石英砂掺量对膨润土–砂混合物泥浆样干缩开裂的控制机制

高放废物地质处置工程中,膨润土–砂混合物作为缓冲回填材料的干缩开裂特征对工程屏障的安全性有重要影响。以混合型缓冲回填材料为研究对象,分别制备掺砂率为0%～50%膨润土–砂的浆状试样,通过室内恒温干燥试验,研究混合物的干缩开裂特征。结果表明:当掺砂率小于30%时,混合物的收缩曲线与径向应变曲线均基本重合,石英砂悬浮在膨润土中,混合物的干缩开裂特性由膨润土决定;当掺砂率大于30%时,混合物中石英砂逐渐相互接触,增加了颗粒间的摩擦力且有大孔隙形成,进而能够抑制混合物的干缩开裂。石英砂颗粒的相互接触显著提高了混合物进气值,略微提高了缩限,限制了混合物的干燥收缩。大孔隙的形成导致毛细水作用力的降低;颗粒间摩擦力的增加,增强了混合物抵抗断裂的能力,进而抑制了混合物干燥裂隙的发展。最终确定了抑制膨润土–砂混合物干缩开裂的最低掺砂率为30%。     

Daily concentrations of trace metals in aerosols in Beijing, China, determined by using inductively coupled plasma mass spectrometry equipped with laser ablation analysis, and source identification of aerosols

This paper describes the daily concentrations of trace metals and ionic constituents in the aerosol of Beijing, China from March 2001 to August 2003. Daily PM10 concentrations were also measured from September 2001 to August 2003. The daily average PM10 concentration at Beijing, China from September 2001 to August 2003 was 171+/-117 microg m(-3) (n = 673), which is 5-fold higher than at Yokohama, Japan. Trace metal concentrations were analyzed by using inductively coupled plasma mass spectrometry equipped with a laser ablation sample introduction (LA/ICP-MS), which is a rapid and simultaneous method for multi-element analysis. The daily average metal concentrations in TSP in Beijing from March 2001 to August 2003 were: Al: 3.5+/-2.4 (n = 727), Ti: 0.47+/-0.35 (n = 720), V: 0.013+/-0.010 (n = 716), Cr: 0.019+/-0.015 (n = 618), Mn: 0.24+/-0.16 (n = 730), Fe: 5.5+/-3.9 (n = 728), Co: 0.0046+/-0.0055 (n = 629), Ni: 0.022+/-0.024 (n = 680), Cu: 0.11+/-0.11 (n = 660), Zn: 0.77+/-0.60 (n = 726), As: 0.048+/-0.047 (n = 731), Se: 0.010+/-0.010 (n = 550), Cd: 0.0068+/-0.0082 (n = 709), Sb: 0.033+/-0.036 (n = 687), and Pb: 0.43+/-0.50 (n = 728) (unit, microg m(-3)). All the metal concentrations in TSP in Beijing, China were 1.7-21.8 times higher than those in TSP in the center of Tokyo, Japan. Notably, As concentrations in TSP in Beijing were 20-fold higher than those in Tokyo. Source identification of aerosols in Beijing was carried out by using the chemical mass balance (CMB) receptor model, with the daily concentration of metals in the aerosol. The major primary sources of the aerosol of Beijing were considered to be soil dust and coal combustion. Vehicle exhaust contribution tended to increase.     

Dissolved organic matter, aluminium and iron interactions: precipitation induced by metal/carbon ratio, pH and competition

