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Design and Implementation of Bio-impedance Sensor Circuits
, M.Sc. Thesis Sharif University of Technology ; Sharifkhani, Mohammad (Supervisor)
Abstract
Heart failure is a chronic and significant disease that affects millions of people worldwide. Despite advances in medical technology and treatment options, heart failure remains a leading cause of death globally. This has led to a growing interest in developing new diagnostic tools and therapeutic strategies that can improve the control of this disease. One promising field is bioimpedance spectroscopy, which is a non-invasive method for measuring the electrical properties of biological tissues in the body. Monitoring the condition of fluid accumulation in the lungs of heart failure patients is effective in reducing the death rate caused by this disease. In this thesis, a portable device for...
Investigation of bed Stability in Downstream for the Diversion dam under Scour (Mill & Moghan case study)
, M.Sc. Thesis Sharif University of Technology ; Shamsai, Abolfazl (Supervisor)
Abstract
Numerical simulations and large eddy simulations (LES) of turbulent flow downstream of diversion dam , pool-riffle bedform in different geometrical ratios (different lengths of riffle and pool) with flow Reynolds number of 3.0 E+04 to 3.3E+04, downstream of special case study "Mill and Moghan diversion dam" with Froude number of 0.5 are presented The calculations are performed using a computational fluid dynamics model, FLOW-3D, which solves the Navier-Stokes equations in three dimensions with finite volume method. Numerical simulations are validated by comparing the numerical results of time-averaged flow patterns downstream of pool-riffle sequence with that of the experimental...
The Effect of Heat Treatment on Microsructure, Hot Tensile Properties and Creep Bihavior of Nickel-based Superalloy CM88Y
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
The Ni-base superalloy CM88Y has good hot corrosion resistance, high stability and strength at elevated temperature; accordingly, the alloy is used in manufacturing of gas turbine hot components. In most applications, heat treatment is required in order to achieve the desired mechanical properties and corrosion resistance of the working conditions; often three stages of heat treatment is designed for precipitation hardening nickel-base superalloy. In general, the effective parameters of heat treatment cycles includes temperature, time, heating rate and the cooling rate. In this study, the effect of cooling rate from partial solution temperature (second stage of heat treatment) on the...
Optimum kinetic and gas hold up distribution study in an NDMA hydrogenation reactor
, Article 18th International Congress of Chemical and Process Engineering, CHISA 2008, Prague, 24 August 2008 through 28 August 2008 ; 2008 ; Kazemeini, M ; Sharif University of Technology
2008
Abstract
Unsymmetrical Dimethyl hydrazine (UDMH) is used as stabilizer, fuel promoter, chemical in photography, and liquid fuel for fighter jet engines. Catalytic liquid phase hydrogenation of nitrosodimethylamine (NDMA) is one of the most efficient methods for the production of UDMH. Hydrogenation of NDMA to UDMH using a commercial 5% Pd/C catalyst in aqueous solution of NDMA was studied under constant temperature at 40°-70°C, ≤ 15 bar, and NDMA concentrations of 40-70 wt %. The effects of temperature, pressure, and NDMA concentration on NDMA conversion and yield of UDMH product in presence of undesired Dimethylamine (DMA) were studied. At NDMA concentration of > 50 wt %, the UDMH yield was < 0.89,...
X-Band Receiver Design in 0.15um GaAs
, M.Sc. Thesis Sharif University of Technology ; Medi, Ali (Supervisor)
Abstract
RF Receivers are one of the main components of telecommunication systems, which can be composed of many parts and circuits according to their working frequency and application.In this thesis, the design and simulation of an X-band Receiver in 0.15um GaAs technology has been discussed. The receiver chain, in the order of receiving the signal, includes the main blocks of limiter, attenuator, low noise amplifier and mixer. It also includes a number of filters. The attenuator has two digital bits and the receiving chain filters are implemented in such a way to provide more than 20dB attenuation in the frequency band of the image signal. In this research, the limiter is implemented with a...
Analysis of Group Formation in Social Networks Using Evolutionary Game Theory
, M.Sc. Thesis Sharif University of Technology ; Ramezanian, Rasoul (Supervisor)
Abstract
Evolutionary game theory is a relatively new branch of game theory (in contrast to the classical game theory) which has overcome some of the common problems of the classical version such as highly rational agents assumption. Because of this, it has gained popularity among different sciences. On the other hand, social network as one of the branches of complex networks is a pretty novel research area and has application in several fields. Networks are everywhere and most real-world networks are complex ones. Group formation and evolution are among important subjects in studying social networks and some works has been done in analyzing and modeling them. In this thesis we have presented a...
