Loading...
Search for:
ghasemi-fard--ali
0.162 seconds
Total 2893 records
New S-norm and T-norm Operators for ALM
, M.Sc. Thesis Sharif University of Technology ; Bagheri Shouraki, Saeed (Supervisor)
Abstract
Active Learning Method (ALM) is a soft computing methodology which has been used for modeling and control. Unlike the good results of ALM’s ability, there is not any analytic expression to prove its power, because ALM’s main operators don’t satisfy fuzzy S-norm & T-norm properties. This problem considered from three viewpoints: Mathematics, Geometry and fuzzy sets. In this paper, we try to introduce two new operators based on morphology to satisfy three conditions: at first, they must be fuzzy S-norm and T-norm to confirm the committal of fuzzy set theory. Secondly, they must satisfy Demorgans law, because they are complement of each other. And finally, they resemble the main operators of...
Mechanical Properties of Al2O3-ZrO2 Nanocomposites Fabricated by Gelcasting
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor)
Abstract
Gelcasting is a new ceramic forming technique getting worldwide attention. The process is based on casting of slurry; containing powder, water and water-soluble organic monomers. The premix solution was prepared using Acrylamide as a monomer and Methylene bisacrylamide as a crosslinker with AM:MBAM ratio of 25:1, and Poly Acrylic Acid Sodium as a dispersant (1 wt% based on ceramic powders weight). A series of Al2O3/ZrO2 ceramic nanocomposites with 15, 17.5 and 20 wt% content of ZrO2 and 40, 43, 45, 47, 50, 53 and 55 vol.% of solid loading were fabricated by gelcasting. After casting the mixture, the monomer was polymerized to form gel parts. Drying, burning out and sintering completed the...
Flow-Field Modeling and Performance Prediction of Axial-Flow Compressors using Streamline Curvature Method
, M.Sc. Thesis Sharif University of Technology ; Ghofrani, Mohammad Bagher (Supervisor) ; Nouri Borujerdi, Ali (Supervisor)
Abstract
Compressors are one of the most important components of gas turbines and turbomachinery processes. Thus some precise and quick tools are needed for design and analysis purposes. Despite of vast development of Computational Fluid Dynamics (CFD) tools, Through-Flow Streamline Curvature Methods (SCM) has retained their position. 2D and quasi-3D forms of SCM in combination with CFD results nowadays make more than 80% of turbomachinery design process of axial and radial compressors and turbines. In this thesis, the basics of developing a tool for axial-flow compressor analysis are introduced. As will be seen, this analysis tool can be used for design purposes too. The method that is chosen for...
Seismic Behavior of Concentric Steel Braced Frames In Near Fault Ground Motion
, M.Sc. Thesis Sharif University of Technology ; Golafshani, Ali Akbar (Supervisor)
Abstract
The use of braced frames has become more popular in seismic design of buildings because of the simplicity in design and construction. The first event that occurs in the earthquake for a concentrically brace frame (CBF), is the buckling of the strut. The inelastic behavior of CBF systems is dominated by brace buckling, yielding and the post buckling behavior. The Inelastic performance of the brace is nonsymmetrical, because of the difference in the tensile and compressive strength of the brace and the deterioration in the resistance after buckling. so we have too complexity in modeling the inelastic performance of brace members. Also the subject of the near fault ground motion and design of...
An Integrated Formal Method for Specification and Verification of Component-Based Systems
, Ph.D. Dissertation Sharif University of Technology ; Movaghar Rahimabadi, Ali (Supervisor)
Abstract
This thesis presents an integrated formal method for modeling and model checking of component based computing systems. Both components and coordination subsystems are modeled by a variant of standard labeled transition systems called record transition systems. A record transition system is a labeled transition system whose transition labels are records. We use records to model the concurrency of input – output operations in the ports of the system. The concurrency of the executions with respect to common transition labels are modeled by standard parallel composition operator and also a new defined operator called join which is analogous to the join operator defined to compose constraint...
