Sudha Kartha, C; Dr.Sathianandan, K(Cochin University of Science and Technology, February , 1984)
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Abstract:
The present study is mainly concéntrated on the visible
fluorescence of Ho3+ ,nd 3+ and Er 3+rare earths in
alkaline earth fluoride hosts(caF2,srF2,BaF2)
using a nitrogen laser excitation. A nitrogen laser was fabricated and its parametric studies were first carried out.
Description:
Department of Physics, Cochin University of Science and Technology
Syed Aftab, Husain Rizvi; Dr.Wazir, Hasan Abdi(Cochin University of Science And Technology, March , 1984)
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Abstract:
This thesis is an attempt to throw light on the works
of some Indian Mathematicians who wrote in Arabic or
persian In the Introductory Chapter on outline of
general history of Mathematics during the eighteenth
Bnd nineteenth century has been sketched. During that
period there were two streams of Mathematical activity.
On one side many eminent scholers, who wrote in Sanskrit,
.he l d the field as before without being much influenced
by other sources. On the other side there were scholars
whose writings were based on Arabic and Persian text
but who occasionally drew upon other sources also.
Description:
Department of Mathematics and Statistics, Cochin University of Science and Technology
Muraleedharan,Pillai S; Dr.Girijavallabhan,C P(Cochin University of Science And Technology, March , 1984)
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Abstract:
The subject of electroluminescence has currently acquired great importance because of its potential applications in display systems of a wide variety. A large number of scientists working in commercial, governmental as well as academic institutions all over the world are at present
engaged in the intense effort to develop new and efficient phosphor materials and electroluminescent devices. This thesis presents the work carried out by the author in this
field during the past few years. The studies discussed in this thesis are mostly confined to
the development of some new phosphor materials, their uses in powder and thin film electroluminescent devices and to their electrical and spectral characteristics. Care has been taken to bring' out the physics involved in all the above aspects of the phenomenon
Description:
Department of physics, Cochin University of Science And Technology
Vijayakumar, K P; Dr.Purushothaman, C(Cochin University of Science and Technology, May 28, 1984)
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Abstract:
The thesis aims to present the results of experimental investigations on the changes of optical properties of metallic thin films due to heating. The parameters which are measured are reflectivity, refractive indices and the ellipsometric quantities V and A . The materials used in the studies are metals like Silver, Aluminium and Copper. By applying the optical method the interdiffusion taking place in multilayer
‘films of Aluminium and Silver has also been studied. Special interest has been taken to reveal the mechanisms of the hillock growth and surface roughness caused by heating and their relation with the stress in the film
Description:
Department of Physics, Cochin University of Science and Technology
Ramabhadran,P; Dr.Madhavan Pillai, P(Cochin University of Science and Technology, July , 1984)
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Abstract:
The study deals with the production of l-phenylflavazoles with chloro, amino, hydroxy,
chloromethyl, carboxamido, trichloromethyl, N-pyrrolidyl and N-pyrrolidylmethyl groups substituted at position 3. The interconversions of 3-amino, 3-hydroxy and 3-chlorol-
phenylflavazoles were also investigated. Further, an unusual phenylation reaction was found to take place if stored or air-oxidised phenylhydrazine was used as the condensing agent for the formation of flavazoles from quinoxaline-2-carboxaldehyde phenylhydrazones.
By this phenylation reaction 1,3-diphenyl, l-p-tolyl-3-phenyl, l-p-chlorophenyl-3-phenyl, l-p-bromophenyl- 3-phenyl and l-phenyl-3-p-tolylflavazoles were prepared. In addition to establishing the structure of the phenylation products, the reaction was shown to take place by a free radical mechanism involving phenyl radicals formed from oxidised phenylhydrazine.
Also the oxidation, reduction and bromination reactions of l-phenylflavazole were investigated. The product obtained when a mixture of l-phenylflavazole and sodium borohydride in isopropanol was heated under reflux was shown to be 2-anilinoquinoxaline-3-carboxamide
which when refluxed with concentrated hydrochloric acid gave the known 2-anilinoquinoxaline.
New procedures were worked out for the oxidative cyclisation reactions of quinoxaline-2carboxaldehyde phenylhydrazones to l-phenylflavazoles in excellent yields using azobenzene as a dehydrogenating agent. These cyclisations were also shown to take place, though in low Yield, if the quinoxaline2- carboxaldehyde phenylhydrazones were heated above their melting points in an atmosphere containing oxygen.
