Fluidisation characteristics of granular activated carbon in drinking water treatment applications

Granular activated carbon (GAC) filtration is an important unit operation in drinking water treatment. GAC filtration is widely used for its filtration and adsorption capabilities as a barrier for undesired organic macro- and micro-pollutants. GAC filtration consists of two successive phases: adsorption and filtration, capturing the impurities from the water in conjunction with a backwash procedure in which the suspended particles are flushed out of the system. Available literature predominantly focusses on adsorption. A less frequently discussed but nevertheless equally crucial aspect of this operation is the backwash procedure of GAC beds. To prevent accumulation of suspended particles and to avoid additional operation costs, optimal backwashing is required. Another factor is sustainability: water utilities are showing increasing interest in exploring new sustainable GAC media. As these have different bed expansion tendencies due to different GAC characteristics with varying geometries, operational developments are needed for prediction models to estimate the expansion degree during backwashing. The prediction of the bed expansion of GAC is complex as the particles are non-spherical, porous and polydisperse. Through a combination of advanced particle laboratory and fluidisation experiments, we demonstrate a new approach which leads to an improved expansion prediction model for the backwashing of GAC filters.     

径向弹簧蓄能密封结构最大接触应力的有限元分析

为研究径向弹簧蓄能密封结构的密封特性，针对典型径向弹簧蓄能密封结构，分析其密封机制以及O形弯曲金属螺旋弹簧的弹性特性；采用ANSYS有限元分析软件，建立典型弹簧蓄能密封结构的非线性有限元分析模型，对弹簧蓄能密封圈在不同压缩率、不同介质压力下的接触应力进行分析，研究在多种工况下最大接触应力的变化情况。结果表明：压缩率保持不变时，最大接触应力随着介质压力的增大而增大；介质压力保持不变时，随着压缩率的增大，最大接触应力先增大再减小。对压缩率、介质压力与最大接触应力的关系进行曲线拟合，可用于指导弹簧蓄能密封结构的精确设计。     

Effect of hydrothermal aging on dental multilayered zirconia for monolithic restorations: An in vitro study

The aim of this in vitro study was to investigate the changes in mechanical, optical, and surface properties of multilayered zirconia during hydrothermal aging.One conventional block (Katana Zirconia HT) and three multilayered blocks (Katana Zirconia ML, STML, and UTML) of monolithic zirconia were examined. Bar-shaped specimens were autoclaved at 134°C and 0.2MPa for 0, 5, and 10 h. The Young's modulus, three-point flexural strength, and nanoindentation hardness were measured to evaluate the mechanical properties. The surface roughness, phase distribution, surface microstructure, and elemental composition were measured to analyze the surface properties. The contrast ratio and total transmittance were measured via spectrophotometry to evaluate the optical properties. Statistical differences were analyzed using appropriate ANOVA, Tukey HSD post hoc tests, and independent and paired sample t-tests (α = .05).The monoclinic phase increased gradually after hydrothermal aging. The yttrium and zirconium concentrations decreased, and the oxygen concentration and the surface roughness increased in all specimens (P<.05) after the aging process. All specimens showed significant grain push-out and microcracks. The total transmittance increased, and the contrast ratio and Young's modulus decreased in all specimens (P<.05) after the aging process. The nanoindentation hardness and three-point flexural strength exhibited a decreasing tendency after the aging process. However, there were no statistical differences (P>.05) between the materials. Significant interactions between material grades and hydrothermal aging were found for all the properties studied (P<.001).Microstructural alterations and significant phase transformations were detected on the surface of the multilayered zirconia after hydrothermal aging. The hydrothermal aging led to increased surface roughness, opaqueness, and elasticity of multilayered zirconia. The optical, mechanical, and surface properties of multilayered zirconia were influenced by the grade of the material after hydrothermal aging. Careful consideration of the grade of materials is necessary for the appropriate selection of multilayered zirconia ceramics for monolithic restorations.     

热烫温度对小麦面团介观特性的影响机制

本实验以热烫面团为研究对象，通过凯氏定氮法、粒径分析、傅里叶变换红外光谱以及快速黏度分析等手段，研究55、65、75、85 ℃和95 ℃热烫温度下小麦面团中麦谷蛋白大聚体的质量分数、粒径分布、蛋白质二级结构以及面团中淀粉的糊化特性的变化情况。结果表明：随着热烫温度的升高，面团中麦谷蛋白大聚体质量分数呈现显著增大的趋势（P＜0.05），小粒径的麦谷蛋白大聚体向中粒径和大粒径转变；面团中蛋白质二级结构发生变化，部分α-螺旋和β-折叠结构转变为β-转角和无规卷曲。同时，面团中淀粉的糊化度随着热烫温度的升高逐渐增大；淀粉的峰值黏度、最低黏度、衰减值、最终黏度、回生值和峰值时间均呈现出减小的趋势，在热烫温度高于75 ℃时，这种变化更加显著。     

