Sharif Digital Repository

There are several methods for measuring thin film thickness, however, for the analysis of liquid film motors [1] we need a method which is capable of measuring the thickness using a single image of the film. In this work, we use the colors that appear on thin films, such as soup bubbles, which is a result of light interference to calculate the thickness of the layer  

Thermal relaxation time is the time when maximum temperature of a particle get to 1/e of it’s initial value. The destruction of a tissue depends to this important parameter. This parameter has studied by Monte Carlo simulation of pulsed laser in to environment as healthy and cancerous tissue. The main goal of this method is providing proper temperature in a special area so that minimize thermal destruction around that area. In this thesis, temperature distribution of tissue that is caused by pulsed laser, has solved by new method;in this new method the pulse duration uses for Monte Carlo simulation. Also using the solution of radiation transfer equation by Discretes Ordinate Method, new... 

By direct and alternating electric field applied to thin film of liquid suspended in the air we can spin out and control it. Rotation pattern depends on the geometry of the electrodes and the applied magnetic field. This is called a rotating liquid film (Liquid Film Motor). To determine the cause of rotation, different models have been proposed. In this project we have tried to check the accuracy of any of the models. Using particle velocimetry using the photo, we calculate the velocity pattern. Then, using the Navier-Stokes equation calculate the acceleration and viscosity from the velocity. Then, for a special arrangement using a finite diffrent method, electric potential and the electric... 

Ultrasound waves have attracted substantial attention due to their potential for trapping the small particles, which cannot be handled by usual tweezers. The acoustic tweezer is a technology that is able to tarp and control the movement of micrometer to millimeter objects by standing or focused sound waves. Acoustic tweezers are the subject of many researches around the world, due to simplicity, cost-effective, biocompatibility and most important better performance in non-transparent optical environments, compared with optical tweezers.In this project, by using a ring piezoelectric and a power amplifier, an acoustic tweezer was designed and constructed. Moreover, the polystyrene particles... 

Eyesight is one of the most important tools for humans to communicate with environment and consequently, blindness or poor eyesight results in unsatisfactory effect on life quality. Owing to the importance of the sense and to assist to the patients, this thesis aims to design and assemble cybernetic glasses using ultrasound waves. To this end, firstly, the notion of waves focusing on ultrasound waves is described and reactions of human hearing system to the waves are studied. Then, the transducers as a key device are introduced. Afterward, bat sense system to communicate with environment which is based ultrasound waves is described. Next, attenuation effects on ultrasound wave pressures are... 

Introduction: Today, backward and forward scattering tomography of dispersive medium is of great interest because of its broad applications, especially in medical imaging, of breast cancer, Distinguishing different tissues of the body from each other is one of the necessities. Increasing the quality of the image by just a few percents has great improvement on the tomography resolution.
Materials and Methods: In this project we made phantom of the tissue and tumor from Intralipid 10% plus Agarose and Indian ink for soft tissue and plastic fibers as tumor having birefringence factor of 0.001.After putting the plastic tumor in soft tissue phantom, the polarized white light and a digital... 

Investigation of electrohydrodynamic behavior of fluids under electric fields is a challenging and impressive matter in condensed matter physics. In this thesis, inspired from previous works on liquid film motor, a new phenomenon has been observed and its properties has been investigated.Here by making a new device named “Liquid Film Electric Generator” we produced potential difference on the rotating suspended liquid film under electric field. The power conducted by electrodes has been generated on the surfaces of the film. By this method, under electric field of 1000 V/cm, micro-watt electric power can be achieved on a liquid film of diameter of about 1 cm.We explained this phenomenon on... 

In Fourier domain optical coherence tomography, we can measure the optical thickness (refractive index n times thickness d), of sample’s layers. In this work, we introduce a new method for measurement of refractive index and physical thickness of multiple layers simultaneously by Fourier domain optical coherence tomography, without additional information about the structure of the sample under investigation. The input data to the formulation are the optical path lengths (OPLs) and suitable set of wavenumber of the FD-OCT interference spectrum. The output of simulation suggest that, the accuracy of the extracted parameters depend on the difference in the refractive index gradient of sample... 

Optical coherence tomography is a rapidly evolving imaging technique that enables non-invasive cross-sectional imaging of high-sensitivity semi-transparent samples (poor scattering). The biggest limitation of optical coherence tomography is the low penetration depth (about a few millimeters) in tissue. OCT is based on low-coherence interferometry. In this study, we investigate Michelson and Mach-Zehnder interferometers in OCT set-up and explain the advantages of using Mach-Zehnder interferometers in OCT systems. Furthermore, in this thesis, we have shown that by using Mie scattering, we can have forward scattering, hence the penetration increases. We have suggested this method as a solution... 

