JOURNAL OF SCIENCES (ISLAMIC AZAD UNIVERSITY)
Year:2008 | Volume:18 | Issue:67 (PHYSIC ISSUE)|Papers Count:9

Ion implantation technique has emerged as an efficient tool in material surface engineering. In this work, Titanium is bombarded by 30 keV nitrogen ions and different implantation doses in the range of 5x1017 to 5x1018. AFM analyses of bombarded samples clearly shows significant changes in Ti surface roughness and also phase formation after nitrogen implantation which was characterized by XRD. The corrosion resistance tests were performed by the electrochemical methods in I M H2SO4 solutions at room temperature.

Hot fiament chemical vapor deposition (HFCVD) is a method for deposition technique in nano scale. Electrical, triblogical properties of material can be changed by operation in HFCVD method. HFCVD is suitable method for growth of diamond like carbon (DLC), carbon nanotubes and other carbon nanostructures.

The measurement of current-carrying plasma column displacement is very important for plasma position control. In this paper, calculation and construction of these coils is explained. Multiple moment method has been used and derived for construction of sensing coils & measuring the Horizontal Displacement (H.D.) of plasma column. The comparison of their advantages and disadvantages are investigated.For IR-T1 Tokamak, Two Cosine coils & two Saddle Sine coils were designed and constructed, which have been placed diametrically around minor radius of torus. Then an electronic circuit was designed for adding and integrating the Cosine and Saddle Sine coils output with proper gain. The contribution and gain of each coil in final output is calculated. For compensation of unwanted pickups voltage from the time varying fields such as Vertical, Toroidal, Ohmic, Plasma current, etc. each signal with adjustable gain is added to main signal, until removing the additional field effect. Finally the signal which has been obtained holds good proportionality to H.D.In this circuit, for fast and more accuracy response, high frequency and low offset Op-Amps (Operational Amplifier) are used.

The goal of this research is to evaluate structure and distribution of N – particle systems including electron gas with respect to relative interactions. In this project the quantum density functional theory is used. Which is now days widely used in two classic and quantum forms. Here we use quantum density functional theory for N - particle systems, actually this theory roots in Thomas-Fermi theory with regards to quantum density functional theory. We consider Thomas-Fermi equation theory and related models namely initial TF, TFD, TFD W and TFD - lW model. Wave function or density of rare elements like Ne, Ar, Kr, Xe is calculated from general equation, then we draw the density with respect to distance for all these elements. As it is shown all these densities have a maximum value in an exact distance from the center of ions so probably the chances of existence of electrons in this distance are more than others.

Sound propagation in sea water has pressure variations. Water, Magnesium sulfate and Boric acid molecules response to this pressure variation and attenuate the sound during a relaxation process. In some models, absorption is a function of ocean variables and frequency. Besides, we see special sound absorption equations for each region. In this paper we introduce a relation for sound absorption for northern part of the Persian Gulf. Due to this relation, we have a low absorption in this region which will be neglected. In this region, Water and magnesium sulfate relaxations are effective in absorption.

Based on the pressure and energy balances on the Keyhole's "Wall", an algorithm constructed to determine the temperature profile in the melt-pool and plasma-phase leading to an investigation of geometrical shape of the hole.The heat transport equation for the liquid and the plasma phase, in the Finite Difference Approximation, restricted to well define boundary conditions are given in same details and solved properly.The heat loss of the system must be calculated to fulfill the boundary conditions; however the heat flux density is a function of Tl and nl, both given in terms of the Match number, which in turn depends on the temperature. Therefore, the calculation has an iterative character.Geometrical structure of the Keyhole is represented by a family of the well- known Bessel function. The Rosenthal solution is used in this model. The results are given in the forms of some diagrams. The results for CO2 laser with 4 and 10 killo watt power have been obtain.

The energy-gap of the heisenberg two-leg ladder in the presence of a magnetic field is studied. The ground state phase diagram cosists of rung-singlet, luttinger liquid and saturated ferromagnetic phases. By using the finite-size scaling method, the critical saturation field is computed. Numerical results show that the mentioned transition is in the universality class of the Ising model in the Transvers field.

Today, computational acoustics is one of major branch of underwater acoustics that play important role in the advanced laboratories in the world. It is important due to high financial cost of operational tests in the water. There exist many numerical methods in this field that among them only, ray tracing, normal modes, fast field programming and parabolic equation method have gained more attention. PE method is a suitable method in low frequencies and shallow water as well as valid for all environments. In this paper, Numerical implementation of PE method based on c++ and MATLAB routines is given over some of well known standard test problems. In the implementation, according to both mathematically and physically complexities of problem, we chose general manner for some of important parameters such as depth and frequency of source, range of receiver, and the whole depth of simulation. Some results show that we have surface and bottom reflections from 4500 meters in range. TL error has a value about 18.4 percent. As increasing source strength from 200 dB, we can eliminate noise effects. TL in stations 1 to 4 in Caspian sea is shown as well as ray simulation in graphs 2, 6, 8, 10.