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Showing papers by "Indian Institute of Technology Bombay published in 1979"


Journal ArticleDOI
TL;DR: In this paper, the Liu and Jordan model for predicting daily diffuse radiation from daily total radiation has been tested and found to be applicable for Indian conditions, however the numerical values obtained are very different from those obtained for conditions in the United States.

83 citations


Journal ArticleDOI
TL;DR: The effect of temperature on the potentiodynamic oxidation of adsorbed sulfur layers on platinum, obtained from H 2 S or SO 2 was studied in this paper, where two distinct peaks were observed at 80°C, oxidation peak I (at 0.97 V) corresponding to the weakly bound sulfur and oxidation peak II (at 1.10 V) representing the strongly bound sulfur.

75 citations


Journal ArticleDOI
TL;DR: In this paper, the motion of a semi-infinite incompressible viscous fluid, caused by the oscillation of a plane vertical plate, has been studied, taking into account the presence of free convection currents.
Abstract: The motion of a semi-infinite incompressible viscous fluid, caused by the oscillation of a plane vertical plate, has been studied, taking into account the presence of free convection currents. Closed form solutions to the velocity, temperature and the penetration distance through which the leading edge effect propagates have been derived on neglecting the transient part. Velocity profiles are shown forGr>0 (Grashof number) (cooling of the plate by the free convection currents),Gr<0 (heating of the plate) on graph. Also the penetration distance has been shown on graphs for different values ofP, the Prandtl number. It has been observed that for ωt=3π/2, greater cooling of the plate may cause the flow to become unstable. Also, the penetration distance is not found to be affected by the frequency of the oscillating vertical plate.

69 citations



Journal ArticleDOI
TL;DR: Auhtor et al. as mentioned in this paper presented optimized hole shapes in plates of finite width subjected to uniaxial load for a large range of hole to plate widths (D/W) ratios.
Abstract: : This paper presents optimized hole shapes in plates of finite width subjected to uniaxial load for a large range of hole to plate widths (D/W) ratios. The stress concentration factor for the optimized holes decreased by as much as 44% when compared to circular holes. Simultaneously, the area covered by the optimized hole increased by as much as 26% compared to the circular hole. Coefficients of efficiency between 0.91 and 0.96 are achieved. The geometries of the optimized holes for the D/W ratios considered are presented in a form suitable for use by designers. It is also suggested that the developed geometries may be applicable. to cases of rectangular holes and to the tip of a crack. This information may be of interest in fracture mechanics. (Auhtor)

42 citations


Journal ArticleDOI
TL;DR: In this paper, a series of compounds with composition BaxLa1-xCoO3 (0 ≦ x ≦ 0.5) is synthesized and the electrical resistivity of the samples decreases with increasing x and the minimum lies between x = 0.2 and 0.3.
Abstract: A series of compounds with composition BaxLa1–xCoO3 (0 ≦ x ≦ 0.5) is synthesized. The rhombohedrally distorted perovskite LaCoO3 becomes cubic at x = 0.4. The electrical resistivity of the samples decreases with increasing x and the minimum lies between x = 0.2 and 0.3. The compounds with x ≧ 0.2 are ferromagnetic, but also possess a paramagnetic moment. At x = 0.5 the compound is metallic. The results can be explained by Zener double exchange as well as by Goodenough's itinerant electron ferromagnetism. Eine Reihe von Verbindungen mit der Zusammensetzung BaxLa1–xCoO3 (0 ≦ x ≦ 0,5) wird synthetisiert. Das rhombisch verzerrte Perovskit LaCoO3 wird bei x = 0,4 kubisch. Der elektrische Widerstand der Proben nimmt mit steigendem x ab, und das Minimum liegt zwischen x = 0,2 und 0,3. Die Verbindungen mit x ≧ 0,2 sind ferromagnetisch, besitzen jedoch auch ein paramagnetisches Moment. Bei x = 0,5 ist die Verbindung metallisch. Die Ergebnisse lassen sich sowohl mit dem Zenerschen Doppelaustausch als auch mit dem Ferromagnetismus itineranter Elektronen nach Goodenough erklaren.

36 citations


Journal ArticleDOI
TL;DR: In this article, the effect of suction or injection on velocity, microrotation, temperature, skin friction coefficient, wall couple stress coefficient, displacement and momentum thicknesses, rate of heat transfer and adiabatic wall temperature have been studied.

