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Saeid Kheradmand,Mojtaba Esmailian,A. Fatahy 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.4
Finishing of a workpiece is a main process in the production. This affects the quality and lifetime. Finishing in order of nanometer, nowadays, is a main demand of the industries. Thus, some new finishing process, such as abrasive flow finishing, is introduced to respond this demand. This may be aided by rotating workpiece and imposing a magnetic field. Numerical simulation of this process can be beneficial to reduce the expense and predict the result in a minimum time. Accordingly, in this study, magnetorheological fluid finishing is numerically simulated. The working medium contains magnetic and abrasive particles, blended in a base fluid. Some hydrodynamic parameters and surface roughness variations are studied. It is found that combination of rotating a workpiece and imposing a magnetic field can improve the surface roughness up to 15 percent.
Shrinkage performance of fly ash alkali-activated cement based binder mortars
M. Kheradmand,Z. Abdollahnejad,F. Pacheco-Torgal 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.5
Some authors reported that Alkali-activated Cement Based Binder (AACB) mortars can have much higher drying shrinkage thanPortland cement based composites. Its worth remember that shrinkage performance is a very important property for reinforcedconcrete composites just because a high shrinkage performance is associated to cracking tendency that leads to future durabilityproblems. Usually shrinkage is assessed under unrestrained conditions. However, the use of a restrained ellipse ring test is especiallyinteresting for materials that will be used in restrained conditions like repair mortars. This paper provides results on restrained andunrestrained shrinkage performance of fly ash AACB mortars. The restrained shrinkage was assessed with an elliptical ring thatprovides a faster and more reliable assessment of the cracking potential than circular rings. The results show that the mixtures withlower sodium silicate content are associated to a lower unrestrained shrinkage. Mixtures with lower sodium silicate content showedreduced average crack width under restrained conditions. The results also show that the reduction of sodium silicate content delaysthe appearance of cracks and is also associated to lower crack width. The use of AACB mortars in restrained conditions requires theuse of a reduced sodium silicate content or else the use of fibres to prevent crack appearance.
Optical Pattern Switching in Semiconductor Microresonators as All-Optical Switch
Reza Kheradmand,Babak Dastmalchi 한국전자통신연구원 2009 ETRI Journal Vol.31 No.5
In this paper, we present a spatial perturbation method to control the optical patterns in semiconductor microresonators in the far-field configuration. We propose a fast all-optical switch which operates at a low light level. The switching beam controls the behavior of output beams with strong intensities. The method has been applied successfully to different optical patterns such as rolls, squares, and hexagons.
Commutative single power cyclic hypergroups of order 4 and period 2
M.R. KHERADMAND,B. Davvaz 강원경기수학회 2020 한국수학논문집 Vol.28 No.3
In this paper we enumerate all commutative single power cyclic hypergroups of order 4 and period 2. Moreover, we prove some interesting properties regarding cyclic hypergroups.
On Cyclic Polygroups of Order less than Six and Period Two
M.R. KHERADMAND,B.Davvaz 한국수학교육학회 2019 純粹 및 應用數學 Vol.26 No.4
Cyclic hypergroups are of great importance due to their applications to many field in mathematics. In this paper, we classify all polygroups of order less than six where each of its non-identity elements is a generator.
