فهرست مطالب alireza fadaei tehrani

Since the bacterial microorganism accumulation on the teeth surface causes a biofilm called dental plaque, periodical removal is essential. In novel methods, it is done by an ultrasonic tool creating cavitation; therefore, the dental plaque will be removed from the tooth surface. The dental scaling tool geometry plays an important role in the tool nose cavitation. In this study, the dental scaling tools of one device have been investigated and analyzed by the theoretical equations. Then the natural frequency of the transducer and each of the dental scaling tools were determined by the COMSOL Limited element software and were compared with the results of the theoretical equations. Also, the natural frequency of the tools was known by the impedance analyzer. The effect of the deformation on the nose and curve was investigated by the tools deformation comparison. The dental plaque performed practically displayed a desired accordance between experimental and practical findings.

Todays, since using metallic nanoparticles has been developed in various industries, achieving new methods to produce them is considered as an important issue. Comparing to other nanoparticle production methods, the dielectric discharge process has been emphasized due to its low cost and environmental compatibility. In this study, the ultrasonic-assisted electrical discharge process is designed and manufactured in order to produce copper nanoparticles in di-ionized fluid. The different machining parameters effect, as current intensity, pulse on/off time, and the ultrasonic vibrations on the produced particle size, material removal rate, suspensive particle stability in the fluid, and the particle abundance percentage is investigated. Characterizing the produced nanoparticles is done by different methods. Determining the purity of nanoparticles, percentage of abundance and the average particle size in the dielectric fluid and the produced particle size has been done by applying Energy Dispersive Analysis by X-ray (EDAX), Dynamic Light Scattering (DLS) and Field Emission Scanning Electronic Microscope (FESEM) image, respectively. Based on the results, the produced nanoparticles purity was more than 95%. By using ultrasonic vibration, the nanoparticles stability significantly was increased and the sedimentation time was more than 5 months. Moreover, the average particle size in more than 70% was less than 100 nm.

The increased material removal rate in ultrasonic-assisted wire electrical discharge turning (by∼2 times)was attributed to compressive and rarefying wave front in dielectric and discharge column sliding into plasma channel and molten crater due to applying lateral ultrasonic vibration on the wire. A single discharge was analytically and experimentally studied and the effective forces and factors on plasma channel including Lorentz force¡ increase of pressure and surrounding vapor ionization of plasma channel¡ elongation of molten crater due to lateral displacement of wire and creation of positive and negative pressures of the ultrasonic wave on molten crater were investigated. Experiments were performed in different machining parameters of voltage and power with and without ultrasonic vibrations. By using ultrasonic vibration¡ the plasma density was increased due to decrease of bubble growth. The current density was increased and pressure drop in the end of discharge was increased. As a result¡ a great amount of the material was exploded out of the crater due to bulk boiling. The plasma channel sliding was elongated the molten crater on workpiece surface¡ which leads to material removal increase.

In this article, a special duct is introduced in which, inlet water jet initiates to oscillate after a short time and it causes the velocity and pressure to oscillate regularly. Considering that there is a linear relationship between the inlet jet velocity and its oscillations frequency, the flow rate can be calculated by measuring the pressure frequency. In order to study the flow field inside the current geometry of fluidic oscillator and also to find the optimum location for sensor to detect the pressure oscillation, the unsteady turbulent Navier-Stokes equations are solved by ANSYS CFX software. Having studied the grid independency, capability of K-ε and SST turbulence models for numerical simulation of unsteady flow inside the fluidic oscillator is considered. Then, according to the peak to average ratio (PAR) criterion, the qualities of pressure signals are compared at some points, to distinguish an optimum pressure sensor position. Afterwards, a prototype of fluidic oscillator flow meter is manufactured for the first time in Iran. Using this prototype and inserting the pressure and Piezoelectric sensor at the optimum point, the numerical simulation results are validated by the experimental data. Comparison between the numerical and experimental results shows that the SST model is more suitable for this flow simulation. Finally, by performing experiments in different flows, acquiring and processing pressure signals, the flow meter characteristic diagram (inlet jet oscillations frequency- inlet jet velocity) are extracted.