Preparation and Evaluation of Hydrophobic Pt Catalyst on Alumina and CNT to Produce Heavy Water Isotope
, M.Sc. Thesis Sharif University of Technology ; Kazemeini, Mohammad (Supervisor)
Abstract
Liquide phase catalytic exchange (LPCE) between liquid water and hydrogen is an important reaction for separation of the hydrogen isotope from liquid water. One of the application of this reaction is heavy water production. This method is mainly used hydrophobic catalysts with Pt active metal. The use of hydrophobic catalyst is necessary, because liquid water in the LPCE reaction, resulted in block the catalyst pores and loss of catalyst activity. Design of experiment has been done by using of Design Expert 7.0.0 for determination of number of tests and optimization of Pt weight percent. Alumina and carbon (included graphene, single-walled and multi-walled carbon nanotube) supported 5% wt Pt...
An experimental kinetic optimization of NDMA hydrogenation to UDMH and DMA on a Pd/C catalyst
, Article CHISA 2006 - 17th International Congress of Chemical and Process Engineering, Prague, 27 August 2006 through 31 August 2006 ; 2006 ; 8086059456 (ISBN); 9788086059457 (ISBN) ; Kazememi, M ; Bozorgmehri, R ; Sharif University of Technology
2006
Abstract
The Unsymmetrical dimethyl hydrazine (UDMH) apart from its use as a versatile rocket fuel, finds numerous industrial applications. Interest in UDMH for various applications in the missile and rocket industry has prompted the study of this member of hydrazine family to greater extent. It can be prepared in several ways but one of the most efficient ones which results in higher yields is the catalytic hydrogenation of Nitroso Dimethylamine (NDMA). In this work the kinetic of NDMA to UDMH hydrogenation on a 5% Pd/C in aqueous solution of NDMA was studied experimentally and optimum conditions of the reaction for maximum yield of UDMH in the presence of undesired dimethyl amine (DMA) product was...
Kinetic investigation of NDMA to UDMH hydrogenation on a pd/C catalyst
, Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 30, Issue 5 , 2006 , Pages 581-593 ; 03601307 (ISSN) ; Kazemeini, M ; Bozorgmehri, R ; Sharif University of Technology
2006
Abstract
Unsymmetrical dimethyl hydrazine (UDMH) is a strong propellant, which due to its very good physical properties and high power of repellency has been utilized as a liquid fuel for fighter jet engines for so many years. There are different methods for production of this material. One of the more efficient ones which results in higher yields compared to others is the catalytic hydrogenation of Nitroso Dimethylamine (NDMA). In this work hydrogenation of NDMA to UDMH on a 5% Pd/C in aqueous solution of NDMA was studied experimentally. Experiments were carried out in a Semi-batch three phase STR reactor under constant pressure and temperature in the range of 40 to 70°C, pressures of up to 15 bar...
Modeling the instability behavior of thin film devices: Fermi Level Pinning
, Article Superlattices and Microstructures ; Volume 117 , 2018 , Pages 399-405 ; 07496036 (ISSN) ; Ahmadpour, M ; Gorji, N. E ; Sharif University of Technology
Academic Press
2018
Abstract
We investigate the underlying physics of degradation/recovery of a metal/n-CdTe Schottcky junction under reverse or forward bias stressing conditions. We used Sah-Noyce-Shockley (SNS) theory to investigate if the swept of Fermi level pinning at different levels (under forward/reverse bias) is the origin of change in current-voltage characteristics of the device. This theory is based on Shockley-Read-Hall recombination within the depletion width and takes into account the interface defect levels. Fermi Level Pinning theory was primarily introduced by Ponpon and developed to thin film solar cells by Dharmadasa's group in Sheffield University-UK. The theory suggests that Fermi level pinning at...
