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    Online-Distributed Mechanism Design

    , M.Sc. Thesis Sharif University of Technology Asghariyan Rezayi, Ahmad (Author) ; Ghodsi, Mohammad (Supervisor)
    Abstract
    The concept of Online-Distributed Mechanism Design, is taken from the two concepts of Online Mechanism and Distributed Mechanism and speaks of an environment which is dynamic when there is no trusted center to do the computation. This problem is stated in this thesis for the first time and by the thesis we gave the first results in some of the up coming fields of Online-Distributed Mechanism. These feilds would be defined by different assupmtions about dynamic environments and the way of distributing of computation among agents. We consider single valued preference domains in the absence of any trusted center and in the presence of an enforcer. Then we try to design truthful auctions for... 

    Damage Detection and Structure Health Monitoring With Hybrid Dynamic Methods

    , M.Sc. Thesis Sharif University of Technology Rezayi, Vahid (Author) ; Golafshani, Ali Akbar (Supervisor)
    Abstract
    structures during their service life continually accumulate damage as a result of the action of various environmental forces. Clearly the development of robust techniques for early damage detection is crucial to avoid the possible occurrence of catastrophic structural failure. In a big picture we can divide process into two subcategories: first – we need modal properties of structure. In this case we install several motion sensors on structure and collect their data. Then use a group of methods named as System Identification Process to discover dynamic properties of structure as natural frequencies and mode shapes. Three famous system identification method have been used in this thesis and... 

    Analytical Solution of the Swirl Flow in Combustion Chamber of a Hybrid Rocket Engine

    , M.Sc. Thesis Sharif University of Technology Mohammad Beiki, Shahab (Author) ; Farahani, Mohammad (Supervisor) ; Rezayi, Hadi ($item.subfieldsMap.e)
    Abstract
    Hybrid engines are one of a variety of chemical propulsion systems that have been given special attention in recent years by various industries such as space and defense. The most important reasons for considering this type of system are its high safety, its affordable price compared with liquid fuel propulsion systems, the possibility of switching on and off and changing thrust. This system has a lot of disadvantages as well. This system cannot meet all the needs of different industries due to the low regression rate and, consequently, the limitation of the operating range, thrusts and special impulse. As a result, increasing the fuel regression rate in these engines can greatly expand... 

    IoT-based stochastic EMS using multi-agent system for coordination of grid-connected multi-microgrids

    , Article International Journal of Electrical Power and Energy Systems ; Volume 151 , 2023 ; 01420615 (ISSN) Mollayousefi Zadeh, M ; MohammadAli Rezayi, P ; Ghafouri, S ; Alizadeh, M. H ; Gharehpetian, G. B ; Sharif University of Technology
    Elsevier Ltd  2023
    Abstract
    A multi-microgrid system – containing various complementary energy sources – must coordinate the power flow among microgrids and the utility grid for stability and reliability enhancement, and also should obtain optimum energy management. Multi-agent-based optimization techniques are ideal for the management of interconnected microgrids, due to their decentralized nature and multifactorial approach in the decision-making process. In this paper, an optimization model is proposed for interconnected multi microgrids which considers the overall cost of the system. For optimum system operation, the hierarchical energy management system is utilized based on the multi-agent systems (MAS) theory.... 

    Manufacture of Smart Drug Delivery System with UCST Polymers

    , M.Sc. Thesis Sharif University of Technology Karimi, Ahmad Reza (Author) ; Ramazani, Ahmad (Supervisor)
    Abstract
    Smart heat-sensitive polymers play a unique role in drug delivery systems due to reversible behavior in response to environmental changes, especially temperature changes. Among the heat-sensitive polymers, UCST polymers due to their specific behavior and very little-known polymers with this feature are the subject of many new researches. In the present study, New designed temperature-sensitive polymers with UCST capability based on acrylamide and vinyl acetate were synthesized. These copolymers were synthesized in different percentages of acrylamide by free radical polymerization in solution conditions. All polymers compounds were characterized by H-NMR, FT-IR, DSC and GPC measurements. The... 

