Analytical determination of permeability of porous fibrous media with consideration of electrokinetic phenomena

Flow behavior in porous fibrous media with consideration of electrokinetic phenomena is investigated based on a linearized Poisson–Boltzmann equation and Navier–Stokes equation. An analytical solution of effective permeability of porous fibrous media as functions of porosity, dimensionless local averaging net charge density and dimensionless electric resistance number is derived in this paper. The influences of the electrokinetic phenomena can be measured by the dimensionless electric resistance number, which is proportional to the square of the liquid dielectric constant, the solid surface Zeta potential and inversely proportional to the liquid dynamic viscosity, electric conductivity and the square of the maximum pore radius. The analytical results show that when the dimensionless electric resistance number is small and the porosity is large, the dimensionless total flow rate shows a nearly uniform distribution. When the dimensionless electric resistance number is large, the resistant effects of the electrical double layer (EDL) become so significant that the superficial velocity decreases. The effective permeability of the porous fibrous media decreases correspondingly. Furthermore, the theoretical predicted effective permeability values are compared with experimental data, and good agreement is observed between the two. It shows that the mathematical model for the effective permeability of porous fibrous media with consideration of electrokinetic phenomena is satisfactory.     

Experimental study of forced convective boiling for non-azeotropic refrigerant mixtures R-22/R-124 in horizontal smooth tube

In this article, the experiment is carried out with four stages of test section and new experimental data of non-azeotropic refrigerant mixtures R-22/R-124 are presented. Existing correlations are analysed and new ones are proposed for pure refrigerants. The nucleate boiling correlation of the refrigerant mixtures is modified so as to obtain the evaporation heat transfer coefficient of the refrigerant mixtures in a smooth tube. The result shows that the majority of the predictions fall within ±30% of the experiments.     

Photoelectrochemical hydrogen production at peak efficiency over 10% via PbSe QDs/TiO2 nanotube array photoanodes

Modulating the deposition of quantum dots onto TiO₂ nanotube arrays provides an effective approach for expansion of visible light response, enhancement of separation and interfacial transfer of photoinduced charge carries, and improvement of photoconversion efficiency. In this paper, titanium dioxide nanotube arrays (TNAs) were modified with PbSe quantum dots (QDs) through the successive ionic layer adsorption and reaction (SILAR) under nitrogen to prepare PbSe/TNAs photoanodes. XRD, SEM, HR-TEM, UV–Vis–NIR DRS, PL, XPS, EIS, Tafel plots, Mott–Schottky analyses and J–V characteristics were used to characterize the samples. The deposition of PbSe QDs was tuned by varying the Se/Pb atomic ratios during the SILAR process. Energy band configuration, interfacial contact characteristics and photoelectrochemical properties were dissected and optimized. At the Se/Pb ratio of 5, the sample (5)PbSe/TNAs demonstrated excellent photoelectrochemical performance with a short circuit photocurrent density of 15.45 mA cm^?2 and a corresponding photoconversion efficiency of 10.6%.     

Corrosion Behavior of High Nitrogen Nickel-Free Fe-16Cr-Mn-Mo-N Stainless Steels

The purpose of the current study is to develop austenitic nickel-free stainless steels with lower chromium content and higher manganese and nitrogen contents. In order to prevent nickel-induced skin allergy, cobalt, manganese, and nitrogen were used to substitute nickel in the designed steel. Our results demonstrated that manganese content greater than 14 wt pct results in a structure that is in full austenite phase. The manganese content appears to increase the solubility of nitrogen; however, a lower corrosion potential was found in steel with high manganese content. Molybdenum appears to be able to increase the pitting potential. The effects of Cr, Mn, Mo, and N on corrosion behavior of Fe-16Cr-2Co-Mn-Mo-N high nitrogen stainless steels were evaluated with potentiodynamic tests and XPS surface analysis. The results reveal that anodic current and pits formation of the Fe-16Cr-2Co-Mn-Mo-N high nitrogen stainless steels were smaller than those of lower manganese and nitrogen content stainless steel.     

离心光散射法测定乳液液珠大小与分布

用日本 Shimadzu SA-CP3型粒度分布仪测定由低分子量挥发性有机物构成的 O/W型和 W/O型乳液中液珠大小与分布。讨论了稀释液种类、稀释倍数和离心速度对测试结果的影响     

广州地铁黄村站联动调试工程项目管理要点

地铁站设备联动调试是项目管理的最后一关,直接关系到产品、设备功能和安装质量能否满足地铁站使用功能及各项功能的设计要求,为日后设备在最佳状态下运行创造先决条件,文中实例因涉及多个专业承包商而成为联动调试的一大难点。     

对中国基础设施和公用事业中公私协作机制的现状观察和思考

通过介绍当前经济危机下,中国交通、能源、水务环保等基础设施领域的国进民退现象,揭示了市场化改革为何受到质疑的深层原因。通过对公共物品的经济属性和提供机制的分析,指出集体物品既可以由公共部门直接生产,也可以由其他制度提供。最后展望了中国基础设施PPP事业的前景,提出了政策建议。     

Mining the co-movement in the Taiwan stock funds market

Mutual funds are an essential tool for investors looking to diversify their investments. Facing various mutual funds, it is necessary to evaluate their performances. This study uses association rules to understand the relationships among various mutual funds. First, equity funds are categorized into high, medium and low risk levels. This study then evaluates the co-movement among funds within the same risk level and among funds across different risk levels. This study concludes that within any given risk level, the performances of at least seven funds exhibit strong co-movement. This study also shows the influence of the global economy on the correlations among different funds. Finally, investment recommendations are provided based on the findings.