Analytical approach on magnetohydrodynamic Casson fluid flow past a stretching sheet via Adomian decomposition method

Flow phenomena of three-dimensional conducting Casson fluid through a stretching sheet are proposed in the present investigation with the impact of the magnetic parameter in a permeable medium. The adaptation of particular transformations is useful to modify the governing equations into their nondimensional as well as the ordinary form. However, these transformed equations are nonlinear and approximate analytical methods for the solution of the complex form of governing equations. In particular, the Adomian decomposition method is proposed for the solution. The behavior of several variables, such as the magnetic and porous matrix, on the flow profile as well as the rate of shear stress, are discussed via graphs and tables. The conformity of the current result with the earlier study shows a road map for further investigation. The major concluding remarks are; the retardation in the velocity distribution is rendered due to an increase in the Casson parameter moreover, the Casson parameter favors in reducing the rate of shear stress coefficient in magnitude.     

Direct high-purity hydrogen production from ammonia by using a membrane reactor combining V-10mol%Fe hydrogen permeable alloy membrane with Ru/Cs2O/Pr6O11 ammonia decomposition catalyst

The hydrogen production capabilities of the membrane reactor combining V-10 mol%Fe hydrogen permeable alloy membrane with Ru/Cs₂O/Pr₆O₁₁ ammonia decomposition catalyst are studied. The ammonia conversion is improved by 1.7 times compared to the Ru/Cs₂O/Pr₆O₁₁ catalyst alone by removing the produced hydrogen through the V-10mol%Fe alloy membrane during the ammonia decomposition. 79% of the hydrogen atoms contained in the ammonia gas are extracted directly as high-purity hydrogen gas. Both the Ru/Cs₂O/Pr₆O₁₁ catalyst and the V-10 mol% Fe alloy membrane are highly durable, and the initial performance of the hydrogen separation rate lasts for more than 3000 h. The produced hydrogen gas conforms to ISO 14687–2:2019 Grade D for fuel cell vehicles because the ammonia and nitrogen concentrations are less than 0.1 ppm and 100 ppm, respectively.     

Effect of Newtonian heating/cooling on free convection in an annular permeable region in the presence of heat source/sink

The influence of Newtonian heating/cooling in the presence of heat source/sink has been investigated on laminar free convective flow in a vertical annular permeable region. The mathematical model for the problem has been considered as a boundary value problem consisting of two simultaneous ordinary differential equations. The boundary value problem has been transformed to nondimensional form. This has given rise to a number of parameters representing both geometrical and physical features of the problem. Closed‐form analytical solutions of the governing equations have been obtained for two different cases of internal heat generation/absorption. To assess the effects of governing parameters on the fluid velocity and temperature, a number of profiles of these field variables have been presented. The efficacy of the distinct processes on the field variables has been discussed extensively. The main outcome obtained in this study is that the velocity as well as temperature is enhanced in the case of the Newtonian heating while the opposite behavior occurs in the Newtonian cooling for both cases of source and sink. Furthermore, the influence of the governing parameters has been shown on the skin friction, volume flow rate, and the Nusselt number.     

水位骤降对下伏隧道堤防安全影响研究

建立了考虑水位骤降条件下的下伏隧道堤防模型,依托湘江某下伏隧道堤防工程,基于堤防边坡渗流原理,结合有限元应力计算,探讨了不同水位骤降速率下的浸润线情况,计算了堤防安全系数。研究结果表明:湘江水位骤降速率越快,浸润线变化范围越大,浸润线变化范围与水位降落速率成正比;湘江水位骤降速度在3 m/d^4 m/d,水位降到28.8 m时,堤岸失去稳定;水位骤降并非整个过程中堤岸均处于失稳状态,而是水位降至某高度后堤岸失稳,骤降速率增快对堤防安全系数有一定负面作用。研究结果对隧道下穿堤防建设具有一定指导意义。     

