Sreekumar, K; Elizabeth, Chirackal Varkey(Wiley, July 20, 2010)
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Abstract:
The toluene diisocyanate based optically
active chiral polyurethanes were synthesized according to
the symmetry conditions. The noncentrosymmetric (both
charge asymmetry and spatial asymmetry) environment
were attained by the incorporation of the chiral units
(diethyl-(2R,3R)(þ)-tartrate) and donor-acceptor building
blocks in the main chain which induce a helical conformation
in the macromolecular chain. A series of optically
active polyurethanes containing chiral linkages in the
polymer back bone have been synthesized by using
DBTDL catalyst by incorporating the amido diols which
were obtained by the aminolysis of e-caprolactone by
using the diamines, diaminoethane, diaminobutane, and
diaminohexane respectively. The effect of incorporation of
the chiral molecule diethyl-(2R,3R)(þ)-tartrate on the properties
of polyurethanes was studied by changing the chromophores
and also by varying the chiral-chromophore
composition. Various properties of polyurethanes were
investigated by UV, Fluorescence, TG/DTA, XRD, polarimetric
techniques, Kurtz-Perry powder techniques, etc.
Description:
Journal of Applied Polymer Science, Vol. 119, 111–119 (2011)
Harilal, S S; Girijavallabhan, C P(Cochin University of Science and Technology, 1997)
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Abstract:
This thesis is entitled “OPTICAL EMISSION DIAGNOSTICS OF LASER PRODUCED PLASMA FROM GRAPHITE AND YBa2Cu3O7. The work presented in this thesis covers the experimental results on the plasma produced with moderately high power laser with irradiance range in between 10 GW cm 2 to 100 GW cm -2. The characterization of laser produced plasma from solid targets viz. graphite and high temperature superconducting material like YBa2Cu3O7 have been carried out. The fundamental frequency from a Q - switched Nd: YAG laser with 9 ns pulse
duration is used for the present studies. Various optical emission emission diagnostic techniques were employed for the the characterization of the LPP which include emission spectroscopy, time resolved studies, line broadening method etc. In order to understand the physical nature of the LPP like recombination, collisional excitation and the laser interaction with plasma, the time resolved studies offer the most logical approach
Optical emission spectroscopic studies were carried out on the plasma produced by ablation of zinc
oxide target using the third harmonic 355 nm of Q-switched Nd:YAG laser, in vacuum and at three
different ambient gas oxygen pressures. The spatial variations of electron density Ne and electron
temperature Te were studied up to a distance of 20 mm from the target surface. The kinematics of
the emitted particles and the expansion of the plume edge are discussed. The optimum conditions
favorable for the formation of high quality zinc oxide thin films are thereby suggested.
Girijavallabhan, C P; Nampoori, V P N; Harilal, S S; Riju, C Issac; Bindhu, C V(Journal of Physics D : Applied Physics, January 24, 1997)
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Abstract:
Optical emission studies of C2 molecules in plasma obtained by Nd:YAG
laser ablation of graphite in a helium atmosphere are reported for irradiances in the
range (1–9:2/ x 1010 W cm−2. The characteristics of the spectral emission intensity
from the C2 (Swan band) species have been investigated as functions of the
distance from the target, ambient pressure and laser irradiance. Estimates of
vibrational temperatures of C2 species under various irradiance conditions are
made. Results of measurements performed under different ambient helium gas
pressures are also discussed.
Nampoori, V P N; Girijavallabhan, C P; Harilal, S S; Riju, C Issac; Bindhu, C V(Journal of Physics D : Applied Physics, January 24, 1997)
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Abstract:
Optical emission studies of C2 molecules in plasma obtained by Nd:YAG
laser ablation of graphite in a helium atmosphere are reported for irradiances in the
range (1–9:2/ x 1010 W cm−2. The characteristics of the spectral emission intensity
from the C2 (Swan band) species have been investigated as functions of the
distance from the target, ambient pressure and laser irradiance. Estimates of
vibrational temperatures of C2 species under various irradiance conditions are
made. Results of measurements performed under different ambient helium gas
pressures are also discussed.
Deepa, Jose; Shelly John, M; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(Elsevier, July 18, 1998)
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Abstract:
A novel fibre optic sensor for the in situ measurement of the rate of deposition of thin films has been developed. Evanescent wave in the uncladded portion of a multimode fibre is utilised for this sensor development. In the present paper we demonstrate how this sensor is useful for the monitoring of the deposition rate of polypyrrole thin films, deposited by an AC plasma polymerisation method. This technique is simple, accurate and highly sensitive compared with existing techniques.
