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S. Amari,F. Dahmane,S. Bin Omran,B. Doumi,I. E. Yahiaoui,A. Tadjer,R. Khenata 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.9
In this study, the structural, magnetic and electronic properties of the Co2FeGe1−xSix (x = 0, 0.5, 1) Heusler compounds have been calculated using the full-potential linearized augmented plane-wave method based on the spin density functional theory within the generalized gradient approximation of Perdew-Burke-Ernzerhof. In order to take into account the correlation effects, we have also performed GGA + U calculations, where the Hubbard on-site Coulomb interaction correction U is calculated by using the constraint local density approximation for the Co and the Mn atoms. The Cu2MnAl-type structure is found to be energetically more favorable than the Hg2CuTitype structure for both the Co2FeSi and the Co2FeGe compounds. The calculated atomic resolved densities of states of Co2FeSi and Co2FeGe indicate nearly half-metallic behaviors with small spindown electronic densities of states at the Fermi level. This behavior is corrected by including the Hubbard Coulomb energy U term. The Coulomb exchange correlation U confirms the halfmetallic property in both the Co2FeSi and the Co2FeGe compounds. We also discuss the electronic structures, the total and the partial densities of states, and the local magnetic moments. The Co2FeGe0.5Si0.5 compound shows a nearly half-metallic behavior with a small spin-down electronic density of states at the Fermi level in both the GGA and GGA+U approximations.
Mahya Samari,Sirus Zinadini,Ali Akbar Zinatizadeh,Mohammad Jafarzadeh,Foad Gholami 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.11
Surface-modified metal-organic frameworks (MOFs) were used for the fabrication of polyethersulfone (PES)- based polymeric composite membranes by phase inversion method. Initially, zirconium-based MOF, UiO-66-NH2, was modified with melamine (denoted as UiO-66-NH-Mlm) and ethylenediamine (UiO-66-NH-EtNH2) via a solvothermal post-modification technique. The fabricated polymeric membranes were then employed for oil-water separation and showed satisfactory hydrophilicity and antifouling performance (PWF: 55.38 kg/m2·h, FRR: 90.67 %, Rr: 46.94%, Rir: 9.33% and >99% rejection to the oil). It was due to the formation of the hydration layer, arising from the available -NH2 groups (providing hydrogen-bonding) on the surface of the modified MOFs (WCA: 51.66o), and the lower surface roughness. Higher hydrophilicity and better antifouling efficiency were obtained for the membranes using UiO-66- NH-Mlm, compared to UiO-66-NH-EtNH2, due to the higher number of -NH2 groups. The membranes also exhibited good thermal stability owing to the fine dispersion of the modified MOFs in the polymeric texture and the presence of metallic cores in the MOFs. The membranes were also applied for frequent filtrations with great performance.
Design of Absorption Refrigeration System Using Solar Energy Resource
Ahmed Al-Samari,Yasseen A. J. Almahdawi,Laith Abd hasnawi Al-Rubaye 대한설비공학회 2020 International Journal Of Air-Conditioning and Refr Vol.28 No.3
This study aims to design an absorption refrigeration system and estimate the heat energy demand. Moreover, this paper investigates the opportunity of using alteration of energy resources such as solar energy. The trough parabolic solar collectors TPC system is suggested and analyzed as a heat energy resource. Actual data of TPC are presented in this work to evaluate the size needed to guarantee enough heat sources that is running the refrigeration system. The outcome of this calculation proved that each 1 T.R needs about 11.1 kW of heat energy. The COP of the refrigeration system is found to be about 0.313. Moreover, the TPC generates about 100 W/m2. However, the optimum TPC may generate about 380 W/m2 in Iraqi climate. This value of heat generated represents the maximum energy at clear sky. The calculations are validated based on experimental and proven data.
Ashofteh, Roya Sadat,Samari, Farhad The Korean Society for Railway 2014 International Journal of Railway Vol.7 No.3
In this paper, the reduction effect of dry (solid) lubrication on wheel flange wear rates is studied. The solid / dry lubricator systems were attached to the most front and furthest back axles of a coach in order to examine the wear behavior of the equipped wheels. An attempt is also made to make a comparison between wear behaviors of these wheel flanges having dry lubrication devices with non-lubricated wheels in other railcars. Finally, a comparison is made between life-cycle of wheels under investigation and other similar wheel types.