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    Development of a Multi-Dimensional and Multi-Group Code for Black and Gray Dancoff Factor Calculation Based on Monte Carlo Method in Various Geometries

    , M.Sc. Thesis Sharif University of Technology Ghaderi Mazaher, Meysam (Author) ; Vossoughi, Nasser (Supervisor)
    Abstract
    Most of the nuclear codes used equivalence between a homogeneous and heterogeneous region to calculate resonance shelf-shielding. when fuels are together in a lattice arrangement, As a good approximation in the resonance shelf-shielding calculation, one could only consider a single fuel lump and consider the effect of neighbor fuels with a correction factor, i.e. the Dancoff coefficient. So far, several methods have used for calculating the Dancoff coefficient, but accuracy of these methods did not improved. In this thesis a computer program (MCDAN-3D) is developed for calculation of the multi-dimension and multi-group black and gray Dancoff coefficient, based on Monte Carlo, escape... 

    Hybrid control and motion planning of dynamical legged locomotion

    , Book ; Sadati, Nasser
    Wiley  2012
    Abstract
    This book provides a comprehensive presentation of issues and challenges faced by researchers and practicing engineers in motion planning and hybrid control of dynamical legged locomotion. The major features range from offline and online motion planning algorithms to generate desired feasible periodic walking and running motions and tow-level control schemes, including within-stride feedback laws, continuous time update laws and event-based update laws, to asymptotically stabilize the generated desired periodic orbits. This book describes the current state of the art and future directions across all domains of dynamical legged locomotion so that readers can extend proposed motion planning... 

    Corrosion inhibition of a novel antihistamine-based compound for mild steel in hydrochloric acid solution: experimental and computational studies

    , Article Scientific Reports ; Volume 12, Issue 1 , 2022 ; 20452322 (ISSN) Ghaderi, M ; Ahmad Ramazani, S. A ; Kordzadeh, A ; Mahdavian, M ; Alibakhshi, E ; Ghaderi, A ; Sharif University of Technology
    Nature Research  2022
    Abstract
    Focused on the assessment of the diphenhydramine hydrochloride (DPH) capabilities as an alternative to conventional and harmful industrial corrosion inhibitors, electrochemical techniques were employed. The optimum concentration of 1000 ppm was determined by molecular simulation and validated through electrochemical experiments. The results acquired from the electrochemical impedance spectroscopy (EIS) study showed that DPH at a concentration of 1000 ppm has a corrosion efficiency of 91.43% after 6 h immersion. The DPH molecules' orientation on the surface was assessed based on EIS predicting horizontal adsorption on the surface. Molecular simulations were done to explore the adsorption... 

    Effects of material properties estimations on the thermo-elastic analysis for functionally graded thick spheres and cylinders

    , Article ASME International Mechanical Engineering Congress and Exposition, IMECE 2007, Seattle, WA, 11 November 2007 through 15 November 2007 ; Volume 10 PART B , 2008 , Pages 843-846 ; 0791843041 (ISBN); 9780791843048 (ISBN) Ghaderi, P ; Bankehsaz, M ; Sharif University of Technology
    2008
    Abstract
    In this paper effects of material properties estimations, used for particulate reinforced composites, on the thermo-mechanical response of functionally graded sphere and cylinder are presented. A numerical solution for an arbitrary material gradation is obtained for each geometry independently. With this assumption, the governing partial differential equations are reduced to an ordinary differential equation in each geometry. The thermo-elastic solution for hollow sphere is derived using spherical symmetry. However, plane strain and axial symmetry are assumed for solving hollow cylinder. In the numerical method, radial domain is divided into some finite sub-domains and material properties... 

