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    Turn-to-Turn Fault Detection in Power Transformers in the Presence of Inrush Current

    , M.Sc. Thesis Sharif University of Technology Fallah Mollamahmod, Mahdi (Author) ; Hajipour, Ehsan (Supervisor)
    Abstract
    One of the most critical equipments in power grids are power transformers, which are vulnerable to damage due to the possibility of faults in its various components. A very common category of such faults is turn-to-turn fault in its winding. This fault initiates by the aging of the winding insulation with a short circuit of several adjacent loops to each other and if it is not detected quickly by the transformer protection, it will spread rapidly and can lead to irreparable failure in the transformer. Traditionally, turn-to-turn fault should be detected by mechanical pressure relays, however, due to the poor performance of these relays in the rapid detection of this type of fault, in the... 

    Thermo-mechanical behavior of functionally graded circular sector plates

    , Article Acta Mechanica ; Volume 226, Issue 1 , 2014 , Pages 37-54 ; 00015970 Fallah, F ; Nosier, A ; Sharif University of Technology
    2014
    Abstract
    By reformulating the governing equations of the first-order theory into those describing the interior and edge-zone problems of the plate, closed-form solutions are presented for analysis of functionally graded circular sector plates with vertex angle (Formula presented.) whose radial edges are simply supported and subjected to transverse loading and heat conduction through the plate thickness. Various types of clamped, simply supported, and free-edge boundary supports are considered on the circular edge of the plate. The material properties are graded through the plate thickness according to a power-law distribution of the volume fraction of the constituents. The effects of material... 

    Nonlinear behavior of functionally graded circular plates with various boundary supports under asymmetric thermo-mechanical loading

    , Article Composite Structures ; Volume 94, Issue 9 , 2012 , Pages 2834-2850 ; 02638223 (ISSN) Fallah, F ; Nosier, A ; Sharif University of Technology
    2012
    Abstract
    The equilibrium equations of the first-order nonlinear von Karman theory for FG circular plates under asymmetric transverse loading and heat conduction through the plate thickness are reformulated into those describing the interior and edge-zone problems of the plate. A two parameter perturbation technique, in conjunction with Fourier series method is used to obtain analytical solutions for nonlinear behavior of functionally graded circular plates with various clamped and simply-supported boundary conditions. The material properties are graded through the plate thickness according to a power-law distribution of the volume fraction of the constituents. The results are verified with known... 

    Thermo-mechanical behavior of functionally graded circular sector plates

    , Article Acta Mechanica ; Volume 226, Issue 1 , January , 2015 , Pages 37-54 ; 00015970 (ISSN) Fallah, F ; Nosier, A ; Sharif University of Technology
    Springer-Verlag Wien  2015
    Abstract
    By reformulating the governing equations of the first-order theory into those describing the interior and edge-zone problems of the plate, closed-form solutions are presented for analysis of functionally graded circular sector plates with vertex angle (Formula presented.) whose radial edges are simply supported and subjected to transverse loading and heat conduction through the plate thickness. Various types of clamped, simply supported, and free-edge boundary supports are considered on the circular edge of the plate. The material properties are graded through the plate thickness according to a power-law distribution of the volume fraction of the constituents. The effects of material... 

    Time-indexed Mathematical Models for Order Acceptance and Scheduling Problems

    , M.Sc. Thesis Sharif University of Technology Fallah, Samira (Author) ; Kianfar, Farhad (Supervisor)
    Abstract
    Scheduling has been an active area of research for decades. A substantial amount of work has been done to define, classify, and solve scheduling problems. Most of these problems are computationally difficult to solve, and incorporating other decisions into them increases the complexity of these problems. This thesis focuses on order acceptance and scheduling (OAS) problems, and proposes time-indexed mixed integer and linear programming (MILP) models for the first time. An OAS problem can be defined with parameters of processing time, release date, due date, and deadline for each order. There are also a maximum revenue that will be brought by each order and an importance weight of each order.... 

