Electrical conductance in a single wall carbon nanotube (SWCNT): tight binding model
T
Mardaani
author
M
Mardaani
author
text
article
2019
per
In this study, we derive analytically Green’s function (GF) formalism to calculate the electrical conductance for an armchair SWCNT in the ballistic regime. We obtain an exact analytical formula for the conductance of the SWCNT, in the tight-binding approach and assuming nearest-neighbor interaction by recursion process in the GF formalism. We show that in the presence of uniform external potential, the number of conductance channels and resonance energy range of the system decrease.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
4
no.
2019
295
298
http://ijpr.iut.ac.ir/article_833_665a86d7b73e304582e698efebbb33e2.pdf
Investigation of dissipation in a quantum LC circuit
D
Nasr Esfahani
author
F
Kheirandish
دانشگاه اصفهان
author
text
article
2019
per
In this article we consider the resistance of a quantum LC circuit as a heat bath. The heat bath can be modeled by a collection of quantum harmonic oscillators with a continuum of frequencies. By using the minimal coupling method between the circuit and the field describing the environment, the process of energy dissipation and probability transitions between the energy levels of the quantum circuit, are obtained.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
4
no.
2019
299
303
http://ijpr.iut.ac.ir/article_834_b48de22ca3bd7ff8196bb467f10f76f1.pdf
Calibration constant of a silver activation counter used with plasma focus devices
GR
Etaati
author
R
Amrollahi
author
V
Doostmohammadi
author
text
article
2019
per
The silver activation counters are commonly used for pulsed-neutron yield measurements especially in plasma focus devices. The counter normally consists of a Geiger-Muller tube along with silver foils and polyethylene (as a moderator), which is calibrated against an Am-Be radioisotope neutron source. The neutrons, after being slowed-down in the polyethylene, activate the silver foils. By measuring the foil activity with a Geiger-Muller counter, the neutron yield is determined. In the present paper, the activation counter’s calibration constant calculation using the MCNP4C code is explained. The calculated calibration constant is in good agreement with the experimental results.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
4
no.
2019
305
312
http://ijpr.iut.ac.ir/article_835_b87d7c39a190079e744e767ae42a54ec.pdf
Effects of magnetic impurities on electron transmission in a quantum nanoring
L
Eslami
author
M
Esmaeilzadeh
author
text
article
2019
per
In this paper we study the Aharonov-Bohm oscillations of transmission coefficient for an electron passing through a quantum nanoring with two identical magnetic impurities using quantum waveguide theory. It is shown that the Aharonov-Bohm oscillations are independent of the coupling constant between the electron and magnetic impurities for the singlet spin state of impurities, while for the other spin states of impurities the Aharonov-Bohm oscillations decrease rapidly with an increasing coupling constant. For a triplet spin state of impurities, we can use this system as a quantum NOT gate with an efficiency upper than 50% by adjusting the coupling constant between the electron and magnetic impurities and the magnetic flux passing through the ring.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
4
no.
2019
313
320
http://ijpr.iut.ac.ir/article_836_100ecefa5a1a20bf3f217e751ef24fc7.pdf
Production dosimeter LiF: Mg, Ti and comparison its responses with dosimeter LiF: Mg, Ti (TLD-100) in Harshaw company against of gamma rays
KH
Mohammadi
author
R
Sarraf Maamory
author
R
Mohammadi
author
A
Mosavi Zarandi
author
text
article
2019
per
Thermoluminescence dosimeters are small tablets used with 3. 2*3. 2*0. 9mm^3 for measurement of received dose from radioactive various beams. The most common dosimeter is TLD-100 which is lithium-fluoride family and this dosimeter contain magnesium impurities. In this study, first lithium-flouride powder was mixed with titanium and controlled atmosphere samples were heated. After measuring of samples density and hardness, their glow curves were drawn and microscopic pictures of producted samples were provided. Of course, the reader should know that the best press pressure, the best range of temperature heating and the best range of samples heating were determined in 6-8 (ton/cm2), 775-800 ° C and 15-20 h, respectively [1]. Then, the response of producted TLD-100 under radiation of gamma sources, 60Co, was measured in 500 mSv rate and obtained values were compared with obtained values by Harshaw producted samples. Dosimetry characteristics of producted samples was evaluated according to ASTM E 668-00, IEC-ISO 1066 standards. The results of comparisions indicate good agreements between producted sample and Harshaw sample.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
4
no.
2019
321
327
http://ijpr.iut.ac.ir/article_837_12b34647e086ebebc167a61b9d06ced7.pdf
Effects of interfacial potential smoothness on reflectivity, phase, and polarization of reflected neutrons from magnetic films in neutron reflectometry
SS
Soyouf Jahromi
author
SF
Masoudi
author
text
article
2019
per
In the past decades, neutron reflectometry have flourished as an applicable method to the study of thin films. As an example, the type and thickness of an unknown thin film which is mounted on top of a magnetic substratum could be determined by measuring the intensity and polarization of the reflected neutrons from the sample. Neutron reflectometry is based on solving the one dimentional schrödinger equation and determining the reflection coefficient at two distinct boundaries. In this paper by considering three smooth varying potential (linear, eckatrt and error function), we have investigated the effects of continuity of interfacial potential on determination of reflectivity, phase and polarization of reflected neutrons from the sample.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
4
no.
