Mobilisation of heavy metals by deicing salts in a roadside environment

The seasonal variations of some selected heavy metals (Cd, Cu, Pb and Zn) and principal anions in soil solutions were monitored as a function of distance from the road at two field sites in Sweden. During the winter, the conductivity, concentrations of dissolved sodium and chloride increased dramatically due to the application of deicing agents (i.e. NaCl). Due to ion exchange, the pH decreased one unit in the soil solutions, whereas the concentrations of total organic carbon decreased due to coagulation and/or sorption to stationary solids. The heavy metal concentrations increased during the winter, but through different mechanisms. Cadmium concentrations in the aqueous phase increased as a response to ion exchange, possibly also enhanced by the formation of chloride complexes. Similarly, the concentrations of zinc increased, due to ion exchange, with calcium and protons. The mechanisms of mobilisation for copper and lead were not that clear probably due to association with coagulated or sorbed organic matter in combination with colloid dispersion.     

对广义梁理论中的平面和空间薄壁构件的整体屈曲分析

采用广义梁理论（GBT）对平面和空间薄壁构件进行整体屈曲分析。简要概述主要概念和广义梁理论屈曲分析中所采用的程序。基于广义梁理论的梁有限元分析考虑了4种刚体变形模式,即：i）运动学模型,用于模拟连接2个或更多U型和I型构件节点的翘曲传输作用;ii）采用程序处理构件重心和剪力中心轴（横截面非双向对称）不重合的效应;iii）节点构件的定义,这些节点可提供连接构件的自由度和节点广义位移之间的联系。最后,介绍并讨论数值结果,其可能有助于基于广义梁理论的有限元公式的制定和实施。并将基于GBT分析的结果（临界屈曲载荷和模态）与ANSYS程序中壳单元和梁单元的建模分析结果进行了对比验证。     

几何缺陷对圆钢管上弦张弦梁影响的数值分析

用数值方法分析了圆钢管上弦张弦梁结构几何缺陷在预应力张拉过程中可能造成的力学影响,指出了此型张弦梁结构对平面外几何缺陷的敏感性,并提出了施工中应采取的措施。     

铝型材挤压模离子氮化处理的几个问题的研究

本文通过试验,分析研究了铝型材挤压模离子氮化处理中,工作炉压、工作气氛与氮化效果的关系,以及模具的窄缝处理问题。并由此获得了模具氮化处理的优选工艺。     

从普通梁、扁梁到板带梁

本文介绍一种新颖的高层楼盖结构——板带梁,它将扁梁与无梁楼盖二种技术优点结合起来,变成一种新的梁板体系。这种板带梁克服了无梁楼盖设计中板梁分界线和配筋分区划分的模糊性,又将扁梁的高度再压缩从而又进一步达到加大室内净高或降低层高的目的。     

基于ANSYS的钢筋混凝土浅梁单调加载变形的数值模拟

本文对当前钢筋混凝土梁的有限元模拟进行了概述,以Bresler等人所做试验中两根分别以剪压与弯曲形式破坏的浅梁为研究对象,采用不同的有限元模型及本构模型对其进行了加载过程数值模拟。将数值分析结果与试验结果进行了对比分析,给出差异产生的可能原因,并指出可优选的有限元模型与本构模型;提出梁的极限荷载应结合压区混凝土应变与拉区纵筋拉应力取定,而不能简单取为非线性求解不收敛时施加的荷载值;以单因素分析的方法对影响求解的主要参数的敏感性进行研究。所得结论将有助于推进钢筋混凝土梁数值模拟时参数设置的标准化。     

Application of the Nernst-Planck approach to lead ion exchange in Ca-loaded Pelvetia canaliculata

