Sharif Digital Repository

Three-phase electronic loads are used to test the performance of various electrical devices such as power supplies, generators, and transformers. Conventional electronic loads are composed of passive components that consume the energy, so have low power density and efficiency and to manage the produced heat, massive cooling systems are required. Nowadays, to increase efficiency and power density, three-phase regenerative electronic AC loads have been developed. To return energy to the grid and control the input power factor, the structure of these loads is based on back-to-back converters. In this project, a 35 kVA three-phase regenerative electronic AC load is designed. To control the power... 

Programmable AC Power Supply is a part of any Grid Simulator. Grid simulator is a system that, as a voltage source, can produce various power grid voltage waveforms in the output, and as a load, can draw different currents of ordinary loads from the power grid. The application of Grid Simulators is testing many grid connected systems, such as chargers, power supplies, PV inverters and etc. The purpose of this thesis is to design and build a 3 kW Programmable AC power supply, which can be used as a part of a grid simulator in future works. In this thesis, back to back converter topology is used for implementation of the programmable AC power supply. This back to back converter consists of an... 

In the present study, design and manufacturing of a connected pipe liquid fuel ramjet test platform is implemented for performance investigation of a research liquid fuel ramjet burner in the thermodynamic flight conditions. Design and manufacturing of platform systems include: the hot air supply system, the liquid fuel system and the square cross-sectional combustion chamber with the v-gutter shape flame holder. In order to determine the performance range of subsystems, calibration process has been carried out. Calibration process of the hot air supply system includes: determining of the burner inlet velocity and temperature. Also, calibration of the liquid fuel system includes: determining... 

With the increase of electric energy demand, one of the human concerns is to create the infrastructure for the production and transmission of energy in order to meet this need. Since the network must have the ability to supply the load during the peak load times, practically during the non-peak load times, many production capacities remain unused and their productivity decreases. One of the ways to reduce this problem due to the increase in penetration of batteries in the network can be the participation of battery banks to inject power into the network during peak load times. The goal of this project is to develop an 8 kilowatt-hour battery bank system that can inject 2 kilowatts of power... 

Renewable energy sources have significantly used in recent years and the associated technologies have been widely developed. Grid connection of most renewable technologies, such as photovoltaic and wind turbine, is accomplished using power electronic converters. Control of injected active and reactive power as well as current and frequency control of is, so, implemented through the power converter. Inverter is among the equipments widely used for grid connection The purpose of this project was to design and develop an inverter for grid connection of renewable generation technologies for laboratory use. The inverter is aimed to control both injected active and reactive power. A full-bridge... 

In recent years Photovoltaic Panels (PV) are very wide spread. Due to AC working mode of many consumers produce DC voltage of PV must be converted to AC voltage by inverters. Nowdays one of the most popular inverter topologies are grid connected transformerless inverters. The main task of transformer is galvanic isolation of PV from grid. These transformers are commonly work with grid frequency i.e 50 Hz, and consequently are bulky, heavy and expensive. Transformer elimination results in common mode leakage current from parasitic capacitors of PV cells and its grounded frame to the grid ground, that will cause in EMI and malfunction of earth fault relays.
In this thesis the factors of... 

Recently a new topology, namely “common ground inverter” is introduced which since it enjoys a direct connection between AC neutral and DC ground, essentially solves the problem of leakage current in grid connected applications. Moreover, a reduced implementation price and a simple control scheme is associated with this system. The Aforementioned features have absorbed a lot of attention for further research regarding this topology. In this research one of the three introduced topologies is considered in details and its function in supplying local loads and Grid is put to the test. Moreover, important efforts have been taken to improve the properties of the inverter in terms of efficiency,... 

In the present study an air supply system of a connected-pipe ramjet test facility for liquid fuel ramjet engine in theoretical and numerical base designed and optimized that the purpose is for performance test of a ramjet engine combustor in flight condition. The flight condition gained from previous assessment that is 1.5 kg air in 10 bars and 550 K. Air supply subsystems consist of air tanks, compressors, valves, regulators, preheater, and fuel and oxygen systems that are designed in a preliminary process and then valves, orifices, and fuel and oxygen systems optimized by HYSYS program. In the last step preheater that is a gas turbine combustor investigated and possible changes made by... 

In addition to improving on current services, future mobile networks will need to support new services types. Two of the envisioned services are enhanced mobile broadband (eMBB) and ultra-reliable low-latency communication. The unprecedented requirements of the new services are out of the reach of current networks, moreover, the diverse characteristics of the new services poses great challenges to the network designers. One of these challenges is designing an efficient resource allocation algorithm that effectively deals with different timescales that the URLLC and eMBB services operate at. A promising enabling technology is multi-connectivity. Multi connectivity is defined as using spatial... 