Shabgard, Hojjat,Kheradmand, Saeid,Farzaneh, Hamed,Bae, Choongsik Elsevier 2017 Applied thermal engineering Vol.110 No.-
<P><B>Abstract</B></P> <P>A numerical model is developed to predict the performance of an exhaust gas recirculation (EGR) cooler using nanofluid as the coolant. The model accounts for turbulent flow of coolant and hot smokes on an integrated computational domain. Thermal and hydrodynamic behavior of four nanofluids comprising water as the base fluid and <SUB> SiO 2 </SUB> , <SUB> TiO 2 </SUB> , <SUB> Al 2 </SUB> <SUB> O 3 </SUB> and Cu nanoparticles, were compared over a wide range of Reynolds numbers and various particle concentrations. The accuracy of predictions was verified by experimental data available in the literature. The <SUB> Al 2 </SUB> <SUB> O 3 </SUB> - water nanofluid was found to provide the greatest heat transfer enhancement. Quantitatively, <SUB> Al 2 </SUB> <SUB> O 3 </SUB> - water nanofluid with a volume fraction of 5% and Reynolds number of 5000 improves the heat transfer coefficient by about 16% compared to pure water. However, it was found that the heat transfer enhancement was achieved at the expense of increased pressure drop due to greater viscosity of nanofluids compared to the base fluid. It was also found that the effectiveness of nanofluids in improving the heat transfer rate decreases as the Reynolds number increase.</P>
Mokhtari, K.,Kheradmand Saadi, M.,Ahmadpanahi, H.,Jahanfarnia, Gh. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.9
The concrete is considered as an important radiation shielding material employed widely in nuclear reactors, particle accelerators, laboratory hot cells and other different radiation sources. The present research is dedicated to the shielding properties study of the ordinary concrete reinforced with different weight fractions of lead oxide micro/nano particles. Lead oxide particles were fabricated by chemical synthesis method and their properties including the average size, morphological structure, functional groups and thermal properties were characterized by XRD, FESEM-EDS, FTIR and TGA analysis. The gamma ray mass attenuation coefficient of concrete composites has been calculated and measured by means of the Monte Carlo simulation and experimental methods. The simulation process was based on the use of MCNP Monte Carlo code where the mass attenuation coefficient (μ/ρ) has been calculated as a function of different particle sizes and filler weight fractions. The simulation results showed that the employment of the lead oxide filler particles enhances the mass attenuation coefficient of the ordinary concrete, drastically. On the other hand, there are approximately no differences between micro and nano sized particles. The mass attenuation coefficient was increased by increasing the weight fraction of nanoparticles. However, a semi-saturation effect was observed at concentrations more than 10 wt%. The experimental process was based on the fabrication of concrete slabs filled by different weight fractions of nano lead oxide particles. The mass attenuation coefficients of these slabs were determined at different gamma ray energies using <sup>22</sup>Na, <sup>137</sup>Cs and <sup>60</sup>Co sources and NaI (Tl) scintillation detector. The experimental results showed that the HVL parameter of the ordinary concrete reinforced with 5 wt% of nano PbO particles was reduced by 64% at 511 keV and 48% at 1332 keV. Reasonable agreement was obtained between simulation and experimental results and showed that the employment of nano PbO particles is more efficient at low gamma energies up to 1Mev. The proposed concrete is less toxic and could be prepared in block form instead of toxic lead blocks.
Shabgard, Hojjat,Kheradmand, Saeid,Bae, Choongsik Professional Engineering Publishing Ltd 2014 Proceedings of the Institution of Mechanical Engin Vol. No.
<P>A three-dimensional numerical model was developed to investigate the pilot injection process in homogeneous charge compression ignition engines using the Open-FOAM computational fluid dynamics package. In particular, the percentage of trapped fuel in the crevice before the main injection was studied. The model was validated by comparing the numerically determined in-cylinder pressures with experimental data available in the literature. The amount of trapped fuel in the crevice was determined for three pilot injections at crank angles of 180°, 120° and 80° before top dead centre and for various pilot injection percentages with different swirl ratios. The results showed that the percentage and the timing of a pilot injection directly and proportionally affect the contributions due to the fuel trapped in the crevice. It was also found that the swirl ratio is an important parameter in accumulation of the fuel in the crevice.</P>
Mohammad Nazemi Babadi,Saeid Kheradmand,배충식 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.1
In this paper, the numerical simulation of the diesel and gasoline fuels injection in a constant volume chamber and in a cylinder under the operating conditions of a compression ignition (CI) engine is conducted. The simulation results are compared with the experimental data which derived from fast imaging techniques. In order to check out the possibility of using gasoline instead of diesel to increase the volumetric efficiency of the CI engine, the spray characteristics of the gasoline and diesel with injection pressures of 40 and 80 MPa, as well as temperatures of 243, 273 and 313 K, under cold start condition is investigated. The results show that under the same conditions, the vapor penetration length for the two fuels is approximately equal and due to the lower volatility of the diesel fuel, its liquid penetration length in 40 and 80 MPa injection pressures was found to be 7 and 9 mm higher than gasoline, respectively. In addition, the reduction in fuel temperature from 313 K to 243 K leads an increase in the penetration of gasoline and diesel liquids by 12 and 10 mm, respectively. Finally, the decrease in the evaporation rate causes a non-homogeneous mixture and results an increase in the unburned hydrocarbons and emissions.