Geetha K, Varier; Issac, Riju C; Harilal, S S; Bindhu, C V; Nampoori, V P N; Vallabhan, C P G(Elsevier, 1997)
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Abstract:
The laser produced plasma from the multi-component target YBa2CU3O7 was analyzed using Michelson interferometry and time resolved emission spectroscopy. The interaction of 10 ns pulses of 1.06 mum radiation from a Q-switched Nd:YAG laser at laser power densities ranging from 0.55 GW cm-2 to 1.5 GW cm-2 has been studied. Time resolved spectral measurements of the plasma evolution show distinct features at different points in its temporal history. For a time duration of less than 55 ns after the laser pulse (for a typical laser power density of 0.8 GW cm-2, the emission spectrum is dominated by black-body radiation. During cooling after 55 ns the spectral emission consists mainly of neutral and ionic species. Line averaged electron densities were deduced from interferometric line intensity measurements at various laser power densities. Plasma electron densities are of the order of 1017 cm-3 and the plasma temperature at the core region is about 1 eV. The measurement of plasma emission line intensities of various ions inside the plasma gave evidence of multiphoton ionization of the elements constituting the target at low laser power densities. At higher laser power densities the ionization mechanism is collision dominated. For elements such as nitrogen present outside the target, ionization is due to collisions only.
Gregorios, Mathew; Dr. Jacob, Philip(Cochin University of Science and Technology, December , 1998)
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Abstract:
In this thesis, we present the results of our investigations on the photoconducting
and electrical switching properties of selected chalcogenide glass systems. We have used
XRD and X-ray photoelectron spectroscopy (XPS) analysis for confinuing the amorphous
nature of these materials and for confirming their constituents respectively.Photoconductivity is the enhancement in electrical conductivity of materials
brought about by the motion of charge carriers excited by absorbed radiation. The
phenomenon involves absorption, photogeneration, recombination and transport processes
and it gives good insight into the density of states in the energy gap of solids due to the
presence of impurities and lattice defects. Photoconductivity measurements lead to the
determination of such important parameters as quantum efficiency, photosensiti\'ity,
spectral sensitivity and carrier lifetime. Extensive research work on photoconducting
properties of amorphous semiconductors has resulted in the development of a variety of
very sensitive photodetectors. Photoconductors are finding newer and newer uses eyery
day. CdS, CdSe. Sb2S3, Se, ZnO etc, are typical photoconducting materials which are used
in devices like vidicons, light amplifiers, xerography equipment etc.Electrical switching is another interesting and important property possessed by
several Te based chalcogenides. Switching is the rapid and reversible transition between a
highly resistive OFF state, driven by an external electric field and characterized by a
threshold voltage, and a low resistivity ON state, Switching can be either threshold type
or memory type. The phenomenon of switching could find applications in areas like
infonnation storage, electrical power control etc. Investigations on electrical switching in
chalcogenide glasses help in understanding the mechanism of switching which is
necessary to select and modify materials for specific switching applications.Analysis of XRD pattern gives no further infonuation about amorphous materials
than revealing their disordered structure whereas x-ray photoelectron spectroscopy,XPS)
provides information about the different constituents present in the material. Also it gives binding energies (b.e.) of an element in different compounds and hence b.e. shift from the
elemental form.Our investigations have been concentrated on the bulk glasses, Ge-In-Se, Ge-Bi-Se
and As-Sb-Se for photoconductivity measurements and In-Te for electrical switching. The
photoconducting properties of Ge-Sb-Se thin films prepared by sputtering technique have
also been studied. The bulk glasses for the present investigations are prepared by the melt
quenching technique and are annealed for half an hour at temperatures just below their
respective glass transition temperatures. The dependence of photoconducting propenies on
composition and temperature are investigated in each system. The electrical switching
characteristics of In-Te system are also studied with different compositions and by varying
the temperature.
Description:
Department of Instrumentation,
Cochin University of Science and Technology
Shynu, S V; Vasudevan, K(Cochin University of Science & Technology, October , 2006)
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Abstract:
In this work,we investigate novel designs of compact electronically reconfigurable dual frequency microstrip antennas with a single feed,operating mainly in L-band,without using any matching networks and complicated biasing circuitry.These antennas have been designed to operate in very popular frequency range where a great number of wireless communication applications exist.Efforts were carried out to introduce a successful,low cost reconfigurable dual-frequency microstrip antenna design to the wireless and radio frequency design community.
Description:
Department of Electronics,
Cochin University of Science and Technology
Binoy, G S; Dr. Vasudevan, K(Cochin University of Science & Technology, June , 2002)
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Abstract:
The thesis is the outcome of the experimental and theoretical investigations carried out on a novel slotted microstrip antenna.The antenna excites two resonance frequencies and provides orthogonal polarization. The radiation characteristics of the antenna are studied in detail. The antenna design is optimized using IE3D electromagnetic simulation tool. The frequency-Difference Time-Domain (FDTD) method is employed for the analysis of the antenna.The antenna can be used for personal and satellite communication applications.
