Showing 6 results for Subject: ph
Azim Aminataei,
Volume 13, Issue 3 (11-2013)
Abstract
In this study, we simulate numerically the process of oxygen mass transport in the human circulatory system incorporating the contribution of axial diffusion. Simulated equation is a time dependent convective-diffusion partial differential equation wherein has applicable application in the bioengineering problems such as boundary layer of fluids, electrical circuits in cables and mass transport problems.
The analytical solution of this kind of equations is complicated. Therefore, the numerical solution for obtaining the approximate solution is important and the convergence and stability in this method of solution, is always a question. In this study, we try to answer the above questions with respect to this special equation and for this we use finite differences.
Hassan Rabani, Mohammad Mardaani, Hamideh Vahid,
Volume 14, Issue 2 (7-2014)
Abstract
In this paper, we study the electronic transport of a multi-molecular chain of copper phthalocyanine connected to two metallic leads by using Green’s function method at the tight-binding approach. The results show that in the gaps of this system, the density of states is independent of the number of molecules or the system length. Moreover, increasing of the system length decreases the tunneling conductance and causes the appearance of peaks and dips in the gaps of the conductance spectra and depending on the value of incoming electron energy, the electron tunneling takes place easier, especially in the edges of the gaps.
H Salehi, Bahaareh Tavakoli Nejad,
Volume 14, Issue 2 (7-2014)
Abstract
In this paper the electronic ,structure and optical properties of strontium sulfide in rocksalt phase have been studied. The calculation have been performed using pseudopotential method in the framework of density functional theory (DFT) by Abinit package.in this calculation we used of localized density approximation(LDA) and generaliezed geradient (GGA) approximation. The obtained result have been good agreement with other theory and experimental results.
Keywords: charge disturibution, density of state, density functional theory, SrS.Keywords: charge disturibution, density of state, density functional theory, SrS.Keywords: charge disturibution, density of state, density functional theory, SrS.Keywords: charge disturibution, density of state, density functional theory, SrS.
Me Azimaraghi, Sn Riazi, Salar Porteamor,
Volume 14, Issue 3 (10-2014)
Abstract
In the present study, we investigate DC conduction mechanism of electron beam evaporated Bromoaluminium phthalocyanine (BrAlPc) thin films using aluminum and gold electrodes. The current-voltage characteristics of sandwich type device are evaluated for the temperature range 298-413K under dark conditions. It is observed that the current passing through the device is increased by increasing temperature at the same voltage in the range of 0-6v. It is found that at lower voltages about 0 to 2v, the current–voltage characteristics demonstrate Ohmic behavior, while the space charge limited current (SCLC) becomes apparent at higher voltages about 2 to 6v, which is restricted by single discrete trapping level. We obtained more than one linear region in the temperature dependence of electrical conductivity. Also, the values of charge carrier mobility and the activation energy of device are evaluated.
Mahmod Bahar, H Golnabi, Mahsima Hamidi,
Volume 14, Issue 3 (10-2014)
Abstract
The aim of this study was to estimate Specific Absorption Rate (SAR) induced in human head tissues, by assuming human head as a cubical model filled with lossy dielectric material and exposed to electromagnetic plane waves. The research is carried out by computational simulation using C programming codes. The numerical technique used in this study was Finite Difference in Time Domain (FDTD) method, along with Perfectly Matched Layer (PML) as an appropriate absorbing boundary condition. Different conditions including exposure conditions as well as physical parameters are employed, in order to compare the results to the past literature. Finally, the penetration depth of one of the specified models is expressed by means of interpolation. The results which are in complete agreement with the others in some cases, suggests that considering the biological tissues as dispersive media, would result in correct estimations whereas changing in the structure of the model, doesn’t differ if precise predictions are not important. Furthermore, the penetration depth correlation to frequency is in line with what is expressed in theoretical papers.
, Ehsan Mir Mehrabi,
Volume 17, Issue 40 (9-2015)
Abstract
Fractional derivatives and integrals are new concepts of derivatives and integrals of arbitrary order. Partial differential equations whose derivatives can be of fractional order, are called fractional partial differential equations (FPDEs). Recently, these equations have been under special attentions due to their most practical usages. In this paper, we survey a rather general case of FPDE, to obtain a numerical scheme, the fractional derivatives in the equation are replaced by common definitions such as Grundwald-Letnikov, Riemann-Liouville and Caputo, to improve the numerical solution, partial derivatives inside the equation are discrete using non-standard finite difference scheme. Then, we survey the stability of numerical scheme and prove that the proposed method is unconditionally stable. Eventually, in order to approve the theoretical results, we use presented technique to solve wave equation with fractional-order that is very practical and widely used in physics and its branches. Numerical results confirm the findings of the theory and show that this technique is effective.