To better understand the precipitation behaviour of dissolved organic matter induced by interactions with metals, a systematic titration experiment was conducted mimicking the soil solution conditions in an acidic, sandy soil. The variables of interest included the type of metal species (Al, Fe), the redox state [Fe(II), Fe(III)], the pH (3.5, 4.0, 4.5), the metal to organic carbon (M/C) ratio and the competition between Al and Fe. Precipitation of DOM–Al appeared to be strongly correlated with M/C ratio and the pH. For Fe(II) only little precipitation occurred, while the strongest flocculation degree was found after addition of Fe(III). In contrast to Al, hardly any correlation between DOM–Fe precipitation and pH was observed. Both reduction and oxidation of Fe was found and exhibited a strong effect on the precipitated amounts of DOM and Fe. In competition, Al determined the precipitation behaviour at lower M/C ratios (<0.10), while at higher M/C ratios Fe determined the flocculation. Below a M/C ratio of 0.06 Al was the dominant metal in the precipitates, especially at lower pH levels, while the opposite trend was found at M/C ratios above 0.06. Overall, Fe(III) gave the strongest flocculation, although Al influenced the impact of Fe(III) interactions with DOM in relation to pH and M/C ratio.     

水溶性C9石油树脂减水剂的制备及性能研究

将C9馏分、丙烯酸(AA)及马来酸单聚乙二醇酯进行自由基溶液共聚合制备水溶性C9石油树脂减水剂。采用红外光谱法对产物进行了表征和分析,考察了酯化反应条件,聚合反应条件如侧链长度、引发剂用量、反应温度及单体总浓度的影响,并对该减水剂进行了水泥净浆流动度等性能测试。实验结果表明所制备的减水剂具有优良的性能。     

空调分区系统中几种空调方式的探讨

本文首先指出在办公建筑中,合理的进行内外分区是实现温度均匀分布的关键。说明了在空调分区系统中,采用适当的空调方式给内、外区供冷供热,是减小能耗、节约能源的重要措施。其次介绍了三种在空调分区系统中可以采用的节能的空调方式,分别为:利用冷却塔给内区供冷、以乙二醇为载冷剂给内区供冷及采用变风量调节。并根据工程实例详细讲述了这三种空调方式的使用的环境、工作原理及优缺点。指出这三种空调方式都可以充分利用天然能源,减小能耗。     

上海竹园污水一厂混合反应沉淀池设计

上海竹园第一污水处理厂设计采用了化学生物絮凝强化一级处理新工艺,针对其混合池、化学生物絮凝反应池、平流沉淀池等主要构筑物以及主要设备、参数控制的设计方法、设计特点进行了详细介绍.该工艺具有运行稳定、耐冲击负荷、运行成本低的特点.     

上部结构-筏板-地基共同作用分析

本文通过引入厚薄板通用矩形元 ,对框架 筏板 地基进行了共同作用分析 ,着重分析了筏板厚度变化对整个体系的内力和位移的影响     

南京地铁一号线南京站车站隧道设计

地铁南京站采用双洞式隧道过站,隧道埋深浅,控制因素多,先前国内没有类似工程经验,文章通过对设计方案、结构计算及铁路线路防护措施等介绍,为今后类似工程提供设计参考.     

高层建筑多自由度结构体系AVS／D多振型控制

探讨了开关型半主动控制算法的研究现状。基于单步状态预测控制律 ,针对高层结构多自由度结构体系提出了AVS/D多振型开关控制律。通过算例与其它开关控制律的计算机仿真分析和比较 ,表明这种开关控制律是可行的、有效的 ,特别是在多自由度结构体系振动过程中有多个振型同时在受控结构的反应中起主要作用时 ,比其它振型开关控制律有更好的控制效果     

Consistent boundary conditions for flows within the atmospheric boundary layer

In computational wind engineering the neutrally stable atmospheric boundary layer (ABL) is often simulated using the standard k-ε model. The application of boundary conditions that are inconsistent with the profiles used at the inflow boundary causes streamwise gradients in the solution and prevents the simulation of a horizontally homogeneous boundary layer. In the present work these problems are overcome by applying a simple extension of the shear stress boundary condition at the top of the domain and by using one-dimensional models to generate inflow profiles in equilibrium with the ground boundary condition. This procedure allows the impact of the inconsistent boundary conditions to be quantitatively assessed. It is shown that inconsistent boundary conditions at the top of the domain result in erroneous streamwise gradients throughout the domain. These errors are reduced by enlarging the domain in the vertical direction but are not removed. The errors are also found in simulations with idealised and real topography included in the domain. A brief discussion of the impact of the errors on simulations of wind energy projects is given.