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Analysis, Design and Optimization of the Rectifier Circuit for RFID and WSN Applications
, M.Sc. Thesis Sharif University of Technology ; Fotowat Ahmady, Ali (Supervisor) ; Sharifkhani, Mohammad (Co-Advisor)
Abstract
In this work, an analytical model has been proposed for rectifiers used in RFID & WSN applications. Body effect has been considered in this model, as well as the effect of transistor size and number of stages on the output voltage of the rectifier. Using proposed equations for both rectifier circuit and the matching network, the power harvesting system is optimized by means of co-designing the rectifier and the matching network. The results of the proposed model are in good agreement with the simulation results.
Finally, A Rectifier circuit which is designed to generate 1-V dc across a capacitive load is presented. Simulation results show that the sensitivity of this power harvesting...
Finally, A Rectifier circuit which is designed to generate 1-V dc across a capacitive load is presented. Simulation results show that the sensitivity of this power harvesting...
System and Circuit Design for High Performance Wireless Power and Data Transfer for Biomedical Implants
, Ph.D. Dissertation Sharif University of Technology ; Fotowat Ahmadi, Ali (Supervisor) ; Ghasem Safarian, Amin (Supervisor)
Abstract
Wireless Power and Data Transfer (WPDT) is a major part of a biomedical implant system. Maximiazing the Power Transfer Efficiency (PTE) and maximizing the data rate are the main challenges in WPDT. In a conventional biomedical implant system, a single inductive link is used to transfer both power and data from outside the body to inside. Data is transmitted by modulating one of the carrier signal properties, i.e., amplitude, frequency or phase. While being simple and robust, this method suffers from the fundamental trade-off between the PTE and data rate. To address this issue, various methods have been proposed including multiple carriers and multiple inductive links, and inductive link...
Cycle by cycle envelope detection and ask demodulation
, Article 27th Iranian Conference on Electrical Engineering, ICEE 2019, 30 April 2019 through 2 May 2019 ; 2019 , Pages 113-117 ; 9781728115085 (ISBN) ; Safarian, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In modern wireless near-filed power and data telemetry systems such as Implantable Medical Devices (IMD), a data rate of several Mbps is required, while the power carrier frequency is limited to few MHz. Therefore, bit rate is comparable to carrier frequency, and the modulated power carrier signal has amplitude, frequency, or phase variation in every cycle. In this paper a very fast amplitude shift keying (ASK) demodulator circuit is presented. The proposed demodulator is able to demodulate a cycle by cycle ASK modulated signal, and a data-rate-to-carrier (DRC) ratio of 100% is achievable. The circuit extracts the clock by limiting the incoming ASK signal. Cycle by cycle demodulation is done...
A cycle by cycle FSK demodulator with high sensitivity of 1% frequency modulation index for implantable medical devices
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 69, Issue 11 , 2022 , Pages 4682-4690 ; 15498328 (ISSN) ; Safarian, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
This paper presents a cycle by cycle Frequency Shift Keying (FSK) demodulator, able to demodulate a FSK signal with 1% frequency modulation index (MI), in a single cycle. Based on the proposed demodulation scheme, a high rate data transmission link can be established through a high-Q inductive coupling link, breaking the basic tradeoff between the power transfer efficiency (PTE) and data rate in single carrier wireless power and data transfer systems. Designed and simulated with 0.18μ m CMOS process, the proposed FSK demodulator, detects successfully a 5Mbps data with a carrier frequency of 5MHz. A test chip is fabricated in 180nm CMOS technology. Measurement results shows that the...
Modeling of Damages such as Crack, Inclusions and Areas with Variable Properties in Composite and Metal Structures and then Prediction and Extension of their Life
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
Nowadays, some of the major problems of the airplane industry is that airplanes’ fleet are approaching to the end of their defined life, inability to buy new planes and obtaining aircraft’s parts for repairing process. Therefore, in order to increase the life of the aging aircrafts, some essential process such as modeling processes, identify principal structure elements to strengthen and repair them should be done to all these airplanes, all these processes refer as aging process. Aging programs initiated in some countries, such as America, Australia, Britain and Canada from about thirty-five years ago, technological approaches inventing new ways to start repairing worn metallic structures...
Analysis and Design of a Duty-Cycle-Controlled Amplitude Shift Keying Class-E Power Amplifier
, Article IEEE Transactions on Power Electronics ; Volume 38, Issue 8 , 2023 , Pages 10470-10479 ; 08858993 (ISSN) ; Tavana, F ; Razavi Haeri, A. A ; Safarian, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
This article presents a method for implementing amplitude modulation in class-E power amplifiers (PAs). The output voltage amplitude of a class-E PA is proportional to the input signal duty cycle. The proposed method exploits this feature in order to implement amplitude shift keying modulation in the standard class-E PA. The conditions for the optimum operation of a class-E PA while using two different input duty cycles are analyzed. The desired conditions are derived at the same time to reduce differences between optimum circuit elements while using different input duty cycles. The resulting class-E PA satisfies both zero voltage switching and zero derivatives of voltage at switching...
