Binoy, Paul; Dr.Girijavallabhan,C P(Cochin University of Science & Technology, February , 2004)
[+]
[-]
Abstract:
Nonlinear optical processes in organic compounds have attracted considerable interest in the field of science and technology because of their compelling technological promises in fields of optical communication,computing,switching and signal processing.As a result of the synthesis of novel organic compounds with varying degree of nonlinear optical strength, many practical devices based on these are getting realised giving new theoretical insights into the nonolinear optical behaviour of materials.Organic compounds like phthalocyanines and porphyrins have evoked great deal of interest in the field of photonic technology.The present thesis describes the results obtained from the investigations carried out on the nonlinear optical properties of certain organo-metallic compounds using Z-Scan and DFWM techniques.
Description:
International School of Photonics,
Cochin University of Science & Technology
Mridula, S; Dr.Mohanan, P(Cochin University Of Science And Technology, July 7, 2005)
[+]
[-]
Abstract:
The thesis relates to the investigations carried out on Rectangular Dielectric
Resonator Antenna configurations suitable for Mobile Communication applications.
The main objectives of the research are to:
- numerically compute the radiation characteristics of a Rectangular DRA
- identify the resonant modes
- validate the numerically predicted data through simulation and experiment
0 ascertain the influence of the geometrical and material parameters upon the
radiation behaviour of the antenna
° develop compact Rectangular DRA configurations suitable for Mobile
Communication applications
Although approximate methods exist to compute the resonant frequency of
Rectangular DRA’s, no rigorous analysis techniques have been developed so far to
evaluate the resonant modes. In this thesis a 3D-FDTD (Finite Difference Time
Domain) Modeller is developed using MATLAB® for the numerical computation of the radiation characteristics of the Rectangular DRA. The F DTD method is a
powerful yet simple algorithm that involves the discretimtion and solution of the
derivative form of Maxwell’s curl equations in the time domain.
Description:
Department of Electronics, Cochin University of Science and
Technology
Deepti Das, Krishna; Dr.Aanandan, C K(Cochin University of Science and Technology, September , 2010)
[+]
[-]
Abstract:
In recent years, there is a visible trend for products/services which demand
seamless integration of cellular networks, WLANs and WPANs. This is a
strong indication for the inclusion of high speed short range wireless technology
in future applications. In this context UWB radio has a significant role
to play as an extension/complement to existing cellular/access technology.
In the present work, we have investigated two major types of wide band
planar antennas: Monopole and Slot. Four novel compact broadband antennas,
suitable for poratble applications, are designed and characterized, namely
1. Elliptical monopole
2. Inverted cone monopole
3. Koch fractal slot
4. Wide band slot
The performance of these designs have been studied using standard simulation
tools used in industry/academia and they have been experimentally verified.
Antenna design guidelines are also deduced by accounting the resonances in
each structure.
In addition to having compact sized, high efficiency and broad bandwidth
antennas, one of the major criterion in the design of impulse-UWB systems
have been the transmission of narrow band pulses with minimum distortion.
The key challenge is not only to design a broad band antenna with constant
and stable gain but to maintain a flat group delay or linear phase response
in the frequency domain or excellent transient response in time domain. One
of the major contributions of the thesis lies in the analysis of the frequency
and time-domain response of the designed UWB antennas to confirm their
suitability for portable pulsed-UWB systems. Techniques to avoid narrowband
interference by engraving narrow slot resonators on the antenna is also
proposed and their effect on a nano-second pulse have been investigated.
Description:
Department of Electronics,
Faculty of Technology,
Cochin University of Science and Technology
Suma,M N; Dr.Mohanan, P(Cochin University of Science & Technology, January , 2008)
[+]
[-]
Abstract:
The space constraints on wireless gadgets is a challenge to antenna designers as the ground plane dimensions of the printed monopole significantly affect s the antenna characteristics.Investigations on ground plane truncations have led to the development of an extremely broad band printed monopole antenna.Omnidirectional radiation characteristics with moderate gain makes this antenna highly suitable for mobile/wireless applications .This thesis also highlights the development of UWB printed antenna along with design equations .Optimum ground plane dimensions for compact antenna applications,folding technique for miniaturization and double folding for dual band application are the other highlights of this thesis.
