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Design and Analysis of Hot Gas Diffuser for High Altitude Simulation
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor) ; Fooladi, Nematollah (Co-Advisor)
Abstract
In order to test the performance of engines used at high altitudes, a vacuum simulator system is used. In the vacuum test stand the supersonic exhaust diffuser is used to create the vacuum conditions and the automatic discharge of combustion gases into the atmosphere. usually, the exhaust gas temperature of the engine nozzle is much higher than the temperature that steel body of diffuser can stand (above 2500 K). The purpose of this study is to design and analyze a cooling system to protect the diffusers body. In this study, first by comparing different cooling methods, a spray-cooled water treatment method has been selected for the problem. A new algorithm for designing a spray cooling...
Design and analysis of a cooling system for a supersonic exhaust diffuser
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 233, Issue 14 , 2019 , Pages 5253-5263 ; 09544100 (ISSN) ; Fouladi, N ; Mirbabaei, A. R ; Sharif University of Technology
SAGE Publications Ltd
2019
Abstract
High-altitude test facilities are usually used to evaluate the performance of space mission engines. The supersonic exhaust diffuser, a main part of high-altitude test facility, provides the required test cell vacuum conditions by self-pumping the nozzle exhaust gases to the atmosphere. However, the plume temperature is often much higher than the temperature the diffuser structure is able to withstand, usually above 2500 K. In this study, an efficient cooling system is designed and analyzed to resolve the thermal problem. A water spray cooling technique is preferred among various existing techniques. Here, a new algorithm is developed for a spray cooling system for a supersonic exhaust...
Performance evaluation of a second throat exhaust diffuser with a thrust optimized parabolic nozzle
, Article Aerospace Science and Technology ; Volume 94 , 2019 ; 12709638 (ISSN) ; Farahani, M ; Mirbabaei, A. R ; Sharif University of Technology
Elsevier Masson SAS
2019
Abstract
In the present study, the experimental analysis of a second-throat exhaust diffuser (STED) performance has been conducted for the high altitude test of a parabolic bell-type nozzle. The diffuser starting performance has been explored considering two different approaches, namely the gradual and instantaneous increase of the nozzle chamber pressure. Also, the influence of pre-evacuating the internal regions of the system on the diffuser starting performance has been studied. Numerical simulations have been carried out to have more physical insight into some test results. It is demonstrated that the non-dimensional hysteresis range in STED starting performance with a bell-type nozzle is up to 4...
Scattering Theory on Locally symmetric Spaces
, M.Sc. Thesis Sharif University of Technology ; Razvan, Mohammad Reza (Supervisor)
Abstract
Scattering theory on locally symmetric space first was studied by Peter Lax and Ralph Phillips. They studied the and develop scattering theory on it. Without the Fourier analysis tools this theory was completed with a lot of computations. In this thesis first we try to construct Fourier analysis by definition Fourier transform then by means of new tools we prove very short version of scattering theory on locally symmetric space . In general case for studying scattering theory we need firs spectral decomposition of Hilbert space of square integrable functions locally symmetric spaces of rational rank one is achieved by quotient of symmetric space where G is Lie group and K is maximal...
Analysis and Improvement of QoS in Optical CDMA Networks Using Cross Layer Design Concepts
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor)
Abstract
According to the rapid growing in communication devices, users need higher rates for their usages. Fiber optics is one the major choices to support such rates. One of the simplest and cheapest networks is Local Area Network (LAN) as a Passive Optical Network (PON). In these networks, some computers are locally connected to a passive optical device and communicate through it. Multiple access to a shared channel is an important task in such a network. In this thesis, Code Division Multiple Access (CDMA) is used and a new algorithm for Multiple Access Control Sublayer (MAC) based on scheduling will be developed to improve Quality of Service (QoS) and stabilize the network.
In the scheduling...
In the scheduling...
Developing an Applied Model for Energy Management in Dairy Production Industry
, M.Sc. Thesis Sharif University of Technology ; Mokhtar, Ali Reza (Supervisor) ; Miremadi, Ali Reza (Supervisor)
Abstract
Reviewing trends of energy consumption in the world reveals that sooner or later energy resources will be depleted. This concerning rate of consumption has brought about more greenhouse gases (GHG) emission influencing deleteriously on environment and climate. Human has continued energy consumption to maintain and improve the quality of his life through industrial production. Industry as a significant energy user owns considerable contribution to this consumption. Several attempts have been carried out to develop energy management systems in order to improve the energy efficiency of industrial sectors. Whilst they are comprehensive and could be applied to any sector, there is lack of...
Formability analysis of Tailor Welded Blank Pridaction with Friction Stret Weld
, M.Sc. Thesis Sharif University of Technology ; Asempour, Ahmad (Supervisor) ; Naghdabadi, Reza (Supervisor)
Abstract
The Tilor welded blank (TWB) two or more sheets with different thickness or strength which are welded together. The automobile designer are searching for new methods to reduce the cars’ weight and producing cost in order to diminish fuel consumption so they can survive in the competitive market. One way to achieve to this seemingly Contradictory demands, is using TWB in cars’ body. One of the most applicable methods to investigate the formability of metals sheets, is Forming Limit Diagrams (FLD). Three ways to determine the FLD are: Analytical Method, Experimental Methods, and Numerical Method. The experimental method to determine FLD, require metal sheets to undergo in different strain...
