Showing papers by "Cochin University of Science and Technology published in 1989"
United States Geological Survey1, Stanford University2, Geological Survey of Canada3, University of São Paulo4, Massachusetts Institute of Technology5, British Geological Survey6, Karlsruhe Institute of Technology7, Cochin University of Science and Technology8, Russian Academy of Sciences9, Columbia University10, University of Paris-Sud11, University of South Carolina12, Luleå University of Technology13, National Autonomous University of Mexico14, Complutense University of Madrid15
TL;DR: In this article, the authors used regional patterns of present-day tectonic stress to evaluate the forces acting on the lithosphere and to investigate intraplate seismicity, and found that most intraplate regions are characterized by a compressional stress regime; extension is limited almost entirely to thermally uplifted regions.
Abstract: Regional patterns of present-day tectonic stress can be used to evaluate the forces acting on the lithosphere and to investigate intraplate seismicity. Most intraplate regions are characterized by a compressional stress regime; extension is limited almost entirely to thermally uplifted regions. In several plates the maximum horizontal stress is subparallel to the direction of absolute plate motion, suggesting that the forces driving the plates also dominate the stress distribution in the plate interior.
587 citations
TL;DR: Hematocrit and hemoglobin values in the fish Oreochromis mossambicus separately exposed to two different sublethal concentrations of copper and mercury for a period of 168 h are reported.
Abstract: Hematology is used as an index of health status in a number of fish species. Hematological changes have been detected following different types of stress conditions like exposure to pollutants, diseases, hypoxia, etc. Copper and mercury are two known aquatic pollutants. Though copper is an essential micro-nutrient, it is highly toxic at high concentrations. Mercury has no biological function to serve and causes serious impairment in the metabolic and physiological functions of the body. In this paper hematocrit and hemoglobin (Hb) values in the fish Oreochromis mossambicus separately exposed to two different sublethal concentrations of copper and mercury for a period of 168 h are reported.
82 citations
TL;DR: The bioaccumulation and depuration of Hg, Cu, Zn and Pb by the mussel Perna viridis (Linnaeus) from seawater is reported and its suitability as an indicator organism for metal pollution is explored.
Abstract: Bivalves are well known for their ability to concentrate heavy metals in their tissue from environmental water. Experimental studies on the accumulation of these pollutants by molluscs have been extensively conducted. The depuration of accumulated metals in a toxicant free medium has also been studied. Bivalve molluscs may form useful tools in monitoring heavy metal pollution. However, such studies are scant in tropical species. This paper reports the bioaccumulation and depuration of Hg, Cu, Zn and Pb by the mussel Perna viridis (Linnaeus) from seawater and explores its suitability as an indicator organism for metal pollution.
46 citations
TL;DR: In this paper, the dielectric properties of vacuum-deposited europium oxide films have been investigated in the frequency range from 1 kHz to 1 MHz at various temperatures (300-543 K).
41 citations
TL;DR: In this article, an overview of some theoretical results concerning the mean residual life function used in reliability theory is presented, and an extension of the concept to the bivariate case is introduced.
Abstract: An overview is presented of some theoretical results concerning the mean residual life function used in reliability theory. An extension of the concept to the bivariate case is introduced, and the relationship between the reliability and mean residual life function is derived. The properties of the function and conditions for asymptotic exponentiality of component life lengths are discussed. >
25 citations
TL;DR: In this article, the authors investigated the nature of instrumentally recorded seismicity for a part of the Burma-Andaman-Nicobar arc bounded by latitudes 2° and 24°N and longitudes 91° and 99°E.