    Novel post-processing methods used in detection of blotches in image sequences

    , Article AEU - International Journal of Electronics and Communications ; Volume 58, Issue 1 , 2004 , Pages 58-64 ; 14348411 (ISSN) Ghaderi, M ; Kasaei, S ; Sharif University of Technology
    Elsevier GmbH  2004
    Abstract
    Blotches are the common artifacts in degraded motion picture sequences. They are usually caused by placing dust and dirt on film surfaces as well as abrasion of film materials. Blotches are seen as dark and bright flashes spreading through the frames, randomly. The spike detection index (SDIa) method is the simplest approach used to detect these artifacts. However, when the motion vectors are not precise enough in some points they might be declared as blotches too. This situation can also occur in areas containing a high level of noise. To overcome these difficulties, two post-processing methods are proposed in this paper. In the first method, the edge points are first omitted from the set... 

    Design of Fault Tolerant Processor for Implementation on SRAM Based FPGAs

    , M.Sc. Thesis Sharif University of Technology Ghaderi, Zana (Author) ; Miremadi, Ghasem (Supervisor)
    Abstract
    Vulnerability of SRAM-based FPGAs to soft errors signals the importance of applying fault-tolerant methods in FPGAs used in safety-critical applications. Previous methods to protect SRAM-based FPGAs impose significant area and power overheads. Additionally, they suffer from susceptibility of configuration bits to Single Event-Multiple Upsets (SEMU). This thesis presents a Highly Available Fault-Tolerant Architecture (HAFTA) to protect SRAM-based FPGA designs against SEMUs in both configuration and user bits. In HAFTA, the entire design is duplicated and the main and replica flip-flops are compared at each clock cycle to detect any possible mismatch. To save the latest correct state of the... 

    Design and Fabrication of Electronic Subsystems for NFCVD

    , M.Sc. Thesis Sharif University of Technology Ghaderi, Erfan (Author) ; Rashidian, Bizhan (Supervisor)
    Abstract
    The fabrication of future electronic and optical devices will require advanced nanofabrication techniques that realize high spatial resolution and high precision in controlling size and position, and that are applicable to various materials. Near-field CVD (NF-CVD) was proposed to solve these problems with no need to perform nanolithography prcesses. NFCVD system has two major subsystems, first vacuum chamber and gas distribution system for delivering parent gases to the chamber and second, a nanopositiong system to keep the probe and the sample in the constant systems.In this dissertation we have set up a piezoelectric nanopositiong system and its driver modules. The positioning accuracy... 

    Fabrication of AZ91/ SiCp Composite In Semi-Solid State By Using Electromagnetic Stirring, Microstructures And Mechanical Properties

    , M.Sc. Thesis Sharif University of Technology Ghaderi, Mohammad (Author) ; Aashuri, Hossein (Supervisor)
    Abstract
    In this study AZ91 alloy reinforced by SiC particles processed by semi-solid casting was produced by using electromagnetic stirrer. In order to prevent ignition and oxidation of the melted AZ91 alloy 1 Wt.% of calcium was added to the melt. In order to surface oxidation of SiC particles, they were heat treated in 1100 ᵒC for 2 hours before adding to the melt. Different methods of adding SiC particles to the melt were investigated. Particle distribution in the matrix was studied qualitatively and quantitatively using microscopic images and image analysis, respectively. It is shown that higher amount of reinforcement particle need to be added to the melt in multi-steps. Frequency versus... 

    Thermodynamic Optimization of a Gifford-McMahon Cycle using Exergy Analysis

    , M.Sc. Thesis Sharif University of Technology Ghaderi, Hanieh (Author) ; Afshin, Hossein (Supervisor)
    Abstract
    Helium, a valuable substance with unique properties, is widely used in various fields such as medicine, life sciences, electronic and military industries, and the industries which require low- temperature cooling. Driven by the increasing global demand for helium, research laboratories and industries are turning to small-scale refrigeration and liquefaction cycles. GM cryocoolers have found widespread applications in cryogenics due to its simplicity, high reliability and cost-effectiveness. The complexities of GM cryocooler performance pose significant challenges to achieving optimal efficiency and operation so developing a simplified model of the cycle is crucial. In this research, the... 

