Joy, Lija K; Prof. (Dr.) M. R. Anantharaman(July 8, 2016)
[+]
[-]
Abstract:
Thermoelectric materials are revisited for various applications including power generation. The direct conversion of temperature differences into electric voltage and vice versa is known as thermoelectric effect. Possible applications of thermoelectric materials are in eco-friendly refrigeration, electric power generation from waste heat, infrared sensors, temperature controlled-seats and portable picnic coolers. Thermoelectric materials are also extensively researched upon as an alternative to compression based refrigeration. This utilizes the principle of Peltier cooling. The performance characteristic of a thermoelectric material, termed as figure of merit (ZT) is a function of several transport coefficients such as electrical conductivity (σ), thermal conductivity (κ) and Seebeck coefficient of the material (S). ZT is expressed asκσTZTS2=, where T is the temperature in degree absolute. A large value of Seebeck coefficient, high electrical conductivity and low thermal conductivity are necessary to realize a high performance thermoelectric material. The best known thermoelectric materials are phonon-glass electron – crystal (PGEC) system where the phonons are scattered within the unit cell by the rattling structure and electrons are scattered less as in crystals to obtain a high electrical conductivity.
A survey of literature reveals that correlated semiconductors and Kondo insulators containing rare earth or transition metal ions are found to be potential thermoelectric materials. The structural magnetic and charge transport properties in manganese oxides having the general formula of RE1−xAExMnO3 (RE = rare earth, AE= Ca, Sr, Ba) are solely determined by the mixed valence (3+/4+) state of Mn ions. In strongly correlated electron
systems, magnetism and charge transport properties are strongly correlated.
Within the area of strongly correlated electron systems the study of
manganese oxides, widely known as manganites exhibit unique magneto
electric transport properties, is an active area of research.Strongly correlated systems like perovskite manganites,
characterized by their narrow localized band and hoping conduction, were
found to be good candidates for thermoelectric applications. Manganites
represent a highly correlated electron system and exhibit a variety of
phenomena such as charge, orbital and magnetic ordering, colossal magneto
resistance and Jahn-Teller effect. The strong inter-dependence between the
magnetic order parameters and the transport coefficients in manganites has
generated much research interest in the thermoelectric properties of
manganites. Here, large thermal motion or rattling of rare earth atoms with
localized magnetic moments is believed to be responsible for low thermal
conductivity of these compounds. The 4f levels in these compounds, lying
near the Fermi energy, create large density of states at the Fermi level and
hence they are likely to exhibit a fairly large value of Seebeck coefficient.
Hema, V; Dr. Savithri, S(Regional Research Laboratory (CSIR), November , 2003)
[+]
[-]
Abstract:
The current study is aimed at the development of a theoretical
simulation tool based on Discrete Element Method (DEM) to 'interpret granular dynamics
of solid bed in the cross section of the horizontal rotating cylinder at the microscopic
level and subsequently apply this model to establish the transition behaviour, mixing and
segregation.The simulation of the granular motion developed in this work is based on solving
Newton's equation of motion for each particle in the granular bed subjected to the
collisional forces, external forces and boundary forces. At every instant of time, the
forces are tracked and the positions velocities and accelarations of each partcle is The software code for this simulation is written in VISUAL FORTRAN 90 After
checking the validity of the code with special tests, it is used to investigate the transition
behaviour of granular solids motion in the cross section of a rotating cylinder for various
rotational speeds and fill fraction.This work is hence directed towards a theoretical investigation based on Discrete
Element Method (DEM) of the motion of granular solids in the radial direction of the
horizontal cylinder to elucidate the relationship between the operating parameters of the
rotating cylinder geometry and physical properties ofthe granular solid.The operating parameters of the rotating cylinder include the various rotational
velocities of the cylinder and volumetric fill. The physical properties of the granular
solids include particle sizes, densities, stiffness coefficients, and coefficient of friction
Further the work highlights the fundamental basis for the important phenomena of the
system namely; (i) the different modes of solids motion observed in a transverse crosssection
of the rotating cylinder for various rotational speeds, (ii) the radial mixing of the
granular solid in terms of active layer depth (iii) rate coefficient of mixing as well as the
transition behaviour in terms of the bed turnover time and rotational speed and (iv) the
segregation mechanisms resulting from differences in the size and density of particles.The transition behaviour involving its six different modes of motion of the
granular solid bed is quantified in terms of Froude number and the results obtained are
validated with experimental and theoretical results reported in the literature The
transition from slumping to rolling mode is quantified using the bed turnover time and a
linear relationship is established between the bed turn over time and the inverse of the
rotational speed of the cylinder as predicted by Davidson et al. [2000]. The effect of the
rotational speed, fill fraction and coefficient of friction on the dynamic angle of repose
are presented and discussed. The variation of active layer depth with respect to fill
fraction and rotational speed have been investigated. The results obtained through simulation are compared with the experimental results reported by Van Puyvelde et. at.
