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.
Deepti Das, Krishna; Gopikrishna, M; Aanandan,C K; Mohanan, P; Vasudevan, K(Electronics Letters, August , 2008)
[+]
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Abstract:
An ultra-wideband (UWB) printed slot antenna, suitable for integration with the printed circuit board (PCB) of a wireless universal serial-bus (WUSB) dongle is presented. The design comprises a near-rectangular slot fed by a coplanar waveguide printed on a PCB of width 20 mm. The proposed design has a large bandwidth covering the 3.1-10.6 GHz UWB band, unaffected by the ground length, and omnidirectional radiation patterns. A linear phase response throughout the band further confirms its suitability for high-speed wireless connectivity.
Deepti Das, Krishna; Gopikrishna, M; Aanandan,C K; Mohanan, P; Vasudevan, K(Wiley InterScience, June , 2009)
[+]
[-]
Abstract:
A compact ultra-wideband (UWB) printed slot antenna is described, suitable for integration with the printed circuit board (PCB) of a wireless, universal, serial-bus dongle. The design comprises of a near-rectangular slot fed by a coplanar waveguide (CPW) printed on a PCB of size 20 × 30 mm2. It has a large bandwidth covering the 3.1–10.6 GHz UWB band, with omnidirectional radiation patterns. Further, a notched band centered at 5.45 GHz wireless local area network bands is obtained within the wide bandwidth by inserting a narrow slot inside the tuning stub. Details of the antenna design are described, and the experimental results of the constructed prototype are presented. The time domain studies on the antenna shows a linear phase response throughout the band except at the notched frequency. The transient analysis of the antenna indicates very little pulse distortion confirming its suitability for high speed wireless connectivity.
Hyunkieu,Yang; Sangseol,Lee(Microwave and Optical Technology Letters, December 5, 2001)
[+]
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Abstract:
The cutoff wavenumbers of higher order modes in circular
eccentric guides are computed with the variational analysis combined
with a conformal mapping. A conformal mapping is applied to the
variational formulation, and the variational equation is solved by the
finite-element method. Numerical results for TE and TM cutoff
wavenumbers are presented for different distances between the centers
and ratio of the radii. Comparisons with numerical results found in the
literature validate the presented method
Pedicle screw insertion technique has made revolution in the surgical treatment of spinal fractures and spinal disorders. Although X- ray fluoroscopy based navigation is popular, there is risk of prolonged exposure to X- ray radiation. Systems that have lower radiation risk are generally quite expensive. The position and orientation of the drill is clinically very important in pedicle screw fixation. In this paper, the position and orientation of the marker on the drill is determined using pattern recognition based methods, using geometric features, obtained from the input video sequence taken from CCD camera. A search is then performed on the video frames after preprocessing, to obtain the exact position and orientation of the drill. An animated graphics, showing the instantaneous position and orientation of the drill is then overlaid on the processed video for real time drill control and navigation
Lethakumary,B; Sreedevi, Menon K; Priya,Francis; Aanandan,C K; Mohanan, P(Microwave and Optical Technology Letters, January 20, 2005)
[+]
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Abstract:
In this paper, we introduce a novel feeding technique for
bandwidth enhancement of a rectangular microstrip antenna This antenna
offers an impedance bandwidth of 22% without degrading the effciencv.
The effect of the feed parameters upon patch characteristics
such as resonant frequency, impedance bandwidth, and radiation pattern are studied in detail. The experimental results are verified using the
FDTD results
Sreedevi, Menon K; Lethakumary,B; Mohanan, P; Bijumon, P V; Sebastian,M T(Microwave and Optical Technology Letters, August 20, 2004)
[+]
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Abstract:
A broadband cylindrical dielectric resonator antenna
(DRA) energized with an L-strip feed is presented The novel exciting
technique achieves a 2:1 VSWR bandwidth of 18%. The variation of
bandwidth for different feed parameters is also studied
The design and development of an L-band printed dipole antenna.
optimized for wide-band applications near first resonance, is reported.
This design has achieved more than 48% impedance bandwidth
(VSWR 2:1), without degrading its overall radiation efficiency
Sarin, V P; Nisha, Nassar; Deepu, V; Aanandan,C K; Mohanan, P; Vasudevan, K(Antennas and Wireless Propagation Letters, IEEE, 2009)
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Abstract:
A simple electromagnetically coupled wideband printed microstrip antenna having a 2:1 VSWR bandwidth of 38% covering the 5.2/5.8-GHz WLAN, HIPERLAN2, and HiSWANa communication bands is presented. The large bandwidth is obtained by adding a rectangular metal strip on a slotted square microstrip antenna. The antenna occupies an overall dimension of 42 times 55 times 3.2 mm3 when printed on a substrate of dielectric constant 4. It exhibits good radiation characteristics and moderate gain in the entire operating band. Details of the design along with experimental and simulation results are presented and discussed.