One of the critical challenges in droplet based micro- and nanofluidic devices is handling the droplet breakup such that a controllable droplet size is produced. The experimental and numerical investigations at the microscale indicate that the droplet size can be well controlled by T junction geometries. In the present study we use non-equilibrium molecular dynamics (NEMD) simulations to investigate this phenomenon at the nanoscale. In order to generalize the study the Lennard-Jones type potential between the fluids and the walls have been considered and the strength and the effective range of the potential are changed to consider a wide variety of materials. Our results reveal that the... 

In order to ensure the safety of the plants, a set of commissioning tests based on international standards for nuclear power plants is carried out before operation. In this research, one of the Bushehr power plant commissioning tests, the loop connection primary circuit cooling pump test, was simulated using the RELAP5 code. In this test, the effects of loop connection primary circuit pumps on the thermohydraulic parameters and the eneterance of test-related systems was evaluated. After simulating the systems related to the test and extracting the results of the stable state, were evaluated the transient results was obtained with the experimental results of the test of loop connection the... 

According to prediction of ITRS, power consumption and bandwidth of processors' interconnection, will be the most major bottleneck of the System-on- Chips (SoCs) in the future. Therefore, in MultiProcessor System-on-Chip (MPSoC) architectures, the design constraints will be altered from "Computational Constraints" to "Communicational Constraints". There are three kinds of communications in the surface of the chip: Global, median and local. The main difference between global and local connections is that the length of latter one will be changed with technology. In other words, it is scalable like processor's elements while the length of global connections is practically constant. Even though... 

A data transmission network constitutes of finite number of data processing stations which are connected together through data transmission lines. Each data transmission network corresponds to a graph which is called network’s graph. Obviously there are meaningful relations between structural properties of network’s graph and efficiency of network. In this thesis we investigate two aspects of network’s graph. The first subject is Cayley graphs. It has been shown that Cayley graphs are good models for designing data transmission networks. In this thesis we have surveyed some structural properties of Cayley graphs. The second subject is isoperimetric number. The isoperimetric number is a good... 

The process of contracting the chips will lead the increasing of impurity concentration, decreasing the bias voltage and threshold voltage to make stable the electrical field. For using the advantage of lesser dimensions of the total circuit using decreasing bias voltage lead the dimension of the wires to be decrease also. Therefore, once the parasitic effects of wires, the RC delays of wires and the noise of power transmission will enhance obviously. With this contracting by process, electrical resistance of interconnect will enhance also. The reason of this matter is that the area chip will decrease significantly. While the operational frequency increases the effect of inductance should be... 

The spectrum of a graph is related to many important combinatorial parameters. Let (G), ′(G) be the maximum number of edge-disjoint spanning trees and edge-connectivity of a graph G,respectively. Motivated by a question of Seymour on the relationship between eigenvalues of a graph G and bounds of (G), we use eigenvalue interlacing for quotient matrix associated to graph to get the relationship between eigenvalues of a graph and bounds of (G) and ′(G). We also study the relationship between eigenvalues and bounds of (G) and ′(G) in a multigraph G. In the first chapter we prove eigenvalue interlacing and give several applications of it for obtaining bounds for characteristic numbers of... 

Graph Theory and Combinatorial Analysis like the other branches of science use the probability for solving their problems. At the first , we will introduce the most common tools from probability used in Discrete Mathematics, such as “The Lovasz Local Lemma”. Most of them are based on Linearity of Expectation, Concentration Theorems and some other innovative methods such as Deletation Method. We will present different examples for these techniques. Also we will introduce “Random Graphs” and their importance. Specially we will explain how to use “Threshold Functions” to obtain different properties about the majority of graphs. Rainbow Connection, is a natural and interesting quantifiable way... 

In this thesis, coordination of a group of autonomous agents, through a scalable control structure and with very limited communications, is addressed. Inter-agent action functions are designed to guarantee the network connectivity. Two coordinator agents with different natures are designed. One is attractive and is named leader-agent (LA). The other is repulsive and is named shepherd-agent (SA). Under the assumption that both coordinators locally affect the group, we have proved that the governing equation of the whole group may have variable order.
By using nonlinear control techniques, coordination algorithms are designed to move the group on a predefined path or to a destination. It... 

In this thesis we study Manin’s proof of Mordel conjecture for function fields in characteristic 0 and restate it using modern algebraic geometry language. First we define an important tool for study of geometry of varieties over function fields: Gauss-Manin connection. Then we study Picard-Fuchs equations as a tool for translating geometric information about variety to arithmetic information. Finally we study height functions over function fields and their relations with Picard-Fuchs equations