Radhakrishnan, P; V P N Nampoori; Girijavallabhan, C P; Nibu, A George; George, A K(Journal of Physics D : Applied Physics, October 13, 2000)
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Abstract:
We report on a laser induced photoacoustic study of the nematic-to-isotropic
transition in certain commercial nematic liquid crystal mixtures, namely BL001, BL002,
BL032 and BL035. A simple analysis of the experimental data using the
Rosencwaig–Gersho theory shows that the heat capacities of all these compounds exhibit a
sharp peak as the temperature of the sample is varied across the transition region. Also,
substantial differences in the photoacoustic signal amplitudes in nematic and isotropic phases
have been noticed for all the mixtures. The increased light scattering property of the nematic
phase may be the reason for the enhanced photoacoustic signal amplitude in this phase
Babu, K K; Dr. Beena, K S(Cochin University of Science and Technology, May , 2007)
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Abstract:
The increasing tempo of construction activity the world over creates heavy pressure
on existing land space. The quest for new and competent site often points to the needs
for improving existing sites, which are otherwise deemed unsuitable for adopting
conventional foundations. This is accomplished by ground improvement methods,
which are employed to improve the quality of soil incompetent in their natural state.
Among the construction activities, a well-connected road network is one of the basic
infrastructure requirements, which play a vital role for the fast and comfortable
movement of inter- regional traffic in countries like India.One of the innovative ground improvement techniques practised all over the world is
the use of geosynthetics, which include geotextiles, geomembranes, geogrids, etc .
They offer the advantages such as space saving, enviromnental sensitivity, material
availability, technical superiority, higher cost savings, less construction time, etc .
Because of its fundamental properties, such as tensile strength, filtering and water
permeability, a geotextile inserted between the base material and sub grade can
function as reinforcement, a filter medium, a separation layer and as a drainage
medium. Though polymeric geotextiles are used in abundant quantities, the use of
natural geotextiles (like coir, jute, etc.) has yet to get momentum. This is primarily
due to the lack of research work on natural geotextilcs for ground improvement,
particularly in the areas of un paved roads. Coir geotextiles are best suited for low cost
applications because of its availability at low prices compared to its synthetic
counterparts. The proper utilisation of coir geotextilcs in various applications demands large quantities of the product, which in turn can create a boom in the coir
industry. The present study aims at exploring the possibilities of utilising coir
geotextiles for unpaved roads and embankments.The properties of coir geotextiles used have been evaluated. The properties studied
include mass per unit area, puncture resistance, tensile strength, secant modulus, etc .
The interfacial friction between soils and three types of coir geotextiles used was also
evaluated. It was found that though the parameters evaluated for coir geotextiles have
low values compared to polymeric geotextiles, the former are sufficient for use in
unpaved roads and embankments. The frictional characteristics of coir geotextile - soil
interfaces are extremely good and satisfy the condition set by the International
Geosynthetic Society for varied applications.The performance of coir geotextiles reinforced subgrade was studied by conducting
California Bearing Ratio (CBR) tests. Studies were made with coir geotextiles placed
at different levels and also in multiple layers. The results have shown that the coir
geotextile enhances the subgrade strength. A regression analysis was perfonned and a
mathematical model was developed to predict the CBR of the coir geotextile
reinforced subgrade soil as a function of the soil properties, coir geotextile properties,
and placement depth of reinforcement.The effects of coir geotextiles on bearing capacity were studied by perfonning plate
load tests in a test tan1e This helped to understand the functioning of geotextile as
reinforcement in unpaved roads and embankments. The perfonnance of different
types of coir geotextiles with respect to the placement depth in dry and saturated
conditions was studied. The results revealed that the bearing capacity of coir-reinforced soil is increasing irrespective of the type of coir geotextiles and saturation
condition.The rut behaviour of unreinforced and coir reinforced unpaved road sections were
compared by conducting model static load tests in a test tank and also under repetitive
loads in a wheel track test facility. The results showed that coir geotextiles could
fulfill the functions as reinforcement and as a separator, both under static and
repetitive loads. The rut depth was very much reduced whik placing coir geotextiles
in between sub grade and sub base.In order to study the use of Coir geotextiles in improving the settlement
characteristics, two types of prefabricated COlf geotextile vertical drains were
developed and their time - settlement behaviour were studied. Three different
dispositions were tried. It was found that the coir geotextile drains were very effective
in reducing consolidation time due to radial drainage. The circular drains in triangular
disposition gave maximum beneficial effect.In long run, the degradation of coir geotextile is expected, which results in a soil -
fibre matrix. Hence, studies pertaining to strength and compressibility characteristics
of soil - coir fibre composites were conducted. Experiments were done using coir
fibres having different aspect ratios and in different proportions. The results revealed
that the strength of the soil was increased by 150% to 200% when mixed with 2% of
fibre having approximately 12mm length, at all compaction conditions. Also, the
coefficient of consolidation increased and compression index decreased with the
addition of coir fibre.Typical design charts were prepared for the design of coir geotextile reinforced
unpaved roads. Some illustrative examples are also given. The results demonstrated that a considerable saving in subase / base thickness can he achieved with the use of
eoir geotextiles, which in turn, would save large quantities of natural aggregates.
Description:
Division of Civil Engineering,
Cochin University of Science and Technology
Rani, Joseph(Gordon and Breach Science Publishers S.A., October 16, 1992)
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Abstract:
Butyl (IIR) tube reclaim (RR) was mixed with carbon black filled natural rubber (NR) compounds at
various percentages. The blend containing a low percentage of RR was found to show improved ageing
resistance and improved processability with out much reduction in the mechanical properties.
