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H. Mahmoudi Chenari,Ali Hassanzadeh,M.M. Golzan,H. Sedghi,M. Talebian 한국물리학회 2011 Current Applied Physics Vol.11 No.3
In this work, the electric and dielectric properties of nanocrystalline SnO_2 thick films were studied using ac impedance spectroscopy under different conditions through capacitanceefrequency measurements in frequency range from 1 Hz to 1 MHz and bias voltage range from 0 V to 2 V. Results showed that dielectric constant (ε´), dielectric loss (ε″), loss tangent (tan δ), ac electrical conductivity (σ) and the electric modulus (M) are strongly frequency dependent. A decrease in frequency accompanied with an increase in ε´ and ε″ values. Whereas, ac electrical conductivity (σ), real (M^Ⅰ) and imaginary parts of electric modulus (M^Ⅱ) values are increased with frequency increasing. A comparative study showed that our prepared thick films have greater dielectric value than that of the reported data; hence can be used them as ultrahigh dielectric materials.
H. Mahmoudi Chenari,M.M. Golzan,H. Sedghi,A. Hassanzadeh,M. Talebian 한국물리학회 2011 Current Applied Physics Vol.11 No.4
The dielectric properties of Cu/nano-SnO_2 thick film/Cu arrangement were studied by means of complex impedance spectroscopy and frequency dependence of capacitance measured from the impedance data at a range of frequency intervals between 1 Hz and 1 MHz with a voltage between 0 and 2 V. The frequency dependence of the dielectric constant ε´, dielectric loss ε″, loss tangent (tan δ), electric modulus M´ and M″ and AC electrical conductivity (σ_ac) of the sandwich arrangement was subsequently investigated. Experimental results revealed that the aforementioned parameters have strong frequency dependence. The obtained values of ε´, ε″ showed increments with decreasing frequency. However,increasing frequency levels cause an increase in the AC electrical conductivity (σ), real and imaginary part of electric modulus. In addition to this, in order to gain an insight into the electric nature of Cu/nano-SnO_2 thick film/Cu arrangement device, the Cole―Cole diagrams of the electric modulus were investigated at different voltages.
A NEW APPROACH TO SOLVING OPTIMAL INNER CONTROL OF LINEAR PARABOLIC PDES PROBLEM
M. Mahmoudi,A.V. Kamyad,S. Effati 한국전산응용수학회 2012 Journal of applied mathematics & informatics Vol.30 No.5
In this paper, we develop a numerical method to solving an optimal control problem, which is governed by a parabolic partial differen-tial equations(PDEs) . Our approach is to approximate the PDE problem to initial value problem(IVP) in R. Then, the homogeneous part of IVP is solved using semigroup theory. In the next step, the convergence of this approach is verified by properties of one-parameter semigroup theory. In the rest of paper, the original optimal control problem is solved by utilizing the solution of homogeneous part. Finally one numerical example is given.
Cauchy Completeness of κ-frames
M. M. Ebrahimi,M. Mahmoudi,M. Vojdani Tabatabaee 경북대학교 자연과학대학 수학과 2004 Kyungpook mathematical journal Vol.44 No.4
Considering general Cauchy filters for κ-frames, we prove some results about completeness, given by Banaschewski, for κ-frames. In particular, we show that a uniform-frame L is complete if and only if every general regular Cauchy filter of L is convergent.
A NEW APPROACH TO SOLVING OPTIMAL INNER CONTROL OF LINEAR PARABOLIC PDES PROBLEM
Mahmoudi, M.,Kamyad, A.V.,Effati, S. The Korean Society for Computational and Applied M 2012 Journal of applied mathematics & informatics Vol.30 No.5
In this paper, we develop a numerical method to solving an optimal control problem, which is governed by a parabolic partial differential equations(PDEs). Our approach is to approximate the PDE problem to initial value problem(IVP) in $\mathbb{R}$. Then, the homogeneous part of IVP is solved using semigroup theory. In the next step, the convergence of this approach is verified by properties of one-parameter semigroup theory. In the rest of paper, the original optimal control problem is solved by utilizing the solution of homogeneous part. Finally one numerical example is given.
M. Mansour Mohieddin Ghomshei,Amin Mahmoudi 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.12
Differential quadrature method (DQM) is implemented for analyzing the thermal buckling behavior of the symmetric cross-ply laminated rectangular thin plates subjected to uniform and/or non-uniform temperature fields. The approach includes two steps: (1) solving the problem of in-plane thermo-elasticity to obtain the in-plane force resultants and (2) solving the buckling problem under the force distribution obtained in the previous step. Solution procedures are numerically performed by discretizing the governing differential equations and boundary conditions using DQM method. Applying the developed DQ formulation, the buckling loads are obtained for several sample plates. The numerical results compared well with those available in the literature as well as those obtained by ABAQUS. Parametric studies are conducted to investigate the influence of some important parameters including the plate aspect ratio, cross-ply ratio,and stiffness ratio on the critical temperature and mode shape of buckling.
