Poly(propylene) (PP) reinforced with short glass fiber was modified with
precipitated nanosilica (pnS) by melt mixing. The weight of the glass fiber was varied
by keeping the pnS at optimum level. The properties of the composites were studied
using universal testing machine, dynamic mechanic analyser (DMA), differential
Scanning calorimetry (DSC) and thermo gravimetric analyser (TGA). The amount of the
glass fiber required for a particular modulus could be reduced by the addition of
nanosilica.
Anjana, R; George, K E(Cochin University of Science And Technology, November , 2014)
[+]
[-]
Abstract:
Upgrading two widely used standard plastics, polypropylene (PP) and high density polyethylene (HDPE), and generating a variety of useful engineering materials based on these blends have been the main objective of this study. Upgradation was effected by using nanomodifiers and/or fibrous modifiers. PP and HDPE were selected for modification due to their attractive inherent properties and wide spectrum of use. Blending is the engineered method of producing new materials with tailor made properties. It has the advantages of both the materials. PP has high tensile and flexural strength and the HDPE acts as an impact modifier in the resultant blend. Hence an optimized blend of PP and HDPE was selected as the matrix material for upgradation. Nanokaolinite clay and E-glass fibre were chosen
for modifying PP/HDPE blend. As the first stage of the work, the mechanical, thermal, morphological, rheological, dynamic mechanical and crystallization characteristics of the polymer nanocomposites prepared with PP/HDPE blend and different surface modified nanokaolinite clay were analyzed. As the second stage of the work, the effect of simultaneous inclusion of nanokaolinite clay (both N100A and N100) and short glass fibres are investigated. The presence of nanofiller has increased the properties of hybrid composites to a greater extent than micro composites. As the last stage, micromechanical modeling of both nano and hybrid
A composite is carried out to analyze the behavior of the composite under load bearing conditions. These theoretical analyses indicate that the polymer-nanoclay interfacial characteristics partially converge to a state of perfect interfacial bonding (Takayanagi model) with an iso-stress (Reuss IROM) response. In the case of hybrid composites the experimental data follows the trend of Halpin-Tsai model. This implies that matrix and filler experience varying amount of strain and interfacial adhesion between filler and matrix and also between the two fillers which play a vital role in determining the modulus of the hybrid composites.A significant observation from this study is that the requirement of higher fibre loading for efficient reinforcement of polymers can be substantially reduced by the presence of nanofiller together with much lower fibre content in the composite. Hybrid composites with both nanokaolinite clay and micron sized E-glass fibre as reinforcements in PP/HDPE matrix will generate a novel class of high performance, cost effective engineering material.
Sinto, Jacob; Dr.George, K E(Cochin University of Science & Technology, May , 2009)
[+]
[-]
Abstract:
The present study was undertaken to prepare nanosilica by a simple cost
effective means and to use it as a potential nanomodifier in thermoplastic matrices and to
develop useful composites. Nanosilica was prepared from sodium silicate and dilute
hydrochloric acid by polymer induced crystallization technique under controlled
conditions. The silica surface was modified by silane coupling agent to decrease the
agglomeration and thus to increase the reinforcement with polymer. The pristine
nanosilica and modified nanosilica were used to make nano-micro hybrid composites.
Short glass fibres and nylon fibres were used as microfillers. The hybrid nanocomposites
based on Polypropylene (PP) and High density poly ethylene (HOPE) are prepared. The
mechanical, thermal, crystallization and dynamic mechanical properties of the composites
are evaluated.
Description:
Dept. of Polymer Science and Rubber Technology,
Cochin University of Science and technology
Sasi Kumar, P R; Nampoori, V P N; Vallabhan, C P G(Springer, May , 1994)
[+]
[-]
Abstract:
The changes in emission characteristics of a neon hollow cathode discharge by resonant laser excitation of 1s 5→2p 2 and 1s 5→2p 4 transition have been studied by simultaneously monitoring the optogalvanic effect and the laser induced fluorescence. It has been observed that resonant excitation causes substantial variation in the relative intensities of lines in the emission spectrum of neon discharge.
Unsaturated polyester resins (UPRs) are extensively
used by the fiber-reinforced plastic (FRPs) industry.
These resins have the disadvantages of brittleness and
poor resistance to crack propagation. In this study, UPRs
were chemically modified by reactive blending with polyurethane
prepolymers having terminal isocyanate groups.