    The Effect of Heat Treatment on Microstructure and Mechanical Properties of Directionally Solidified Nickel-based Superalloy GTD-111

    , M.Sc. Thesis Sharif University of Technology Fallah, Parastoo (Author) ; Varahram, Naser (Supervisor)
    Abstract
    The Ni-based superalloy GTD-111 possesses excellent hot corrosion resistance, high stability and strength at elevated temperature; accordingly, the alloy is used in manufacturing of the first stage blades of powerful gas turbines. In this study, effect of withdrawal rate from Bridgman furnace and precipitation hardening on the microstructure and microhardness of this superalloy were investigated. To this end, several experiments were carried out under growth rates of 1, 6 and 10 mm/min using Bridgman process under vacuum. Afterwards, the effects of homogenization treatment, partial dissolution with two different cooling rates (air and water) along with aging on the microstructure were... 

    On the nonlinear bending and post-buckling behavior of laminated sandwich cylindrical shells with FG or isogrid lattice cores

    , Article Acta Mechanica ; 2019 ; 00015970 (ISSN) Fallah, F ; Taati, E ; Sharif University of Technology
    Springer-Verlag Wien  2019
    Abstract
    The nonlinear governing equations of three shell theories (Donnell, Love, and Sanders) with first-order approximation and von Kármán’s geometric nonlinearity for laminated sandwich cylindrical shells with isotropic, functionally graded (FG) or isogrid lattice layers are decoupled. This uncoupling makes it possible to present a semi-analytical solution for the nonlinear bending and post-buckling behavior of short and long doubly simply supported, doubly clamped, and cantilever laminated sandwich cylindrical shells subjected to various types of thermo-mechanical loadings. The results for deflection, stress, critical axial traction, and mode shapes in FG shells are verified with those obtained... 

    On an extended Kantorovich method for the mechanical behavior of functionally graded solid/annular sector plates with various boundary conditions

    , Article Acta Mechanica ; Volume 228, Issue 7 , 2017 , Pages 2655-2674 ; 00015970 (ISSN) Fallah, F ; Khakbaz, A ; Sharif University of Technology
    Springer-Verlag Wien  2017
    Abstract
    Based on the first-order shear deformation plate theory, two approaches within the extended Kantorovich method (EKM) are presented for a bending analysis of functionally graded annular sector plates with arbitrary boundary conditions subjected to both uniform and non-uniform loadings. In the first approach, EKM is applied to the functional of the problem, while in the second one EKM is applied to the weighted integral form of the governing differential equations of the problem as presented by Kerr. In both approaches, the system of ordinary differential equations with variable coefficients in r direction and the set of ordinary differential equations with constant coefficients in θ direction... 

    On the nonlinear bending and post-buckling behavior of laminated sandwich cylindrical shells with FG or isogrid lattice cores

    , Article Acta Mechanica ; 2019 ; 00015970 (ISSN) Fallah, F ; Taati, E ; Sharif University of Technology
    Springer-Verlag Wien  2019
    Abstract
    The nonlinear governing equations of three shell theories (Donnell, Love, and Sanders) with first-order approximation and von Kármán’s geometric nonlinearity for laminated sandwich cylindrical shells with isotropic, functionally graded (FG) or isogrid lattice layers are decoupled. This uncoupling makes it possible to present a semi-analytical solution for the nonlinear bending and post-buckling behavior of short and long doubly simply supported, doubly clamped, and cantilever laminated sandwich cylindrical shells subjected to various types of thermo-mechanical loadings. The results for deflection, stress, critical axial traction, and mode shapes in FG shells are verified with those obtained... 

    Non-linear thermo-mechanical cylindrical bending of functionally graded plates

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 222, Issue 3 , 2008 , Pages 305-318 ; 09544062 (ISSN) Fallah, F ; Nosier, A ; Sharif University of Technology
    2008
    Abstract
    Based on the first-order non-linear von Karman theory, cylindrical bending of functionally graded (FG) plates subjected to mechanical, thermal, and combined thermo-mechanical loadings are investigated. Analytical solutions are obtained for an FG plate with various clamped and simply-supported boundary conditions. The closed form solutions obtained are very simple to be used in design purposes. The material properties are assumed to vary continuously through the thickness of the plate according to a power-law distribution of the volume fraction of the constituents. The effects of non-linearity, material property, and boundary conditions on various response quantities are studied and... 

