Lovely, M R; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(Indian Journal of Pure and Applied Physics, January , 1996)
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Abstract:
The design and development of an evanescent wave sensor to determine the etching rate of the core of an optical fibre is discussed in this paper. The working of the device is based on the principle of propagation and loss of the evanescent wave in the cladding region of the fibre. The fraction of light intensity creeping out of the core of an uncladded fibre is a function of the core radius. As this radius decreases, the evanescent wave coupling to the medium surrounding the core enhances. This results in a decrease of the transmitted light intensity through the fibre. This technique is useful to design and fabricate optical fibres with different core geometries.
Anantaraman, M R; Swapna S, Nair; Mercy, Mathews; Anantharaman, M R(Elsevier, May , 2005)
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Abstract:
Superparamagnetic nanocomposites based on Y-Fe2O3 and sulphonated polystyrene were synthesised by ion-exchange process
and the structural characterisation has been carried out using X-ray diffraction technique. Doping of cobalt in to the Y-Fe2O3 lattice
was effected in situ and the doping was varied in the atomic percentage range 1–10. The optical absorption studies show a band gap
of 2.84 eV, which is blue shifted by 0.64 eV when compared to the reported values for the bulk samples (2.2 eV). This is explained on
the basis of weak quantum confinement. Further size reduction can result in a strong confinement, which can yield transparent magnetic
nanocomposites because of further blue shifting. The band gap gets red shifted further with the addition of cobalt in the lattice
and this red shift increases with the increase in doping. The observed red shift can be attributed to the strain in the lattice caused by
the anisotropy induced by the addition of cobalt. Thus, tuning of bandgap and blue shifting is aided by weak exciton confinement
and further red shifting of the bandgap is assisted by cobalt doping.
Harikrishnan, K P; Nandakumaran, V M(Elsevier, November 21, 1988)
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We analyse numerically the bifurcation structure of a two-dimensional noninvertible map and show that different periodic cycles are arranged in it exactly in the same order as in the case of the logistic map. We also show that this map satisfies the general criteria for the existence of Sarkovskii ordering, which supports our numerical result. Incidently, this is the first report of the existence of Sarkovskii ordering in a two-dimensional map.
Ambili, V; Narayana, A C(Cochin University of Science and Technology, October , 2010)
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Abstract:
Drainage basins are durable geomorphic features that provide insights into the long term evolution of the landscape. River basin geometry develop response to the nature and distribution of uplift and subsidence, the spatial arrangement of lineaments (faults and joints), the relative resistance of different rock types and to climatically influenced hydrological parameters . For developing a drainage basin evolution history, it is necessary to understand physiography, drainage patterns, geomorphic features and its structural control and erosion status. The present study records evidences for active tectonic activities which were found to be responsible for the present day geomorphic set up of the study area since the Western Ghat evolution. A model was developed to explain the evolution of Chaliar River drainage basin based on detailed interpretation of morphometry and genesis of landforms with special emphasis on tectonic geomorphic indices and markers.
Description:
Department of Marine Geology and Geophysics, Cochin University of Science and Technology
Lalitha, P R; Rao, V R; V P N Nampoori(Current Science, 1980)
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Abstract:
Excitation and emission spectra of SrS : Mn : Ce phosphors have been studied in detail
at various Mn and Ce concentrations. In order to study the effect of external pressure on phosphors,
the samples were pretreated under various pressures. Four bands around 470 nm, 530 nm,
310 nm and 620 nm were observed, when the samples were excited with 265 nm radiation. The
effect of pressure is to reduce the fluorescence ability of the phosphors, and the luminescence
vanishes above O· 1 ton m-2 pressure. The fluorescence ability, however, can be regained on retiring
the sample. The emission mechanism has been attributed to two luminescentcenters in the forbidden
gap. An appreciable amount of photocurrent has also been observed for the sample.
