The standard models for statistical signal extraction assume that the signal and noise are
generated by linear Gaussian processes. The optimum filter weights for those models are
derived using the method of minimum mean square error. In the present work we study
the properties of signal extraction models under the assumption that signal/noise are
generated by symmetric stable processes. The optimum filter is obtained by the method of
minimum dispersion. The performance of the new filter is compared with their Gaussian
counterparts by simulation.
Jianlang,Li; Liren,Liu; Yingchun,Guo; Huaisheng,Wang; Changhe,Zhou(Microwave and Optical Technology Letters, December 20, 1999)
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Abstract:
The transient interaction between a refraction index grating
and light beams during simultaneous writing and thermal fixing of
a photorefractive hologram is investigated. With a diffusion- and
photovoltaic-dominated carrier transport mechanism and carrier thermal
activation (temperature dependent) considered in Fe:LiNbO3 crystal, from
the standpoint of field-material coupling, the theoretical thermal fixing
time and the space-charge field buildup, spatial distribution, and temperature
dependence are given numerically by combining the band transport
model with mobile ions with the coupled-wave equation
Narayanan, T; Dr.Chandramohanakumar, N(Cochin University of Science And Technology, June , 2006)
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Abstract:
The thesis entitled “Sterols in Mangrove Sediments of the Cochin
Estuary” is an attempt to characterize the sterol content of the mangrove
sediments, their dietary status with respect to the natural flora and fauna
present, their transfonnations in the sediment and assess contributions, if any to
the nursery character of the mangrove eco system. Samplings were done from
two sites at Mangalavanam and Vypin. Mangalavanam is a patchy mangrove
area in the heart of the city of Cochin and serves as a small bird sanctuary. This
is an almost closed system with a single narrow canal linking to the estuary.
Vypin, the largest single stretch of mangroves in Kerala, is regularly inundated
by a semi diurnal rhythm of Cochin bar mouth. Perhaps, this is the only site in
Kerala where one can see mangroves right along the accreting seacoast.
However a lot of developmental pressure is threatening the very existence of
these mangroves. Post monsoon sediment samples from these areas were used
for the present study, as it is the period of maximum faunal growth and activity
Description:
School of marine sciences, Cochin University of Science And Technology
Bijesh Paul; Dr.Jayadas.N.H(Cochin University of Science and Technology, September 22, 2015)
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Abstract:
In case of novel products with short shelf life, sales data was either
unavailable or scarcely available. The available methods for the estimation of
demand of such products were direct survey methods, collection of opinion or
indirect survey methods, comparison with established products and limited
market trial. From literature review it was concluded that existing literature for
predicting the demand of novel and short life products were scarce. This led to
identification of problem namely demand forecast of relatively novel and short
life products. Initially conventional methods like naive, exponential smoothing
and moving average methods were used to predict the demand. Markov based
model was then applied to forecast errors of the conventional methods. This
model or algorithm requires only demand data of two consecutive months and
hence is suited for demand forecast of novel products.This algorithm was then applied to two novel baked products, one of
relatively large quantity and another of relatively small quantity. Naive,
exponential smoothing and moving average methods were applied to this data
and the forecasts as well as error for all the working days of two consecutive
months were estimated. Markov based algorithm was then applied for these
errors and the steady state probability was determined for each state of
demand. A state of a system is where the system was at a point of time. The
demand corresponding to the state with maximum probability was selected
and the corresponding profit was estimated. The obtained profits were then
compared and the combination with maximum profit was identified and the
method is validated by estimating the annual savings that this method will
bring to the firm when compared to existing methods in case of products A
and BThe suitability of the model was validated by the fact that its
implementation on product A and product B fetched more annual savings
when compared to existing practice. Return on investment increased for
product A and product B when compared to existing methods.
Thus it was concluded that a firm can further enhance its profit by
implementing this model or algorithm for more number of products. Further the
model can be generalized by applying it to more types of novel products with
short shelf life. The forecasting of novel and short life products was not much
explored in previous research works. This model can act as the benchmark for
future researches in forecasting of novel and short life products
Jose, K P; Dr.Krishnamoorthy,A(Cochin University of Science and Technology, December 28, 2006)
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Abstract:
This thesis Entitled Stochastic modelling and analysis.This thesis is divided into six chapters including this introductory chapter. In second chapter, we consider an (s,S) inventory model with service, reneging of customers and finite shortage of items.In the third chapter, we consider an (s,S) inventoiy system with retrial of customers. Arrival of customers forms a Poisson process with rate. When the inventory level depletes to s due to demands, an order for replenishment is placed.In Chapter 4, we analyze and compare three (s,S) inventory systems with positive service time and retrial of customers. In all these systems, arrivals of customers form a Poisson process and service times are exponentially distributed. In chapter 5, we analyze and compare three production inventory systems with positive service time and retrial of customers. In all these systems, arrivals of customers form a Poisson process and service times are exponentially distributed.In chapter 6, we consider a PH /PH /l inventory model with reneging of customers and finite shortage of items.
