives to hightechnology systems which are inappropriate for use in developing countries. Portsmouth Polytechnic reed-bed sewage treatment GBH projects in the UK and Egypt are discussed and current progress is assessed.