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hosseini--soheil
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Studying the Problem of Maximum Matching in Stochastic Environments
, M.Sc. Thesis Sharif University of Technology ; Ghodsi, Mohammad (Supervisor)
Abstract
The problem studied in this research is the online stochastic bipartite matching. In this problem the vertices of one side of the given graph arrive in an online manner, with respect to a probability distribution. Also the edges of the graph exist according to a given probability distribution and one should perform queries from an oracle to know about the existence of an edge. The given graph shall be weighted or unweighted. The goal here is to find a maximum matching in the graph that is as close to the omniscient optimum as possible, while the number of queries performed per vertex is limited. In the general case of the problem, there are no specific conditions, but in other versions,...
Modelling of Frictional Cracks by the Extended Finite Element Method Considering the Effect of Singularity
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Supervisor) ; Mohammadi, Soheil (Co-Advisor)
Abstract
When a crack is subjected to a compression field, it will close and its edges will get into contact with each other. Depending on the direction and magnitude of the loads and also the coefficient of friction, ‘stick’ or ‘slip’ situationsbetween the edges will occur. This type of crack is known as ‘frictional crack.’ In this project, first these cracks are studied analytically and the order of singularity is derived using asymptotic analysis and also the analytical fields are determined for both ‘isotropic’ and ‘orthotropic’ materials. Then, numerical simulations are carried out using extended finite element method which is considered as the most powerful means for analyzing the problems...
Theoretical and Numerical Analysis of Shock Waves Propagation in Porous Medium
, Ph.D. Dissertation Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor) ; Mohammadi, Soheil ($item.subfieldsMap.e)
Abstract
Particulate porous mateials have always been of interest in terms of reducing shock waves effects in different protective applications. Therefore, the physics governing the flow in porous media is especially significant for which different models have been presented by the researchers. The complexities of these media have caused many existing models to be unable to properly predict the behavior of granular media under shock loadings. On the other hand, the complexity of the equations makes the numerical solution of them cumbersome and costly in a way that many researchers do not solve the whole coupled equations and reduce their number. In addition, current high-resolution TVD solutions of...
Monte Carlo simulation of Feynman-α and Rossi-α techniques for calculation of kinetic parameters of Tehran research reactor
, Article Annals of Nuclear Energy ; Volume 38, Issue 10 , 2011 , Pages 2140-2145 ; 03064549 (ISSN) ; Vosoughi, N ; Hosseini, M ; Sharif University of Technology
2011
Abstract
Noise analysis techniques including Feynman-α (variance-to-mean) and Rossi-α (correlation) have been simulated by MCNP computer code to calculate the prompt neutron decay constant (α0), effective delayed neutron fraction (βeff) and neutron generation time (Λ) in a subcritical condition for the first operating core configuration of Tehran Research Reactor (TRR). The reactor core is considered to be in zero power (reactor power is less than 1 W) in the entire simulation process. The effect of some key parameters such as detector efficiency, detector position and its dead time on the results of simulation has been discussed as well. The results of proposed method in the current study are...
Semisolid Stir Joining of AZ91 Magnesium alloy
, M.Sc. Thesis Sharif University of Technology ; Aashuri, Hosseini (Supervisor)
Abstract
AZ91 is the most applicable alloy of magnesium alloys.Semisolid stir welding of AZ91 magnesium alloy was investigated due to its welding problem such oxide formation, hot cracking in weld metal, and high residual stress through solidification with special focus on the effect of the welding temperatures, stirring rates, and tool shape. The interlayer with thickness of 2mm was located between two AZ91 pieces with 7.5mm thickness. Then, they were heated to the desired temperatures (515C, 530C and 540C), the semisolid temperature of both base metal and interlayer. A grooved stirrer with six rotational speeds from 0rpm to 2000rpm was introduced into the stir weld seam and the welded coupons...
Instagram and its Relation to Moral Values
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Hassan (Supervisor)
Abstract
In this thesis, the value-ladenness or value-neutrality of technology, new social media and as a result Instagram is investigated. It is also discussed whether values can be taken into account during the design process of technical artefacts, including new social media and Instagram, and methods are developed for this purpose. Several methods have been developed for this purpose, some of them and their compatibility with modern social media are explained; including the Value-Sensitive-Design method and the disclosive computer ethics design method. The frameworks of ethical philosophy such as virtue ethics are reviewed and the appropriate ethical framework for the analysis of new social media...