    Numerical study of lorentz force interaction with micro structure in channel flow

    , Article Energies ; Volume 14, Issue 14 , 2021 ; 19961073 (ISSN) Ahmad, S ; Ali, K ; Ahmad, S ; Cai, J ; Sharif University of Technology
    MDPI AG  2021
    Abstract
    The heat transfer Magnetohydrodynamics flows have been potentially used to enhance the thermal characteristics of several systems such as heat exchangers, electromagnetic casting, adjusting blood flow, X-rays, magnetic drug treatment, cooling of nuclear reactors, and magnetic devices for cell separation. Our concern in this article is to numerically investigate the flow of an incompressible Magnetohydrodynamics micropolar fluid with heat transportation through a channel having porous walls. By employing the suitable dimensionless coordinates, the flow model equations are converted into a nonlinear system of dimensionless ordinary differential equations, which are then numerically treated for... 

    A numerical approach for analyzing the electromagnetohydrodynamic flow through a rotating microchannel

    , Article Arabian Journal for Science and Engineering ; Volume 48, Issue 3 , 2023 , Pages 3765-3781 ; 2193567X (ISSN) Ali, K ; Ahmad, A ; Ahmad, S ; Ahmad, S ; Jamshed, W ; Sharif University of Technology
    Institute for Ionics  2023
    Abstract
    The purpose of the paper is to develop a mathematical foundation for exploring the complex interaction of Coriolis and Lorentz forces with the electromagnetohydrodynamic (EMHD) flow of a power-law fluid inside a microchannel with wall slip condition. Both the Lorentz and Coriolis forces act orthogonally to each other. Mathematical modeling of the problem is based on a set of classical Maxwell and Navier–Stokes equations, which are subsequently solved numerically by employing an implicit finite difference methodology. The numerical solution thus obtained has been found to be in an excellent agreement correlation with the ones reported in the scientific literature, for some limiting cases. A... 

    Implementation of new stepped horn in rotary ultrasonic machining of NOMEX honeycomb composites

    , Article Journal of Mechanical Science and Technology ; Volume 38, Issue 9 , 2024 , Pages 4983-4988 ; 1738494X (ISSN) Ahmad, S ; Sharif University of Technology
    2024
    Abstract
    Performance of rotary ultrasonic machining (RUM) system greatly influences by appropriate design of ultrasonic horn. Ultrasonic stepped horn gives high amplitude of vibration and better cutting efficiency but design and integration of horn with RUM system is highly intricate. Therefore, systematic study on design and implementation of ultrasonic stepped horn was needed in order to achieve better efficiency of RUM process. This paper focuses on design aspects of ultrasonic stepped horn by theoretical, FE simulations and modeling techniques. The designed horn was integrated with RUM system, performance was measured in terms of ultrasonic resonant frequency through FE simulations and modeling... 

    A self-similar approach to study nanofluid flow driven by a stretching curved sheet

    , Article Symmetry ; Volume 14, Issue 10 , 2022 ; 20738994 (ISSN) Ali, K ; Jamshed, W ; Ahmad, S ; Bashir, H ; Ahmad, S ; Tag El Din, E.S.M ; Sharif University of Technology
    MDPI  2022
    Abstract
    Nano-fluids have considerable importance in the field of thermal development that relates to several industrial systems. There are some key applications in recent construction systems flow, as well as microscale cooling gadgets and microstructure electric gadgets for thermal migration. The current investigation concludes the study of electrically conducting nano-fluid flow and heat transfer analysis in two-dimensional boundary layer flow over a curved extending surface in the coexisting of magnetic field, heat generation and thermal radiation. The small sized particles of copper (Cu) are taken as nanoparticles and water is assumed to be the base fluid. We used quasi-linearization and central... 

