Jaya, V.L; Dr Gopika Kumari(Cochin University of Science and Technology, May 20, 2015)
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Abstract:
Digital Image Processing is a rapidly evolving eld with growing applications
in Science and Engineering. It involves changing the nature
of an image in order to either improve its pictorial information
for human interpretation or render it more suitable for autonomous
machine perception. One of the major areas of image processing
for human vision applications is image enhancement. The principal
goal of image enhancement is to improve visual quality of an image,
typically by taking advantage of the response of human visual
system.
Image enhancement methods are carried out usually in the pixel
domain. Transform domain methods can often provide another way
to interpret and understand image contents. A suitable transform,
thus selected, should have less computational complexity. Sequency
ordered arrangement of unique MRT (Mapped Real Transform)
coe cients can give rise to an integer-to-integer transform, named
Sequency based unique MRT (SMRT), suitable for image processing
applications. The development of the SMRT from UMRT (Unique
MRT), forward & inverse SMRT algorithms and the basis functions
are introduced. A few properties of the SMRT are explored and its
scope in lossless text compression is presented.
Shouri, P V; Dr.Sreejith,P S(Cochin University of Science and Technology, March , 2007)
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Abstract:
In the present scenario of energy demand overtaking energy supply top priority is given
for energy conservation programs and policies. Most of the process plants are operated
on continuous basis and consumes large quantities of energy. Efficient management of
process system can lead to energy savings, improved process efficiency, lesser operating
and maintenance cost, and greater environmental safety. Reliability and maintainability
of the system are usually considered at the design stage and is dependent on the system
configuration. However, with the growing need for energy conservation, most of the
existing process systems are either modified or are in a state of modification with a view
for improving energy efficiency. Often these modifications result in a change in system
configuration there by affecting the system reliability. It is important that system
modifications for improving energy efficiency should not be at the cost of reliability. Any
new proposal for improving the energy efficiency of the process or equipments should
prove itself to be economically feasible for gaining acceptance for implementation. In
order to arrive at the economic feasibility of the new proposal, the general trend is to
compare the benefits that can be derived over the lifetime as well as the operating and
maintenance costs with the investment to be made. Quite often it happens that the
reliability aspects (or loss due to unavailability) are not taken into consideration. Plant
availability is a critical factor for the economic performance evaluation of any process
plant.The focus of the present work is to study the effect of system modification for improving
energy efficiency on system reliability. A generalized model for the valuation of process
system incorporating reliability is developed, which is used as a tool for the analysis. It
can provide an awareness of the potential performance improvements of the process
system and can be used to arrive at the change in process system value resulting from
system modification. The model also arrives at the pay back of the modified system by
taking reliability aspects also into consideration. It is also used to study the effect of
various operating parameters on system value. The concept of breakeven availability is
introduced and an algorithm for allocation of component reliabilities of the modified
process system based on the breakeven system availability is also developed. The model
was applied to various industrial situations.
Description:
Division of Mechanical Engineering,Cochin University of Science and
Technology
Jiji, K S; Jayadas, N H; Babu, C A(Cochin University Of Science And Technology, May , 2015)
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Abstract:
Salient pole brushless alternators coupled to IC engines are
extensively used as stand-by power supply units for meeting in-
dustrial power demands. Design of such generators demands high
power to weight ratio, high e ciency and low cost per KVA out-
put. Moreover, the performance characteristics of such machines
like voltage regulation and short circuit ratio (SCR) are critical
when these machines are put into parallel operation and alterna-
tors for critical applications like defence and aerospace demand
very low harmonic content in the output voltage. While designing
such alternators, accurate prediction of machine characteristics,
including total harmonic distortion (THD) is essential to mini-
mize development cost and time.
Total harmonic distortion in the output voltage of alternators
should be as low as possible especially when powering very sophis-
ticated and critical applications. The output voltage waveform
of a practical AC generator is replica of the space distribution of
the
ux density in the air gap and several factors such as shape
of the rotor pole face, core saturation, slotting and style of coil
disposition make the realization of a sinusoidal air gap
ux wave
impossible. These
ux harmonics introduce undesirable e ects on
the alternator performance like high neutral current due to triplen
harmonics, voltage distortion, noise, vibration, excessive heating
and also extra losses resulting in poor e ciency, which in turn
necessitate de-rating of the machine especially when connected
to non-linear loads. As an important control unit of brushless
alternator, the excitation system and its dynamic performance
has a direct impact on alternator's stability and reliability.