Calculation of fuel burn up and radioactive inventory for HEU fuel element of Tehran Research Reactor
, Article International Conference on Nuclear Engineering, Proceedings, ICONE, 17 May 2010 through 21 May 2010 ; Volume 2 , 2010 ; 9780791849309 (ISBN) ; Vosoughi, N ; Hosseini, M ; Nuclear Engineering Division ; Sharif University of Technology
2010
Abstract
This paper presents a new approach for fuel burn up evaluation and radioactive inventory calculation used in Tehran Research Reactor. The approach is essentially based upon the utilization of a program written by C# which integrates the cell and core calculation codes, i.e., WIMSD-4 and CITVAP, respectively. Calculation of fuel burn up and radioactive inventories has been done for 26 core configuration of Tehran Research Reactor with HEU fuel element. The present inventory and fuel enrichment of each fuel element have been calculated
Preparation and characterization of yttrium iron garnet (YIG) nanocrystalline powders by auto-combustion of nitrate-citrate gel
, Article Journal of Alloys and Compounds ; Volume 430, Issue 1-2 , 2007 , Pages 339-343 ; 09258388 (ISSN) ; Madaah Hosseini, H. R ; Nemati, Z. A ; Sharif University of Technology
2007
Abstract
The nitrate-citrate gel exhibits auto-catalytic behavior, which can be used to synthesize nanocrystalline YIG powders. In this study, yttrium iron garnet (Y3Fe5O12) nanocrystalline powders were prepared by a sol-gel auto-combustion process. The influence of metal nitrates to citric acid molar ratio (MN/CA) of the precursor solution on the combustion behavior and crystallite size of synthesized powders was investigated by scanning electron microscopy (SEM), thermal analyses (DTA/TGA) and X-ray diffraction (XRD). The results show that with increasing MN/CA value, the combustion rate increases and the single-phase YIG forms at a higher temperature. The crystallite size of the single phase YIG...
Experimental and numerical fatigue life study of cracked AL plates reinforced by glass/epoxy composite patches in different stress ratios
, Article Mechanics Based Design of Structures and Machines ; Volume 49, Issue 6 , 2021 , Pages 894-910 ; 15397734 (ISSN) ; Safarabadi, M ; Ganjiani, M ; Mohammadi, E ; Hosseini, A ; Sharif University of Technology
Bellwether Publishing, Ltd
2021
Abstract
In this study, the fatigue behavior of composite reinforced cracked aluminum 1050 plates is investigated experimentally and numerically. The tests are conducted in four different stress ratios between 0 and 1. At first step, plates with similar cracks and geometries have been prepared. Then the glass/epoxy patches have been attached to the cracked plates using Araldite 2015 adhesive. Fatigue load has been applied to three cases of samples including non-patch, one-side patch and two-side patch, where in all stress ratios the maximum force is considered constant. A three-dimensional finite element analysis is developed in ABAQUS. A good correlation between finite element results and the...
Preparation and characterization of nanocrystalline misch-metal-substituted yttrium iron garnet powder by the sol-gel combustion process
, Article International Journal of Applied Ceramic Technology ; Volume 5, Issue 5 , 26 August , 2008 , Pages 464-468 ; 1546542X (ISSN) ; Madaah Hosseini, H. R ; Nemati, Z. A ; Sharif University of Technology
2008
Abstract
Nanocrystalline Y3-xMMxFe5O12 powders (MM denotes Misch-metal, x = 0.0, 0.25, 0.5, 0.75, and 1.0) were synthesized by a sol-gel combustion method. Magnetic properties and crystalline structures were investigated using X-ray diffraction (XRD), a vibrating sample magnetometer (VSM), and a scanning electron microscope. The XRD patterns showed that the single-phase garnet of Y3-xMMxFe5O12 was formed at x values ≤ 1.0. The saturation magnetization of powders increased with decreasing MM content and reached the maximum value at Y3 Fe5O12. The crystallite size of powders calcined at 800°C for 3 h was in the range of 38-53 nm. © 2008 American Ceramic Society
Synthesis of nanocrystalline yttrium iron garnets by sol-gel combustion process: The influence of pH of precursor solution
, Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 129, Issue 1-3 , 2006 , Pages 211-215 ; 09215107 (ISSN) ; Madaah Hosseini, H. R ; Nemati, Z. A ; Sharif University of Technology
2006
Abstract
The nitrate-citrate gels exhibit auto-catalytic behavior, which can be used to synthesize the nanocrystalline YIG powders. In this study yttrium iron garnet (Y3Fe5O12) nanocrystalline powders were prepared by a sol-gel auto-combustion process. The influence of pH value of the precursor solution on the combustion behavior and the garnet phase formation of synthesized powders were investigated by scanning electron microscopy (SEM), thermal analysis (DTA/TGA), infrared (IR) spectroscopy and X-ray diffraction technique (XRD). The results show that with increasing pH value, the combustion rate increases. The as-burnt powder prepared with pH 1 yielded a single phase YIG after calcination at 800...
