Sharif Digital Repository

The main objective of this project is to take the first step in designing torsional vibration damper (TVD) for engines in Iran. To this end a complete dynamic model of a 4 cylinder internal combustion engine comprising of all reciprocating parts plus the crankshaft was developed using Bond Graph method. Real firing data of the engine was used as input to the system and output torque to gearbox shaft as the output. The system equations in two cases, with TVD and without TVD were derived. MATLAB software was used to solve these equations in finding the quality of performance of the torsional vibration damper. Dynamic properties of crankshaft and designed TVD were obtained using finite element... 

An important characteristic of sea waves is their high energy density, which is the highest among renewable energy sources. Many different types of wave-energy converters of various categories have been proposed yet. In this thesis the performance of a novel wave energy converter (WEC) is studied. The system, extracts the wave energy from heaving motion of a cylinder buoy in head seas. This heaving cylindrical floating buoy is tested with sinusoidal incident waves in a wave channel in marine engineering laboratory, Sharif University of Technology (SUT). The study begins with a thorough review on types of renewable energy and their application in Iran. Then an introduction to ocean wave,... 

Neutron fluctuations in both low and high power reactors provide important information about the system. The origins of these fluctuations are different in both regimes. In low power the branching process is the reason of these fluctuations. But the random nature of technological processes such as boiling in the reactors cooling and mechanical structure vibrating such as control rod and fuel rod created the neutron noise. Mathematical descriptions and applications of neutron noise for each mode are different. In common mode, fluctuations in the neutron detection system, determine some parameters and determin the start abnormality in system. In this study the spatial dependence of the cross... 

Torque variations caused by intermittent combustion and inertia effects of reciprocating components, exert significant torsional excitation on crankshaft of internal combustion engines. These excitation induces considerable torsional vibration on crankshafts. Therefore, modeling and analysis of crankshaft torsional vibration and absorber systems, especially in automobiles engine that crankshaft tolerate high amplitude excitations coupled with heavy inertia effects has high importance. In this study, ability of centrifugal pendulum vibration absorber and dual mass flywheel which used in rotating machinery for vibration reduction, will be examined. At first, cranktrain will be torsionaly... 

Stress Absorbing Membrane Interlayer (SAMI) is a slightly thin layer made of bitumen and aggregate placed between a pavement with limited cracking and overlay in order to avoid reflective cracking in overlay. SAMI’s performance depends on many factors such as pavement layer’s materials and thickness and existing pavement’s condition. Numerical simulations are powerful tools to evaluate SAMI’s performance. Previous studies showed that construction of SAMI does not necessarily reduce reflective cracking. This research investigated the effect of different parameters on SAMI’s performance using numerical simulations. The focus of this study was on the performance of SAMIs used between asphalt... 

Subwavelength metallic slit structures allow extraordinary transmission of light (EOT) at certein frequencies.In recent years, the effect of graphene layer on EOT has been investigated, which is used in the design of terahertz modulators. The electrostatic tuning ability of graphene electrical conductivity controls the resonance frequency and the amount of incident radiation absorption. Because of the single atomic thickness of graphene, the wide range control of incident light can not be achieved alone. However, by placing this layer with various 1-D and 2-D patterns on periodic metallic layers with EOT ability, high light modulations can be obtained. In particular, the structure of the... 

In this thesis Blackening of electroless nickel-phosphorous coating and the effect of TiO2 anti-reflection coating on optical properties of coating was investigated. In the first step, electroless nickel coatings with different amounts of phosphorous on 1050 aluminium substrate deposited. In second step, blackening of coatings by chemical and electroche-mical methods have studied and in final step, effect of TiO2 antireflection coatings with different amount of Pluronic F127 on the optimum black surface and properties of coating investigated. Chemical blackening performed in nitric acid and effect of acid concenteration, Blackening time and temperature studied. optimized condition was... 

One of the key issues in the operations of on orbit servicing to unmanned satellites is to provide a safe and reliable docking process. In this thesis, the dynamic behavior of a flexible probe in the central docking mechanism of unmanned satellites is investigated. For this purpose, first a dynamic analysis software has been applied to build a three dimensional model with the assumption of flexible clamped beam as a shock absorber, finally, the impact phenomone is simulated. therefore, in addition to solving a three-dimensional problem and studying the impact phenomenon between chaser and target satellite, it is possible to consider the parameters such as the type of connection between the... 

Cracks or construction joints in an overlayed pavement can propagate into the overlay over time due to various factors, the most important of which are traffic and temperature loading, and cause premature failure of pavement. This propagated cracks are called reflective cracks and the phenomenon of crack propagation into the overlay is called reflective cracking. Use of stress-absorbing membrane interlayers (SAMI) is one of the ways can reduce the occurrence of reflective cracking and/or delay it. One of the most common SAMIs is an asphalt mixture consists of bitumen and aggregate layed down between the old and the veneer layers. The function of the SAMI depends on several factors such as... 

The silencer is used to reduce sound in the vehicle, air conditioning channels, power plants and guns. Functional parameters of the sound amplifier are the amount of noise reduction and pressure drop. There are few studies on the flow and pressure distribution in the silencer, and there is no article about the effect of the size of the internal passages on the pressure drop and acoustical performance of the silencer. Few studies have been done on the effect of the absorbent fiber diameter on the acoustic performance of silencer. In this study, the effect of different shapes of internal channels (extended tubes, baffles and number of chambers) on the pressure drop and acoustic performance of... 