Polarization-sensitive optical coherence tomography is a non-invasive imaging technique that is capable of producing two-dimensional or three-dimensional images using the additional properties of light, as well as qualitative examination of the sample. This system, like optical coherence tomography, is mainly used in ophthalmology as a powerful tool for the early detection of eye diseases. PS-OCT can obtain high-resolution cross-sectional images of ocular fibrous structures, such as the retina or anterior segment, which show birefringence when injured. The main purpose of this dissertation is to develop an analytical model of system layout to study important parameters such as birefringence.... 

Scientists want to know how they can control fluids motion. They use electric fields for controlling the fluids in different dimensions. In small size, application of electric fields is very important because of biological applications. We use electric current and field for rotating freely suspended films. Here, we study soap, polar and non-polar liquids, MBBA liquid crystal and ferrofluids films. We show that the surface charge plays the crucial role in rotating the films.We study the correlation between rotation of a film and different physical quantities.Our experiments confirm that dipole moments of fluid molecules do not show a clear effect on the rotation. Increasing the dipole moment... 

Precise leak detection by acoustic signal analysis calls for robust similarity measures to estimate the time delay between recorded leakage signals and minimize the probability of false alarms, in the face of dispersive propagation, multiple reflections, and unknown correlated, uncorrelated and impulsive background noise. Providing evidence that higher order modes and multi-reflected signals behave like sets of correlated noise, this thesis uses a regression model to optimize residual complexity in the presence of both correlated and uncorrelated noise. This optimized residual complexity (ORC) is highly robust since it takes into account both the level and complexity of noise and signal,... 

In this project, polarization properties, intensity of reflected light, by one layer tissue that has specified optical properties has been investigated by means of Monte Carlo simulation. Fresnel's coefficients were considered in this simulation too. The incident beam was assumed very thin with specified wave length and linear polarization parallel to plane of incidence.This beam was radiated from origin to the tissue vertically. The layer consists of homogenous particles with defined radius. Concentration of particles was constant. 10000 photons with specified weight were launched to tissue in each simulation. The results of reflected light from tissue showed that variation of the size and... 

The tissue characteristics are important for all kinds of medical laser applications in order to understand the interaction mechanisms between light and tissue. Knowledge about light transport in tissue is essential for cancer treatment and cancer diagnostic techniques. By having the diffused reflectance of a tissue we can determine its optical characteristics. In this thesis we have solved the inverse process. That is, we compute the diffused reflectance of a turbid media with pre-determined optical parameters. This problem can be solved using two methods: Monte Carlo simulation and diffusion method. Since Monte Carlo simulation is computationally very expensive, it is not used in medical... 

Ultrasound waves have been one of the passions of researchers of different fields for many years. In recent decades the potential of ultrasound waves for trapping and manipulating micro-particles has been noted by many researchers. “Acoustic Tweezers” is the name given to this application of ultrasonic devices. The advantages of this device over its optical counterpart, named “Optical Tweezers”, are its low price, ease of use, biocompatibility and its capability of being used in opaque media. In acoustic tweezers, particles can be trapped either by making standing acoustic waves, or by making highly focused narrow beams and trapping the particles in potential wells. In this research... 

Flow measurement in both types of single phase and multiphase has a crucial place in a wide variety of industries, specially petroleum industry. for single phase flowmeters, improving their precision using different types of mechanical, mathematical and analytical techniques will be considered as an important step. Using multiphase flow meters will cause no need of volume catching and costly separators and also make us capable of taking well-timed decisions in production management. for making flow meters weather multiphase or single phase, there is a crucial need of a multiphase flow loop. To achieve that, an 8-meter-long flow loop using transparent Plexiglas pipes with inside diameter of... 

People in the organization who are influential, opinion leaders, decision-makers and approvers need to be incorporated into the entire Strategic Planning process at some levels .The Management of these Stakeholders involves identifying their organizational roles and their disposition towards and understanding of Strategic Planning, then to work with them throughout the process to improve or maintain their opinion of the value of Strategic Planning through continuous updating and addressing of their issues, concerns and questions. Physical asset practitioners apply the physical asset management framework and policies to ensure the performance and output potential of physical assets through...