Iranian Journal of Physics Research
Year:2017 | Volume:17 | Issue:1 |Papers Count:17

Studying the production or decay processes of heavy quarkonia (the bound state of heavy quark-antiquark) is a powerful tool to test our understanding of strong interaction dynamics and QCD theory. Fragmentation is the dominant production mechanism for heavy quarkonia with large transverse momentum. The fragmentation refers to the production process of a parton with high transverse momentum which subsequently decays into a heavy quarkonia. In all previous manuscript where the fragmentation functions of heavy mesons or baryons are calculated، authors have used the approximation of a Dirac delta function for the meson wave function. In the present paper by working in a perturbative QCD framework and by considering the effect of meson wave functions we calculate the fragmentation function of a gluon into a spin-triplet S-wave charmonium J/psi. To consider the real aspect of meson bound state we apply a mesonic wave function which is different of Dirac delta function and is a nonrelativistic limit of the Bethe-Salpeter equation. Finally، we present our numerical results and show that how the proposed wave function improves the previous results.

In this paper، the optical properties of the quantum double folded potential well in the terahertz frequency region are investigated. The Schrö dinger equation is solved and using the obtained wave functions، the standard density matrix and the iterative method the refractive index and the absorption coefficient in the first order is calculated and investigated. The results show that for the proper choice of the parameters، the maximum absorption could lie in the terahertz range that is appropriate for use in terahertz devices. Furthermore، the effects of small potential disturbances on frequency absorption coefficient and thus the stability of the system are studied. The results of these calculations show that for small fluctuations the maximum absorption remains in the terahertz range، but by increasing the disorder، this maximum gradually increased and move toward infrared frequencies.

Using three cluster model، the ternary fission of (_"98" ^"252" )Cf is studied. We applied collinear and equatorial configurations to study the ternary fission of (_"98" ^"252" )Cf when three fragments are Sn، Ni and Ca. The potential energy of collinear and equatorial configurations is calculated. We calculated the potential energy for odd and even values of A3. Also، we compared the potential energy for (_"50" ^(A_"1" ))Sn+(_"28" ^(A_"2" ))Ni+(_"20" ^(A_"3" ))Ca and (_"50" ^(A_"1"-"1" ))Sn+(_"28" ^(A_"2" +"1" ))Ni+(_"20" ^(A_"3" ))Ca to investigate the influence of neutron numbers of three fragments. Obtained results show that for (_"50" ^(A_"1" ))Sn+(_"28" ^(A_"2" ))Ni+(_"20" ^(A_"3" ))Ca reaction with even A3 in collinear and equatorial configurations، the potential energy and penetration probability have، respectively، minimum and maximum values in A3=48 whereas for odd values of A3 the minimum value for the potential energy and the maximum value of penetration probability take place in A3=49. For (_"50" ^(A_"1"-"1" ))Sn+(_"28" ^(A_"2" +"1" ))Ni+(_"20" ^(A_"3" ))Ca reactions in collinear and equatorial cases، the minimum value of potential energy and maximum value of penetration probability take place in A3=49 and A3=50، respectively، for even and odd values of A3. Also، among all the possible reactions the lowest value of potential energy and highest value of penetration probability happen for (_"50" ^132)Sn+(_"28" ^72)Ni+(_"20" ^48)Ca configuration.

Thermoluminescence material LiF: Mg، Cu، P was produced using standard GR200 dopant concentrations and its emission and absorption spectrums was measured after beta irradiation. The alterations resulting from various thermal treatments، excessing the recommended temperatures namely 240º C on the emission and absorption spectrums has been investigated. The main peak of absorption spectrum، which is relevant to F centers، don’ t exhibits any difference to the absorption spectrum of LiF: Mg، Ti، which in turn demonstrates the dominant function of F centers in formation of trap centers in both TL materials. The TL Material LiF: Mg، Cu، P is sensitive to the temperatures higher than 240º C and the results show that main peak of absorption spectrum shifts to lower wavelength with increasing the temperature to 400º C. Furthermore the investigation of TL sensitivity from LiF: P at temperatures above 240º C confirms the role of P impurity in sensitivity reduction from LiF: Mg، Cu، P at temperatures higher than 240º C.

In this paper، with respect to the advantages of geometric phase in quantum computation، we calculate the geometric phase of the optomechanical systems. This research can be considered as an important step toward using the optomechanical systems in quantum computation with utilizing its geometric phase.

We investigate harvesting electrical energy from Gaussian white، Gaussian colored، telegraph and random phase-random amplitude (RARP) noises، using linear and nonlinear electromechanical systems. We show that the output power of the linear system with one or two degrees of freedom، is maximum for the Gaussian white noise. The response of the system with two degrees of freedom is widened in a larger frequency domain compared to that of a single degree of freedom system. A nonlinear system generates more power than a linear one.

