Abstract: Starch/chitosan blend have been prepared via the
solution casting technique. Ionic conductivity for the system was
conducted over a wide range of frequency between 50 Hz-1 MHz and
at temperatures between 303 K and 373 K. Sample with 35 wt% of
NH4NO3 shows the highest conductivity of 3.89 ± 0.79 x 10-5 Scm-1
at room temperature. Conductivity-temperature relationship suggests
that samples are Arrhenian. Power law exponent was obtained
through dielectric loss variation and the trend suggests that the
conduction mechanism of the ions can be represented by the
correlated barrier hopping (CBH) model.
Abstract: In this paper, the design of a multiple U-slotted microstrip patch antenna with frequency selective surface (FSS) as a superstrate for WLAN and WiMAX applications is presented. The proposed antenna is designed by using substrate FR4 having permittivity of 4.4 and air substrate. The characteristics of the antenna are designed and evaluated the performance of modelled antenna using CST Microwave studio. The proposed antenna dual resonant frequency has been achieved in the band of 2.37-2.55 GHz and 3.4-3.6 GHz. Because of the impact of FSS superstrate, it is found that the bandwidths have been improved from 6.12% to 7.35 % and 3.7% to 5.7% at resonant frequencies 2.45 GHz and 3.5 GHz, respectively. The maximum gain at the resonant frequency of 2.45 and 3.5 GHz are 9.3 and 11.33 dBi, respectively.
Abstract: There are a many of needs for the development of
SiC-based hydrogen sensor for harsh environment applications. We
fabricated and investigated Pd/Ta2O5/SiC-based hydrogen sensors
with MOS capacitor structure for high temperature process monitoring
and leak detection applications in such automotive, chemical and
petroleum industries as well as direct monitoring of combustion
processes. In this work, we used silicon carbide (SiC) as a substrate to
replace silicon which operating temperatures are limited to below
200°C. Tantalum oxide was investigated as dielectric layer which has
high permeability for hydrogen gas and high dielectric permittivity,
compared with silicon dioxide or silicon nitride. Then, electrical
response properties, such as I-V curve and dependence of capacitance
on hydrogen concentrations were analyzed in the temperature ranges
of room temperature to 500°C for performance evaluation of the
sensor.
Abstract: The effect of porous medium on the capillary instability of a cylindrical interface in the presence of axial electric field has been investigated using viscous potential flow theory. In viscous potential flow, the viscous term in Navier-Stokes equation vanishes as
vorticity is zero but viscosity is not zero. Viscosity enters through normal stress balance in the viscous potential flow theory and tangential stresses are not considered. A dispersion relation that accounts for the growth of axisymmetric waves is derived and stability is discussed theoretically as well as numerically. Stability criterion is given by critical value of applied electric field as well as critical wave number. Various graphs have been drawn to show the effect of various physical parameters such as electric field, viscosity ratio, permittivity ratio on the stability of the system. It has been observed that the axial electric field and porous medium both have stabilizing effect on the stability of the system.
Abstract: Dielectric sheet perturbation to the dominant TE111
mode resonant frequency of a circular cavity is studied and presented
in this paper. The dielectric sheet, placed at the middle of the airfilled
cavity, introduces discontinuities and disturbs the configuration
of electromagnetic fields in the cavity. For fixed dimensions of cavity
and fixed thickness of the loading dielectric, the dominant resonant
frequency varies quite linearly with the permittivity of the dielectric.
This quasi-linear relationship is plotted using Maple software and
verified using 3D electromagnetic simulations. Two probes are used
in the simulation for wave excitation into and from the cavity. The
best length of probe is found to be 3 mm, giving the closest resonant
frequency to the one calculated using Maple. A total of fourteen
different dielectrics of permittivity ranging from 1 to 12.9 are tested
one by one in the simulation. The works show very close agreement
between the results from Maple and the simulation. A constant
difference of 0.04 GHz is found between the resonant frequencies
collected during simulation and the ones from Maple. The success of
this project may lead to the possibility of using the middle loaded
cavity at TE111 mode as a microwave non-destructive testing of solid
materials.
Abstract: In this paper, a novel wave equation for electromagnetic
waves in a medium having anisotropic permittivity has been derived
with the help of Maxwell-s curl equations. The x and y components
of the Maxwell-s equations are written with the permittivity () being
a 3 × 3 symmetric matrix. These equations are solved for Ex , Ey,
Hx, Hy in terms of Ez, Hz, and the partial derivatives. The Z
components of the Maxwell-s curl are then used to arrive to the
generalized Helmholtz equations for Ez and Hz.
Abstract: The electromagnetic imaging of inhomogeneous
dielectric cylinders buried in a slab medium by transverse electric
(TE) wave illumination is investigated. Dielectric cylinders of
unknown permittivities are buried in second space and scattered a
group of unrelated waves incident from first space where the scattered
field is recorded. By proper arrangement of the various unrelated
incident fields, the difficulties of ill-posedness and nonlinearity are
circumvented, and the permittivity distribution can be reconstructed
through simple matrix operations. The algorithm is based on the
moment method and the unrelated illumination method. Numerical
results are given to demonstrate the capability of the inverse
algorithm. Good reconstruction is obtained even in the presence of
additive Gaussian random noise in measured data. In addition, the
effect of noise on the reconstruction result is also investigated.
Abstract: A time-domain numerical model within the
framework of transmission line modeling (TLM) is developed to
simulate electromagnetic pulse propagation inside multiple
microcavities forming photonic crystal (PhC) structures. The model
developed is quite general and is capable of simulating complex
electromagnetic problems accurately. The field quantities can be
mapped onto a passive electrical circuit equivalent what ensures that
TLM is provably stable and conservative at a local level.
Furthermore, the circuit representation allows a high level of
hybridization of TLM with other techniques and lumped circuit
models of components and devices. A photonic crystal structure
formed by rods (or blocks) of high-permittivity dieletric material
embedded in a low-dielectric background medium is simulated as an
example. The model developed gives vital spatio-temporal
information about the signal, and also gives spectral information over
a wide frequency range in a single run. The model has wide
applications in microwave communication systems, optical
waveguides and electromagnetic materials simulations.