Anantharaman, M R; Suchand Sandeep, C S; Jinto, Thomas; Reji, Philip; Swapna, Nair S(AIP Publishing, May 1, 2008)
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Abstract:
We report an optical limiter based on ferrofluids which has a very high shelf life and remarkable
thermal stability, which are important requirements for sustainable use with intense lasers. The
colloidal suspensions contain nanosized particles of approximately 80 Å diameter, with a number
density of the order of 1022 /m3. The nonlinear optical transmission of the samples is studied using
nanosecond and femtosecond laser pulses. Excited state absorption phenomena contribute to
enhanced limiting in the nanosecond excitation regime. An advantageous feature of ferrofluids in
terms of device applications is that their optical properties are controllable by an external magnetic
field.
Harilal, S S; Bindhu, C V; Nampoori, V P N; Vallabhan, C P G(American Institute of Physics, 1999)
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Abstract:
Optical limiting and thermo-optic properties of C60 in toluene are studied using 532 nm, 9 ns pulses from a frequency-doubled Nd:YAG laser. Optical limiting studies in these fullerene molecules lead to the conclusion that reverse saturable absorption is the major mechanism for limiting properties in these molecules. Thermal lensing measurements are also performed in fullerene solutions. The quadratic dependence of thermal lens signal on incident energy confirms that enhanced optical absorption by the sample via excited triplet state absorption may play a leading role in the limiting property.
Aneeshkumar, B; Pramod, Gopinath; Vallabhan, C P G; Nampoori, V P N; Radhakrishnan, P(Optical Society of America, July , 2003)
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Abstract:
The nanosecond optical-limiting characteristics (at 532 nm) of some rare-earth metallo-phthalocyanines (Sm(Pc)2, Eu(Pc)2, and LaPc) doped in a copolymer matrix of poly(methyl methacrylate) and methyl-2-cyanoacrylate have been studied for the first time to our knowledge. The optical-limiting response is attributed to reverse saturable absorption due to excited-state absorption. The performance of LaPc in a copolymer host is studied at different linear transmissions. The laser damage thresholds of all the samples are also reported.
Anantharaman, M R; Senoy, Thomas; Sakthi Kumar, D; Joy, P A; Yasuhiko, Yoshida(IOP Publishing LTD, October 25, 2006)
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Abstract:
Composite Fe3O4–SiO2 materials were prepared by the sol–gel method with
tetraethoxysilane and aqueous-based Fe3O4 ferrofluids as precursors. The
monoliths obtained were crack free and showed both optical and magnetic
properties. The structural properties were determined by infrared
spectroscopy, x-ray diffractometry and transmission electron microscopy.
Fe3O4 particles of 20 nm size lie within the pores of the matrix without any
strong Si–O–Fe bonding. The well established silica network provides
effective confinement to these nanoparticles. The composites were
transparent in the 600–800 nm regime and the field dependent magnetization
curves suggest that the composite exhibits superparamagnetic characteristics
Kumar, G A; Thomas, J; Unnikrishnan, N V; Nampoori, V P N; Vallabhan, C P G(Elsevier, 2001)
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Abstract:
Optical absorption and emission spectral studies of various phthalocyanine molecules, viz., LaPc, NdPc, SmPc, EuPc, CuPc and ZnPc in a polymer matrix of cyano acrylate are reported for the first time. All the absorption spectra show an intense B band (Soret) in the UV region followed by a weaker Q band in the visible region. The positions of the Q and B bands are found to have dependence on the metallic substitution. Values of the important spectral parameters, viz., molar extinction coefficient (ϵ), oscillator strength (f), radiative transition rate and decay time of the excited singlet state are also presented and compared with other solid matrices. The recorded fluorescence spectrum shows two broad emission bands in the case of NdPc, whereas for ZnPc only a very weak band is observed. The absence of emission bands for the other metallated phthalocyanines is attributed to increased spin orbit interaction and intersystem crossing.
Kumar, G A; Vinoy, Thomas; Gin, Jose; Unnikrishnan, N V; Nampoori, V P N(Elsevier, 2002)
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Abstract:
Optical properties of free and substituted porphyrins (PP) doped borate glass matrix are reported for the first time. Absorption spectral measurements of H2TPP, CdTPP, MgTPP and ZnTPP doped borate glass matrix have been made in the 200–1100 nm region and the spectra obtained are analyzed to obtain the optical bandgap (Eg) and other important spectral parameters viz. oscillator strength (f), molar extinction coefficient (ε), electric dipole strength (q2), absorption cross-section (σa) and molecular concentration (N). Intense fluorescence was observed in the region 668–685 nm for CdTPP, ZnTPP and MgTPP doped matrices, whereas no such fluorescence was observed in H2TPP doped matrix. Fluorescence intensity was observed to be almost similar in all the metallated porphyrine matrices. Fluorescence bandwidth (Δλ), decay time (τ), stimulated emission cross-section (σ) and optical gain (G) of the principal fluorescence transitions corresponding to the Q-band excitation were also evaluated and discussed.
