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Dr Alireza Ganjovi
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    • Currently, I am a Plasma Physics faculty member (Associate Professor) in the Photonics Research Institute at Graduate... more edit
    In this paper, the output characteristics of a UV pin array pre-ionized TEA CO2 laser have been simulated and compared with the associated experimental data. In our simulation, a new theoretical model has been improved for transient... more
    In this paper, the output characteristics of a UV pin array pre-ionized TEA CO2 laser have been simulated and compared with the associated experimental data. In our simulation, a new theoretical model has been improved for transient behavior analysis of the discharge current pulse. The laser discharge tube was modeled by a nonlinear RLC electric circuit as a real model for electron density calculation. This model was coupled with a six-temperature model (6TM) in order to simulation dynamic emission processes of the TEA CO2 laser. The equations were solved numerically by the fourth order Runge–Kutta numerical method and some important variables such as current and voltage of the main discharge, resistance of the plasma column and electron density in the main discharge region, were calculated as functions of time. The effects of non-dissociation factor, rotational quantum number and output coupler reflectivity were also studied theoretically. The experimental and simulation results are in good agreement.
    The effects of a nonthermal atmospheric plasma jet with argon and argon/oxygen (Ar/O2) gases on live human dental pulp stem cells (hDPSCs) were studied to verify tooth vitality in the pulp-capping process. Using MTT assay, the surviving... more
    The effects of a nonthermal atmospheric plasma jet with argon and argon/oxygen (Ar/O2) gases on live human dental pulp stem cells (hDPSCs) were studied to verify tooth vitality in the pulp-capping process. Using MTT assay, the surviving hDPSCs after plasma jet exposure for 1, 2, and 3 min were counted. First, for the pulsed plasma jet the frequency varied from 10 to 50 kHz for 5 groups with Ar and 5 groups with Ar/O2 plasma jet. Later, with the alternating current (AC) plasma jet, the voltage was changed between 5.5 and 16.05 kV for 13 groups. The cells in the control group were only exposed to Ar and Ar/O2 gases. To control thermal damage to hDPSCs, optical emission spectroscopy was used. For data analysis, the ANOVA repeated measure was used. There were significant differences between the various frequencies and exposure durations (p < 0.05) for the Ar plasma. For the Ar/O2 gas, there were significant differences between frequencies (p < 0.001). For the AC plasma jet with Ar...
    Purpose The purpose of this study is to numerically examine the heat transfer and transport of space charges in the solid insulating materials [low density polyethylene (LDPE), flame retardant type 4 (FR4), Polytetrafluoroethylene (PTFE)]... more
    Purpose The purpose of this study is to numerically examine the heat transfer and transport of space charges in the solid insulating materials [low density polyethylene (LDPE), flame retardant type 4 (FR4), Polytetrafluoroethylene (PTFE)] using the transmission line modeling (TLM) method. Besides, a comprehensive study is performed on the mutual influences of heat transfer and space charges transport within the solid dielectric bulk. Design/methodology/approach The obtained governing equations including continuity and circuit equations are coupled with heat transfer equations, and they are solved via fourth-order Runge–Kutta method. Findings The electric potential and field, current density and temperature distribution are calculated. It is shown that compared with FR4 and PTFE, the temperature increment rate in LDPE is much lower. Moreover, the heat transfer in the solid insulating materials bulk increases the homo-charges density and temperature in the vicinity of electrodes. Henc...
    The tubule occlusion of two newly developed herbal toothpastes was examined. They were prepared based on the mixture of pomegranate peel and Equisetum arvense extracts with strontium acetate. The antimicrobial activity of pomegranate peel... more
    The tubule occlusion of two newly developed herbal toothpastes was examined. They were prepared based on the mixture of pomegranate peel and Equisetum arvense extracts with strontium acetate. The antimicrobial activity of pomegranate peel and E. arvense were determined using minimum inhibitory concentration (MIC). Then, 30 mid‐coronal dentin discs from the human third molars were etched for 30 s with the lemon juice (pH = 2.4). The specimens divided into the three groups. While the control group had 6 specimens, Groups 1 and 2 were including 12 specimens. Group 1 brushed with toothpaste containing 10% strontium acetate and 5% hydroalcoholic extracts of pomegranate peel, and Group 2 brushed with 5% strontium acetate, 5% hydroalcoholic extracts of E. arvense, and 5% hydroalcoholic extracts of pomegranate peel. Brushing was simulated for 6 months with 2 N loading. Then, 50% of discs in each group were immersed in lemon juice for 1 min. Moreover, specimens in control group were brushed with distilled water. Finally, all 30 discs were analyzed using scanning electron microscopy (SEM) and energy‐dispersive X‐ray spectroscopy (EDXS). The occluded dentin tubules were counted and statistically evaluated. It was found that the number of open dentin tubules decreases significantly after brushing with both tested toothpastes compared with control group (p < .001). Moreover, a significant difference was observed between two toothpastes before and after acid immersion process (p < .001). The SEM micrographs confirmed the dentin tubule occlusion of both herbal dentifrices. Besides, EDXS analysis approved the strontium and silica presence on the dentin tubules for the toothpaste which was based on E. arvense.