36 citations


Journal ArticleDOI
TL;DR: In this paper, the combined approach of quasilinearization and invariant imbedding is used for computing solutions of the nonlinear regularized long-wave (RLW) equation.

34 citations


Journal ArticleDOI
TL;DR: In this article, the assignment of chemical shifts for all the C atoms has been achieved by using techniques recently reported by Bose et al. They also examined the C NMR spectra of some naturally occurring furocoumarins and derivatives.

24 citations


Journal ArticleDOI
TL;DR: In this article, the effect of tetramethyl thiuram disulfide (TMTD) with amines on efficient vulcanization, semi-EV, and conventional sulfur vulcanisation was studied.
Abstract: Influence of hydrofuramide and ethanolamines on efficient vulcanization (EV), semi-EV, and conventional sulfur vulcanization accelerated by tetramethyl thiuram disulfide is reported. In the case of thiuram vulcanization, the amines increase the cure rate but reduce the crosslink density. The interaction of tetramethyl thiuram disulfide with amines has been studied. The amines interact with thiuram disulfide (TMTD) giving rise to the formation of gaseous products. Thermogravimetric analysis shows weight loss of about 50% in case of TMTD–ethanolamine system and 25% in case of TMTD–hydrofuramide system. Gas chromatographic studies of the gaseous products indicate that it consists mainly of H2S. The other constituents in the gaseous product are CO2 and a thiol. A possible reaction based on these observations to account for decrease in crosslink density in thiuram vulcanization caused by amines is reported.

23 citations



Journal ArticleDOI
TL;DR: In this article, the electrical and photovoltaic properties of SnO 2 -Si heterojunctions were investigated, and the results showed that the (n−n) and (n −p) heterojunction has better electrical properties than those of (n+p) and n−n, respectively.

Journal ArticleDOI
TL;DR: A 16-channel data acquisition system based on the Fairchild F8 microprocessor which stores and processes data and develops software for data logging at regular intervals, data logging on demand by the operator, limit checking, trend checking and self checking is reported.

Journal ArticleDOI
01 Sep 1979-Talanta
TL;DR: Xylene, toluene, benzene, chloroform, carbon tetrachloride, hexane, cyclohexane and kerosene have been studied as diluents and Xylene is found to be the most efficient.

Journal ArticleDOI
TL;DR: In this article, a photovoltaic output of 280 mV under Air Mass 1 conditions and a rectification ratio of the order of hundreds was achieved by depositing carbon onto single-crystal silicon.

Journal ArticleDOI
01 Jun 1979-Pramana
TL;DR: In this paper, a Ge (Li) detector was used to determine the cross-sections of lead, tantalum and molybdenum with 1.17 and 1.33 MeV rays between 30° and 115°.
Abstract: Elastic scattering cross-sections of lead, tantalum and molybdenum were determined with the help of a Ge (Li) detector for 1.17 and 1.33 MeV rays between 30° and 115°. Theoretical evaluations of the cross-sections are based on a coherent addition of the well-known nuclear Thomson scattering amplitudes, the Rayleigh amplitudes calculated by Kissel and Pratt and the Delbruck amplitudes given by Papatzacos and Mork. The fairly good agreement between experiment and theory reveals the importance of the real Delbruck amplitudes. However, the experimental results in the 30–60° range tend to lie slightly but systematically below the calculated cross-sections.

Journal ArticleDOI
TL;DR: In this paper, a numerical solution of the Fredholm integral equation describing the degradation has been attempted to restore images degraded by a linear shift variant (LSV) point spread function.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the effect of preadsorbed sulfur on the growth and stripping of the sulfur layer in the presence of adsorbed formic acid in the form of a sulfur layer from SO2 solutions.

Journal ArticleDOI
TL;DR: Based on a Boltzmann-like equation in reciprocal space, a theory was developed to describe sensitized fluorescence in molecular crystals in this article, where an expression for the energy transfer rate was derived and shown to be time dependent and to have the qualitative features of the experimental rate.

