نشریه پژوهش سیستم های بس ذره ای
سال یازدهم شماره 3 (پیاپی 30، پاییز 1400)

The destructive effects of high-energy hydrogen and argon ions irradiated in the MTPF-2 Mather type plasma focus device on the surface and structural properties of graphite were investigated. Raw and irradiated samples were analyzed using a Scanning Electron Microscope. While microscopic images of samples irradiated with hydrogen ions point sputtering, pores are seen on the samples' surface along with spot melts, the predominant phenomenon on the surface of samples irradiated with argon ions is sputtering of particles from the graphite surface. X-ray diffraction analysis was used to investigate the changes caused by the irradiation of high-energy protons and argon ions on the graphite structure. In the X-ray diffraction spectrum of the irradiated samples, the peaks' displacement, and the change in the peaks' intensity compared to the X-ray diffraction spectrum of the reference sample were observed. The peak of the graphite sample's locations irradiated with hydrogen and the sample irradiated with argon have been shifted to smaller angles. The displacement of the peaks in the proton-irradiated sample is higher than that of the argon ions. The argon ion and hydrogen ion beam specifications were calculated using the Lee code.

Half-metallic, thermoelectric, and also thermodynamic stability of CoXMnSi (X = Rh, Tc) quaternary Heusler compounds were performed by density functional theory calculations. These compounds have an equilibrium volume with the lattice constants of 5.81 and 5.77 Aᵒ for CoRhMnSi and CoTcMnSi, respectively, which is consistent with the other functions. Moreover, the bulk moduli of these compounds have been calculated to be 225.8GPa and 242.5GPa, respectively, which indicates their very high crystalline hardness. Thermodynamic phase diagrams confirmed the thermodynamic stability of these compounds. Electronic calculations show half-metallic behavior with 100% spin polarization at the Fermi level for both compounds. The CoRhMnSi has 0.65eV and 0.72eV, and CoTcMnSi has 0.22eV and 0.51eV spin gap in minority spin when applying the GGA and GGA+U approximations, respectively. Also, the study of thermoelectric properties shows that these compounds with a figure of merit index of 0.99 at room temperature are suitable candidates for thermoelectric purposes, which is in agreement with other works.

In this paper, we assume that the core of the neutron star consists of nucleons, leptons, and hyperons. We investigate the equation of state of neutron star matter using the LOCV method with AV18 potential,, TNI and also excluded volume effect (VE). We obtain the mass-radius relation of twin neutron stars in the presence of hyperons. The obtained results demonstrate that the threshold density of sigma hyperon lies in the range of (0.243-0.552) fm^-3 and that of lambda hyperon exists in the range of (0.353-0.940) fm^-3 . It is obvious that the appearance of hyperons softens the equation of state of neutron star matter, which is largely compensated by considering the radius for nucleons. The comparison of the results obtained for the mass-radius relation of neutron stars shows that the presence of hyperons using potential reduces the maximum mass of neutron stars from 2.11 to 1.12 M_sun . However, this parameter reaches the value of 1.5 M_sun by including the VE which indicates stiffening of the equation of state. In addition, excluded volume effect leads to instability after the appearance of hyperons, which implies the existence of a twin neutron star, two stars of the same mass but different radii.

In this paper, propagation of electromagnetic waves in a cylindrical waveguide with two different regions and with circular cross-section is investigated. The incident wave in symmetric mode TM0j is sent from the first media to the second media which the first is a filled loss-free dielectric semi-bounded metallic waveguide. The second region of the waveguide is a metallic waveguide with a plasma rod which is isolated by a thin dielectric layer from the metallic wall of the waveguide. The considered plasma rod in the waveguide is assumed in warm approximation. The generation of the new modes for reflected and transmitted waves investigated and by using the mode matching technique, the reflection and transmission coefficients are obtained as a function of the temperature of plasma charged carriers. It is shown that the reflected and transmitted waves have phase difference with respect to the incident wave. The graphs of reflection and transmission coefficients and so the graphs of their phase difference for some elementary modes in terms of the variations of the plasma temperature are presented.

In this study, microstructural and magnetic evolution of nanostructured (Fe50Co30Ni20)90Cu10 alloy prepared by mechanical alloying are investigated. The structural and magnetic properties have been evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The powder morphology shows that for the powders at the final part of milling time, the particle size distribution falls into a narrower range compared to the powders at the initial time. X-ray diffraction results indicate that, with increasing milling time, the peak broadening of the elements become wider. During mechanical alloying process, after 32 h, two low values of crystallite size are happened. The most dissolved of cobalt, nickel and copper elements are occurred after 16 h of milling time. However, at the last part of the milling time, the crystallize size and lattice strain reaches to about 29.12 nm and 0.221 % respectively. The variation of crystallite size enhances magnetization saturation to about 127.26 emu/g and increases coercivity to approximately 82.86 Oe for milling time of 2 and 48 h, respectively. This alloy exhibits much softer magnetic behavior compared to the Fe50Co30Ni20 alloy reported in the recent work [15].

