Sharif Digital Repository

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... 

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... 

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... 

Iodine isotopes are among the most significant medical radioisotopes with a wide range of applications in therapy and diagnosis. The I-131 isotope is usually synthesized by irradiation of natural tellurium in atomic reactors. But there is an alternative route in which this isotopes is produced along with two other significant medical radioisotopes (i.e. Mo-99, Xe-131) by neutronic irradiation of uranium in the reactors. To separate iodine isotopes especially in the extraction process of fission fragments, it is necessary to be selective adsorption of iodine on a selective adsorbent. One of the most selective adsorbent for this application is copper. The aim of this study is to compare the... 

Recently, cooperative communications have gained much interest due to its ability to mitigate fading in wireless networks through achieving spatial diversity while resolving the difficulties of installing multiple antennas on small communication terminals. There have been considerable research efforts on the performance analysis of cooperative diversity. This is while most of the current works assume that perfect knowledge of the channel information is available at the destination and/or relay terminals. However, in many practical scenarios, due to the errors caused by Doppler shift or noise on the pilot signals the perfect estimation of channel coefficients is not possible. In this thesis,... 

In the present study liquid thermophysical properties in electrospray has been studied. Other parameters such as electrical configuration do not change during this study. For this purpose Alcoholic fuels have been chosen because of their high energy density and their polarity that make them suitable for electrospraying. Electrical conductivity, surface tension, viscosity, density and permittivity are the most effective liquid properties in the electrospraying. The visualization method used for this study is shadowgraphy and light scattering method. In this study the range of flow rate and voltage is acquired for each operational mode and Q-V diagram has been obtained for all liquids... 

In recent years, social robots have used simple and complicated context-aware systems to provide better services for users. The navigation module is one of the most important modules in which a context-aware system can be used; Where a social robot can change the way it navigates with respect to the context that the users are experiencing in a manner that fits the cultural background of the users. This kind of navigation helps the robot to keep its users safe both psychologically and physically. In this research, we present a context-aware navigation method that changes its proxemics due to the group context the users are experiencing. This research consists of three main parts: first, a... 

In today’s competitive world, productivity is one of the main components that guarantee the success and profitability of an industry or a project. This research has studied productivity of dam construction projects in Iran that are usually classified as mega projects. First, the major factors influencing productivity of dam construction projects in Iran were identified and evaluated. Three main sources of information namely; literature review, records and lesson learned from previous projects and experts’ opinions were used to identify these factors. Then, 41 main factors influencing productivity were selected and the effect of each factor was measured based on the results obtained from... 

More than half a century has passed since the start of research on seismic liquefaction phenomenon in cohesionless soils, and various researchers has proposed different correlations for liquefaction prediction based on in situ tests. However, there still exists a great uncertainty in liquefaction prediction correlations, and liquefaction still occurs in different parts of the world. Hence, the main objective of this research is to reduce uncertainty in seismic liquefaction initiation correlations. While the technical literature indicates that soil resistance can alter due to liquefaction and shaking events and soil resistance after the liquefaction is not necessarily indicative of it prior... 

Given the increasing concerns about climate change and the depletion of fossil fuel resources, the use of renewable energy as a sustainable and environmentally friendly solution has gained significant importance. This study examines a building that utilizes solar and geothermal energy to meet its heating and cooling needs. The system is analyzed from energy, exergy, and economic perspectives. Initial system design results showed that chilled water at 7°C and hot water at 59.13°C are produced. Among the three types of collectors examined, the thermal photovoltaic collector was selected for its simultaneous electricity and heat production and optimal efficiency for combination with an... 

Today, high-efficiency inverter-fed electrical machines (such as Permanent-Magnet Machines) are increasingly used in a wide range of industrial applications, vehicles, and servo mechanisms. The performance of these machines strongly depends on the control unit, and particularly on the position sensor. To achieve improved performance and ensure proper electronic commutation, the rotor position must be determined accurately. Compared with other commercial position sensors, such as encoders, selsyns—owing to their electromagnetic structure—provide higher accuracy in harsh industrial and high-vibration environments. Although extensive research has recently been conducted on two-phase selsyns... 

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... 

Statistical studies indicate the fact that in Iran, like many other developing countries, a significant percentage of buildings are made of traditional materials and most of them are adobe buildings especially in rural areas. Furthermore, geological data indicates that Iran is located in alps-Himalayas seismic zone and exposed by destructive earthquakes and adobe buildings suffer the most damages comparing with other type of the structures. According to these explanations, this research deals with adobe buildings behavior and provides solutions for reinforcing them and improving the seismic response of these buildings. These studies include numerical modeling with finite elements methods by... 

An isopropanol supercritical reducing environment was prepared by fabricating a high temperature, high pressure autoclave, in order to make a hybridized structure of zinc oxide and graphene oxide, entitled as ZnO-G. In this novel structure, the oxygen acts as bridging element between zinc and carbon, that connects a wide band gap semiconductor to a narrow banded one. The hybridization mechanism is studied by FTIR analysis, and morphology is shown by FE-SEM. The micrographs obtained from the thin film show a stacked pile of ZnO-G disks, like a button, dispersed on a crack free layer. In addition, the crystallographic structure was revealed by comparing low angle X-ray diffraction patterns to... 

For neurodegenerative diseases like Multiple Sclerosis, Alzheimer’s, or Parkinson’s disease early detection is required to slow progression and prevent disease onset. To do so, identifying early signs and symptoms of the disease as well as modifying lifestyle can play a crucial role. Nowadays, the increasing use of smart gadgets and sensors has paved the way for collecting behavioral data and therefore analyzing and extracting meaningful patterns. In this study, lifestyle and cognitive performance data have been collected via a platform called OptiMind. Previous studies have shown that the Integrated Cognitive Assessment (ICA) can identify patients with neurodegenerative disorders (such as... 

Laser-assisted machining is nowadays considered as an alternative to conventional machining processes including ceramics grinding, which has provided the basis for extensive experimental and numerical studies in this field. Since the main difference between laser-assisted machining and conventional machining is in the presence of lasers, the main purpose of this study was to investigate the effects of laser on the laser assisted machining process. In this regard, in the first step the process of laser heating to the ceramic workpiece has been studied experimentally and numerically by finite element method. The material used in this research is a slip cast fused silica ceramic. The... 

In this thesis we consider the problem of distributed computation by many processors.We mainly concentrate on matrix multiplication problem in this thesis because of its importance. A distributed system consists of N worker processors and one master processor. The master processor should distribute the computation between workers and after computation in each of them, collect the results. In this thesis, we are going to mitigate the effect of straggler processors by using coding methods. Straggler processors can cause delays in the computation time.In this thesis, we firstly introduce a method to multiply any number of matrices in each other. The proposed method occurred in one shot without...