Numerical Simulation of Turbulent Flow Heat Transfer in the Entrance Region of Microchannels
, M.Sc. Thesis Sharif University of Technology ; Nouri Borujerdi, Ali (Supervisor)
Abstract
In this thesis the steady state convective heat transfer for turbulent, two-dimensional, incompressible gas flow in a circular microchannel under slip flow and temperature jump conditions is numerically investigated by means of finite volume scheme. The low Reynolds number k-ε turbulence model is employed using a new boundary condition for turbulent kinetic energy at solid surface. To calculate variables at control volume surfaces in the axial direction upwind differencing scheme and in the radial direction central differencing scheme are used. Rhie-Chow interpolation technique is used to prevent pressure field oscillations. The set of discrete equations are solved using SIMPLE Algorithm. In...
Toughening of Laminated Composites Composites Using Micro and Nano Particles
,
M.Sc. Thesis
Sharif University of Technology
;
Koochakzadeh, Mohammad Ali
(Supervisor)
Abstract
In this study, standard composite laminate specimens with micro and nano sized particle additives are made to study the effect of the additives on the fracture toughness of the specimens in standard tests. The composite laminates are made from epoxy resin and unidirectional glass fibers. The mode I and mode II fracture toughness of the specimens are measured under various loadings in standard tests. The fracture surface is then, fractogaphed by microscopic instruments. In conclusion, the fracture behavior of laminated composites, toughened by micro and nano particles is discussed. The results show that using rubber particles will improve fracture toughness of neat epoxy resin and laminated...
Theoretical and Experimental Investigation of Losses in Twin-Entry Radial Inflow Gas Turbine under Full and Partial Admission Conditions
,
Ph.D. Dissertation
Sharif University of Technology
;
Rad, Manoucher
(Supervisor)
;
Hajilouy Benisi, Ali
(Supervisor)
Abstract
The twin-entry radial inflow gas turbine is extensively used in engine turbochargers. The use of twin-entry radial flow turbine in the turbocharging systems makes it possible to use the kinetic energy of pulsating exhaust gases. This turbine is usually exposed to partial admission conditions in engine operating conditions, which the flows in each inlet are not equal for most of the time. This partial admission varies from zero flow in one entry with full admission in the other, to full flow in both entries. The flow pattern in this turbine is complex and three dimensional due to geometry and inlet conditions. Therefore, better understanding of the flow pattern and losses in the turbine can...
Axial Flow Compressor's Optimization
, M.Sc. Thesis Sharif University of Technology ; Hajilouy Benisi, Ali (Supervisor)
Abstract
Improvement of axial flow compressor is usually goal of manufacturers of these equipments. Because basic role of it in gas turbine efficiency too many researchers have effort to know phenomenon and effect of them on axial flow compressor's revenue and optimization of them. In this project the aerodynamic of axial flow compressor studied and effect of important parameters such as diffusion factor coefficient, optimum incidence angel and Mach and Reynolds number determined from text and papers. Then obtained a model from experimental data to determine shock loss and extended algorithms to specify critical Mach number and chocking mass flow. With quotation Craig and Cox method we determined a...
Design and Manufacturing of a Propulsion Engine Thrust Forces Digital Test Stand in 3-DOF
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor) ; Saeedi, Mohammad Hassan (Supervisor) ; Mozaffari, Ali Asghar (Supervisor)
Abstract
Measurements of magnitude and direction of thrust generated by a propulsion engine is important for verification of design, fabrication, assembely and or repare procedure used for a engine. Due to possible simplification in design calculations, human and machine errors in manufacturing process, the resulted thrust generated may be different from those values expected. Also, It is important to determine the dependency of magnitude and direction of thrust forces relative to tolerances and manufacturing processes. It is necessary to have thrust measuring stand with high accuracy with capability to measure the forces in different directions. A new digital engine test stand has been designed,...