Description:
Department of Applied Chemistry, Cochin University of Science and Technology
Valsala Kumari, C K; Dr.Joy, George(Cochin University of Science and Technology, September 20, 1984)
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Abstract:
During the past few decades, a wide spread interest in the structural, optical, electrical and
other physical properties of the transition metal dichalcogenide layer compounds has evolved. The members of this family of compounds can be regarded as strongly bonded two dimensional chalcogen-metal~chalcogen layers which are loosely coupled to one another by the weak ven
der Waal's forces. Because of this type of bonding, the crystals are easily cleavable along the basal plane and show highly anisotropic properties. This thesis contains the growth and the study
of the physical properties of certain tin dichalcogenide crystals (SnS2 and SnSe2). Tin disulphide and tin diselenide crystallize in the hexagonal CdI2 type crystal structure. This structure consists of layers of tin atoms sandwiched between two layers of chalcogen atoms. A tin atom is surrounded by six chalcogen atoms octahedrally.In the layers the atoms are held together by
covalent bonding and in between the layers there is van der Waal's bonding.
Description:
Department of Physics, Cochin University of Science and Technology
Jacob,K Daniel; Dr.Krishnamoorthy,A(Cochin University Of Science And Technology, 1985)
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Abstract:
In this thesis we study the effect of rest periods
in queueing systems without exhaustive service and inventory
systems with rest to the server. Most of the works in the
vacation models deal with exhaustive service. Recently
some results have appeared for the systems without exhaustive
service.
Description:
Department Of‘ Mathematics And Statistics,Cochin University Of Science And Technology
Ramachandran,P T; Dr.Thrivikraman, T(Cochin University of Science and Technology, 1985)
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Abstract:
In this thesis we investigate some problems in set theoretical topology related to the concepts of
the group of homeomorphisms and order. Many problems considered are directly or indirectly related to the concept of the group of homeomorphisms of a topological space onto itself. Order theoretic methods are used extensively. Chapter-l deals with the group of homeomorphisms.
This concept has been investigated by several authors for many years from different angles. It was observed that nonhomeomorphic topological spaces can have isomorphic groups of homeomorphisms. Many problems relating the topological properties of a space and the algebraic properties of its group of homeomorphisms were investigated. The group of isomorphisms of several algebraic, geometric, order theoretic and topological structures had also been investigated. A related concept of the semigroup of continuous functions of a topological space also received attention
Description:
Department of Mathematics and Statistics, Cochin University of Science and Technology
Jessy,John C; Dr.Pillai, R N(Cochin University of Science And Technology, 1985)
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Abstract:
This study is concerned with Autoregressive Moving Average (ARMA) models of time series. ARMA models form a subclass of the class of general linear models which represents stationary time series, a phenomenon encountered most often in practice by engineers, scientists and economists. It is always desirable to employ models which use parameters parsimoniously. Parsimony will be achieved by ARMA models because it has only finite number of parameters. Even though the discussion is primarily concerned with stationary time series, later we will take
up the case of homogeneous non stationary time series which can be transformed to stationary time series. Time series models, obtained with the help of the present and past data is used for forecasting future values. Physical science as well as social science take benefits of forecasting models. The role of forecasting cuts across all fields of management-—finance, marketing, production, business economics, as also in signal process, communication engineering, chemical processes, electronics etc. This high applicability of time series is the motivation to this study.
Description:
Department of mathematics, Cochin University of Science And Technology
Thresiamma,T K; Dr.Wazir, Hasan Abdi(Cochin University of Science and Technology, 1985)
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Abstract:
The object of this thesis is to formulate a basic commutative difference operator theory for
functions defined on a basic sequence, and a bibasic commutative difference operator theory for functions defined on a bibasic sequence of points, which can be applied to the solution of basic and bibasic difference equations. in this thesis a brief survey of the work done in this field in the classical case, as well as a review of the development of q~difference equations, q—analytic function theory, bibasic analytic function theory, bianalytic function theory, discrete pseudoanalytic function theory and finally a summary of results of this thesis
Description:
Department of Mathematics and
Statistics, Cochin University of Science & Technology
Mohanan, P; Dr.Nair, K G(Cochin University of Science And Technology, March , 1985)
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Abstract:
The flange technique, suggested by Reynolds72
is simple technique to improve antenna characteristics.
