Ravindranathan, S; Dr.Unnikrishnan, A(Cochin University of Science & Technology, October , 1991)
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Abstract:
Neural Network has emerged as the topic of the day.
The spectrum of its application is as wide as from ECG noise
filtering to seismic data analysis and from elementary
particle detection to electronic music composition. The
focal point of the proposed work is an application of a
massively parallel connectionist model network for detection
of a sonar target. This task is segmented into: (i) generation of training patterns from sea noise that
contains radiated noise of a target, for teaching the
network;(ii) selection of suitable network topology and learning
algorithm and (iii) training of the network and its subsequent testing
where the network detects, in unknown patterns applied
to it, the presence of the features it has already
learned in. A three-layer perceptron using backpropagation
learning is initially subjected to a recursive training
with example patterns (derived from sea ambient noise with
and without the radiated noise of a target). On every
presentation, the error in the output of the network is
propagated back and the weights and the bias associated with
each neuron in the network are modified in proportion to
this error measure. During this iterative process, the network converges and extracts the target features which get
encoded into its generalized weights and biases.In every unknown pattern that the converged
network subsequently confronts with, it searches for the
features already learned and outputs an indication for their
presence or absence. This capability for target detection is
exhibited by the response of the network to various test
patterns presented to it.Three network topologies are tried with two
variants of backpropagation learning and a grading of the
performance of each combination is subsequently made.
Description:
Department of Electronics, Cochin University of Science and Technology
Thomas, Baby; Ramachandran, T; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(IOP Publishing, 1991)
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Abstract:
A low inductance, triggered spark gap switch suitable for a high-current fast discharge system has been developed. The details of the design and fabrication of this pressurized spark gap, which uses only commonly available materials are described. A transverse discharge Blumlein-driven N2 laser incorporating this device gives a peak output power of 700 kW with a FWHM of 3 ns and an efficiency of 0.51%, which is remarkably high for a pulsed nitrogen laser system.
Poulose Jacob, K; Dr. Sridhar, C S(Cochin University of Science & Technology, 1991)
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Abstract:
One of the fastest expanding areas of computer exploitation
is in embedded systems, whose prime function is not that of
computing, but which nevertheless require information
processing in order to carry out their prime function.
Advances in hardware technology have made multi
microprocessor systems a viable alternative to uniprocessor
systems in many embedded application areas.
This thesis reports the results of investigations carried out
on multi microprocessors oriented towards embedded
applications, with a view to enhancing throughput and
reliability.
An ideal controller for multiprocessor operation is developed
which would smoothen sharing of routines and enable more
powerful and efficient code I data interchange. Results of
performance evaluation are appended.A typical application scenario is presented, which calls for
classifying tasks based on characteristic features that were
identified. The different classes are introduced along with
a partitioned storage scheme. Theoretical analysis is also
given.
A review of schemes available for reducing disc access time
is carried out and a new scheme presented. This is found to
speed up data base transactions in embedded systems.
The significance of software maintenance and adaptation in
such applications is highlighted. A novel scheme of
prov1d1ng a maintenance folio to system firmware is
presented, alongwith experimental results.
Processing reliability can be enhanced if facility exists to
check if a particular instruction in a stream is appropriate.
Likelihood of occurrence of a particular instruction would be
more prudent if number of instructions in the set is less. A
new organisation is derived to form the basement for further
work. Some early results that would help steer the course of
the work are presented.
Description:
Department of Electronics,Cochin University of Science and Technology
Jayaraj, M K; Vallabhan, C P G(Thin Solid Films, 1991)
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Abstract:
The dielectric properties of electron beam evaporated Sm2O3 films have been
investigated in the frequency range from 1 kHz to 1 MHz at various temperatures
(300 K-453 K). The dielectric constant is found to depend on film thickness and it
attains a constant value beyond 1000 A. The present electron beam evaporated
Sm2O3 films have a high dielectric constant of 43. The frequency dependence of
and tan teeta at various temperatures is also studied.
Amritkar, R E; Gade, P M; Gangal, A D; Nandkumaran, V M(The American Physical Society, September , 1991)
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Abstract:
We consider the stability properties of spatial and temporal periodic orbits of one-dimensional coupled-map lattices. The stability matrices for them are of the block-circulant form. This helps us to reduce the problem of stability of spatially periodic orbits to the smaller orbits corresponding to the building blocks of spatial periodicity, enabling us to obtain the conditions for stability in terms of those for smaller orbits.
Sasi Kumar, P R; Padmaja, G; Ravi Kumar, A V; Nampoori, V P N; Vallabhan, C P G(Springer, April , 1991)
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Abstract:
Observation of laser induced two-photon photoemission optogalvanic (TPPOG) effect from tungsten electrode in a discharge cell using 564 nm radiation obtained from a pulsed dye laser is described. The magnitude of the POG signal is studied as a function of laser energy under various discharge parameters. Competition between one-photon and two-photon processes has been observed when nitrogen gas is used in the discharge cell.