Simulation of carbon dioxide absorption process by aqueous monoethanolamine in a microchannel in annular flow pattern

The process of carbon dioxide absorption by aqueous monoethanolamine solvent was simulated in a microchannel in an annular flow pattern. This simulation has been carried out as a multiphase and three-dimensional process. The effects of different operating parameters such as temperature, superficial gas and liquid velocities, aspect ratio, and concentrations of solvent and solute have been investigated on the mass transfer flux and carbon dioxide conversion. The results of simulating mass transfer flux based on the calculated mass transfer coefficient were well consistent with the experimental data. The result of this study indicated that the mass transfer flux shall increase with the superficial gas and liquid velocities, temperature, concentration of solvent, and increment in the aspect ratio. It also revealed that increasing the concentration of solute would lead to an increase in the mass transfer flux and a decrease in the conversion.     

Enhanced removal of benzene in nonthermal plasma with ozonation,flow recycling,and flow recirculation

A double stage AC/DC sequential high voltage reactor has been developed to study the decomposition of benzene in the air stream at atmospheric pressure. The removal efficiency was measured as a function of ozonation, flow recycling, and flow recirculation. Ozonation in the inlet, and recycling of the exhaust stream increased the removal of benzene, also with increasing of specific input energy (J l⁻¹) the effect of inlet flow ozonation on benzene decomposition was enhanced. The highest removal efficiency was obtained up to >99% in recirculation six times, while CO₂ selectivity reached 99.9% and energy efficiency was 0.59 g kWh⁻¹. O₃ production/ decomposition > production of OH radicals > electronic and ionic collisions were indicated as the main mechanisms influencing benzene abatement in this research.     

An exploration of green supply chain practices and performances in an automotive industry

During recent years, the natural environment has become a challenging topic that business organizations must consider due to the economic and ecological impacts and increasing awareness of environment protection. Globalization and the increased number of countries entering the World Trade Organization (WTO) have promoted green supply chain management (GSCM) practices in manufacturing organizations. GSCM has emerged as an important organizational philosophy and a proactive approach to reduce environmental risks. Increasing pressures such as stricter regulations, increased community, and consumer pressures, and the developing country’s aim to enter the WTO have caused automotive supply chain managers to consider and to implement GSCM practices to improve both their economic and environmental performances. This paper explores the practices and performances of the GSCM based on the GSCM literature, and it considers the relationship between green supply chain practices (initiatives) and performance outcomes. In this paper, two questionnaires were developed and a survey conducted to assess the importance of GSCM practices and performances in an automotive company in a developing country using a fuzzy multiple criteria decision-making method. The result of this paper presents practical guidance for managers in performing GSCM practices by ranking GSCM practices according to their importance which leads to improving GSCM performances.     

Nanostructured AA5005/Al2O3 composite manufactured by anodising and accumulative roll bonding

In this study, nanostructured AA5005/6 vol.-% Al₂O₃ composite manufactured by anodising and accumulative roll bonding (ARB) processes was investigated. The microstructure of the AA5005/Al₂O₃ composite after ninth ARB cycle exhibited a good distribution of alumina reinforcement particles in the AA5005 matrix. It was found that with increasing the number of cycles, the tensile strength of the monolithic and composite samples increased, but their ductility decreased at the first ARB cycle and then increased. The mean grain size of the composite sample after the ninth cycle was 88?nm. The tensile strength of the composite was 3.3 times higher than the initial AA5005 sheet. Observations revealed that the failure mode in the AA5005/Al₂O₃ composite was the shear ductile fracture.     

A hybrid S-N formulation for fatigue life modeling of composite materials and structures

A semi-empirical S-N formulation for the modeling of the constant amplitude fatigue behavior of composite materials and structures is introduced in this paper. The new S-N formulation is based on the commonly used exponential and power law fatigue models. It is a hybrid formulation combining the two existing models in order to improve their modeling accuracy in the low and high cycle fatigue regions. This formulation was applied to a number of fatigue databases for different composite materials and structural elements in order to simulate their fatigue behavior. The modeling accuracy of the hybrid model was compared to the accuracy of commonly used S-N models for composite materials. As proved, the hybrid model performs better in the majority of the examined cases and is able to overcome the disadvantages of previously developed models without introducing any complexity in the fitting procedure.     

