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    The formation and dissociation energy of vacancies in cementite: A first-principles study

    , Article Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms ; Volume 502 , 2021 , Pages 157-163 ; 0168583X (ISSN) Mehrdad Zamzamian, S ; Amirhossein Feghhi, S ; Samadfam, M ; Sharif University of Technology
    Elsevier B.V  2021
    Because of the possibility of various types of vacancies in cementite due to its crystalline structure, the focus of this paper was only on vacancies. In this regard, the formation energies of single, two, three and four vacancies of over than 120 different cases were calculated using first-principles method. For the case of single vacancy, the results were in three values of ~1.63, 1.39 and 0.78 eV according to iron vacancies at general positions, iron vacancies located on mirror planes and carbon vacancies in the interstitial positions, respectively. The results for the case of two, three and four vacancies were between from 2.10 to 3.34 eV, from 3.92 to 5.10 eV and from 4.77 to 6.33 eV,... 

    Optimization of the marinelli beaker dimensions using genetic algorithm

    , Article Journal of Environmental Radioactivity ; Volume 172 , 2017 , Pages 81-88 ; 0265931X (ISSN) Zamzamian, S. M ; Hosseini, S. A ; Samadfam, M ; Sharif University of Technology
    A computational code, based on the genetic algorithm and MCNPX version 2.6 code was developed and used to investigate the effects of some important parameters of HPGe detector (such as Al cap thickness, dead-layer thickness and Ge hole size) on optimum dimensions of marinelli beaker. In addition, the effects of detector material on optimal beaker dimensions were also investigated. Finally, the optimized beaker dimensions at various beaker volumes (300, 500, 700, 1000 and 1500 cm3) were determined for some conventional Ge detectors with different crystal sizes (16 sizes). These sets of data then were used to drive mathematical formulas (obtained by best fitting to data sets). The results... 

    Atomistic simulation of the effect of radiation-induced point defects on uniaxial tension behavior of single-crystal α-Fe containing low carbon in solution

    , Article European Physical Journal Plus ; Volume 137, Issue 3 , 2022 ; 21905444 (ISSN) Zamzamian, S. M ; Feghhi, S. A. H ; Samadfam, M ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2022
    Molecular dynamics simulations are employed to investigate the effects of Frenkel pairs resulted from displacement cascade in single-crystal α-Fe containing ~ 0.09 at.% C on the uniaxial tension behavior in α-Fe with and without the presence of a 12〈111〉{01¯1} edge dislocation. These point defects did not considerably change the elastic modulus. The drop in the ultimate tensile strength of perfect α-Fe is not very considerable, and it decreased by 2% in the case of the presence of the edge dislocation in α-Fe. The simulations showed there is a sudden phase transformation from BCC crystal structure to FCC and HCP with the beginning of the plastic deformation that the first one is predominant... 

    Determining of the optimized dimensions of the Marinelli beaker containing source with inhomogeneous emission rate by using genetic algorithm coupled with MCNP and determining distribution type by neural networks

    , Article Applied Radiation and Isotopes ; Volume 157 , 2020 Zamzamian, S. M ; Hosseini, S. A ; Feghhi, S. A ; Samadfam, M ; Sharif University of Technology
    Elsevier Ltd  2020
    In order to determine the activity of C137s in soil resulting from nuclear accidents or fallouts, the best choice is to use HPGe detectors due to their best energy resolutions. In this regard, in order to enhance the detection efficiency, the Marinelli beakers have been used to increase the radiation interaction with the sensitive volume of the detector. In previous works, to optimize the dimension of Marinelli beakers, the assumption was that the emission rate of the source is homogeneous in beaker volume. In the present study, to investigate the effect of the inhomogeneous emission rate of the source on the optimum dimensions of the beaker, in a simple case, the beaker was divided into two... 

    Atomistic investigation of the effects of symmetric tilt grain boundary structures on irradiation response of the α-Fe containing carbon in solution

    , Article Computational Materials Science ; Volume 166 , 2019 , Pages 82-95 ; 09270256 (ISSN) Zamzamian, S. M ; Feghhi, S. A ; Samadfam, M ; Darvishzadeh, M ; Sharif University of Technology
    Elsevier B.V  2019
    In this paper, molecular dynamics simulations were used to investigate the effect of the presence of carbon atoms, either in dispersed form or C-rich region, in low-carbon α-Fe containing symmetric tilt grain boundary (STGB)with a boundary plane rotated about the 110 misorientation axis on the number of SIAs and vacancies produced by PKA energies of 3, 5, 7 and 9 keV at 300 K. Results were compared with the SIAs and vacancies produced in pure α-Fe. It was also shown that the presence of GBs in this Fe-C alloy has no effect on the time at which point defects reach to their maximum values at the thermal spike stage. On the other hand, the GBs decrease the number of point defects in comparison... 

