Deo Prabha, Vasant; Dr.Sridhar, C S(Cochin University of Science and Technology, 1980)
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Abstract:
RMS measuring device is a nonlinear device consisting of linear and
nonlinear devices. The performance of rms measurement is influenced by a number
of factors; i) signal characteristics, 2) the measurement technique used and
3) the device characteristics. RMS measurement is not simple, particularly when
the signals are complex and unknown. The problem of rms measurement on high
crest-factor signals is fully discussed and a solution to this problem is presented
in this thesis.
The problem of rms measurement is systematically analized and found
to have mainly three types of errors: (1) amplitude or waveform error 2) Frequency
error and (3) averaging error. Various rms measurement techniques are studied
and compared. On the basis of this study the rms -measurement is reclassified
three categories: (1) Wave-form-error-free measurement (2) High-frequncy-error
measurement and (3) Low-frequency error-free measurement. In modern digital
sampled-data systems the signals are complex and waveform-error-free rms
measurement is highly appreciated.
Among the three basic blocks of rms measuring device the squarer
is the most important one. A squaring technique is selected, that permits shaping
of the squarer error characteristic in such a way as to achieve waveform-errob
free rms measurement. The squarer is designed, fabricated and tested.
A hybrid rms measurement using an analog rms computing device and
digital display combines the speed of analog techniques and the resolution and
ease of measurement of digital techniques. An A/D converter is modified to perform
the square-rooting operation. A 10-V rms voltmeter using the developed rms detector
is fabricated and tested.
The chapters two, three and four analyse the problems involved in rms
measurement and present a comparative study of rms computing techniques and
devices. The fifth chapter gives the details of the developed rms detector that
permits wave-form-error free rms measurement. The sixth chapter, enumerates the
the highlights of the thesis and suggests a list of future projects
Description:
Department of Electronics, Cochin University of Science and Technology
Saseendran Pillai, P R; Dr.Sreedhar, C S(Cochin University of Science and Technology, December , 1981)
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Abstract:
The thesis presented here includes the designing of underwater transducer arrays, taking into account the ‘interaction effects’ [30] among the closely packed radiators.
Methods of minimizing the ‘interaction effects‘ by modifying the radiating aperture, are investigated. The need for this study arises as it is one of the important peculiar limitations that stands in the way of achieving maximum range of transmission of acoustic signals. Application of the modified array format for the generation of narrow beam low frequency sound waves, through nonlinear interactions, is discussed. Other techniques that can be advantageously
exploited in array synthesis are also investigated
Description:
Department of electronics and communication systems, Cochin University of Science And Technology
Thomas,E V; Dr.Joseph,Francis D(Cochin University of Science And Technology, April , 1985)
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Abstract:
Although the physical and technological properties
of modified rubbers were compared with those of conventional
rubbers in the earlier studies reviewed above, the extent of
energy saving possible by their use has not been quantified.
In the present work it is proposed to determine the energy
saving possible by using the following forms of natural rubber:
1. Oil extended natural rubber, 2. peptised natural rubber,
3. latex stage compounds. The process of production and
quality control of the above types of processed rubbers are
proposed to be standardised. It is also planned to work out
a methodology for utilising field coagula for production of
constant viscosity rubbers. The variation in processing
properties of rubber from popular Indian clones will be examined and those with energy advantages in the processing
stage will be identified. In conclusion a recommendation for
adoption of a commercially advantageous processing procedure
among Indian rubber plantation industry is also given.