Comparing the Performance of Centrifuge, Membrane Filter and Filter Press for Clarification of Lipase Enzyme
, M.Sc. Thesis Sharif University of Technology ; Rousta Azad, Reza (Supervisor)
Abstract
Lipases (Triacyl Glycerol Acyl Hydrolase, EC.3.1.1.3) are multidimensional biocatalysts which have many applications in food industrials, dairy, fats and oils processing, detergents, synthesis of pure chemical and pharmaceutical materials, paper industrial and cosmetics. Generally, industrial enzymes are produced extracellularly, so their separation from a low-cost complex medium (usually used for production) is one of the cost stages in their production process. Filtration is the most economical method of separation in the production of enzymes, but due to the small size of colloidal particles and cell masses present in the fermentation environment, its use is subject to limitations. In...
Fluid Suspended Films in Present of Electric Field and Voltage
, Ph.D. Dissertation Sharif University of Technology ; Amjadi, Ahmad (Supervisor) ; Ejtehadi, Mohammad Reza ($item.subfieldsMap.e)
Abstract
Scientists want to know how they can control fluids motion. They use electric fields for controlling the fluids in different dimensions. In small size, application of electric fields is very important because of biological applications. We use electric current and field for rotating freely suspended films. Here, we study soap, polar and non-polar liquids, MBBA liquid crystal and ferrofluids films. We show that the surface charge plays the crucial role in rotating the films.We study the correlation between rotation of a film and different physical quantities.Our experiments confirm that dipole moments of fluid molecules do not show a clear effect on the rotation. Increasing the dipole moment...
Stabilization of the Finite element Analysis of the Fluid-Structure Interaction in Micro Systems in Small Time Steps
, Ph.D. Dissertation Sharif University of Technology ; Movahhedy, Mohammad Reza (Supervisor) ; Assempour, Ahmad (Supervisor)
Abstract
Fluid-structure interaction plays an important role in the performance of various Microsystems. In many micro-devices such as micropumps, microvalves and micromixers, the fluid flow is driven by a vibrating solid membrane. Since the fluid also plays a role in resistance to the solid vibration and deformation, the solid vibration and the fluid flow are always coupled and a full fluid-structure interaction (FSI) analysis is required in order to investigate the performance characteristics of these devices. Since the frequency of the solid vibration is normally high in micro-devices, the time step size required for the finite element analysis of the fluid-structure interaction in these devices...
A Fuzzy Multi-Criteria Approach to Sustainable Development Case Study of Hendurabi Island in Iran
,
Ph.D. Dissertation
Sharif University of Technology
;
Abrishamchi, Ahmad
(Supervisor)
;
Maknoon, Reza
(Co-Supervisor)
Abstract
The main objective of this research is to provide a framework by which decision-makers can evaluate and compare alternatives for sustainable development planning under uncertain dynamic future considering the risk and uncertainty associated with human judgment as well as the uncertain future. This approach combines the Delphi method, fuzzy set theory, and a discrete multi-criteria method based on prospect theory (TODIM). TODIM (an acronym in Portuguese for iterative MCDM) method is a particular multi-criteria approach based on the prospect theory. A qualitative Delphi technique is used to identify a set of qualitative sustainability criteria and to rate the alternatives accordingly. The...
Fabrication and Characterization of Porous Carbon-Graphene Composite as an Absorbent for Industrial Pollutants
, Ph.D. Dissertation Sharif University of Technology ; Madaah Hosseini, Hamid Reza (Supervisor) ; Pourjavadi, Ali (Supervisor) ; Bahramian, Ahmad Reza (Co-Supervisor)
Abstract
The amount of fresh water suitable for various uses is decreasing day by day. This may be due to evaporation or contamination of water or such. Heavy metal cations, dyes, oils and solvents are the most important substances that contaminate water. There are various ways to remove these contaminants, one of which is the absorption of these substances by suitable absorbents. Carbon compounds have attracted much attention among all the absorbents used so far. The aim of this study is to produce carbon aerogels from an economic and modify its structure and properties by adding graphene nanosheets. In this study, Novalak-graphene oxide (GO) gel was fabricated using solvent-saturated vapor...
Human Capital Development and Utilization Methodology in a Public Sector Organization: Dynamic Capability Approach
, M.Sc. Thesis Sharif University of Technology ; Kermanshah, Ali (Supervisor) ; Sanjari, Ahmad Reza (Supervisor)
Abstract
It is proposed, in this research, a methodology for a public sector organization to integrate policy making in human capital development and utilization area. In this case the researcher used system dynamics method for modeling and analyzing the situation, to describe the mechanisms that produce the difficulties in the organization. The researcher mentioned the differences between public sector and profit organization, in designing the main part of the model and also the use of dynamic capability approach in designing human capital development parts of it. The model built in this research, describe the events before and after the 1990s separately, according to the different policy making...
