مجله پژوهش فیزیک ایران
سال سیزدهم شماره 4 (زمستان 1392)

In this study، 1200 images and catalogues of M33 spiral galaxy taken by WFCAM camera at UKIRT telescope in J، H and K bands. Cross correlation methods were employed to identify stars in overlapping regions from among images taken in different dates. Careful astrometric and photometric analysis was made to calibrate stellar positions and magnitudes using their 2MASS near infra red survey. The final catalogue consisted of 445303 stars and covered more than 0. 75 square degrees of sky centered on M33 core، which included the bulge and spiral arms. This is the biggest catalogue ever made from a nearby spiral galaxy in near infrared. A color magnitude diagram in near infrared was plotted، which shows a bunch of very red stars that extended to J-K = 4.

In this study، the noncommutative problems of quantum mechanics in the presence of the classical gravitation field are investigated. It is shown that spaectime will fail by Schwarzschild metric، and classical response to the gravitational field، will be equal to the change in the geodesic derivation equation

In the present work، anodized aluminum oxide template was prepared by accelerated mild anodization technique in 0. 6M phosphoric aside and 175 V، anodization voltage. Pore widening was performed by chemical etching in 0. 5M phosphoric acid for 8، 16، 32، 40 minutes. Scanning Electron Microscopy (SEM) images showed the pores، diameter exponentially increases with etching time. By depositing silver contacts on the prepared samples and using an RC circuit for applying impedance spectroscopy، the characteristics of the humidity sensor based on constructed samples were investigated. The maximum response was seen for the sample etched for 40 minutes. For this sample، the detectable threshold of relative moisture was 30% and the response and the recovery time were 8، 2 seconds، respectively

In this paper، in order to study a nonlinear dissipative cavity a linear master equation of the cavity in generalized to a nonlinear one at zero temperature. Then، it is shown that nonlinear coherent states are the only preferred states of the system under decoherence

There is a kind of composite materials made up of noble metal nanoparticles (such as gold، silver، copper) and a dielectric material (such as silica) with unique properties. In this paper، using Strong Permittivity Fluctuation Theory (SPFT) method، the coefficient of effective permittivity and the effective susceptibility coefficient are calculated for combining glass with metal nanoparticles، assuming that the nanoparticles are spherical. Coefficient of effective permittivity and the effective susceptibility index are estimated for the sample of homogeneous composite materials. And the results of this study are compared with experimental results and other models. It is observed that the data obtained for the zero-order estimate do not match the experimental results. By appropriate correlation length for the second- and third-order، specially for the second-order estimate of SPFT method، conformity between results can be established. Therefore، it can be concluded that SPFT method is betler than other models for calculating and improving the properties of the non-linear model.

In this paper، construction of triplet atmospheric plasma jet using argon، air، oxygen and nitrogen gases is reported. Bactericidal effect of the plasma jet is also investigated. To that end، longitudinal geometric configuration for the electrodes was chosen because it would increase the jet length. Electrical characteristics، jet length dependencies on the applied voltage and gas flow rate were decided، experimentally. Relative concentrations of chemical reactive species such as ozone، atomic oxygen، NOx compounds and hydroxyl were measured using optical emission spectroscopy. It was seen that atomic oxygen and ozone concentrations with triplet plasma jet are more than the concentration of single plasma jet. Triplet plasma jet was also used for sterilization of solid and liquid surfaces to disinfect gram-negative and gram-positive Escherichia coli and Streptococcus pyogenes bacteria. The results verified the effectiveness of the triplet plasma jet for killing bacteria.

In the present work، first an analytic relation for position-dependent effective mass in a quantum rod is obtained. Then، the effect of position-dependent effective mass on the intersubband optical absorption coeffcient and the refractive index change in the quantum rod is examined. Our numerical calculations are performed using both a constant effective mass and the position-dependent effective mass. We calculate the linear، nonlinear and total intersubband absorption coeffcient and refractive index change as a function of the incident optical intensity and structure parameters such as rod length and rod radius. The results obtained from the present work show that spatially varying electron effective mass plays an important role in the intersubband optical absorption coeffcient and refractive index change in a quantum rod.

As the input of MCNP code (Monte Carlo N - Particle code system)، a monoenergetic and isotropic point source with the energy rangeg from 0. 3 to 10 MeV was placed at the center of a spherical material surrounded by another one. The first shielding material was water and the second one was lead. The total thickness of the shield varied between 2 to 10 mfp. Then، using the output of MCNCP، exposure build up factor was calculated. The MCNP computed data were analyzed by plotting the buildup factor as a function of each independent variable (energy، first material thickness and second material thickness) and observing the trends. Based on the trends، we examined many different expressions with different number of constants. By MINUIT the FORTRAN program، the constants were calculated، which gave the best agreement between the MCNP-computed exposure buildup factors and those obtained by the formula. At last، we developed a polynomial formula with 11 constants that reproduced exposure buildup factor with a relative error below 2% (in comparison with the MCNP result).

In this paper، an analytic treatment of electroweak phase transition is proposed within the two-Higgs doublet model. This phase transition occurs in one stage and is strongly first order. Therefore، it can be applied to the electroweak baryogenesis scenario، whereas the standard model cannot provide this condition considering the experimental data. Also، we study CP violation which is one of the necessary conditions to baryogenesis within the two-Higgs-doublet model.

This paper deals with the role of fast ignitor in fast-shock ignition (FSI) concept. The semi-analytical model indicates that the FSI target gain is a function of fast ignitor laser wavelength. If the energy of fast ignitor driver is and the laser wavelength is less than 0. 53 micron، then with a fuel mass about 2 mg the FSI has a considerable advantage over pure shock ignition and the figure of merit is better than 1. 2. When the wavelength of fast ignitor becomes shorter، the approaches، and for wavelengths shorter than 0. 25 micron no additional is advantage is obtained.

In this paper، a generalization of the Kuramoto model is introduced by explicit consideration of deterministically time-varying periodic external force. In this model، the oscillator''s natural frequencies and amplitude of collective oscillations are influenced by external forces with constant or random strengths. Then، the synchronization behavior of forced Kuramoto model is studied in some complex networks. In the model، a new collective dynamics behavior is observed، i. e.، all the oscillators are synchronized at one second، and after a little time، all of them become unsynchronized. Also، a distinct behavior of small-world networks is observed. When the strength of external force has a bimodal distribution، a resonant behavior in small-world network is seen.

In this paper، modulation bandwidth characteristics of InGaAs/GaAs quantum dot (QD) laser were theoretically investigated. Simulation was done by using the fourth order Runge-Kutta method. Effect of carrier relaxation life time، temperature and current density on characteristics of tunneling injection QD laser (TIL) and conventional QD laser (CL) were analyzed. Results showed that tunneling injection in QD laser increases the modulation bandwidth indicating that it is very useful for using in the fiber optic communication systems.