Description:
Department of Electronics,
Cochin University of Science and Technology
Mathiazhagan, A; Dr.Rani,Joseph; Dr.Narayanan, K P(Cochin University of Science & Technology, January , 2011)
[+]
[-]
Abstract:
Brasses are widely used as constructional materials in marine environment due to their anticorrosive,antifouling and mechanical properties.However, its resistance to corrosion and fouling may vary according to local marine environmental condition and the seasons.The dezincification of brass is one of the forms of selective corrosion which has attracted the attention of researchers for the last two decades.Many of the dezincification mechanistic studies have been performed in noncomplex media and hence their conclusions cannot be extended to esturine water,which is of great significance since brass is extensively used in marine environment.Inhibited α brasses are largely immune to dezincication and the effect of tin and arsenic addition to α/beta brasses is not so reliable in controlling the dezincification. There have been many cases of dezincification in duplex brasses in both freshwater and seawater.Though there is some protection methods such as inhibitors,electro deposition and electro polymerization,there is no reliable method of inhibiting the dezincification of two-phase brass.Organic coatings are effectively used for the protection metals due to their capacity to act a physical barrieer between the metal surface and corrosive environment.Hence,pure epoxy coating is selected for this as it has antocorrosiion effect on brass.The dezincification behaviour of brass of the present study has been highlighted in terms of corrosion rate,weight gain/loss,corrosion current and polarization resistence,open circuit potential,dezincification factor. The marine fouling as biomass on brass was assessed and presented in this thesis, The physicochemical properties of estuarine water were correlated with corrosion behaviour of brass.The deterioration of the brass subjected to the effect of estuarine water was also investigated as a measure of loss in mechanical properties such as tensile strength,yield strength,percntage elongation and percentage reduction in area.To validate dezincification data,visual observation,spot analysis,surface morphology before and after removal of corrosion products and corrosion product analysis were performed.The dezincification behavior of epoxy coated brass of the present study has beenhighlighted in terms of corrosion rate ,weight gain/loss,corrosion current and polarization resistance,open circuit potential.dezincification factor.The marine fouling as biomass on epoxy coated brass subjeted to the effect of estuarine water was also investigated as ameasure of loss in mechanical properties such as tensile strength,percentage elongation and percentage reduction in area.The results of dezincification behavior of brass and epoxy coated brass in Cochin estuary water has been presented and discussed.Attempt has been made to correlate the dezincification behavior of brass with epoxy coated brass.
Description:
Dept.of Ship Technology,Cochin University of Science and Technology
Geetha K, Varier; Dr.Nampoori,V P N(Cochin University of Science and Technology, April 28, 1998)
[+]
[-]
Abstract:
Light in its physical and philosophical sense has captured the imagination of human
mind right from the dawn of civilization. The invention of lasers in the 60’s caused
a renaissance in the field of optics. This intense, monochromatic, highly directional
radiation created new frontiers in science and technology. The strong oscillating electric
field of laser radiation creates a. polarisation response that is nonlinear in character in
the medium through which it passes and the medium acts as a new source of optical
field with alternate properties. It was in this context, that the field of optoelectronics
which encompasses the generation, modulation, transmission etc. of optical radiation
has gained tremendous importance. Organic molecules and polymeric systems have
emerged as a class of promising materials of optoelectronics because they offer the
flexibility, both at the molecular and bulk levels, to optimize the nonlinearity and
other suitable properties for device applications. Organic nonlinear optical media,
which yield large third-order nonlinearities, have been widely studied to develop optical
devices like high speed switches, optical limiters etc.
Transparent polymeric materials have found one of their most promising applicationsin
lasers, in which they can be used as active elements with suitable laser dyes
doped in it. The solid-matrix dye lasers make possible combination of the advantages
of solid state lasers with the possibility of tuning the radiation over a broad spectral
range. The polymeric matrices impregnated with organic dyes have not yet widely
used because of the low resistance of the polymeric matrices to laser damage, their low
dye photostability, and low dye stability over longer time of operation and storage.
In this thesis we investigate the nonlinear and radiative properties of certain organic
materials and doped polymeric matrix and their possible role in device development
Description:
International School of Photonics, Cochin University of Science & Technology
Shynu, S V; Vasudevan, K(Cochin University of Science & Technology, October , 2006)
[+]
[-]
Abstract:
In this work,we investigate novel designs of compact electronically reconfigurable dual frequency microstrip antennas with a single feed,operating mainly in L-band,without using any matching networks and complicated biasing circuitry.These antennas have been designed to operate in very popular frequency range where a great number of wireless communication applications exist.Efforts were carried out to introduce a successful,low cost reconfigurable dual-frequency microstrip antenna design to the wireless and radio frequency design community.
