حسن مهدیان

Today, the expansion of manufacturing knowledge and high consumption rates have led to increased attention on polymers. However, many polymers face challenges with colorability, as their surfaces often do not accept color well. This issue arises from the low surface energy of polymers, necessitating improvements in adhesion prior to printing. Polypropylene (PP), in particular, exhibits surface characteristics that require modification to enhance its hydrophilicity. This research aims to identify an effective method for altering the surface properties of this polymer. One promising approach is the use of surface dielectric barrier discharge plasma treatment, which can activate the PP surface more efficiently than conventional methods, making it more conducive to dyeing.When the polymer is exposed to a plasma environment, electrons, ions, free radicals, and other particles collide with the surface, activating it and enhancing its hydrophilic properties. As a result, the surface becomes better suited for bonding with colored materials. In this study, we demonstrate that surface plasma treatment effectively reduces the water contact angle and increases surface energy, transforming the polypropylene polymer into a hydrophilic material.

Production of gaseous products through non-thermal plasma technology is an innovative method for refining heavy oil or petroleum residues. In this study, plasma sparks were generated in gas bubbles to break the hydrocarbon bonds in oil and produce valuable gaseous products. This research aims to develop a more efficient and sustainable method for refining heavy oil or distillation column residues using non-thermal plasma. This study describes the construction of a reactor designed at the Plasma Research Institute of Kharazmi University, the stages and circuitry for generating plasma sparks, the method of gas collection, and the analysis techniques for gaseous products. Heavy oil was poured into the reactor, and argon gas was used to purge the circuit of oxygen. Additionally, plasma sparks were generated in argon gas bubbles injected into the oil. The paper examines the utilization and optimization of gas usage in the process. The primary gaseous products obtained, forming the highest percentage of the gas mixture, were hexane (13.8%) , pentane (15.7%) , and 2-methylbutane (12.75%). After plasma application and gaseous product storage, the remaining heavy oil exhibited no significant changes in its state and remained suitable for its original uses.

In this paper, a test particle model is developed to study the electron acceleration in a magnetized plasma-filled waveguide by a twisted electromagnetic wave with variable amplitude and phase along the longitudinal position. With appropriately assigned initial values, the electron total energy gain is obtained using numerical analysis without calculating the dispersion relation. Numerical results show that as long as the twisted electromagnetic waves significantly affect the electron acceleration, during the passage of an electron through the waveguide, one may employ an optimum value of the external magnetic field to obtain the maximum energy gain.

Plasma is a subgroup of advanced oxidation technology (AOP) that has received considerable attention. It is currently being used to degrade persistent pollutants and inactivate organisms in environmental bodies. The objective of the present study is to decolorize tatrtrazine aqueous dye solution using cold atmospheric plasma technology. The main parameters selected for the study were initial dye concentration (4-20 mg/L), pH of the solution (2.2-9), input AC voltage (70-110), treatment time (10-30 minutes), and the electrode distance, which was kept at 8 mm throughout the experiment. The primary parameters investigated through the optimization tool of response surface methodology (RSM) software were color concentration, solution pH (2.2-9.4), power supply voltage (70-110 V), and detention time (10-30 minutes). The experimental reactor had a capacity of 15 ml. The color removal study of the plasma process showed that the optimal condition occurred at an initial concentration of 14 mg/L, voltage of 86 V, pH = 4.1, and plasma irradiation time of 18.7 minutes, resulting in a color removal percentage of 99.78%. According to half-life and efficiency yield calculations, the process was suitable for application in water pollution decontamination, with the lowest half-life achieved at the optimum condition (1.18) and the highest efficiency yield (108.3 mg/Kwh). The results extracted from the quadratic model illustrate the direct effect of retention time and initial voltage and the inverse effect of pH and initial concentration of industrial dye on the removal efficiency. The contact time had the major influence on efficiency via its coefficient in the model equation, while among interactive parameters, pH and contact time had the most interactive influence on the process. The reaction rate could also be described by the first-order kinetic model with an R2 value of over 95%.

In this paper, the collisional filamentation instability of an electron beam-weakly magnetized and ionized plasma has been investigated in the presence of background plasma, using the fluid description. By describing the equilibrium configuration in the presence of binary collision terms between charged and neutral particles and using the local approximation method, the dispersion relation (DR) of instable mode (filamentation instability) has been obtained and the effect of collision and magnetic field driven-destabilization and current-driven stabilization on the growth rate of instability has been studied. The results show the cut-off wave number and the magnetic threshold for the filamentation instability in the collisional magnetized plasma in which the instability will disappear for the larger wave number and larger magnetic fields. Studies show that the value of cut-off wave number and magnetic threshold are raised by increasing the electron beam current density.

In this paper, quantum two-stream and multi-stream instabilities have been studied by taking into account the effect of Fermi pressure term. The dispersion relation is calculated by means of a quantum non-relativistic hydrodynamic model. It is shown that there is no any free energy for velocities shorter than Fermi velocity in the system and hence the plasma system is stable in this condition. On the other hand, it has been observed, taking into account the effect of Fermi pressure decreases the maximum growth rate of instabilities but cut-off wave number increases. It is found that the growth rate and cut-off wave number of two-stream instability is larger than multi-stream instability due to Focusing of energy.

The generation of coherent Terahertz (THz) radiation is studied which is produced from moving the relativistic electron beam through a helical wiggler with axial magnetic field. The relativistic electron beam is modulated via interacts with the beat wave of two laser beams that have frequency difference in THz range. When the modulated relativistic beam of electrons go through the helical wiggler with axial magnetic field, it radiates coherent THz electromagnetic wave as an antenna. In addition, the numerical study has shown the maximum THz power increases with the increasing axial magnetic field power.

The fluid description is employed to investigate the instability of Newtonian viscous shear dusty plasma system in hydrodynamic regime, taking into account both viscosity and collision effects. Describing the equilibrium configuration in the presence of the binary collision terms between dust grains and neutral particles and using the local approximation method, the dispersion relation is obtained by applying the generalized hydrodynamic equation to find the spatial dependence of the initial velocity in equilibrium state. Analyzing the obtained dispersion relation shows that the main factor of free energy source to arise the instability of the system is due to the viscous force. While the collision effect plays a stabilizing role for the system by reducing the growth rate of the instability of the Newtonian strongly coupled dusty plasma system in the hydrodynamic regime.

The Grad- Shafranov equation plays an important role in the analysis of the plasma equilibrium in magnetic confinement configurations such as tokamak. In tokamaks which are operating in Ohmic heating regime, the Grad- Shafranov equation can be expanded through the inverse aspect ratio parameter. Consequently, the first order of the poloidal flux function and poloidal/radial components of the magnetic field are obtained. It is possible to estimate the Shafranov equilibrium parameter in a semi-analytical approach just by means of one of the magnetic field components. In this study, the Shafranov equilibrium parameter was estimated by means of the poloidal magnetic field experimental data, measured by the Damavand tokamak magnetic probes.

In this paper، the acceleration of an electron in the interaction with a plasma wave and a magnetized ion-channel is analyzed. The electron dynamics is studied treated employing complete three-dimensional Lorentz force equations. A relativistic three dimensional single particle code is used to obtain the electron-trajectories. The results of numerical calculation show that the electrons can be accelerated in the magnetized channel. Furthermore، the electron energy gain with axial magnetic field is compared to that without axial magnetic field.