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Study and Preparation of the Modified Nanostructure Carbon Electrode for Capacitive Deionization (CDI) Process
, Ph.D. Dissertation Sharif University of Technology ; Ahadian, Mohammad Mahdi (Supervisor) ; Shahrokhian, Saeed (Supervisor)
Abstract
Nowadays capacitive deionization (CDI) has attracted a lot of attention for water treatment. CDI is an emerging water treatment technology that uses electrophoretic driving forces for desalination of water. During the CDI process, ions are adsorbed onto the surface of electrodes by applying a low voltage electric field (DC<2V). In addition, the regeneration of the electrodes contains desorption of the electrosorbed ions from the surface of the electrodes to the water in the absence of the applied electric field. In the mechanism of CDI, separation and accumulation of ions in the electric field are the main processes and no additional chemicals are required in this technology. Therein,...
Investigation of the Ion Migration Mechanism and its Effect on the Slow Response of Perovskite Solar Cells
, Ph.D. Dissertation Sharif University of Technology ; Taghavinia, Nima (Supervisor) ; Mohammadpour, Raheleh (Supervisor)
Abstract
In recent years, organo-metal perovskite solar cells have attracted remarkable attention due to their low cost manufacturing method as well as the rapid growth of efficiency. Despite the fast growing efficiency of organo-metal perovskite solar cells, there are big challenges around their low stability under real operational condition. In addition to extrinsic parameters like oxygen and humidity, intrinsic instability of perovskite rises mainly from ion migration in perovskite film. In order to understand the ion migration and its effect on photovoltaic parameters of the devices, appropriate characterizations and analysis are needed. Since ions are much slower compare to electrons, their...
Modeling, Identification and Control of an Electrostatically Suspended Gyroscope
, M.Sc. Thesis Sharif University of Technology ; Ghanbarpour Asl, Habib (Supervisor)
Abstract
This paper presents a novel method for satellite attitude determination, using Electrostatically Suspended gyroscope (ESG). In this method, two superconducting rings rotated around a spherical rotor, which causes a variable flux in rings. So according to faraday’s law of induction, a voltage will be induced in the rings. Using this voltage and a kalman filter, attitude of satellite will be determined. ESG works precisely, when the rotor is maintain at the center of gyroscope cavity, between three pairs of circular electrode, so a backstepping control algorithm will be designed In order to this purpose. The performance of attitude determination using this ESG and designed control algorithm is...
Approximation Algorithms for Clustering Points in the Distributed Model
, M.Sc. Thesis Sharif University of Technology ; Zarrabi Zadeh, Hamid (Supervisor)
Abstract
Clustering is one of the most well-known fundamental problems in computer science. In this thesis we have focused on a particular version of such problem, called capacititated k-center, and we analyze and survey them in the distributed model, when massive data is given. Our contribution in this research includes a new approximation algorithms with constant approximate factors for such problems in the distributed model, as well as improving the best available algorithm for capacitated k-center problem. Composable coreset as one of the most important techniques in distributed and streaming model is our primary tools in designing these algorithms. This technique gives the opportunity of solving...
Estimation of Ground Thermal Properties Using Inverse Heat Transfer Techniques
, M.Sc. Thesis Sharif University of Technology ; Hakkakifard, Ali (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor) ; Biglarian, Hassan (Co-Supervisor)
Abstract
Ground-Source Heat Pumps (GSHPs) are efficient means of space heating and cooling. However, owing to their high installation costs, their development in societies has not grown as it should. Therefore, it is crucial to have a meticulous design of these systems. The first step in designing GSHPs is determining the ground and grout thermal properties. Thermal Response Tests (TRTs) are developed for this purpose. The previous methods of estimating the unknown thermal properties are either computationally inefficient or yield inaccurate estimates for the ground volumetric heat capacity, to which the mean fluid temperature has the slightest sensitivity among all thermal properties. Among previous...
Synthesis of Titanium Carbide Mxene-Carbonaceous Material Composite as Capacitive Deionization Electrode for Water Desalination
, M.Sc. Thesis Sharif University of Technology ; Khachatourian, Adrineh Malek (Supervisor)
Abstract
Capacitive deionization (CDI) is a suitable method for water desalination with low energy consumption and high efficiency, which does not have secondary pollution and is environmentally friendly. The hybrid capacitive deionization uses a faradaic electrode next to the carbonaceous electrode, taking advantage of both electrodes, and high capacities have also been reported. Titanium carbide Mxene is an important candidate in CDI due to its high electrical conductivity and tunable interlayer distance, but Mxene suffers from low oxidation resistance. Therefore, in this research, molybdenum disulfide (MoS2) that is an essential member of the 2D transition metal dichalcogenides family, was used as...