    Thin Film Thickness Measurement Using Colors of Interference Fringes

    , M.Sc. Thesis Sharif University of Technology Sadegh, Sanaz (Author) ; Amjadi, Ahmad (Supervisor)
    Abstract
    There are several methods for measuring thin film thickness, however, for the analysis of liquid film motors [1] we need a method which is capable of measuring the thickness using a single image of the film. In this work, we use the colors that appear on thin films, such as soup bubbles, which is a result of light interference to calculate the thickness of the layer  

    Thermal Relaxation Time Of Healthy and Cancerous Tissue In Pulsed Laser Using Monte Carlo Simulation

    , M.Sc. Thesis Sharif University of Technology Khaze, Mehran (Author) ; Amjadi, Ahmad (Supervisor)
    Abstract
    Thermal relaxation time is the time when maximum temperature of a particle get to 1/e of it’s initial value. The destruction of a tissue depends to this important parameter. This parameter has studied by Monte Carlo simulation of pulsed laser in to environment as healthy and cancerous tissue. The main goal of this method is providing proper temperature in a special area so that minimize thermal destruction around that area. In this thesis, temperature distribution of tissue that is caused by pulsed laser, has solved by new method;in this new method the pulse duration uses for Monte Carlo simulation. Also using the solution of radiation transfer equation by Discretes Ordinate Method, new... 

    Effect of Amplitude of Electric Field on the Rotation of Liquid Film

    , M.Sc. Thesis Sharif University of Technology Mashhadi, Meysam (Author) ; Amjadi, Ahmad (Supervisor)
    Abstract
    By direct and alternating electric field applied to thin film of liquid suspended in the air we can spin out and control it. Rotation pattern depends on the geometry of the electrodes and the applied magnetic field. This is called a rotating liquid film (Liquid Film Motor). To determine the cause of rotation, different models have been proposed. In this project we have tried to check the accuracy of any of the models. Using particle velocimetry using the photo, we calculate the velocity pattern. Then, using the Navier-Stokes equation calculate the acceleration and viscosity from the velocity. Then, for a special arrangement using a finite diffrent method, electric potential and the electric... 

    Design and Build an Acoustic Tweezers and Move up the Polystyrene Particles

    , M.Sc. Thesis Sharif University of Technology Ghavidel, Amir (Author) ; Amjadi, Ahmad (Supervisor)
    Abstract
    Ultrasound waves have attracted substantial attention due to their potential for trapping the small particles, which cannot be handled by usual tweezers. The acoustic tweezer is a technology that is able to tarp and control the movement of micrometer to millimeter objects by standing or focused sound waves. Acoustic tweezers are the subject of many researches around the world, due to simplicity, cost-effective, biocompatibility and most important better performance in non-transparent optical environments, compared with optical tweezers.In this project, by using a ring piezoelectric and a power amplifier, an acoustic tweezer was designed and constructed. Moreover, the polystyrene particles... 

    Prediction of Agricultural Water Demand and Uncertainties Under Climate Change(Case Study: Wheat in Cities of Dezful and Andimeshk)

    , M.Sc. Thesis Sharif University of Technology Memarzadeh, Ali (Author) ; Abrishamchi, Ahmad (Supervisor)
    Abstract
    Climate change impacts especially on temperature and precipitation, may have various effects on agriculture and water demand of agriculture sector in different regions around the world. Based on numerous researches, these effects may be positive in a region while another region might endure negative effects. Therefore carrying out researches and developing methods to predict these impacts as well as mitigating strategies seem to be essential. The most worldwide accepted method is using global circulation models (GCMs) outputs under different greenhouse gases emission scenarios, and according to Intergovernmental Panel on Climate Change (IPCC) assessments. IPCC claims that the most recent... 

    Assessing the Ecological Potential of Tehran City Using Sustainable Urban Criteria

    , M.Sc. Thesis Sharif University of Technology Aghashahi, Nazli (Author) ; Abrishamchi, Ahmad (Supervisor)
    Abstract
    The citizens’ dissatisfaction with the decreased life and residential care quality is increasing as a result of the rapid growth and development of cities. To find an effective solution to reduce and control these harmful effects is one of the main concerns of urban managers and planners in most countries. In this research, various ecological and sustainability criteria were selected through library-based studies and relative recognition of the region. The Maps were mostly provided through satellite imagery and some by using synoptic data collected from the official aerology website of the country, Iran. Through surveying the experts, different criteria were evaluated and based on the... 