    In this paper, using a one-dimensional simulation model, the reforming process of sour gas, i.e. CH4, CO2, and H2S, to the various charged particles and syngas in a dielectric barrier discharge (DBD) reactor is studied. An electric field... more
    In this paper, using a one-dimensional simulation model, the reforming process of sour gas, i.e. CH4, CO2, and H2S, to the various charged particles and syngas in a dielectric barrier discharge (DBD) reactor is studied. An electric field is applied across the reactor radius, and thus a non-thermal plasma discharge is formed within the reactor. Based on the space-time coupled finite element method, the governing equations are solved, and the temporal and spatial profiles of different formed charged species from sour gas inside the plasma reactor are verified. It is observed that the electric field increases radially towards the cathode electrode. Moreover, the electron density growth rate at the radial positions closer to the cathode surface is smaller than the one in the anode electrode region. Furthermore, as time progresses, the positive ions density near the anode electrode is higher. In addition, the produced syngas density is mainly concentrated in the proximity of anode dielec...
    – In this paper, the effect of applied electric field on the damage due to partial discharges activity into the surroundings dielectrics of a narrow channel encapsulated within the volume of a dielectric material is evaluated using a... more
    – In this paper, the effect of applied electric field on the damage due to partial discharges activity into the surroundings dielectrics of a narrow channel encapsulated within the volume of a dielectric material is evaluated using a kinetic model based on Particle in Cell - Monte Carlo Collision (PIC-MCC) model. After application of an electric field across a dielectric material which contains a narrow channel, repeated ionization process starts in the gaseous medium of narrow channel. Charged particles, especially electrons, gain energy from the electric field across narrow channel and cause damage into dielectric surfaces of narrow channel on impact. The dependence of the electron energy distribution function (EEDF) on the applied electric field is studied. It is seen that, during PD activity within narrow channel, the damage to the surrounding dielectrics and consequently the surface conductivity increases. These estimations are performed based on the number of C-H bond-scission...
    In this paper, the effects of plasma discharge parameters on the nano particles formation process in a plasma enhanced chemical vapor deposition (PECVD) reactor using a model based on equations of ionization kinetics for different active... more
    In this paper, the effects of plasma discharge parameters on the nano particles formation process in a plasma enhanced chemical vapor deposition (PECVD) reactor using a model based on equations of ionization kinetics for different active species are studied. A radio frequency applied electric field causes ionization inside the reactor and consequently different reaction schemically active species are formed. The reactions leading to production of nano-particles include negative and positive ion, neutrals and radicals. The dependency of the background gas temperature, frequency and amplitude of applied electric field as the main plasma discharge parameters on the avalanche time constant, nano-particles formation and their growth rate is verified. Silane and hydrogen gases are considered as background species. It was observed that the growth rate at higher frequencies and lower temperatures is higher. It was seen that increase in the applied voltage peak amplitude affects charged and ...
    A kinetic model is used based on Particle in Cell Monte Carlo Collision (PIC-MCC) model, for parametric study of the damage due to partial discharges (PD) activity into the surroundings dielectrics of a narrow channel encapsulated within... more
    A kinetic model is used based on Particle in Cell Monte Carlo Collision (PIC-MCC) model, for parametric study of the damage due to partial discharges (PD) activity into the surroundings dielectrics of a narrow channel encapsulated within the volume of a dielectric material. The parameters studied are applied electric field, channel dimensions and gas pressure. After employing an electric field across a dielectric material which contains a narrow channel, repeated ionization process starts in the gaseous medium of narrow channel. Charged particles, especially electrons, gain energy from the electric field across narrow channel and cause damage into dielectric surfaces of narrow channel on impact. The dependence of the electron energy distribution function (EEDF) on the applied electric field is considered. These estimations are performed based on the number of C-H bond-scissions produced by the impacting electrons of a single PD pulse. Regarding this technique, the consequent damage ...
