Jianlang,Li; Liren,Liu; Yingchun,Guo; Huaisheng,Wang; Changhe,Zhou(Microwave and Optical Technology Letters, December 20, 1999)
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Abstract:
The transient interaction between a refraction index grating
and light beams during simultaneous writing and thermal fixing of
a photorefractive hologram is investigated. With a diffusion- and
photovoltaic-dominated carrier transport mechanism and carrier thermal
activation (temperature dependent) considered in Fe:LiNbO3 crystal, from
the standpoint of field-material coupling, the theoretical thermal fixing
time and the space-charge field buildup, spatial distribution, and temperature
dependence are given numerically by combining the band transport
model with mobile ions with the coupled-wave equation
Design and development of a new feed -horn antenna
with low sidelobe levels is reported . The E-walls of this
antenna are fabricated with low -loss dielectric substrate ,
periodicallyloaded with thin conducting strips . The antenna
is found to be simulating the radiation characteristics of metallic
Corrugated horns . This can be an ideal substitute for metallic
Corrugated horns with added advantages like light -weight and low
production cost
K G Nair; Mohanan, P; Stephen, Rodrigues(Department of Electronics, 1991)
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Abstract:
Design and development of a new feed -horn antenna
with low sidelobe levels is reported . The E-walls of this
antenna are fabricated with low -loss dielectric substrate , periodically
loaded with thin conducting strips . The antenna is found
to be simulating the radiation characteristics of metallic corrugated
horns . This can be an ideal substitute for metallic corrugated
horns with added advantages like light -weight and low
production cost.
Mohanan, P; K G Nair; Stephen, Rodrigues(Department of Electronics, November , 1991)
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Abstract:
Design and development of a new feed -horn antenna
with low sidelobe levels is reported . The E-walls of this
antenna are fabricated with low -loss dielectric substrate , periodically
loaded with thin conducting strips . The antenna is found
to be simulating the radiation characteristics of metallic corrugated
horns . This can be an ideal substitute for metallic corrugated
horns with added advantages like light -weight and low
production cost.
Joseph, V P; Biju Kumar, S; Mathew, K T(John Wiley & Sons, April 5, 2001)
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Abstract:
The radiation characteristics of a new type of hollow dielectric H-plane sectoral horn antenna are presented. Metallic strips of optimum length are loaded on the H-walls of the sectoral horns. The effects of strip loading for producing square patterns in the H plane are discussed.
The (Ba1-x Srx) (Nd1/2, Nb1/2) O3 ceramics have been prepared by the conventional
ceramic route for different values of x. Addition of a small amount of
CeO2(1 wt%) as a sintering aid increased the density of the samples. The structure
and microstructure of the sintered samples are studied by X-ray diffraction
and SEM methods. The dielectric properties of the samples are measured in the
microwave frequency region as a function of composition. The dielectric constant
decreases as x increases. The coefficient of thermal variation of resonant
frequency decreases as the Sr content increases and goes to the negative side.
The dielectric properties of (Ba1-x Srx) (Nd1/2, Nb1/2) O3 are in the range suitable
for application as dielectric resonators in microwave circuits
Pazhoor Bijumon, Varghese; Mohanan, P; Mailadil, Thomas Sebastian(The Japan Society of Applied Physics, 2002)
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Abstract:
Microwave ceramic dielectric materials Ca5Nb2TiO12 and Ca5Ta2TiO12 have been prepared by a conventional solid-state
ceramic process. The structure was studied by X-ray diffraction and the dielectric properties were characterized at microwave
frequencies. The ceramics posses a relatively high dielectric constant, very low dielectric loss (Q5 x f > 30000GHz) and
small temperature variation of resonant frequency. These materials are potential candidates for dielectric resonator
applications in microwave integrated circuits. [DOI: 10. 1 143/JJAP.41.3834]
Dielectric ceramics based on solid solution phases of [RE1_x= REr]TiNb06, where REI_s = Nd, Pr, Sm and RE' = Dy, Gd and Y, were prepared by the conventional solid-state ceramic route for values of x. The ceramic samples are characterized by X-ray diffraction and microwave methods. Ceramics based on RE (Pr, Nd and Sm) belonging to aeschynite group shows positive value of Tf and those based on RE (Gd, Dy and Y) belonging to euxenite group show negative value of r f. The solid solution phases between the aeschynite and the euxenite group shows intermediate dielectric constant and r f values. The results indicate the possibility of tailoring the dielectric properties by varying the composition of the solid solution phases. The range of solid solubility of euxenite in aeschenite and aeschenite
in euxenite are different for different rare earth ions
Ceramic dielectric resonators in the BaO-RE2O3-TiO2 (RE = rare earth) system have been
prepared by the conventional solid state ceramic route. The dielectric properties have been
tailored by substitution of different rare earth oxides and by bismuth oxide addition. The
dielectric constants increased with Bi addition whereas the 0 decreased. The temperature
coefficient of the resonant frequency improved with bismuth addition
Ceramic dielectric resonators in the BaO-RE2O3-TiO2 (RE=rare earth) system have been
prepared by the conventional solid state ceramic route. The dielectric properties have been
tailored by substitution of different rare earth oxides and by bismuth oxide addition. The
dielectric constants increased with Bi addition whereas the Q decreased. The temperature
coeffecient of the resonant frequency improved with bismuth addition.