Lo, H Y; Leung, K W(Microwave and Optical Technology Letters, June 5, 2001)
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Abstract:
A new configuration that employs a conducting conformal
strip to excite the low-profile equilaterial-triangular dielectric resonator
antenna (DRA) of very high permittivity is proposed. As compared with
the previous aperture-coupling configuration, the new configuration has
a wider impedance bandwidth (- 5.5%) and a higher front-to-back
radiation ratio. The return loss, radiation patterns, and antenna gain are
measured and discussed
Kailasnath, M; Nishant, Kumar; Nampoori, V P N; Vallabhan, C P G; Radhakrishnan, P(Elsevier, 2008)
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Abstract:
Dependence of energy transfer parameters on excitation wavelength has been investigated in poly (methyl methacrylate) (PMMA) optical fibre preforms doped with C 540:Rh B dye mixture by studying the fluorescence intensity and the lifetime variations. A fluorescence spectrophotometer was used to record the excitation spectra of the samples for the emission wavelengths 495 and 580 nm. The fluorescence emission from the polymer rods was studied at four specific excitation wavelengths viz; 445, 465, 488 and 532 nm. The fluorescence lifetime of the donor molecule was experimentally measured in polymer matrix by time correlated single photon counting technique. The energy transfer rate constants and transfer efficiencies were calculated and their dependence on the acceptor concentration was analysed for three excitation wavelengths. It was found that any change in the excitation wavelength leads to significant variations in the quenching characteristics, which in turn affect the calculated energy transfer parameters.
Radhakrishnan, P; V P N Nampoori; Litty, Irimpan; Bindu, Krishnan; Deepthy, A(Journal of Physics D : Applied Physics, August 30, 2007)
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In this paper, the fluorescence behaviour of nano colloids of ZnO has been
studied as a function of the excitation wavelength. We have found that
excitation at the tail of the absorption band gives rise to an emission that
shifts with the change of the excitation wavelength. The excitation
wavelength dependent shift of the fluorescence maximum is measured to be
between 60 and 100 nm. This kind of excitation wavelength dependent
fluorescence behaviour, which may appear to be in violation of Kasha’s rule
of excitation wavelength independence of the emission spectrum, has been
observed for nano ZnO colloids prepared by two different chemical routes
and different capping agents. It is shown that the existence of a distribution
of energetically different molecules in the ground state coupled with a low
rate of the excited state relaxation processes, namely, solvation and energy
transfer, are responsible for the excitation wavelength dependent
fluorescence behaviour of the systems.
V P N Nampoori; Radhakrishnan, P; Litty, Irimpan; Bindu, Krishnan; Deepthy, A(Journal of Physics D : Applied Physics, August 30, 2007)
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Abstract:
In this paper, the fluorescence behaviour of nano colloids of ZnO has been
studied as a function of the excitation wavelength. We have found that
excitation at the tail of the absorption band gives rise to an emission that
shifts with the change of the excitation wavelength. The excitation
wavelength dependent shift of the fluorescence maximum is measured to be
between 60 and 100 nm. This kind of excitation wavelength dependent
fluorescence behaviour, which may appear to be in violation of Kasha’s rule
of excitation wavelength independence of the emission spectrum, has been
observed for nano ZnO colloids prepared by two different chemical routes
and different capping agents. It is shown that the existence of a distribution
of energetically different molecules in the ground state coupled with a low
rate of the excited state relaxation processes, namely, solvation and energy
transfer, are responsible for the excitation wavelength dependent
fluorescence behaviour of the systems.
Krishnan Nair, P R; Nandakumaran, V M(Springer, October , 1998)
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Abstract:
We present the analytical investigations on a logistic map with a discontinuity at the
centre. An explanation for the bifurcation phenomenon in discontinuous systems is presented. We
establish that whenever the elements of an n-cycle (n > 1) approach the discontinuities of the nth
iterate of the map, a bifurcation other than the usual period-doubling one takes place. The periods of
the cycles decrease in an arithmetic progression, as the control parameter is varied. The system also
shows the presence of multiple attractors. Our results are verified by numerical experiments as well.
Bindhu, C V; Harilal, S S; Nampoori, V P N; Vallabhan, C P G(Springer-Verlag, 2000)
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Abstract:
Optical limiting and thermal lensing studies are
carried out in C70–toluene solutions. The measurements are
performed using 9-ns pulses generated from a frequencydoubled
Nd:YAG laser at 532 nm. Optical limiting studies in
fullerene molecules lead to the conclusion that reverse saturable
absorption is the major mechanism for limiting. Analysis
of thermal lensing measurements showed a quadratic
dependence of thermal lens signal on incident laser energy,
which also supports the view that optical limiting in C70 arises
due to sequential two-photon absorption via excited triplet
state (reverse saturable absorption).
