|
Home>Products>Journal
and Reviews>I.RE.PHY.>Latest
issue
International Review
of PHYSICS - Papers
One-dimensional Solvable Potentials in a Tridiagonal Representation
Space
by E. El Aaoud, H.
Bahlouli, A. D. Alhaidari
Abstract - We use
variable transformation from the real line to finite or semi-infinite
spaces where we expand the regular solution of the one-dimensional
time-independent Schrödinger equation in terms of square integrable
bases. We also require that the basis support an infinite tridiagonal
matrix representation of the Hamiltonian. By this requirement, we deduce
a class of solvable potentials along with their corresponding bound
states energies and stationary wave functions, expressed in terms of the
square integrable basis set. This approach allows for simultaneous
treatment of the discrete (bound states) as well as the continuous
(scattering states) spectrum on the same footing. The problem translates
into finding solutions of the resulting three-term recursion relation
for the expansion coefficients of the wavefunction. These are written in
terms of orthogonal polynomials, some of which are modified versions of
known polynomials. The examples given, which are not exhaustive,
illustrate the power of this approach in dealing with one-dimensional
quantum problems.
Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords:
Bound and continuum states, orthogonal polynomials, recurrence
relations, square integrable bases, tridiagonal representations.
Effective
Hamiltonian for a Two-Level Atom Interacting with Two Fields
by J. L.
Escudero-Jiménez, R. Juárez-Amaro, R. Mar-Sarao, H. Moya-Cessa
Abstract - We study
how effective Hamiltonians may be produced for the interaction of a
two-level atom and a quantum and a classical field. We use a method
recently introduced that produces a small rotation to the Hamiltonian
which in turn allows to neglect some terms in the rotated (effective)
Hamiltonian. We proceed by studying the dynamics of this system by
looking at the probability to find the atom in its ground state, which
shows small amplitude revivals and by means of the Q-function.
Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords:
Two-level atoms, effective Hamiltonians.
Abstract
-
Dust particles appear on the edge of the tokamak plasma as a result of
disruptions and plasma interactions with divertor plates, limiters, or
blankets, as well as of pellet injections. The transport of dust in
plasmas may play a significant role in the performance of next step
tokamaks such as ITER, appropriate fluid model equations for the
nonlinear interchange mode in a dusty plasma are derived, accounting for
the attachment of electrons and ions, as well as for their scattering by
the dust particulates, and the symmetry breaking between the electron
and ion densities due to the dust charging. In this paper we consider
some aspects of the dust dynamics in ITER plasmas, and we presented a
theoretical and numerical study of the evolution of sheath width of the
scrape-off layer (S.O.L.) by using computer simulations.
Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords:
dust particles, tokamak plasma, ITER, fluid model, sheath width,
scrape-off layer.
Abstract
-
The numerical simulation of the variation of the neutral molecule density
induced by the strong correlation between the dynamics of the electron
gas and that of the neutral gas is studied in a 2-D numerical
modelisation. The energy injection is simulated by a mathematical
function that represents the spatial dependence of the discharge
density. The simulated discharge is a positive point to plane discharge
in a gap = 10 mm, in Nitrogene at atmospheric pressure (760 Torr), with
cylindrical symmetry. The hydrodynamic set of equations, i.e. equations
of transport for mass, momentum and energy, is solved by the flux
corrected transport (F.C.T.) method, in employing the procedure of time
splitting for the two space variables. The space and time distributions
of the fundamental hydrodynamic quantities, density and temperature of
the neutral gas are obtained.
Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords:
Negative-corona discharge, FCT method, Numerical modelling,
Transport equations.
A Comparative X-ray Diffraction and Mössbauer Spectroscopic Study in
Iron Ore Type FeaSibCagMgδMnεAlλ
by A. Benlalli, A.
Djedid, J-M. Greneche
Abstract - Five
samples of Iron ore type FeaSibCagMgMnεAlλ with traces of Phosphorus
and Titanium from El-Ouenza iron ore of Algeria have been studied using
X-ray diffraction (XRD) and Mössbauer spectroscopy at the temperatures
of 77 and 300 K. The XRD diagrams obtained have identified in addition
to Hematite, Goethite, Lepidocrocite and Kaolinite the Calcite and the
quartz two phases without Iron. While Mössbauer spectra reveal hyperfine
parameters highlighting two types of environment, those of Hematite and
Goethite associated to the signature of other low proportions phases.
The results obtained at 77 K are coherent with those at 300 K.
Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords:
Iron Ore, Mineral deposits of El-Ouenza, Mössbauer spectroscopy,
X-ray diffraction.
Comparison
between Mobility Laws on (I-V) Characteristics of GaAs MESFET
by S. Belhour, C.