Abstract: The nature of instrumentally recorded seismicity for a part of the Burma-Andaman-Nicobar arc bounded by latitudes 2° and 24°N and longitudes 91° and 99°E was investigated. Based on the spatial distribution of the earthquakes and their focal mechanism solutions, four tectonic units were identified. From the south going northward, these are the Sumatra trench region, characterized by strike-slip and thrust faulting, the Andaman spreading ridge, characterized by normal and a few strike-slip faults, the Andaman-Nicobar ranges, where faulting is mostly thrust type, and the Indo-Burman ranges region, dominated by thrust faulting. The stress orientations in these segments and their changes with depth were studied in relation to the tectonics of the region. The direction of maximum compression in the Burma-Andaman-Nicobar region is NE-SW to N-S, compatible with the postulated motion of the Indian plate. Changes in stress orientations are attributable to local tectonics.
24 citations
TL;DR: A modified methodology to determine the hydroxylated aromatic compounds in aquatic waters and sediments has been developed in this paper, where interference in seawater samples were overcome by addition of citrate solution permitting the blue colour development on reduction of tungsto• and molybdo• phosphoric acids by the aromatic hydroxlyated groups present in lignins and tannins.
Abstract: A modified methodology to determine the hydroxylated aromatic compounds in aquatic waters and sediments has been developed. Interference in seawater samples were overcome by addition of citrate solution permitting the blue colour development on reduction of tungsto‐ and molybdo‐ phosphoric acids by the aromatic hydroxylated groups present in lignins and tannins. The above procedure was adopted to study the fate of tannin and lignin like substances (TALLS) in tropical estuarine and coastal waters and sediments receiving pulp‐paper effluents.
18 citations
TL;DR: In this paper, the failure rate and mean residual life functions of the parent as well as partial sum distributions, along with the forms of these functions that characterize the above models are also presented.
18 citations
TL;DR: In this paper, a vanadium pentoxide (V 2 O 5 ) was fabricated by the electron beam gun evaporation method and the variation of dielectric constant, ϵ, and loss factor, tan δ, with frequency and temperature were studied in the range 0.5 to 20 KHz and 300 to 423 K, respectively.
Abstract: Amorphous thin films of vanadium pentoxide (V 2 O 5 ) were fabricated by the electron beam gun evaporation method. The variation of dielectric constant, ϵ, and loss factor, tan δ, with frequency and temperature were studied in the range 0.5 to 20 KHz and 300 to 423 K, respectively. Both ϵ and tan δ were found to depend on frequency and temperature. The activation energy calculated (0.41 ± 0.02 eV) for the dielectric relaxation process was found to have good agreement with the activation energy calculated from the temperature dependence of DC conductivity (0.43 ± 0.015 eV). The DC conductivity of these films was remarkably low in comparison with DC conductivities of the films reported earlier, by other methods. The conduction was ascribed to small polaron motion. The application of a higher measuring voltage level at lower frequencies was found to give a negative capacitance and this is associated with a memory switching effect.
16 citations
TL;DR: In this paper, the spatial distribution of isothermals, inversions, lapse conditions, mixing heights and ventilation coefficients over south India is studied for the months of January, April, July and October, which are typical of winter, premonsoon, monsoon and post monsoon seasons, respectively.
Abstract: The potential of the atmosphere to disperse and dilute pollutants emitted into it by myriad sources, depends upon various factors such as wind, vertical mixing, inversion of temperature in the vertical, etc. A study of such parameters is attempted in the present article over south India. The spatial distribution of isothermals, inversions, lapse conditions, mixing heights and ventilation coefficients over south India is studied for the months of January, April, July and October, which are typical of winter, premonsoon, monsoon and post monsoon seasons, respectively. Diurnal variations are also studied.
11 citations
TL;DR: In this paper, the crosslink density and physical properties of the vulcanizates are compared and it is found that for each compound there is an optimum vulcanization temperature which results in the best compromise of properties for specific applications.
Abstract: Compounds of natural rubber, styrene-butadiene rubber, and butadiene rubber are vulcanized at different temperatures and the crosslink density and physical properties of the vulcanizates are compared. It is found that for each compound there is an optimum vulcanization temperature which results in the best compromise of properties for specific applications.
