Chandran,A R; Gopikrishna, M; Aanandan,C K; Mohanan, P; Vasudevan, K(IEEE, September 28, 2006)
[+]
[-]
Abstract:
Effective use of fractal-based metallo-dielectric structures for enhancing the radar cross-section (RCS) of dihedral corner reflectors is reported. RCS enhancement of about 30 dBsm is obtained for corner reflectors with corner angles other than 90deg. This may find application in remote sensing and synthetic aperture radar.
Nisha Nandakumar; Dr. Philip Kurian(Cochin University of Science and Technology, December 3, 2013)
[+]
[-]
Abstract:
The Human race of our century is in gluttonous search for novel engineering
products which led to a skyrocketed progress in research and fabrication of filled
polymers. Recently, a big window has been opened up for speciality polymers
especially elastomers with promising properties. Among the many reasons why
rubbers are widely used in the process industries, three are considered as
important. Firstly, rubbers operate in a variety of environments and possess usable
ranges of deformity and durability and can be exploited through suitable and more
or less conventional equipment design principles. Secondly, rubber is an eminently
suitable construction material for protection against corrosion in the chemical plant
and equipment against various corrosive chemicals as, acids and alkalies and if
property tailored, can shield ionising radiations as X-rays and gamma rays in
medical industry, with minimum maintenance lower down time, negligible
corrosion and a preferred choice for aggressive corroding and ionising
environment. Thirdly, rubber can readily and hastily, and at a relatively lower cost,
be converted into serviceable products, having intricate shapes and dimensions. In a
century’s gap, large employment of flexible polymer materials in the different
segments of industry has stimulated the development of new materials with special
properties, which paved its way to the synthesis of various nanoscale materials. At
nano scale, one makes an entry into a world where multidisciplinary sciences meet
and utilises the previously unapproached infinitesimal length scale, having
dimension which measure upto one billionth of a meter, to create novel properties.
The nano fillers augment the elastomers properties in an astonishing fashion due to
their multifunctional nature and unprecedented properties have been exhibited by
these polymer-nanocomposites just to beat the shortcomings of traditional micro
composites. The current research aims to investigate the possibility of using
synthesised nano barium sulphate for fabricating elastomer-based nanocomposites
and thereby imparting several properties to the rubber. In this thesis, nano
materials, their synthesis, structure, properties and applications are studied. The
properties of barium sulphate like chemical resistance and radiopacity have been
utilized in the present study and is imparted to the elastomers by preparing
composites.
Nisha, Nandakumar; Dr. Philip, Kurian(Cochin University of Science And Technology, December 11, 2013)
[+]
[-]
Abstract:
The Human race of our century is in gluttonous search for novel engineering
products which led to a skyrocketed progress in research and fabrication of filled
polymers. Recently, a big window has been opened up for speciality polymers
especially elastomers with promising properties. Among the many reasons why
rubbers are widely used in the process industries, three are considered as
important. Firstly, rubbers operate in a variety of environments and possess usable
ranges of deformity and durability and can be exploited through suitable and more
or less conventional equipment design principles. Secondly, rubber is an eminently
suitable construction material for protection against corrosion in the chemical plant
and equipment against various corrosive chemicals as, acids and alkalies and if
property tailored, can shield ionising radiations as X-rays and gamma rays in
medical industry, with minimum maintenance lower down time, negligible
corrosion and a preferred choice for aggressive corroding and ionising
environment. Thirdly, rubber can readily and hastily, and at a relatively lower cost,
be converted into serviceable products, having intricate shapes and dimensions. In a
century’s gap, large employment of flexible polymer materials in the different
segments of industry has stimulated the development of new materials with special
properties, which paved its way to the synthesis of various nanoscale materials. At
nano scale, one makes an entry into a world where multidisciplinary sciences meet
and utilises the previously unapproached infinitesimal length scale, having
dimension which measure upto one billionth of a meter, to create novel properties.