L-lysine biodetector based on a TOCNFs-coated Quartz Crystal Microbalance (QCM)
, Article European Polymer Journal ; Volume 186 , 2023 ; 00143057 (ISSN) ; Iraji zad, A ; Vossoughi, M ; Hosseini, M ; Sharif University of Technology
Elsevier Ltd
2023
Abstract
Developing a simple, cost effective and accurate detection method for L-lysine (Lys), L-leucine (Leu) and glycine (Gly) as the important analytes in clinical diagnostics, biological processes and food industries is of great significance. Herein, we prepared spin-coated TEMPO-oxidized cellulose nanofibrils (TOCNFs) on Quartz Crystal Microbalance (QCM) chip to achieve QCM biodetectors. The coated QCMs were carefully characterized before and after interaction with amino acids (AA) using water contact angle (WCA), Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR), Raman spectroscopy, and scanning electron microscopy (SEM). In addition, to study the response of...
Lattice Boltzmann simulation of TiO2-water nanofluid in a curved boundary domain at high Rayleigh numbers
, Article Computers and Fluids ; Volume 168 , 30 May , 2018 , Pages 159-169 ; 00457930 (ISSN) ; Saidi, M. H
Elsevier Ltd
2018
Abstract
In this paper, a two-component Lattice Boltzmann Method (LBM) has been utilized to simulate the natural convection of TiO2-water nanofluid in a curved geometry. The main purpose of this research is to study the effect of nanoparticle size and also boundary conditions on the thermal characteristics of the nanofluid. Furthermore, the effect of Rayleigh number (Ra) and volume fraction of nanoparticles (ϕ) on the average Nusselt number (Nuave) have been investigated. Two different thermal boundary conditions, namely adiabatic and constant temperature, have been considered in the current work for the curved boundaries. The Rayleigh number varies from 103 to 109. Four different sizes, namely 10,...
High accurate three-dimensional neutron noise simulator based on GFEM with unstructured hexahedral elements
, Article Nuclear Engineering and Technology ; Volume 51, Issue 6 , 2019 , Pages 1479-1486 ; 17385733 (ISSN) ; Sharif University of Technology
Korean Nuclear Society
2019
Abstract
The purpose of the present study is to develop the 3D static and noise simulator based on Galerkin Finite Element Method (GFEM) using the unstructured hexahedral elements. The 3D, 2G neutron diffusion and noise equations are discretized using the unstructured hexahedral by considering the linear approximation of the shape function in each element. The validation of the static calculation is performed via comparison between calculated results and reported data for the VVER-1000 benchmark problem. A sensitivity analysis of the calculation to the element type (unstructured hexahedral or tetrahedron elements) is done. Finally, the neutron noise calculation is performed for the neutron noise...
Neutron spectrum unfolding using artificial neural network and modified least square method
, Article Radiation Physics and Chemistry ; Volume 126 , 2016 , Pages 75-84 ; 0969806X (ISSN) ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
In the present paper, neutron spectrum is reconstructed using the Artificial Neural Network (ANN) and Modified Least Square (MLSQR) methods. The detector's response (pulse height distribution) as a required data for unfolding of energy spectrum is calculated using the developed MCNPX-ESUT computational code (MCNPX-Energy engineering of Sharif University of Technology). Unlike the usual methods that apply inversion procedures to unfold the energy spectrum from the Fredholm integral equation, the MLSQR method uses the direct procedure. Since liquid organic scintillators like NE-213 are well suited and routinely used for spectrometry of neutron sources, the neutron pulse height distribution is...
