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Design of Low Phase Noise DCO in All Digital Frequency Synthesizers
, M.Sc. Thesis Sharif University of Technology ; Atarodi, Mojtaba (Supervisor)
Abstract
A new class of design has been introduced in the RF circuits and Frequency Synthesizers, which is based on the digital circuits. Implementation of the digital synthesizers suppresses the need to use loop filter and thus reduces the loop lock time. In this thesis different topologies of digitally controlled oscillators using inductor and capacitor tank and all digital architectures used in high frequency all digital synthesizers in 0.18um CMOS technology has been inspected and simulated. Novel techniques introduced to improve the ring oscillator-based design’s specifications which doesn’t need inductor. Using the introduced techniques, the phase noise has been lessened acceptably with respect...
Dynamic NMR Study of 0-Ethyle Morpholine -4-Carbotioate
, M.Sc. Thesis Sharif University of Technology ; Tafazzoli, Mohsen (Supervisor)
Abstract
The Barrier of the internal rotation around C-N bond in O-ethyle morpholine-4-carbotioate were calculated using dynamic NMR spectroscopy (DNMR) in DMSO solvent. 1H and 13C NMR spectra were recorded at different temperatures (295-350K). Band shape broadening patterns at coalescence regions were simulated to extract rate constants of NMR spectera. Transition state thermodynamic properties of internal rotation around C-N bond in O- ethyle morpholine -4- carbotioate are estimated: , , , . To assay reliability of the estimated values, transition state thermodynamic properties were calculated using PCM model at method and basis set B3LYP/6-311++G(d,p). Theoretical values of thermodynamic...
Exploiting Applications and Improving Performance of Polar Codes in Information Theory
, M.Sc. Thesis Sharif University of Technology ; Marvasti, Farrokh (Supervisor)
Abstract
The two central topics of information theory are the compression and the transmission of data. Shannon, in his seminal work, formalized both these problems and determined their fundamental limits. Since then the main goal of coding theory has been to find practical schemes that approach these limits.Polar codes, recently invented by Arıkan, are the first practical codes that are known to achieve the capacity for a large class of channels. Their code construction is based on a phenomenon called “channel polarization”.
Since the performance of polar code degrades when the block length is small, several kinds of Reed – Solomon concatenation is considered in order to improve the...
Since the performance of polar code degrades when the block length is small, several kinds of Reed – Solomon concatenation is considered in order to improve the...
The Effect of Polarization in Edge detection in Dispersive Medium
, M.Sc. Thesis Sharif University of Technology ; Amjadi, Ahmad (Supervisor)
Abstract
Introduction: Today, backward and forward scattering tomography of dispersive medium is of great interest because of its broad applications, especially in medical imaging, of breast cancer, Distinguishing different tissues of the body from each other is one of the necessities. Increasing the quality of the image by just a few percents has great improvement on the tomography resolution.
Materials and Methods: In this project we made phantom of the tissue and tumor from Intralipid 10% plus Agarose and Indian ink for soft tissue and plastic fibers as tumor having birefringence factor of 0.001.After putting the plastic tumor in soft tissue phantom, the polarized white light and a digital...
Materials and Methods: In this project we made phantom of the tissue and tumor from Intralipid 10% plus Agarose and Indian ink for soft tissue and plastic fibers as tumor having birefringence factor of 0.001.After putting the plastic tumor in soft tissue phantom, the polarized white light and a digital...
Study of Light Depolarization in Biological Tissue by Means of the Monte Carlo Simulation
, M.Sc. Thesis Sharif University of Technology ; Amjadi, Ahmad (Supervisor) ; Ansari, Mohammad Ali (Supervisor)
Abstract
In this project, polarization properties, intensity of reflected light, by one layer tissue that has specified optical properties has been investigated by means of Monte Carlo simulation. Fresnel's coefficients were considered in this simulation too. The incident beam was assumed very thin with specified wave length and linear polarization parallel to plane of incidence.This beam was radiated from origin to the tissue vertically. The layer consists of homogenous particles with defined radius. Concentration of particles was constant. 10000 photons with specified weight were launched to tissue in each simulation. The results of reflected light from tissue showed that variation of the size and...
