microwave dielectric properties of ceramics based on Ba(Mgv3Ta(2-2x)t3W,t3Tixt3)O3 is investigated as a function of x. The
15 densification as well as dielectric properties deteriorate with increase in the substitution levels of (Ti 1,3W113)333 + at (Ta213)3.33+ site
16 in Ba(Mg113Ta213)03. The rt is approaching zero between x = 0.1 and 0.15 in Ba(Mg it3Ta(2-2,,.)t3W,it3Ti,Tt3)O3 where quality factor is
17 reasonably good (Qu x f = 80,000-90,000 GHz). The Ba(Mg1,3Ta(2_,013W,13Ti,,13)03 with x = 1.0 has e, = 15.4, rf= -25.1 ppm/
18 "C, Q„ x f = 35,400 GHz
The BaO-2CeO2-nTiO2 ceramics with n = 3, 4 and 5 have been prepared with CeO2 as starting material . The ceramics have been
characterized using scanning electron microscopy , X-ray diffraction , Raman and X-ray photoelectron spectroscopy techniques. The
microwave dielectric properties have been measured using standard dielectric resonator techniques . BaO-2CeO2-3TiO2 (123),
BaO-2CeO2-4TiO2 ( 124) and BaO-2CeO2-5TiO2 ( 125) ceramics showed dielectric constants of 38, 27 and 32, respectively . All the
ceramics showed fairly good unloaded Q - factors . 124 and 125 compounds exhibited low tf values, while 123 showed a high rf value
Isuhak, Naseembeevi Jawahar; Narayana Iyer, Santha; Mailadil, Thomas Sebastian(Materials Reserach Society, December , 2002)
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Abstract:
Single-phase polycrystalline ceramics in the MO-La2O3-Ti02 (M = Ca, Sr, Ba)
system, such as cation-deficient hexagonal perovskites CaLa4Ti4O15, SrLa4Ti4O15,
BaLa4Ti4O15, and Ca2La4Ti5O18 and the orthorhombic phases CaLa4Ti5O17 and
CaLa8Ti9O31, were prepared through the solid-state ceramic route. The phases
and structure of the ceramics were analyzed through x-ray diffraction and scanning
electron microscopy. The microwave dielectric properties of the ceramics were studied
using a network analyzer. The investigated ceramics show high Er in the range 42 to
54, high quality factors with Q x f in the range 16,222 to 50,215 GHz, and low Tf in
the range -25 to +6 ppm3/°C. These high dielectric constant materials with high Q x f
up to 50,215 GHz are suitable for applications where narrow bandwidth and extremely
low insertion loss is necessary, especially at frequencies around 1.9 GHz
Microwave dielectric ceramics based on RETiTaO6 (RE = La, Cc, Pr, Nd, Sm, Eu,
Gd, Tb, Dy, Ho, Y, Er, Yb, Al, and In) were prepared using a conventional solid-state
ceramic route. The structure and microstructure of the samples were analyzed using
x-ray diffraction and scanning electron microscopy techniques. The sintered samples
were characterized in the microwave frequency region. The ceramics based on Ce, Pr,
Nd, Sm, Eu, Gd, Tb, and Dy, which crystallize in orthorhombic aeschynite structure,
had a relatively high dielectric constant and positive T f while those based on Ho, Er,
and Yb, with orthorhombic euxenite structure, had a low dielectric constant and
negative Tf. The RETiTaO6 ceramics had a high-quality factor. The dielectric constant
and unit cell volume of the ceramics increased with an increase in ionic radius of the
rare-earth ions, but density decreased with it. The value of Tf increased with an
increase in RE ionic radii, and a change in the sign of Tf occurred when the ionic
radius was between 0.90 and 0.92 A. The results indicated that the boundary of the
aeschynite to euxenite morphotropic phase change lay between DyTiTaO6 and
HoTiTaO6. Low-loss ceramics like ErTiTaO6 (Er = 20.6, Qxf = 85,500), EuTiTaO6
(Er = 41.3, Qxf = 59,500), and YTiTaO6 (Er = 22.1, Q„xf = 51,400) are potential
candidates for dielectric resonator applications
Dielectric resonator ceramics with composition formula Ba[(D3+0.3 Bi0.2)Nb0.5]O3,where D3+=Y,Pr,Sm,Gd,Dy and Er,were prepared by the conventional ceramic preparation route
Bindu, G; Vinu, Thomas; Anil, Lonappan; Aanandan,C K; Mathew, K T(John Wiley & Sons, January , 2006)
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Abstract:
A phantom that exhibits complex dielectric properties similar to low-water-content biological tissues over the electromagnetic spectrum of 2000–3000 MHz has been synthesized from carbon black, graphite powder, and poly vinyl acetate (PVA)-based adhesive. The material overcomes various problems that are inherent in conventional phantoms such as decomposition and deterioration due to the invasion of bacteria or mold. The absorption coefficients of the material for various concentrations of carbon and graphite are studied. A combination of 50% poly-vinyl-acetate-based adhesive, 20% carbon, and 30% graphite exhibits a high absorption coefficient, which suggests another application of the material as a good microwave absorber for the interior lining of tomographic chamber in microwave imaging. The cavity-perturbation technique is adopted to study the dielectric properties of the material.