Optimal Asset Allocation with Hidden Markov Regime Switching
,
M.Sc. Thesis
Sharif University of Technology
;
Bahramgiri, Mohsen
(Supervisor)
;
Jalali Naeni, Ahmad Reza
(Supervisor)
Abstract
Asset allocation is one of the core economic functions of security markets. By purchasing and selling securities individuals are able to effectively time their stream of consumption and to allocate their temporarily unused wealth among competing investments. To time the stream of future consumption optimally, the question arises as to how wealth is allocated most effciently on security markets. The purpose of this thesis is to develop an optimal Asset Allocation with Hidden Markov Regime Switching means and volatilities. We use the historical weekly information of three Indices in Wallstreet stock exchange: Stock, bond and commodity. First we use these historical information from...
Improvement and Expansion of Characteristic Green’s Function-Complex Images Method for Extraction of Green’s Function of Finite Dielectric Structures
, Ph.D. Dissertation Sharif University of Technology ; Shishegar, Amir Ahmad (Supervisor) ; Faraji-Dana, Reza (Co-Advisor)
Abstract
Finite dielctric structures are commonly used in optical devices, Microwave Integrated Circuitc (MICs) and printed antennas. To analyze these structures, full-wave analysis methods cannot be employed easily. They need huge computer resources and are time-consuming especially for electrically large structures. On the other hand, asymptotic techniques may not be exact enough for these structures. In this thesis, MPIE technique is chosen as an accurate and efficient technique for analyzing these structres. To use this technique, the magnetic vector potential and electric scalar potential are required. Uniform and closed-form spatial Green's function for finite dielectric structures is...
Simulation of GTL Process Slurry Bubble Column Reactor Using CFD Methods
, Ph.D. Dissertation Sharif University of Technology ; Bozorgmehri, Ramin (Supervisor) ; Pishvaie, Mahmoud Reza (Supervisor) ; Tavassoli, Ahmad (Co-Advisor)
Abstract
In this thesis non-ideal behavior of fluids and its effects on hydrodynamic and mass transfer in multiphase flow is studied. A numerical framework has been proposed to model the interacting effects of mixture non-ideality and mass transfer on hydrodynamics of a multiphase system using CFD methods. Using the numerical framework mass and momentum transfer in a system was simulated. The system consists of a cylindrical vessel filled with vapor and liquid hydrocarbons which selected as the benchmark. The liquid hydrocarbon is chosen to be pure Octane and the hydrocarbon in the gas phase is assumed to be Propane. Due to operating condition (T=323 K, P =445 kpa) the behavior of fluid is non-ideal...
Preparation of Biodegradeble Nanocomposite with Appropriate Physical and Mechanical Properties for Bread Packaging
, M.Sc. Thesis Sharif University of Technology ; Ramezani Saadat, Ahmad (Supervisor) ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
Platelet nanoparticles could dramatically decrease permeability of polymeric film where increase considerably its physical -mechanical properties. Bio based (Biodegradable) polymeric materials such as starch based polymeric films show very weak mechanical and high oxygen and water vapor permeability. Graphene oxide (GO) could increase mechanical properties of starch based polymer where decrease its permeability dramatically. Addition of chitosan also could increase antibacterial and antifungal of films and decrease permeability of films considerably. In this research nanocomposite of Starch/Chitosan/GO films have been prepared by solution method and its morphology, permeability, physical...
Effect of tiO_2 Nanoparticles on Heat and Drag Properties of Dilute Polymer Solutions
, M.Sc. Thesis Sharif University of Technology ; Ramezani Saadat Abadi, Ahmad (Supervisor) ; Mohammadi, Mohammad Reza ($item.subfieldsMap.e)
Abstract
In the present work, the experiments were carried out for two types of PAM (3330 and 3630) with three distinct concentrations (25, 40 and 55 ppm) and TiO_2-water nanofluid for four concentrations (1.5, 2, 2.5 and 3 vol. %), and the Nusselt number and friction factor for each of them expressed separately. The Reynolds number was in the range from 11000 to 21000. The steady state turbulent convective heat transfer and friction factor of the combination of TiO_2-water nanofluid and polymer 3330 in the coiled tube were investigated. The effects of the Reynolds number for 2 vol. % nanoparticles which consists of 25 ppm PAM (3330) determined at the constant temperature of 24°C. It was observed...
Cosmology with Polarization of Gravitational Waves
, M.Sc. Thesis Sharif University of Technology ; Baghram, Shant (Supervisor) ; Mansouri, Reza (Supervisor)
Abstract
the gravitational wave (GW) which is a prediction of General Relativity has entered a new era after being detected by Ligo observatory in 2015. new discoveries are still being made. the discovery of GW is a new opportunity for studying gravity, astrophysical sources of GWs like binary black-holes or binry neutron stars as well as testing cosmology models.on the other hand, it should be mentioned that the astronomy of gravitational waves is in its dawn stage. in future having numerous precise detectors and by accumulation of data, speaking about exact phenomena and statistical analysis will become meaningful. as in the case of cosmic microwave background physics, in which researchers started...
Manufacture of Smart Drug Delivery System with UCST Polymers
, M.Sc. Thesis Sharif University of Technology ; 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...