海藻酸钙固定化零价铁抗团聚及堵塞的作用机制

以海藻酸钠（SA）、氯化钙、微米零价铁（MZVI）为原料，制备了海藻酸钙（CA）固定化MZVI填料（CAZ），通过静态烧杯实验和动态PRB模型实验，探讨了CA运用对Cr(Ⅵ)的去除性能的影响，并通过电镜扫描分析了CA避免团聚、堵塞机制。实验结果表明，CA凝胶颗粒的运用能显著提升MZVI的除Cr(Ⅵ)性能，CAZ相比MZVI对Cr(Ⅵ)的去除率和反应速率分别提升7.1倍、23.0倍；MZVI利用率的提高是CAZ反应器处理Cr(Ⅵ)水量显著大于MZVI反应器的主要原因，MZVI反应速率的提高是CAZ反应器出水Cr(Ⅵ)浓度显著低于MZVI反应器的主要原因。电镜扫描结果表明，SA与氯化钙交联形成的CA具有丰富的骨架孔道结构，具有骨架支撑作用，能有效克服MZVI颗粒因重力作用导致团聚、降低比表面积的缺陷。CA表层固定的MZVI颗粒与Cr(Ⅵ)反应生成的(Fe_xCr_1-x)(OH)₃ 络合沉淀会冲破CA表层外壳，释放到零价铁-渗透反应墙（Fe⁰-PRB）系统中，导致PRB反应初期出现堵塞现象；大部分MZVI颗粒被固定在CA内部，CA内部有较多孔隙结构，这些孔隙结构会控制(Fe_xCr_1-x)(OH)₃ 络合沉淀释放，从而缓解了Fe⁰-PRB后期长期运行持续堵塞的问题。     

Physicochemical and microbial changes during storage of smoke-flavoured salmon obtained by a new method

The aim of this study was to evaluate the effect of a new smoking-salting method employing water vapour permeable (WP) bags on the physicochemical and microbial quality of smoke-flavoured salmon in refrigerated storage. Fresh salmon was subjected to a smoking process in the WP at 5 °C. Physicochemical and microbiological analyses were periodically carried out during the subsequent 40 days of refrigerated storage of the product. The WP bags enabled the evaporation of the exudate during the smoking-salting stage, enabling the drying of the product to take place at the same time. A slight increase of trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) contents was observed over the storage period. The concentration of TVB-N ranged from 14.26 to 21.48 mg N/100 g of fish, values far below the upper limits of acceptability. The low values of the thiobarbituric acid (TBA) index (final level of 0.71 mg MDA/kg) indicate that the lipid oxidation in the smoke-flavoured salmon was limited throughout the period studied. The initial K₁-value was high and only a slight increase was observed during storage. Counts of mesophilic, psychrotrophic, Enterobacteriaceae and lactic acid bacteria were low throughout the study. Given the changes observed for the physicochemical and microbiological parameters, it can be said that no spoilage took place in the smoke-flavoured salmon during the 40 days of storage. This new method could be of interest to producers as it enables smoke-flavoured salmon to be produced to a good standard of hygiene, minimizing handling and reducing processing steps and brine wastes.     

透水理论在新疆某高压隧洞混凝土衬砌结构设计中的应用

鉴于在高水头作用下,采用面力理论设计高压混凝土衬砌结构时存在衬砌厚度过大、含筋率超标严重的问题,以体积力的形式将内水压力施加于混凝土衬砌和围岩,通过建立透水衬砌理论数值计算模型,分析混凝土衬砌的应力应变关系,并按照规范进行限裂配筋。将该方法应用于新疆某水电站发电洞衬砌设计中,并与面力理论的计算结果进行对比,发现采用透水衬砌理论设计高压隧洞的混凝土的配筋量明显减小,降低了工程投入成本。     

温敏型防水透湿聚氨酯的研究进展及应用

温敏型防水透湿聚氨酯为当前智能高分子材料研究的热点之一。介绍了该类聚氨酯的结构和温敏特性,介绍了温敏型防水透湿聚氨酯的研究进展,并对其在纺织、医疗、食品包装等领域的应用前景进行了概述。     

黏土铺盖裂缝淤填固结的理论与试验研究

针对渗透力作用下黏土铺盖裂缝的淤填固结问题,对其固结机理进行阐述。在充分考虑了孔隙比与有效应力、孔隙比与渗透系数的非线性关系条件下,提出了以孔隙比为控制变量的大变形固结微分方程。通过渗透诱发固结试验确定微分方程中的待定系数,该系数综合反映了软黏土初始孔隙比、压缩性、渗透性等随时空变化的影响。采用数值方法求解微分方程,得出了孔隙比在固结过程中随时空的变化规律。采用模型试验模拟了淤填黏土的固结过程并对数值计算结果进行了验证。选择渗漏问题严重的水库进行了现场试验。     

砂衬透水混凝土桩设计与施工

本文讨论了在软粘土地基中设置透水性的混凝土桩 ,可起到“砂井”排水固结作用 ,提高单桩承载力和地基承载力 ,节省工程造价 ,具有很好的推广应用前景