Chlorination of humic substances in aqueous solution: Yields of volatile and major non-volatile organic halides

In this paper, we present the study of the effect of chlorination contact time, of the chlorine/carbon ratio and of the bromide concentration on the major halogenated products in the case of chlorinated humic substance solutions at neutral pH. The yields of chloroform, of trichloroacetic acid and of dichloro-acetic acid increase with the increase in reaction time and in chlorine dosage. Various values for the yield are given for chlorinated commercial humic acid solutions and for chlorinated solutions of aquatic fulvic and humic acids. The simultaneous presence of trihalomethanes precursors and bromides in the solution leads to the formation of organo-brominated products. Total trihalomethanes increase with the increase of bromide concentration.     

砂岩矿物组分流变特性纳米压痕实验研究

深部地下工程中,关于岩石流变特性对工程结构施工设计和稳定性的显著影响研究较多,但主要是基于宏观非均质岩样进行的,很少涉及岩石细观尺度上的矿物流变特性.采用纳米压痕技术研究砂岩中矿物组分的流变特性和本构方程,结合X射线衍射(XRD)、扫描电子显微镜(SEM)和能谱仪(EDS)获得的矿物组分分布特征,砂岩中石英、钠长石、方...     

基于异型件连接的胶合木网壳节点受力性能研究

为了减轻节点自重同时提高结构美观性,有必要开展新型木网壳节点连接形式研究。以已提出的新型K6网壳销式连接节点作为原始方案,进行2次改进。通过轴压性能试验确定改进方案1的有效性后,对改进节点进行抗弯性能试验。在此基础上提出改进方案2,并采用有限元分析的方法研究因试验条件受限导致的难以同时施加轴压力和竖向荷载的问题。结果表明:改进方案1受安装偏差影响较小,其实际承载力未像原始方案那样低于预期承载力设计值; 节点中的异型钢连接件自重较目前应用较多的网壳节点轻20%～50%,在轴压性能试验中具有较好的弹性变形性能,抗弯性能试验中具有一定的塑性变形性能; 改进方案2节点在轴压和竖向荷载共同作用时的受力性能明显优于竖向荷载单独作用时,说明轴压力对节点抗弯承载力有利; 改进方案2节点抗弯承载力较改进方案1更有优势,经数据优化后提出的钢板厚度建议可为工程设计提供参考。     

LNG储罐外壳自振特性及地震响应分析

主要研究LNG储罐外壳的自振特性和地震响应分析,应用ANSYS建立LNG储罐外壳有限元模型,得到有限元模型的频率、振型、最大相对位移等,选取三种地震波进行了LNG储罐外壳的地震响应分析,得到LNG储罐特殊位置点的位移、加速度、等效应力时程曲线。     

利用AutoCAD确定复杂构件的重量与重心

结合几个工程实例，就如何利用AutoCAD的三维实体功能及相关实体特性查询功能确定复杂构件的重量与重心进行了深入探讨，并提出实际应用中需注意的问题及建议，从而为工程中复杂构件吊装方案的选择奠定基础。     

基于响度级差的建筑构件空气声隔声评价初探

现行建筑隔声评价标准采用计权隔声量作为建筑构件空气声隔声单值评价量。该基于声压级差的隔声参量与主观感受到的隔声量存在差异。采用响度级差作为建筑构件隔声评价新参量,在空气声隔声实验室内,在声源室不同声级条件下,对某建筑构件的空气声隔声响度级差进行测量,并与计权隔声量的测量结果进行对比分析,研究隔声响度级差模型在建筑墙体隔声中的适用性。     

基于时间序列与神经网络的空间网壳结构损伤检测方法

针对网壳结构损伤识别中遇到的模态信息不完备、模态局部化和跃迁现象以及结构自由度巨大所带来的建模精度低等实际困难,提出了一种适用于网壳结构损伤检测的方法——基于时间序列与神经网络的结构损伤检测法.首先,利用ANSYS瞬态分析模块提取结构加速度响应;然后,通过MATLAB(Matrix Laboratory)编程软件建立时间序列自回归模型即AR(Auto-Regressive)模型并提取模型参数,从而判定结构损伤是否发生;最后,对AR模型参数作差并对其进行组合作为损伤特征向量输入到由MATLAB神经网络工具箱建立的BP(Back Propagation)神经网络,对结构损伤进行定位.以凯威特单层球面网壳作为研究对象进行数值模拟,验证该方法的有效性.     

Analysis of the build-up of semi and non volatile organic compounds on urban roads

Vehicular traffic in urban areas may adversely affect urban water quality through the build-up of traffic generated semi and non volatile organic compounds (SVOCs and NVOCs) on road surfaces. The characterisation of the build-up processes is the key to developing mitigation measures for the removal of such pollutants from urban stormwater. An in-depth analysis of the build-up of SVOCs and NVOCs was undertaken in the Gold Coast region in Australia. Principal Component Analysis (PCA) and Multicriteria Decision tools such as PROMETHEE and GAIA were employed to understand the SVOC and NVOC build-up under combined traffic scenarios of low, moderate, and high traffic in different land uses. It was found that congestion in the commercial areas and use of lubricants and motor oils in the industrial areas were the main sources of SVOCs and NVOCs on urban roads, respectively. The contribution from residential areas to the build-up of such pollutants was hardly noticeable. It was also revealed through this investigation that the target SVOCs and NVOCs were mainly attached to particulate fractions of 75-300 μm whilst the redistribution of coarse fractions due to vehicle activity mainly occurred in the >300 μm size range. Lastly, under combined traffic scenario, moderate traffic with average daily traffic ranging from 2300 to 5900 and average congestion of 0.47 were found to dominate SVOC and NVOC build-up on roads.     

网壳锚喷支护理论分析及其在兖州矿区的应用

跨采及软岩巷道地压强度高、变形强烈,支护较为困难。传统支护方式成本高、工艺复杂。根据地面大跨度板壳原理设计出网壳结构,该结构稳定性强,能承受较大变形地压及冲击荷载。钢筋网壳结构是巷道支护工程中一种新型的支护形式,既可在巷道内单独组装对围岩进行连续支撑,又可先撑后喷,在围岩表面形成半刚性钢筋混凝土薄壳衬砌结构。能承受强大变形地压及采动荷载,达到用较少材料又提高喷层支撑能力与让压的目标。介绍了钢筋网壳锚喷支护的技术特色与支护原理,并对其进行理论分析,推导出钢筋网壳锚喷结构的计算模型及其内力与主要应力的计算表达式。完成了室内整架载荷试验,成功应用于兖州矿区跨采巷道。     

基于热网调研的供热管网元件故障率统计与频谱分析

通过对北京、沈阳、哈尔滨及牡丹江的热网运行和故障情况的调查统计，给出了这些城市热网的管道、阀门及波纹管补偿器的分管径故障率数据。对北京和沈阳热网的故障发生规律进行了管径频谱、年频谱及月频谱分析，发现中等管径(DN250～DN400)故障率最高，北京热网故障率随运行年份增加的增长较沈阳慢。北京和沈阳热网元件故障率可作为我国热网可靠性研究的参考数据。