Journal ArticleDOI
TL;DR: In this article, a new approach is proposed to interpret the sounding data with the help of RMS difference in apparent resistivity values for three-layer earth-sections, the electrical resistivity in the intermediate layer of which has a linear variation with depth.
Abstract: Master curves are presented for three-layer earth-sections, the electrical resistivity in the intermediate layer of which has a linear variation with depth. A new approach is proposed to interpret the sounding data with the help of RMS difference in apparent resistivity values.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the chemical shifts ΔE of K-absorption edge of RCo3 and L3 absorption edge of Gd, Tb, and Dy in intermetallic compounds and estimated the effective charges on the absorbing ions.
Abstract: Chemical shifts ΔE of K-absorption edge of Co and L3-absorption edge of Gd, Tb, and Dy in GdCo3, TbCo3, and DyCo3 intermetallic compounds are measured and effective charges on the absorbing ions are estimated. It is found that the magnitudes of ΔE and q for Co in RCo3 (R refers to rare earth ions) lie in between those reported for RCo5 and RCo2 compounds. Further, ΔE and q of Co increase with increasing number of rare earth atoms per cobalt atom (RCo5 RCo3 > RCo2).

Journal ArticleDOI
TL;DR: In this article, the L3-absorption edges of Pt in RPt2 and RPt5 compounds are measured and correlated with the effective charges calculated using Siegbahn's method.
Abstract: Chemical shifts of the L3-absorption edges of Pt in RPt2 and RPt5 compounds are measured and correlated with the effective charges calculated using Siegbahn's method. It is found that the L3-edge shifts towards the lower-energy side of the Pt metal edge in RPt2 compounds, while in the case of RPt5 the shifts are in opposite direction. An attempt is made to explain the behviour of these chemical shifts. Es werden die chemischen Verschiebungen der L3-Absorptionskanten von Pt in RPt2- und RPt5-Verbindungen gemessen und mit den effektiven Ladungen verglichen, die mit der Methode von Siegbahn berechnet werden. Es wird gefunden, das die L3-Kante sich zur niederenergetischen Seite der Pt-Metallkante in RPt2-Verbindungen verschiebt, wahrend im Falle von RPt5 die Verschiebungen zur entgegengesetzten Seite erfolgen. Ein Versuch wird unternommen, das Verhalten dieser chemischen Verschiebungen zu klaren.

Journal ArticleDOI
01 Jul 1979-Pramana
TL;DR: In this paper, an alternative derivation of the projection method for constructing effective operators in the truncated shell model space is presented, and the results of explicit numerical calculations in three different nuclear regions are discussed.
Abstract: An alternative derivation of the projection method for constructing effective operators in the truncated shell model space is presented. The results of explicit numerical calculations in three different nuclear regions are discussed. Non-hermiticity of the effective Hamiltonian and various hermitisation procedures are investigated in detail.

Journal ArticleDOI
TL;DR: In this paper, numerical predictions for laminar free convective heat transfer to fluids in the nearcritical region from a vertical flat plate with uniform surface heat flux were made for various values of wall-heat flux ranging from 1000 W/M2 to 50 000W/M 2.

Journal ArticleDOI
TL;DR: In this paper, a generalized version of the broken-pair approximation was proposed for the case where both neutrons and protons are present in the valence shells, and the ground state for even-even nuclei was obtained for even Zr isotopes.
Abstract: A generalized approximation to seniority shell model, based on the number conserving quasiparticle theory, is presented which includes the cases where both neutrons and protons are present in the valance shells. The numerical calculations are carried out for even Zr isotopes. The results obtained compare well with the corresponding exact shell model results, demonstrating thereby the validity of the present approximation for this nuclear region. It is well known that the shell model or even the seniority (v (4) shell model calculations with con- figuration mixing are permanently limited to -the cases where only a few' valence particles are pres- ent in a few valence levels. This is because with the increase in the number of valence particles (levels), the dimension of the Hamiltonian matrix increases tremendously which is formidable in practice. However, in such practical calculations, the dimensions of the Hamiltonian matrices can be reduced if the problm is reviewed with some ap- proximation based on phenomenology derived from the effective nucleon-nucleon interactions. One such practical approximation is the quasiparticle model based on the strong pairing correlations among nucleons. Unfortunately, the rehults of the quasiparticle calculation do not correspond to the specific nucleus due to the noncommutability of the actual number operator with the quasiparticle Hamiltonian. This number nonconservation also introduces spurious states. To remove these drawbacks and to.retain the basic advantages of the model, various methods' ' based on the number projection, have been proposed. One such method is the broken-pair approximation (BPA), ' the val- idity of which has been demonstrated~' in the 2plf- region as well as for N=50, even A. nuclei. So far these projection methods have been applied only for the identical particles (neutrons 'or protons) in the valence shells. In this report we generalize the broken-pair approximation (referred to as GBPA) to include the cases where both the neutrons and the protons are active in the valence shells. Approaching the problem in the same manner as in the identical nucleon case, we write the approx- imate ground state for even-even nuclei as a pro- duct of a proton paired (p pairs) state T, l 0), and a neutron paired (n pairs) state 7tl0), i.e.,

