Sharif Digital Repository

Fixation devices and implants are the most applied devices in orthopedic operation and dentistry. Interference screw is one of these devices that is made by biodegradable nanocomposite polymeric materials in this project. The purpose of this project is designing interference screw, applicable to body, and doing related tests since in vivo tests. For this purpose, hand injection molding, was designed to prepare screws in laboratory scale, first. For making samples, poly(D,L) lacticacid, nano hydroxyapatite as reinforce and polyethylene glycol as plasticizer were used. These samples were made by combination of solvent casting and melt processing methods. Adding nano hydroxyapatite and... 

In this thesis, the potential flow including unsteady partial cavitation around axisymmetric bodies are studied using a boundary element method (BEM) based on potential theory. For this purpose the wetted surface of the body and cavity surface are divided (approximated) to panels. Then, by applying the Green’s third identity and expressing this theory in potential flow around every surface, cavitation can be modeled by distributing the source and the dipole rings on cavity/body surface. In order to approaching this goal we introduced dipole rings distribution on the cavity and body surfaces and source rings distribution on the cavity surface. In this work the cavitation number is assumed to... 

Nowadays, vertical take-off and landing (VTOL) UAVs are widely used in various commercial and military applications due to its high flying capabilities. RMIT VTOL is a special design of this family. This bird has a small size and low weight and along with the vertical takeoff and landing capabilities, it also has the ability to fly at high speed Cruise.
The overall objective of this project is to design and evaluate the efficiency of the proposed three control methods that are linear, predictive and adaptive on the dynamic model of this bird. Thus, the first part of the project is obtaining a dynamic model with sufficient detail for the dedicated bird. This model consists of different... 

The goal of this thesis is the development and application of the finite volume method (FVM) with a same solution procedure in the fluid and structure domains for the simulation of fluid-structure interaction (FSI) problems in the compressible fluid flow. The unsteady Euler equations written in the arbitrary Lagrangian–Eulerian (ALE) form are considered as the governing equations of the compressible fluid flow and the moderate/large nonlinear deformation of the elastic structure is considered to be governed by the Cauchy equations in the Lagrangian/total Lagrangian forms. Therefore, the nonlinear phenomena in the unsteady compressible fluid flow and the large deformation of the elastic... 

In the present study, an incompressible smoothed particle hydrodynamics method based on vorticity-stream function (VSF-SPH) formulation is developed and assessed for simulating steady and unsteady incompressible flows. The vorticity-stream function formulation in the Eulerian reference frame is written in a Lagrangian reference frame to provide an appropriate incompressible SPH algorithm. The advantage of the proposed smoothed particle hydrodynamics method based on the vorticity-stream function (VSF-SPH) formulation over the weakly compressible SPH (WCSPH) is that the VSF-SPH method is a truly incompressible SPH algorithm and it does not involve any approximate enforcement of the... 

In recent years, Rheological behavior and heat transfer of nanofluid studies have been increasing considerably and results show significant progress in this area. In this study we analyze the laboratory examination of the influence of parameters of volume fraction and temperature on thermal conductivity coefficient, dynamic viscosity of new and useful nanofluid carbon nanotube in engine oil. Most of fluid comparing to solid has lower thermal conductivity coefficient therefore solid particles increase thermal conductivity coefficient. On the other hand by adding particles, the dynamic viscosity of nanofluid also increases. Since nanoparticles have high volume ratio to surface (SSA) they have... 

In the current study, shape-memory alloys are analysed analytically under mechanical loading. Due to the special properties of these materials, their usage in various applications is rapidly increasing. However, mostly, the numerical methods such as finite-elements methods are employed to model the thermo-mechanical behavior of these materials. Also, due to the complexity of their behavior, there are few analytical solutions for them in the literature. In this research, an analytical approach is proposed to investigate the response of these materials under mechanical loading using a fundamental model which is suitable for modelling their crystalline structure. Given the impact of multiple... 

Given the increasing concerns about climate change and the depletion of fossil fuel resources, the use of renewable energy as a sustainable and environmentally friendly solution has gained significant importance. This study examines a building that utilizes solar and geothermal energy to meet its heating and cooling needs. The system is analyzed from energy, exergy, and economic perspectives. Initial system design results showed that chilled water at 7°C and hot water at 59.13°C are produced. Among the three types of collectors examined, the thermal photovoltaic collector was selected for its simultaneous electricity and heat production and optimal efficiency for combination with an... 

In the present study, the numerical simulation of incompressible laminar and turbulent flows using a high-order finite difference lattice Boltzmann method is presented. To handle curved geometries with non uniform grids, the incompressible form of lattice Boltzmann equation is transformed into the generalized curvilinear coordinates and the spatial derivatives of the resulting equation are discretized using the fifth-order WENO scheme. The advantage of using the WENO-LBM developed is that it needs less number of grid points and remains stable even at high Reynolds number flows. For the temporal term, the fourth-order explicit Rung-Kutta scheme is adopted for laminar flow calculations and... 