Description:
Polymer science & rubber technology, Cochin University of Science And Technology
Devarajan, G; Dr.Sridhar, C S(Cochin University of Science and Technology, January 30, 1987)
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Abstract:
Median filtering is a simple digital non—linear signal
smoothing operation in which median of the samples in a sliding
window replaces the sample at the middle of the window. The
resulting filtered sequence tends to follow polynomial
trends in the original sample sequence. Median filter preserves
signal edges while filtering out impulses. Due to this property,
median filtering is finding applications in many areas of image
and speech processing. Though median filtering is simple to
realise digitally, its properties are not easily analysed with
standard analysis techniques,
Description:
Department of Electronics, Cochin
University of Science and Technology
George,K E; Dr.Joseph,Francis D(Cochin University of Science And Technology, March , 1987)
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Abstract:
The study is undertaken on PVC blends because of their all-round importance-One of the most prominent needs of PVC in application end-use is permanent plasticizationlo. Butadiene-acrylonitrile rubber (NBR) has been utilized as permanent plasticizer for PVC since the 1940s for wire and cable insulation, food contact, and pondliners used for oil containment23'24. Also plasticized PVC has been added to vulcanizable nitrile rubber, to yield improved ozone, thermal ageing, and chemical resistance resulting in applications including fuel hose covers, gaskets, conveyor belt covers, and printing roll covers. This blend is miscible in the range of 23 to 45 per cent acrylonitrile content in the butadiene-acrylqnitrile copolymerzs. The first phase of the study was directed towards modification blends. These blends, in addition to the polymers, require
a host of additives like curatives for the NBR phase and stabilizers for the PVC phase26of the existing PVC blends, especially NBR/PVC. The second phase of the study was directed towards
the development of novel PVC based blends. Chloroprene rubber (polychloroprene) (CR) is structurally similar to PVC and hence is likely to form successful blends with PVC32.
Description:
Department of polymer science
& rubber technology,
Cochin University of Science And Technology
Rani, Joseph; Dr.Joseph,Francis D(Cochin University of Science and Technology, December , 1987)
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Abstract:
There are a large number of commercial examples and property advantages of immiscible elastomer blends.73 Blends of natural rubber (NR) and polybutadiene (BR) have shown various
advantages including heat stability, improved elasticity and abrasion resistance. Ethylene-propylene-diene-rubber (EPDM) blended with styrene-butadiene rubber (SBR) has shown improvements in ozone and chemical resistance with better compression set properties. Blends of EPDM and nitrile rubber (NBR) have been cited as a compromise for obtaining moderate oil and ozone resistance with improved low temperature properties. Neoprene (CR)/BR blends offer improved low temperature properties and abrasion resistance with better processing characteristics etc. However, in many of the commercial two-phase elastomer blends, segregation of the crosslinking agents, carbon black or antioxidants preferentially into one phase
can result in failure to attain optimum properties. Soluble and insoluble compounding ingredients are found to be preferentially concentrated in one phase. The balance of optimum curing of both phases therefore presents a difficult problem. It has been the aim of this study to improve the
performance of commercially important elastomer blends such as natural rubber (NR)/styrene-butadiene rubber (SBR) and natural rubber/polybutadiene rubber (BR) by industrially viable procedures
Description:
Department Of Polymer Science And Rubber technology
Ravindran, T; Dr.Joseph,Francis D(Cochin University of Science And Technology, March , 1989)
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Abstract:
In the present study, the photochemical
depolymerisation of NR in toluene, in presence of
H202 and a homogenizing solvent (Methanol/Tetrahydro—
furan) so as to get hydroxyl terminated liquid natural
rubber (HTNR) has been carried out. The copolymeri—
sation of this product with butane 1,4 diol and toluene
2,4 diisocyanate in presence of a catalyst, dibutyl tin
dilaurate, to produce polyurethanes with HTNR soft segments
is also reported. The preparation of block
copolymers based on poly(ethylene oxide) with varying
molecular weights and HTNR are also discussed along with
a detailed study on their thermal and mechanical properties
Description:
Department of Polymer science and Rubber technology, Cochin University of Science And Technology
Jose,K A; Dr.Nair, K G(Cochin University of Science And Technology, July , 1989)
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Abstract:
The- classic: experiment of Heinrich Hertz verified
the theoretical predict him of Maxwell that kxnfli radio and
light waves are physical phenomena governed by the same
physical laws. This has started a.rnnJ era of interest in
interaction of electromagnetic energy with matter. The
scattering of electromagnetic waves from a target is cleverly
utilized im1 RADAR. This electronic system used tx> detect
and locate objects under unfavourable conditions or obscuration
that would render the unaided eye useless. It also
provides a means for measuring precisely the range, or distance
of an object and the speed of a moving object.
when an obstacle is illuminated by electromagnetic
waves, energy is dispersed in all directions. The dispersed
energy depends on the size, shape and composition of the
obstacle and frequency and nature of the incident wave.
This distribution of energy’ is known as ‘scattering’ and
the obstacle as ‘scatterer’ or 'target'.