Description:
Department of Electronics, Cochin University of Science and Technology.
Ahmed Yasir,Vakayil; Mohan Das,P N; Mohammed Yusuff,K K(Department of Applied Chemistry, 2001)
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Abstract:
Titania is a versatile metal oxide with multiple applications. Titania supported catalysts are reported to be much more active compared to conventional silica or alumina supported ones in some reactions. TiO2 (anatase) having high surface area, with better crystallinity and high onset temperature of rutilation can be prepared by thermal hydrolysis of titanyl sulfate solution under controlled conditions. Calcinations at 350oC for 6 hrs were necessary to crystallize anatase. Method of preparation and percentage of the loaded metal oxides have greater influence on surface area. Drastic decrease in surface area was observed upon rutilation. Rutilation started at different temperatures depending on the metal oxide and the method of preparation. TiO2 should be characterized with high surface area, phase purity and high onset temperature of rutilation.Which should be well above the optimum temperature of a designated reaction in which it is employed as a catalyst. Variation in physical properties, depending upon the method of preparation is greater in TiO2 supported catalysts. Methanation activity was found to be highly dependent on nickel concentration present on the surface of the pellets. The methanation activity is strongly influenced by support material. The rate and turn over frequency of methanation and toluene oxidation activity of these catalysts are also equally important from an industrial point of view.
Nandagopan, O R; Dr. Nandakumar, C G(Cochin University of Science and Technology, November , 2010)
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Abstract:
The study envisaged herein contains the numerical investigations on Perforated Plate
(PP) as well as numerical and experimental investigations on Perforated Plate with Lining
(PPL) which has a variety of applications in underwater engineering especially related to
defence applications. Finite element method has been adopted as the tool for analysis of
PP and PPL. The commercial software ANSYS has been used for static and free
vibration response evaluation, whereas ANSYS LS-DYNA has been used for shock
analysis. SHELL63, SHELL93, SOLID45, SOLSH190, BEAM188 and FLUID30 finite
elements available in the ANSYS library as well as SHELL193 and SOLID194 available
in the ANSYS LS-DYNA library have been made use of. Unit cell of the PP and PPL
which is a miniature of the original plate with 16 perforations have been used. Based
upon the convergence characteristics, the utility of SHELL63 element for the analysis of
PP and PPL, and the required mesh density are brought out. The effect of perforation,
geometry and orientation of perforation, boundary conditions and lining plate are
investigated for various configurations. Stress concentration and deflection factor are
also studied. Based on these investigations, stadium geometry perforation with horizontal
orientation is recommended for further analysis.Linear and nonlinear static analysis of PP and PPL subjected to unit normal pressure has
been carried out besides the free vibration analysis. Shock analysis has also been carried
out on these structural components. The analytical model measures 0.9m x 0.9m with
stiffener of 0.3m interval. The influence of finite element, boundary conditions, and lining plate on linear static response has been estimated and presented. Comparison of
behavior of PP and PPL in the nonlinear strain regime has been made using geometric
nonlinear analysis. Free vibration analysis of the PP and PPL has been carried out ‘in
vacuum’ condition and in water backed condition, and the influence of water backed
condition and effect of perforation on natural frequency have been investigated.Based upon the studies on the vibration characteristics of NPP, PP and PPL in water
backed condition and ‘in vacuum’ condition, the reduction in the natural frequency of the
plate in immersed condition has been rightly brought out. The necessity to introduce the
effect of water medium in the analysis of water backed underwater structure has been
highlighted.Shock analysis of PP and PPL for three explosives viz., PEK, TNT and C4 has been
carried out and deflection and stresses on plate as well as free field pressure have been
estimated using ANSYS LS-DYNA. The effect of perforations and the effect of lining
plate have been predicted. Experimental investigations of the measurement of free field
pressure using PPL have been conducted in a shock tank. Free field pressure has been
measured and has been validated with finite element analysis results. Besides, an
experiment has been carried out on PPL, for the comparison of the static deflection
predicted by finite element analysis.The distribution of the free field pressure and the estimation of differential pressure from
experimentation and the provision for treating the differential pressure as the resistance,
as a part of the design load for PPL, has been brought out.