Using ARB process as a solution for dilemma of Si and SiCp distribution in cast Al-Si/SiCp composites

A major challenge in achieving the best potential of SiC_p-reinforced aluminum composites is to homogeneously disperse SiC particles within the aluminum alloys. The presence of coarse Si fibers with non-uniform distribution in cast Al-Si alloys, which may lead to poor mechanical properties, is another important problem that limits the application of these alloys. In order to eliminate these problems, accumulative roll bonding (ARB) process was used in this study as a very effective method for improving the microstructure and mechanical properties of the Al356/SiC_p composite. It was found that when the number of ARB cycles was increased, the uniformity of the Si and SiC_p in the aluminum matrix improved, the Si particles became finer and more spheroidal, the free zones of Si and SiC particles disappeared, the porosity of composite decreased, the bonding quality between SiC_p and matrix improved, and therefore mechanical properties of the composites were improved. The microstructure of the manufactured Al356/SiC_p composite after six ARB cycles indicated a completely modified structure so that its tensile strength and elongation values reached 318 MPa and 5.9%, which were 3.1 and 3.7 times greater than those of the as-cast composite, respectively.     

Investigation of Park–Ang damage index model for flexural behavior of reinforced concrete columns

One of the most popular damage indexes for reinforced concrete (RC) members is Park–Ang damage index model. This model has been established on the basis of experimental results of RC beams and columns with different modes of damage. It has considerable uncertainty on the basis of its authors' remarks. In this study, precision of Park–Ang model for RC columns is improved by using some experimental results from Pacific Earthquake Engineering Research information bank. In proposed model, it focused on RC columns with specific sections and collapse modes. Finally, in order to define damage index more exactly in concrete columns under seismic loadings, capability of IDARC‐2D computer program has been improved by this proposed model. Copyright © 2012 John Wiley & Sons, Ltd.     

Comparison of Microparticles and Nanoparticles Effects on the Bonding of Roll Bonded IF Steel

In the present work, the effect of silicon carbide (SiC) particle size on the characteristics of cold roll bonded interstitial free (IF) steel strips, such as bond strength and peeled surface were carried out and compared to those of IF steel strip without particles. The bond strength was evaluated by the peeling test and scanning electron microscopy. It was found that with increasing thickness reduction, the bond strength of IF steel strips improved. The results also indicated that the presence of SiC particles (both micro and nano) decreased the bond strength of IF steel strips. Also, with increasing the particle size, the bond strength improved. It was found that for sample with microparticles compared to sample with nanoparticles, beyond the 80 % thickness reduction, a sudden increase in the average peel strength was observed. Finally, the results indicated that in the presence of nanoparticles between strips there were two types of unbonded area and the bond strength of these two areas was quite similar to each other.     

Comparison of the Microstructure and Mechanical Properties of As-Cast A356/SiC MMC Processed by ARB and CAR Methods

Accumulative roll bonding (ARB) and continual annealing and roll-bonding (CAR) processes were used in this study for improving the microstructure and mechanical properties of the A356/10?vol.% SiC metal matrix composite (MMC) produced by semi-solid metal processing (SSM). The results showed that using the ARB and CAR processes led to the following points: (a) the uniformity of the silicon and silicon carbide in the aluminum matrix improved, (b) the Si particles became finer and more spheroidal in appearance, (c) the porosity disappeared, (d) the bonding quality between the reinforcement and the matrix improved, (e) the particle-free zone disappeared, and therefore (f) the tensile strength (TS), elongation, and formability index of the MMC samples improved. However, it was found that the CAR process is a better method for improvement of microstructure and mechanical properties of as-cast MMC compared to ARB process.     

Effects of porosity gradient of multilayered electrospun nanofibre mats on air filtration efficiency

Performance of the nanofibrous filter media is determined by fibre diameter and pore size distribution of the membranes. In this study, an attempt is made to fabricate a nanofibrous multi-scale filter media by simply varying the layer-by-layer-assisted stacking structure and composition of individual fibres within the single layers. These structural controls of the filter membrane helped to form a skeletal frame-worked membrane with controlled filtration efficiency and pressure drop aerosol particle filtration application. Altering the right electrospinning parameters, layering structure of the membrane resulted in changes in average fibre diameter and pore size distribution, especially in the middle layer of media, while a gradient in pore size and its distribution was created. The results of measurements of pressure drop and filtration efficiency indicated that by changing the gradient in pore size and its distribution in the middle membrane, keeping other layers constant, the pressure drop and filtration efficiency can be effectively tuned. The results suggested that this developed filter media could be used as promising materials for a variety of potential applications in high efficiency particulate air filters with tunable characteristics.