Analysis of C-2C DAC Mismatch Effects in SAR ADCs
, M.Sc. Thesis Sharif University of Technology ; Sharif Khani, Mohammad (Supervisor)
Abstract
Analog to digital converters is one of the main building blocks of today's circuits. These circuits play an important role in signal processing. Since these circuits consist of analog and digital sections, a large percentage of the power consumed in a circuit is allocated to this section. Therefore, in applications such as medical devices, wearable applications and wireless technology where power control is very important and necessary, reducing the power of analog to digital converters is very important. One of the simplest analog-to-digital converters from the design point of view is Successive Approximation Register (SAR) analog-to-digital converters. This type of analog-to-digital...
Multi-depot Vehicle Routing Using Predictive Distributed Cooperative Method
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohammad (Supervisor)
Abstract
Due to conspicuous increases in shopping and goods transportation in this unbridled world, a significant part of companies’ final interest and final cost are related to their distributions of goods. Meanwhile, because of practical constraints of service hours and service distances, logistics companies usually build multiple depots to serve a great number of dispersed customers. Hence, multi-depot vehicle routing problems (MDVRP) win more and more engineers’ and companies’ attention to thrift their cost by using optimization methods. Considering NP-hardness of MDVRP and the lack of optimal solution derived by heuristic and meta-heuristic approaches in the large scale problems, in this...
Condition Monitoring of the DC-link Capacitor in Back-to-back Converter Using Main Transient Parameters
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
Condition monitoring of a system refers to the process of measuring and analyzing the aging indicators of critical components of a system that can be harnessed to estimate the system’s health. One of the main interests in condition monitoring is to performing the scheduled maintenance activities for the system. Monitoring the status of the system reduces maintenance costs and prevents unwanted contingencies and outages in the system.
In power electronics, the capacitors are the most critical components of the system from the point of reliability. Capacitors are the leading cause of failure in the power electronic converters so, this essay attempts to attain a solution to monitor the...
In power electronics, the capacitors are the most critical components of the system from the point of reliability. Capacitors are the leading cause of failure in the power electronic converters so, this essay attempts to attain a solution to monitor the...
Investigating Excitation and Geometrical Effects on the Behavior of Cold Plasma
, M.Sc. Thesis Sharif University of Technology ; Rashidian, Bijan (Supervisor) ; Faez, Rahim (Supervisor)
Abstract
Cold plasma has many applications in micro electronics industry. In this study, several examples of widely used plasmas systems have been investigated. First, the theory and physics of each type of plasma has been studied. Then the applications of each type have been discussed. Finally, the accuracy of the statements has been investigated using COMSOL multi physics software. In 1&2 D simulations the effects of all macroscopic parameters on plasma properties and its behavior have been investigated. In the design of plasma excitation source, plasma impedance is a very important parameter for maximum power transfer. Plasma impedance has been calculated with COMSOL software. Different modes of...
Dynamic Modeling and Stability Analysis of PV Plants and their Impact on Network Stability
, M.Sc. Thesis Sharif University of Technology ; Parniani, Mostafa (Supervisor)
Abstract
Due to the growing rate of photovoltaic plants in power systems, in the future years this type of plant will have significant contribution in electrical energy generation. For this reason, the impact of photovoltaic plants on various aspects of power system operation should be investigated. In this research dynamic impacts of photovoltaic plants on small signal stability of power systems are analyzed. For this purpose, improved dynamic equivalent models are developed for large-scale photovoltaic plants, based on integration of the plant modules. It is shown that the usual assumption of ideal DC power supply at the input of plant inverter is inappropriate, and that the DC-DC converter and DC...
Design and Fabrication of 2D Multi-Electrode Array (MEA)Devices to Evaluate Functionality of Neural Cell Network and Cardiac Cells
, M.Sc. Thesis Sharif University of Technology ; Fardmanesh, Mehdi (Supervisor)
Abstract
Microelectrode array technology is a broad platform for studying and characterization of the electrophysiological properties of excitable tissues derived from both brain and heart in vitro. Microelectrode arrays can either record or stimulate cells by accessing multiple sites of neural networks and cell tissues and detect signals from all sources around each electrode simultaneously. By using recorded signals, one can detect cell potential changes and its minor fluctuations. Unlike intracellular recording techniques, the noninvasive interface of microelectrode arrays with cells provides durable studying of neural networks and cell tissues. Using related microelectronics fabrication...
Analysis and Optimal Design of High-Voltage High-Frequency Transformer with Parasitic Elements Consideration for Microwave Power Module
, Ph.D. Dissertation Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
Applications of high voltage power supplies is increasing. Microwave power module is one of the applications. In microwave power module, the dimensions of the power supply are very important. On the other hand, the parasitic elements of the transformer of a high voltage power supply are significant because of high insulation distances and transformer high turn ratio. These elements including stray capacitance and leakage inductance change the converter behavior. In this thesis, a method for dimensional efficient design of high voltage power supply used in microwave power module is presented considering and analyzing the transformer parasitic elements. Beforehand, at first, the transformer...
