Jiby, K. Gopinath; Dr. K. Sreekumar(Cochin University of Science & Technology, July 30, 2015)
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Abstract:
Polymers with conjugated π-electron backbone display unusual
electronic properties such as low energy optical transition, low ionization
potentials, and high electron affinities. The properties that make these
materials attractive include a wide range of electrical conductivity,
mechanical flexibility and thermal stability. Some of the potential
applications of these conjugated polymers are in sensors, solar cells, field
effect transistors, field emission and electrochromic displays, supercapacitors
and energy storage. With recent advances in the stability of
conjugated polymer materials, and improved control of properties, a
growing number of applications are currently being explored. Some of the
important applications of conducting polymers include: they are used in
electrostatic materials, conducting adhesives, shielding against
electromagnetic interference (EMI), artificial nerves, aircraft structures,
diodes, and transistors.
Rosabella,K Puthur; Sebastian, K L; Sugunan, S(Cochin University of Science and Technology, October , 2001)
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Abstract:
The thesis presents the dynamics of a polymer chain under tension. It includes existing theories of polymer fracture, important theories of reaction rates, the rate using multidimensional transition state theory and apply it to the case of polyethylene etc. The main findings of the study are; the life time of the bond is somewhat sensitive to the potential lead to rather different answers, for a given potential a rough estimate of the rate can be obtained by a simples approximation that considers the dynamics of only the bond that breaks and neglects the coupling to neighboring bonds. Dynamics of neighboring bonds would decrease the rate, but usually not more than by one order of magnitude, for the breaking of polyethylene, quantum effects are important only for temperatures below 150K, the lifetime strongly depends on the strain and as the strain varies over a narrow range, the life varies rapidly from 105 seconds to 10_5 seconds, if we change one unit of the polymer by a foreign atom, say by one sulphure atom, in the main chain itself, by a weaker bond, the rate is found to increase by orders of magnitude etc.
Sunandakumari,V M; Dr.Ramanujam, N(Cochin University of Science And Technology, May , 1988)
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Abstract:
During recent years, the theory of differential inequalities has been extensively used to discuss singular perturbation problems and method of lines to partial differential equations. The present thesis deals with some differential inequality theorems and their applications to singularly perturbed initial value problems, boundary value problems for ordinary differential equations
in Banach space and initial boundary value problems for parabolic differential equations. The method of lines to parabolic and elliptic differential equations are also dealt The thesis is organised into nine chapters
Description:
Department of mathematics, Cochin University of Science And Technology
Challa Ravi Kiran; Dr Sundresan, A(Cochin University of Science and Technology, June , 2015)
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Abstract:
Deep fat frying process is one of the widely followed cooking practices throughout the
world. Cooking oils serve as a medium for frying food for transferring heat and makes fried
food tasty and palatable. Frying process is a most complex process involving numerous
physicochemical changes which are complicated to understand. Frying leads to thermal
degradation of oil through thermo-oxidation, hydrolysis, and polymerization. Hydrolysis
results in formation of free fatty acids whereas oxidation process produces hydroperoxides
and small molecular carbonyl compounds. This whole process leads to the formation of polar
compounds and degradation of antioxidants that further degrades frying oil. Eventually,
through mass transfer process these degradation products accumulate into fried food and
reduce the nutritional quality of both oil and food. Thus, the frying process is of research
interest calls for detailed systematic study which is chosen for the present study. The primary
objective of this study is to understand the mechanism of degradation and characterization ofdegraded products which helps in arriving at the limits for frying oil utilization in terms of
number of frying cycles. The mechanistic studies and the knowledge on the degraded
products help to understand the way to retard the deterioration of oil for stability and
enhancement of frying cycles. The study also explores the formation of the predominant
polar compounds and their structural elucidation through mass spectrometry. Oxidation of oil
is another important factor that ignites the degradation phenomena. One of the best ways to
increase thermal stability of any oil is addition of potent antioxidants. But, most of the natural
and synthetic antioxidants are unstable and ineffective at frying temperatures. Therefore, it is
necessary to screen alternative antioxidants for their activity in the refined oils which are devoid of any added antioxidants. In this context, this study discussed the efficacy of several
natural and synthetic antioxidants to retard the formation of polar compounds and thermooxidation
during prolonged frying conditions. Similarly, the advantage of blending of two
different oils to improve the thermal stability was explored. The present study brings out the
total picture on the type of degradation products formed during frying and the ways of
retarding the determination to improve upon the stability of the oil and enhancement of frying
cycles.
Subin, Joseph P; Dr.Jathavedan, M(Cochin University of Science and Technology, January , 2006)
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Abstract:
In this thesis we are studying possible invariants in hydrodynamics and hydromagnetics.
The concept of flux preservation and line preservation of vector fields, especially
vorticity vector fields, have been studied from the very beginning of the study of fluid
mechanics by Helmholtz and others. In ideal magnetohydrodynamic flows the magnetic
fields satisfy the same conservation laws as that of vorticity field in ideal hydrodynamic
flows. Apart from these there are many other fields also in ideal hydrodynamic and magnetohydrodynamic flows which preserves flux across a surface or whose vector lines
are preserved.
