Sharif Digital Repository

Routine ultrasound calibration methods have some restrictions such as: low bandwidth, low frequency resolution, limited spatial resolution, the high cost of test and risk of damage to the transducer when exposed to high powers. In this thesis, a new technique based on microbubble resonance is proposed. Non-linear resonating microbubbles produce harmonics;the first harmonic may be masked by reflection from larger microbubbles as well as unwanted reflections which cause ambiguity in the determination of the amplitude of the excited pressure. Therefore, the second harmonic is used, with a single characteristic peak. In order to model the physical phenomenon, the second harmonic generated in the... 

Ionization chamber is used in radiotherapy for to get precise information from amount activity of radionuclide. Ionization chamber filled with Argon is used to measure the activity of brachytherapy radionuclide. This device measures the activity according to the produced current by the incident radiation. In order to obtain the precise activity of the radionuclide, it is necessary to the precise amount of the device calibration factor which relates the amount of the produced current to the activity. Because of little access to standard radionuclide and for appointing the activity of unknown samples, ionization chamber calibration is done indirectly and with the help of the simulation of the... 

Continuous increase in population which leads to increase in water demand, negative ecological and environmental impacts of dam constructions for supplying water, surface and groundwater pollution and climate change impacts on water cycle are among the major reasons that has made water supply into a crisis specifically in the past two decades. This issue is highlighted in regions with arid or semi-arid climatic conditions. Water demand is the key stimulus in the complex and dynamic water resources system which causes interaction among economical, social and environmental sub systems. These issues together with political challenges led to the introduction of integrated water resources... 

After the heart-rending earthquake in Bam and its severe losses, the engineering community forced to pay special attention to the seismic vulnerability of traditional structures. Therefore, with the aim of reducing of such devastations to minimum, a multi-phase research project was defined at Sharif University of Technology to study the vulnerability and retrofitting of these structures which the current study is the eighth phase of that series research. In the third and fourth phases of this project, a typical adobe building with dome roof was chosen for study making use of shaking table facilities. The tests included both un-retrofitted and retrofitted states and considerable seismic... 

In designing of sheet metal forming processes, knowledge of the maximum permissible strains in the sheet is of prime importance for the design engineer. Thus, a large amount of experimental and theoretical researches have been carried out to estimate these limiting strains. A renowned and prevalent theoretical method for prediction of forming limits is the Marciniak and Kuczynski model. In this model, it is assumed that a small groove exists in the sheet even before applying the loads; and due to the weakness of this region, necking starts from there. The major problem of the M-K model is requiring of an experimental point to “calibrate” the results. Furthermore, while experiments indicate... 

Statistical studies indicate the fact that in Iran, like many other developing countries, a considerable percentage of houses are in the form of traditional buildings, and major losses due to recent earthquakes are because of masonry building collapse. In the early twentieth century in Iran every ten years a destructive earthquake has been occurred which has resulted in huge human casualties and economic losses. After the Bam 2003 earthquake, a team project was defined to investigate the behavior of rural houses with the aim of providing solutions to lessen seismic hazards, and the current study is the fifth phase of the following line of investigations. Among the existing kinds of rural... 

Recent stringent HC and CO emission regulations are because of increasing consciousness of the perilous influences of exhaust emissions. The chief attempt to pass the standards is to decrease the emissions during cold-start, due to catalytic converters are not efficient until they arrive a light-off temperature. It has been discovered that 50% to 80% of the controlled HC and CO emissions are sent out from tailpipe of automotive during the cold-start. Therefore, in order to minimize the cold-start emissions and fast light-off of catalytic converters, it is important to understand the catalytic converter characteristics and techniques for rapid warm-up catalyst. This thesis describes a... 

Increasing demand for high-speed and high-resolution ADCs as much as low-power ones and on the other hand, the obstacles in the way of reaching them make calibration and compensation methods more significant for obtaining ADCs with the better specs. Among the cases which need modification, the modification of C-2C-based SAR ADCs, which can decrease the power significantly, and the modification of time-skew error of time-interleaved ADCs, which is the main and the most challenging error in this type of ADCs, could be the two of the effective ways to making the State-of-the-Art ADCs. In this project for the first time, a novel compensation method for C-2C parasitic charges is proposed which... 

One of the important jobs of ESM and Elint receiver is to find the direction of arrival of the targets. Also DOA estimation has applications in guiding missiles and jammers location, position finding using of multiple DF systems which are placed in different locations is the most important use of this type of system.
A DF system has multiple parts: receiver, algorithm and arrays of antennas.
Amplitude comparison algorithms are more simple but on the other hand phase comparison algorithms prepare more accurate estimation. In this thesis these algorithms are simulated and to each other. And it will be concluded that, in the application being test, the "MUSIC" algorithm is the best.... 

Beam diagnostics is an essential constituent of any accelerator. The position information of the electron beam is obtained by a set of Beam Position Monitors (BPMs), which in addition to determining the position, are used to derive information concerning lattice functions and beam dynamics. To design of Button Beam Position Monitor(BPM) for a Synchrotron Light Source, to get beam stabilities on submicron levels, preliminary studies were done to have optimal design. We present an algorithem which caculate all required parameteres for different design of button BPMs. To calculate induced charge and voltage on each button, Poisson's equation has been solved by Green method. For sensivity... 