[2000] and Ding et at. [2002].The theoretical model has been further extended, to study the rmxmg and
segregation in the transverse direction for different particle sizes and their size ratios. The
effect of fill fraction and rotational speed on the transverse mixing behaviour is presented
in the form of a mixing index and mixing kinetics curve. The segregation pattern
obtained by the simulation of the granular solid bed with respect to the rotational speed of
the cylinder is presented both in graphical and numerical forms. The segregation
behaviour of the granular solid bed with respect to particle size, density and volume
fraction of particle size has been investigated. Several important macro parameters
characterising segregation such as mixing index, percolation index and segregation index
have been derived from the simulation tool based on first principles developed in this
work.
Jayaprasad, P N; Dr.Johnson, T P(Cochin University of Science And Technology, January 6, 2014)
[+]
[-]
Abstract:
One can do research in pointfree topology in two ways. The rst is
the contravariant way where research is done in the category Frm but
the ultimate objective is to obtain results in Loc. The other way is the
covariant way to carry out research in the category Loc itself directly.
According to Johnstone [23], \frame theory is lattice theory applied to
topology whereas locale theory is topology itself". The most part of this
thesis is written according to the rst view. In this thesis, we make an
attempt to study about
1. the frame counterparts of maximal compactness, minimal Hausdor -
ness and reversibility,
2. the automorphism groups of a nite frame and its relation with the
subgroups of the permutation group on the generator set of the frame
Description:
Department of Mathematics
Cochin University of Science and Technology
Dhanya., R; Dr. P. Jayamurthy(Cochin University of Science and Technology, February 22, 2016)
[+]
[-]
Abstract:
The incidence of diabetes is rapidly increasing and by 2030 an expected 592 million individuals
are projected to be affected (WHO report). Hyperglycaemic condition is recognized as the causal
link between diabetes and its complications. The chronic hyperglycemia resulting from diabetes
brings about a rise in oxidative stress due to overproduction of reactive oxygen species (ROS) as
a result of glucose auto oxidation and protein glycosylation. Generation of ROS leads to
oxidative damage of the structural components (such as lipids, DNA and proteins) of cells and
potentiate diabetes related complications. Oxidative insult in cells is also created by the
impairment in functioning of endogenous antioxidant enzymes because of their non enzymatic
glycosylation and oxidation. The prolonged exposure of oxidative stress may cause insulin
resistance by triggering an alteration in cellular redox balance. Several lines of evidence suggest
that oxidative stress occurs in diabetes and could have a role in the development of insulin
resistance. The cause and cellular mechanism responsible for this abnormality is not fully
understand despite of intense investigative efforts. However it is unknown whether it is the cause
or consequence of diabetes. Despite strong experimental evidence indicating that oxidative stress
may determine the onset and progression of late-diabetic complications, controversy exists
between the cause and associative relationship between oxidative stress and diabetes mellitus.
Disruption of glucose homeostasis is a characteristic feature of Non-insulin dependent diabetes
mellitus (NIDDM) and is associated with some complications including cardiovascular disease
and renal failure. Glucose transport, the rate limiting step in glucose metabolism, can be activated
in peripheral tissues by two distinct pathways. One stimulated by insulin through IRS-1/PI3K,
Preface
Page 2
the other by muscle contraction/exercise through the activation of AMPK. Both pathways also
increase the phosphorylation and activity of MAPK family components of which p38 MAPK
participates in the full activation of GLUT4.Insulin exerts its biological effect upon binding with the insulin receptor (IR) thereby activating
the downstream signaling that lead to enhanced glucose uptake. In skeletal muscle, it potentiates
glucose transport through PI3K mediated or non-PI3K mediated pathways. Alterations or defects
in its signal transduction pathway was found in diabetic patients associated with decreased levels
of IRb, IRS-1, and PI3K. In the insulin signaling, PI3K is a key molecule and inhibition of PI3K
completely abolish insulin stimulated uptake. Akt or Pkb is an important downstream target of
insulin stimulated glucose transport and metabolism.Impairment in fuel metabolism occurs in obesity, and this impairment is a leading pathogenic
factor in type 2 diabetes. The insulin resistance associated with type 2 diabetes is most profound
at the level of skeletal muscle as this is the primary site of glucose and fatty acid utilization.