TL;DR: In this paper, photoacoustic (PA) technique is used to study glass transition and temperature dependence of thermal diffusivity in AsxTe1-x glasses with 0.25 0.60 amplitude.
Abstract: Photoacoustic (PA) technique is used to study glass transition and temperature dependence of thermal diffusivity in AsxTe1-x glasses with 0.25 0.60. PA amplitude goes through a minimum and the phase shows a maximum at glass transition temperature Tg. The variation of thermal diffusivity with temperature shows sharp decrease near Tg. The variation of thermal diffusivity with composition shows maximum at = 0.40 for all temperatures T Tg.
26 Jun 1989
TL;DR: In this article, the concept of coupled microstrip line model is extended for the theoretical interpretation of the input impedance of a two-patch gap coupled along the nonradiating edges, and it is concluded that the theory presented here predicts the impedance behavior of a rectangular patch antenna loaded with a parasitic element within tolerable limits.
Abstract: Wideband performance has been obtained from a microstrip patch antenna by using parasitic patches coupled along the nonradiating edges. The concept of the coupled microstrip line model is extended for the theoretical interpretation of the input impedance of a two-patch gap coupled along the nonradiating edges. It is concluded that the theory presented here predicts the impedance behavior of a rectangular patch antenna loaded with a parasitic element within tolerable limits. >
TL;DR: In this paper, a detailed investigation of the thermal-transport properties of bulk glass near their glass-transition temperatures, using the photoacoustic (PA) technique, was carried out.
Abstract: We have carried out a detailed investigation of the thermal-transport properties of bulk ${\mathrm{As}}_{\mathrm{x}}$${\mathrm{Se}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$ glasses near their glass-transition temperatures, using the photoacoustic (PA) technique. Temperature dependence of the thermal diffusivity in several compositions of these glasses in the glass-forming region has been determined by measuring the PA amplitude and phase and their chopping-frequency dependencies. It is found that the PA amplitude has a minimum value and the phase has a maximum value at the glass-transition temperature ${T}_{g}$ in all the compositions. Correspondingly, the thermal diffusivity and conductivity have minimum values at ${T}_{g}$. Also, the temperature dependence of the optical energy gap ${E}_{0}$ in ${\mathrm{As}}_{\mathrm{x}}$${\mathrm{Se}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$ glasses has been determined by use of the PA technique. As expected, ${E}_{0}$ decreases with temperature but with no marked change at ${T}_{g}$, except for an increase in slope for the curves in the region.
TL;DR: In this paper, it was shown that the modulated logistic map comes under the universality class of Feigenbaum and showed that it can generate strange attractors in the unit square for an uncountable number of parameter values in the range μ∞.
TL;DR: In this paper, the vibrational overtone spectra of styrene and polystyrene were studied by the laser-induced thermal lens (for AV = 6) and the conventional near infrared absorption techniques.
Abstract: Vibrational overtone spectra of styrene (liquid) and polystyrene (solid~ studied by the laser-induced thermal lens (for AV = 6) and the conventional near infrared absorption (for AV = 3-5) techniques. are reported. For polystyrene, the overt()ne energy· bond length correlation predicts that the aryl CH bonds are - 0-0005 A longer than that in benzene, while no such conclusions could be drawn on styrene. The sp) CH overtones in polystyrene are observed on the low energy side of the aryl CH overtones.
TL;DR: In this paper, the absorption spectra of formaldehyde molecule in the gas phase have been recorded using photoacoustic (PA) technique with pulsed dye laser at various power levels.
Abstract: Absorption spectra of formaldehyde molecule in the gas phase have been recorded using photoacoustic (PA) technique with pulsed dye laser at various power levels. The spectral profiles at higher power levels are found to be different from that obtained at lower laser powers. Two photon absorption (TPA) is found to be responsible for the photoacoustic signal at higher laser power while the absorption at lower laser power level is attributed to one photon absorption (OPA) process. Probable assignments for the different transitions are given in this paper.
