Organic pollutants in the effluents of large wastewater treatment plants in Sweden

Effluents from the three largest WWTPs in Sweden were analysed for the presence of organic pollutants by GC-MS. From a total of 137 identified compounds only 10 were priority pollutants. A broad spectrum of non-regulated organic pollutants found in the effluents included aromatic hydrocarbons, food and household related compounds, solvents, plasticisers, flame retardants, preservatives, antioxidants and washing and cleaning related compounds. The concentrations of individual compounds in effluents of all three WWTPs were in the range of 0.5–50 μg/l. Rather few point-discharged pollutants from specific industries were present in the effluents. The majority of pollutants detected in the effluents were attributable to the overall usage and discharge of chemical products in modern society. These pollutants originate from diffuse sources and represent “a background chemical pollution load” of the receiving waters through the discharge from WWTPs in large cities.     

矩形钢管混凝土T型节点极限承载力及其参数分析

矩形钢管混凝土桁架具有整体刚度大、抗震性能好、节点形式简单、施工方便、节点承载力大、造型优美的优点,广泛应用于我国的桥梁和空间结构等大跨、重载结构中。矩形钢管混凝土T型节点常见于Vier-endeel和Fink桁架中,节点的合理与否对结构的安全性与工程造价有很大影响。国内外对其研究虽然开展相对较晚,但已经引起多方面的足够重视。本文应用大型有限元软件ABAQUS对T型节点进行参数分析,以探究各参数影响其静力力学性能的规律。     

某高层框支剪力墙结构的楼板应力分析

以某平面不规则框支剪力墙结构为例,进行多遇地震下的弹性分析和罕遇地震下的弹塑性分析,并就楼盖凹陷处以不设拉板、设拉梁和设拉板三种模型分别对上部标准层平面和带转换层平面进行楼板应力分析,检验其抗震性能。分析表明,拉板模型结构具有良好的受力性能和变形能力,各构件能够达到预期的性能目标。     

Trade-off relationship between public transportation accessibility and household economy: Analysis of subway access values by housing size

This study examines whether different income groups have different trade-off preferences between public transportation accessibility and income and economic power. In this study, apartments, the most typical housing type in Seoul, were categorized according to size (small, medium, and large) based on the premise that apartment size is a measure of the economic status of an individual or household. Subsequently, the effect of subway accessibility on apartment prices for the three types of apartments was examined through the conventional hedonic price model and the spatial autoregressive combined model, followed by an investigation of the spatial patterns of the effect with a focus on a geographically weighted regression. As a result, this study finds that, although subway accessibility serves as a positive factor in housing location decisions for most socioeconomic classes, the positive effect is not spatially unanimous, indicating that households with relatively robust economic stability preferred housing locations further away from subway stations in pursuit of a more attractive residential environment. Although high-income households trade greater accessibility to public transportation for a more attractive neighborhood environment, middle-income households more actively pursued convenience and the greenness of their neighborhoods. Households with less economic stability preferred neighborhoods featuring relatively low-cost housing and greater accessibility. These results confirm the prevalence of trade-off between public transportation accessibility and housing size in Seoul, Korea. This also verifies that the spatial division along economic class lines is intensifying, and that perspectives on subway accessibility vary depending on consumers' economic status. The results suggest the need for consumer-tailored public transportation policies that consider the residential location patterns of the socioeconomic classes that are dependent on public transportation. This perspective can improve our understanding of how to distribute mass transportation systems spaces in large cities, particularly where the wealth gap is relatively high.     

Effect of cationic substitutions on the photoluminescence properties of Eu2+ doped SrCN2 prepared by a facile C3N4 based synthetic approach

An alternative general approach to synthesize carbodiimide materials using carbon nitride as precursor is proposed. This new facile synthetic route was illustrated by the preparation of single phases α-SrCN₂ and β-SrCN₂ in a reproducible and effective manner via the substitution of barium and calcium for strontium. Structural characterizations and optical properties of Eu²⁺ doped SrCN₂ polymorphs were investigated on the bases of high-resolution X-ray powder diffraction and photoluminescence analyses to evaluate the potential of such systems as red phosphors. All Eu²⁺ doped samples exhibit intense red emission in the 620−630 nm range when excited at 440 nm at 77 K with little impact of the crystal lattice on the emission wavelength. However, calcium and barium substitutions for strontium strongly impact the emission intensity and the emission width respectively and all doped samples have their emission intensity reduced by 50 % around 80−90 K and totally quenched at RT.     

门式刚架构造改进型节点试验研究

通过对门式刚架梁柱改进型和常规螺栓端板竖放连接节点的低周往复加载试验,对试件的承载力、滞回曲线、刚度退化和等效粘质阻尼系数及破坏模式等进行研究,且分析了试件破坏的原因.结果表明:经过构造改进的圆弧形整体式和弧形加腋螺栓端板竖放节点比常规节点,向下极限承载力均提高21.4%;刚度损伤明显减小;极限荷载时节点域变形较小,避免了高三轴应力作用下节点的脆性破坏;试件SP-2延性和耗能性能明显得到改善,塑性转角满足延性刚架要求.     

空调房间四种通风方式对污染物分布影响数值模拟与分析

采用RNG k-ε模型对4种侧送风方式下的空调房间进行数值模拟,对室内污染物衰减结果及污染物浓度场进行分析,并通过示踪气体衰减方法计算室内通风效率.结果表明当送回风口位于同侧且在同一垂直面上时室内空气品质最好.     

An autonomous decision support system for manganese forecasting in subtropical water reservoirs

Manganese monitoring and removal is essential for water utilities in order to avoid supplying discoloured water to consumers. Traditional manganese monitoring in water reservoirs consists of costly and time-consuming manual lake samplings and laboratory analysis. However, vertical profiling systems can automatically collect and remotely transfer a range of physical parameters that affect the manganese cycle. In this study, a manganese prediction model was developed, based on the profiler's historical data and weather forecasts. The model effectively forecasted seven-day ahead manganese concentrations in the epilimnion of Advancetown Lake (Queensland, Australia). The manganese forecasting model was then operationalised into an automatically updated decision support system with a user-friendly graphical interface that is easily accessible and interpretable by water treatment plant operators. The developed tool resulted in a reduction in traditional expensive monitoring while ensuring proactive water treatment management.     

A simulation study on the effect of spring-shaped fillers on the viscoelasticity of rubber nanocomposite

Background/PurposeRubber nanocomposites have been widely used in many engineering fields due to their unique properties such as high elasticity and viscoelasticity. Much attention has been paid to the viscoelasticity of rubbers because it directly relates to the performance of the rubber products.MethodsBased on the micromechanical theory, the finite element method is used to analyze the effect of elastic modulus and volume content of spring-shape nanofillers on the dynamic viscosity of composites.ResultsThe simulation results show that there is an optimal elastic modulus of spring-shape nanofillers to make the loss factor a minimum. There is a threshold value of spring-shape nanofiller content for the dissipation energy density of composite.ConclusionThe elastic modulus of spring-shape nanofillers has a large effect on the loss factor of composites. The selection of elastic modulus of spring-shape nanofillers is critical for applications of composites. The efficiency of spring-shape nanofillers in reducing the dynamic viscosity of composites is so high that volume content of spring-shape nanofillers as low as 0.1% can greatly reduce the loss factor of composites with bonding interface.