Capacitive Sensors for user Gesture Recognition in Smart Environments
, M.Sc. Thesis Sharif University of Technology ; Karbalaee Aghajan, Hamid (Supervisor)
Abstract
To create applications for smart environments we can select from a huge variety of sensors that measure environmental parameters within the premises. Capacitive proximity sensors use weak electric fields to recognize conductive objects, such as the human body. They can be unobtrusively applied or even provide information when hidden from view which make these sensor more popular. Furthermore, these sensors are low cost, precise and low power. In this thesis, we study the construction and operation of capacitive sensors and the challenges of using them. Then we use them to produce smart devices. Smart flooring is used on the ground and it can be used to track people or fall detection. Smart...
Optimal Design of Medium Voltage Modular Multilevel Inverter with Reliability Consideration
, M.Sc. Thesis Sharif University of Technology ; Zolghadri, Mohammad Reza (Supervisor)
Abstract
Modular multilevel converters provide higher output voltage levels than switches rated voltages by switching between cascaded modules. Increasing the number of modules might results in less reliability because of an increase in the number of elements. On the other hand, an increase in the number of modules decreases the semiconductors rated voltage, switches power losses and thermal stresses and consequently a lower switches failure rate is expected. Therefore the optimal number of modules, would minimize the failure rate. To investigate it, in this project, first fundamental elements of converter are designed for a MMC with different number of output levels, to drive a medium voltage medium...
Circuit and Systematic Design of Low Power SAR ADC
, M.Sc. Thesis Sharif University of Technology ; Sharif Khani, Mohammad (Supervisor)
Abstract
Low power and high speed analog-to-digital converters (ADCs) are the key elements of communication and computing systems. There are several ADC structures such as delta-sigma, flash, pipeline, and successive approximation register (SAR) for different applications, albeit SAR ADCs are natural candidates of onchip designs for their low power and scalability benefits. Nowadays, SAR ADCs are widely being used in low-power moderate-resolution applications which need several tens of MS/s to low GS/s sampling rates. By virtue of the technology scaling power consumption of digital parts of a SAR ADC is reduced significantly. As a result, in a SAR ADC the power consumption of the digital-to-analog...
Design of Oscillator with Active Inductor and Investigation of Noise Cancellation in Oscillators
, M.Sc. Thesis Sharif University of Technology ; Sharif Bakhtiar, Mehrdad (Supervisor)
Abstract
In this thesis, at first, we study the active inductors have been reported in the literature. Then by choosing one of them and investigating its advantages and disadvantages, we changed the structure in a way to solve its problems. On the way by using this active inductor and a negative capacitor, we designed an oscillator in 1.5 GHz frequency that has -106 dBc/Hz phase noise at 1MHz offset and its FOM value is 160 dBc. Also this oscillator is capable of frequency tunability of oscillation from 500 MHz to 2.2 GHz. In this spectrum the phase noise is changing between -100 dBc/Hz and -110 dBc/Hz. In the second part, in the aim of improvement of phase noise of oscillator structures based on...
Obtaining the Frequency Response of Voltage Transformers
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
In this thesis a new method to determine the accuracy of CVT in measuring harmonics has been proposed. Capacitive voltage transformers are known as an important tool in measuring the harmonics. However, the frequency response of CVT contains cut-off and pass characteristics, because of the resonances of the internal elements. One of the main problems is in determining the frequency response of HV voltage source capable of accurate change to apply to CVT. The proposed method reduces the voltage level of the HV source. Also, the source structure and the effect of the additional elements are described and the accuracy of the method has been evaluated by simulation and experimental results
Design of Wide-Band, Low Noise, Low Power OPAMP using Negative Capacitance Circuit and a Novel Method for Reducing Power Consumption and Die Area of Active RC Filters
, M.Sc. Thesis Sharif University of Technology ; Sharif Bakhtiar, Mehrdad (Supervisor)
Abstract
Gain bandwidth products of Operational Amplifiers are dependent to power consumption. In this thesis we introduce negative capacitance circuit as a candidate to improve GBWs of OPAMPs in constant power, or achieve the requested GBW in lower power consumption. First we characterize negative capacitance circuit and introduce a model for that. Then we see how pole-zero placement will change, when we add negative capacitance circuit to a circuit node. As an application we use this circuit in Folded Cascode and Current mirror OPAMPs and give design guideline for this topologies. A three stages and a one stage OPAMP is designed in 0.18um CMOS, for the application of negative capacitance...
Adsorption Processes in Capacitive Deionization
, M.Sc. Thesis Sharif University of Technology ; Taghavinia, Nima (Supervisor)
Abstract
Today the water crisis affects billions around the world.According to existance of large amount of salty water on the earth, it seems one of the best soloution is desalination of salty water.There are methods for removing ions from water such as thermal methods, membrane methods , chemical methods and capacitive deionization.Capacitive deionization is based on the deviation of ions in the electric field.CDI system contains of two conductive porous electrodes that an elecric field is applied between them.While the brine pass through the space between the elecrodes the ions are absorbed by elecrodes. After a while the electrodes get saturated so a reverse potential is needed to regenerate the...