Hybrid networks were formed by copolymerisation of unsaturated
polyesters with styrene and simultaneous reaction
between terminal hydroxyl groups of unsaturated polyester
and isocyanate groups of polyurethane prepolymer. The
prepolymers were based on toluene diisocyanate (TDI) and
each of hydroxy-terminated natural rubber (HTNR), hydroxy-
terminated polybutadiene (HTPB), polyethylene glycol
(PEG), and castor oil. Properties like tensile strength,
toughness, impact resistance, and elongation-at-break of the
modified UPRs show considerable improvement by this
modification. The thermal stability of the copolymer is also
marginally better
Description:
Journal of Applied Polymer Science, Vol. 100, 449–456 (2006)
Pravinkumar,P A; Dr.Nair, K G(Cochin University of Science and Technology, March 18, 1985)
[+]
[-]
Abstract:
With the advent of satellite communication and radio astronomy, the need for large and efficient reflector antennas had triggered a widespread investigation in reflector feed design techniques. Major improvements sought are reduction in spill-over, cross polarization losses and the enhancement of aperture efficiency. The search for such a feed culminated in the corrugated horn. The main idea behind the present work is to use the H-plane sectoral horns fitted with,corrugated flanges as feeds of a paraboloid and see how the secondary pattern
of the reflector antenna varies with different parameters of the feed. An offset paraboloid is used as the secondary reflector in order to avoid the adverse effect of aperture ‘blocking by the feed horn structure on the secondary radiation pattern. The measurements were repeated for three
different H-plane sectoral horns with the same set of corrugated flanges at various X-band frequencies. The following parameters of the whole system are studied: (a) Beam shaping. (b) Gain. (c) Variation of VSWR and (d) Cross polarization
Description:
Department of Physics, Cochin University of Science and Technology
Tessamma, Thomas; Dr.Sridhar, C S(Cochin University Of Science And Technology, August 24, 1993)
[+]
[-]
Abstract:
This thesis investigated the potential use of Linear Predictive
Coding in speech communication applications. A Modified Block Adaptive
Predictive Coder is developed, which reduces the computational burden and
complexity without sacrificing the speech quality, as compared to the
conventional adaptive predictive coding (APC) system. For this, changes in
the evaluation methods have been evolved. This method is as different from
the usual APC system in that the difference between the true and the
predicted value is not transmitted. This allows the replacement of the high
order predictor in the transmitter section of a predictive coding system, by
a simple delay unit, which makes the transmitter quite simple. Also, the
block length used in the processing of the speech signal is adjusted
relative to the pitch period of the signal being processed rather than
choosing a constant length as hitherto done by other researchers. The
efficiency of the newly proposed coder has been supported with results of
computer simulation using real speech data.
Three methods for voiced/unvoiced/silent/transition
classification have been presented. The first one is based on energy,
zerocrossing rate and the periodicity of the waveform. The second method
uses normalised correlation coefficient as the main parameter, while the
third method utilizes a pitch-dependent correlation factor. The third
algorithm which gives the minimum error probability has been chosen in a
later chapter to design the modified coder The thesis also presents a comparazive study beh-cm the
autocorrelation and the covariance methods used in the evaluaiicn of the
predictor parameters. It has been proved that the azztocorrelation method is
superior to the covariance method with respect to the filter stabf-it)‘ and
also in an SNR sense, though the increase in gain is only small. The
Modified Block Adaptive Coder applies a switching from pitch precitzion to
spectrum prediction when the speech segment changes from a voiced or
transition region to an unvoiced region. The experiments cont;-:ted in
coding, transmission and simulation, used speech samples from .\£=_‘ajr2_1a:r1
and English phrases. Proposal for a speaker reecgnifion syste: and a
phoneme identification system has also been outlized towards the end of
the thesis.
Description:
Department of Electronics, Cochin University of Science and
Technology
Dey,S; Aanandan,C K; Mohanan, P; K G Nair(Department of Electronics, June , 1993)
[+]
[-]
Abstract:
A circular miqrostrip antenna with a modified structure is
presented. By adjusting the feed location along the circumference
of the patch it is possible to match the antenna with a C
microstrip line of any impedance. The impedance bandwidth
and radiation characteristics are unaffected by this structural
V modification.