The nano fillers augment the elastomers properties in an astonishing fashion due to
their multifunctional nature and unprecedented properties have been exhibited by
these polymer-nanocomposites just to beat the shortcomings of traditional micro
composites. The current research aims to investigate the possibility of using
synthesised nano barium sulphate for fabricating elastomer-based nanocomposites
and thereby imparting several properties to the rubber. In this thesis, nano
materials, their synthesis, structure, properties and applications are studied. The
properties of barium sulphate like chemical resistance and radiopacity have been
utilized in the present study and is imparted to the elastomers by preparing
composites
Description:
Department of Polymer Science and Rubber Technology
Cochin University of Science and Technology
Nisha, V S; Rani, Joseph(Dept. of Polymer Science and Rubber Technology, May , 2006)
[+]
[-]
Abstract:
The present work is to impart radiopacity in various natural polymers like chitosan, natural rubber and derivatives of chitosan and to characterize it. This thesis collated the radiopaque properties of these radiopaque polymers and various technological applications in the medical field. The applications of radiopaque polymers leads to an exploitation of radiopaque properties like X-ray visibility, optical density, effective atomic number, attenuation coefficient of biopolymers like chitosan, chitosan formate, chitosan acetate, carboxy methyl chitosan and natural rubber. The radiopaqe properties of these materials highly depend upon the size, shape, amount of radiopacifier and crystallinity of the radiopaque material. Radiopaque chitosan microspheres were prepared by cross linking with glutaraldehyde followed by the encapsulation of barium sulpahte. The effect of different emulsion systems on the morphology of chitosan microspheres were studied. The study concentrates radiopaque natural rubber for shielding applications. It reveals that to improve the particle size, morphology and crystalline phase of the zinc oxide particles, a novel method for the preparation of zinc oxide is adopted. A detailed radiopacity study was done in natural rubber containing 100phr precipitated zinc oxide prepared from different zinc salts. One of the significant findings of this investigation is that NR vulcanizates containing precipitated zinc oxide (from zinc acetate) shows higher attenuation coefficient. These interesting findings reveal the applications of these natural radiopaque systems in various fields like surgical tools, medical tubings, catheters, radiation shielding,etc.
A better understanding of the rainfall climatology of the Middle East region identifying the
mechanisms responsible for the rain producing systems is essential for effective utilization of the water
resources over the arid region. A comprehensive analysis on the rainfall climatology of the Middle East region
is carried out to bring out the spatial and temporal variation of rainfall and mechanisms responsible for the
rain events. The study was carried out utilizing rainfall, OLR, wind and humidity data sets procured from
TRMM, NOAA and NCEP-NCAR. Climatology of annual rainfall brings out two areas of alarmingly low rainfall
in the Middle East region: one in Egypt, Jordan and adjoining areas and the other in the southern part of Saudi
Arabia. Daily rainfall analysis indicates that northern region gets rainfall mainly during winter and spring
associated with the passage of Mediterranean low pressure systems whereas rain over the southern region is
caused mainly by the monsoon organized convection, cross equatorial flow and remnants of low pressure
systems associated with the monsoon during the summer season. Thermodynamic structure of the atmosphere
reveals that the region does not have frequent local convection due to insufficient moisture content.
The sinking motion associated with the sub tropic high pressure system and subsidence associated with the
Walker circulation are responsible for maintaining warm and dry air over the region.
Description:
International Journal of Water Resources and Arid Environments 1(3): 180-192, 2011
Junaid, Bushiri M; Nayar, V U(Elsevier, March 15, 2002)
[+]
[-]
Abstract:
Raman and FTIR spectra of [Cu(H2O)6](BrO3)2 and [Al(H2O)6](BrO3)3 · 3H2O are recorded and analyzed. The
observed bands are assigned on the basis of BrO3
− and H2O vibrations. Additional bands obtained in the region of
3 and 1 modes in [Cu(H2O)6](BrO3)2 are due to the lifting of degeneracy of 3 modes, since the BrO3
− ion occupies
a site of lower symmetry. The appearance 1 mode of BrO3
− anion at a lower wavenumber (771 cm−1) is attributed
to the attachment of hydrogen to the BrO3
− anion. The presence of three inequivalent bromate groups in the
[Al(H2O)6](BrO3)3 · 3H2O structure is confirmed. The lifting of degeneracy of 4 mode indicates that the symmetry of
BrO3
− anion is lowered in the above crystal from C3v to C1. The appearance of additional bands in the stretching and
bonding mode regions of water indicates the presence of hydrogen bonds of different strengths in both the crystals.
Temperature dependent Raman spectra of single crystal [Cu(H2O)6](BrO3)2 are recorded in the range 77–523 K for
various temperatures. A small structural rearrangement takes place in BrO3
− ion in the crystal at 391 K. Hydrogen
bounds in the crystal are rearranging themselves leading to the loss of one water molecule at 485 K. This is preceded
by the reorientation of BrO3
− ions causing a phase transition at 447 K. Changes in intensities and wavenumbers of
the bands and the narrowing down of the bands at 77 K are attributed to the settling down of protons into ordered
positions in the crystal
Junaid, Bushiri M; Antony, C J; Abderrahim, Aatiq(Elsevier, February 11, 2008)
[+]
[-]
Abstract:
Raman and FTIR spectra of CaFeTi(PO4)3 and CdFeTi(PO4)3 are recorded and analyzed. The observed bands are assigned in terms
of vibrations of TiO6 octahedra and PO4 tetrahedra. The symmetry of TiO6 octrahedra and PO4 tetrahedra is lowered from their free ion
symmetry. The presence of Fe3+ ion disrupts the Ti–O–P–O–Ti chain and leads to the distortion of TiO6 octrahedra and PO4 tetrahedra.
