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TED Large Signal Modeling in the Dominant Mode
, M.Sc. Thesis Sharif University of Technology ; Farzaneh, Forouhar (Supervisor)
Abstract
Transferred Electron Device is a semiconductor device being capable of generating oscillation in microwave frequencies. Applying a bias voltage to the device and putting it in a resonant circuit, a periodic waveform in the output current is observed. The cause of the generation of oscillation in the device is related to the characteristics of velocity-field in the device. In some part of the characteristics, it is observed that increasing the field inside the device causes the velocity of electrons to be reduced. This causes the generation of the negative conductance and the oscillation of the output current under some conditions. The purpose of this thesis is to represent an equivalent...
Hydrodynamic Investigation of Large Drops and Their Breakage In Liquid Liquid Packed Beds
, M.Sc. Thesis Sharif University of Technology ; Safekordi, Ali Akbar (Supervisor)
Abstract
packed columns are important in liquid-liquid extraction processes. In most studies, at first, drops are broken to small drops as much as possible and then they contact with packings. But, because of different reasons drops during their moving up coalescence together. So far, there is not serious investigation about hydrodynamics of these large drops and their breakage in packed columns. Thus, breakage of two different sizes of drops while collision to 3 different height of 4 different type of packings with two volumetric flow rates and in 2 cases of straight collision of drops to bed and collision to support plate has been investigated. Then size distribution of produced drops throughout...
Modeling of Small Drones with a Wingspan of Less than 3 Meters and an Operating Speed of Less than 60 Kilometers Per Hour
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohammad (Supervisor) ; Doodman Tipi, Alireza (Co-Supervisor)
Abstract
Over the past two decades, the production of ultra-light drones has increased dramatically. These aircraft are used in applications such as filming, surveying, etc. One of the most important goals is to fly them for a long time. From time immemorial, a lot of work has been done to get such birds to fly, but nothing has ever been done on their engines and propellers, and they have always been considered ideal models (in other words, their efficiency is a bit ideal). In this dissertation, the main purpose is to study some of these sets and to obtain the flight time of a particular drone. First, a low-velocity wind tunnel was built to examine these complexes, then we tested these complexes...