Description:
Department of Electronics, Cochin University of Science And Technology
Babu, Jose T; Dr. Punnoose, K K(Cochin University of Science and Technology, November 3, 1989)
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Abstract:
With the increase in population, housing and construction of various facilities have been a problem with urbanization. Having exhausted all the trouble free hand, man is nowon the lookout for techniques to improve areas which were originally considered uninhabitable. Thus this study is based on the nature and engineering behavior of soft clays covering long stretches of coastal line and methods to improve their geotechnical properties .The main aim of the present investigation is to study in detail the physical and engineering behavior of the marine clays of Cochin. While it is well known that the marine clays have been posing numerous problems to foundation engineers all along, the relevant literature reveals that no systematic and comprehensive study has been attempted to date. The: knowledge gained through the study is suitably used to improve these properties with appropriate additives.
Description:
School of Technology,Cochin University of Science and Technology
George, Mathew; Dr.Kuriakose, A P(Cochin University of Science and Technology, December , 1989)
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Abstract:
The thesis entitled Study on Accelerators in Rubber Vulcanization with Special Reference to the Binary Systems Containing Substituted Dithiobiurets. It includes a detailed study on the binary accelerator systems containing substituted dithiobiurets in natural rubber and NR latex and dithiobiurets in SBR and NR-SBR blends vulcanization systems. It deals with the experimental procedure adopted for the preparation of DTB-II and DTB-III; the procedure for compounding and vulcanization and determination of physical properties like modulus, tensile strength, elongation at break, hardness, compression set, heat build up etc. The results indicate that there is efficient acceleration activity of the dithiobiurets in the vulcanization of natural rubber latex containing TMT. The study of dithiobiurets in natural rubber and NR latex reveal that they are having definite accelerating effect in SBR vulcanization systems.
Description:
Department of Polymer Science
and Rubber Technology
Cochin University of Science
and Technology
Antony, T P; Dr.Joseph,Francis D(Cochin University Of Science And Technology, December 4, 1989)
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Abstract:
The main objectives of the investigations
reported in the present thesis are the following: (1)
to find out some industrial wastes as cheaper additives
to augment the air-blowing polymerization process
of bitumen. This will bring down the cost of production
of industrial bitumen which can be applied for the
manufacture of bitumenous paints, roofing and flooring
materials etc. (2) to find out suitable promoters
for the above additives. This will bring down the
consumption of the additives (3) to help in the
industrial pollution control (4) to investigate the
usefulness of the industrial bitumen produced in the
production of bituminous paints (5) to find out thekinetic parameters of the reactions invovled with
different additives. This is essential for the design,
construction and operation of new industrial bitumen
plants using the additives investigated. This will
also enable us to establish the mechanism of the
reactions involved in the process
Description:
Department of Polymer Science and
Rubber Technology, Cochin University of Science and
Technology
Narayanan, N K; Dr.Sridhar, C S(Cochin University of Science and Technology, February 17, 1990)
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Abstract:
This thesis investigates the potential use of
zerocrossing information for speech sample estimation.
It provides 21 new method tn) estimate speech samples using
composite zerocrossings. A simple linear interpolation
technique is developed for this purpose. By using this
method the A/D converter can be avoided in a speech coder.
The newly proposed zerocrossing sampling theory is supported
with results of computer simulations using real speech
data. The thesis also presents two methods for voiced/
unvoiced classification. One of these methods is based
on a distance measure which is a function of short time
zerocrossing rate and short time energy of the signal.
The other one is based on the attractor dimension and entropy
of the signal. Among these two methods the first one is
simple and reguires only very few computations compared
to the other. This method is used imtea later chapter to
design an enhanced Adaptive Transform Coder.
The later part of the thesis addresses a few
problems in Adaptive Transform Coding and presents an
improved ATC. Transform coefficient with maximum amplitude
is considered as ‘side information’. This. enables more
accurate tfiiz assignment enui step—size computation. A new
bit reassignment scheme is also introduced in this work.
Finally, sum ATC which applies switching between luiscrete
Cosine Transform and Discrete Walsh-Hadamard Transform
for voiced and unvoiced speech segments respectively is
presented. Simulation results are provided to show the
improved performance of the coder
Description:
Department of Electronics, Cochin University
of Science and Technology