Journal ArticleDOI
TL;DR: In this paper, the authors report easy-to-prepare spin-on solutions for boron and arsenic which give highly reproducible surface concentrations very close to the solid solubility limit.
Abstract: ‘Spin-on’ sources are commercially available either under brand names like ‘Accuspin’ or doped silicate films manufactured by various companies. However, the method of preparation of these doping solutions is not known and since almost all these solutions become jelly after a certain duration during which the viscosity changes, it is preferable to prepare one's own solution so that one can easily control the solution composition to a particular requirement and achieve reproducibility. In this paper, we report easy-to-prepare ‘spin-on’ solutions for boron and arsenic which give highly reproducible surface concentrations very close to the solid solubility limit. These solutions are useful for deep junction formation in silicon.

Journal ArticleDOI
TL;DR: In this paper, various chemical methods such as conventional coprecipitation, spray drying, pyrogel flame reactor, freeze drying, liquid drying, and pyrolysis of organic precursors suitable for preparing ferrite powders from aqueous salt solutions have been described.
Abstract: The preparation of powder plays an important role in the manufacture of sintered ferrites. The characteristics of the ferrite powders are influenced by method of preparation which subsequently influence the properties of finished products. Various chemical methods such as conventional coprecipitation, spray drying, pyrogel flame reactor, freeze drying, liquid drying, and pyrolysis of organic precursors suitable for preparing ferrite powders from aqueous salt solutions have been described. The high degree of homogeneity, precise chemical composition and controlled particle size of ferrite powders prepared by these methods are found to be highly desirable for achieving good quality products with improved properties. The selection of a suitable chemical method of powder preparation in relation to the traditional practice of milling along with modern manufacturing methods will be helpful towards improving the quality of our industrial products which are now produced by the conventional ceramic processing.

Journal ArticleDOI
TL;DR: In this paper, a simple programmable procedure has been developed for the determination of the subduction coefficients for states of the unitary group U(n) under restrictions under the down arrow U( n/sub 1/) x u(n/sub 2/) for the spin-free states of many electron systems.
Abstract: The determination of the subduction coefficients for states of the unitary group U(n) under restrictions U(n) down arrow U(n/sub 1/) x U(n/sub 2/ has been considered for the spin-free states of many electron systems. With the aid of the transformation properties of the tensor basis spanning the irreducible representation of U(n) under the permutations of electron coordinates, a simple programmable procedure has been developed for the determination of these coefficients. The procedure is illustrated with a simple example.

Journal ArticleDOI
01 Sep 1979-Talanta
TL;DR: From knowledge of the distribution coefficients, several separations have been devised, such as separation of Fe(III) from alkali and alkaline earth metals, chromium, manganese, cobalt, nickel, copper, vanadium zirconium, thorium, uranium, yttrium and titanium.

Journal ArticleDOI
TL;DR: In this paper, azeotropic and two terminal solid solution type phase diagrams have been carried out. Solution models used for the synthesis range from ideal to regular, quasi-chemical and surrounded atom models.
Abstract: Synthesis of azeotropic and two terminal solid solution type phase diagrams has been carried out. Solution models used for the synthesis range from ideal to regular,quasi-chemical and surrounded atom models. In general, it is observed that the regular solution model is satisfactory, though the quasi-chemical model shows better approximation to experimentally determined diagrams. Synthesis based on the surrounded atom model shows marked deviations from that of the experimental diagrams. The discrepancy may be due to the errors in the calculations of the vibrational frequencies of the central atom for different configurations.