TL;DR: Etude de l'effet du dopage en halogenures et en oxyde sur les spectres d'electroluminescense du ZuS:Pr.
Abstract: Etude de l'effet du dopage en halogenures et en oxyde sur les spectres d'electroluminescense du ZuS:Pr. Developpement de dispositifs electroluminescents a basse tension de seuil et emettant dans le visible, a base de couches minces de ZnS:PrF 3 comme couche active et de Sm 2 O 3 comme isolant
26 Jun 1989
TL;DR: In this article, the authors present the results of the numerical solution to the problem of periodic metallic strips on a dielectric sheet above the ground plane, which is an extension of J. H. Richmond's (IEEE Trans. Antennas Propagat., vol.AP-28, p.883-7, 1980) approach.
Abstract: The authors present the results of the numerical solution to the problem of periodic metallic strips on a dielectric sheet above the ground plane. The present method is an extension of J. H. Richmond's (IEEE Trans. Antennas Propagat., vol.AP-28, p.883-7, 1980) approach. Calculation results agree well with experimental results. The low backscattered surface considered can be used to reduce the radar cross section of metallic objects. >
TL;DR: In this paper, the integrability of the variable coefficient Korteweg-de Vries (KdV) equation u 1 +α t n uu x +β t m u xxx =0 is shown to be exceptional in the two cases m = n and m = 2 n + 1 by showing that they are equivalent to the plane KdV and cylindrical kdV equations respectively.
Abstract: The variable coefficient Korteweg-de Vries (KdV) equation u 1 +α t n uu x +β t m u xxx =0 is shown to be exceptional in the two cases m = n and m = 2 n +1 by showing that they are equivalent to the plane KdV and cylindrical KdV equations respectively. Thus the integrability depends on the two parameters m and n . Here we also consider the numerical solutions of the equation in different cases, viz ., the integrability condition is satisfied and not satisfied. Only when the equation is equivalent to the plane KdV, the profile is seen to be propagating as a stable solitary-wave. In all other cases an oscillatory tail appear on the left of the wave. In the case of interactions of two waves also oscillatory tails appear. The momentum and energy are conserved in all the cases.
TL;DR: In this article, the optical energy gap of bulk SixTe100−x glasses in the glass-forming region 10 ≤ x ≤ 28 was determined using photoacoustic technique and the thermal diffusivity α of these samples has also been measured.
Abstract: The photoacoustic technique is used to determine the optical energy gap E0 of bulk SixTe100−x glasses in the glass-forming region 10 ≤ x ≤ 28. The thermal diffusivity α of these samples has also been measured. The variation of E0 and α with x is reported. It is found that E0 increases with x nearly linearly with a sharp decrease in the rate of increase beyond x = 20. The thermal diffusivity also increases with x up to x = 20 but decreases for compositions with higher values of x. The observed behaviour is explained on the basis of a chemical bond approach. It is accounted for in terms of the increase in the number of Te---Te bonds and formation of SiTe4 tetrahedra with an increase in the chalcogen content.
TL;DR: In this paper, the authors measured the composition dependence of the optical energy gap and thermal diffusivity in bulk As 2Se3 glasses using photoacoustic technique and showed that the decrease in energy gap is explained on the basis of chemical bonding.
Abstract: We have measured the composition dependence of the optical energy gap and thermal diffusivity in bulk As
x
Se1−x
(0.10⩽x⩽0.50) glasses using photoacoustic technique. The energy gap shows a threshold minimum value and thermal diffusivity has a threshold maximum value at the stoichiometric composition As2Se3 corresponding tox=0.40. The decrease in energy gap is explained on the basis of chemical bonding. It is argued that the threshold percolation of rigidity in the random network is responsible for the peaking of the thermal diffusivity at the stoichiometric composition.