2019
329
335
http://ijpr.iut.ac.ir/article_838_4257511284427ebc5a9b80e07cc11164.pdf
Josephson junction between two high Tc superconductors with arbitrary transparency of interface
GhR
Rashedi
author
text
article
2019
per
In this paper, a dc Josephson junction between two singlet superconductors (d-wave and s-wave) with arbitrary reflection coefficient has been investigated theoretically. For the case of high Tc superconductors, the c-axes are parallel to an interface with finite transparency and their ab-planes have a mis-orientation. The physics of potential barrier will be demonstrated by a transparency coefficient via which the tunneling will occur. We have solved the nonlocal Eilenberger equations and obtained the corresponding and suitable Green functions analytically. Then, using the obtained Green functions, the current-phase diagrams have been calculated. The effect of the potential barrier and mis-orientation on the currents is studied analytically and numerically. It is observed that, the current phase relations are totally different from the case of ideal transparent Josephson junctions between d-wave superconductors and two s-wave superconductors. This apparatus can be used to demonstrate d-wave order parameter in high Tc superconductors.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
4
no.
2019
337
340
http://ijpr.iut.ac.ir/article_839_1df647f14b1af1372db19e2f2ec96194.pdf
Time dependent solutions of the nonlinear Fokker- Planck equations related to arbitrary functions of Tsallis entropy
F
Rezaei
author
B
Mirza
author
B
Mirza
author
text
article
2019
per
The nonlinear Fokker-Plank equations can be related to generalized entropies. We investigate the stationary solutions of Fokker- Plank equations which are related to entropies defined as arbitrary functions of Tsallis entropy. Also the transient solutions of the equations are determined for linaer drifts.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
4
no.
2019
341
347
http://ijpr.iut.ac.ir/article_840_01ecbd10f9a7dca34055d555d098e7a8.pdf
Field analysis of TE and TM modes in photonic crystal Bragg fibers by transmission matrix method
M
Hosseini Farzad
دانشگاه شیراز
author
N
Yazdanpanah
دانشگاه پیام نور شیراز
author
text
article
2019
per
In this article, we considered the field analysis in photonic crystal Bragg fibers. We apply the method of transmission matrix to calculater the dispersion curves, the longitudinal wave number over wave number versus incident wavelength, and the field distributions of TE and TM modes in the Bragg fiber. Our analysis shows that the field of guided modes is confined in the core and can exist only in particular wavelength bands corresponding to the band-gap of the periodic structure of the clad. From another point of view, light confinement is due to Bragg reflection from high-and low-refractive index layers of the clad. Also, the diagram of average angular frequency with respect to average longitudinal wave number is plotted so that the band gap regions of the clad are clearly observed.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
4
no.
2019
349
355
http://ijpr.iut.ac.ir/article_841_cf7fc97c4154ac0e2dcc35e317da76dc.pdf
The role of electroweak penguin and magnetic dipole QCD penguin on hadronic b Quark Decays
H
Mehrban
دانشگاه سمنان
author
text
article
2019
per
This research, works with the effective Hamiltonian and the quark model. Using, the decay rates of matter-antimatter of b quark was investigated. We described the effective Hamiltonian theory which was applied to the calculation of current-current (Q1,2), QCD penguin (Q3,…,6), magnetic dipole (Q8) and electroweak penguin (Q7,…,10) decay rates. The gluonic penguin structure of hadronic decays b→qkg→qkqiqj was studied through the Wilson coefficients of the effective Hamiltonian. The branching ratios of the Tree-Level, effective Hamiltonian, effective Hamiltonian including electroweak penguin, effective Hamiltonian including magnetic dipole and the effective Hamiltonian including electroweak penguin and magnetic dipole b quark decays b→qiqkqj, qi{u,c}, qk{d,s}, qj{u,c} have been calculated. It was shown that, the electroweak penguin and magnetic dipole contributions in b quark decays are small and current-current operators are dominated.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
4
no.
2019
357
357
http://ijpr.iut.ac.ir/article_842_49861d65a24c5a80b38cd6e19dba5aad.pdf
Magneto-Optical properties of GaP single crystal
MS
Omar
دانشگاه صلاحالدین عراق
author
TA
Abbas
دانشگاه صلاحالدین عراق
author
text
article
2019
per
The temperature dependence of magneto-optical and magneto-photoconductivity measurements were carried out in the range of (200-330) K. A home made optical cryostat was used for the measurements. The measured room temperature value of the energy gap was found to be 2.211 eV. The temperature coefficient of energy gap was found to be -5.48×10-4 eV/K obtained by the optical absorption method and -4.90×10-4 eV/K from the measurements of photoconductivity. The magnetic field coefficient of energy gap was found to be temperature dependent with values of 1.34×10-3 eV/Tesla at 202 K and 2.67×10-3 eV/Tesla at room temperature, when the field used was up to 2.2 Tesla. The reduced effective mass of carriers are also calculated from both techniques and found to be changing from 0.034 m0 to 0.021 m0 when magneto-optical data was used in the calculations and from 0.052 m0 to 0.032 m0 when magneto-photoconductivity data was used as the temperature changed from 220 K to 330 K respectively.
Iranian Journal of Physics Research
https://www.psi.ir/physics_society_iran_1_home
1682-6957
9
v.
4
no.
2019
358
358
http://ijpr.iut.ac.ir/article_843_79f879d63f13031e4a93352723efa230.pdf