    Thermal attributes of sodium alginate (Na.C6H7O6) based binary and ternary hybrid nanofluids under activation energy and induced magnetic field environment

    , Article Case Studies in Thermal Engineering ; Volume 59 , 2024 ; 2214157X (ISSN) Li, S ; Leng, Y ; Atta, G ; Ahmad, S ; Ali, K ; Idris, S. A ; Ahmad, H ; Sharif University of Technology
    2024
    Abstract
    Ternary hybrid nanofluids possess several potential applications in the modern science beyond just the heat transfer efficiency. A continuous research and advancements on binary and ternary hybrid nanofluids might lead towards new developments in many technological and scientific zones. Ongoing research interprets and distinguishes the novel attributes of the sodium alginate (Na.C6H7O6) based unary, binary and ternary nanofluids through a porous medium under induced magnetic field environment. The nano-composition of single-wall carbon nanotubes (SWCNT) with silver (Ag) and molybdenum dioxide (MoS2) gives rise to the binary (SWCNT-Ag/Na.C6H7O6) and ternary hybrid (SWCNT-Ag-MoS2/Na.C6H7O6)... 

    A case study of different magnetic strength fields and thermal energy effects in vortex generation of Ag-TiO2 hybrid nanofluid flow

    , Article Case Studies in Thermal Engineering ; Volume 47 , 2023 ; 2214157X (ISSN) Kai, Y ; Ali, K ; Ahmad, S ; Ahmad, S ; Jamshed, W ; Raizah, Z ; El Din, S. M ; Sharif University of Technology
    Elsevier Ltd  2023
    Abstract
    Vortices grab the attention of many scientists while analyzing any flow model due to their importance in interpreting fluid mixing and mass transport phenomena. Since vortices exist in the natural environment, so researchers need to investigate them whenever they are encountered. Solar collectors, automobile cooling, engine applications, thermal management, and machine cutting, are just a few of the major areas in which most hybrid nanofluids could help to improve overall performance. The goal of this study is to demonstrate the highly complex dynamics of a Lorentz force, which governs the rotation of nanoparticles and the composition of the complex configuration of eddies inside the fluid... 

    Experimental research on the performance of lightweight concrete containing foam and expanded clay aggregate

    , Article Composites Part B: Engineering ; Volume 171 , 2019 , Pages 46-60 ; 13598368 (ISSN) Ahmad, M. R ; Chen, B ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    This work addresses the preparation of self-flowing lightweight aggregate foamed concrete (LAFC) resulting from the mixing of stable foam, expanded clay aggregate (ECA) and silica fume (SF) as main raw materials. Formulated LAFC mixtures were tested for the mechanical, thermal, sorption and high-temperature resistance properties. Results showed that the increase in the volume of foam from 0% to 20% considerably improved the flowability of LAFC and LAFC mixtures were categorized into high stable visual stability index. Compressive strength of LAFC mixtures was reduced from 24.75 MPa to 21.10, 15.95 and 12.05 MPa respectively when foam volume was increased from 0% to 10, 15 and 20%. Thermal... 

    An Analysis of Key Factors Contributing to Residential Property Valuation in Iran

    , M.Sc. Thesis Sharif University of Technology Naderi, Iman (Author) ; Sharbatoghlie, Ahmad (Supervisor)
    Abstract
    It is our purpose in this study to compare and analyze behavioral aspects of residential property valuation in Iran. More specifically, this research aims to explore the attributes that influence the value of residential property from the consumers’ and valuers’ perspective to determine whether valuers account for consumer behavior accurately. Finally, we investigate which variables operate at the lower end of the market, as distinct from those influencing the value of higher priced property. The core methodology underpinning the measurement of buyer and valuer behavior is the use of survey analysis. The identification of variables employing a two stage process forms an initial but critical... 

    Estimation of Springback in Sheet Metal Stamping Using Inverse Finite Element Method

    , M.Sc. Thesis Sharif University of Technology Marzban, Bahador (Author) ; Asempour, Ahmad (Supervisor)
    Abstract
    This work presents a quick method in estimation of spring back effect in sheet metal forming. In this method, the so called Inverse Finite Element Method (IFEM) has been adopted for compution of strains and also blank shape. Although the of element used is membrane, the effect of bending/ unbendiing is considered by addition of some extra forces as the bending forces to the nodal forces. The results of strain distribution obtained by IFEM are applied to another algorithm developed for computation of the spring back . this algorithm has been developed for the sections with plane starin assumption. Therefore, spring back of longitudinal parts, can be estimated by this method in a short time....