Taheri Otaqsara S.M.,Islamic Azad University at Parsabad
Materials Science in Semiconductor Processing | Year: 2013
Cu2+-doped (0-2 at%) ZnS nanoparticles stabilized by 2-mercaptoethanol (2-ME) were successfully prepared using wet precipitation route in aqueous solution. The structural and optical characteristics were studied by various techniques. XRD pattern showed zinc blende cubic structure of Cu2+-doped ZnS with grain size of 4±0.5 nm. Spherical shape and well distribution of particles is confirmed by TEM, SEM and STM microscopy. Copper doping were identified by elemental dispersive (EDS) spectrometry. UV-vis spectroscopy revealed strong confinement effect due to blue shift in absorption shoulder peak as compared to bulk ZnS. Red luminescence band at∼657 nm on Cu2+ doping may be arising from recombination of electrons at sulfur vacancies (Vs) and Cu(t2) states formed at ZnS band gap. Optimum concentration of 0.25 at% (red band) of Cu2+ doping was selected by the observed enhanced PL emission. © 2013 Elsevier Ltd. All rights reserved.
Azizi H.,Islamic Azad University at Parsabad |
Jahed R.,Islamic Azad University
Computers and Industrial Engineering | Year: 2011
In a recent article, Wang et al. [Wang, N. S.; Yi, R. H.; & Wang, W. (2008). Evaluating the performances of decision-making units based on interval efficiencies. Journal of Computational and Applied Mathematics, 216, 328-343] proposed a pair of interval data envelopment analysis (DEA) models for measuring the overall performances of decision-making units (DMUs) with crisp data. In this paper, we demonstrate that interval DEA models face problems in determining the efficiency interval for each DMU when there are zero values for every input. To remedy this drawback, we propose a pair of improved interval DEA models which make it possible to perform a DEA analysis using the concepts of the best and the worst relative efficiencies. Two numerical examples will be examined using the improved interval DEA models. One of the examples is a real-world application about 42 educational departments in one of the branches of the Islamic Azad University in Iran that shows the advantages and applicability of the improved approach in real-life situations. © 2011 Elsevier Ltd. All rights reserved.
Azizi H.,Islamic Azad University at Parsabad
International Journal of Advanced Manufacturing Technology | Year: 2013
Smirlis et al. (Appl Math Comput 177(1):1-10, 2006) have proposed a pair of interval data envelopment analysis (DEA) models for computation of the efficiency of decision-making units (DMUs) in the presence of missing data. In this paper, we show that the interval DEA models presented by Smirlis et al. have some drawbacks due to the use of variable production frontier for computation of the efficiency intervals of DMUs. To overcome these drawbacks, this paper presents new interval DEA models based on interval arithmetic. It is shown that the proposed interval DEA models do not need extra variable changes and use a fixed, unified production frontier for computation of the efficiency intervals of the DMUs with interval input and output data. A numerical example is presented to illustrate the potential applications of the new interval DEA models and their effectiveness for measuring the interval efficiencies of the DMUs. © 2012 Springer-Verlag London Limited.
Azizi H.,Islamic Azad University at Parsabad
International Journal of Advanced Manufacturing Technology | Year: 2014
Farzipoor Saen proposed a method based on data envelopment analysis for supplier selection in the presence of weight restrictions and imprecise data (Int J Adv Manuf Technol 39 (11-12):1061-1070). The aim of this note is to show a computational deficiency in calculating the value of the preference intensity parameter in that paper. © 2013 Springer-Verlag London.
Nemati-Kande E.,Islamic Azad University at Parsabad |
Shekaari H.,University of Tabriz
Journal of Chemical Thermodynamics | Year: 2013
In this work, the (liquid + liquid) equilibrium of 1-propanol, 2-propanol, 2-methyl-2-propanol, 2-butanol, or (ethanol + sodium carbonate + water) ternary systems was studied. Binodal curves and tie-line data at T = 298.15 K were reported. The effect of temperature was studied using the obtained cloud-point data as a function of alcohol mole fraction at temperature range T = (293.15 to 328.15) K with 5 K intervals. The free energy, enthalpy, and entropy of clouding point (CP) estimated using a simple method, and the driving force of the two-phase formation process was discussed on the base of the estimated free energy values. Salting-out effect was discussed using the values of parameters of one parameter effective excluded volume (EEV) model. The effect of different alcohols on the phase-separation ability of the studied systems was discussed on the base of the intermolecular interactions. Also, a new three parameter nonlinear equation developed and successfully used for the correlation of the binodal curves, and the correlation coefficients were also reported. Moreover, the generalized electrolyte-NRTL model to the mixed solvent electrolyte systems (e-NRTL) was satisfactorily used for the correlation of the tie-line compositions, and the binary interaction parameters were also reported. © 2012 Elsevier Ltd. All rights reserved.