    Calculation of VVER-1000 reactor scaling factor for inference of core barrel motion

    , Article Annals of Nuclear Energy ; Vol. 63 , 2014 , pp. 205-208 ; ISSN: 03064549 Fallah, V. F ; Vosoughi, N ; Sharif University of Technology
    2014
    Abstract
    To quantify the core barrel motion (CBM) in a pressurized water reactor, a scaling factor can be calculated to convert the Root Mean Square (RMS) value of the ex-core signals (%) to the core barrel motion amplitude (mil) (Thompson et al., 1980). In the current paper, a scaling factor is calculated using the direct and adjoint methods for a typical VVER-1000 reactor. The scaling factor is calculated using the perturbed parameters that result from CBM. The results show that the calculated scaling factors are not the same in one and two-dimensional modeling, and strongly depend on the ex-core detector location. The linearity assumption of relative detector response versus the small displacement... 

    Nonlinear free vibration and post-buckling analysis of functionally graded beams on nonlinear elastic foundation

    , Article European Journal of Mechanics, A/Solids ; Volume 30, Issue 4 , July , 2011 , Pages 571-583 ; 09977538 (ISSN) Fallah, A ; Aghdam, M. M ; Sharif University of Technology
    2011
    Abstract
    In this study, simple analytical expressions are presented for large amplitude free vibration and post-buckling analysis of functionally graded beams rest on nonlinear elastic foundation subjected to axial force. Euler-Bernoulli assumptions together with Von Karman's strain-displacement relation are employed to derive the governing partial differential equation of motion. Furthermore, the elastic foundation contains shearing layer and cubic nonlinearity. He's variational method is employed to obtain the approximate closed form solution of the nonlinear governing equation. Comparison between results of the present work and those available in literature shows the accuracy of this method. Some... 

    HSE management challenges in Iranian civil projects

    , Article Proceedings, Annual Conference - Canadian Society for Civil Engineering, 14 June 2011 through 17 June 2011 ; Volume 3 , 2011 , Pages 2268-2277 ; 9781618392183 (ISBN) Fallah, F ; Mortaheb, M. M ; Sharif University of Technology
    2011
    Abstract
    HSE management is one of the key topics in project management that plays a significant role in indication of success and soundness of projects. According to the official reports and statistics, construction industry has annually incurred a great deal of expenses and losses due to neglecting the role of HSE issues in the projects worldwide. Since many challenges and problems related to HSE faced Iranian civil engineers and construction managers, recently the HSE have been regarded as a highly critical issue in Iran. Observations show that many Iranian managers and engineers, in their daily activities, have the tendency to ignore the HSE related rules. The aim of this research is to evaluate... 

    Nonlinear Elastic Analysis of FG Arcs under Thermo-Mechanical Loading

    , M.Sc. Thesis Sharif University of Technology Rouholamini, Reza (Author) ; Fallah, Famida (Supervisor)
    Abstract
    Arcs and rings are used extensively in structures such as submarines and bridges due to their particular geometry. On the other hand, in multi-part rocket, due to the high temperature gradients, they form the fastening rings of functional materials (FGM). Considering the importance of this structural element, in this thesis, linear and nonlinear behavior (including bending and post-buckling) of rings made of functionally graded materials under different types of thermo-mechanical loading has been investigated. First, the governing equations are derived from the principle of minimum potential energy, based on the two theorems of Donnell and Love. Donnell's theory equations are solved... 