饱和尾粉砂边界面模型在FLAC3D中的开发

由于岩土材料的复杂性，FLAC3D软件自带的本构模型不能满足实际数值分析的全部要求。利用FLAC3D预留的UMD接口，在C++的编译环境下实现了一种基于临界状态模型CASM边界面模型的开发。介绍了边界面模型的基本组成，给出了开发的关键步骤。并基于三轴试验结果，利用该模型对饱和尾粉砂静/动力学特性进行了分析，论证了该模型对饱和尾粉砂的适用性。     

大豆油体蛋糕的制作及品质分析

目的 为比较大豆油体、单甘脂和蔗糖酯三种成分对蛋糕烘焙学特征的影响。方法 本文通过对蛋糕面胚比容、质构，蛋糕面糊比重、黏度和表面气孔特性以及理化指标检测，并对蛋糕进行感官评定进行测试。结果 结果表明，大豆油体最适添加量为4.5%。大豆油体能增加蛋糕的黏度，有助于形成稳定的乳化体系，并且大豆油体蛋糕的酸价、过氧化值和反式脂肪酸检测结果符合国家标准。结论 大豆油体和乳化剂能显著提高豆乳奶油蛋糕的比容，降低硬度，从而改善蛋糕的品质特性。     

Numerical investigation of the effects of H2/CO/syngas additions on laminar premixed combustion characteristics of NH3/air flame

Co-firing NH₃ with H₂/CO/syngas (SYN) is a promising method to overcome the low reactivity of NH₃/air flame. Hence, this study aims to systematically investigate the laminar premixed combustion characteristics of NH₃/air flame with various H₂/CO/SYN addition loadings (0–40%) using chemical kinetics simulation. The numerical results were obtained based on the Han mechanism which can provide accurate predictions of laminar burning velocities. Results showed that H₂ has the greatest effects on increasing laminar burning velocities and net heat release rates of NH₃/air flame, followed by SYN and CO. CO has the most significant effects on improving NH₃/air adiabatic flame temperatures. The H₂/CO/SYN additions can accelerate NH₃ decomposition rates and promote the generation of H and NH₂ radicals. Furthermore, there is an evident positive linear correlation between the laminar burning velocities and the peak mole fraction of H + NH₂ radicals. The reaction NH₂ + NH <=> N₂H₂ + H and NH₂ + NO <=> NNH + OH have remarkable positive effects on NH₃ combustion. The mole fraction of OH × NH₂ radicals positively affects the net heat release rates. Finally, it was discovered that H radicals play an important role in the generation of NO. The H₂/CO/SYN additions can reduce the hydrodynamic and diffusional-thermal instabilities of NH₃/air flame. The NH₃ reaction pathways for NH₃–H₂/CO/SYN-air flames can be categorized mainly into NH₃–NH₂–NH–N–N₂, NH₃–NH₂–HNO–NO(?N₂O)–N₂ and NH₃–NH₂(?N₂H₂)–NNH–N₂. CO has the greatest influence on the proportions of three NH₃ reaction routes.     

Investigation on hydrogen-fueled combustion characteristics and thermal performance in a micro heat-recirculation combustor inserted with block

Numerical investigation on the premixed H₂/air combustion in a micro heat-recirculation combustor inserted with/without block is conducted. Effects of block setting, heat-recirculation, and flow rate on combustion characteristics and thermal performance are depicted and analyzed. The results demonstrate that the block enhances the flame stability and preheating effect, which also reduces the heat loss via exhaust gas, while it shortens reactants residence time. The combustor setting with a transverse block gains a better thermal performance than that inserted with a longitudinal block. With the increase of transverse block height, the high-temperature zone is broadened and radiation is improved. However, the block with a height of 10 mm separates the fluid field and weakens the effects of heat recirculation, leading to a lower outer wall temperature. Furthermore, the appropriate block insertion method and height contribute to the significant improvement of heat transfer, radiant efficiency and further optimization of micro power generator.     

Charging strategy through analysis of charging influence factors of ultra-light hydrogen storage with polyethylene terephthalate liner

A lightweight type 4 vessel with a polyethylene terephthalate (PET) liner is analyzed. The derived heat transfer coefficients between the gas and wall are applied, and a parametric study is performed. An optimized charging strategy is also developed. Firstly, when the injected hydrogen temperature decreases, the charging time increases, and the charged gas temperature decreases. Secondly, the higher the ambient temperature, the shorter the charging time, and the higher the charged gas temperature. Thirdly, the larger the mass flow rate, the shorter the charging time, and the higher charged gas temperature. Fourthly, as the initial pressure inside the vessel increases, the charging time shortens, and the charged gas temperature decreases. Fifthly, using the formulated charging strategy, during summer, the charged gas temperature decreases by approximately 9 °C. In winter, the charging time is reduced by approximately 58 s. The results provide important information of temperature control for ensuring vessel safety.