Source Coding with Polar Codes
, M.Sc. Thesis Sharif University of Technology ; Behroozi, Hamid (Supervisor)
Abstract
Polar codes were introduced by Arikan in 2009. These codes are the first family of codes that with low encoding complexity and successive cancellation decoder, can achieve the channel capacity. Polar codes, at first were implemented for channel coding, but in 2010 performance of these codes in binary and q-ary alphabet source was studied. It is shown that these codes can perform efficiently in channel coding and source coding. On the other hand, one of the most important continuous sources are Gaussian sources. Due to the importance of Gaussian sources and good performance of polar codes, we try to evaluate the performance of these codes in Gaussian sources. Note that, these codes have...
Analysis of Circular Slot Antenna on a Ferrite Substrate
, M.Sc. Thesis Sharif University of Technology ; Rajaei, Behzad (Supervisor)
Abstract
Circular polarization (CP) is one of the common polarization types used in wireless systems for frequency identification (RFID), global positioning (GPS) and wireless local area networks (WLAN), since it can provide greater flexibility in orientation angle between transmitter and receiver, and better mobility and weather penetration than the linearly polarized antennas. Magnetic permeability in ferrites can be tuned by external magnetic field ; So ferrites can be good candidates for new reconfigurable CP antenna technology. In this project, we will consider circularly polarized slot antenna with a wide axial ratio beamwidth that consists of a normally magnetized ferrite substrate mounted...
Design and Analysis of Joint Encoding-Encryption Schemes Based on Polar Codes
, M.Sc. Thesis Sharif University of Technology ; Eghlidos, Taraneh (Supervisor)
Abstract
Wide use of communication systems and transmission of huge data has increased the need for cryptographic and encoding systems with high speed operations and lower energy consumptions. Code based and joint encryption encoding schemes are examples of such systems, which enjoy simultaneously high performance and security against quantum computers. So far, there has not been developed any quantum algorithm which can solve any of the hard instances of coding theory based on which these cryptographic schemes have been designed. That is why such systems are called post quantum cryptosystems. The main disadvantage of such cryptosystems is large size the key which is to be stored or shared. In this...
Full Analysis Antenna Ferrite Disk in Range of Negative Permeability
, M.Sc. Thesis Sharif University of Technology ; Rejaei, Behzad (Supervisor)
Abstract
In wireless communication systems increasing the gain of antennas is seminal to increase in coverage and data transmission rate, and reducing the possible errors. One of the main factors for improving the antenna gain is matching the polarizations of the transmitter and the receiver antennas. Towards this end, both the transmitter and the receiver antennas should have the same axial ratio, specific direction and polarizations. As far as the flexibility of the direction angle between the transmitter and the receiver is concerned, the so-called circular polarization is preferred do the linear polarization. The antennas with circular polarizations are prominently utilized in satellites,...
Formation and Investigation of Zinc-Nickel Two Cathionic Electrophospahte Coating Properties on Galvanized Steel
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah (Supervisor)
Abstract
By using electrophoaphating treatment in the metal coating process, the operating temperature of chemical phosphating bath is decrease and also difficulties with the use of high temperature bath is eliminated. The aim of this study is investigate the effect of operating parameter on coating properties and also investigation the deposition mechanism of Zn-Ni electrophosphate coating. Coating properties such as morphology, corrosion resistance and porosity of the coating characterized using SEM, polarization test and electrochemical method respectively. The values used for pH effect was 1.6,1.8,2 and 2.2 results indicated that by increasing the pH value from 1.6 to 1.8 the icorr decrease from...