    Non-linear analysis of functionally graded sector plates with simply supported radial edges under transverse loading

    , Article Mechanics of Advanced Composite Structures ; Volume 6, Issue 1 , 2019 , Pages 65-74 ; 24234826 (ISSN) Fallah, F ; Karimi, M. H ; Sharif University of Technology
    Semnan University, Faculty of Mechanical Engineering  2019
    Abstract
    In this study, nonlinear bending of functionally graded (FG) circular sector plates with simply supported radial edges subjected to transverse mechanical loading has been investigated. Based on the first-order shear deformation plate theory with von Karman strain-displacement relations, the nonlinear equilibrium equations of sector plates are obtained. Introducing a stress function and a potential function, the governing equations which are five non-linear coupled equations with total order of ten are reformulated into three uncoupled ones including one linear edge-zone equation and two nonlinear interior equations with total order of ten. The uncoupling makes it possible to present... 

    MBBR and MBR Reactor Configuration for Better Performance

    , M.Sc. Thesis Sharif University of Technology (Author) ; Borgheei, Mahdi (Supervisor)
    Abstract
    Membrane bioreactors (MBRs) which are commonly understood as the combination of membrane filtration and biological treatment using activated sludge have several advantages, but membrane fouling reduces the membrane efficiency, permeability and lifetime. An alternative is replacing a moving bed biofilm reactor (MBBR) with the activated sludge system which may reduce the effect of membrane fouling. The sludge produced in MBBRs has poor settling characteristics, therefore, their efficiency is limited by the sedimentation tank performance and they require a larger settling surface. The combination of moving bed biofilm reactors and membrane bioreactors can compensate for the drawbacks of both of... 

    Evaluation of Different Water and Gas Injection Scenarios for Improving Recovery of One of the Iranian South West Reservoirs

    , M.Sc. Thesis Sharif University of Technology Fallah Tafty, Mona (Author) ; Masihi, Mohsen (Supervisor)
    Abstract
    Increasing the global demand for energy and decreasing the production rate of oil reservoirs have forced the oil companies to focus on enhanced oil recovery (EOR) extensively. This paper summarizes the design, reservoir simulation, and results of different gas injection scenarios in one of the Iranian complex oil reservoirs. This complex reservoir is located in the south west of Iran and is made up of sandstone, limestone, and dolomite layers. It is an under saturated reservoir with no gas cap but with a strong aquifer. Oil production has started in 1977, but due to strong aquifer the production is still in the plateau period. In this study, by simulation, it is estimated that natural... 

    Simulation of Mild Steel Corrosion in H2S Aqueous Solution

    , M.Sc. Thesis Sharif University of Technology Fallah Mohammadi, Ehsan (Author) ; Dolati, Abolghasem (Supervisor)
    Abstract
    Corrosion is a main problem for oil and gas industries at refineries and petrochemical process. Presence of sulfur compounds in crude oil and creation a corrosive environment for steel structure, caused failure and unfortunate damages. H2S which present at cracking and sweetening process in sour feed obtain hydrogen atoms that can diffuse into steel structure which involve with its instruments and consequent to hydrogen damage .distribution and storage of these sour environments can be done by high strength low alloy steel (HSLA).Electrochemical hydrogen permeation test were performed to measure the hydrogen permeation current through A106/GR B pipeline steel in the electrolytes simulating... 

    Automatic Web Services Composition Using HSIP

    , M.Sc. Thesis Sharif University of Technology Aram, Siamak (Author) ; Soleyman Fallah, Mehran (Supervisor)
    Abstract
    We propose Hierarchical Web Services Composer (HWSC) as a technique for fully automatic Web services composition. It takes functional and nonfunctional requirements of a Web service and returns possible compositions that realize those requirements. In doing so, HWSC deploys the Hierarchical Services of Interacting Processes (HSIP), a formalism of concurrent systems, and integrates its capabilities with the existing methods and protocols for service oriented computing. The proposed framework technique is then analyzed and validated through a number of real-life examples  

    Calculation of the Scaling Factor for WWER-1000 Reactor (Boushehr)

    , M.Sc. Thesis Sharif University of Technology Farhang Fallah, Vahid (Author) ; Vossoughi, Nasser (Supervisor)