In this article، organic light emitting diode with the two structures of ITO / PEDOT: PSS /PVK/Alq3/PBD/Al and ITO/PEDOT: PSS/PVK: Alq3: PBD/Alwith different concentrations were fabricated. The effects of concentration of Alq3 complex on the characteristics of diodes، which were made، were studied. Layers with the same weight percentages PVK، PBD and different wt. %Alq3 by spin coating on PEDOT: PSS layer was deposited. Current-voltage characteristic curve-and luminescence (El) were studied. Experimental results showed that by increasing the concentration of the Alq3complexin both structure، luminescence increased and the operating voltage is reduced.

Boron neutron capture therapy (BNCT) is an effective method for treatment of deep seated brain tumors. This method consists of two stages: injection of boron compound in the patient body، and then irradiation of the region tumors with the neutron beam. It allows for delivery of high linear energy transfer (LET) radiation (particles 4He and 7Li nuclei) to tumors at the cellular level whilst avoiding unnecessary dose deposition to healthy tissue. The proper neutron energies for BNCT is 1eV– 10keV، namely epithermal energy range. Neutrons can slow down to the thermal energies via passing through the different tissue before reaching the tumor. Neutrons with higher or lower energies and &gamma-radiation are extremely undesirable and should be avoided as much as possible of the spectrum. Therefore، a good spectrum shaping is an essential requirement for BNCT. The following neutron-producing charged particles reactions are considered mainly for use in accelerator based neutron capture therapy: 7Li(p، n)7Be، 9Be(p، n)9B، 9Be(d، n)10B and 13C(d، n)13N. The 7Li(p، n)7Be reaction is excellent for producing neutron. Neutrons from this reaction have a relatively narrow energy spectrum which requires less moderation than those generated from other reactions. In this paper، we investigate the feasibility of using 7Li(p، n)7Be reaction with irradiation of 2. 5MeV-20mA proton beam for neutron production in order to treatment deep seated brain tumors. the serious drawback of this source is the low melting point of Li target (180 ° C) and its low thermal conductivity (84. 7 W/m ° k). To overcome this problem، a cooling system was optimized and a beam shaping assembly (BSA) was proposed for decreasing of the flux of fast neutrons (E>10 keV). The proposed BSA based on 7Li(p، n)7Be reaction contains: BeO as moderator، graphite as reflector، Cd as thermal neutron filter and BeO as collimator. Our results show 1. 08×109 n/cm2s epithermal neutron flux at the beam port of the proposed BSA. Although the designed beam meet IAEA criteria، however، considering the differences between skin and healthy tissue in BNCT leads to high neutron dose in skin. To overcome this problem، the BSA is designed so that the dose in skin reduced as much as possible. The simulated Snyder head phantom is used to evaluate dose in tissues due to the irradiation of designed neutron beam. Dosimetric evaluation in the simulated head phantom shows that our designed beam is effective to treat deep-seated brain tumors with the reduction of damage to the skin in a reasonable time. Our optimization is based on Monte Carlo calculation using MCNPX code.

In this research، the capability of new approach of making ridge waveguides in lithium niobate by Argon physical etching and diffusion of titanium is investigated. For this purpose، the proportion of light mode confinement in the ridge section is measured and compared to simulation results. Also the effect of ridge wall defects-which is a challenge of this kind of waveguides-in light power dissipation، is simulated. The ridge height reaches 2. 5µ m and the defects of ridge walls are measured to be about 200nm on average. In this research، by simulation of titanium diffusion and refractive index change of the waveguide it is demonstrated that although the defects exist in the ridge walls، by using appropriate diffusion depth of titanium and refractive index distribution، light power dissipation less than 3 dB/cm can be reached while mode confinement in the ridge section is more than 50 percent.

This paper aims to explore the human mobility pattern by using taxi positioning data in the city of Isfahan. Results show that Lognormal yields the most suitable fit to the data at hand which has been collected from 53000 records throughout Isfahan in a week. Power law did not show acceptable performance and exponential function did not function as good as Lognormal. It was also shown that transportation hierarchy does not sufficiently explain the human mobility pattern. The trip lengths are shown to be 5 and 7 kilometers for working days and holidays respectively. Peak hour trip length distribution function shows lower mean، standard deviation، skewness، and kurtosis compared to the whole day figures.