The PO4 3 tetrahedra in both crystals are linearly distorted. The covalency bonding factor of PO4 3 polyanion of both the crystals are
calculated from the Raman spectra and compared to that of other Nasicon-type systems. The numerical values of covalency bonding
factor indicates that there is a reduction in redox energy and cell voltage and is attributed to strong covalency of PO4 3 polyanionin
Description:
Journal of Physics and Chemistry of Solids 69 (2008) 1985–1989
Junaid, Bushiri M; Jayasree, R S; Fakhfakh, M; Nayar, V U(Elsevier, 2002)
[+]
[-]
Abstract:
Raman and infrared spectra of Tl2NbO2PO4, Tl3NaNb4O9(PO4)2 and TlNbOP2O7 are reported. The observed bands are assigned in
terms of vibrations of NbO6 octahedra and PO4 tetrahedra in the first two compounds and in terms of NbO6 octahedra and P2O7
4−
anion in the third compound. The NbO6 octahedra in all the title compounds are found to be corner-shared and distorted. The higher
wavenumber values of the ν1 (NbO6) mode and other stretching modes indicate that the NbO6 octahedra in them are distorted in the order
TlNbOP2O7 > Tl2NbO2PO4 > Tl3NaNb4O9(PO4)2. The splitting of the ν3 (PO4) mode indicates that PO4 tetrahedra is distorted more
in Tl2NbO2PO4 than in Tl3NaNb4O9(PO4)2. The symmetry of P2O7
4− anion in TlNbOP2O7 is lowered. Bands indicate that the P–O–P
bridge in the above compound has a bent P–O–P bridge configuration
Junaid, Bushiri M; Mahadevan Pillai, V P; Ratheesh, R; Nayar, V U(Elsevier, April 23, 1999)
[+]
[-]
Abstract:
Raman spectra of the KTP single crystal are recorded in electric fields (dc and ac) applied along the polar axis c. Spectra with
the laser beam focused near the cathode end, anode end and the centre of the crystal are recorded. The cathode end of the crystal
develops a spot ‘grey track’ where the laser beam is focused after a lapse of 5 h from the application of a dc electric field of
38 V/cm. The spectra recorded at the cathode end after the application of field show variations in intensity of bands. A new band
appears at 177 cm21. Changes in band intensities are explained on the basis of changes in polarizability of the crystal due to the
movement of K1 ions along the polar axis. K1 ions accumulate at the cathode end, where the ‘Grey track’ formation occurs.
The intensity enhancement observed for almost all bands in the ac field is attributed to the improvement of crystalline quality.
Description:
Journal of Physics and Chemistry of Solids 60 (1999) 1983–1988
Nampoori, V P N; Girijavallabhan, C P; Radhakrishnan, P; Thomas, K J; Sheeba, M(Journal of Optics A: Pure and Applied Optics, March 27, 2008)
[+]
[-]
Abstract:
Polymethyl methacrylate (PMMA) optical fibres are fabricated by a preform drawing process.
The Raman spectra of PMMA fibres are recorded using a diode pumped solid state laser
emitting at 532 nm and a CCD-spectrograph in the 400–3800 cm−1 range. The variation of the
Raman intensity with the length of the optical fibre is studied. Investigations are carried out on
the variation of FWHM of the Raman peak at 2957 cm−1 with the length of the optical fibre and
pump power. The differential scattering cross section and gain coefficient of the Raman peak at
2957 cm−1 in PMMA are calculated in relation to that of toluene
Radhakrishnan, P; Girijavallabhan, C P; Nampoori, V P N; Thomas, K J; Sheeba, M(Journal of Optics A: Pure and Applied Optics, March 27, 2008)
[+]
[-]
Abstract:
Polymethyl methacrylate (PMMA) optical fibres are fabricated by a preform drawing process.
The Raman spectra of PMMA fibres are recorded using a diode pumped solid state laser
emitting at 532 nm and a CCD-spectrograph in the 400–3800 cm−1 range. The variation of the
Raman intensity with the length of the optical fibre is studied. Investigations are carried out on
the variation of FWHM of the Raman peak at 2957 cm−1 with the length of the optical fibre and
pump power. The differential scattering cross section and gain coefficient of the Raman peak at
2957 cm−1 in PMMA are calculated in relation to that of toluene.