Rani, Joseph(Huthig & Wepf Verlag,Basel, April 16, 1993)
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Abstract:
Scrap latex products contain rubber hydrocarbon of very high quality, that is only
slightly crosslinked. A novel economic technique for converting such latex waste into
a processible material is developed. This paper reports the effect of adding this latex
reclaim to natural rubber. It is shown that latex reclaim can replace raw natural rubber
up to about 50 wt.% without affecting mechanical properties.
Waste latex products are converted to a processabto material by a novel
economical process developed in our laboratory , It contains rubber hydrocarbon
of very high quality and Is lightly cross -linked. Styrene-butadlene
rubber is mixed with latex reclaim In different proportions . The mechanical
properties are found to be improved up to 60 percent replacement of
styrene-butadlene rubber by latex reclaim . The curing of styrene-butadiene
rubber Is found to be accelerated by the addition of latex reclaim. The
processablllty study shows that the blends can be processed similar to
SBRINR blends.
Vacuum-ultraviolet (VUV) irradiation (kexc: 172 ± 12 nm) of polystyrene films in the presence of oxygen
produced not only oxidatively functionalized surfaces, but generated also morphological changes.
Whereas OH- and C=O-functionalized surfaces might be used for e.g. secondary functionalization,
enhanced aggregation or printing, processes leading to morphological changes open new possibilities of
microstructurization. Series of experiments made under different experimental conditions brought
evidence of two different reaction pathways: introduction of OH- and C=O-groups at the polystyrene
pathways is mainly due to the reaction of reactive oxygen species (hydroxyl radicals, atomic oxygen,
ozone) produced in the gas phase between the VUV-radiation source and the substrate. However,
oxidative fragmentation leading to morphological changes, oxidation products of low molecular weight
and eventually to mineralization of the organic substrate is initiated by electronic excitation of the
polymer leading to C–C-bond homolysis and to a complex oxidation manifold after trapping of the
C-centred radicals by molecular oxygen. The pathways of oxidative functionalization or fragmentation
could be differentiated by FTIR-ATR analysis of irradiated polystyrene surfaces before and after
washing with acetonitrile and microscopic fluorescence analysis of the surfaces secondarily
functionalized with the N,N,N-tridodecyl-triaza-triangulenium (TATA) cation. Ozonization of the
polystyrene leads to oxidative functionalization of the polymer surface but cannot initiate the
fragmentation of the polymer backbone. Oxidative fragmentation is initiated by electronic excitation of
the polymer (contact-mode AFM analysis), and evidence of the generation of intermediate C-centred
radicals is given e.g. by experiments in the absence of oxygen leading to cross-linking (solubility effects,
optical microscopy, friction-mode AFM) and disproportionation (fluorescence).
Vanadia/ceria catalysts (2–10 wt% of V2O5) were prepared by wet impregnation of ammonium metavanadate in oxalic acid solution. Structural characterization was done with energy dispersive X-ray analysis (EDX), powder X-ray diffraction (XRD), BET surface area measurements, FT-IR spectroscopy and nuclear magnetic spectral analysis (51V MASNMR). XRD and 51V MASNMR results show highly dispersed vanadia species at lower loadings and the formation of CeVO4 phase at higher V2O5 loading. The catalytic activity of catalysts was conducted in liquid phase oxidation of ethylbenzene with H2O2 as oxidant. The oxidation activity is increased with loading up to 8 wt% V2O5 and then decreased with further increase in V2O5 content to 10 wt%. Different vanadia species evidenced by various techniques were found to be selective towards ethylbenzene oxidation. The CeVO4 formation associated with increased concentration of vanadia on ceria results the production of acetophenone along with 2-hydroxyacetophenone.
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
Madhusoodana Kurup, B; Thomas, Joice V; Sreedevi, C(Indian Journal of Marine Sciences, September , 2006)
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Abstract:
Variations of the infaunal polychates populations due to bottom trawling were studied during December 2000 to November 2002 at depth ranging from 0-50 m along Cochin-Munambam area (Kerala, long. 76degree10'94" to 75degree 56' and lat.9degree58' to 10degree10'), in the southwest coast of India.Infaunal polychaetes from the sediment samples were collected both before and after experimental trawling in order to assess the variations on their abundance (no.m-2),biomass(g.m-2) and diversity due to bottom trawling .Highest variations in polychaetes were recorded at station 9 in May 2002 where polychaete abundance increased to 20710 no.m-2 after trawling from 2787 no.m-2 before trawling.Biomass showed highest variations at station 3 in December 2000 where biomass increased from 7.16g.m-2 recorded before trawling to 34.53 g.m-2 in the samples collected after trawling .Multivariate community analysis carried out based on both species abundance and biomass of plychaetes also confirm the wide variations in the similarities of the stations comparing both before and after trawling
V P N Nampoori; Litty, Irimpan; Radhakrishnan, P(Journal of Applied Physics, American Institute of Physics,, 2008)
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Abstract:
We describe the structure of luminescence spectrum in the visible region in nano-ZnO in colloidal
and thin film forms under weak confinement regime by modeling the transition from excited state
energy levels of excitons to their ground state. Measurements on nanocrystallites indicate the
presence of luminescence due to excitonic emissions when excited with 255 nm. The relevant
energy levels showing the transitions corresponding to the observed peaks in the emission spectrum
of ZnO of particle size 18 nm are identified.
Manju, Kurian; Sugunan, S(Elsevier, January , 2006)
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Abstract:
Wet peroxide oxidation (WPO) of phenol is an effective means for the production of diphenols, which are of great industrial importance. An added advantage of this method is the removal of phenol from wastewater effluents. Hydroxylation of phenol occurs efficiently over mixed iron aluminium pillared montmorillonites. An initial induction period is noticed in all cases. A thorough study on the reaction variables suggests free radical mechanism for the reaction.