Therefore, an understanding of how to activate AMPK in skeletal muscle would offer significant
pharmacologic benefits in the treatment of type 2 diabetes. Metformin and the thiazolidinedione
drugs exert the effects via activation of AMPK. Activation of AMPK occurs in response to
exercise, an activity known to have significant benefit for type 2 diabetics. AMPK serves as
sensor of energy status whose activity is triggered in response to changes in nutritional status in
order to modulate tissue-specific metabolic pathways
Krishna, C; Dr.Chandrasekaran,M(Cochin University of Science and Technology, August , 1995)
[+]
[-]
Abstract:
A critical survey of the fruits and vegetable
markets of the towns and cities in South India reveals that
banana fruit stalk wastes share a dominant proportion among
the solid wastes generated. In the light of the review of
literature presented in the foregoing section, few reports are
available on the utilisation of banana waste for the
production of alcoholic beverages, biogas, and single cell
protein. However, it is not yet tried for the production of
industrial enzymes. Moreover, preliminary fermentation
studies conducted under uncontrolled conditions revealed that
banana fruit stalk could be aptly utilised as solid substrate?
for the industrial production of microbial amylases and
cellulases at a cheaper cost. Therefore, it was proposed to conduct a detailed study towards the development of a suitable fermentation process for the production of industrial enzymes using banana fruit stalk wastes, which is rich in carbohydrate, as solid substrate, employing bacteria, under SSF.
Description:
Department of Biotechnology, Cochin University of
Science & Technology,
Sreedevi, E P; Dr.Sankaran, P G(Cochin University Of Science And Technology, April 9, 2010)
[+]
[-]
Abstract:
there has been much research
on analyzing various forms of competing risks data. Nevertheless, there are several
occasions in survival studies, where the existing models and methodologies are
inadequate for the analysis competing risks data. ldentifiabilty problem and various
types of and censoring induce more complications in the analysis of competing risks
data than in classical survival analysis. Parametric models are not adequate for the
analysis of competing risks data since the assumptions about the underlying lifetime
distributions may not hold well. Motivated by this, in the present study. we develop
some new inference procedures, which are completely distribution free for the
analysis of competing risks data.
Description:
Department of Statistics, Cochin University of Science and
Technology
Hareesh, G; Dr.Balakrishna, N(Cochin University of Science and Technology, August , 2010)
[+]
[-]
Abstract:
The thesis has covered various aspects of modeling and analysis of finite mean time series
with symmetric stable distributed innovations. Time series analysis based on Box and
Jenkins methods are the most popular approaches where the models are linear and errors
are Gaussian. We highlighted the limitations of classical time series analysis tools and
explored some generalized tools and organized the approach parallel to the classical set up.
In the present thesis we mainly studied the estimation and prediction of signal plus noise
model. Here we assumed the signal and noise follow some models with symmetric stable
innovations.We start the thesis with some motivating examples and application areas of alpha stable
time series models. Classical time series analysis and corresponding theories based on finite
variance models are extensively discussed in second chapter. We also surveyed the existing
theories and methods correspond to infinite variance models in the same chapter.
We present a linear filtering method for computing the filter weights assigned to the observation
for estimating unobserved signal under general noisy environment in third chapter.
Here we consider both the signal and the noise as stationary processes with infinite variance
innovations. We derived semi infinite, double infinite and asymmetric signal extraction filters
based on minimum dispersion criteria. Finite length filters based on Kalman-Levy
filters are developed and identified the pattern of the filter weights. Simulation studies show that the proposed methods are competent enough in signal extraction for processes
with infinite variance.Parameter estimation of autoregressive signals observed in a symmetric stable noise
environment is discussed in fourth chapter. Here we used higher order Yule-Walker type
estimation using auto-covariation function and exemplify the methods by simulation and
application to Sea surface temperature data. We increased the number of Yule-Walker
equations and proposed a ordinary least square estimate to the autoregressive parameters.
Singularity problem of the auto-covariation matrix is addressed and derived a modified
version of the Generalized Yule-Walker method using singular value decomposition.In fifth chapter of the thesis we introduced partial covariation function as a tool for stable
time series analysis where covariance or partial covariance is ill defined. Asymptotic results
of the partial auto-covariation is studied and its application in model identification of stable
auto-regressive models are discussed. We generalize the Durbin-Levinson algorithm to
include infinite variance models in terms of partial auto-covariation function and introduce
a new information criteria for consistent order estimation of stable autoregressive model.In chapter six we explore the application of the techniques discussed in the previous
chapter in signal processing. Frequency estimation of sinusoidal signal observed in symmetric
stable noisy environment is discussed in this context. Here we introduced a parametric
spectrum analysis and frequency estimate using power transfer function. Estimate of the
power transfer function is obtained using the modified generalized Yule-Walker approach.
Another important problem in statistical signal processing is to identify the number of
sinusoidal components in an observed signal. We used a modified version of the proposed
information criteria for this purpose.
Description:
Department of Statistics,
Cochin University of Science and Technology