Dey,S; Aanandan,C K; Mohanan, P; K G Nair(Department of Electronics, June , 1993)
[+]
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Abstract:
A circular miqrostrip antenna with a modified structure is
presented. By adjusting the feed location along the circumference
of the patch it is possible to match the antenna with a C
microstrip line of any impedance. The impedance bandwidth
and radiation characteristics are unaffected by this structural
V modification.
Fingerprint based authentication systems are one of the cost-effective biometric authentication techniques employed for personal identification. As the data base population increases, fast identification/recognition algorithms are required with high accuracy. Accuracy can be increased using multimodal evidences collected by multiple biometric traits. In this work, consecutive fingerprint images are taken, global singularities are located using directional field strength and their local orientation vector is formulated with respect to the base line of the finger. Feature level fusion is carried out and a 32 element feature template is obtained. A matching score is formulated for the identification and 100% accuracy was obtained for a database of 300 persons. The polygonal feature vector helps to reduce the size of the feature database from the present 70-100 minutiae features to just 32 features and also a lower matching threshold can be fixed compared to single finger based identification
Description:
(IJACSA) International Journal of Advanced Computer Science and Applications,
Vol. 3, No. 11, 2012
Jose, Rodriguez Victor; Jose, Molina Garcia Maria; Leandra, Juan Liacer(Microwave and Optical Technology Letters, February 20, 2004)
[+]
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Abstract:
This work presents an explicit formulation for multiple-
edge diffraction for mobile radiowave propagation in terms of
uniform theory of diffraction (UTD) coefficients when a spherical
incident wave is considered. This solution can be used in an UTD
context and sharply reduces the computing time over existing formulation.
Results can be applied in the planning of microcellular systems
Zheng,Qinhong; Xie,Fuyao; Liang,Li; Wang,Ruili; Ou,Jiaming(Microwave and Optical Technology Letters, June 20, 2000)
[+]
[-]
Abstract:
A new approach, the multipole theory (MT) method, is
presented for the computation of cutoff wavenumbers of waveguides
partially filled with dielectric. The MT formulation of the eigenvalue
problem of an inhomogeneous waveguide is derived. Representative
computational examples, including dielectric-rod-loaded rectangular and
double-ridged waveguides, are given to validate the theory, and to
demonstrate the degree of its efficiency
Aanandan,C K; Mohanan, P; Supriyo,Dey; K G Nair(Department of Electronics, 1994)
[+]
[-]
Abstract:
A simple technique to improve the impedance bandwidth of a circular
microstrip patch antenna using two sectorial slots is proposed. Using this
design more than 5% impedance bandwidth is obtained. The added
advantage of this new antenna is that it can be fed by a 50 microstrip
line.