A coronal loop can be oscillated in various directions. A basic type of coronal loop oscillation is called transverse oscillation that can be caused by different factors، such as nearby active regions and flares. The damping of transverse oscillation may be produced by the dissipation mechanism or the wake of the traveling disturbance. The aim of this paper is to estimate the damping time of transverse (kink) coronal loop oscillations and the quantitative dependence of these oscillations on their frequencies in the solar corona loops that are situated near an active region with the Atmospheric Imaging Assembly (AIA) onboard Solar Dynamic Observatory (SDO). The observed data on 2014-Oct-17، consisting of 130 images with an interval of 24 seconds in the 171 A0 pass band is analyzed for evidence of transvers kink oscillations along the coronal loops and for estimate of physical parameters by fast Fourier transform (FFT) of data times series. In this analyzed signatures of transvers oscillations that are damped rapidly were found، with oscillation periods in the range of P=2-9. 5 minutes. Also، damping times and damping qualities of filtered intensities centered on the dominant frequencies are measured in the range of minutes and، respectively. The observational results of this study indicate that the damping times increase with increasing the oscillation periods، and are highly sensitive function of oscillation period، but damping qualities are not very sensitive to the oscillations period. The order of magnitude of the damping times and damping qualities that obtained from this analysis are in good agreement with previous findings by authors and the theoretical prediction for damping of fast kink mode oscillations.

In the present work has been tried to do a generalized formalism of semi-classical method used in ion-atom impact. One of the current method to calculation of the differential and total cross section for ion-atom impact at high energy range is the first Born approximation because of the simplicity of its calculations، but not necessarily sufficiently accurate. In particular this approximation in the excitation channel take into account orthogonality of the initial and the final state wave functions of the bound subsystem and then disappears inter-nuclear effect in the calculations and offers the poor picture for viewing impact process. Also in this approximation the most important coupling has been considered between the initial and the final state. However the close-coupling method because of some restrictions in high impact energies is unusable. Therefore the aim of this work is correction the first Born approximation by implemented the multi-channel eikonal formalism. At last it will be shown that by simplifying this generalized theory it can be achieved a number of current formalism in terms of ion-atom impact.

Tungsten oxide thin films were prepared by a cathodic electrodeposition method at-0. 450 mV in order to investigate how water content affects their electrochromic properties. FESEM images exhibit that WO3 thin films consist of 65 nm uniform grains. Thin Films were electrochemically investigated in 0. 1M LiClO4 in propylene carbonate electrolyte with and without 5vol% water content by cyclic voltammetry and chronoamperometry. The results indicate that tungsten oxide thin films exhibit faster switching time between coloration and bleaching states and also higher coloration efficiency in hydrated electrolyte.

In this research single phaseLa0. 7(Sr 1-xBax)0. 3MnO3(x =0، 0. 1، 0. 2، 0. 3) nanomanganite with crystalline size of 18-28 nm have been prepared by sol gel method. The structural properties have been studied using X-ray diffraction spectra with its Rietveld analysis and scaning electron microscope images. The magnetic and elctrical properties have been investigated by measuring the ac magnetic susceptibility and resistivity in the presence of magnetic fields in the range of 0-20 kOe. The obtained results from ac magnetic susceptibility show that the Curie temperture of the samples are above room temperture. The results of resistivity show that the metal-insulator phase transition temperture of La0. 7 Sr0. 3 MnO3 and La0. 7 (Sr0. 3 Ba0. 2) MnO3 compounds are below room temperture. The resistivity of the samples strongly decreases and their magnetoresistance almost linearly increases by incrasing the applied magnetic field at different tempertures. The value of magnetoresistance for La0. 7 (Sr0. 3 Ba0. 2) MnO3 Ecompound is 10 % and 14 % at 275 K and 200 K، and for La0. 7 Sr0. 3 MnO3 Ecompound is 13 % and 27 % at 275 K and 100 K، respectively which are suitable for magnetic field sensing applications. The magneto-transport properties of La0. 7 (Sr1-x Bax) MnO3 nanomanganite are described in terms of spin dependent scattering of charge carriers from grain boundaries and their spin dependent tunneling between grains.

We study the problem of a quantum particle in an infinite one dimensional potential well with a moving wall. Based on the effective Hamiltonian approach and using the gauge transformation concepts، we show that the effect of the moving wall appears as an extra phase factor in the wave function which depends on the velocity of the wall.

We investigate adiabatic pumping current in a graphene based normal-insulator-superconductor (NIS) junction with Corbino disk structure. The adiabatic pumping current is generated by two electrostatic potentials، oscillating periodically and out of phase، applied to the insulating and superconducting regions. Using the extended Brouwer’ s formula for the adiabatic pumping current، which is based on the scattering theory، the pumping current is obtained. The results of this calculation show the pumped current oscillates as a function of the barrier strength and it has maximums at resonances with a π /2 phase shift in comparison to the planar NIS junction.

Manganese oxide nanoparticles were synthesized by sol-gel technique. Annealing in 250° C leading to produce Mn3O4. Mn2O3 was obtained by increasing annealing temperature. Potassium permanganate and maleic acid were used to produce MnO2 at room temperature. The structural properties of manganese oxides were investigated by XRD spectrum and the average crystallite size were identified in the range of 38-51nm. The magnetic properties of the samples were studied by VSM. The effect of annealing temperature on the hysteresis cycle showed different χ m for Mn3O4 and Mn2O3.