Modified Forward Osmosis Membrane Preparation for Portable Water Purification Systems
, M.Sc. Thesis Sharif University of Technology ; Mousavi, Abbas (Supervisor) ; Ramazani Saadat Abadi, Ahmad (Supervisor)
Abstract
In this study, mesh-reinforced cellulose acetate (CA)-based membranes were prepared for forward osmosis (FO) by immersion precipitation. Casting composition, preparation conditions, evaporation time, coagulation bath temperature, annealing temperature, CA percent and 1,4-dioxane/acetone ratio were tested for membranes’ performance. Also, the results were compared with commercially CTA membranes. The FO membrane prepared under optimized conditions had a smooth surface similar to commercial ones. The most proper membrane (17.9 % polymer and 1,4-dioxane /acetone ratio 1.89) showed water flux of 9.3 L/m2.hr (LMH) and RSF of 0.536 mol NaCl/m2.hr. Using mesh in the membrane structure, different...
Numerical Modeling of Terrestrial Planet Temperature Distribution Effect on Polar Vortex Forming: Venus Modeling
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
A global rotating atmosphere with polar vortex and super rotation is simulated using a simplified Venus General Circulation Model (GCM). The polar vortex is maintained strongly by meridional circulation develops in the form of a simple Hadley cell, extending from the equator to the pole in both hemispheres and rotation terrestrial planet. Venus Total Polar Vortex Parameter (PVP) was defined like globally integrated super-rotation but at polar skullcaps (60-90 deg). Venus Polar Vortex Parameter is PVP=1.5 that’s qualitatively similar to observed polar vortex. Then with study in terrestrial planet and Titan modeling, we appointed the Polar Vortex Parameter and critical limit of Polar Vortex...
Design and Manufacture of Nanostructured Hydroxyapatite coated Foamy core@compact Shell Ti-6Al-4V Nanocomposite
, M.Sc. Thesis Sharif University of Technology ; Sadrnezhad, Khatiboleslam (Supervisor)
Abstract
The main purpose of this research is design and manufacture of nanostructured hydroxyapatite-coated foamy core@compact shell Ti-6Al-4V bone-like composites for utilization as substitutive implant for cortical bone having porous core. The production procedure consist of two steps; (a) fabrication of foamy core@compact shell Ti-6Al-4V alloy using powder metallurgy-space holder technique, (b) precipitation of hydroxyapatite on the Ti-6Al-4V alloy specimens via pulse electrodeposition process. The bone-like structures were designed to reduce the stress shielding which ensures long-term stabilization of implants. It is while that, the hydroxyapatite coating improve the biological response of...
An Investigation into the Microstructure and Mechanical Properties of Biodegradable Magnesium Alloys Composite-carbon Nanotube Produced by the Mechanical Alloying and Powders Pressing Processes
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor)
Abstract
Properties of biomaterials, especially in application as planting, can be controlled and optimized by alloying and hardening sedimentation. In recent years, the study on the simultaneous improvement of mechanical properties, toughness and corrosion behavior of magnesium composite by carbon nanotubes (CNTs) is very limited. In this study, the behavior of mechanical properties and corrosion of magnesium alloy composites with different percentages of CNTs have been investigated. The production of magnesium alloy composite by powder metallurgy and aging process have been used as effective methods for improving mechanical properties and increasing the corrosion resistance of magnesium alloys. For...
A Dual Polarized Planar Antenna Array for Millimeter-Wave Imaging
, M.Sc. Thesis Sharif University of Technology ; Memarian, Mohammad (Supervisor) ; Fakharzadeh Jahromi, Mohammad (Supervisor)
Abstract
Today's millimeter imaging has been widely used in the field of security and medicine. With increasing security threats, there is a need for improved security equipment. Millimetric waves not only have the ability to penetrate dielectric materials, but also the ability to separate them to detect hazardous materials. Also, the millimeter-field imagery is capable of detecting different materials from each other, which is an advantage in detecting hidden cases. Unlike X-ray imaging, millimeter waves do not have the ability to ionize the cells of the body, which reduces the risk of creating radios for imaging. In this project, an array antenna with two orthogonal poles is designed. Macrostrip...
