Sharif Digital Repository

The electrical voltage, current and power output is calculated due to harmonic forced vibration of shell energy harvester. So five electromechanical equation together with Gauss equation is solved for doubly curve shell harvester in steady state condition in order to derive voltage, current and electric power output. The effect of shell curvature in cylindrical and spherical shells, the harvester series or parallel connection of layers and thickness of substrate and piezoelectric layer, is also considered in order to obtain maximum power output. The results show for small shell curvatures a high frequency load is needed to obtain maximum power and when the shell arc length is three times to... 

In recent years, multiport bidirectional converters have been a center of attention in renewable energy systems. This research focuses on three-port bidirectional converters. First, series resonant bidirectional converter is precisely analyzed. This analysis includes sinusoidal, exact state space and small signal analysis through phasor concept. This converter can work in higher switching frequencies and higher power ratings in comparison with common DAB bidirectional converter due to its inductor impedance cancellation. To increase power rating a three-phase version is proposed which has reduced output filter capacitance. Then, three-port bidirectional resonant converter is proposed and... 

In this thesis a novel passive method for integrated blood pressure monitoring in implantable applications has been proposed. The main constraints of such implantable systems are power consumption, area and simplicity of the implanted part and detected pressure is transmitted wirelessly to the external system and recorded. In this thesis an oscillator in 0.18um CMOS process has been proposed to detect the resonance frequency of the implanted tank circuit in the external unit of an implantable blood pressure monitoring system. Other designed circuits include a buffer, frequency detector, voltage to current converter and an 8 bit analog to digital converter. The system is capable of measuring... 

One of the robots that has become more important recently is radio control helicopters. According to the intrinsic unstability of these helicopters and possibility of crash with the surroundings, it is needed to have a device which the helicopter can be fixed to so the ability of motion is reduced and a safer flight is achieved. In the recent applications of these helicopters, the autonomous flight ability of these devices is more noticed; and a lot of controllers are proposed to achieve this goal. It is obvious that these controllers are needed to be tested; and benchmarking a controller in the software simulation environment is not reliable; so a test stand is needed.
In this project a... 

Long lasting portable power is an ultimate desire for electronic devices. The limited capacity of the batteries in addition to the heavy weight and extra costs are the main challenges of the batteries for energy storage in large electrical devices like electric vehicles. Wireless Power Transmission (WPT) technology can address these issues by providing online electric power for these portable devices. Furthermore, this technology can supply electric devices especially portable ones by eliminating cables and connectors with more reliability.The current research is focused on optimum design of the wireless power transfer system for electric vehicle charging applications. The optimization of... 

Atomic force microscope (AFM) has a significant capability of imaging surface topography on an atomic scale. It is also widely used for Nanolithography in MEMS/NEMS (micro/nanoelectromechanical systems). Conventional AFMs consist of a cantilever with a sharp conical or pyramidal tip located at the free end of the cantilever that plays an important role in AFM measurements. Scanning across a surface, AFM interacts with the sample surface through its tip. Although the dynamic behavior of the AFM cantilever is complicated, the researchers have been interested in studying AFM dynamic behavior because it has a great influence on the surface imaging process. The imaging rate and contrast of... 

Experimental investigations in the subject of dynamic response of machine foundations for verification of many theoretical studies are scant. The effects of several factors, namely, shape and weight of foundation, frequency of vibration, depth of embedment, dynamic load levels and type of loading (harmonic and impact) on dynamic response of foundation were studied experimentally.Also, the current methods of machine foundation analysis mostly are based on the concept of the dynamic impedance function. Therefore, using these tests results, impedance functions for the model are calculated and presented. The physical model tests were carried out in a steel container with dimension of 1×1×0.9 m.... 

In this research, soft magnetic-soft composite of iron-borosilicate was prepared by cold compression and then heat treatment at 850 ° C. In order to prepare the initial mixture, the pure iron powder was mixed with different particles of 2% by weight of borosilicate and pressed at 400, 800 and 1200 MPa, and then subjected to thermal treatment at 850 ° C for one hour. After examining the density, electrical resistance, magnetic properties of DC, the magnetic properties of these materials were studied in the frequency range of 10-1000 kHz at room temperature and at 300 ° C. The results show that increasing the particle size increases the saturation magnetization and magnetism and reduces the... 

Due to the key role of implant stability and Oseointegration in dental implant success, in the last two decades, many methods have been proposed to assess these parameters. Resonance Frequency Analysis (RFA) is one of these methods that attracted special attention and has been widely used in implant stability assessment. In the present work, a method is proposed that uses fuzzy logic to solve RFA restriction in evaluating Oseointegration degree.
In the first part of this work, a 3-D finite element model of implant-bone system is used to study factors affecting system resonance frequency. Then, fuzzy logic is used to propose a method for evaluating degree of Oseointegration. The designed...