In this paper, a charged AdS black hole is considered and exponential corrections on entropy ‎are studied for it. Next, thermodynamic quantities of this black hole, including mass, ‎temperature, heat capacity, as well as pressure and Gibbs free energy, are investigated. Then, ‎the thermodynamic geometry of this black hole is investigated using the geometric methods of ‎Weinhold, Ruppeiner, Quevedo, HPEM and NTG. In addition, the correspondence between ‎singularities of the scalar curvature of these metrics and the black hole phase transition points ‎is investigated. It has been observed that Quevedo (II), HPEM and NTG formalisms provide ‎more information about the phase transition of this black hole compared with Weinhold, ‎Ruppeiner and Quevedo (I) formalisms.‎

In order to show the effects of different degrees of expansion of the imaginary time propagation operator on convergence, the imaginary time propagation method is used, for example, for a simple harmonic oscillator. Considering the potential energy, the wave function of the ground state of the system as well as the wave function that is close to the wave function of the ground state of the system can be seen that each time the imaginary time operator is applied, the wave of initial guess function approaches the wave function of the ground state of the system. Examining the different levels of expansion of the operator, it can be seen that the higher the level used, the less repetition of the operations of this operator to reach the wave function of the base state of the system. The Monte Carlo computational method was used to calculate the integrals. Finally, this method has been tested on the hydrogen atom to investigate the physical problem.

Remote spectroscopy of material plasmas can be used well to detect and identify the material identity especially the explosive and organic materials. The plasma can be generated either through the applying high power density laser radiations or high DC voltages in the vacuum circumstance. In this paper, to generate the material plasmas, a high DC voltage of 2 kV was applied in the T-shaped lamp with argon atmosphere. The plasmas of two explosive materials of TNT and picric acid and two organic materials of 4-nitrobenzoic acid and 3,5-dinitrobenzoic acid in quantities of 35 mg were at first generated and then their spectra were measured from distances of 1.55, 2, and 2.31 meters. The spectra of material plasmas ranged from 200 nm to 800 nm consisting of lines C2, H, O, N, and Ar. The limit-of-detection from a distance of 2 m was determined consequently. Finally, with the use of two methods, the explosive materials were distinguished from the organic ones and the calibration curve was also prepared.

In the present study, Fe-doped ZnO (Zn1−xFexO) thin films were deposited by simple chemical spray pyrolysis technique on glass substrates at substrate temperature of 300 °C. The effect of Fe-doping concentration on the structural, morphological and optical properties of deposited films was studied. The X-ray diffraction (XRD) analyses indicates that all the obtained samples have a hexagonal wurtzite crystal structure without any secondary phases. The atomic force microscopy (AFM) images show that the morphology features changes with the increase of Fe-doping concentration and a denser microstructure and smoother surface obtained. The Fourier transform infrared (FTIR) spectra shows the presence of the stretching vibration mode of ZnO, functional groups, chemical bonding and iron in the doped ZnO thin films. Optical studies indicate that the absorption edge of deposited film shifted towards higher-wavelength direction and their optical band-gaps are decreased with the increase of Fe-doping concentration.

Today, polyvinyl chloride (PVC) is used in the automotive industry, production of flooring and building facades, water and wastewater pipes, electronic circuits, etc. Considering the non-biodegradability of polymers, PVC products are produced and accumulated as polymer waste. One of the methods for recycling polymers with minimal destruction of chemical structure is the plasma treatment. In this study, the effect of hexafluoride sulfur plasma on recycled PVC at different times and pressures is investigated. The best exposure time was obtained a 5 and 10 minute for possess a hydrophobicity surface at a pressure 0/16 torr of the plasma processing chamber, in which case the contact angle was 101 °. The electrical resistivity analysis showed that modifying the surface of PVC samples by plasma Sulfur hexafluoride at a certain pressure and time would increase the electrical resistance of their surface.

Fluorine adsorption on graphene adjusts its band gaps, therefore fluorinated graphene is one of the functional compounds in the electronics industry. In this paper, we investigate the process of melting, fluorine desorption and structural changes due to increasing temperature in single-sided and both-sided fluorinated graphene within molecular dynamics theory and compare the results with the same configuration of hydrogenated graphene structures. Our results reveal that the transition phase from solid-state to the molten state in both-sided fluorinated graphene is accompanied by the formation of polymer chains of carbon and fluorine atoms if the concentration of fluorine atoms extend beyond 50%. In contrast, the results show that in single-sided fluorinated graphene the fluorine atoms are desorbed from the graphene surface, before the beginning of the transition phase. Our calculations also indicate that, unlike two-sided fluorinated graphene structures, the structural changes caused by the increase in temperature in single-sided and both-sided hydrogenated graphene are similar to that of single-sided fluorinated graphene, but at a lower temperature.

We will consider a toy model of generalization of three-dimensional (3D) gravity in the presence of higher curvature corrections known as extended new massive gravity (ENMG). By employing the Wald approach in the context of covariant phase space formalism, we compute the conserved charges of 3D rotating black holes in ENMG. In fact, we will obtain exact expressions for the mass and angular momentum of two kinds of rotating black holes the so called Banados-Teitelboim-Zanelli (BTZ) and warped anti-de Sitter (WAdS3) black holes. We show that these physical quantities not only satisfy the Smarr-like formula for the mass of a black hole but also fulfill the first law of black holes thermodynamics.