Description:
Dept. of Ship Technology,
Cochin University of Science and
Technology
Neethu Sundaresan; C K S Pillai(RRL,CUSAT, April , 2006)
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Abstract:
Liquid Crystalline DNA is emerging as an active area of research, due to its potential applications in diverse fields, ranging from nanoelectronics to therapeutics. Since, counter ion neutralization is an essential requirement for the expression of LC DNA, and the present level of understanding on the LC phase behavior of high molecular weight DNA is inadequate, a thorough investigation is required to understand the nature and stability of these phases under the influence of various cationic species. The present study is, therefore mainly focused on a comparative investigation of the effect of metal ions of varying charge, size, hydration and binding modes on the LC phase behavior of high molecular weight DNA. The main objectives of the works are investigations on the induction and stabilization of LC phases of high molecular weight DNA by alkali metal ions, investigations on the induction and stabilization of LC phases of high molecular weight DNA by alkaline earth metal ions, effects of multivalent, transition and heavy metal ions on the LC phase behavior of high molecular weight DNA and investigations on spermine induced LC behavior of high molecular weight DNA in the presence of alkali and alkaline earth metal ions.
The critical DNA concentration (CD) required for the expression of LC phases, phase transitions and their stability varied considerably when the binding site of the metal ions changed from phosphate groups to the nitrogenous bases of DNA, with Li+ giving the highest stability. Multiple LC phases with different textures, sometimes diffused and unstable or otherwise mainly distinct and clear, were observed on mixing metal ions with DNA solutions, which in turn depended on the charge, size, hydration factor, binding modes, concentration of the metal ions and time. Molecular modeling studies on binding of selected metal ions to DNA supported the experimental findings
Prafulla, V; Dr.Lakshmanan, P T(Central Institute of Fisheries Technology, 2002)
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Abstract:
The present study entitled "Investigations on the Distribution Characteristics of Heavy Metals in Squid (Loligo spp.) in Relation to Levels in Food Fishes from the West Coast of India with a Perspective on Seafood Safety"attempts to
establish the base line data on metal levels in squids along the west
coast of India. The study is of great relevance in the present context
when utmost importance is being given for producing wholesome
seafoods especially in the export market with a perspective on seafood
safety.The thesis presents a comprehensive account of the base line
data on important heavy metals, viz., Hg, Cd, Pb, Cu, Zn, Fe, Mn Cr
and Ni in the edible and non-edible body components of the most
abundant Loligo species, viz., L. duvauceli caught along the west
coast of India.
Krishnan Nair, P R; Nandakumaran, V M(Cochin University of Science and Technology, October , 1999)
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Abstract:
This thesis is a study of discrete nonlinear systems represented by one dimensional mappings.As one dimensional interative maps represent Poincarre sections of higher dimensional flows,they offer a convenient means to understand the dynamical evolution of many physical systems.It highlighting the basic ideas of deterministic chaos.Qualitative and quantitative measures for the detection and characterization of chaos in nonlinear systems are discussed.Some simple mathematical models exhibiting chaos are presented.The bifurcation scenario and the possible routes to chaos are explained.It present the results of the numerical computational of the Lyapunov exponents (λ) of one dimensional maps.This thesis focuses on the results obtained by our investigations on combinations maps,scaling behaviour of the Lyapunov characteristic exponents of one dimensional maps and the nature of bifurcations in a discontinous logistic map.It gives a review of the major routes to chaos in dissipative systems,namely, Period-doubling ,Intermittency and Crises.This study gives a theoretical understanding of the route to chaos in discontinous systems.A detailed analysis of the dynamics of a discontinous logistic map is carried out, both analytically and numerically ,to understand the route it follows to chaos.The present analysis deals only with the case of the discontinuity parameter applied to the right half of the interval of mapping.A detailed analysis for the n –furcations of various periodicities can be made and a more general theory for the map with discontinuities applied at different positions can be on a similar footing
Nandini Menon, N; Dr. Ravindranatha Menon, N(Cochin University of Science & Technology, April , 1997)
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Abstract:
The thesis deals with different aspects connected with the distribution and toxicity of PHC in crude oils in the aquatic environment and marine molluscs. Information has been gathered and presented on the present status of research in the field based on a thorough review of recent literature. It is seen from the literature that the resident time of PHC becomes lesser and lesser when crude oil is discharged in large quantities into the coastal waters where excess oxygenation light penetration, temperature availability and strong tidal currents persist. This results in the reduction of the onslaught of oil pollution. This probably shows that taxic insult of crude oil in tropical shores will be relatively lesser than that occurring in temperate and boreal waters. However, there is no record of major episodal oil pollution comparable in quantum and extent to that of Torrey Canyon or Amoco Cadiz which prevents a more reliable analysis on the issue. Considerable controversy exists on the method of estimation of PHC in seawater. However, Ultra-violet fluorescence spectroscopy has been widely recommended as an analytical tool for the determination of total hydrocarbons. Similarly representation of values as chrysene equivalents has been recognised as the most reliable method of Quantum representation.
Description:
Division of Marine Biology, Microbiology and Biochemistry, school of Marine Sciences, Cochin University of Science and Technology