超声波辅助提取雨水管道沉积物中磷的存在形态

在SMT法的基础上采用超声波技术对实验条件进行优化,用于雨水管道沉积物中磷的提取。通过对提取时间、提取温度等影响提取效率的因素进行分析,确定了提高闭蓄态磷提取效率的条件,从而建立了管道沉积物中磷形态分析的最佳条件。在确定的最佳提取条件下对北京城区雨水管道内沉积物中磷的存在形态进行提取,并对不同形态磷的污染水平和分布状况进行分析,结合环境状况等因素对不同形态磷的污染特性进行了综合研究。     

Effect of oxide-based fluxes on mechanical and metallurgical properties of Dissimilar Activating Flux Assisted-Tungsten Inert Gas Welds

Present investigation is to study the “Effect of Activating Fluxes on Mechanical and Metallurgical Properties of Dissimilar Activated Flux-Tungsten Inert Gas Welds”. Effect of current, welding speed, joint gap and electrode diameter on weld bead dimensions on 6 mm thick dissimilar weld between carbon steel to stainless steel, was studied under Activated Flux-Tungsten Inert Gas Welding process. During this investigation three different types of oxide powders were used-TiO₂, ZnO and MnO₂. After welding samples were subject to mechanical testing, in addition to characterization via micro hardness and microstructures of Normal Tungsten Inert Gas Welds and Activated Flux-Tungsten Inert Gas Welds. Activating fluxes TiO₂ and ZnO are effective fluxes for Activated Flux-Tungsten Inert Gas Welding of dissimilar weld between CS to SS. Highest depth/width (D/W) ratio reported under TiO₂ and ZnO fluxes compare to Normal-Tungsten Inert Gas Welds. Lowest angular distortion was observed under TiO₂ flux compare to Normal-Tungsten Inert Gas Welds. Mechanical properties, Joint Efficiency of Activated Flux-Tungsten Inert Gas Welds are higher than normal-Normal Tungsten Inert Gas Welds. Tensile Test specimens of both the processes failed from the parent metal (carbon steel side). Carbon migration from CS to SS, had occurred which led to failure of weld joints from CS side.     

Microstructure of 2205 duplex stainless steel joint in submerged arc welding by post weld heat treatment

The 2205 duplex stainless steel (DSS) is of both good properties austenitic steel and ferritic steel, which applies to the shipbuilding industry usually. In this paper, the OM, XRD and microhardness test methods are used to analyze the variation of submerged arc welded (SAW) joints with and without post weld heat treatment (PWHT). The research results show that the σ phase disappear in the fusion edge zone near heat affect zone (HAZ) and an increase in the welded center zone during the follow-up PWHT, while the amount of γ phase is decreased in the welded center zone with PWHT. A segregation distribution of some second phases is also found in the welded center zone after PWHT. There have two pick values of microhardness arise in the fusion edge zone and the welded center zone separately without PWHT. However, a maximum value of microhardness at the fusion edge zone near HAZ is disappeared and the other is still held at the welded center zone during PWHT. It can be attributed to the changes of second phases, element diffusions and particle segregation during PWHT. A developing mechanism is issued to demonstrate the second phases transferring of the 2205 DSS SAW joints by PWHT.     

我国生态环境资产负债表编制框架研究

本文根据生态环境资产负债表的基本概念和理论,提出了生态环境资产负债表编制的总体框架,同时,针对环境容量资产、环境质量产品、生态产品资产的特点,分别建立了相应框架体系,提出了环境资产负债表的应用决策方向。本文研究成果对于确立统一的生态环境资产核算标准和方法、使我国生态环境资产负债核算工作逐步规范化、制度化具有重要的现实意义。     

45~#钢在西双版纳大气环境下的腐蚀研究

目的研究西双版纳热带雨林地区大气环境下材料的初期腐蚀行为。方法使用45#碳钢在西双版纳大气环境下进行1年的大气暴露腐蚀试验,并利用质量损失分析、SEM、XRD和FTIR等技术,分析45#碳钢在西双版纳大气环境下暴露1年的腐蚀行为。结果 45#碳钢的腐蚀产物以γ-FeOOH,Fe(OH)3和Fe3O4为主,并有少量的α-FeOOH。结论西双版纳大气环境腐蚀性为C2级。在暴露1年的时间内,锈层化学稳定性随试验时间的延长逐渐增强,对基体的保护性逐渐加大。     

某大型钢结构项目喷涂废气污染防治措施可行性分析研究

钢结构建筑是一种新型的节能环保的建筑体系,大多数大型钢结构产品在生产过程中均需要进行抛丸除锈、喷涂处理,使用油漆进行喷涂过程中将不可避免地产生含TVOC(主要为甲苯、二甲苯和非甲烷总烃)的有机废气。大型钢构类生产项目喷涂废气的收集和处理尤为困难。文章结合某大型钢结构生产企业实际采取的喷涂废气治理方法进行喷涂废气污染防治可行性分析,旨在为同类项目喷涂废气污染治理及进一步改良涂装废气治理工艺和技术提供参考依据。     

双层板桁钢梁应力分析

以跨度最大的双层斜拉桥闵浦大桥为背景,研究了双层板桁钢梁桥面板的受力特性,阐述了精细壳单元与梁单元结合的整体有限元模型,并分析了上、下桥面间腹杆的受力特性与桥面板的应力分布特性;采用桥面纵横梁间带U肋精细桥面模型,分析了桥面板和U肋在车辆荷载作用下的应力分布.研究表明,上、下层桥面横桥向应力小于纵桥向应力,并且横桥向应...     

设置限位器双向隔震铁路桥梁车桥耦合动力响应研究

对铅芯橡胶双向隔震铁路桥梁在列车荷载作用下的力学性能进行了研究,针对双向隔震铁路桥梁中存在的问题,提出了设置限位器的解决方案,并对设置限位器的双向隔震铁路桥梁进行了车桥耦合动力响应分析.研究结果表明,采用常规隔震设计方法的铅芯橡胶支座在横桥向的初始刚度和屈服强度均不能满足规范要求,设置限位器后,双向隔震铁路桥梁的力学性...     

地基弹性参数对于长型大截面地下结构横向自由振动的影响

自由振动分析是地下结构地震动力响应分析的基础.本文利用笔者先前得到的长型地下结构的自由振动方程,研究了地基弹性参数对地下结构自由振动的影响.由分析可以看出,随着地基弹性参数值的增加,结构中波速值总的趋势是增加,但是温克尔地基参数对结构中波速的影响远大于第二地基参数的影响;地下结构振动频率总的趋势是随着温克尔地基参数(k...     

下翼缘摩擦式自定心钢框架梁柱节点抗震性能的数值模拟

介绍了一种新型的钢框架梁柱节点形式,其中预应力钢绞线提供了结构在地震作用下的复位功能(自定心),设置在梁端下翼缘的摩擦件则为结构提供了耗能能力;介绍了下翼缘摩擦式自定心钢框架梁柱节点的构造和工作原理,以节点的低周反复加载试验结果为依据,利用面向对象的开放式计算程序OpenSees建立了节点的数值模型,并侧重于模拟节点在...