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.     

Design of a new low power MISO multi-mode universal biquad OTA-C filter

ABSTRACT

In this article, a new low-power multiple-input, single-output (MISO) multi-mode universal biquad operational transconductance amplifier-capacitor (OTA-C) filter with a minimum number of active and passive components is proposed. The proposed filter employs three OTAs, one inverter and two grounded capacitors. The proposed filter can realise all filter frequency responses including low-pass (LP), band-pass (BP), high-pass (HP), band-stop (BS) and all-pass (AP) in all operation modes including voltage, current, tranasresistance and transconductance modes using the same topology. Furthermore, sensitivity analysis is done which shows that the proposed filter has a low sensitivity to the values of the active and passive elements. The proposed filter is simulated in HSPICE using 0.18 µm CMOS technology. The HSPICE simulation results demonstrate that the proposed filter consumes only 35 μW at 2.5 MHz from a ±0.5 V supply voltage, while all of the transistors are biased in strong inversion region. Also, the simulation results are in a close agreement with the theoretical analysis which is done in MATLAB. Furthermore, the process, voltage and temperature variation simulations are done to study the effect of non-idealities on the performance of the proposed filter. It is shown that the simulation results justify a 4.8%, 0.8% and 20% variations of the centre frequency for process, voltage and temperature, respectively. Finally, Monte-Carlo, noise and transient simulations are done to justify the good performance of the proposed filter performance.     

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.     

Optimization of Wellhead Location Selection and Well Path Design

Abstract

In the petroleum industry, reservoir operations are generally very costly and most of the oil companies are interested in workflows that help saving the budget by optimizing different steps of filed-developmental planning and decision making, including wellhead location selection and well path design. These steps, in most oil companies, are usually carried out by different departments almost separately, thus calling for further reinvestigations, modifications, and reconsiderations to reach a final optimized plan. The authors introduce a new methodology that thoroughly integrates all the possible data through an available commercial software package (Petrel) and suggests the best possible optimization of wellhead location and well path design only in one run. It is observed that having considered the integration of all types of data available for deciding the field development plan, the well optimizer module of Petrel could be applied to select more optimized wellhead locations, more accurate reservoir targets, and more reliable drilling designs based on drilling cost models, all in one run, which systematically considers all the steps of the process as a whole, giving the best integrated optimized plan.     

Ultrasound and water-mediated synthesis of bis-thiazoles catalyzed by Fe(SD)3 as Lewis acid-surfactant-combined catalyst

Preparation of bis-aminothiazoles under different conditions including synthesis in EtOH under ultrasound irradiation and also in water in the presence of Fe(SD)₃ as Lewis acid-surfactant-combined catalyst (LASC) under ultrasound irradiation has been studied. The results were compared with the traditional reflux method. Also, the results confirmed the efficiency of the synthesis in water and under ultrasound irradiation technique. Moreover, the antibacterial activity of products was investigated using the well-diffusion method against bacterial strains including Micrococcus luteus, Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis. All of the products showed good antibacterial activity against M. luteus and E. coli. Most of the products showed antibacterial activity higher than erythromycin against M. luteus, E. coli, and B. subtilis.     

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.     

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.     

Fabrication of porous NiTi alloy via powder metallurgy and its mechanical characterization by shear punch method

In this study, Porous NiTi shape memory alloy has been produced by mechanical alloying of the elemental Ni and Ti powders. The compacting process was done at two temperatures (warm and cold press) and then sintering at 980 and 1050°C was performed on the specimens. Microstructure and mechanical prop-erties of the samples were investigated by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction. Moreover, shear punch test (SPT) employed to investigate the effect of compaction pressure and sintering temperature on the mechanical properties of the fabricated samples. It was revealed that warm compaction/sintering resulted in 15% yield stress improvement and 20% ultimate tensile strength (UTS) enhancement with respect to conventionally produced specimens. The proposed approach in this paper seems a step forward towards fulfillment of the demand for heavy load-bearing artificial bone.     

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.