Description:
Department of Electronics,
Cochin University of Science and Technology
Indu Sebastian; Dr. Sheenu Thomas(Cochin University of Science and Technology, August 10, 2014)
[+]
[-]
Abstract:
Among various optical sensing schemes, infrared spectroscopy is a powerful tool for detecting and determining the composition of complex organic samples since vibrational finger prints of all biomolecules and organic species are located in this window. This spectroscopic technique is simple, reliable, fast, non-destructive, cost-effective while having low sensitivity. Use of metallic nanoparticles in association with a good IR transparent sensing substrate, is one of the promising solutions to enhance the sensitivity.
Chalcogenide glasses are promising substrate material because of their extended optical transmission window starting from the visible to the far infrared range up to 20 μm, high refractive index usually between 2 and 3 and high optical nonlinearity, which make them good candidates as IR sensors and optical ultrafast nonlinear devices. These glasses are favorable sensor materials for the infrared spectral range because of their high IR transparency to allow for low optical loss at wavelengths corresponding to the characteristic optical absorption bands of organic molecules, high refractive index for tight confinement of optical energy within the resonator structure, processibility into thin film form, chemical compatibility for adhesion of silver nano particles and thin films and resistance to the chemical environment to be sensed. Molecules adsorbed to silver island structures shows enhanced IR absorption spectra and the extent of enhancement is determined by many factors such as the size, density and morphology of silver structures, optical and dielectric properties of the substrate material etc.
Binoy,G S; Dr.Vasudevan, K(Cochin University of Science & Technology, June , 2002)
[+]
[-]
Abstract:
The thesis is the outcome of the experimental and theoretical investigations carried out on a novel slotted microstrip antenna.The antenna excites two resonance frequencies and provides orthogonal polarization. The radiation characteristics of the antenna are studied in detail. The antenna design is optimized using IE3D electromagnetic simulation tool. The frequency-Difference Time-Domain (FDTD) method is employed for the analysis of the antenna.The antenna can be used for personal and satellite communication applications.
Description:
Department of Electronics, Cochin University of Science and Technology.
Manju Dominic; Dr C.G. Nandakumar(Cochin University of Science and Technology, February 12, 2016)
[+]
[-]
Abstract:
Composite materials have emerged as a superior structural material having application in
all spheres of life. These have applications in every sector and essentially in marine
environment, where high strength to weight ratio and noncorrosive nature of the material
has great importance. Subsequently there has been a major shift in use of structural
materials from steel to composite materials in marine structures. Composite materials are
engineered materials made from two or more constituent materials that are combined at a
macroscopic level to produce a material with characteristics different from the individual
components. When both the matrix and fibre are not of metallic origin, such composites
are called as nonmetallic composites. Glass Fibre Reinforced Polymers (GFRP), Carbon
Fibre Reinforced Polymers (CFRP) and Aramid Fibre Reinforced Polymers (AFRP) are
common nonmetallic composite materials used for marine structural applications. These
are used in laminate form in ship hull construction.In the present study, a design philosophy based on strength and sustainability of
composite laminates has been proposed for selection of composites for ship hull
construction. For this purpose, an index based on strength of composite laminates and an
index based on sustainability of composites has been tabulated and materials need to be
selected based on these indices. Both the indices had been constructed as a composite
indicator. Index based on strength called as ‘Strength Index’ has been developed based on
the index values of various strength parameters. Index based on sustainability called as
‘Sustainability index’ has been developed based on the index values of the composites
based on the environmental impact of various phases of a ship’s life cycle. Nine non
metallic composites have been considered in the present study. Accordingly strength
parameters identified are bending strength, buckling strength and impact strength have
been found out. Environmental impact during the manufacturing phase and disposal phase
of composites has been found out. Based on these index values, indices based on strength
and sustainability has been constructed respectively. Based on these indices, ranks have
been assigned in such a way that, lower rank corresponds to higher strength and lower
environmental impact. This also means lower the rank, higher the acceptability of the composite laminates. Using these two indices a two dimensional assessment of
composites has been conducted. In this study both the indices have been superimposed to
get strength index versus sustainability index plot. Analysis of this plot is the core of the
design philosophy, ‘Design for strength and sustainability’. According to this design
philosophy, the composite which has the least strength index and sustainability index
rank should be selected for designing so that the structure will be strong and at the same
time have a low impact on the environment. This procedure can be extended to any
number of composites in the marine area or to composites that has application in other
areas.