A general study using this analogy had not been made for a long time. Moreover
there are other physical quantities which are also invariant under the flow, such as
Ertel invariant. Using the calculus of differential forms Tur and Yanovsky classified
the possible invariants in hydrodynamics. This mathematical abstraction of physical
quantities to topological objects is needed for an elegant and complete analysis of
invariants.Many authors used a four dimensional space-time manifold for analysing fluid flows.
We have also used such a space-time manifold in obtaining invariants in the usual three
dimensional flows.In chapter one we have discussed the invariants related to vorticity field using
vorticity field two form w2 in E4. Corresponding to the invariance of four form w2 ^ w2
we have got the invariance of the quantity E. w. We have shown that in an isentropic
flow this quantity is an invariant over an arbitrary volume.In chapter three we have extended this method to any divergence-free frozen-in
field. In a four dimensional space-time manifold we have defined a closed differential
two form and its potential one from corresponding to such a frozen-in field. Using this
potential one form w1
, it is possible to define the forms dw1 , w1 ^ dw1 and dw1 ^ dw1
.
Corresponding to the invariance of the four form we have got an additional invariant
in the usual hydrodynamic flows, which can not be obtained by considering three
dimensional space.In chapter four we have classified the possible integral invariants associated with
the physical quantities which can be expressed using one form or two form in a three
dimensional flow. After deriving some general results which hold for an arbitrary dimensional
manifold we have illustrated them in the context of flows in three dimensional
Euclidean space JR3. If the Lie derivative of a differential p-form w is not vanishing,then the surface integral of w over all p-surfaces need not be constant of flow. Even
then there exist some special p-surfaces over which the integral is a constant of motion,
if the Lie derivative of w satisfies certain conditions. Such surfaces can be utilised
for investigating the qualitative properties of a flow in the absence of invariance over
all p-surfaces. We have also discussed the conditions for line preservation and surface
preservation of vector fields. We see that the surface preservation need not imply the
line preservation. We have given some examples which illustrate the above results.
The study given in this thesis is a continuation of that started by Vedan et.el. As
mentioned earlier, they have used a four dimensional space-time manifold to obtain
invariants of flow from variational formulation and application of Noether's theorem.
This was from the point of view of hydrodynamic stability studies using Arnold's
method.
The use of a four dimensional manifold has great significance in the study of knots
and links. In the context of hydrodynamics, helicity is a measure of knottedness of
vortex lines. We are interested in the use of differential forms in E4 in the study of
vortex knots and links. The knowledge of surface invariants given in chapter 4 may
also be utilised for the analysis of vortex and magnetic reconnections.
Description:
Department of Mathematics,
Cochin University of Science and Technology
Sethulakshmi, N; Dr. Anantharaman, M. R.(Cochin University of Science and Technology, September , 2014)
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Abstract:
The present thesis work focuses on hole doped lanthanum manganites and their thin film forms. Hole doped lanthanum manganites with higher substitutions of sodium are seldom reported in literature. Such high sodium substituted lanthanum manganites are synthesized and a detailed investigation on their structural and magnetic properties is carried out. Magnetic nature of these materials near room
temperature is investigated explicitly. Magneto caloric application potential of these materials are also investigated. After a thorough investigation of the bulk samples, thin films of the bulk counterparts are also investigated. A magnetoelectric composite with ferroelectric and ferromagnetic components is developed using pulsed laser deposition and the variation in the magnetic and electric properties are investigated. It is established that such a composite could be realized as a potential field effect device. The central theme of this thesis is also on manganites and is with the twin objectives of a material study leading to the demonstration of a device. This is taken up for investigation. Sincere efforts are made to synthesize phase pure compounds. Their structural evaluation, compositional verification and evaluation of ferroelectric and ferromagnetic properties are also taken up. Thus the focus of this investigation is related to the investigation of a magnetoelectric and magnetocaloric application potentials of doped lanthanum manganites with sodium substitution. Bulk samples of sodium substituted lanthanum manganites. Bulk samples of sodium substituted lanthanum manganites with Na substitution ranging from 50 percent to 90 percent were synthesized using a modified citrate gel method and were found to be orthorhombic in structure belonging to a pbnm spacegroup. The variation in lattice parameters and unit cell volume with sodium concentration were also dealt with. Magnetic measurements revealed that magnetization decreased with increase in sodium concentrations.
Rekha,A; Krishnamoorthy,A(Department of Mathematics, Faculty of Science, 2000)
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Abstract:
In this thesis T-policy is implemented to the inventory system with random lead time and also repair in the reliability of k-out-of-n system. Inventory system may be considered as the system of keeping records of the amounts of commodities in stock. Reliability is defined as the ability of an entity to perform a required function under given conditions for a given time interval. It is measured by the probability that an entity E can perform a required function under given conditions for the time interval. In this thesis considered k-out-of-n system with repair and two modes of service under T-policy. In this case first server is available always and second server is activated on elapse of T time units. The lead time is exponentially distributed with parameter and T is exponentially distributed with parameter from the epoch at which it was inactivated after completion of repair of all failed units in the previous cycle, or the moment n-k failed units accumulate. The repaired units are assumed to be as good as new. In this study , three different situations, ie; cold system, warm system and hot system. A k-out-of-n system is called cold, warm or hot according as the functional units do not fail, fail at a lower rate or fail at the same rate when system is shown as that when it is up.