Browsing by Author "V.N. Singh"

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A method for the measurement of solar cell series resistance
(1983) V.N. Singh; R.P. Singh
A simple method is suggested for measuring the series resistance of a solar cell which utilises only a single I-V curve at a moderate light intensity level.
Adsorption of phosphate ions on antimony tetroxide by radioactive tracer technique
(1973) I.S. Singh; V.N. Singh; R. Tripathi; B.M. Shukla
[No abstract available]
China clay as an adsorbent for dye house wastewaters
(1992) G.S. Gupta; G. Prasad; V.N. Singh
The ability of china clay to remove a popular chrome dye, Omega Chrome Red ME, from aqueous solutions has been studied. Maximum removal (i.e., 81.08%) was noted at 10 mg l−1 initial dye concentration, 53μm adsorbent particle size, 2.0 pH and 303 K. The process follows a first order rate kinetics. Intraparticle diffusion and mass transfer coefficients have been determined at different temperatures. The adsorption data fits well in the Langmuir adsorption model. The effect of temperature has been examined on the basis of boundary layer thickness and enthalpy change studies. Heat of adsorption has been found to be a function of surface coverage. The maximum removal of the dye in acidic range has been explained on the basis of surface hydroxylation, acid‐base dissociation and surface complexation probabilities. A 100% desorption of the dye from the adsorbent surface was noted at pH 12.0. © 1992 Taylor and Francis Group, LLC.
Equivalent circuit analysis of a system of coupled helical transmission lines in a complex environment
(1983) V.N. Singh; B.N. Basu; B.B. Pal; N.C. Vaidya
The complex boundary value problem of a system of coupled transmission lines which takes into account the effects of the dielectric and metal shell environment is solved by a simple equivalent circuit analysis. The results are compared with those for a simple system of coupled helices in free space now available in the literature. The effects of the various environmental parameters - like the thickness of the dielectric sleeve for the outer helix, the ratio of the outer helix-to-inner helix radii, the ratio of the outer helix-to-inner helix contangents of the pitch angle - are studied on the variation of the optimum length with frequency for a system of helical couplers as used in a traveling-wave tube.
Improved thermal stability and electrochemical behavior of cnts/polyaniline nanocomposite
(2009) Rajesh Kumar Srivastava; Anchal Srivastava; V.N. Singh; B.R. Mehta; Rajiv Prakash
Carbon nanotubes/polymer composite are recently opening new dimension for researchers. We report, the fabrication of nanocomposite of polyaniline (RANI) with functionalized CNTs (f-CNTs) by in-situ chemical polymerization using a novel approach of polymerization of monomers directly over the surface of the CNTs by taking oxidizing agent adsorbed CNTs. In this process of composite formation, CNTs were functionalized with carboxyl group using potassium permanganate (KMnO 4) and sulphuric acid (H 2SO 4) as an oxidizing agent. The deposition of oxidizing agent on the surface of CNTs induces the growth of a uniform layer of PANI on CNTs, which leads the formation of homogeneous nanocomposite of CNTs/PANI. We have studied thermal stability (TGA) and electrochemical behavior of CNTs/PANI nanocomposite. In the nanocomposite, the PANI degradation temperature shifted to higher temperature upto 600 °C. Cyclic Voltammetry of CNTs/PANI composite suggests the catalytic effect of CNTs for fast electron transfer. In this novel synthesis procedure, nanotubes act as a template for the formation of nanocomposite. The formation of f-CNTs coated with oxidizing agent and CNTs/PANI composite were characterized by XRD, SEM and TEM studies. A feasible model for the formation of composite has also been discussed. The processible nanocomposite showed its potential for wide applications. Copyright © 2009 American Scientific Publishers All rights reserved.
INTERACTION IMPEDANCE OF AN INHOMOGENEOUSLY LOADED HELICAL SLOW-WAVE STRUCTURE OF A TWT.
(1985) V.N. Singh; Ved P. Singh; B.N. Basu; R.K. Jha
Pierce's theory for the interaction impedance of a helix in free-space is extended to the case of an inhomogeneously loaded helical structure of a TWT in order to estimate the quality of the latter from the 'grain-frequency' consideration. The characteristic impedance, the impedance parameter and the gain-frequency response of the structure are compared with those of a homogeneously loaded helical structure.
OBSTRUCTION EFFECT OF AGAR GEL IN TRACER DIFFUSION STUDIES OF IONS.
(1985) A.K. Singh; B.K.D. Agrawal; V.N. Singh
The tracer diffusion coefficients of iodide ions in 10** minus **3 M Ca(NO//3)//2 solution immobilized in agar gel of various concentrations (1-5%) at different temperatures (20-35 degree C) were determined by zone diffusion method. There was no appreciable decrease in the value of diffusion coefficient D//g when the concentration of the agar gel increases from 1 to 2. 5%; beyond this concentration range obstruction effect was observed. These investigations also reveal that with an increase in the concentration of agar gel the macromolecules of gel resist the longer elementary jumps and thus the lowering of energy of activation is expected with the increase in gel concentration.
RADIOTRACER STUDIES OF Br** minus IONS ADSORPTION ON (CuO plus SnO//2) GEL.