Hunagund,P V; Jose,K A; Mohanan,P; Nair,K G(Indian Journal of Radio & Space Physics, February , 1992)
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Abstract:
Results of exhaustive study of the effect of metallic flanges on H-plane radiation characteristics of V-slot
waveguide antenna are presented . It has been established that the beam can be sharpened or broadened by
varying the flange angle . The adjustment of the flange angle and flange width would further improve the
radiation pattern , yielding optimum efficiency from the flanged system
Hector J,Thayil Kochukunnel; Arunachalam,P(Department of Applied Economics, 2006)
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Abstract:
The study was motivated by the need to understand factors that guide the software exports and competitiveness, both positively and negatively. The influence of one factor or another upon the export competitiveness is to be understood in great depth, which is necessary to find out the industry’s sustainability. India is being emulated as an example for the success strategy in software development and exports. India’s software industry is hailed as one of the globally competitive software industry in the world. The major objectives are to model the growth pattern of exports and domestic sales of software and services of India and to find out the factors influencing the growth pattern of software industry in India. The thesis compare the growth pattern of software industry of India with respect to that of Ireland and Israel and to critically of various problems faced by software industry and export in India and to model the variables of competitiveness of emerging software producing nations
Sindu,T K; Sankaran,P G(COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY, December , 2002)
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Abstract:
In the present environment, industry should provide the products of high quality. Quality of products is judged by the period of time they can successfully perform their intended functions without failure. The cause of the failures can be ascertained through life testing experiments and the times to failure due to different cause are likely to follow different distributions. Knowledge of this distribution is essential to eliminate causes of failures and thereby to improve the quality and the reliability of products. The main accomplishment expected to the study is to develop statistical tools that could facilitate solution to lifetime data arising in such and similar contexts
Madhu, K M; Dr. Chandrasekaran, M(Cochin University of Science and Technology, April , 2007)
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Abstract:
The beta-glucosidase enzyme purified from the marine fungus, Aspergillus
sydowii BTMFS 55 showed a good yield of enzyme production under solid state
fermentation. The statistical optimization of the media components revealed that
moisture content, concentration of peptone and inoculum are the major parameters
which supported the maximal enzyme production. The purified enzyme showed low
pH activity and stability, glucose tolerance and activation by ethanol. It could produce
ethanol from wheat bran and rice straw by simultaneous saccharification and
fermentation with yeast.The glucosidase purified from Aspergillus sydowii BTMFS 55
shows great potential for several biotechnological applications such as the production
of bio-ethanol from agricultural biomass and improvement in the aromatic character
of wines and fruit juices through the hydrolysis of flavour glucosidic precursors.
There is immense scope for the application of this marine fungus in the biofuel
production besides in other industries provided further studies are pursued in
exploiting this enzyme and the organism particularly scale up studies with respect to
application. There is also ample scope for cloning of the gene encoding beta-glucosidase
in domesticated hosts such as Pichia pastoris or S. cerevisiae that can produce ethanol
directly from cellulosic biomass.
Description:
Department of Biotechnology,
Cochin University of Science and Technology
Anas,A; Bright Singh,I S(Centre for Fish Disease Diagnosis and Management, School of Environmental Studies, 2005)
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Abstract:
Present work is aimed at development of an appropriate microbial technology for protection of larvae of macrobrachium rosenbergii from disease and to increase survival rate in hatcheries. Application of immunostimulants to activate the immune system of cultured animals against pathogen is the widely accepted alternative to antibiotics in aquaculture. The most important immunostimulant is glucan. Therefore a research programme entitled as extraction of glucan from Acremonium diospyri and its application in macrobrachium rosenbergii larval rearing system along with bacterians as microspheres. The main objectives of the study are development of aquaculture grade glucan from acremonium diospyri, microencapsulated drug delivery system for the larvae of M. rosenbergii and microencapsulated glucan with bacterian preparation for the enhanced production of M. rosenbergii in larval rearing system. Based on the results of field trials microencapsulated glucan with bacterin preparation, it is concluded that the microencapsulated preparation at a concentration of 25g per million larvae once in seven days will enhance the production and quality seed of M. rosenbergii.