Description:
Department of Mathematics, Cochin University of Science
and Technology
Lakshmy, B; Dr.Krishnamoorthy,A(Cochin University of Science And Technology, February , 1991)
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Abstract:
This thesis analyses certain problems in Inventories
and Queues. There are many situations in real-life where we
encounter models as described in this thesis. It analyses
in depth various models which can be applied to production,
storag¢, telephone traffic, road traffic, economics, business
administration, serving of customers, operations of particle
counters and others. Certain models described here is not a
complete representation of the true situation in all its
complexity, but a simplified version amenable to analysis.
While discussing the models, we show how a dependence structure can be suitably introduced in some problems of Inventories and Queues. Continuous review, single commodity inventory systems with Markov dependence structure introduced in the demand quantities, replenishment quantities and reordering levels are considered separately. Lead time is assumed to be zero in these models. An inventory model involving random lead
time is also considered (Chapter-4). Further finite capacity
single server queueing systems with single/bulk arrival,
single/bulk services are also discussed. In some models the
server is assumed to go on vacation (Chapters 7 and 8). In
chapters 5 and 6 a sort of dependence is introduced in the
service pattern in some queuing models.
Description:
Department of mathematics & statistics, Cochin University of Science And Technology
Madhusoodanan,T P; Dr.Krishnamoorthy,A(Cochin University of Science And Technology, 1988)
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Abstract:
The objective of this thesis is to study the time dependent behaviour of some complex queueing and inventory models. It contains a detailed analysis of the basic stochastic processes underlying these models. In the theory of queues, analysis of time dependent behaviour is an area.very little developed compared to steady state theory. Tine dependence seems certainly worth studying from an application point of view but unfortunately, the analytic difficulties are considerable.
Glosod form solutions are complicated even for such simple models as M/M /1. Outside M/>M/1, time dependent solutions have been found only in special cases and involve most often double transforms which provide very little insight into the behaviour of the queueing systems themselves. In inventory theory also There is not much results available giving the time
dependent solution of the system size probabilities. Our emphasis is on explicit results free from all types of transforms and the method used may be of special interest to a wide variety of problems having regenerative structure.
Description:
Department of mathematics, Cochin University of Science And Technology
Anantharaman, M R; Narayanan, T N; Sakthi Kumar, D; Yasuhiko, Yoshida(Springer, July 30, 2008)
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Abstract:
Nano magnetic oxides are promising candidates for high density magnetic storage and other applications.
Nonspherical mesoscopic iron oxide particles are also candidate materials for studying the shape, size
and strain induced modifications of various physical properties viz. optical, magnetic and structural. Spherical
and nonspherical iron oxides having an aspect ratio, ~2, are synthesized by employing starch and ethylene glycol
and starch and water, respectively by a novel technique. Their optical, structural, thermal and magnetic
properties are evaluated. A red shift of 0⋅24 eV is observed in the case of nonspherical particles when compared
to spherical ones. The red shift is attributed to strain induced changes in internal pressure inside the
elongated iron oxide particles. Pressure induced effects are due to the increased overlap of wave functions.