Design and Construction of a Soft Actuated Exoskeleton for Hand Rehabilitation of Stroke Patients
, M.Sc. Thesis Sharif University of Technology ; Ghafari, Ali (Supervisor) ; Meghdari, Ali (Supervisor)
Abstract
The main goal of this thesis is the design and development of a rehabilitation device for helping patients “to improve blood circulation” & retain and recover their abilities if possible that were lost during the stroke or a accident like that (my research in karaj/iran shows that it is possible by just movement of the specific body part). The focus is on hand in this thesis because Injuries to the hand are common and can be very debilitating since our hands are our primary means for interacting with our world. For rehabilitation in case of human hand there are several practices that should be done for patients either in home or in a rehabilitation center, time and money that is supposed to...
Interval Determination for Coefficients of a Characteristic Polynomial in Order to Restrict the Location of the Roots
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohammad (Supervisor)
Abstract
One of usual criterion which detrimines how much two polynomials are close to each other is smallness of the norm of vector that is formed from subtraction of their corresponding coefficients. Using this criterion, in this dissertation we become involved in investigation of two similar problems. First one is determination of the closest non-Hurwitz polynomial to a Hurwitz one. During this activity, the robustness margin of Hurwitz polynomial whose coefficients are subject to uncertainty is determined. The second problem is determination of the closest Hurwitz polynomial to another polynomial which is not Hurwitz. Unlike to the first problem, this problem is extremely hard. The solution of...
“Prediction of Stratified Charge Engine Performance Using HC Fuels”
, M.Sc. Thesis Sharif University of Technology ; Mozafari, Ali Asghar (Supervisor)
Abstract
The partially stratified charge (PSC) approach involves micro-direct-injection of pure fuel or a fuel air mixture, to create a rich zone in the region around the spark plug. A theoretical model is presented in this research to predict ignition delay and combustion process in partially stratified charge engine. It considers flame progress through rich and lean regions. Step by step calculations will be carried out in both regions. The process continues to the point where all the fuel is burned. At each step for one degree rotation of the crank shaft, there is a change in cylinder volume and mole fraction burned due to burning of a fraction of the mixture. Considering heat transfer from the...
Prediction of Homogeneos Charge Compression Ignition (HCCI) Engines Performance Using Multi-Zone Model
, M.Sc. Thesis Sharif University of Technology ; Mozafari, Ali Asghar (Supervisor)
Abstract
Some researches have been carried out in the last 20 years in order to increase the present IC engines thermal efficiency and their optimum performance. (HCCI) engine is viewed as a combination of spark-ignition (SI) and compression-ignition (CI) engines. This is because HCCI engines use premixed fuel/air mixture like SI engines and have auto ignition combustion after the mixture is compressed like CI engines. Control of combustion and ignition timing are the main challenges of these engines. Ignition delay, compression ratio, fuel air equivalence ratio and intake temperature and pressure are considered to be the most effective parameters on HCCI combustion.HCCI engines have great potentials...
Prediction of HCCI Engine Performance Using Blend of H2 and HC Fuel
, M.Sc. Thesis Sharif University of Technology ; Mozaffari, Ali Asghar (Supervisor)
Abstract
The idea of improving performance of internal combustion engines has always been important for researchers and manufacturers. In recent decades, due to limited resources of fossil fuels and introduction of vehicle emission regulations, researchers have undertaken more efforts to achieve goals such as increased horsepower, reduced fuel consumption and pollutant emissions reductions. Homogeneous charge compression ignition engine is a modern and efficient design that has attracted attention of many researchers. In[[ these engines, homogenous mixture of fuel and air enters into the combustion chamber and with a mechanism of self ignition, produces more power and has less fuel consumption...
Electric-field-induced Response of Charged Droplets in Uncharged Hydrogels
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Ali Asghar (Supervisor)
Abstract
The electric field induced response of a charged droplet in an uncharged gel is calculated theoretically. For modeling, the gel is considered as a soft porous solid that is saturated with a Newtonian electrolyte and modeled as a continuum that contains 3 phases: a porous, soft and compressible solid, an incompressible Newtonian fluid and the ions inside fluid. Droplet is modeled as a charged incompressible Newtonian fluid immiscible with the gel. The droplet-gel interface is considered as a surface with electrostatic potential ζ . After obtaining governing equations, they solved by using perturbation methodology and linear superposition. Boundary conditions, especially at the droplet-gel...
Janus Silica Nanoparticles and Their Application for Enhanced Oil Recovery
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Ali Asghar (Supervisor)
Abstract
Nanoparticles can be applied as chemical agent in enhnaced oil recovery like surfactants and polymers. One of nanoparticles usefull capabilities is modification of their surface. This research investigates this capabilty of nanoparticles in enhanced oil recovery. Surface modification of nanoparticles with both agents can bring new abilities to these materials. Here surface of silica nanoparticles is modified by hydrophilic agent comprising PEG groups, hydrophobic agent comprising propyl group and both agents. FT-IR tests showed that grafting of modifiyng agents on surface of nanoparticles is well done. To investigate effect of nanoparticles surface modification on nanoparticles capability in...