CFD modeling of gas-liquid hydrodynamics in a stirred tank reactor
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 26, Issue 2 , 2007 , Pages 85-96 ; 10219986 (ISSN) ; Bozorgmehry Bozzarjomehry, R ; Kazemeini, M ; Sharif University of Technology
2007
Abstract
Multiphase impeller stirred tank reactors enhance mixing of reacting species used in a variety of chemical industries. These reactors have been studied based on Computational Fluid Dynamics (CFD) that can be used in the analysis, design and scale up of these reactors. Most of the researches done in this area are limited to single phase reactors, and a few remaining two phase flow investigations have been done based on MRF (Multi Reference Frame) and Snapshot approach. However, the MRF and snapshot approaches cannot be used in rigorous simulation of unsteady state problems. In order to simulate the unsteady state behavior of the multiphase stirred tank reactors we have used sliding mesh...
A three dimensional CFD modeling of hydrodynamics and mass transfer in a gas-liquid impeller stirred tank reactor
, Article CHISA 2006 - 17th International Congress of Chemical and Process Engineering, Prague, 27 August 2006 through 31 August 2006 ; 2006 ; 8086059456 (ISBN); 9788086059457 (ISBN) ; Bozorgmehry Boozarjomehry, R ; Kazemeini, M ; Sharif University of Technology
2006
Abstract
Multiphase impeller stirred tank reactors enhance mixing of reacting species used in a variety of chemical industries. Gas-liquid mixing and mass transfer between these phases is an important application in reactor design. One such an example is hydrogenation reaction of aqueous NDMA (Nitroso dimethyl amine) solution in which one of the parameters having a significant effect on the reaction rate is mass transfer. This parameter in turn is a function of impeller shape and rotational speed, gas flow rate and reactor scale. Computational Fluid Dynamics (CFD) is a useful tool in the analysis, design and scale up of stirred tank reactors via investigating hydrodynamics of gas and liquid flow,...
Development of composite silver/nickel nanopastes for low temperature Joining of yttria-stabilized zirconia to stainless steels
, Article Ceramics International ; Volume 41, Issue 1 , January , 2015 , Pages 1815-1822 ; 02728842 (ISSN) ; Simchi, A ; Kokabi, A. H ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Joining of yttria-stabilized zirconia (YSZ) to stainless steels is considered for various applications such as solid oxide fuel cells, thermal barrier coatings, and medical implants. In the present work, a series of brazing pastes utilizing silver and nickel nanoparticles (∼80 nm) mixed with carboxymethyl cellulose as the organic phase were developed to join 5 mol% YSZ to AISI 420 steel. Effects of processing parameters including time and temperature of brazing and the composition of the nanopastes on the microstructure of joints and their shear rupture strength were studied. Elaboration of the joining mechanism by scanning electron microscopy and electron probe micro-analyzer showed...
Optimizing the materials response in humidity capacitive sensors
, Article Journal of Nano- and Electronic Physics ; Volume 7, Issue 3 , October , 2015 ; 20776772 (ISSN) ; Golnabi, H ; Gorji, N. E ; Sharif University of Technology
Sumy State University
2015
Abstract
The number of humidity outputs on the cap of a cylindrical capacitance sensor is optimized by designing three different probes with direct and indirect windows. The time interval is measured within which 30- 70 % humidity can influence the dielectric constant and conductivity of the capacitance when exposed to a range of relative humidity. It is then compared with a simple set-up including a simplified equivalent circuit. The direct probes had four and double outputs on the window of the cylindrical capacitive sensor while the indirect probe had a thin plastic layer only. We observed that the dielectric constant and its conductivity depend closely to the humidity outgoing pathway and also to...
Modeling of J sc and V oc versus the grain size in CdTe, CZTS and Perovskite thin film solar cells
, Article Superlattices and Microstructures ; Volume 128 , 2019 , Pages 421-427 ; 07496036 (ISSN) ; Pourasiab Dizaj, H ; Gorji, N. E ; Sharif University of Technology
Academic Press
2019
Abstract
A modeling approach is presented for the first time to model the dependence of short-circuit current density (J sc ) and open-circuit voltage (V oc ) on the grain size g in three thin film solar cells including the emerging perovskites. The variation of J sc and V oc with the grain size (g) of three different solar cells with CdTe, CZTS and perovskite absorber layers are modelled and fitted with the experimental dataset collected from relevant literature. The experimental literature suggested that the grain size of absorber layers in solar cells is controlled during the deposition process by adjusting the growth rate, temperature and ambient. The model has been successfully applied to the...