CO2/CH4 separation through a novel commercializable three-phase PEBA/PEG/NaX nanocomposite membrane
A. Mahmoudi,M. Asghari,V. Zargar 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.23 No.-
Three-phase polymer/liquid/solid (PEBA/PEG/nanozeolite X) mixed matrix membranes were synthe- sized. Effects of PEG and/or nanoparticle on CO2 and CH4 permeabilities and CO2/CH4 selectivity of the membranes were investigated. The synthesized membranes were characterized using AFM and SEM. CO2 Permeability and selectivity in the membranes increased with feed pressure and PEG loading. The PEBA membrane with loadings of 30% PEG and 10% nanozeolite showed the best performance; its CO2 permeability and CO2/CH4 selectivity at 8 bar were 95 Barrer and 45, respectively. Based on Robeson’s upper bound, both the three-phase membranes of this work would be proper for being commercialized.
Rabbab Bachir Bouiadjra,Abdelkader Mahmoudi,Mohamed Sekkal,Samir Benyoucef,Mahmoud M. Selim,Abdelouahed Tounsi,Muzamal Hussain 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.6
In this paper, an analytical solution for thermodynamic response of functionally graded (FG) sandwich plates resting on variable elastic foundation is performed by using a quasi 3D shear deformation plate theory. The displacement field used in the present study contains undetermined integral terms and involves only four unknown functions with including stretching effect. The FG sandwich plate is considered to be subject to a time harmonic sinusoidal temperature field across its thickness with any combined boundary conditions. Equations of motion are derived from Hamilton’s principle. The numerical results are compared with the existing results of quasi-3D shear deformation theories and an excellent agreement is observed. Several numerical examples for fundamental frequency, deflection, stress and variable elastic foundation parameter’s analysis of FG sandwich plates are presented and discussed considering different material gradients, layer thickness ratios, thickness-to-length ratios and boundary conditions. The results of the present study reveal that the nature of the elastic foundation, the boundary conditions and the thermodynamic loading affect the response of the FG plate especially in the case of a thick plate.
Saki, A.A.,Mahmoudi, H.,Tabatabaei, M.M.,Ahmadi, A. Asian Australasian Association of Animal Productio 2008 Animal Bioscience Vol.21 No.11
Experiments were conducted to evaluate the nutritional value of yellow-seeded rapeseed meal (YRSM). In the first experiment nutrient retention was recorded by 48 Arbor Acres-broiler chickens (28-d old) to determine AMEn (nitrogen-corrected apparent metabolizable energy), coefficient of apparent protein digestibility based on ileal digesta nitrogen, excreta nitrogen and uric acid nitrogen. The second experiment was carried out with 304 Arbor Acres-broiler chickens to compare effects of SBM (soybean meal) and YRSM on performance, carcass and digestive tract status. In the control treatment, SBM was replaced by graded levels of YRSM at 15, 22.5 and 30% of diet. Digestibility of YRSM protein was significantly lower (p<0.001) than SBM protein. The protein digestibility based on ileal measurement was significantly higher (p<0.001) than protein digestibility from excreta samples. There was no significant difference (p>0.001) between ileal and excreta digestibility of protein based on uric acid. AMEn as a fraction of gross energy was 0.54 in SBM and 0.45 in YRSM. With the exception of 30% YRSM, other YRSM treatments resulted in major effects on length and weight of the gastrointestinal tract. The results of this study have shown no adverse effect on performance as well as protein digestibility and energy value in response to replacement of SBM by YRSM with the exception of 22.5 and 30% YRSM.
Energy and exergy evaluation of a tri-generation system driven by the geothermal energy
Ehsan Akrami,Ata Chitsaz,Pooria Ghamari,S. M. S. Mahmoudi 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.1
In this paper, a geothermal-based tri-generation energy system with three useful outputs is clearly developed to produce electricity, heating and hydrogen. To have a better view of the thermodynamic performance of the present integrated system, parametric studies upon the effects of geofluid mass flow rate, turbine inlet temperature and pressure on the energy and exergy efficiencies of the system are undertaken. Under the specified circumstances, the related efficiencies of energy and exergy for the overall system are estimated around 26.14 % and 44.45 %, respectively, while these efficiencies for this system with electricity and heating generation, amount to 25.32 % and 39.75 %, and these amounts for solely electricity generation are 6 % and 33.47 %, respectively. Also the amount of net electricity power and heating generation in specific design parameter values are estimated around 43.47 (kW) and 149.8 (kW), respectively. In addition, for every 10.4 kW of electrical energy consumption in the electrolysis unit, pure hydrogen will be produced at a rate of 0.2 kg/hour.