    Development of a 3D multigroup program for dancoff factor calculation in pebble bed reactors

    , Article Annals of Nuclear Energy ; Vol. 72, issue , 2014 , pp. 311-319 ; ISSN: 03064549 Ghaderi Mazaher, M ; Vosoughi, N ; Sharif University of Technology
    2014
    Abstract
    The evaluation of multigroup constants in reactor calculations depends on several parameters. One of these parameters is the Dancoff factor which is used for calculating the resonance integral and flux depression in the resonance region in heterogeneous systems. In the current paper, a computer program (MCDAN-3D) is developed for calculating three dimensional black and gray Dancoff coefficients, based on Monte Carlo, escape probability and neutron free flight methods. The developed program is capable to calculate the Dancoff factor for an arbitrary arrangement of fuel and moderator pebbles. Moreover this program can simulate fuels with homogeneous and heterogeneous compositions. It might... 

    Development of a 3D program for calculation of multigroup Dancoff factor based on Monte Carlo method in cylindrical geometry

    , Article Annals of Nuclear Energy ; Volume 78 , 2015 , Pages 49-59 ; 03064549 (ISSN) Ghaderi Mazaher, M ; Vosoughi, N ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    Evaluation of multigroup constants in reactor calculations depends on several parameters, the Dancoff factor amid them is used for calculation of the resonance integral as well as flux depression in the resonance region in the heterogeneous systems. This paper focuses on the computer program (MCDAN-3D) developed for calculation of the multigroup black and gray Dancoff factor in three dimensional geometry based on Monte Carlo and escape probability methods. The developed program is capable to calculate the Dancoff factor for an arbitrary arrangement of fuel rods with different cylindrical fuel dimensions and control rods with various lengths inserted in the reactor core. The initiative... 

    An investigation of shear failure in welded channel and angle brace members

    , Article Structures ; Volume 45 , 2022 , Pages 1287-1306 ; 23520124 (ISSN) Ghaderi Garekani, M ; Maleki, S ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    Shear yielding (SY) and shear rupture (SR) are base metal failure modes in welded connections of brace members to gusset plates. Although gusset plated connections have been extensively investigated in the past nonetheless, the shear failure limit states of welded brace members have not received significant attention. This paper aims to shed some light on the shear failure mechanism and strength of welded brace members consisting of single and double channels and angles. For this purpose, a nonlinear finite element (FE) model with ductile damage simulation is developed and validated against the authors’ experiments and other available test results. Then an extensive parametric study using... 

    Experimental and numerical investigations of block shear failure in gusset plates welded to double angle members

    , Article Structures ; Volume 48 , 2023 , Pages 1356-1372 ; 23520124 (ISSN) Ghaderi Garekani, M ; Maleki, S ; Sharif University of Technology
    Elsevier Ltd  2023
    Abstract
    Double angle braces are used extensively in structures to resist lateral loads such as wind, earthquake, and blast loads. A possible failure mode in the gusset plate when all-around weld is used for the angles is the block shear failure. To date, only limited test data on welded gusset plates failing in this mode have been reported in the literature, and all of them only considered concentrically loaded gusset plates. This paper investigates the block shear failure in welded gusset plates experimentally and numerically when connected to double angle members with possible in-plane load eccentricity effects. The test results, including failure loads, fracture sequences, and load-displacement... 

    Numerical Study of Load Eccentricity Effects on Block Shear Rupture of Welded Gusset Plates

    , Article International Journal of Steel Structures ; Volume 23, Issue 4 , 2023 , Pages 1148-1163 ; 15982351 (ISSN) Ghaderi Garekani, M ; Maleki, S ; Sharif University of Technology
    Korean Society of Steel Construction  2023
    Abstract
    Block shear rupture is a potential failure mode in welded steel gusset plates. The research on this failure mode in welded connections is scarce, and in available few studies, only concentric loading condition has been considered. Nevertheless, gusset plates are often loaded eccentrically, either in-plane or out-of-plane, depending on the connection. This paper examines the block shear failure in welded gusset plates under eccentric loading. First, an advanced nonlinear finite element model with ductile fracture prediction capability was developed and verified in detail against the authors’ experiment. Then, a comprehensive parametric study consisting of 260 connections was performed. Based... 