Optical bistability is one of the most important results of nonlinear optics. The term optical bistability refers to the situation in which two different output intensities are possible for a given input intensity. Interest in optical bistability stems from its potential usefulness as a switch for use in optical communication and in optical computing. Optical bistability is resulted by nonlinear phenomena such as kerr effect, two photon absorption and saturable absorber. In this thesis, we study the optical bistability in a double-coupler ring resonator, in which the right half of ring is made of an erbium doped fiber amplifier for compensating the loss by the gain of EDFA, and the left half... 

In this research, the first attempt was made to increase the thickness of the absorbent layer and increase the size of the absorbent layer crystals and minimize the cavities of this layer. this attempt resulted in the synthesis of absorbent layer with a thickness of about one micrometer and with low cavities. then, an attempt was made to crystallize the buffer layer and form the bond with the absorbent layer. these efforts led to the synthesis of a cadmium sulfide layer with a high carrier density. in this study, cadmium sulfide and cadmium zinc sulfide and indium sulfide were used to make the cell. then we could synthesizing window layer with low resistance.at end, we made superstrate... 

In this thesis the effects of vibro absorbing coating on vibration behavior of an aluminum sheet and also on a stiffened aluminum panel are investigated using experimental approach. Since there wasn't any information available about the used coating, to find its viscoelastic material properties, the method mentioned in ASTM E756-05 standard is employed and corresponding tests are performed.
In the next step, an analytical solution developed for the aluminum sheet with viscoelastic coating and the obtained results compared with experimentation, in order to find its prediction accuracy for loss in “loss factor” of the system in presence of coating.
To study the effect of... 

The aim of this work is numerical analysis of wave propagation in earth by using spectral element method for single and multi phase with application in oil industry. In this method, numerical solution has high accuracy due to using high order polynomials and appropriate integration points. Also, the mass matrix is diagonal by using this method which results in considerable decrease in computational cost with respect to finite element method.
The wave propagation in the mentioned models is studied by many researchers. The main problem in petroleum industry is large dimension of the model which results in high computational costs. Thus, using the proper numerical approach for these... 

We Consider the Chemotaxi Systems in a smooth bounded domain as follow:{ █(ut = Δu-χ∇.(u∇v)+ f (u) x ϵ Ω ,t>0 @ @τ vt =Δv-v+u x ϵ Ω ,t>0)┤ Where χ∈ and f(u) =Au - Buα generalizes the logistic function with A≥0, B>0 and α>1. First for τ=0, global existence of such solutions for any nonnegative initial data is proved under the assumption that . Moreover, boundedness properties of the constructed solutions are studied. Next we assume that 2=α, τ>0 and we consider nonnegative solutions of the Neumann
Boundary value problem for the chemotaxis system above in a smooth bounded convex domain . We will see that if B is sufficiently large then for all sufficiently smooth initial data the... 

In this dissertation, we design and simulate Electromagnetic (EM) wave absorbers using periodic array of ultra-thin metallic ribbons, metallic disks and graphene disks based on circuit theory. The equivalent circuit for EM structures significantly eliminates the requirement of systems with advanced hardwares. Firstly, we categorize the metallic absorbers in the literature in two types: narrowband absorbers and broadband absorbers. Surface plasmon polariton, magnetic resonance, interference theory and localized surface plasmon are employed to illustrate the mechanism behind the narrowband absorption. Therefore, they will be the basis for classifying the narrowband absorbers in this work.... 

The circular flexible cylindrical liquid tanks usually are made of steel or aluminum and in majority of cases are built on grade due to its economic advantages. The most important part of a safe design of a storage tanks is the accurate estimation of the seismically induced lateral forces that should be transferred to its base through the tank shell and its support. Seismic behavior of liquid storage tanks is quite different from regular buildings and industrial structures due to its nonlinear behavior caused by complex distribution of hydrodynamic pressure, buckling of its walls, etc.. Moreover, the effect of rocking motion caused by the under laying soft soil, on its response parameters... 

In this project, the feasibility of hydrocarbon waste water treatment with low concentration by physical- chemical treatment methods will be discussed. The purpose of this thesis is to investigate the feasibility of reusing the water outlet of the oil and gas refineries, in the region of ASALUYEH where there is an urgent need for water. By using activated carbon and wooden absorbent (absorption method) efficiency of this method was determined. Both coagulation and flocculation methods were investigated. To design and optimize various operating conditions on the adsorption process the RSM method was used. Temperature, residence time, feed concentration, amount of adsorbent, and adsorbent ... 

The aim of this project is analysis of fuselage vibration reduction on turboprop aircraft, by using passive methods. In this method by design and installation of tuned vibrant absorber (a system composed of mass and auxiliary spring) which its natural frequency is tuned, taking into account the excitation frequency of the vibrant fuselage body under harmonic force. And the motion of the point which is connected to it, would be ceased. Considering the place limitations and weight in the aircraft design, the designed absorber with respect to space and occupied volume shall be mountable on the aircraft frames and for maximum reduction of skin vibrations and eventually damping of acoustic energy...