Litty, Irimpan; Deepthy, A; Bindu, Krishnan; V P N Nampoori; Radhakrishnan, P(Springer, 2008)
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Abstract:
In the present work, we have investigated the nonlinear
optical properties of self-assembled films formed from
ZnO colloidal spheres by z-scan technique. The sign of the nonlinear
component of refractive index of the material remains
the same; however, a switching from reverse saturable absorption
to saturable absorption has been observed as the material
changes from colloid to self-assembled film. These different
nonlinear characteristics can be mainly attributed to ZnO defect
states and electronic effects when the colloidal solution is
transformed into self-assembled monolayers. We investigated
the intensity, wavelength and size dependence of saturable and
reverse saturable absorption of ZnO self-assembled films and
colloids. Values of the imaginary part of third-order susceptibility
are calculated for particles of size in the range 20–300 nm
at different intensity levels ranging from 40 to 325MW/cm2
within the wavelength range of 450–650 nm.
The principal objective of this study was to explore the compatibility of a blend of
two synthetic elastomers viz., ethylene-propylene-diene rubber (EPDM) and
chlorobutyl rubber (CIIR). Various commercial grades of EPDM were blended
with a specific grade of CIIR at different proportions. The mechanical properties such
as tensile strength, tear strength, ageing resistance, etc. were studied. On the basis of
the observed physical properties, two particular grades of EPDM were found to be compatible
with CIIR. Differential scanning calorimetry and scanning electron microscopy
confirmed the results. Chlorosulphonated polyethylene was added as a compatibilizing
agent to overcome the phase separation of the other two incompatible grades of EPDM
in blending with CIIR. The results revealed that the addition of compatibilizer greatly
improves the compatibility and thereby the properties of the blends.
V P N Nampoori; Samuel, Varghese; Suresh, Nair; Girijavallabhan, C P(Elsevier, Journal of Optics Communications, November 26, 2008)
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Abstract:
A new method for the fabrication of high uniformity monolithic 1 x 4 single mode fused coupler is
described together with details of its performance in terms of coupling ratio, spectral response and uniformity.
The fabricated device exhibits ultra-broadband performance with a port-to-port uniformity of
0.4 dB. The reliability of such couplers is also evaluated and found to have good stability. Moreover, by
controlling the process parameters it is possible to control the power remaining in the through put port
of the device, which can be used for dedicated non-intrusive network health monitoring.
Girijavallabhan, C P; V P N Nampoori; Suresh, Nair; Samuel, Varghese(Elsevier, Journal of Optics Communications, November 26, 2008)
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Abstract:
A new method for the fabrication of high uniformity monolithic 1 x4 single-mode fused coupler is
described together with details of its performance in terms of coupling ratio, spectral response and uniformity.
The fabricated device exhibits ultra-broadband performance with a port-to-port uniformity of
0.4 dB. The reliability of such couplers is also evaluated and found to have good stability. Moreover, by
controlling the process parameters it is possible to control the power remaining in the through put port
of the device, which can be used for dedicated non-intrusive network health monitoring
V P N Nampoori; Lyjo, K Joseph; Suja, H; Sanjay, G; Sugunan, S; Radhakrishnan, P(Elsevier, Journal of Applied Clay Science, June 28, 2008)
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Abstract:
Thermal diffusivity (TD) measurement on commercial K-10 and KSF montmorillonites was carried out by
photoacoustic technique. The TD of the montmorillonites after methylene blue adsorption changed with the
dye concentration. The repeatedly adsorbed samples showed a lesser TD than the single adsorbed samples.
After methylene blue adsorption the acid leached K-10 samples showed well defined changes in TD when
compared to the ordered KSF samples.
Jacob, Philip; Manjusha, M V(Taylor & Francis, 2008)
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Abstract:
The thermal transport properties, thermal diffusivity, thermal conductivity and specific heat
capacity of Dicalcium Lead Propionate (DLP) crystal have been measured following a modified
photopyroelectric thermal wave method. The measurements have been carried out with
thermal waves propagating along the three principal symmetry directions, so as to bring out the
anisotropy in these parameters. The variations of the above parameters through two prominent
phase transition temperatures of this crystal have also been measured to understand the variation
of these parameters as it undergoes ferroelectric phase transitions. In addition, complete
thermal analysis and FTIR measurements have been done on the crystal to bring out the correlation
of these results with the corresponding thermal transport properties. All these results are
presented and discussed. The data presented in this paper form a comprehensive set of results
on the thermal transport properties of this crystal.