    Atomistic simulation of the effect of carbon content and carbon-rich region on irradiation response of α-Fe on picosecond timescale

    , Article Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms ; Volume 443 , 2019 , Pages 70-78 ; 0168583X (ISSN) Zamzamian, S. M ; Samadfam, M ; Feghhi, S. A ; Arjhangmehr, A ; Sharif University of Technology
    Elsevier B.V  2019
    α-Fe with low carbon content is a base material which is commonly used in manufacturing of Reactor Pressure Vessel (RPV) of commercial nuclear power plants. Carbon is generally diffused to α-Fe matrix to improve some of its mechanical properties. The presence of carbon may alter the irradiation response of the steel. In the current study, using molecular dynamics simulations, we have investigated the influence of carbon (∼in either dispersed form or carbon-rich region as chain) in the primary damage states of α-Fe low carbon steels. It is found that carbons in dispersed form have no significant effect on the self-interstitial atoms (SIAs) in α-Fe. While, carbon-rich (C-rich as... 

    Simultaneous alpha and gamma discrimination with a phoswich detector using a rise time method and an artificial neural network method

    , Article Applied Radiation and Isotopes ; Volume 154 , 2019 ; 09698043 (ISSN) Panahi, R ; Feghhi, S. A. H ; Moghadam, S. R ; Zamzamian, S. M ; Sharif University of Technology
    Elsevier Ltd  2019
    We used two digital methods—rise time discrimination (RTD) and an artificial neural network (ANN)—to simultaneously discriminate alpha particles and gamma rays detected by a phoswich detector (50 μm BC-400 coupled to 3 mm CsI(Tl)). The results for 10,000 pulses discriminated by the RTD method showed that the rise time distribution of the pulses is rather vast (between 200 and 800 ns for gamma rays and less than 40 ns for alpha particles). The same result was also observed in the dual-parameter diagram (pulse rise time versus area under the pulse) for an 241Am source. Then, as another approach, three pulse features—rise time, pulse height ratio, and charge ratio—were extracted from 2000... 

    Flight envelope expansion in landing phase using classic, intelligent and adaptive controllers [electronic resource]

    , Article Journal of aircraft ; 2006, Vol. 43, No. 1 Malaek .S. M. B ; Izadi, Hojjat Allah ; Pakme, Mehrdad
    An expanding flight envelope in the landing phase of a typical jet transport aircraft in presence of strong wind shears using a learning capable control system (LCCS) is investigated. The idea stems fromhuman beings functional architecture that gives them the ability to do more as they age and gain more experience. With the knowledge that classical controllers lack sufficient generality to cope with nonlinear as well as uncertain phenomenon such as turbulent air, the focuse is on different types of intelligent controllers due to their learning and nonlinear generalization capabilities as candidates for the landing flight phase. It is shown that the latter class of controllers could be used... 

    , M.Sc. Thesis Sharif University of Technology Zamzamian, Mehrdad (Author) ; Vosoughi, Nasser (Supervisor)
    High purity Germanium (HPGe) detector is a sub branch of semiconductor detectors which has very good resolution, very little dead time, able tobuild in large dimensions and suitable for any condition that it is using in vast fields from space investigation to radiation therapy. this detector is usually used to detecting gamma radiations furthermore the best resolution can be attained with decreasing leakage current. for analyzing about operation of the HPGe detector, it needs to initiate a model of this detector. in this studing has been used modelGEM-15190,POP-TOP which is built by ortec company. for initiating, it was used liquid nitrogen and accessory equipments like high voltage supply,... 