Modeling and Simulation of Bioelectrochemical Systems
, M.Sc. Thesis Sharif University of Technology ; Yaghmaei, Soheyla (Supervisor)
Abstract
The objective of the present research, for the first time, was to configure a novel dynamic model to be applied in a general manner to simulate bioelectrochemical systems including microbial fuel cell and microbial electrolysis cell. Biochemical reactions engaged in organic substances degradation in both anolyte and biofilm were described by two anaerobic digestion models; Bernard’s anaerobic digestion model and ADM1. In addition, the bioelectrogenesis and electron transfer were modeled based on the direct electron transfer mechanism across the conductive biofilm. The biofilm simulation was established upon the one-dimensional distributions of substrates and microorganisms. In this study,...
Analysis and Design of Dual Polarization Vivaldi Antenna Array for 6-18GHz Range
, M.Sc. Thesis Sharif University of Technology ; Farzaneh, Forouhar (Supervisor)
Abstract
The main objective of this project is to analysis and design of ultra ultra wideband dual polarization vivaldi antenna array for electronic support measure system. In modern satellite communication and radar systems, antenna are required to have the characteristics of both ultra wide band and dual-polarization so as to satisfy various needs such as expanding the information volume, improving the quality of receiving information and increasing the ratio of bandwidth utilization. For this reason we first design a single element of vivaldi antenna for 6-18GHz range and then with design of SMA connector shown that result with and without SMA is same. In the next step we design(under...
Experimental and Theoretical Study of the Lipid Extraction from Wet Microalgae for Biodiesel Production
, M.Sc. Thesis Sharif University of Technology ; Rashtchian, Davood (Supervisor) ; Vossoughi, Manoochehr (Supervisor)
Abstract
In this study, different stages of biodiesel production from microalgae were investigated, specifically the extraction step.Various cultivation methods were also studied among which cultivation under stress was the best. Different carbon sources were also investigated to achieve highest growth. Sodium acetate with complete growth was achieved after 8 days with 6.22% fatty acid recovery. Different mixtures of solvents were compared with Blye and Dier method. Results showed that the mixture of hexane and methanol with crude lipid extraction of 15% and fatty acid recovery of 3.97% were chosen as the solvent mixture of equilibria experiments.Organic solvent composed of hexane (non-polar...
Using Numerical Simulation in the Design and Analysis of Spiral PEM Fuel Cells
, M.Sc. Thesis Sharif University of Technology ; Kazem Zadeh Hannani, Siamak (Supervisor) ; Taghizadeh Manzari, Mehrdad (Supervisor) ; Roshandel, Ramin (Co-Advisor)
Abstract
The gas flow field geometry influences the transport phenomena inside PEMFCs and hence affecting their overall performance. Radial force and secondary flows resulting from curvature of the spiral channels in PEMFCs can improve mass transport limits and so does to their overall performance. Studying the effects of curvature of spiral channels on fuel cell performance and comparing them with similar designs is the aim of this thesis. The geometries are generated using concentric Archimedes’ spirals and categorized as axial or radial depending on the direction of the vector perpendicular to their MEA . Each category has five geometries which are the result of branching the main channel into...
Optimal Design of the Heliostat Field in the Solar Central Receiver Systems
, M.Sc. Thesis Sharif University of Technology ; Boroushaki, Mehrdad (Supervisor)
Abstract
In a solar central system plant about 40% of energy losses occurs in the heliostat field. Furtheremore, half of the investment costs for construction of the plant is related to the heliostat field. Therefore, an optimal design of the heliostat field is necessary for reduction of levelized cost of energy in solar tower power plants. In this study, in order to optimally design the heliostat field, first energy performance of the helistat field in one year is simulated. Solar power and sun’s position at each moment of the day is determined by mathematical relations. Then, loss factors in the field are modelled and heliostat field layout is designed by an algorithm. Finally, by using PSO...