Bioactivity of Surface Modified Titanium Alloy Ti-6Al-4V ELI by Pack Siliconizing in Simulated Body Fluid
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor) ; Ziaei Moayyed, Ali Akbar (Supervisor)
Abstract
Titanium alloy Ti-6Al-4V ELI with high biocompatibility and corrosion resistance, has a lot of applications in biomedical engineering. Disadvantage of this alloy is it’s disability to create a fast and good contact with the host/bone environment, after implanting in the body. Beside that it has low wear resistance. Nowadays to optimize the wear resistance, bioactivity and osteoconduction of surface of implants which are made from this alloy, the surface morphology are optimized in size and distribution. Different surface treatments are used for producing rough and porous surfaces to improve bioactivity along with wear resistance. In this study, surface modification of Ti-6Al-4V ELI was done...
Evaluation of the Friction Dampers Effect on Seismic Retrofit of Non-ductile Concrete Structures
, M.Sc. Thesis Sharif University of Technology ; Golafshani, Ali Akbar (Supervisor)
Abstract
Iran plateau is situated over the Alpide-Himalaya earthquake belt. Tectonic studies indicate that this plateau has a very high density of active and recent faults; as a result, Iran is at risk of damaging earthquakes. Experience of past severe earthquakes shows previous designed structures do not have enough strength instead of real earthquake forces, therefore vulnerability study of existing structures and give a technical and economical retrofitting plan of them is required. Conventional methods of seismic rehabilitation for example using concrete shear walls or steel braces are not suitable for some buildings. Nowadays, passive control systems have been successfully used for reducing the...
Investigation the Effect of Process Parameters on the Synthesis of Nanometric Yttrium Aluminum Garnet Powder via Sol-Gel Combustion Method
, M.Sc. Thesis Sharif University of Technology ; Maddah Hosseini, Hamid Reza (Supervisor) ; Nemati, Ziarat Ali (Supervisor)
Abstract
Yttrium Aluminum Garnet powders possessing controlled size distribution has found applications in production of transparent ceramics, phosphors, laser host materials and composites. Sol-Gel Combustion process is one of the versatile methods to produce nanometeric garnet powders. This procedure is based on combustion of a concentrated gel of metal salts and fuel in an exothermic reaction which leads to nanoparticles formation. pH value of solution and employed fuel system strongly affect production quality and single phase nanopowder can be synthesized by well monitoring these parameters. In this study nanocrystalline Yttrium Aluminum Garnet powders was Synthesized via sol-gel combustion...
Modeling of Yield Behavior of Rubber Modified Epoxies
, M.Sc. Thesis Sharif University of Technology ; Kuchakzadeh, Mohammad Ali (Supervisor)
Abstract
Because of increasing usage of modified polymers and consequent necessity for investigation and modeling of mechanical behavior of these materials, it is important to get a yield criterion for these materials. For this purpose the Gurson yield criterion presented for porous metals, was modified with regard to mechanical properties of polymers. Indeed pressure sensitivity of polymers and their large elastic strain during deformation, makes using of Gurson yield criterion problematic for modified polymers.
For modification of Gurson criterion, macroscopic hydrostatic yield stress equation was derived for a thick-walled spherical shell of epoxy and then Gurson criterion was modified with...
For modification of Gurson criterion, macroscopic hydrostatic yield stress equation was derived for a thick-walled spherical shell of epoxy and then Gurson criterion was modified with...
Friction Stir Welding of Commercially Purity Titanium and its Effect on Microstructure and Mechanical Properties using Different FSW Tools
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor)
Abstract
The objective of this investigation was obtaining sound Friction Stir Welded (FSWed) Commercially Purity Titanium using suitable Tool’s Materials (for Shoulder and Pin) in order to be able to work in high temperature (>1000 ˚C) with great mechanical properties and minimum wear during process. Consequently, different materials and designs for Tool, such as High Speed Steel tool, Tungsten based tool, Tungsten Carbide (WC-Co) based tool and diverse tool geometry and designs like simple design, threaded design, fixed pin and inserted pin (adjustable pin) was used. The results demonstrated that using simple cylindrical WC-Co for pin and Tungsten for shoulder resulted in joints with the best...