Synthesis of Amphiphilic Nanoparticles with Different Alkyl Chains and their Application in Enhanced Oil Recovery
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Ali Asghar (Supervisor)
Abstract
Important features of the nanoparticles properties are their high superficial area and being able to reform their surface. In this study, the repairable property used to reform surface of silica nanoparticles (Those are used more frequently than other nanoparticles). Repairing of surface are doing to use nanoparticles as a surface-active material in enhanced oil recovery. Silane compounds with different chain length are used to create hydrophobic nanoparticles and PEG compounds are used to create hydrophilic nanoparticles. Also amphiphilic nanoparticles are created with a combination of both hydrophilic and hydrophobic compounds. To investigate the usefulness of nanofluids are made up of the...
Design and Fabrication of a Microfluidic System Based on Dielectrophoresis for Enrichment and Separation of Bioparticles
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Ali Asghar (Supervisor)
Abstract
The main purposes of this project are simulation, design, and fabrication of a microfluidic system based on dielectrophoresis (DEP) exploiting AC voltages for separation of microparticles. Generally, this project can be divided into two parts. First, the engineering section including design and fabrication of microchip, and second biological samples preparation for investigating the system performance. The main advantages of proposed system are eliminating joule heating, a significant problem in insulating based dielectrophoresis systems, overcoming problems related to metal contamination in biological samples, the main problem of conventional dielectrophoresis platforms, and removing...
Mild Hybrid Vehicle Performance
, M.Sc. Thesis Sharif University of Technology ; Mozafari, Ali Asghar (Supervisor)
Abstract
Many studies on hybrid vehicles have been done in the past few years. The Full hybrid vehicles need a large number of batteries creating up to 300V to meet the required voltage of electric motor. The size and weight of the batteries cause some problems. This research investigates the mild hybrid vehicle. This vehicle includes a small electric motor and a high power internal combustion engine. In most cases the car’s driving force is created by internal combustion part. A small electric motor, which can operate as engine starter, generator and traction motor, is located between the engine and automatically shifted multi-gear transmission (gearbox). The clutch is used to disconnect the gearbox...
Performance Simulation of HCCI Engine Equipped with Direct Injection System
, M.Sc. Thesis Sharif University of Technology ; Mozafari, Ali Asghar (Supervisor)
Abstract
HCCI engines have lower NOX and PM emissions and higher thermal efficiency compared to spark ignition engines. But these engines have some deficiencies which up to now have prevented their widespread employment. These engines have not been very successful at high loads and speeds and in these conditions normally produce high pollution and noise. In order to solve this problem the present research proposes to equip the HCCI engines with fuel injection system so that at low loads and speeds operate at HCCI engine mode and at loads and speeds higher than pre-set limits, use the fuel injection system in order to operate at a combined HCCI and compression ignition engine mode and provide a...
Simulating of Droplet Formation and Calculation of Interfacial Tension by Microfluidic Method
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Ali Asghar (Supervisor)
Abstract
Emulsions are the intermittent dispersion of liquid droplets that have many applications such as polymerization, dyeing, cosmetics, food industry, etc. Droplets can be created in a variety of ways, but the most important point in emulsification and the greatest efficiency of its applications is when the formed droplets are uniform. In the emulsification process, there is a key parameter called interfacial tension, which affects the behavior of the formed droplets, such as their stability and morphology, and its precise measurement is very effective in the quality control of the mentioned applications. Be. In this research, droplet formation in microfluidic systems due to uniform droplet...
Microfluidic Tensiometry and Investigation of Nanoparticles Adsorption at Liquid/Liquid Interfaces
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Ali Asghar (Supervisor)
Abstract
The present paper is an attempt to critically measure interfacial tension with microchannels and achieve the quantity of adsorption in the liquid – liquid interfaces and comparing the adsorption of surfactants and nanoparticles surface modificated as well. At this point we need to make emulsion and it is necessary for droplets to be monodispersed due to analyze these droplets in this paper. According to this condition for our droplets microsystems are the best options. As we know surfactants were already known as a stabilizing emulsion agent and in this paper nanoparticles are suggested as suitable alternatives for surfactants which can be absorbed as if they are in the water / oil...
Microfluidics Biological Separation
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Ali Asghar (Supervisor)
Abstract
The main goals of this research are design, simulation, and fabrication of a microfluidic system working based on dielectrophoresis. This research divided into two different parts, the first of which is the simulation of a microfluidic system, and second of which is an attempt for fabrication of microfluidic system. For the fabrication of the microfluidic system, different methods were used. In the simulation part, the enrichment of different particles was investigated, and the effects of different parameters on the enrichment were assessed. It was observed that as flow rate increases, the enrichment amount diminishes. Furthermore, as the microfluidic depth decreases, the enrichment amount...