    Experimental investigation of forced convective heat transfer coefficient in nanofluids of Al2O3/EG and CuO/EG in a double pipe and plate heat exchangers under turbulent flow

    , Article Experimental Thermal and Fluid Science ; Volume 35, Issue 3 , April , 2011 , Pages 495-502 ; 08941777 (ISSN) Zamzamian, A ; Oskouie, S. N ; Doosthoseini, A ; Joneidi, A ; Pazouki, M ; Sharif University of Technology
    Nanofluid is the term applied to a suspension of solid, nanometer-sized particles in conventional fluids; the most prominent features of such fluids include enhanced heat characteristics, such as convective heat transfer coefficient, in comparison to the base fluid without considerable alterations in physical and chemical properties. In this study, nanofluids of aluminum oxide and copper oxide were prepared in ethylene glycol separately. The effect of forced convective heat transfer coefficient in turbulent flow was calculated using a double pipe and plate heat exchangers. Furthermore, we calculated the forced convective heat transfer coefficient of the nanofluids using theoretical... 

    A study on the mobility of [formula presented] edge dislocation in low-carbon α-Fe and its interactions with damage cascade: on picosecond time scale using molecular dynamics simulations

    , Article Journal of Nuclear Materials ; Volume 527 , 2019 ; 00223115 (ISSN) Zamzamian, M ; Feghhi, A. H ; Samadfam, M ; Sharif University of Technology
    Elsevier B.V  2019
    Molecular dynamics simulations were used to propose a closed-form expression for the mobility of the [Formula presented] edge dislocation in low-carbon α-Fe (up to 0.1 at.% C) at temperatures of 300, 400 and 500 K and applied shear stresses of 10–100 MPa. Considering this parameter helps us to understand the effect of damage cascade on the dislocation mobility. The results confirmed that the point defect clusters at the thermal spike stage of the cascade (that they can be considered as an unstable precipitation-like phase), the distance of damage cascade relative to the center of the dislocation core and forming carbon-vacancy (C–V) complexes are some rather stronger obstacles for movement... 

    Short Term and Long Term Analysis of Radiation Damage in Carbon Based Steels with Emphasis on Reactor Pressure Vessel

    , Ph.D. Dissertation Sharif University of Technology Zamzamian, Mehrdad (Author) ; Samadfam, Mohammad (Supervisor) ; Feghhi, Amir Hossein (Supervisor)
    Steels as structural materials of pressure vessels of nuclear reactors, in addition to high temperatures and pressures, are exposed to ionizing radiation such as neutrons. The primary effects of damage caused by exposing these solids to radiation are the displacement of atoms from their equilibrium positions and the formation of point defects and damage clusters caused by damage accumulation due to displacement cascades produced by transmitting the energy of the incident particle to an atom by interactions such as elastic and inelastic scatterings neutrons with the nucleus. These microstructural changes cause large structural defects such as swelling, cracking, cracking, creep, reducing... 

    Optimal Design of the Heliostat Field in the Solar Central Receiver Systems

    , M.Sc. Thesis Sharif University of Technology Piroozmand, Pasha (Author) ; Boroushaki, Mehrdad (Supervisor)
    In a solar central system plant about 40% of energy losses occurs in the heliostat field. Furtheremore, half of the investment costs for construction of the plant is related to the heliostat field. Therefore, an optimal design of the heliostat field is necessary for reduction of levelized cost of energy in solar tower power plants. In this study, in order to optimally design the heliostat field, first energy performance of the helistat field in one year is simulated. Solar power and sun’s position at each moment of the day is determined by mathematical relations. Then, loss factors in the field are modelled and heliostat field layout is designed by an algorithm. Finally, by using PSO... 

    Modeling and Optimal Design of a Solar Chimney Power Plant

    , M.Sc. Thesis Sharif University of Technology Gharagozlou, Ali (Author) ; Boroushaki, Mehrdad (Supervisor)
    The power generation system of this type of power plants operates on the air flowing through the power plant’s chimney and colliding with the turbine blades within the chimney. When the solar collector warms the nearby air and thus expands the air by absorbing the sunlight, a difference is created in the density. Then, this difference in the density creates the phenomenon of buoyancy, making the air pass to the top of the chimney through the collector.This study simulated and optimized a solar chimney power plant. The simulation and optimization were performed based on the information of Manzanares Solar Chimney Power Plant in Spain (located in 150 km from the south of Madrid). It was... 

    An efficient graphyne membrane for water desalination

    , Article Polymer ; Volume 175 , 2019 , Pages 310-319 ; 00323861 (ISSN) Mehrdad, M ; Moosavi, A ; Sharif University of Technology
    Elsevier Ltd  2019
    Desalination of sea saline water seems a successful solution to supply clean water. For desalination, novel nanoporous membranes have been proposed as a substitute for the classic reverse osmosis (RO) membranes. The one-atom-thick graphyne membrane has shown great potential in water desalination. By applying functional groups (FGs) into the pores of the monolayer graphyne membranes, the water permeability and the ion rejection were passively increased. The effects of applying various FGs such as Hydrogen, Fluorine, Carboxyl and Amine, effect of the salt concentration, the applied pressure, and the effective diameter of the graphyne pores were determined by molecular dynamics (MD)... 

