Revi Kala, S; Dr. Ramamurthy, V D(Cochin University Of Science And Technology, March 14, 1985)
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Abstract:
The present study was undertaken to observe the phytoplankton (distones,dinoflageliates,and blue green algae) blooms occurring along the south west coast of India at various seasons from February 1982 to august 1984.The centers selected for collection and observation were off Quilon, off Alleppey ,off Calicut. A total number of 25 phytoplankton blooms were studied. Characterisation of phytoplankton blooms include observing the cell counts from the day of its appearance to its day of disappearance. The appearance ,duration and locality of the blooms were also noted
Description:
School Of Marine Sciences
Cochin University Of Science And Technology
Asha Gopalakrishnan; Dr.Unnikrishnan Nair, N(Cochin University Of Science And Technology, May 15, 1995)
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Abstract:
The term reliability of an equipment or device is
often meant to indicate the probability that it carries out
the functions expected of it adequately or without failure
and within specified performance limits at a given age for a
desired mission time when put to use under the designated
application and operating environmental stress. A broad
classification of the approaches employed in relation to
reliability studies can be made as probabilistic and
deterministic, where the main interest in the former is to
device tools and methods to identify the random mechanism
governing the failure process through a proper statistical
frame work, while the latter addresses the question of
finding the causes of failure and steps to reduce individual
failures thereby enhancing reliability. In the
probabilistic attitude to which the present study subscribes to, the concept of life distribution, a mathematical
idealisation that describes the failure times, is
fundamental and a basic question a reliability analyst has
to settle is the form of the life distribution. It is for
no other reason that a major share of the literature on the
mathematical theory of reliability is focussed on methods of
arriving at reasonable models of failure times and in
showing the failure patterns that induce such models. The
application of the methodology of life time distributions is
not confined to the assesment of endurance of equipments and
systems only, but ranges over a wide variety of scientific
investigations where the word life time may not refer to the
length of life in the literal sense, but can be concieved in
its most general form as a non-negative random variable.
Thus the tools developed in connection with modelling life
time data have found applications in other areas of research
such as actuarial science, engineering, biomedical sciences,
economics, extreme value theory etc.
Description:
Division of Statistics, School of Mathematical Sciences,
Cochin University of Science and Technology
Muraleedharan Nair,K R; Dr.Unnikrishnan Nair, N(Cochin University Of Science And Technology, May 10, 1990)
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Abstract:
It is highly desirable that any multivariate
distribution possessescharacteristic properties that
are generalisation in some sense of the corresponding
results in the univariate case. Therefore it is of
interest to examine whether a multivariate distribution
can admit such characterizations. In the exponential
context, the question to be answered is, in what meaning—
ful way can one extend the unique properties in the
univariate case in a bivariate set up? Since the lack
of memory property is the best studied and most useful
property of the exponential law, our first endeavour
in the present thesis, is to suitably extend this
property and its equivalent forms so as to characterize
the Gumbel's bivariate exponential distribution.
Though there are many forms of bivariate exponential
distributions, a matching interest has not been shown
in developing corresponding discrete versions in the
form of bivariate geometric distributions. Accordingly,
attempt is also made to introduce the geometric version
of the Gumbel distribution and examine several of its
characteristic properties. A major area where exponential
models are successfully applied being reliability
theory, we also look into the role of these bivariate
laws in that context.
The present thesis is organised into five
Chapters
Description:
Department of Mathematics
and Statistics, Cochin University of Science
and Technology
This thesis entitled Reliability Modelling and Analysis in Discrete time Some Concepts and Models Useful in the Analysis of discrete life time data.The present study consists of five chapters. In Chapter II we take up the derivation of some general results useful in reliability modelling that involves two component mixtures. Expression for the failure rate, mean residual life and second moment of residual life of the mixture distributions in terms of the corresponding quantities in the component distributions are investigated. Some applications of these results are also pointed out. The role of the geometric,Waring and negative hypergeometric distributions as models of life lengths in the discrete time domain has been discussed already. While describing various reliability characteristics, it was found that they can be often considered as a class. The applicability of these models in single populations naturally extends to the case of populations composed of sub-populations making mixtures of these distributions worth investigating. Accordingly the general properties, various reliability characteristics and characterizations of these models are discussed in chapter III. Inference of parameters in mixture distribution is usually a difficult problem because the mass function of the mixture is a linear function of the component masses that makes manipulation of the likelihood equations, leastsquare function etc and the resulting computations.very difficult. We show that one of our characterizations help in inferring the parameters of the geometric mixture without involving computational hazards. As mentioned in the review of results in the previous sections, partial moments were not studied extensively in literature especially in the case of discrete distributions. Chapters IV and V deal with descending and ascending partial factorial moments. Apart from studying their properties, we prove characterizations of distributions by functional forms of partial moments and establish recurrence relations between successive moments for some well known families. It is further demonstrated that partial moments are equally efficient and convenient compared to many of the conventional tools to resolve practical problems in reliability modelling and analysis. The study concludes by indicating some new problems that surfaced during the course of the present investigation which could be the subject for a future work in this area.