H2O based different nanofluids with unsteady condition and an external magnetic field on permeable channel heat transfer
, Article International Journal of Hydrogen Energy ; Volume 42, Issue 34 , 2017 , Pages 22005-22014 ; 03603199 (ISSN) ; Rahimi Gorji, M ; Pourmehran, O ; Domairry, G ; Sharif University of Technology
2017
Abstract
This paper investigates numerically the problem of unsteady magnetohydrodynamic nanofluid flow and heat transfer between parallel plates due to the normal motion of the porous upper plate. The governing equations are solved via the fourth-order Runge-Kutta method. Different kind of nanoparticles is examined. The effects of kind of nanoparticle, nanofluid volume fraction, expansion ratio, Hartmann number, Reynolds number on velocity and temperature profiles are considered. Also effect of different types of nanoparticles is examined. Results indicate that velocity decreases with increase of Hartmann number due to effect of Lorentz forces. Rate of heat transfer increase with increase of...
Random data and key generation evaluation of some commercial tokens and smart cards
, Article 2014 11th International ISC Conference on Information Security and Cryptology, ISCISC 2014 ; 2014 , p. 49-54 ; Sarmadi, S. B ; Yousefi, P ; Gorji, P ; Jalili, R ; Sharif University of Technology
2014
Abstract
In this paper, we report our evaluation of the strength of random number generator and RSA key-pair generator of some commercially available constrained hardware modules, i.e., tokens and smart cards. That was motivated after recent related attacks to RSA public keys, which are generated by constrained network devices and smart cards, and turned out to be insecure due to low-quality randomness. Those attacks are mostly computing pair-wise GCD between the moduli in public keys, and resulted in breaking several thousands of these keys. Our results show that most of the tested hardware modules behave well. However, some have abnormal or weak random generators which seem to be unsuitable for...
A simplified model for the flow inside cascade impactor
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 7 A , November , 2013 ; 9780791856314 (ISBN) ; Sohrabi, S ; Falsafi, P ; Gorji, P ; ASME ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2013
Abstract
In this paper we developed a new mathematical model for the flow inside cascade impactors and via this simplified model, we determined the particle size distribution by a fast and low cost computational method. Using cascade impactors for determining the particle size distribution, one can use comprehensive CFD methods to fully simulate the particle traces. Although the results from those CFD analyses can be very accurate, usually that is not a time and cost efficient routine. In contrast, we showed that by using our proposed calculation we can estimate the particle size distribution very fast and yet with the slight error -comparing to the results from CFD method. Cascade impactors are...
Experimental investigation of a supercritical airfoil boundary layer in pitching motion
, Article Journal of Mechanical Science and Technology ; Volume 31, Issue 1 , 2017 , Pages 189-196 ; 1738494X (ISSN) ; Jahanmiri, M ; Soltani, M. R ; Tabrizian, A ; Gorji, M ; Sharif University of Technology
Korean Society of Mechanical Engineers
2017
Abstract
In this study, the boundary layer velocity profile on the upper surface of a supercritical airfoil in a forced sinusoidal pitching motion was measured and experimentally investigated. Measurements were performed using a boundary layer rake, including total pressure tubes positioned at 25 % of the chord far from the leading edge on the upper surface. For static measurements, the effects of the angle of attack between −3° and 14° and free-stream velocity between 40 m/s and 70 m/s were investigated; for dynamic measurements, the effects of oscillation amplitude variation between ±3° and ±10°, reduced frequency from 0.007 to 0.0313, and mean angle of attack between −3° and 6° were studied during...
Modeling the detection efficiency in photodetectors with temperature-dependent mobility and carrier lifetime
, Article Superlattices and Microstructures ; Volume 122 , 2018 , Pages 557-562 ; 07496036 (ISSN) ; Ahmadpour, M ; Mosavi, A ; Alharbi, N ; Gorji, N. E ; Sharif University of Technology
2018
Abstract
We proposed a modeling procedure to calculate the impact of temperature on the detection efficiency in photodetectors based on CdTe materials. Temperature increase impacts on the electrical properties of the materials such as carrier mobility and carrier recombination lifetime. This impact which can be effective in some cases has been normally ignored in the modeling approaches presented in the literature. Here we show that increasing the temperature from 190 K to 300 K not reduces the mobility of both electrons and holes but also significantly reduces the carrier lifetime. The result will impact on electric-field within the depletion width of the device, drift and diffusion lengths which...