Kafashi S.,University of Mazandaran
International Journal of Advanced Manufacturing Technology | Year: 2011
Process planning is an essential component for linking design and manufacturing process. Setup planning and operation sequencing are two most important functions in the implementation of CAD/CAPP/CAM integration. Many researches solved these two problems separately. Considering the fact that the two functions are complementary, it is necessary to integrate them more tightly so that performance of a manufacturing system can be improved economically and competitively. This paper presents a generative system and genetic algorithm (GA) approach to process plan the given part. The proposed approach and optimization methodology analysis constraints such as TAD∈(tool approach direction), tolerance relation between features and feature precedence relations to generate all possible setups and operations using workshop resource database. Tolerance relation analysis has a significant impact in setup planning for obtaining the part accuracy. Based on technological constraints, the GA algorithm approach, which adopts the feature-based representation, simultaneously optimizes the setup plan and sequence of operations using cost indices. Case studies show that the developed system can generate satisfactory results in optimizing the integrated setup planning and operation sequencing in feasible condition. © 2011 Springer-Verlag London Limited.
Kiani K.,University of Mazandaran
Journal of Physics and Chemistry of Solids | Year: 2014
The vibration and instability of a single-walled carbon nanotube (SWCNT) under a general magnetic field are of particular interest to researchers. Using nonlocal Rayleigh beam theory and Maxwell's equations, the dimensionless governing equations pertinent to the free vibration of a SWCNT due to a general magnetic field were derived. The effects of the longitudinal and transverse magnetic fields on the longitudinal and flexural frequencies as well as their corresponding phase velocities were addressed and are discussed below. The critical transverse magnetic field (CTMF) associated with the lateral buckling of the SWCNT was obtained. The obtained results reveal that the CTMF increases with the longitudinally induced magnetic field. Further, its value decreases as the effect of the small-scale parameter increases. © 2013 Elsevier Ltd. All rights reserved.
Azizi T.,University of Mazandaran
International Journal of Theoretical Physics | Year: 2013
We study wormhole solutions in the framework of f(R,T) gravity where R is the scalar curvature, and T is the trace of the stress-energy tensor of the matter. We have obtained the shape function of the wormhole by specifying an equation of state for the matter field and imposing the flaring out condition at the throat. We show that in this modified gravity scenario, the matter threading the wormhole may satisfy the energy conditions, so it is the effective stress-energy that is responsible for violation of the null energy condition. © 2013 Springer Science+Business Media New York.
Ashkarran A.A.,University of Mazandaran
Materials Science in Semiconductor Processing | Year: 2014
Mn-doped ZnS nanoparticles (NPs) were prepared with dopants at various concentrations using a facile, simple and inexpensive wet chemical method at room temperature. The physicochemical properties of NPs were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible absorption spectroscopy (UV-vis) and photoluminescence (PL). XRD analysis confirmed formation of ZnS with zinc blende structure and average crystallite size of about 2 nm. TEM analysis revealed formation of hyperfine NPs with rather good uniformity. The room temperature photoluminescence (PL) spectrum of ZnS:Mn2+ exhibited an orange-red emission around 600 nm. The maximum PL intensity was observed for 7.5% Mn doped ZnS. The photocatalytic performance of ZnS:Mn2+ was successfully demonstrated for degradation of three different model dyes (i.e. Rhodimine B (Rh. B), Bromocresol Green (BCG) and Bromochlorophenol Blue (BCB)). The results revealed that not only was there a remarkable difference in photocatalytic performance of Mn doped ZnS for all three different dyes at different dopant concentrations but also photocatalytic activity was decreased by Mn doping. © 2013 Elsevier Ltd.
Hatami M.,Islamic Azad University at Esfarayen |
Hatami M.,University of Mazandaran |
Ganji D.D.,University of Mazandaran
Energy Conversion and Management | Year: 2014
In this study, heat transfer of a fin shaped microchannel heat sink (MCHS) cooled by Cu-water nanofluid is investigated and temperature distribution in solid section (fin) and fluid section (Cu-water) are obtained by porous media approach and least square method and the results are compared with numerical procedure. The effective thermal conductivity and viscosity of nanofluid are calculated by the Parsher and Brinkman models respectively and MCHS is considered as a porous medium proposed by Kim and Kim. Modified Darcy equation is applied to the fluid and porous medium for heat transfer between fluid and solid sections. In addition, to deal with nanofluid heat transfer, a model based on Brownian-motion of nanoparticles is used. The effects of the nanoparticles volume fraction, porosity, Darcy number, microchannel dimensions, etc. on temperature distribution, velocity and Nusselt number are considered. As an outcome, by increasing the nanoparticles volume fraction, Brownian motion of the particles which carries heat and distributes it to the surroundings increases, and consequently difference between coolant and wall temperature will become less. Also, the optimum point for MCHS design is calculated by minimizing the friction factor which obtained channel aspect ratio (αs) is 2.45. © 2013 Elsevier Ltd. All rights reserved.