    Intelligent Control of Hybrid Vehicles based on the Simultaneous Optimization of Fuel Consumption and Pollution Emission

    , M.Sc. Thesis Sharif University of Technology Mamouri, Ali (Author) ; Boroushaki, Mehrdad (Supervisor)
    The issue under discussion in this paper is to optimize the fuel consumption of the Toyota Prius hybrid car. In order to solve this problem, the ADVISOR design model used by NREL in the Matlab / Simulink environment has been used. Various parts of this model are described. The optimization performed on this issue is based on the emotional controller. This controller works by simulating learning in animals based on encouraging and punishing them. With the introduction of the controller, the model and its inclusion in the fuel consumption control and its implementation have achieved good results. In the initial state and the controller in the model, the fuel consumption was 4.9 liters per 100... 

    Simulation and Multi-Objective Optimization of a Solar Micro CCHP Using Intelligent Techniques

    , M.Sc. Thesis Sharif University of Technology Younesi, Ali (Author) ; Boroushaki, Mehrdad (Supervisor)
    Today, due to the scarcity of fossil energy resources, security of energy supply, and increasing environmental concerns, we need to develop new technologies to promote energy-saving and reduce greenhouse gas emissions. One of the suitable options for this purpose is to use the simultaneous production of electric power, cooling, and heating. Meanwhile, trigeneration systems that provide part of their energy needs from the sun, due to the free solar energy source and low environmental impact, can be an ideal technology for clean and safe scattered production. The present study has suggested a trigeneration system of cooling, heating, and power generation based on the organic Rankin cycle and... 

    Optimal Design of Induction MHD Generator for Electrical Power Generation from Exhaust of the Gas Turbine Power Plants

    , M.Sc. Thesis Sharif University of Technology Barzegar, Iran (Author) ; Boroushaki, Mehrdad (Supervisor)
    Today, due to increasing electricity consumption and demand, the use of conventional systems such as thermal, hydro and nuclear power plants is not enough to convert energy. Over the past century, scientists have sought to discover new technologies for exploiting different forms of energy and converting them into high-efficiency electrical energy. One of these ways is to use the phenomenon of magnetohydrodynamics (magnetic fluid dynamics) to convert thermal energy directly into electrical energy. Magnetohydrodynamics is a theoretical field that studies the dynamics of fluids with electrical conductivity. Induction magneto-hydrodynamic generators use ionized hot plasma (a quasi-neutral gas of... 

    The Impact of Human Capital on Labour Productivity in Manufacturing Sectors of Iran

    , M.Sc. Thesis Sharif University of Technology Narimani, Meysam (Author) ; Sepahvand, Mehrdad (Supervisor)
    This research has been surveyed the impact of intermediate skilled and high skilled human labor force on the productivity of manufacturing sectors by the Nelson & Phelps and also Lucas approaches. first model is related to the level of productivity and the second model is related to the growth of it. We has been prepared the needed statistics from the raw figures of iran statistics center. regression analysis has been done on the basis of panel data model by the use of stata software. the results show that not good efficiency to optimize technology factor of Cobb-Douglas model although it shows higher marginal labor productivity of high skilled human labor force. we has proposed some... 

    Design and Implementation of a Linear, 1 Watt, High Efficiency Power Amplifier with Controllable Output Power for UHF-RFID Application

    , M.Sc. Thesis Sharif University of Technology Sadeghi, Sanaz (Author) ; Sharifbakhtiar, Mehrdad (Supervisor)
    Design and implementation of an efficient, 1 Watt, linear power amplifier (PA) with CMOS technology for UHF-RFID applications is presented in this thesis. Poor quality factor of inductors, high substrate noise and low breakdown voltage of CMOS, makes the implementation of Watt-level PAs challenging on this technology. Also the trade-off between linearity and efficiency, further hardens achieving an efficient high power linear PA. So the literature was reviewed first to come up with the appropriate structure of a linearized efficient PA. Afterwards, the structure was reformed and optimized for the application mentioned above with reasonable stability margins. Baseband relevant blocks were...