3D neutron diffusion computational code based on GFEM with unstructured tetrahedron elements: A comparative study for linear and quadratic approximations
, Article Progress in Nuclear Energy ; Volume 92 , 2016 , Pages 119-132 ; 01491970 (ISSN) ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
In the present study, the comparison between the results obtained from the linear and quadratic approximations of the Galerkin Finite Element Method (GFEM) for neutronic reactor core calculation was reported. The sensitivity analysis of the calculated neutron multiplication factor, neutron flux and power distributions in the reactor core vs. the number of the unstructured tetrahedron elements and order of the considered shape function was performed. The cost of the performed calculation using linear and quadratic approximation was compared through the calculation of the FOM. The neutronic core calculation was performed for both rectangular and hexagonal geometries. Both the criticality and...
Development of galerkin finite element method three-dimensional computational code for the multigroup neutron diffusion equation with unstructured tetrahedron elements
, Article Nuclear Engineering and Technology ; Volume 48, Issue 1 , 2016 , Pages 43-54 ; 17385733 (ISSN) ; Sharif University of Technology
Korean Nuclear Society
2016
Abstract
In the present paper, development of the three-dimensional (3D) computational code based on Galerkin finite element method (GFEM) for solving the multigroup forward/adjoint diffusion equation in both rectangular and hexagonal geometries is reported. Linear approximation of shape functions in the GFEM with unstructured tetrahedron elements is used in the calculation. Both criticality and fixed source calculations may be performed using the developed GFEM-3D computational code. An acceptable level of accuracy at a low computational cost is the main advantage of applying the unstructured tetrahedron elements. The unstructured tetrahedron elements generated with Gambit software are used in the...
Neutron spectroscopy with soft computing: Development of a computational code based on Support Vector Machine (SVM) for reconstruction of neutron energy spectrum
, Article Journal of Instrumentation ; Volume 14, Issue 2 , 2019 ; 17480221 (ISSN) ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
This paper presents a developed computational code based on Support Vector Machine (SVM) for reconstruction of energy spectrum of neutron source. To reconstruct unknown energy spectrum using known neutron pulse height distribution, the developed machine is trained by known neutron pulse height distribution of detector and corresponding energy spectrum of neutron source. Validation and testing are the next steps to verify the validity of the calculations done with the developed computational code. The calculated neutron pulse height distributions due to randomly generated energy spectrum using MCNPX-ESUT (MCNPX-Energy engineering of Sharif University of Technology) computational code are used...
Neutron spectroscopy with soft computing: Unfolding of the neutron energy spectrum using the developed computer code based on Adaptive Group of Ink Drop Spread (AGIDS)
, Article Journal of Instrumentation ; Volume 14, Issue 3 , 2019 ; 17480221 (ISSN) ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
This paper presents the developed computer codes based on the Adaptive Group of Ink Drop Spread (AGIDS) algorithm [1] for the reconstruction of the energy spectrum of the neutron source. The required data are generated via simulation of the neutron pulse height distributions due to randomly generated energy spectra with the MCNPX-ESUT computer code [2]. The simulated neutron pulse height distributions and corresponding randomly generated energy spectra are the input and output data of the developed computer code, respectively. As a case study, the 241Am-9Be neutron source is studied and the simulation of the neutron pulse height distribution of the NE-213 liquid organic scintillator is...
Sensitivity analysis of the galerkin finite element method neutron diffusion solver to the shape of the elements
, Article Nuclear Engineering and Technology ; Volume 49, Issue 1 , 2017 , Pages 29-42 ; 17385733 (ISSN) ; Sharif University of Technology
Korean Nuclear Society
2017
Abstract
The purpose of the present study is the presentation of the appropriate element and shape function in the solution of the neutron diffusion equation in two-dimensional (2D) geometries. To this end, the multigroup neutron diffusion equation is solved using the Galerkin finite element method in both rectangular and hexagonal reactor cores. The spatial discretization of the equation is performed using unstructured triangular and quadrilateral finite elements. Calculations are performed using both linear and quadratic approximations of shape function in the Galerkin finite element method, based on which results are compared. Using the power iteration method, the neutron flux distributions with...