Ca-loaded Pelvetia canaliculata biomass was used to remove Pb²⁺ in aqueous solution from batch and continuous systems. The physicochemical characterization of algae Pelvetia particles by potentiometric titration and FTIR analysis has shown a gel structure with two major binding groups - carboxylic (2.8 mmol g⁻¹) and hydroxyl (0.8 mmol g⁻¹), with an affinity constant distribution for hydrogen ions well described by a Quasi-Gaussian distribution. Equilibrium adsorption (pH 3 and 5) and desorption (eluents: HNO₃ and CaCl₂) experiments were performed, showing that the biosorption mechanism was attributed to ion exchange among calcium, lead and hydrogen ions with stoichiometry 1:1 (Ca:Pb) and 1:2 (Ca:H and Pb:H). The uptake capacity of lead ions decreased with pH, suggesting that there is a competition between H⁺ and Pb²⁺ for the same binding sites. A mass action law for the ternary mixture was able to predict the equilibrium data, with the selectivity constants α_Ca^H = 9 ± 1 and α_Ca^Pb = 44 ± 5, revealing a higher affinity of the biomass towards lead ions. Adsorption (initial solution pH 4.5 and 2.5) and desorption (0.3 M HNO₃) kinetics were performed in batch and continuous systems. A mass transfer model using the Nernst-Planck approximation for the ionic flux of each counter-ion was used for the prediction of the ions profiles in batch systems and packed bed columns. The intraparticle effective diffusion constants were determined as 3.73 × 10⁻⁷ cm² s⁻¹ for H⁺, 7.56 × 10⁻⁸ cm² s⁻¹ for Pb²⁺ and 6.37 × 10⁻⁸ cm² s⁻¹ for Ca²⁺.     

Design optimization and experimental study on beam string structures

Taking the beam string structure (BSS) in Shanghai Yuanshen Arena as a sample, the rise-span ratio, beam cross-section, area of string, prestressing force of BSS was optimized by using the ANSYS programme. It was proposed that the absolute value of the maximum deflection of the beam under dead load should be minimized in the optimization of the prestressing force. Based on three scale model tests and elastoplastic large deformation analysis, the paper investigated the behavior of BSS in the full-range including the stretching phase, serviceability phase and ultimate load carrying phase. The results showed that the midspan camber should be chosen as the control target of stretching. The failure mode of BSS was the yielding or rupture of the string, while the beam was still in the semi-plastic stage. This paper also presented the construction monitoring results of the real BSS, which satisfied design requirements well.     

钇离子注入对Co—40Cr（wt%）合金氧化行为的影响

研究了Co－40Cr（wt％）合金在空气中、1000℃下的恒温氧化和循环氧化行为。通过SEM／EDXA等测试手段,对合金表面形成的氧化膜进行了分析．并且,与合金表面离子注入3×1016Y ／cm2和3×1017Y ／cm2后的氧化行为进行了比较．结果表明,注钇和未注钇样品氧化后表面形成的都是纯Cr2O3膜,离子注钇明显改善了合金的氧化性能．其原因主要是稀土钇能以离子或细小氧化物颗粒的形式偏聚于Cr2O3晶界,通过阻碍氧化膜中Cr3＋阳离子向外扩散,降低了氧化膜的生长速率．同时,通过阻碍氧化膜／合金界面附近"kirkendall"空洞的形成,增强了氧化膜与合金基体之间的结合强度,提高了氧化膜的粘附性及合金的抗氧化性能．     

A simple method for the measurement of organic iodine in wastewater and surface water

Total adsorbable organic iodine (TAOI) has been used as a surrogate parameter for X-ray contrast media in municipal wastewater. Available methods require specialized equipment for pyrolyzing these compounds to convert the covalently bound iodine into iodide, which is then measured by ion chromatography. In this study we describe a simple method for liberating iodide from these compounds with Cu(II) and hydrogen peroxide. Concentrations of TAOI were measured in wastewater effluent, surface waters that were expected to be impacted by wastewater, and unimpacted surface waters. TAOI concentrations ranged between 1.9 and 16.3 microg/L I in wastewater with a median of 6.5 microg/L I. The lowest TAOI concentrations consistently were detected in a wastewater treatment plant that apparently had few hospitals within its collection area. In comparison, TAOI concentrations in surface water that was unimpacted by sewage were between 0.3 and 3.5 microg/L I. TAOI concentrations in surface waters that were impacted by sewage were consistent with the expected conservative behavior of TAOI.