Peer-to-peer streaming has developed as a popular application in today’s Internetinfrastructure. In a typical peer-to-peer live streaming system, publishers provide the streaming content and the interested peers receive and deliver data in a distributed manner and also apeer structure is created by forming an overlay inside the network. In reality, peers are strategic and there is no motivation to contribute any of their upload bandwidth toward other peers. To address this issue, we proposed a simple arcade algorithm that makes an arcade based mechanism for peers to facilitate adjacent peers with more bandwidth to achieve a higher bandwidth themselves.Commensurate with our algorithm, if... 

In this research a copper- diamond nanocomposite coating prepared by electrodeposition from a sulfate bath in order to increase the hardness and erosion resistance of cooper without disturbing cooper's specific physical properties as like as electrical and thermal conductivity. The mechanism of electrodeposition was analyzed with the technique of Cyclic Voltammetry, Chronopotentiometry and Chronoamperometry. The morphology, hardness, scratch resistance, elastic modulus and friction factor of coating were investigated by using a scanning electron microscope (SEM) and atomic force microscope(AFM) also the mechanism of co- deposition of diamond particles with copper was corresponded with... 

The steering system is very important in controlling the car. This requires to turning wheels at certain angles. These angles ideally follow the Ackerman geometry. But there is a difference between the real steering angle and the ideal geometry, which caused to steering error. This error depends on two factors, the steering mechanism and the vehicle suspension. Reducing steering error causes to reducing tire wear and increasing vehicle maneuverability at low speeds. In addition, the stability of the vehicle increases when crossing straight line and uneven roads. So far, mechanisms have been designed in accordance with the Ackerman geometry, but in these mechanisms used cam profile. Also... 

In this thesis, hemodynamic parameters of flow and deposition of low density lipoproteins (LDL) on wall of coronary arteries with taking into account their curvature on the heart are studied. At first, numerical solution of the blood flow by assumption of blood as incompressible and Newtonian fluid for steady and pulsatile inlet is done. Then by assuming LDL particles as dilute solute in the blood, LDL transport from artery lumen into arterial wall is studied. LDL accumulation and penetration into the vessel wall cause thickening of the walls and eventually eclipse it and its known as the first stage of atherosclerosis disease. The results show that low shear region occurs on inner wall... 

Nowadays, one of the most important desires of the human being is to reduce his living environmental pollution. Using the diluted combustion systems in new gas turbines in order to produce the minimum amount of has been done to satisfy this desire. It should be noted that reducing this amount and using the lower flame temperature will result in some consequences. The most important problem occurred in industrial and aerial gas turbines are the instability of the combustion due to dilution of the fuel to air mixture which it results in heat release fluctuations. If the heat release fluctuations and acoustic pressure are in the same phases, the amplitude of the fluctuations will increase which... 

In recent years, requirement to increase projectile performance, leads to a great interest in high angle of attack Aerodynamics. Projectile Maneuverability is a concept which is defined by having the capability to perform at high angles of attack while maintaining attached flow over the tail, rather than a capability of performing a mission in minimum possible duration. Interaction between body, wing and tail vortices can delay vortex breakdown over the wing and as a result may enhance projectile maneuverability. Studies show that wing aspect ratio and tail location have a remarkable influence on the vortices interaction and thus projectile maneuverability. In the present study, a series of... 

Throughout history, the occurrence of natural disasters and incidents has posed a potential threat to man-made constructions. Advancements in science and technology have led to the development of man-made civil infrastructures, which now exhibit increased complexity in terms of technological sophistication and spatial coverage. Consequently, monitoring and managing their health and risk factors have become more intricate. Urban lifelines, which encompass constructed utilities, transportation systems, telecommunication networks, and critical facilities, hold significant importance for the well-being of citizens. These infrastructure assets are essential for the distribution and flow of... 

Given the increasing importance of renewable energy and the environmental challenges posed by fossil fuels, this study primarily focuses on optimizing the use of solar energy and determining appropriate policies to increase investment in this sector. Residential buildings are among the major energy consumers, and given the available space on their rooftops, they provide a suitable location for the use of solar technology. Even when investors have the necessary financial resources, they prefer not to invest in this sector. This indicates an investment gap that government incentives could potentially bridge. However, previous government policies have failed to attract investors to this energy... 

The production of agricultural products is one of the most important human economic activities. The issue of mechanized and optimal use of pesticides is vital for human health and the environment, and the use of helicopters makes this possible. Although spray-based systems in helicopters are one of the most effective ways to produce agricultural products, it is still unclear how droplet movement in aerial spraying is affected by the complex downwash flow created by rotors. Modeling agricultural air spray to identify the spray trend of droplets in the air stream, downwash flows, and consequent vortices has attracted more attention as a result of the development of computational fluid...