Sharif Digital Repository

Focusing on fossil fuel to secure energy demand lead to big challenges. Hydrogen as alternative for fossil fuel has attracted a lot of attentions. Fuel cell with an electrochemical reaction which it’s byproducts are water and heat convert Hydrogen into electricity. High efficiency and low environmental pollution, persuade many researchers toward fuel cell commercialization. But problems such as high cost, high power oscillation and inertia, avoid fuel cell from significant development. One way to deal with these problems is using the fuel cell and battery hybrid system. In recent decade too many research has been made in utilizing this hybrid system in transportation. This project... 

The need for service passenger cars, like taxies and governmental vehicles, to work in central Tehran that can produce less emission has been the main drive behind this research. A series and a parallel hybrid pneumatic vehicle based on Iran manufactured Samand Passenger car and different driving cycles were developed using commercially available components. The idea is to use as many standard parts as possible to reduce the development and manufacturing costs. The vehicle space, weight limitations and the fixed geometry have been the main constraints in components adoption. In addition, the dynamic performance of both series and parallel designed vehicles were evaluated with chosen... 

In this thesis, we consider the motion of a stretched string coupled with a rigid body at one end and we study the existence of periodic solution when a periodic force acts on the body. In this hybrid system, there is a weak dissipation that characterizes. The main difficulty of the study is related to the weak dissipation which does not ensure a uniform decay rate of the energy. In this thesis, firstly, under the condition of 0 1 0 , we prove there exists a periodic solution. Then, we change the conditions on , Indeed, we restrict ourselves to solve the problem. In this case, under the condition of 0 2 0 , we show there is a periodic solution for rational periods. In the last part, by... 

Nowadays, despite the special position of power electronic converters in the world, and the fact that they become an integral part of human life, still in the wake of a serious necessity the development process has not stopped and the increasingly fast pace, it opens up new horizons. This important necessity emerges from the environmental concerns regarding consumption of fossil fuels and their limited and imbalanced distribution which can be effectively addressed with the use renewable energy systems. By improving the quality of the semiconductor switches and offering new topologies in different functions as well as using new control methods, scholars try to develop enhanced converters in... 

A DC-DC quasi-resonant converter has the advantage of reducing switching losses and electromagnetic interference which are the main limitations of high frequency power converters. The conventional model of the quasi-resonant converter is derived using state space averaging followed by linearization about an operating point. Nevertheless, the state variables have large variations and the validity of the linearized averaged model is violated. Therefore it is essential to investigate the stability of quasi-resonant converter using a more precise model. Quasi-resonant converters are intrinsically hybrid systems consisting of discrete input and continuous states. In this paper the discrete... 

Solar power is a clean energy resource which has been known as an important renewable energy source; however, due to the high cost of installation and the need for energy storage systems in the absence of sunlight at night, it has not been used on a large scale till now. Using the combination of solar energy and biomass energy from agriculture and urban waste in a power plant may be regarded as a commercial option due to the removal of individual solar power energy storage costs. In this study, a hybrid solar-biomass power plant will be studied. Linear Fresnelin and parabolic through technologies in the solar section and combustion and gasification technologies were used in the biomass... 

World population is increasing with a rapid paste while the availability of freshwater is becoming more scared. There is a severe lack of fresh water in the world today. Desalination of seawater is one of the significant options in hand to solve this problem. In this research a hybrid solar collector- high efficiency water purification system is introduced which can help to solve this problem with an interesting economic outlook. Renewable energies and desalination plants are two different technologies, which can be combined in various ways. The interface between the renewable energy system and the desalination system is met at the place/subsystem where the energy generated by the renewable... 

Ever-increasing energy consumption and consequent extensive greenhouse gas (GHG) emissions are two major urgent problems faced by all human beings in the 21st century. As a major contributor, the energy production section appears to be the most suitable field where further improvements could be explored to tackle these problems. Multi carrier energy system is a typical type of next generation energy production technology with higher energy efficiency and lower/zero GHG emissions. The conversion of energy between different carriers establishes a coupling of the corresponding power flows resulting in system interactions. The investigation of such phenomena requires the development of tools for... 

Gas Metal Arc Welding (GMAW) process is one of the most applicable component in the industry due to its high speed and capability of employing for wide ranges of materials. The quality of products in a welding process is relevant to the quality of welding which is determined by characteristics like shape and size of droplet during detachment. In order to improve the quality of welding, a precise model of the process is required. There are many various model presented for GMAW process based on its dynamic equations. Almost all of these models assume the process as a continuous state system. However the process includes sudden variants in droplet detachment that is known as hybrid behavior.... 

Whenever continuous and discrete dynamics interact, hybrid systems arise. Basically, models of such systems consisted of differential or difference equations to represent continuous dynamics and automata or other discrete variables to describe behavioral mode of the systems. Our main concern is focused on two types of hybrid systems: Discrete controllers which are combined with continuous physical process like biological systems can often be well described by hybrid systems. Our approach in this thesis deals with optimal multiple daily insulin injections which are introduced as an offline control approach on a simulated patient with type I diabetes. Simulated patient is provided via GlucoSim...