The thesis explores design and implementation of an excitation
i
system utilizing third harmonic
ux in the air gap of brushless al-
ternators, using an additional auxiliary winding, wound for 1=3rd
pole pitch, embedded into the stator slots and electrically iso-
lated from the main winding. In the third harmonic excitation
system, the combined e ect of two auxiliary windings, one with
2=3rd pitch and another third harmonic winding with 1=3rd pitch,
are used to ensure good voltage regulation without an electronic
automatic voltage regulator (AVR) and also reduces the total
harmonic content in the output voltage, cost e ectively.
The design of the third harmonic winding by analytic methods
demands accurate calculation of third harmonic
ux density in
the air gap of the machine. However, precise estimation of the
amplitude of third harmonic
ux in the air gap of a machine by
conventional design procedures is di cult due to complex geome-
try of the machine and non-linear characteristics of the magnetic
materials. As such, prediction of the eld parameters by conven-
tional design methods is unreliable and hence virtual prototyping
of the machine is done to enable accurate design of the third har-
monic excitation system.
In the design and development cycle of electrical machines, it is
recognized that the use of analytical and experimental methods
followed by expensive and in
exible prototyping is time consum-
ing and no longer cost e ective. Due to advancements in com-
putational capabilities over recent years, nite element method
(FEM) based virtual prototyping has become an attractive al-
ternative to well established semi-analytical and empirical design
methods as well as to the still popular trial and error approach
followed by the costly and time consuming prototyping. Hence,
by virtually prototyping the alternator using FEM, the important
performance characteristics of the machine are predicted.
Design of third harmonic excitation system is done with the help
of results obtained from virtual prototype of the machine. Third
harmonic excitation (THE) system is implemented in a 45 KVA
ii
experimental machine and experiments are conducted to validate
the simulation results. Simulation and experimental results show
that by utilizing third harmonic
ux in the air gap of the ma-
chine for excitation purposes during loaded conditions, triplen
harmonic content in the output phase voltage is signi cantly re-
duced. The prototype machine with third harmonic excitation
system designed and developed based on FEM analysis proved
to be economical due to its simplicity and has the added advan-
tage of reduced harmonics in the output phase voltage.
Paulose,M M; Narayanan Nampoothiri,V N; Sreejith,P S(School of Engineering, May , 2006)
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Abstract:
The study aims to the hydrodynamic characteristics of swirling fluidized bed, using large particles (Geldart D-type) selected from locally available agricultural produce (coffee beans and black pepper). The important variables considered in the present study include percentage area of opening, angle of air injection and the percentage useful area of the distributor. A total of seven distributors have been designed and fabricated for a bed column of 300 mm, namely single row vane type distributors (15˚ and 20˚ vane angle), inclined hole type distributors (15˚ and 20˚ vane angle) and perforated plate distributors. The useful area of distributor of single row vane type, three now vane-type and inclined hole-type distributors are respectively 64%,91% and 94%. The hydrodynamic parameters considered in the present study include distributor pressure drop, air velocity, minimum fluidizing velocity, bed pressure drop, bed height and the bed behaviour.
It has been observed that, in general, the distributor pressure drop decreases with an increase in the percentage area of opening, Further, and increase in the area of opening above 17% will not considerably reduce the distributor pressure drop. In the present study, for the distributor with an area of opening 17%, and corresponding to the maximum measured superficial velocity of 4.33 m/s, the distributor pressure drop obtained was 55.25mm of water. The study on the bed behavior revealed that, in a swirling fluidized bed, once swirl motion starts, the bed pressure drop increases with superficial velocity in the outer region and it decreases in the inner region. This means that, with higher superficial velocity, the air might get by-passed through the inner boundary of the bed (around the cone). So, depending on the process for which the bed is used, the maximum superficial velocity is to be limited to have an optimum bed performance.