Microwave dielectric ceramics based on GdTiNb,-,.Ta,O6 and Sml _.,Y,TiTa06 have been prepared by conventional solid state
method . The GdTiTaO6 and SmTiTaO6 have aeschenite structure with positive rr and GdTiNbO6 and YTiTaO6 have euxenite
structure with negative rr. The rr of the ceramics has been tuned by preparing solid solution phases between the aeschynites and
euxenites for a possible zero rr material . It is observed that GdTiNbt_YTa.,O6 undergoes a phase transition from aeschynite to
euxenite when x=0.75 and in Sml-,YxTiTa06 for x= 0.73. The microwave dielectric properties change abruptly near the transition
region . The rr value approaches zero near the phase transition region while the samples have poor sinterability and poor quality
factor . The unloaded quality factor, dielectric constant and the sign of rr of the solid solution phases are found to depend on the
average ionic radius of the rare earth ion in RE ,-5RE',TiTaO6. The boundary of the euxenite-aeschynite phase transition occurs at
an average ( RE) ionic radius of 0.915 A in Sm,_, Y,.TiTaO6 solid solution phases
The microwave dielectric properties of ZnAl2O4 spinels were investigated and their properties
were tailored by adding different mole fractions of Ti02. The samples were synthesized using the mixed
oxide rout.e. The phase purity and crystal structure were identified using X-ray diffraction technique.
The sintered specimens were characterized in the microwave frequency range (3-13 GHz). The ZnA12O4
ceramics exhibited interesting dielectric properties (dielectric constant (e,.) = 8.5, unloaded quality factor
(Q.) = 4590 at 12.27 GHz and temperature coefficient of resonant frequency (Tf) = -79 ppm/°C).
Addition of Ti02 into the spinel improved its properties and the Tf approached zero for 0.83ZnAl2O4-
0.17TiO2• This temperature compensated composition has excellent microwave dielectric properties (Cr _
12.67, Q, = 9950 at 10.075 GHz) which can be exploited for microwave substrate applications
Tessamma, Thomas; Ananda Resmi, S(ACEEE, November , 2010)
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Abstract:
Low grade and High grade Gliomas are tumors
that originate in the glial cells. The main challenge in brain
tumor diagnosis is whether a tumor is benign or malignant,
primary or metastatic and low or high grade. Based on the
patient's MRI, a radiologist could not differentiate whether it
is a low grade Glioma or a high grade Glioma. Because both
of these are almost visually similar, autopsy confirms the
diagnosis of low grade with high-grade and infiltrative
features. In this paper, textural description of Grade I and
grade III Glioma are extracted using First order statistics and
Gray Level Co-occurance Matrix Method (GLCM). Textural
features are extracted from 16X16 sub image of the
segmented Region of Interest(ROI) .In the proposed method,
first order statistical features such as contrast, Intensity ,
Entropy, Kurtosis and spectral energy and GLCM features
extracted were showed promising results. The ranges of these
first order statistics and GLCM based features extracted are
highly discriminant between grade I and Grade III. In this
study which gives statistical textural information of grade I
and grade III Glioma which is very useful for further
classification and analysis and thus assisting Radiologist in
greater extent.
Description:
Int. J. of Recent Trends in Engineering and Technology, Vol. 4, No. 3, Nov 2010
Qinghe, Mao; John, Lit W Y(Microwave and Optical Technology Letters, November 20, 2002)
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Abstract:
The transient characteristics of an erbium-doped fiber
(F.DF) laser, which can switch between wavelengths. are investigated.
77te laser has a set of coupled linear cavities. The slow gain dynamics
of EDFs and the cross-gain saturation in the coupled cavities give rise
to delayed switching responses and relocation oscillations, which are
respertively measured to be l ins and 3.5 ms for the worst rase, and
which mar be decreased by increasing the pump power. Thus, the
switching speed of the laser may be higher than 100 Hz
Bijumon, P V; Sreedevi, Menon K; Suma,M N(Microwave and Optical Technology Letters, November 5, 2005)
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Abstract:
rectangular low-density, high-permittivity dielectric
resona or antenna (DRA) excited by T-shaped microstrip feed offering a
2:1 VSWR bandwidth of -22% at 2.975 GHz is reported. The design
methoaology and experimental results of the antenna are discussed. The
excellent gain and radiation performance of the proposed antenna
project: it as a potential candidate for telecommunication applications
Shyam S,Pattnaik; Dhruba C,Panda; Devi,S(Microwave and Optical Technology Letters, September 20, 2002)
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Abstract:
The mathematical formulation of empirically developed formulas Jirr the calculation of the resonant frequency of a thick-substrate
(h s 0.08151 A,,) microstrip antenna has been analyzed. With the
use qt' tunnel-based artificial neural networks (ANNs), the resonant frequency
of antennas with h satisfying the thick-substrate condition are
calculated and compared with the existing experimental results and also
with the simulation results obtained with the use of an IE3D software
package. The artificial neural network results are in very good agreement
with the experimental results
Bindu, G; Santhosh John, Abraham; Anil, Lonappan; Vinu, Thomas; Aanandan,C K; Mathew, K T(International Journal of Cancer Research, 2006)
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Abstract:
Despite its recognized value in detecting and characterizing breast disease, X-ray
mammography has important limitations that motivate the quest for alternatives to augment
the diagnostic tools that are currently available to the radiologist. The rationale for pursuing
electromagnetic methods are based on the significant dielectric contrast between normal
and cancerous breast tissues, when exposed to microwaves. The present study analyzes
two-dimensional microwave tomographic imaging on normal and malignant breast tissue
samples extracted by mastectomy, to assess the suitability of the technique for early
detection ofbreast cancer. The tissue samples are immersed in matching coupling medium
and are illuminated by 3 GHz signal. 2-D tomographic images ofthe breast tissue samples
are reconstructed from the collected scattered data using distorted Born iterative method.
Variations of dielectric permittivity in breast samples are distinguishable from the obtained
permittivity profiles, which is a clear indication of the presence of malignancy. Hence
microwave tomographic imaging is proposed as an alternate imaging modality for early
detection ofbreast cancer.