Thomas, J; Kumar, G A; Unnikrishnan, N V; Nampoori, V P N; Vallabhan, C P G(Elsevier, 2000)
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Abstract:
Optical absorption and emission spectral studies of various phthalocyanine (Pc) molecules in PVA matrix have been reported for the first time. The recorded spectra are analyzed to get the important spectral parameters, such as optical absorption cross-section (σa), emission cross-section (σe), oscillator strength (f), fluorescence bandwidth (Δλ), emission wavelength (λ), radiative decay time (τ) and optical gain (G). Analysis shows that the emission cross-section and optical gain are maximum in the NdHPc2-doped PVA matrix. However, a comparison of the calculated emission parameters with that of borate glass matrix show that they are many times smaller in the present matrix.
Jagathy Raj, V P; Praveen, R P; Ravichandran, M H; Sadasivan Achari, V T; Madhu, G; Bindu, G R; Dubas, F(IEEE, March 23, 2011)
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Abstract:
This paper presents the optimal design of a surface
mounted permanent-magnet (PM) Brushless direct-current
(BLDC) motor meant for spacecraft applications. The spacecraft
applications requires the choice of a motor with high torque
density, minimum cogging torque, better positional stability and
high torque to inertia ratio. Performance of two types of machine
configurations viz Slotted PMBLDC and Slotless PMBLDC with
Halbach array are compared with the help of analytical and
finite element (FE) methods. It is found that unlike a Slotted
PMBLDC motor, the Slotless type with Halbach array develops
zero cogging torque without reduction in the developed torque.
Moreover, the machine being coreless provides high torque to
inertia ratio and zero magnetic stiction
Description:
Emerging Trends in Electrical and Computer Technology (ICETECT), 2011 International Conference on
Krishnamoorthy,A; Vishwanath, Narayanan C; Deepak,T G(Korean Society for Computational & Applied mathematics, 2007)
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Abstract:
In this paper, we study a k-out-of-n system with single server
who provides service to external customers also. The system consists of
two parts:(i) a main queue consisting of customers (failed components of
the k-out-of-n system) and (ii) a pool (of finite capacity M) of external
customers together with an orbit for external customers who find the pool
full. An external customer who finds the pool full on arrival, joins the orbit
with probability
and with probability 1−
leaves the system forever. An
orbital customer, who finds the pool full, at an epoch of repeated attempt,
returns to orbit with probability (< 1) and with probability 1 − leaves
the system forever. We compute the steady state system size probability.
Several performance measures are computed, numerical illustrations are
provided.
Jude Martin, Mendez; Dr.George, K E(Cochin University of Science & Technology, October , 2009)
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Abstract:
This study was undertaken in order to upgrade blends of HDPE and
PP, two of the most widely used standard plastics so as to widen their
application spectrum. Dicumyl peroxide was used as the modifier for the
upgradation. Optimum concentration of dicumyl peroxide required for
modification was detennined by measurement of mechanical, rheological,
thermal and morphological properties. Selected blends were used to prepare
recyclable composites with nylon clothes by compression moulding. The
composites were characterized by measurement of mechanical and thermal
properties. The composites were recycled and the mechanical propertics of
the recycled material were determined.
Description:
Dept.of Polymer Science and Rubber Technology,
Cochin University of Science and technology
Rosamma, Philip; Preetha, R; Jayaprakash, N S; Bright Singh, I S(The Society for Applied Microbiology, 2007)
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Abstract:
Aim: To develop a new medium for enhanced production of biomass of an
aquaculture probiotic Pseudomonas MCCB 103 and its antagonistic phenazine
compound, pyocyanin.
Methods and Results: Carbon and nitrogen sources and growth factors, such as
amino acids and vitamins, were screened initially in a mineral medium for the
biomass and antagonistic compound of Pseudomonas MCCB 103. The selected
ingredients were further optimized using a full-factorial central composite
design of the response surface methodology. The medium optimized as per the
model for biomass contained mannitol (20 g l)1), glycerol (20 g l)1), sodium
chloride (5 g l)1), urea (3Æ3 g l)1) and mineral salts solution (20 ml l)1), and
the one optimized for the antagonistic compound contained mannitol (2 g l)1),
glycerol (20 g l)1), sodium chloride (5Æ1 g l)1), urea (3Æ6 g l)1) and mineral
salts solution (20 ml l)1). Subsequently, the model was validated experimentally
with a biomass increase by 19% and fivefold increase of the antagonistic
compound.
Conclusion: Significant increase in the biomass and antagonistic compound
production could be obtained in the new media.
Significance and Impact of the Study: Media formulation and optimization are
the primary steps involved in bioprocess technology, an attempt not made so
far in the production of aquaculture probiotics.