Supriyo,Dey; Aanandan,C K; Mohanan, P; K G Nair(Microwave and Optical Technology Letters, September , 1994)
[+]
[-]
Abstract:
A simple technique to improve the impedance bandwidth of a circular
microstrip patch antenna using two sectorial slots is proposed. Using this
design more than 5% impedance bandwidth is obtained. The added
advantage of this new antenna is that it can be fed by a 50- microstrip line
Manju,Paulson; Sona,Kundukulam O; Aanandan,C K; Mohanan, P(Microwave and Optical Technology Letters, June 5, 2001)
[+]
[-]
Abstract:
A new compact dual-band, dual-polarized microstrip antenna
is presented. 7'iris antenna resonates at two frequencies with
different polarizations: a linearly polarized one for terrestrial
communication, and a circularly polarized one for satellite mobile
communication. This antenna also provides an area reduction of 70%
compared to a standard rectangular patch antenna
George,J; Deepukumar,M; Aanandan,C K; Mohanan, P; K G Nair(Department of Electronics, March , 1996)
[+]
[-]
Abstract:
A new microstrip antenna geometry with considerable reduction
in size, with similar radiation characteristics to those of an
equivalent rectangular patch antenna is proposed. A relationship
has been suggested for fmding out the resonant frequency of the
new geometry, and its validity has been established by the
experimental results. Without increasing the aperture area, this
geometry also offers a facility for considerably reducing the
resonant frequency compared to conventional patches.
Sebastian, Mathew; Joe, Jacob; Joseph, V P; Bijukumar, S; Raveendranath, U; Mathew, K T(John Wiley & Sons, March 5, 1999)
[+]
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Abstract:
This paper presents the design of a new type of corner reflector (CR) antenna and the experimental investigation of its radiation characteristics. The design involves the addition of planar parallel periodic strips to the two sides of a CR antenna. The position, angular orientation, and number of strips have a notable effect on the H-plane radiation characteristics of the antenna. Certain configurations of the new antenna are capable of producing very sharp axial beams with gain on the order of 5 dB over the square corner reflector antenna. A configuration that can provide symmetric twin beams with enhanced gain and reduced half-power beam width (HPBW) is also presented.
Tessamma, Thomas; Deepa, Sankar(Society for Imaging Informatics in Medicine, October , 2010)
[+]
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Abstract:
In this paper, a novel fast method for modeling mammograms
by deterministic fractal coding approach to detect
the presence of microcalcifications, which are early
signs of breast cancer, is presented. The modeled
mammogram obtained using fractal encoding method is
visually similar to the original image containing microcalcifications,
and therefore, when it is taken out from
the original mammogram, the presence of microcalcifications
can be enhanced. The limitation of fractal image
modeling is the tremendous time required for encoding.
In the present work, instead of searching for a matching
domain in the entire domain pool of the image, three
methods based on mean and variance, dynamic range of
the image blocks, and mass center features are used.
This reduced the encoding time by a factor of 3, 89, and
13, respectively, in the three methods with respect to
the conventional fractal image coding method with quad
tree partitioning. The mammograms obtained from The
Mammographic Image Analysis Society database
(ground truth available) gave a total detection score of
87.6%, 87.6%, 90.5%, and 87.6%, for the conventional
and the proposed three methods, respectively.
Description:
Journal of Digital Imaging, Vol 23, No 5 (October), 2010: pp 538-546
Tessamma, Thomas; Deepa, J(The International Institute for Science, Technology and Education (IISTE), 2013)
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Abstract:
As the technologies for the fabrication of high quality microarray advances rapidly, quantification of
microarray data becomes a major task. Gridding is the first step in the analysis of microarray images for
locating the subarrays and individual spots within each subarray. For accurate gridding of high-density
microarray images, in the presence of contamination and background noise, precise calculation of
parameters is essential. This paper presents an accurate fully automatic gridding method for locating
suarrays and individual spots using the intensity projection profile of the most suitable subimage. The
method is capable of processing the image without any user intervention and does not demand any input
parameters as many other commercial and academic packages. According to results obtained, the accuracy
of our algorithm is between 95-100% for microarray images with coefficient of variation less than two.
Experimental results show that the method is capable of gridding microarray images with irregular spots,
varying surface intensity distribution and with more than 50% contamination
Description:
Computer Engineering and Intelligent Systems,Vol.4, No.1, 2013
New dielectric ceramics with formula BaTi3Nb4, O„ and Ba6Til4Nbz039 have been prepared and characterized. BaTi3Nba017 was densified to 92% of TD after firing at 1310 oC for 4 h. However, Ba6Ti 1 4Nb2O39 fired under optimized conditions (1260 ` C for 4 h) showed only 85% TD together with secondary phase. The crystal system of both of the compositions is orthorhombic