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Farahany S.,Buein Zahra Technical University | Ourdjini A.,University of Ottawa | Bakhsheshi-Rad H.R.,University of Technology Malaysia
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2016

The microstructure evolution, mechanical and corrosion properties of Al-11Si-2Cu-0.8Zn die cast alloy treated with Bi, Sb and Sr additions were investigated. The results of mechanical testing showed that all additions increased impact toughness, ultimate tensile strength, and elongation of the alloy as a result of change in eutectic Si morphology. The analysis of fracture surfaces revealed that with addition of Sr and to lesser extent Bi and Sb, the alloy exhibited a predominantly ductile fracture rather than quasi-cleavage brittle fracture. Moreover, with the additions of Sr, Bi and Sb, the quality index increased to 164.7 MPa, 156.3 MPa and 152.6 MPa respectively from 102 MPa for the base alloy. Polarization corrosion tests conducted in sodium chloride solution showed that the corrosion potential shifted to more negative values with additions of Sb, Bi and Sr, respectively. Corrosion immersion tests also revealed that the element additions have a detrimental effect on the corrosion rate of alloys, due to the increase of boundaries between the Al and eutectic Si phases. © 2016 The Nonferrous Metals Society of China.

Alahyarizadeh Gh.,Shahid Beheshti University | Amirhoseiny M.,Shahid Beheshti University | Amirhoseiny M.,Buein Zahra Technical University | Hassan Z.,University of Technology Malaysia
International Journal of Modern Physics B | Year: 2015

The performance characteristics of deep violet indium gallium nitride (InGaN) multiquantum well (MQW) laser diodes (LDs) with an emission wavelength of around 390 nm have been investigated using the integrated system engineering technical computer aided design (ISE-TCAD) software. A comparative study on the effect of quantum well (QW) thickness and number on electrical and optical performance of deep violet In0.082Ga0.918N/GaN MQW LDs have been carried out. The simulation results showed that the highest slope efficiency and external differential quantum efficiency (DQE), as well as the lowest threshold current are obtained when the number of wells is two. The different QW thickness values of 2.2, 2.5, 2.8, 3 and 3.2 nm were compared and the best results were achieved for 2.5 nm QW thickness. The radiative recombination rate decreases with increasing QW thickness because of decreasing electron and hole carrier densities in wells. By increasing QW thickness, output power decreases and threshold current increases. © 2015 World Scientific Publishing Company.

Taheri S.M.-R.,Institute for Advanced Studies in Basic Sciences | Madadi E.,Buein Zahra Technical University | Sadeghi M.,Institute for Advanced Studies in Basic Sciences | Reihani S.N.S.,Sharif University of Technology
Journal of the Optical Society of America B: Optical Physics | Year: 2015

Optical tweezers have proven to be indispensable micromanipulation tools especially in aqueous solutions. Because of the significantly larger spherical aberration induced by the refractive index mismatch, trapping aerosols has always been cumbersome if not impossible. We introduce a simple but very efficient method for optimized aerosol trapping at a desired depth. We show that a wise selection of the immersion medium and the mechanical tube length not only enables trapping of objects that are known to be untrappable but also provides a way to tune the trappable depth range. © 2015 Optical Society of America.

Niroumand H.,Buein Zahra Technical University | Niroumand H.,University of Barcelona | Barcelo Alvarez J.A.,University of Barcelona | Saaly M.,Amirkabir University of Technology
Renewable and Sustainable Energy Reviews | Year: 2016

Earth has been a tried and tested natural construction material for thousands of years, and in combination with modern methods, it can be used for modern sustainable buildings. The reason for this increase is the interest in ecologically friendly constructions. Earth architecture is a type of vernacular architecture and sustainable architecture. To date, small number of studies have been carried out into investigation of earth architecture and earth buildings. The current survey is aimed at investigation of interest levels and involvement levels of ICOMOS members of USA, Iran, Malaysia, UK, Australia and India in development of earth architecture and earth buildings. Required data have been gathered by online questionnaires which were filled by ICOMOS members of six aforementioned countries. Based on various aspects of existing researches, literature review and discussion with few senior architects and researchers, the questionnaires were completed. A comparison has been made between responses of ICOMOS members of USA, Iran, Malaysia, UK, Australia and India. Results describe a gap between interest level and involvement level of respondents in earth architecture and earth buildings. © 2015 Elsevier Ltd. All rights reserved.

Seifbarghy M.,Islamic Azad University at Qazvin | Nouhi K.,Islamic Azad University at Qazvin | Mahmoudi A.,Buein Zahra Technical University
International Journal of Production Economics | Year: 2015

We consider a two-level supply chain consisting of a manufacturer and a retailer. The retailer gives a final product to a competitive market with customer sensitive to price. The customer demand is assumed to be constant depending on the price and quality degree of the final product. The manufacturer decides on the quality degree of the product. The optimal values of the major decision variables of the chain are determined for different conditions. The supply chain in centralized condition is considered and the optimal values of the price and the quality degree are found. Chain profit in decentralized condition is optimized and the optimal values of wholesale price and quality degree are determined. Retailers revenue sharing contract is designed and the optimal values of wholesale price and quality degree are found. Finally, a market segmentation condition in which customers are divided into two categories of quality oriented and price oriented is considered; then, the threshold of the percentage of potential quality oriented customers is determined. A set of numerical examples are designed in order to analyze the optimal values of the decision variables. © 2015 Elsevier B.V. All rights reserved.

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