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Showing 3 results for Izadkhah


Volume 16, Issue 7 (9-2016)
Abstract

Nanofluids are engineered by suspending nanoparticles with average sizes below 100 nm in traditional. The ever increasing of thermal loads in such applications requires advanced operational fluid characteristics, for example, high thermal conductivity dielectric oils in transformers and car radiators. These fluids require high thermal conduction, as long as electrical insulation. In the present work the thermophysical and rheological properties of the nanofluids such as thermal conductivity, viscosity and density are obtained from molecular dynamics simulations. These results served as initial data for computational fluid dynamics simulations to calculate heat transfer coefficient. The results show that, adding titanium oxide nanosheet in the base fluid enhanced the thermal conductivity and increased the viscosity and density of the base fluid. The theoretical calculations are confirmed the molecular dynamics simulation results and the simulation methods accuracy. The computational fluid dynamics results show that increasing the amount of titanium oxide nanosheet in the base fluid increases the heat transfer coefficient and increasing ethylene glycol ratio in base fluid leads to lower heat transfer coefficient. Also non-equilibirium molecular dynamics method can use as a effective and accurate method for nanofluids investigation. The coding which used to obtaine the thermal conductivity of nanofluid is a novel and modified type of non-equlibiruim molecular dynamics method. With using this coding the eror persentages of simulations is decreases. The other advantage of this code is reducing the simulation process, becous the molecular dynamics simulations need a long time for processing.

Volume 16, Issue 8 (10-2016)
Abstract

The aim of present work is the investigation of polypropylene/graphene oxide nanocamposies. In this work, the reinforcing effects of the graphene oxide nanoparticles on the mechanical and thermal properties of the nonpolar polypropylene are examined. There is two main challenges to improve the properties of polypropylene by graphene oxide nanoparticles. First, the nanoparticles have not suitable dispersion in polymer matrix. Furthermore, there is not sufficient adhesion between nanoparticle and polymer chains. In this study, the graphene oxide (GO) surface is modified by a linear alkyl chain via a bimolecular nucleophilic substitution reaction between the oxygen groups of GO and reactants to promote the homogeneous dispersion of GO in the organic solvent and increasing the interfacial adhesion between the graphene oxide and polymer matrix. The presence of the alkyl groups on the surface of graphene oxide nanoparticles is characterized by FT-IR. To prevent the AGO aggregation in the polypropylene, the solution-blending method is used to prepare the nanocomposites with 0.1, 0.3, 0.5 wt% AGO. The SEM images confirmed the appropriate dispersion of the graphene oxide in the composites. The stress-strain analysis, dynamic-mechanical thermal analysis (DMTA), and thermal gravimetric analysis (TGA) are performed to investigate the mechanical and thermal properties of nanocomposites. The results demonstrated that the Young’s modulus of the polymer are improved by 20, 30 and 34% with adding 0.1, 0.3 and 0.5% AGO, respectively. Also the 10% mass loss temperature for 0.1, 0.3 and 0.5% AGO nanocomposites compared to neat polypropylene increased by 2, 8, 12 C0, respectively.

Volume 19, Issue 3 (9-2015)
Abstract

In today’s competitive business environment, using holding company has been common in the developed countries, and recently, it has also gained momentum in Iran. These companies create special value through synergy. Todays, multi-business organization management has been more important than ever, and the fact that the number of such holding companies has been increased has also intensified this. This research presents a strategic model for performing the first level of strategic performance through balanced scorecard. It can help parent companies as a dashboard in order to observe subset companies. In this research, after studying the related literature, based on the nature of the subject under study, interview with the managers of these holding companies and their subsets was the best research methodology. After identifying the dimensions, the questionnaire developed by the researchers and quantitative research methods were used for drawing the hierarchy dimensions. Eventually, a model with 11 dimensions at 4 levels was extracted.

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