Magnetic measurements reveal that particles are superparamagnetic. The marked increase in coercivity in the
case of elongated particles is a clear evidence for shape induced anisotropy. The decreased specific saturation
magnetization of the samples is explained on the basis of weight percentage of starch, a nonmagnetic component
and is verified by TGA and FTIR studies. This technique can be modified for tailoring the aspect ratio and
these particles are promising candidates for drug delivery and contrast enhancement agents in magnetic resonance
imaging
Description:
Bull. Mater. Sci., Vol. 31, No. 5, October 2008, pp. 759–766
Ajith,Joseph K; Dr. Balchand, A N(Cochin University of Science and Technology, December , 1996)
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Abstract:
The dynamics and associated stability analysis of tidal inlets situated on the southwest coast of India, namely Andhakaranazhi (90 45 J OO JJN and 760 17 J 29 JJ E) and the other at
Cochin harbour inlet (90 58 1 04 J1N and 760 14 1 50 1J E) have beenconducted. A detailed study on the inlet regime of Cochin barmouth (permanent in nature) was attempted so as to elucidate information on: (a) channel characteristics (b) tidal hydraulics and (c) stability of the inlet. In this
connection, a naturally occurring seasonal sandbar formation at Andhakaranazhi, near Sherthallay, about 20 km south of Cochin inlet, was also chosen as a site ofstudy brought out conclusively the dynamical study. The aspects of ( 1) tidal influx/out flux (2) channel morphology (3) sedimentation regime and (4) stability and factors related
to stability of these locations. The above aspects are supported by suitable mathematical formulations to describe the associated coastal processes, wherever applicable
Description:
School of marine science, Department of Physical Oceanography, Cochin University of
Science and Technology
Lalaja, V; Nampoori, V P N; Pratap, R(Kluwer Academic Publishers, February , 1989)
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Abstract:
The theory of deterministic chaos is used to study the three rings A, B, and C of Saturn and the French and Cassini divisions in between them. The data set comprises Voyager photopolarimeter measurements. The existence of spatially distributed strange attractors is shown, implying that the system is open, dissipative, nonequilibrium, and non-Markovian in character.
Vinu, Thomas; Dr.Mathew, K T(Cochin University of Science & Technology, September , 2008)
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Abstract:
Electromagnetic tomography has been applied to problems in
nondestructive evolution, ground-penetrating radar, synthetic aperture
radar, target identification, electrical well logging, medical imaging
etc. The problem of electromagnetic tomography involves the
estimation of cross sectional distribution dielectric permittivity,
conductivity etc based on measurement of the scattered fields. The
inverse scattering problem of electromagnetic imaging is highly non
linear and ill posed, and is liable to get trapped in local minima. The
iterative solution techniques employed for computing the inverse
scattering problem of electromagnetic imaging are highly computation
intensive. Thus the solution to electromagnetic imaging problem is
beset with convergence and computational issues. The attempt of this
thesis is to develop methods suitable for improving the convergence
and reduce the total computations for tomographic imaging of two
dimensional dielectric cylinders illuminated by TM polarized waves,
where the scattering problem is defmed using scalar equations. A multi
resolution frequency hopping approach was proposed as opposed to
the conventional frequency hopping approach employed to image large
inhomogeneous scatterers. The strategy was tested on both synthetic
and experimental data and gave results that were better localized and
also accelerated the iterative procedure employed for the imaging. A
Degree of Symmetry formulation was introduced to locate the scatterer
in the investigation domain when the scatterer cross section was
circular. The investigation domain could thus be reduced which
reduced the degrees of freedom of the inverse scattering process. Thus
the entire measured scattered data was available for the optimization of
fewer numbers of pixels. This resulted in better and more robust reconstructions of the scatterer cross sectional profile. The Degree of
Symmetry formulation could also be applied to the practical problem
of limited angle tomography, as in the case of a buried pipeline, where
the ill posedness is much larger. The formulation was also tested
using experimental data generated from an experimental setup that was
designed. The experimental results confirmed the practical
applicability of the formulation.
Description:
Department of Electronics,
Cochin University of Science and Technology
Sathiyamoorthy,V; Dr.Mohan Kumar, K(Department of Atmospheric Sciences, 2001)
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Abstract:
The aim of the present study is to understand the biennial scale stratosphere-troposphere interactions over India, and synoptic to interannual timescale meridional stratosphere-troposhere exchanges caused by upper tropospheric/lower stratospheric longwaves using NCEP/NCAR reanalysis data and satellite measured total ozone data. The biennial timescale interaction between lower stratosphere and troposphere over Thumba is analysed using high-resolution radiosonde data. The results suggest that TBO and QBO are two different phenomena with nearly biennial periodicity. Interannual timescale meridional stratosphere-troposphere exchanges caused by the newly documented Asia Pacific Wave (APW) were analysed using ozone as tracer of atmospheric motion. Synoptic timescale meridional stratosphere-troposhere exchanges caused by subtropical upper tropospheric long waves over Asia were studied using global total ozone measurements from TOMS. This research work can be extended to study the influence of decadal scale epochal nature in Indian summer monsoon activity on the APW generated total ozone anomalies around the globe and the trend estimates in total ozone