(1987) K.K. Panday; K.C. Pathak; H.N. Srivastava; V.N. Singh
The adsorption of Br** minus ions on (CuO plus SnO//2) gel has been studied at different concentrations, temperatures, pH and irradiation of adsorbent. The equilibrium data at different temperatures follow Freundlich isotherm. Thermodynamic parameters indicate physical adsorption of Br** minus ions. The extent of adsorption decreases with increase in pH of the solution and irradiation of adsorbent. The desorption of Br** minus ions increases with increase in temperature of the aqueous suspension.
Removal of basic dye (Crystal Violet) from water using wollastonite as absorbent
(1988) S.K. Khare; R.M. Srivastava; K.K. Panday; V.N. Singh
It is shown that wollastonite (calcium metasilicate) can be most efficiently used to treat dyeing effluents at low dye concentrations, high temperatures, alkaline pH and small particle size of adsorbent. Adsorption follows the Langmuir isotherm.
Removal of chrome dye from carpet effluents using coal. I
(1988) G.S. Gupta; G. Prasad; V.N. Singh
A study was made of the removal of Omega Chrome Red ME from carpet effluent by coal for dye concentrations of 5-20 mg per litre, temperatures of 30-50 degrees C and pH 2-12. Lagergren's equation was used to determine kinetics of dye adsorption, and Langmuir's rearranged isotherm model was used to analyse equilibrium data for chrome dye adsorption on to coal. Dye removal was found to be most effective at low adsorbate concentration, low pH and low temperature. Thermodynamic analysis indicated that the process is spontaneous and exothermic.
Removal of chrome dye from carpet effluents using coal. II. Rate processes
(1988) G.S. Gupte; G. Prasad; V.N. Singh
A study is made of the adsorption rate kinetics on coal of Omega Chrome Red ME which is frequently used in carpet production. The effects of initial dye concentration and coal particle size are investigated. A mathematical model is developed for the relationship between dye contact time and its initial and residual concentration. For part I see abstract 1988/5341.
Removal of Victoria Blue from aqueous solution by fly ash
(1987) S.K. Khare; K.K. Panday; R.M. Srivastava; V.N. Singh
In work relating to colour removal from textile effluents, a study has been made of a convenient and economic method for removal of Victoria Blue (C.I. 26,44045) from water by adsorption on fly ash, a low-cost and abundantly available adsorbent.
Some radio tracer studies of thorium oxidesolution interface
(1981) V.N. Singh; S.P. Mishra; H.N. Srivastava
Thorium oxide is one of the most important refractory materials used in ceramic industries. In the present work, the surface properties of this oxide have been studied by allowing the adsorption of bromide ions on its surface at various temperatures (5° to 45°C) and pH (3.2 to 11.5) of KBr solutions using Br-82 as tracer. The influence of neutrons and γ-rays irradiations of this oxide by 300 me (Ra-Be) source for 12, 24, 36 and 48 hours on the adsorption of bromide ions has also been studied. The kinetics of adsorption in all the above cases were found to be of first order. It has been observed that the change in temperature, pH and irradiations with neutron and y-rays of the oxide have remarkable effect on the surface behaviour of the adsorbent. The energy of activation of the process has been determined to understand the mechanism of adherence of ions on the surface of thorium oxide. Attempts have also been made to explain the results obtained in the present investigation in the light of some 'adsorptive properties' of thoria in electrolyte solution. © 1981 Taylor & Francis Group, LLC.
SURFACE PROPERTIES OF ANTIMONY TETROXIDE.
(1984) V.N. Singh; I.S. Singh; U.S. Rai; N.P. Singh
In order to understand the mechanism of the behavior of antimony tetroxide-solution interface, the adsorption of sulfate ions on Sb//2O//4 from aqueous solution of sodium sulfate and their subsequent desorption were followed by radiotracer technique. Both physical and chemical adsorptions occur simultaneously but chemically absorbed ions are predominant.
Treatment of effluents of carpet industry in Bhadohi (Varanasi)
(1988) G.S. Gupta; G. Prasad; V.N. Singh
Treatment of carpet industry effluent (containing mainly Omega Chrome Red ME dye) in Bhadohi (Varanasi) has been carried out by using activated carbon as an adsorbent. It has been found that low concentration, pH and temperature favor the removal of the chrome dye. Kinetics of dye removal indicates that the process is of the first order and mainly diffusion-controlled. The mass transfer of dye at different temperatues from solution-to-solid interface has been explained on the basis of boundary layer and pore diffusion theories. The formation of monolayer coverage of adsorbate on the surface of adsorbent at different temperatures has been confirmed by the applicability of Langmuir's isotherm model. The adsorption of dye decreases from 98.41 to 71.43% with the increase of temperature from 30 to 50°C, showing exothermic nature of the process (ΔH°=-24.43 K cal mole-1). The negative values of standard free energy and entropy change show the spontaneous and random nature of adsorbing molecules.
Trichoderma viride as a mycoparasite of Aspergillus spp.
(Martinus Nijhoff, The Hague/Kluwer Academic Publishers, 1980) Bharat Rai; V.N. Singh; D.B. Singh
Trichoderma viride was found to be parasitic on three species of Aspergillus. The mycoparasitism was characterized by frequent coiling, penetration and hyphal growth of the parasite inside the conidiophores of Aspergillus. The volatile and non-volatile metabolites of T. viride, more or less, inhibited radial growth of all the test Aspergillus spp. © 1980 Martinus Nijhoff Publishers.