    A kinetic model based on Particle in Cell - Monte Carlo Collision (PIC-MCC) model is used for parametric study of the damage due to partial discharges activity into the surroundings dielectrics of a narrow channel encapsulated within the... more
    A kinetic model based on Particle in Cell - Monte Carlo Collision (PIC-MCC) model is used for parametric study of the damage due to partial discharges activity into the surroundings dielectrics of a narrow channel encapsulated within the volume of a dielectric material. The parameters studied are applied electric field, channel dimensions and gas pressure. After application of an electric field across a dielectric material which contains a narrow channel, repeated ionization process starts in the gaseous medium of narrow channel. Charged particles, especially electrons, gain energy from the electric field across narrow channel and cause damage into dielectric surfaces of narrow channel on impact. The dependence of the electron energy distribution function (EEDF) on the applied electric field is studied. These estimations are performed based on the number of C-H bond-scissions produced by the impacting electrons of a single PD pulse. Based on this technique, the consequent damage int...
    In this paper a theoretical model for transient behavior analysis of the discharge current pulse in the transversely excited atmospheric pressure CO2 laser with pin array pre-ionization is presented. The laser discharge tube is modeled by... more
    In this paper a theoretical model for transient behavior analysis of the discharge current pulse in the transversely excited atmospheric pressure CO2 laser with pin array pre-ionization is presented. The laser discharge tube is modeled by a non-linear RLC electric circuit. By this method the governing partial differential equations are reduced to a system of ordinary differential equations. The equations are solved numerically by the fourth order Runge–Kutta numerical method and sum important variables such as Current and Voltage of the main discharge, Resistance of the plasma column and Electron density in the main discharge region as a function of time, will be calculated.
    In this paper, a lumped RC circuit model, which is based on the Transmission Line Modeling (TLM) method, is used to describe the space charge production and displacement mechanisms in three different solid dielectric materials (LDPE, PTFE... more
    In this paper, a lumped RC circuit model, which is based on the Transmission Line Modeling (TLM) method, is used to describe the space charge production and displacement mechanisms in three different solid dielectric materials (LDPE, PTFE and FR4). Each dielectric material is considered as a transmission line with the capacitive and resistance elements. The obtained circuit equations are solved along with the continuity equations for the various charged species in the bulk of solid dielectric material. The electric potential and field, density of different charged species and their recombination rates, resistive and capacitive properties of the solid dielectric material are calculated. In addition, the effects of the variations in the applied voltage, dielectric permittivity and temperature on these physical parameters are examined. Besides, compared with LDPE and PTFE, the net charge density increment rate in FR4 is much higher. Moreover, the influences of temperature on the net ch...
    The two dimensional Particle in Cell - Monte Carlo Collision (PIC-MCC) model for simulation of partial discharges inside a narrow micro-channel presented in part 1 is used in this second part to study the effect of various parameters. The... more
    The two dimensional Particle in Cell - Monte Carlo Collision (PIC-MCC) model for simulation of partial discharges inside a narrow micro-channel presented in part 1 is used in this second part to study the effect of various parameters. The parameters studied are applied electric field, channel dimensions and gas pressure. The effect of the number of initial electrons assumed at the onset of simulation is further studied in order to validate the results. It is observed that the extent of damage caused by a PD is primarily determined by the total number of impacting electrons capable of producing bond-scission at the dielectric. Parameters that effectively cause an increase in the number of energetic electrons increases effective damage as well as surface conductivity of surrounding dielectrics.
    In this work, the operating parameters of the plasma antenna are optimized using a kinetic model based on Particle in Cell‐Monte Carlo Collisions (PIC‐MCC) method. This optimization study is performed via the investigation of variations... more
    In this work, the operating parameters of the plasma antenna are optimized using a kinetic model based on Particle in Cell‐Monte Carlo Collisions (PIC‐MCC) method. This optimization study is performed via the investigation of variations in the operating parameters of the plasma antenna, i. e., its dimensions, background gas pressure, and the applied voltage frequency and their consequent effects on the plasma frequency, kinetic energy of electrons and plasma current density of plasma antenna. While the antenna performance is improved at higher tube lengths and applied frequencies, it is optimized at a particular tube radius. Moreover, higher background pressures have increasing effects on the plasma antenna operation. Based on this parametric study, the optimum operating parameters of the plasma antenna are established. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
    ABSTRACT