Description:
Department of Statistics, Cochin
University of Science and Technology
Thomas, Joseph; Dr.Jathavedan, M(Cochin University of Science and Technology, June , 1993)
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Abstract:
This thesis contains a study of conservation laws of
fluid mechanics. These conservation laws though classical, have
been put to extensive studies in t:he past many decades
Description:
Department of Mathematics And Statistics, Cochin University of Science And Technology
Sojan Lal,P; Unnikrishnan, A; Poulose Jacob,K(Cochin University of Science and Technology, 2000)
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Abstract:
The thesis introduced the octree and addressed the complete nature of problems encountered, while building and imaging system based on octrees. An efficient Bottom-up recursive algorithm and its iterative counterpart for the raster to octree conversion of CAT scan slices, to improve the speed of generating the octree from the slices, the possibility of utilizing the inherent parallesism in the conversion programme is explored in this thesis. The octree node, which stores the volume information in cube often stores the average density information could lead to “patchy”distribution of density during the image reconstruction. In an attempt to alleviate this problem and explored the possibility of using VQ to represent the imformation contained within a cube. Considering the ease of accommodating the process of compressing the information during the generation of octrees from CAT scan slices, proposed use of wavelet transforms to generate the compressed information in a cube. The modified algorithm for generating octrees from the slices is shown to accommodate the eavelet compression easily. Rendering the stored information in the form of octree is a complex task, necessarily because of the requirement to display the volumetric information. The reys traced from each cube in the octree, sum up the density en-route, accounting for the opacities and transparencies produced due to variations in density.
Sreekumar, R; Thrivikraman,T; Chakravarti, R S(Department of Mathematics, Faculty of Science, 2002)
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Abstract:
The main purpose of the study is to extent concept of the class of spaces called ‘generalized metric spaces’ to fuzzy context and investigates its properties. Any class of spaces defined by a property possessed by all metric spaces could technically be called as a class of ‘generalized metric spaces’. But the term is meant for classes, which are ‘close’ to metrizable spaces in some under certain kinds of mappings. The theory of generalized metric spaces is closely related to ‘metrization theory’. The class of spaces likes Morita’s M- spaces, Borges’s w-spaces, Arhangelskii’s p-spaces, Okuyama’s spaces have major roles in the theory of generalized metric spaces. The thesis introduces fuzzy metrizable spaces, fuzzy submetrizable spaces and proves some characterizations of fuzzy submetrizable spaces, and also the fuzzy generalized metric spaces like fuzzy w-spaces, fuzzy Moore spaces, fuzzy M-spaces, fuzzy k-spaces, fuzzy -spaces study of their properties, prove some equivalent conditions for fuzzy p-spaces. The concept of a network is one of the most useful tools in the theory of generalized metric spaces. The -spaces is a class of generalized metric spaces having a network.
Noble,A; Dr.Silas, E G(Cochin University of Science and Technology, February , 1986)
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Abstract:
Mackerel fishery at many places in the country including Cochin
as well as at all—India level, besides its seasonal changes to
have long-term flucations apparently evincing a ten-year cycle.
Published literature on the fishery and biology of mackerel at
many places are available. But attempts on population studies
and assessment of stock are scanty. The researchers attention
at this juncture turned to investigations on population dynamics
of the mackerel .On account of the long-term Fluctuations
in the fishery, it was felt desirable to have data For a
number of years together to facilitate adequate coverage of a
unit of time in the 10-year cycle. Investigations on length weight
relationships for 16 seasons were hence carried out.
This thesis is written eection'by section embodying‘ the
results and_findings of the work carried out under different
subject areas. It contains sections on identity of the species,
information on its spatial and temporal distribution along the
Indian coast, study on length-weight relationships, growth and
age determination, population studies and stock assessment, and
discussions.This dissertation is the outcome of the works of the
candidate on the Indian mackerel. The work, however is based
on exploited resource of the inshore waters. In the course
of this analysis, lacunae existing in the investigations on
the Indian mackerel are therefore identified and presented
For future work