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... 

In this thesis, a cellular model of electroporation process and its detection by ultrasound signals is proposed. Electroporation is permeabilization of the cell membrane, caused by an external electric field. The resulted pores open cell’s membrane to large or hydrophilic molecules. The process of Electroporation has been used in Gene therapy and treatment of solid tumors. In this project, first we made a phantom of electroporated tissue and a phantom of normal tissue and then we simulated their responses to a linear array ultrasound transducer. By comparision of received signals from phantoms the probable effect of electroporation on ultrasound RF signals revealed. Results show up to 5 %... 

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... 

In past three decades, use of crude oil’s derivatives increased dramatically. The critical environmental condition of today’s world, which majorly caused by unclean fuels, forces governments to legislate new rules to increase quality of fuels. These rules force refinery industries to produce clean fuels. One of the main processes in producing clean fuels is Desulfurization process. For fuel desulfurization there are different kinds of processes like HydroDesulfruization, Oxidative Desulfurization, Bio-desulfurization, etc. From these processes Hydro-desulfurization is the conventional process for desulfurization. Because of significant problems of this process, like high operational cost,... 

Carbon Nanotube webs exhibit interesting properties when used as thermo-acoustic projectors. This work studies thermo-acoustic phenomena of these sound sources both in near and far field regions. Our three-dimensional simulation and experimental data show pressure waves are highly affected by dimensions of sound sources in near field due to interference effects. Although pressure amplitude increases with increasing frequencies, maximum pressure amplitude reached in lower frequencies may become larger than its maximum amount at higher frequencies because of interference effects. Measurement of different surface area sources shows generation of sound waves in far field is independent of... 

This work concerns with experimental and modeling investigation of the asphaltene damage removal using ultrasonic wave irradiation. A specific core holder apparatus was designed and utilized for in situ ultrasonic exposure to damaged core plug at different conditions of exposure time, ultrasound power and distances between sound source and plug. Injection of many pore volumes of an asphaltenic crude oil was used for creating asphaltene induced damaged in porous media through permeability measurements. The deposited asphaltene during oil injection as well as asphaltene removal due to ultrasonic exposure was evaluated using IP-143 analysis. The results revealed that ultrasound application... 

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... 

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... 

Nowadays, application of ultrasonic wave technology as a novel method of enhancing oil recovery and also gas and oil well stimulation is prevailing. Not only this method is environment friendly, but also it is economic. Although the application of this method is proved to be of outstanding positive influences in field operations. In this study, it is intended to investigate the effect of ultrasonic waves on the rate and final recovery of miscible and immiscible injection of fluids as Enhanced Oil Recovery (EOR) methods by using the Micro model apparatus and Although the effect of the waves on fluid flow through the porous media can be studied. The results of this work are a good guidance to... 

Nowadays, using one-pot multicomponent reactions in the synthesis of organic and natural compounds has attracted a lot of attention due to their ideal synthetic features. These types of reactions play an important role in synthetic chemistry by reducing reaction steps, costs, wastes, and by-products and increasing the reaction efficiency as an efficient method. The issue that led to this project was the development of a novel procedure for developing synthetic methods for the synthesis of thioxo-pyrrolidine 3-carbutamide compounds. In this study, the first Mumm rearrangement was performed by using dithiocarbamates by applying ultrasonic irradiation. The reaction was investigated in methanol... 

Nowadays, microgyroscopes are among the most important products of MEMS. The production of small, precise and inexpensive gyroscopes has become possible as the result of recent developments in fabrication technology. In this thesis it is intended to introduce a new method for manufacturing more precise microgyroscopes regarding manufacture facilities. Using this new method, sensitivity and resistance of microgyroscopes are increased against noises which are primarily caused by vibration and rotation about undesirable axes. The rotational movement imposed on the gyro is detected through fluid flow within its torus channel. This transformation facilitates the measurement of the initial motion.... 

Near wellbore formation damage is caused additional pressure drop around the wellbore and therefore decreased the oil or gas productivity of the well. The usual methods for removal of these damages are acidizing and hydraulic fracturing which have operational limitations in addition to high costs. Thus the researchers are motivated to find new methods and technologies specially the use of mechanical waves for well stimulation purposes.Ultrasonic waves have been extensively used in many industrial applications including clean devices, pipes and vessels. A clear extension of this usage is the removal of wellbore contaminants by exposing it to high-power ultrasonic waves. Although several... 

In this project we focused on Ultrasonic waves as novel, effective and well-controllable means for cell wall disruption and disintegration to provide faster and more complete penetration of solvent into cellular materials and improve sugar mass transfer and extraction from sugarcane and sugar beet. Impact of frequency, temperature, power density and reactor shape on Ultrasonic wave efficiency in extraction process has been investigated and the result was utilized to design a semi-pilot reactor. In the optimum situation, sucrose extraction from sugarcane improved to 4.51 gr/100 ml H2O that had a significant increasing from 2.1 gr/100 ml H2O extraction in thermal only process at 70 °C. Optimum... 

Laboratory experiments were carried out to investigate the effect of ultrasound waves on sludge reduction in MBBR bioreactor for industrial wastewater. The experiments were performed using two identical 20L MBBR bioreactor under same operational conditions. In MBBR with return sludge, sludge was collected from clarifier and after being sonicated, returned to the system by pump.
For determining optimum intensity and time duration of ultrasound, 0.3lit of MBBR sludge was sonicated with intensities of 20, 30, 60, 120, 150, 250 w/cm2 and time duration of 5, 10, 15, 20, 30 min. Afterward, these two parameters were optimized with Energy Efficiency Index. As the results shown, intensity of 120... 

In this thesis its considered the characterization of an ultrasound wave in a medium with some obstacles. Derivation of speed of molecules and pressure of the wave is carried out in the Cartesian coordinates system. Simulation is carried out to prove the dependency of wave speed to set up parameters such as the target point (x,y,z) at which the speed value is obtained, the location of the obstacles, the amplitude of original wave emitting from the source, and the propagation speed in different layers of the medium. From the numerical results, it is apparent that the amplitude of the speed wave gets degraded as the wave travels through the medium which is a function of reflection and... 

In this research non-contact ultrasonic based method is used for liquid level measurement in a container. A system has been designed and developed to determine the liquid level and show the results on a personal computer. The system contains three main parts, which are mechanical and electronic parts and the programming. The setup can measure the liquid level with the accuracy of 1cm. An ATMEGA8 microprocessor commands to relays and controls the pumps. The pumps are used to change the height of the liquid in the containers to accurately calibrate the sensor and test its operation. The ultrasonic sensor, which is mounted above the vessel, transfers the data to an ATMEGA64 microprocessor for... 

According to the importance of conversion and transmission of energy, and introduction of hydrate formation process as an alternative method, in this study, the nano-graphene oxide is used to increase the rate if methane gas hydrates formation. The experiments were performed at different concentrations of 30 to 70 ppm and the results were compared with pure water. The effect of temperature and pressure on hydrate formation at temperatures of 1 and 2˚C and pressures of 48 and 53 bar were studied. And it was found that nano-graphene oxide can be used to accelerate the methane hydrates formation. The effect of ultrasonic on methane hydrate formation has been studied that it was found that the...