Modern sensors consist of arrays of detectors specially arranged to enhance precision, capabilities, and field of view (FOV). Sensor arrays can have multiple functionalities such as the simultaneous detection of position and motion. We use a linear sensor model and develop an optimization method to design an array of photodiodes. Our objective function minimizes bias and variance estimations. We introduce a maximum likelihood technique to approximate and determine the bias caused by measurement errors, and verify our theory by statistically complete simulations. We apply our theory to design an optimal sun sensor. The sensor has a predefined conical FOV, and its accuracy is controlled by a... 

In this thesis we are going to improve an ultrasonic flowmeter accuracy by considering the influence of different parameters like temperature, pressure, etc. Firstl of all different cases of flow condition in which ultrasonic flowmeter may work are specified, then velocity and temperature profile of pipe flow are determined using Fluent software. In thr next step ultrasonic pulses transmitted are simulated by the use of code written in Matlab to find wave travel time in the flow. Evetually an accurate relation of calibration for flowmeter is determined by the use of travel time and all other flow properties to evaluate the accuracy of flowmeter in diffent cases. Relation extracted can be... 

In this paper the predictive equations for collapse assessment of shear links used in eccentric braced frames are developed. An extensive database including results of over 70 cyclic tests on steel wide flange shear links is collected and the structural parameters governing the hysteresis behavior are calibrated using a simplified numerical model. The methodology of calibration is to minimize the discrepancy between the experimental hysteresis loops and the corresponding numerical results using Particle Swarm Optimization (PSO) algorithm. The objective function of PSO algorithm is minimized by iterating parameters that govern the hysteresis behavior of the numerical model. Stepwise... 

In adaptation with nature, Flapping Wing Arial Robots (FWARs) are flying vehicles that use wing flapping motion to produce lift and thrust forces simultaneously. Wing oscillating motion of FWARs in turn creates an unsteady and turbulent flow field around them that makes their aerodynamic modeling and analysis a complex and formidable task. As a result, experimental aerodynamic investigation of FWARs has been the focus of many researchers in the last few years. Inspired by nature, Bird-like FWARs utilize a tail as an augmented aerodynamic surface during their flight motion. In turn the tail aerodynamics that in general plays an important role in flight stability and control is adversely... 

This Thesis was an effort to write and quantify an agricultural economic model for Urmia Lake Basin and evaluate the change in water consumption in reaction to a policy change. Aggregated form of the data gathered from 33 counties located in Urmia Lake Basin was used in this research. This data includes the quantity used of each input and their costs, in addition to crop yield and their selling price. In our model, the representative farmer takes into account the price of various inputs, crops and the condition of the farm and its limitations and decides on the profit-maximizing crop pattern. In this model, water is one of the most important inputs and its price and availability, effects the... 

Considering that the agricultural sector is the largest consumer of water in the basin of Lake Urmia, it seems necessary to provide comprehensive methods of water resources management and formulate appropriate policies to increase water productivity in this sector. For this reason, in this research, we examine the effects of creating a water market in the basin of Lake Urmia. For this purpose, models of agricultural economics and positive mathematical programming techniques at the regional level have been used for modeling to analyze the various effects of water market creation. According to the model, the farmer chooses his cultivation pattern according to the price of the crop and the... 

Video stabilization is one of the main quality enhance- ment techniques for the data captured by a moving/shaking video recorder. In this work, we focus on video stabilization in smartphones equipped with inertial measurement units (IMU). Specifically, we present a fully differentiable dynamic computational graph to compensate for simple pinhole camera model deficiencies, using the suggested model and estimated angular rotation changes inferred from IMU data, We try to improve and stabilize shaky videos. Further using qualitative and quantitative approaches we show our method’s supremacy against current state of the art stabilization methods. This work accompanied with software and necessary... 

In this thesis, a wideband multi-standard digital transmitter based on the multi-path architecture has been designed in 65-nm CMOS process. Moreover, the effect of phase error of the clocks on the output specifications of this multi-path transmitter has been analyzed, and based on the derived theoretical equations, circuit-level solutions for the correction of these errors have been proposed. In addition to the circuit-level solutions for error correction of the clocks, a general setup for calibration of the multi-path transmitter has been presented. Also, several software-based algorithms for the calibration of the transmitter have been studied and their validity has been verified using... 

The need to measure the authenticity of food has always been an important concern of many countries. Since food fraud can cause serious problems, every year, much research is conducted in the field of food authenticity all over the world. Milk among dairy products and orange juice among fruit juices are two categories of widely consumed beverages all over the world, therefore they are exposed to various frauds from the manufacturers. Frauds such as adding water to milk and preservatives such as hydrogen peroxide, formaldehyde, and sodium hypochlorite are common frauds that are added to milk to increase its volume and storage time. Among the common cases of adulteration in orange juice, we...