The influence of the chemical composition and silylation of mesoporous MCM-41 materials on the photochromic
behaviour of adsorbed spiropyran (BIPS) and 6-nitrospiropyran was studied. Upon incorporation, the spiropyrans
underwent ring opening to form either zwitterionic merocyanine or its corresponding O-protonated form. In all
silica MCM-41 or in the MCM-41 containing aluminium, the O-protonated merocyanine was predominantly
formed. In the case of MCM-41 modified by silylation of the OH groups, a mixture of zwitterionic merocyanine
and spiropyran was present. The photochromic response was studied by means of steady-state irradiation and by
laser flash photolysis. Steady-state irradiation (λ > 450 nm) of the solid samples gives rise in all cases to an intensity
decrease of the absorption bands corresponding to either the protonated or the unprotonated merocyanine form
(reverse photochromism). In contrast, laser flash photolysis at 308 nm of spiropyrans supported on silylated
MCM-41 allows observation of the photochemical ring opening of residual spiropyran to the corresponding
zwitterionic form (normal photochromism).
Afsal, V V; Dr Rosamma Philip(Cochin University of Science and Technology, June 9, 2015)
[+]
[-]
Abstract:
Most living organisms are constantly exposed to potentially harmful pathogens. It is the immune system of the organism that enables it to survive in an environment loaded with dangerous pathogenic microorganisms. The innate immunity provides organisms with a rapid and non-specific first line of defense against pathogens. It includes physical barriers such as skin and mucous membranes and chemical barriers including the high acidity of gastric juice, and specialized soluble molecules that possess antimicrobial activity. One of the well-known innate immune defense mechanisms is the production of antimicrobial substances by specific cells or tissues of the organisms. Antimicrobial peptides (AMPs) are such natural substances that
Naveen Sathyan; Dr. Rosamma Philip(Cochin University of Science and Technology, May 5, 2015)
[+]
[-]
Abstract:
Antimicrobial peptides (AMPs) are gene encoded, small sized, generally cationic, amphiphathic peptides characterized by antimicrobial activity against bacteria, fungi, viruses and other pathogens. They are a major component of the innate immune defense system of almost all living organisms, ranging from bacteria to humans and represent the first line of defense against the invading microbial pathogens (Boman, 1995; Zasloff, 2002). Antimicrobial peptides represent a heterogeneous group displaying multiple modes of action that are determined by the sequence and concentration of peptides. Their remarkable specificity for prokaryotes with low toxicity for eukaryotic cells has favored their investigation and exploitation as new antibiotics
Sreelakshmi, B; Dr.Bright Singh,I S(Cochin University Of Science And Technology, November , 2011)
[+]
[-]
Abstract:
The present study focuses on vibrios especially Vibrio harveyi
isolated from shrimp (P. monodon) larval production systems from both east
and west coasts during times of mortality. A comprehensive approach has
been made to work out their systematics through numerical taxonomy and
group them based on RAPD profiling and to segregate the virulent from
non- virulent isolates based on the presence of virulent genes as well as their
phenotypic expression. The information gathered has helped to develop a
simple scheme of identification based on phenotypic characters and
segregate the virulent from non virulent strains of V. harveyi.
Description:
National Centre for Aquatic Animal Health
Cochin University of Science and
Technology
Toms C, Joseph; Dr.Surendran, P K; Dr. Nirmala, Thampuran(Central Institute of Fisheries Technology, January , 2010)
[+]
[-]
Abstract:
This thesis covers various aspects of viral diseases affecting shrimp aquaculture. The
research component of this thesis can be divided into four areas. The areas covered are: I) A
study to determine the prevalence of WSSV among the crustaceans in the Vembanad estuary, the
shrimp aquaculture farms surrounding the estuary, and the sea off Cochin coast, India using two
, sets of nested PCR primers. 2) An investigation to compare the sequence of six major structural
proteins of WSSV; vp28, vp26, vp 19, vp68, vp281, vp466 from different geographical locations
with that of an isolate from India. 3) Simultaneous occurrence of HPV, IHHNV, MBV and
WSSV in postlarvae of P. monodon from hatcheries in India was monitored by Polymerase
Chain Reaction. 4) A real time PCR procedure was developed for the quantitative analysis of
WSSV infection. The viral load of postlarvae from hatcheries in Kerala meant for aquaculture
was also determined using the quantitative PCR.
Thomas, K T; Dr.Mathew, N M(Cochin University of Science and Technology, April 22, 1997)
[+]
[-]
Abstract:
The forms of natural rubber studied were sheet [RSS 4 and RSS 5], ISNR 20 and EBC. In the case of the latter two forms samples from estate and nonestate sectors were included. The samples were collected from different locations at specified intervals, for a particular period. The effect of the extent of mastication on raw rubber properties as well as the properties of the compounds and vulcanizates also studied. The consistency in raw rubber properties and breakdown behavior of skim rubber were studied by collecting samples periodically from selected processing units. The effect of incorporation of skim with
ISNR 20 has also been investigated
Description:
Rubber Research Institute of India
Rubber Board, Kottayam