TL;DR: In this paper, the Liouville quantum field was analyzed at zero temperature and at finite temperature, and it was shown that there does not exist any translationally invariant ground state for the model and finite temperature corrections do not modify this result.
22 Nov 1989
TL;DR: A speaker independent isolated digit recognition algorithm using a tree structure has been described and an 80% recognition accuracy with trained speakers has been achieved with this algorithm.
Abstract: A speaker independent isolated digit recognition algorithm is described. Decision making using a tree structure has been adopted in this method. Two simple features, energy envelope and zerocrossing rate, have been used for the classification. An 80% recognition accuracy with trained speakers has been achieved with this algorithm. This method implemented on a 386 super PC/AT could respond within 20 sec. >
TL;DR: In this paper, the laser induced plasma emission spectra from high-Tc superconducting samples of YBa2Cu3O7 and GdBa2cu3O 7 obtained with 1.06 µm radiation from a Q switched Nd:YAG laser beam has been analyzed.
Abstract: Laser induced plasma emission spectra from highTc superconducting samples of YBa2Cu3O7 and GdBa2Cu3O7 obtained with 1.06µm radiation from a Q switched Nd:YAG laser beam has been analysed. The results clearly show the presence of diatomic oxides in addition to ionized species of the constituent metals in the plasma thus produced.
TL;DR: In this article, the variation of the thermal diffusivity in the high temperature superconductor YBa2Cu3O7−δ below the transition temperature measured using photo-acoustic technique α is found to increase sharply belowTc.
Abstract: We report the variation of the thermal diffusivity in the high temperature superconductor YBa2Cu3O7−δ below the transition temperature measured using photo-acoustic technique α is found to increase sharply belowTc. Qualitative explanations are given.
TL;DR: In this paper, the photoacoustic (PA) amplitude and phase were measured at the glass transition temperature, where the amplitude has critical minimum and phase has maximum values at T 1 g.
Abstract: The glass transition in Ge
x
Se1−x
) (0·1 ⩽x ⩽ 0·25) glasses has been investigated using the photoacoustic (PA) technique. It is found that the PA amplitude and phase undergo anomalous changes at the glass transition temperatureT
g. The amplitude has critical minimum and phase has maximum values atT
g. The variation of the thermal diffusivity, determined by measuring the frequency dependence of the PA amplitude and phase, with temperature shows sharp decrease near the glass transition temperature. The temperature dependence of the optical energy gap also has been measured and it shows a decrease with temperature for all compositions, the rate of decrease being higher for temperatures greater thanT
g.
22 Nov 1989
TL;DR: A system for the hardware implementation of the FFT (fast Fourier transform) is developed in conjunction with an SDK-86 and can be computed of any number of points provided the system has sufficient memory capacity.
Abstract: A system for the hardware implementation of the FFT (fast Fourier transform) is developed in conjunction with an SDK-86 The FFT of any number of points can be computed provided the system has sufficient memory capacity A scheme for implementing this hardware on a PC is also described >
TL;DR: In this article, a mixture of mixed benzoic-dithiocarbamic anhydride with mercury(II) halides in acetone was used to synthesize halogenodithiamato mercury(III) complexes, which were characterized by chemical analyses, conductance measurements, molecular weight determinations, magnetic susceptibility measurements, and electronic and IR spectral studies.
Abstract: Halogenodithiocarbamato mercury(II) complexes [HgX(Et2NCSS)] and [HgX(PipCSS)] (Pip[dbnd]piperidyl; X[dbnd]C1, Br or I) have been synthesized by the reaction of mixed benzoic-dithiocarbamic anhydride with mercury(II) halides in acetone. The complexes were characterized by chemical analyses, conductance measurements, molecular weight determinations, magnetic susceptibility measurements, and electronic and IR spectral studies. The complexes were dimeric in benzene solution. The IR spectra indicate monodentate bonding for the dithiocarbamate ligand and the absence of halogen bridges in these complexes.