Using flange technique we can trim the antenna
characteristic by suitably adjusting the flange parameters75.
Later corrugated flanges87 are used for beam shaping. The
important parameters of the corrugated flanges are (a) flange
angle, (b) flange width, (c) flange position, (d) conductivity
of the flange, (e) amplitude excitation of the flange
elements, (f) period of corrugation etc. Compared to a
compound horn the flange technique offers great convenience
in trimming antenna characteristics.
Horns are commonly used as a feed in radar and
satellite communications. A large number of work had been
done to improve the characteristics of horn antennas. It is
an established fact that grooved walls on the inner surface
of a horn can improve the antenna characteristics44.
Corrugated comb surface can be used for the circular
polarization98, tilt of polarization99 etc. This suggests
the possibility to combine these two phenomena and to
obtain a resultant beam. This thesis presents the result
of an investigation to study the possibility of controlling
different antenna characteristics like polarization, beam
shaping, matching etc, using corrugated flange techniques.
Description:
Department of physics, Cochin University of Science And Technology
Pravinkumar,P A; Dr.Nair, K G(Cochin University of Science and Technology, March 18, 1985)
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Abstract:
With the advent of satellite communication and radio astronomy, the need for large and efficient reflector antennas had triggered a widespread investigation in reflector feed design techniques. Major improvements sought are reduction in spill-over, cross polarization losses and the enhancement of aperture efficiency. The search for such a feed culminated in the corrugated horn. The main idea behind the present work is to use the H-plane sectoral horns fitted with,corrugated flanges as feeds of a paraboloid and see how the secondary pattern
of the reflector antenna varies with different parameters of the feed. An offset paraboloid is used as the secondary reflector in order to avoid the adverse effect of aperture ‘blocking by the feed horn structure on the secondary radiation pattern. The measurements were repeated for three
different H-plane sectoral horns with the same set of corrugated flanges at various X-band frequencies. The following parameters of the whole system are studied: (a) Beam shaping. (b) Gain. (c) Variation of VSWR and (d) Cross polarization
Description:
Department of Physics, Cochin University of Science and Technology
Baby,B V; Dr.Babu, Joseph K(Cochin University of Science and Technology, April 3, 1985)
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Abstract:
An immense variety of problems in theoretical physics are of the non-linear type. Non~linear partial differential equations (NPDE) have almost become the rule rather than an exception in diverse branches of physics such as fluid mechanics, field theory, particle physics, statistical physics and optics, and the construction of exact solutions of these equations constitutes
one of the most vigorous activities in theoretical physics today. The thesis entitled ‘Some Non-linear Problems in Theoretical Physics’ addresses various aspects of this problem at the classical level. For obtaining exact solutions we have used mathematical tools like the bilinear
operator method, base equation technique and similarity method with emphasis on its group theoretical aspects. The thesis deals with certain methods of finding exact solutions of a number of non-linear partial differential equations of importance to theoretical physics. Some of these new solutions are of relevance from the applications point of view in diverse branches such as elementary particle physics, field theory, solid state physics and non-linear optics and give some insight into the stable or unstable behavior of dynamical Systems The thesis consists of six chapters.
Description:
Department of Physics, Cochin University of Science and Technology
Radhakrishnan, P; Dr.Sathianandan, K(Cochin University Of Science And Technology, April 30, 1985)
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Abstract:
Laser-induced damage is the principal limiting
constraint in the design and operation of high-power laser
systems used in fusion and other high-energy laser applications.
Therefore, an understanding of the mechanisms
which cause the radiation damage to the components employed
in building a laser and a knowledge of the damage threshold
of these materials are of great importance in designing a
laser system and to operate it without appreciable degradation
in performance. This thesis, even though covers
three distinct problems for investigations using a dye
Q-switched multimode Nd:glass laser operating at 1062 nm
and emitting 25 ns (FWHM) pulses, lays its main thrust on
damage threshold studies on thin films. Using the same glass
laser two-photon excited fluorescence in rhodamine 6G and
generation and characterisation of a carbon plasma have also
been carried out.
Description:
Department of Physics, Cochin University Of Science And Technology