Sharif Digital Repository

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... 

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... 

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... 

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... 

Rammed earth (RE) structures are getting popular due to sustainability, environmental-friendly and economic advantages. Various studies have investigated the mechanical behavior and the energy performance of RE materials. However, little is known about the fracture behavior of RE materials. In this research, the fracture properties of RE materials containing different percentages of various stabilizers were investigated using a modified wedge splitting test. The stabilizers were cement, pozzolan, microsilica, glass-fiber, guar-gum and phase change material. In addition, the effect of stabilizers on the microstructure and the phase composition was inspected using scanning electron microscope... 

Kidney stone disease is one of the diseases that a large number of people experience each year.A Common method for the treatment of kidney stone is the use of acoustic waves, which have attracted the attention of doctors in recent decades. Because of the different structure of kidney stones, the waves transmitted to break these stones are usually performed at different frequencies. Most kidney stones are calcium that can be broken down by using acoustic wave frequencies in the range of 40-20 KHz. Most available lithotripters for the treatment of percutaneous nephrolithotomy (PCNL) are two types: Pneumatic and piezoelectric lithotripters. The lithotripter in this thesis is a piezoelectric... 

Production logging consists of running measurement instruments called logging tools into an oil or gas well to measure various parameters such as temperature, flow velocity, pressure, density, etc. The primary purpose for production logging is to allow enhancing production profits and decreasing costs. Nowadays the common way for fluid density measurement as a part of these tools depends on radioactive source. Special considerations must be taken upon the use of this principle due to its radioactive character. This thesis is focused on a non-radioactive method of determining density. The subject of this thesis is to consider methods for measuring density based on principle of acoustic... 

Low tensile strength and also low strain capacity make plain concrete a ‘brittle’ material. To overcome this shortcoming, the addition of fibre as a reinforcing material has proved to be a reasonable solution. One of the crucial factors in deciding to make this type of concrete is the cost of fibre, which varies depending on its type. In this project a special type of fibre which does not cost a lot and at the same time has a high strength has been used. To investigate the effect of the fibre on the tensile strength of concrete, splitting tensile test (Brazilian test) was adopted. Altogether, 30 standard cylindrical specimens with dimensions of 15 × 30 cm2 were made (3 of each type) which... 

While there are many advantages associated with concrete, including high compressive strength, durability and so forth, on the contrary, it has several disadvantages which may make engineers somewhat reluctant to use it. These include low tensile strength, high brittleness, low resistance to impact, large dimensions of structural cross sections, etc. In recent years, there have been many attempts to surmount these disadvantages by various means such as adding pozzolans, using FRPs, fibres, etc. In this project, the effects of using a special type of high strength steel fibre is studied. In order to investigate the effect of this fibre on the compressive behavior of concrete, 30 cylindrical... 

Selective laser sintering is an additive manufacturing technique based on fusion of powder bed, wherein after spreading a powder layer, a focused laser beam directs onto selected points of powder bed to fuse powder particles together. This process is repeated layer by layer until the final part is created. Although utilization of blade as a conventional powder spreading (CPS) mechanism has a good compression ability, the fixed contact line between blade and powder bed surface results in improper powder flowability and increasing shear forces applied on underneath layer. In this study, in order to obtain the basis for conducting practical experiments, discrete element simulation of powder... 

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,... 

Nowadays cancer has become one of the main and prevailing worldwide challenges in medical field, and many attempts have been made for treatment of this disease. The common methods for cancer treatment, have had significant side effects and even resulted death. The method of “High Intensity Focused Ultrasound” (HIFU) as a non-invasive method, has been welcomed by engineers and doctors and is using in some tumor based cancers. For predicting the level of temperature increasing in tissue, it’s necessary to model the ultrasound waves propagates from HIFU source precisely. The main object of this thesis is modeling and simulation of the behavior of ultrasound wave propagation and investigating... 

Currently, the HIFU (High Intensity Focused Ultrasound) therapy method is known as one of the most advanced surgical techniques in tumor ablation therapy. Simulation of the HIFU therapy in the case of appearance of bon barrier is essential in HIFU planning to improve the usefulness and efficiency of treatment in brain tumor cases. In this work, linear, thermoviscous equations are applied for simulation of phase correction array and steering method, after analysis of performance, these methods are used in a 3D human brain and skull model to estimate thermal ablation in case of using these methods. Results indicate that the maximum focal pressure of 1.42 and 1.65 MPa can be achieved for... 

A biocompatible ferrofluid have been prepared by co-precipitation of FeCl2.4H2O and FeCl3.6H2O under ultrasonic irradiation and with NaOH as alkaline agent. Also cystein was used as capping agent in the solution. Magnetic properties of the produced ferrofluid then determined by VSM test and magnetite nanoparticles were characterized by XRD and TEM techniques. Results indicate the presence of a biocompatible superparamagnetic ferrofluid including magnetite nanoparticles with particle size ranging under 15 nm. The effect of ultrasonic irradiation on presence of a sharp particle size distribution then denoted by comparing the condition with production without ultrasonic irradiation  

In the recent years, there has been an increasing attention toward usage of ultrasonic for enhanced oil recovery practices. But, thorough knowledge of active mechanisms and spreading and characterization of developed fingers during this practice is not available. From the other hand, due to limited amount of light oil fields, more attentions towards recovery from heavy oils is the need of the hour. Documents show that the big issues during the enhanced oil recovery from heavy crudes are high density of reservoir oil as well as poor development of fingers during injection due to high mobility ratios. In this study, results of ultrasound effect on the heavy oil recovery and its effect on the... 

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... 

The fiber-reinforced composite materials possess advantage for structural purpose in various industries. Delamination is recognized as one of the major causes of damage during drilling of fiber reinforced composites, which not only reduces the structural integrity, but also has the potential for long-term performance deterioration. It is difficult to produce precise quality holes with high efficiency by conventional drilling method. Drilling is frequently applied in production cycle while the anisotropy and nonhomogeneity of composite materials affect the chip deformation and machining behavior during drilling. In this thesis, a new non-traditional drilling technology is presented for solve... 

Nowadays, application of ultrasonic wave technology as a novel method of enhancing oil recovery and also gas an 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, it suffers from lack of knowledge about the main governing mechanisms and also there are few mathematical models describing the process. In this study it is intended to investigate the role of ultrasonic waves on rate of recovery and the total recovery from porous media. A model is proposed which can predict the recovery at different times of operation. The results...