Azizi
Abstract - We
consider, in this paper, the optimization of the static performances of
a field effect transistor with Schottky barrier of gallium arsenide GaAs
MESFET. After briefly outlining the properties of the material, the
principle of the transistor as well as natural phenomenon that govern
its performance are introduced. Then, we propose a model that describes
the GaAs MESFET static behavior. This model is based on a mathematical
analysis that determines the drain current which takes into account the
effect of the injection of majority carriers in the space charge and the
influence of the mobility on the output characteristics. A comparison is
made on several components for different laws of mobility. The results
show the influence of the mobility law on the output characteristics.
The satisfactory agreement obtained between the experimental and
theoretical results shows the validity of the method.
Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords:
GaAs, MESFET, field effect, transistor, characteristics,
mobility.
An
Accurate Two-dimensional Analytical Subthreshold Swing Model to Study
the Scaling Capability of the Surrounding-gate MOSFET
by F. Djeffal, N.
Lakhdar, A. Benhaya
Abstract - The Surrounding-Gate (SG)
MOSFET has been proposed as a viable option for extending CMOS
scalability beyond 50nm partly due to its immunity to short channel
effects. So, the objective of this work is to provide a two-dimensional
analytical subthreshold swing model for SG MOSFETs at low drain-source
voltage based on an analytical solution of the two-dimensional
distribution-Poisson equation in cylindrical coordinates. It is shown
that the subthreshold swing predicted by the analytical model is in
close agreement with 2-D numerical simulation results without the need
of any fitting parameters. Using this analytical model, we have studied
the scalability limits of SG MOSFETs as function of geometrical and
electrical parameters. The analytical model not only provides useful
physics insight into short-channel effects, but also serves as basis for
compact modeling of SG MOSFETs.
Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords:
SG MOSFETs; device modeling; downscaling; subthreshold swing;
short channel effects
.
Evidence
of Josephson – Like Behavior of Thin Granular Carbon Films
by S. G. Lebedev
Abstract -
This review is described some new results in the studies of anomalous
electromagnetic of thin carbon films. The work presents the study of
some new anomalous electromagnetic effects in graphite-like thin carbon
films. These are: fast switching (10-9 sec) of electrical conductivity;
detection of microwave radiation and its temperature dependence up to
650K; oscillations of film stack magnetization in a magnetic field of
1-5 T and their temperature dependence up to 300 K; generation of
optical radiation during the spasmodic switching of conductivity at room
temperatures. These effects are explained to be the consequence of
carbon films granular structure, which can be considered as the
Josephson junction array (JJA). The results obtained provides a basis
for non-cryogenic electronics utilizing the Josephson’s effect such as
contact less field-effect switcher (FES), the detector of γ – radiation
for registration of neutrino and dark matter, the generators and
detectors of microwave radiation, the magnetic protection, the new type
of micro lasers based on the magnetic vortices movement, and the
low-dissipative coatings.
Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords:
thin films; superconductivity; Josephson devices.
Investigation
of Spectroscopical and Calorimetrical Properties of Poly(siloxane)/Liquid
Crystal Films
by R. Hadji, A. Negadi,
U. Maschke
Abstract -
Polymerization and crosslinking induced phase separation initiated by
ultraviolet radiation is used to elaborate Polymer Dispersed Liquid
Crystal films made of Polydimethylsiloxane and the liquid crystal
4-cyano-4’-n-pentyl-biphenyl (5CB). The polymerization induced phase
separation was monitored by Fourier Transform Infrared Spectroscopy (FTIR)
in terms of the radiation dose. The conversion of double bonds of the
dimethylsiloxanediacrylate shows a rapid increase at low dose values
followed by a plateau. Differential scanning calorimetry was employed to
obtain the nematic-isotropic transition temperature and the glass
transition temperature of the liquid crystal in the presence of the
monomer.
Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords:
Polysiloxane; liquid crystal; UV irradiation; infrared
spectroscopy, differential scanning calorimetry.
The
Vacancies Jump Rate, Diffusion Coefficient and Jump Length in Cu- Zn Ferrite
by H. M. Zaki
Abstract -
Samples with the chemical formula Cu1-x ZnxFe2 O4 (x=0.2, 0.4, 0.6, 0.8
& 1) were prepared by the standard ceramic method. The electric
conductivity and dielectric loss tangent were studied as a function of
vacancy jump rate. The results show that the dielectric constant and
dielectric loss tangent decrease with increasing vacancy jump rate. In
addition, the electron jump length in the octahedral sites was studied
as a function of zinc concentration. The increase of the jump length
with Zn concentration has been attributed to the substitution of Fe+3
for Zn2+ at the A-sites which increases the B-B interaction. The
increase of diffusion coefficient with increasing Zn concentration was
reinforced by the increase of jump rate.
Copyright © 2008 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords:
Ferrites, dielectric properties, jump rate, jump length, diffusion
coefficient.
| 
