Sharif Digital Repository

All supersonic intakes with external compression, having a good level of performance at all the critical poin t. Exhibit a marked instability of flow in subcritical operation below some value of the flow ratio, in the form of an oscillation of the shock system, colloquially known as “buzz", which can lead to thrust loss, engine surge or even structural damages. Therefore the effort to understand the nature and cause of this phenomenon is important in order that the starting of buzz can be predicted and more effectively avoided without losing performance. This phenomenon has been the subject of many studies, mainly experimental. In this research, we design and build an axisymmetric supersonic... 

In this research, mathematical modeling, deriving equations of motion, solving equations and analyzing the response of motion vibrations of a moving mass with constant speed on a sandwich beam have been discussed. The sandwich beam consists of three layers, the middle layer of which is made of viscoelastic material, and the upper and lower layers are the Euler-Bernoulli beam model.At first, this sandwich beam is mathematically modeled, This mathematical modeling includes all the specifications of the system to obtain the equations that govern the behavior of the system. Then, the displacement field of the system has been extracted and the equations of motion of the system have been obtained... 

Vision-based localization and 3D orientation estimation of a moving camera, has been for long a vast research area including robot localization and mapping, virtual reality and structure from motion. By introduction of RGB-D cameras in 2010, many sparse methods which are based on key-point extraction and tracking, moved towards dense methods. Dense methods utilize the RGB-D depth and gray-scale values in the images and define the odometry estimation problem as an image registration optimization, without the need to make key-point correspondance in images. Although RGB-D cameras impose specific constraints such as limited depth, depth errors and medium resolution, dense methods have shown... 

In this thesis, the performance of a special type of controllers, called Proportional-Integral weighted (PIw) controllers, in control of nonlinear systems is studied. To this aim, the domain of attraction of polynomial nonlinear control systems in the presence of PIw and Proportional-Integral (PI) controllers is estimated and compared with each other. For this estimation, two different methods are used, and the obtained results are compared. Next, adaptive PIw and adaptive PI controllers are designed to be used in control of nonlinear systems. The effectiveness of the proposed controllers is illustrated for a Continuous-Stirred-Tank-Reactor (CSTR) that has an uncertain parameter in its... 

Electric power is considered as one of the prerequisites of development in many countries. In recent years distributed electric power generation has attracted much attention. Small hydro potentials are considered as the most economical method of harvesting renewable energy and a suitable solution for earning income.In the last two years, a project was defined for Sharif University of Technology by Iran hydro-power authorities with the goal of spotting hydro potentials and design, manufacture and installation of three types of micro hydro powerplants for the first time in Iran. One of these powerplants use a micro Cross-Flow turbine. Although the prototype manufactured for this project is a... 

In this thesis a novel non-rotating space tethered configuration is introduced which its relative positions are controlled using electromagnetic forces. The attitude dynamics is controlled by three reaction wheels in the body axes. The nonlinear coupled orbital dynamics of a dumbbell tethered satellite formation flight are derived through a constrained Lagrangian approach. These equations are presented in the leader satellite orbital frame. The advantage of using equations in the Cartesian coordinate system over presenting the equations of satellite formation plane angles is the appearance of gravity gradient and Earth’s magnetic field effects. The tether is assumed to be mass-less and... 

Particle separation has a variety of applications in biology, chemistry and industry. Among them, circulating tumor cells (CTCs) separation has drawn significant attention to itself due to its high impact on both cancer diagnosis and therapeutics. In recent years, there has been growing interest in using inertial microfluidics to separate micro/nano particles based on their sizes. This technique offers label-free, high throughput, and efficient separation and can be easily fabricated. However, further improvements are needed for potential clinical applications. In this study, a novel inertial separation technique using spiral microchannel with stair-like cross section is introduced. The... 

One of the most common methods for determining elastic moduli of rocks and porosity is acoustic velocity log. The elastic moduli of reservoir rock are widely used in geomechanical modelling, borehole stability and hydraulic fracture design. Carbonate oil reservoirs are known for heterogeneity and anisotropic nature. Therefore correlation of acoustic velocity and rock properties are generally challenging. Rock’s shear modulus is very important during saturating of sample with pore fluid because assumed it is independent of pore fluid type. However due to the several fluid-solid interaction mechanisms such as velocity dispersion, surface energy reduction and viscous coupling, shear modulus... 

Micropumps are regarded as one of the devices used in microsystems, which are responsible for pumping working fluid. The Mercury Magneto Reciprocating (MMR) micropump, which has been introduced for less than a decade, is an innovative kind of micropumps which the pumping agent includes three liquid metal droplets (LMD) placed inside lateral chambers and reciprocated by the electromagnetic force inside the chambers. The working fluid located inside the main channel is pumped through due to the movement of these three LMDs. The equations governing this micropump are complex and their numerical solution is a time-consuming process, due to electromagnetic, hydrodynamic, and unsteady effects. The... 

Aerodynamics loads and aeroheating during reentry, are one of the challenging issues in designing One of the main challenges in the design and application of reusable spacecrafts is the aerodynamic and thermal loads acting on their structures during reentry into the atmosphere. For this reason, all the concepts/prototypes presented in the 20th century were either not fully reusable, or were partially canceled, or did not have economic justification. In this report, the aerodynamic loads on the first stage of a launch vehicle during the launch and return phases have been investigated. Due to the fact that the main part of the first stage of the vehicle includes fuel and oxidizer tanks, the...