Determination of Eddy Current Losses in Power Transformer Tank and Analysis of Methods for Reduction of These Losses
, M.Sc. Thesis Sharif University of Technology ; Abbaspour Tehranifard, Ali (Supervisor) ; Vakilian, Mehdi (Supervisor)
Abstract
The leads with heavy current passing through the covering plates, and the winding in a transformer, are sources of eddy current losses. Due to this loss some regions of tank wall are subject to serious local overheating. It affects the safety and reliability of this expensive bject and power delivery.Heavy current in large power transformers and special type transformers give rise to a concentrated passage of eddy currents which in turn cause high local losses and overheating in the metallic parts especially in the steel tank walls of transformer.This local overheating is dangerous for transformer oil and the solid insulations. Therefore the calculation of losses and proper design of...
Experimental Study on Two-Phase Flow Characteristics in Micro-Channels
, M.Sc. Thesis Sharif University of Technology ; Nouri, Ali (Supervisor)
Abstract
The present study provids an experimental investigation on two-pase flow characteristics in microchannels. Experiment were conducted with a mixture of air and water in horizontal circular pyrex channel with 400µm inner diameter. The pressure drop and flow rates of the liquid and gas were measured using new method and images of the flow patterns recorded by high shutter speed camera. The gas and liquid superficial velocity ranges were 0.025-12.5m/s and 0.016-3.6m/s, respectively. The flow pattern map is developed from the observed flow patterns based on phases superficial velocity as wel as We numbers of liquid and gas phases. The flow pattern map is compared with those of larger channels....
Application Microarray Technology in Infectious Diseases
, M.Sc. Thesis Sharif University of Technology ; Mahdavi-Amiri, Nezameddin (Supervisor) ; Karami, Ali (Co-Advisor)
Abstract
DNA microarrays consist of DNA microscopic points that are attached to a solid surface such as glass, plastic or silicon chip and formed as an array. The fixed pieces of DNA are considered as searchers. In an experiment, we can use thousands of searchers. Therefore, any microarray consists of the same number of genetic tests as the experiment performed on all of them in parallel. Whit this ability, arrays have speeded up the biological investigations. Microarray technology can be seen as a continued development of southern blotting. However, the most important stage in this technology, analysis of data, requires reliable bioinformatics tools achieving high reliabilities. Infectious diseases,...
Bearing Capacity and Settlement Analysis of Intermediate Foundation (Short Rammed Aggregate Piers)
, M.Sc. Thesis Sharif University of Technology ; Pak, Ali (Supervisor)
Abstract
Using short rammed aggregate piers (RAP) is one of the ground improvement methods that is suitable for loose sands and soft clays. In this method, gravel or crushed stone is placed in layers with specific thickness in a pre-drilled cavity and each layer is fully compacted with impacts of a hammer. The basic advantages of these piers are increasing soil lateral stresses due to aggregate ramming and increasing the consolidation rate due to high permeability of aggregates. The main application of RAPs is soil improvement underneath shallow foundations, in order to increase the bearing capacity and reduce settlement of foundation. Regarding the usual height of 1.5 to 5m of these piers, a...
Numerical Analysis of Stresses and Steady State Creep Strain Rates Fields of a Short Fibre Composite
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
A finite difference technique is developed to predict the second stage creep displacement rates and stress analysis of a short fiber metal matrix composite subjecting to a constant axial load. The exponential law is adopted to describe the matrix creep behavior. Also, a method for prediction of interfacial debonding at fiber/matrix interface is developed using a stress based method. The obtained results could greatly help to better understand the flow pattern of matrix material and the load transfer mechanism between fiber and matrix. The stress components and strain rates are also validated by the available FEM and experimental results