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A comparison between hydrothermally prepared Co3O4 via H2O2 assisted and calcination methods
S. E. Hashemi Amiri,M. R. Vaezi,A. Esmaielzadeh Kandjani 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.3
In this paper Co3O4 nanoparticles were synthesized via two different synthesis procedures. In the first method, hydrothermally synthesized β-Co(OH)2 particles were calcined at different temperatures. In the other method, H2O2 was used to eliminate the production of cobalt hydroxide. The amount of H2O2 was the main variable investigated in this study. All samples synthesized via these methods, were investigated for their structure, morphology, specific surface area and magnetization. The results showed that an increase in the temperature of the post heat treatment substantially increased particle sizes and consequently decreased the specific surface area of nanoparticles which influences magnetization. In the H2O2 assisted route, the minimum amount of the oxidant necessary for the complete elimination of the β-Co(OH)2 phase and production of the pure Co3O4 phase was determined to be 0.25 volume fraction. In the H2O2 assisted method, due to elimination of the post heat treatment, the nanoparticles become smaller with a higher specific surface area in comparison with the calcination method. However, the magnetic properties of the nanoparticles in the H2O2 assisted method are influenced by changing the amount of H2O2.
E. Mahmoudpour,SH. Hosseini-Hashemi,S. A. Faghidian 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.1
In the present research, an attempt is made to obtain a semi analytical solution for both nonlinear natural frequency and forced vibration of embedded functionally graded double layered nanoplates with all edges simply supported based on nonlocal strain gradient elasticity theory. The interaction of van der Waals forces between adjacent layers is included. For modeling surrounding elastic medium, the nonlinear Winkler-Pasternak foundation model is employed. The governing partial differential equations have been derived based on the Mindlin plate theory utilizing the von Karman strain-displacement relations. Subsequently, using the Galerkin method, the governing equations sets are reduced to nonlinear ordinary differential equations. The semi analytical solution of the nonlinear natural frequencies using the homotopy analysis method and the exact solution of the nonlinear forced vibration through the Harmonic Balance method are then established. The results show that the length scale parameters give nonlinearity of the hardening type in frequency response curve and the increase in material length scale parameter causes to increase in maximum response amplitude, whereas the increase in nonlocal parameter causes to decrease in maximum response amplitude. Increasing the material length scale parameter increases the width of unstable region in the frequency response curve.
Mahmoudpour, E.,Hosseini-Hashemi, SH.,Faghidian, S.A. Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.1
In the present research, an attempt is made to obtain a semi analytical solution for both nonlinear natural frequency and forced vibration of embedded functionally graded double layered nanoplates with all edges simply supported based on nonlocal strain gradient elasticity theory. The interaction of van der Waals forces between adjacent layers is included. For modeling surrounding elastic medium, the nonlinear Winkler-Pasternak foundation model is employed. The governing partial differential equations have been derived based on the Mindlin plate theory utilizing the von Karman strain-displacement relations. Subsequently, using the Galerkin method, the governing equations sets are reduced to nonlinear ordinary differential equations. The semi analytical solution of the nonlinear natural frequencies using the homotopy analysis method and the exact solution of the nonlinear forced vibration through the Harmonic Balance method are then established. The results show that the length scale parameters give nonlinearity of the hardening type in frequency response curve and the increase in material length scale parameter causes to increase in maximum response amplitude, whereas the increase in nonlocal parameter causes to decrease in maximum response amplitude. Increasing the material length scale parameter increases the width of unstable region in the frequency response curve.
ON (??; ±)-SKEW ARMENDARIZ RINGS
A. Moussavi,E. Hashemi 대한수학회 2005 대한수학회지 Vol.42 No.2
For a ring endomorphism ?? and an ??-derivation ±, we introduce (??; ±)-skew Armendariz rings which are a generalization of??-rigid rings and Armendariz rings, and investigate their properties. A semiprime left Goldie ring is ??-weak Armendariz if and only if it is ??-rigid. Moreover, we study on the relationship between the Baerness and p.p. property of a ring R and these of the skew polynomial ring R[x; ??; ±] in case R is (??; ±)-skew Armendariz. As a consequence we obtain a generalization of [11], [14] and [16].
ON (α, δ)-SKEW ARMENDARIZ RINGS
MOUSSAVI A.,HASHEMI E. Korean Mathematical Society 2005 대한수학회지 Vol.42 No.2
For a ring endomorphism $\alpha$ and an $\alpha$-derivation $\delta$, we introduce ($\alpha$, $\delta$)-skew Armendariz rings which are a generalization of $\alpha$-rigid rings and Armendariz rings, and investigate their properties. A semi prime left Goldie ring is $\alpha$-weak Armendariz if and only if it is $\alpha$-rigid. Moreover, we study on the relationship between the Baerness and p.p. property of a ring R and these of the skew polynomial ring R[x; $\alpha$, $\delta$] in case R is ($\alpha$, $\delta$)-skew Armendariz. As a consequence we obtain a generalization of [11], [14] and [16].
Porosity changes during packed bed solid-state fermentation
A. Karimi,S.A. Shojaosadati,P. Hejazi,E. Vasheghani-Farahani,M. Hashemi 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.6
Porosity is one of the key parameters in a typical solid-state fermentationmodel that represents the intraand inter-particle void spaces in bioreactor bed. In this research, the particle density and moisturecontent of the bed were used to determine the porosity changes of the solid substrate bed during thefermentation of Aspergillus niger in a laboratory scale packed-bed bioreactor. Biomass growth was alsomonitored by means of measuring CO2 and O2 in the bioreactors outlet gas online. As such, anexperimental relationship between humidity and porosity has been developed and can be used in solidstatefermentation modeling.
Effect of a Magnetic Field on Mixed Convection of a Nanofluid in a Square Cavity
G. A. Sheikhzadeh,S. Mazrouei Sebdani,M. Mahmoodi,Elham Safaeizadeh,S. E. Hashemi 한국자기학회 2013 Journal of Magnetics Vol.18 No.3
The problem of mixed convection in a differentially heated lid-driven square cavity filled with Cu-water nanofluid under effect of a magnetic field is investigated numerically. The left and right walls of the cavity are kept at temperatures of Th and Tc respectively while the horizontal walls are adiabatic. The top wall of the cavity moves in own plane from left to right. The effects of some pertinent parameters such as Richardson number (ranging from 0.1 to 10), the volume fraction of the nanoparticles (ranging 0 to 0.1) and the Hartmann number (ranging from 0 to 60) on the fluid flow and temperature fields and the rate of heat transfer in the cavity are investigated. It must be noted that in all calculations the Prandtl number of water as the pure fluid is kept at 6.8, while the Grashof number is considered fixed at 104. The obtained results show that the rate of heat transfer increases with an increase of the Reynolds number, while but it decreases with increase in the Hartmann number. Moreover it is found that based the Richardson and Hartmann numbers by increase in volume fraction of the nanoparticles the rate of heat transfer can be enhanced or deteriorated compared to the based fluid.