Imidazolium Based Surface Active Ionic Liquids: Promising Boosters to Enhance the Radical Scavenging and Antioxidant Activity of Conventional Surfactant Solubilised Quercetin

Catalysis Letters - Surface Active Ionic Liquids (SAILs) are emerging as promising alternatives to conventional amphiphiles. Their unique specialties endow the SAIL/SAIL plus conventional...     

同时考虑速度和轴跨比影响时铁路钢桥的影响因子的确定

传统桥梁设计方法中,把交通荷载处理为静载乘以影响因子。依据现行规范,该因子仅是跨度或一阶自振频率的函数。分析各种参数对钢桥动力响应的影响,包括:速度、火车轴距、车轴数、桥跨度,并研究影响因子。计算了火车速度100～400km/h,轴距13～20m,桥跨度10,15,20,25m情况下的动力响应和影响因子。动力分析表明,大多数情况下,算得的影响因子高于相关规范中的值。影响因子随火车速度、火车轴距和桥跨度之比而变化,而车轴数仅在共振时产生影响。给出了速度、车轴距、桥跨度与影响因子的关系。     

Probabilistic seismic assessment of Buckling Restrained Braces and Yielding Brace Systems

The current paper investigates the effectiveness of using an innovative structural fuse named YBS over the Buckling Restrained Brace (BRB) within the context of performance-based earthquake engineering. To this end, two groups of structures equipped with BRB and YBS braces are modeled by OpenSEES platform. In the first part of the paper, simplified procedures including pushover and Incremental Dynamic Analysis (IDA) are utilized for seismic performance evaluation. In the second part, two EDP-based and IM-based probabilistic frameworks are employed to gain a more comprehensive assessment. On this basis, fragility analysis is carried out for different performance levels. Also, limit state frequencies are calculated to compare collapse capacity of both systems. Finally, confidence levels are estimated to study reliability of the structures against collapse. Results show that both systems can achieve the expected performance objectives. However, YBS represent superior performance beyond the sideway collapse performance level.     

Modeling of polymer electrolyte membrane fuel cell with circular and elliptical cross‐section gas channels: A novel procedure

The main objective of this paper is to develop an analytical solution based on the perturbation method to solve the continuity and momentum equations governing the flow in gas channels of a PEMFC having circular and elliptical cross sections. The equations are solved in both the anode and cathode gas channels with appropriately defined perturbation parameters to obtain the velocity profile in these channels. It was observed that by changing the circular cross section to an elliptical one (ie, increasing the value of perturbation parameter), the axial velocity increases. As a result, the penetration of species into the reaction areas decreases. Then, the effect of species penetration speed on the performance of PEMFC is discussed. Increasing the penetration speed (ie, radial velocity) of the reactant gases causes the maximum value of the gas velocity in the channel to decrease. This would imply that the diffusion rate of the reactant species to the reaction areas, and thereby the cell performance would be optimized. Apart from the analytical solution, 3‐D numerical solution of the governing equations using collocated finite volume method along with the SIMPLE algorithm is also performed. The results are validated against the available published data. The numerical results confirm that by converting the circular cross section to the elliptical one, while other conditions are fixed, the PEMFC produces less current density.     

The effect of nano-SiO2 and the styrene butadiene styrene polymer on the high-temperature performance of hot mix asphalt

The production of modified asphalt mixtures with appropriate performance in high temperature has always been under the attention of researchers. One of these modifiers is Styrene Butadiene Styrene (SBS) polymer. Since the application of SBS polymer in bitumen and asphalt mixture does not have expected performance of field due to phase separation of bitumen and polymer, oxidation, and aging, the present study tries to not only improve the polymer defects, but also analyzes its high-temperature performance by using nano-SiO₂ and SBS polymer in bitumen modification. According to the study results, adding nano-SiO₂ and SBS polymer with 3 and 4.5 bitumen weight percent, respectively, to bitumen in asphalt mixture leads to an increase of flow number in dynamic creep test at 50°C for 399 times and at 60°C for 1,015 times compared to unmodified asphalt mix. This, in turn, indicates the considerable improvement of asphalt mixture high-temperature performance.