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The present work reports the temperature and frequency dependence
of a.c. conductivity in glassy Se70Te30−xZnx (x = 0, 2, 4 and 6) alloys in the temperature range 300–500 K and frequency range 1 kHz.
An agreement between experimental and theoretical results suggests that the
a.c. conductivity behaviour of the present samples can be successfully
explained by correlated barrier hopping (CBH) model. The density of defect
states has been determined using this model for all the glassy alloys.
The results show that bipolaron hopping dominates over single-polaron
hopping in this glassy system. This is explained in terms of lower values of
the maximum barrier height for single-polaron hopping.
Organic photovoltaic cells based on the multilayers
structure, indium tin oxide
tris(8-hydroxyquinoline) (Alq3)/aluminium, have been studied. When an
ultra-thin metal layer is deposited onto the surface of the ITO anode the
power conversion efficiency of the cells is significantly improved. The
improvement depends on the ITO used. These differences have been attributed
to the difficulty to control the surface chemistry of ITO. The best result
has been obtained with a gold layer thick of about 0.5 nm. We propose that
the gold ultra-thin film, which is too thin to be continuous, allows to
improve the agreement between the work function of the anode and the highest
occupied molecular orbital (HOMO) of the organic donor CuPc and to passivate
the surface contamination of ITO.
Polymer sheets are currently used worldwide in a wide
range of applications. The manufacturing process of these sheets involves
extruding machines that stretch the material in both lateral and
longitudinal directions with respect to the machine direction, thus inducing
birefringence. In most cases, the film obtained is optically biaxial.
Polarimetric spectroscopy (Ellipsometry and Mueller Matrix) combined with
conoscopic observation are the methods of choice to study these properties.
In this work we report an analysis of commercially available polyethylene
terephtalate (PET) films used as substrate for food packaging as well as for
embedded electronic devices such as solar cells or flexible displays.
Initial observation of these films through polarizing microscope in
conoscopic mode reveals first the trace of optical axis plane with respect
to the film surface and second, whether the optical axis is acute or not.
This preliminary study allows optimal sample positioning for further
polarimetric studies. The measurements and modelling are done in both
reflection and transmission mode on several spectroscopic polarimetric
setups from UV to NIR. The models give as a main result, the dielectric
tensor of the film as well as its orientation with respect to the laboratory
Kinetic electron emission from MgO film under the impact of 50–300 eV
rare-gas ions has been investigated by Monte Carlo simulation. The program
includes excitation of the target electrons (by projectile ions, recoiling
target atoms and fast primary electrons), subsequent transport and escape of
these electrons from the target surface. Potential electron yields due to
Auger neutralization of various ions are obtained by comparing the
calculated kinetic electron yield with the experimental data. The program
generates partial yields of the secondary electrons excited by projectile
ions, recoiling target atoms and electron cascades. The partial yields of
the electrons excited by projectile ions and electron cascades fluctuate
with mass of the projectile ion like the electronic stopping. Moreover,
lateral and depth distribution of the electrons excited by three excitation
processes were quite different. For the range of investigated ion energies,
the average electron escape depth was independent of the mass of the
incident ion, which indicates that electron escape depth is a material
Well-aligned ZnO nanocones were self-assembled on amorphous carbon using
manganese oxide assisted thermal chemical vapor transport and condensation,
without any metal catalysts. Compared with the ZnO nanowires fabricated
without the manganese oxide assistance, the field emission performance of
the ZnO nanocones was greatly improved, lower turn-on electronic fields and
higher current densities were achieved with these emitters. Experimental
analyses showed that the ZnO nanocones grow vertically and epitaxially on
the  oriented ZnO intermediate layer between nanocones and substrate
The manganese oxide seems to play a crucial role in the formation of this
ZnO intermediate layer.
The fabrication of a hybrid micro/nano-fluidic device to
study electropreconcentration of biomolecules is presented. A nanoslit
surrounded by glass is formed between two access microchannels and an “H”
configuration bio-analysis system is developed. The optimized know-how for
this biochip fabrication is transferred and the key steps are discussed.
Fluorescence spatiotemporal profile in the preconcentration area is recorded
and quantitatively analyzed. The reliability of the applied technology for
studies of charged biomolecule transport phenomena across nanochannels is
proven giving two examples for different preconcentration geometries.
The intensity spectrum of modulated noisy light on optical microwave signal
processing and on conversion of FM noise to intensity noise in optical links
is investigated theoretically and experimentally with a good
agreement. We have applied a model that uses a 1550 nm distributed feedback
(DFB) laser and an unbalanced Mach-Zehnder interferometer (UMZI) considering
the external phase modulator. Numerical calculations show the influence of
the phase modulation index, modulation frequency, and interferometric delay
in the phase-to-intensity noise conversion by lowest-order group-velocity
dispersion in optical fiber. The results can be employed to estimate the
influence of the chromatic dispersion in phase-to-intensity noise
conversion, which use either self-delayed interferences or interferometers.