    Some Combinatorial Properties of Fullerene Graphs

    , M.Sc. Thesis Sharif University of Technology Ghaderi, Shadisadat (Author) ; Mahmoodian, Abadolla (Supervisor)
    Abstract
    In the study of molecules and chemical structures, especially fullerenes, they can be modeled to graphs. In this way, we can consider some chemical properties as graphical properties such as, perfect matching, connectivity, Hamiltonian; in order to obtain some results about some families of chemical structures.In this thesis, at first we mention some graphical and combinatorial properties. Then,we survey some results about fullerenes, and finally we investigate some properties of specific families of fullerenes. Furthermore, we mention some existing open problems in each case  

    Simulation of Coolant Temperature Variation in VVER-1000 Reactor Using Temperature Noise Analysis

    , M.Sc. Thesis Sharif University of Technology Nourollahi, Reza (Author) ; Vossoughi, Nasser (Supervisor)
    Abstract
    Temperature noise phenomenon in nuclear reactors results to the vital information about the system. This phenomenon may originate from coolant inlet temperature fluctuations, coolant fluid velocity fluctuations or the reactor power fluctuations in PWR reactors. Diagnosis of such temperature noise sources shall improve the reactor control and protection.The present research aims to develop a software to model the temperature noise in the axial direction of a single channel comprises of fuel rod and the associated coolant to recognize the type of temperature noise sources. In this regard, research stages are as follows: first the temperature noise caused by three conventional noise sources in... 

    Adaptive-Robust Control of Dynamic Systems Using Orthonormal Filters

    , M.Sc. Thesis Sharif University of Technology Hoshyar, Mohsen (Author) ; sadati, Nasser (Supervisor)
    Abstract
    In this research, using orthonormal filters, an adaptive-robust controller is designed for a class of SISO dynamic systems for which the input and output datas are available. First, Laguerre filters are combined with orthonormal Chebyshev functions to increase the capability of Laguerre filters in identification of systems with unknown dynamics. Then, the resulted Lagueree-Chebyshev structure is used for closed loop identification of the system and controller is designed. Moreover, RBF neural networks are used to approximate some nonlinear terms appearing in the controller design process.
    Finally, in order to minimize the control effort, a new approach is proposed that leads to a set... 

    , M.Sc. Thesis Sharif University of Technology Zamzamian, Mehrdad (Author) ; Vosoughi, Nasser (Supervisor)
    Abstract
    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,... 

    Olympic Games Scheduling

    , M.Sc. Thesis Sharif University of Technology Ghorbanian, Nafiseh (Author) ; Salmasi, Nasser (Supervisor)
    Abstract
    In the present work, the problem of Olympic Games scheduling is investigated. Due to the high number of matches and limited number of resources, scheduling of the Olympic Games is a difficult and time consuming job. Also a balanced distribution of medals on the days of Olympic Games keep each day attractive for the people and prevent sudden changes in the medal ranking of countries. So, in regard to the limitations of the problem and to balance the distribution of medals, the Olympic Games are scheduled. In order to do that, at first, two mathematical models are presented. One of them is for obtaining the feasible and optimum solution in a specified period of time. The other model presents a... 

    Neutronic Simulation of Pebble Bed Reactors

    , M.Sc. Thesis Sharif University of Technology Abedi, Amin (Author) ; Vossoughi, Nasser (Supervisor)
    Abstract
    The Very-High Temperature Reactor (VHTR) design is one of the six candidates for the Generation IV nuclear reactors. The reactor core type of the VHTR design is either prismatic or pebble-bed. In pebble bed reactors, the core is filled of thousands of graphite and fuel pebbles. Fuel pebbles in these reactors consist of TRISO particles, which are embedded in a graphite matrix stochastically. The reactor core is also stochastically filled up of fuel and dummy pebbles with an unequal ratio. These two stochastic geometries are the so-called double heterogeneous of this type of reactors. In the current study, a...