Alice, Mathai; Dr.Nandakumar, C G(Cochin University of Science & Technology, November , 2004)
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Abstract:
Submarine hull structure is a watertight envelope, under hydrostatic pressure
when in operation. Stiffened cylindrical shells constitute the major portion of these
submarine hulls and these thin shells under compression are susceptible to buckling
failure. Normally loss of stability occurs at the limit point rather than at the
bifurcation point and the stability analysis has to consider the change in geometry at
each load step. Hence geometric nonlinear analysis of the shell forms becomes. a
necessity. External hydrostatic pressure will follow the deformed configuration of the
shell and hence follower force effect has to be accounted for.
Computer codes have been developed based on all-cubic axisymmetric
cylindrical shell finite element and discrete ring stiffener element for linear elastic,
linear buckling and geometric nonIinear analysis of stiffened cylindrical shells. These
analysis programs have the capability to treat hydrostatic pressure as a radial load
and as a follower force.
Analytical investigations are carried out on two attack submarine cylindrical
hull models besides standard benchmark problems. In each case, the analysis has
been carried out for interstiffener, interdeepframe and interbulkhead configurations.
The shell stiffener attachment in each of this configuration has been represented by
the simply supported-simply supported, clamped-clamped and fixed-fixed boundary
conditions in this study.
The results of the analytical investigations have been discussed and the
observations and conclusions are described. Rotation restraint at the ends is
influential for interstiffener and interbulkhead configurations and the significance of
axial restraint becomes predominant in the interbulkhead configuration. The follower
force effect of hydrostatic pressure is not significant in interstiffener and
interdeepframe configurations where as it has very high detrimental effect on
buckling pressure on interbulkhead configuration. The geometric nonlinear
interbulkhead analysis incorporating follower force effect gives the critical value of
buckling pressure and this analysis is recommended for the determination of collapse
pressure of stiffened cylindrical submarine shells.
Description:
Dept.of Ship Technology,Cochin University of Science & Technology
Rajagopalan, S; Dr. Sabir, M(Cochin University Of Science And Technology, March 4, 2002)
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Abstract:
The study of simple chaotic maps for non-equilibrium processes in statistical
physics has been one of the central themes in the theory of chaotic dynamical
systems. Recently, many works have been carried out on deterministic diffusion
in spatially extended one-dimensional maps This can be related to real physical
systems such as Josephson junctions in the presence of microwave radiation and
parametrically driven oscillators. Transport due to chaos is an important problem
in Hamiltonian dynamics also. A recent approach is to evaluate the exact diffusion
coefficient in terms of the periodic orbits of the system in the form of cycle
expansions. But the fact is that the chaotic motion in such spatially extended maps
has two complementary aspects- - diffusion and interrnittency. These are related
to the time evolution of the probability density function which is approximately
Gaussian by central limit theorem. It is noticed that the characteristic function
method introduced by Fujisaka and his co-workers is a very powerful tool for
analysing both these aspects of chaotic motion. The theory based on characteristic
function actually provides a thermodynamic formalism for chaotic systems
It can be applied to other types of chaos-induced diffusion also, such as the one
arising in statistics of trajectory separation. It was noted that there is a close connection
between cycle expansion technique and characteristic function method. It
was found that this connection can be exploited to enhance the applicability of
the cycle expansion technique. In this way, we found that cycle expansion can be
used to analyse the probability density function in chaotic maps. In our research
studies we have successfully applied the characteristic function method and cycle
expansion technique for analysing some chaotic maps. We introduced in this
connection, two classes of chaotic maps with variable shape by generalizing two
types of maps well known in literature.
Description:
Department of Physics, Cochin University of Science and Technology
Maya L Pai; Dr. A N Balchand; Dr. K V Pramod(Cochin University of Science and Technology, May 12, 2016)
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Abstract:
ANN based long range forecast of Indian summer monsoon rainfall for
the hydrological regions of India using ocean and atmosphere state
parameters with improved accuracy,Trend analysis of SST, sub surface temperature of Indian Ocean and
that of ISMR.
3. Prediction of extreme rainfall events using ANN.
Jayaprakash, N S; Bright Singh, I S(School of Environmental Studies, 2005)
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Abstract:
The main objective of the work undertaken here was to develop an appropriate microbial technology to protect the larvae of M.rosenbergii in hatchery from vibriosis. This technology precisely is consisted of a rapid detection system of vibrios and effective antagonistic probiotics for the management of vibrios. The present work was undertaken with the realizations that to stabilize the production process of commercial hatcheries an appropriate, comprehensive and fool proof technology is required primarily for the rapid detection of Vibrio and subsequently for its management. Nine species of Vibrio have been found to be associated with larvae of M. rosenbergii in hatchery. Haemolytic assay of the Vibrio and Aeromonas on prawn blood agar showed that all isolates of V. alginolyticus and Aeromonas sp., from moribund, necrotized larve were haemolytic and the isolates of V.cholerae, V.splendidus II, V.proteolyticus and V.fluvialis from the larvae obtained from apparently healthy larval rearing systems were non-haemolytic.
Hydrolytic enzymes such as lipase, chitinase and gelatinase were widespread amongst the Vibrio and Aeromonas isolates. Dominance of V.alginolyticus among the isolates from necrotic larvae and the failure in isolating them from rearing water strongly suggest that they infect larvae and multiply in the larval body and cause mortality in the hatchery. The observation suggested that the isolate V. alginolyticus was a pathogen to the larvae of M.rosenbergii. To sum up, through this work, nine species of Vibrio and genus Aeromonas associated with M.rosenbergii larval rearing systems could be isolated and segregated based on the haemolytic activity and the antibodies (PA bs) for use in diagnosis or epidemiological studies could be produced, based on a virulent culture of V.alginolyticus. This could possibly replace the conventional biochemical tests for identification. As prophylaxis to vibriosis, four isolates of Micrococcus spp. and an isolate of Pseudomonas sp. could be obtained which could possibly be used as antagonistic probiotics in the larval rearing system of M.rosenbergii.