In image processing, the Wavelet Transform (WT) is
largely used. However, time requirements for large two-dimensional
image transforms are hard to meet with sequential implementations.
Parallel implementation decreases the processing time and allows
to reach a real-time operation in image coding. Unfortunately,
this parallel coding increases the hardware complexity.
We propose an optical implementation of the JPEG2000 compression
using a special implementation of the WT. Special attention is
paid to propose a simple all optical setup carrying out the
optical implementation of JPEG2000 compression for gray-level
images. Finally, an adaptation of our technique to colored images
The methods to control the pulse width of a laser-diode end-pumped doubly
Q-switched Nd:YVO4/YVO4 composite crystal laser with
acoustic-optic (AO) and GaAs saturable absorber has been theoretically and
experimentally studied. By varying the laser beam radius in the Q-switchers
and the pump beam radius in the gain medium, we provide efficient means to
control the pulse duration. The coupled rate equations are used to analyze
the process of the laser. The experimental results are consistent with the
Photoinduced changes in a Sudan I doped PMMA thin film
were investigated. The dependence of photoinduced birefringence of the thin
film on light intensity was studied, with a continuous wave (CW) 532 nm
laser as pump light and a CW 650 nm laser as probe light. For all the light
intensities (100–1000 mW/cm2), the thin film possessed large
photoinduced birefringence (Δn ~ 10−4). With a CW 532 nm
laser at relatively low light intensity, a reversible polarization hologram
has been recorded in the thin film. Moreover, Z-scan measurements showed
that the thin film possessed large nonlinear refractive index (−7.93 ×
10−5 cm 2/W) and nonlinear absorption coefficient (−5.50 W/cm)
under a CW 532 nm excitation.
Analysis of the optical generation of three bands of continuously tunable millimeter-wave signals using an optical phase modulator (OPM) and an optical notch filter is presented. Three bands of millimeter-wave signals are tuned by using an optical phase modulator and a polarization state rotation filter (PSRF) as optical notch filter. The effect of the chromatic dispersion on wide-band continuously tunable millimeter-wave signal which using an OPM and a PSRF is investigated. The spectrum of the generated millimeter-wave signal after transmission over a 25 km standard single-mode fiber (SSMF) is obtained.
A recent claim [Eur. Phys. J. Appl. Phys. 40, 293 (2007)] demonstrating a nuclear process triggered by electrolysis is
challenged. An analysis, based on relative diameters, is used to demonstrate
that predominant pits could not possibly be attributed to alpha particles,
or to less massive nuclear projectiles. This conclusion is supported not
only by positive results from a replication experiment, but also by results
from the experiment on which the original claim was based. While the
numerous SPAWAR-type pits seem to be highly reproducible, their
interpretation is not yet clear.
Earlier we reported, in this journal, that the pits generated in CR-39
detectors during Pd/D co-deposition experiments are consistent with those
observed for pits that are of a nuclear origin. Recently, that
interpretation has been challenged. In this communication, additional
experimental data and further analysis of our earlier results are provided
that support our original conclusions.
Physics of Energy Generation, Conversion and Storage
It is theoretically shown that an attractive effective potential is
generated via optical phonon exchange between two quasi-free, different
particles in deuterated Pd which, in turn, enhances the probability of
their nuclear fusion reaction. Mechanisms, that
may be responsible for extra heat production and nuclear isomer formation,
are also discussed. Creation of 4He pairs due
to the significantly increased probability of the p + 7Li
24He + 17.35 MeV and d + 6Li
24He + 22.37 MeV
nuclear reactions is predicted. Some of the basic questions of fusion reactions in
solids seem to be successfully explained.
In order to improve our knowledge of the emitted signal of forests at L-band
(1.4 GHz) we focused this study on permittivity measurements of heterogenic
natural media such as soil or litter consisting of plant debris and organic
matter. This study was done in the context of the upcoming SMOS (Soil
Moisture and Ocean Salinity) satellite mission that will attempt to map
surface soil moisture from L-band (1.4 GHz) passive microwave measurements.
In the field of passive microwaves, very little information exists about the
behaviour of the L-band signal of forests especially when litter is included
in the soil-vegetation system. To date very few analyses have investigated
the dielectric behaviour of the litter layer and its influence on the
microwave emission of forests is generally neglected.
This paper presents a dynamical non linear model of the
spatial time-dependant evolution of A3 point during a particular
sequence of resistance spot welding in steel material. The model is based on
a solution to the heat equation, expressed in cylindrical coordinates inside
the joint area, and when the source term is attributed to the electrical
power. By the mean of the steel binary Fe–C diagram and the deduced
t-dependant temperature rise profile, an estimation of the A3 point
spatial range date is given and compared to further results. The obtained
temperature profile is yielded, taking into account main parameters
variations, as a guide to non-destructive protocols and thermal