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Showing papers by "Indian Institute of Technology Kharagpur published in 1980"


Journal ArticleDOI
TL;DR: In this paper, a method of extending computation beyond the limit of the initial normal interval in Walsh series analysis of dynamical systems is presented, where the solution may be extended over contiguous normalized intervals of time to any length.
Abstract: This paper presents a method of extending computation beyond the limit of the initial normal interval in Walsh series analysis of dynamical systems. The solution may be extended over contiguous normalized intervals of time to any length. The procedure avoids operational matrices of prohibitively large size and reduces the computational effort to a minimum while retaining accuracy. As a by-product of the method, the solution at the segment junctions is also available in addition to the one in piecewise constant form. The formula also provides information regarding the stability of the resulting progression.

67 citations


Journal ArticleDOI
TL;DR: In this article, the results of an experimental investigation of the flow characteristics of a submerged horizontal jet flowing over a partly rigid and erodible bed are presented; the diffusion characteristics of the jet, growth of boundary layer thickness, velocity distribution within the boundary layer, critical shear stress at equilibrium stage, and the time variation of shear stresses at the location of maximum scour have been investigated.
Abstract: The results of an experimental investigation of the flow characteristics of a submerged horizontal jet flowing over a partly rigid and erodible bed are presented. The diffusion characteristics of the jet, growth of boundary layer thickness, velocity distribution within the boundary layer, critical shear stress at equilibrium stage, and the time variation of shear stress at the location of maximum scour have been investigated. The expression of critical shear stress has been obtained from the solution of Von Karman's integral equation. A functional relationship of time variation of shear stress has been found out by correlating the dynamic pressure drop recorded by a Preston tube with the velocity distribution law developed from experimental data.

65 citations


Journal ArticleDOI
TL;DR: In this article, the Fermi-Dirac integral for narrow-gap semiconductors with spherical energy bands is derived and the role of this integral towards the convergence of the expansion of the screening charge density for impurity ions is described.
Abstract: Based on an analytical approximation (recently proposed by Joyce and Dixon) for the Fermi energy of an ideal Fermi gas, an expression for the Fermi energy of zincblende-symmetry narrow-gap semiconductors with spherical energy bands is derived. A formula for the Fermi-Dirac integral for such semiconductors is given and certain properties of the integral are discussed. As an additional study, the role of this Fermi-Dirac integral towards the convergence of the expansion of the screening charge density for impurity ions in semiconductors is described.

42 citations


Journal ArticleDOI
TL;DR: Combined resistivity and induced polarisation (time domain) soundings were carried out near Fredericton Junction, New Brunswick, Canada in order to delineate saline water and fresh water zones as discussed by the authors.

41 citations


Journal ArticleDOI
TL;DR: A polyesterimide was prepared by reacting 4,4′-diaminodiphenylmethane with trimellitic acid anhydride in ethylene glycol, which acts as an esterification reagent as well as a solvent as discussed by the authors.
Abstract: A polyesterimide was prepared by reacting 4,4′-diaminodiphenylmethane with trimellitic acid anhydride in ethylene glycol, which acts as an esterification reagent as well as a solvent. The solution and thermal behaviour, and a few other properties were studied. The polymer was found to be soluble in highly polar solvents. The polymer solution was stable. Thermogravimetric data revealed that the polymer underwent only 10% weight loss in air at 300°C. Ein Polyesterimid wurde durch Reaktion von 4,4′-Diaminodiphenylmethan mit Trimellithsaureanhydrid in Ethylenglykol hergestellt. Letzteres dient sowohl der Veresterung als auch als Losungsmittel. Die Loslichkeit, das thermische Verhalten und einige andere Eigenschaften wurden studiert. Es wurde gefunden, das das Polymere in hochpolaren Losungsmitteln loslich und die Polymerlosung stabil ist. Thermogravimetrische Daten zeigten, das das Polymere bei 300°C in Luft nur 10% Gewichtsverlust erleidet.

39 citations


Journal ArticleDOI
TL;DR: In this article, a method of producing magnesium silicide and silane from rice husk is reported, which is shown to produce amorphous silica of very high purity, the use of such silica will lead to a purer Mg 2 Si and silanes.

38 citations


Journal ArticleDOI
TL;DR: In this paper, a tensile ruptured gum specimen shows formation of crystalline regions at an angle of 45° to the flow lines, whereas the surface is rough and brittle.
Abstract: A tensile ruptured gum specimen shows formation of crystalline regions at an angle of 45° to the flow lines, whereas a tensile ruptured filled specimen shows formation of depression. A tear fractured gum specimen shows again the formation of crystallites at an angle of 45° to the flow lines. Tear fractured filled specimens show the enhancement of crystallinity throughout the matrix, but the surface is rough. Flex fractured gum specimen show a large number of cracks on the surface while the filled vulcanizate shows formation of balls presumably due to coiling of polymer chains on the filler surface. An abraded gum surface shows dimple structure, while a filled vulcanizate indicates coarse ribbed structure. Addition of lignin, in general, reduces the crystallinity of tensile and tear fractured samples and increases the fibrosity of flex cracked and abraded samples.

37 citations


Journal ArticleDOI
TL;DR: In this paper, an exact solution of the governing equations for the fully developed flow was obtained in closed form, and the solution in dimensionless form contains three parameters: the Hartman NumberM2,K2, the reciprocal of the Ekman Number, and ω the frequency of oscillation.
Abstract: The unsteady hydromagnetic flow of a viscous incompressible fluid in the presence of a uniform transverse magnetic field in a rotating parallel plate channel with oscillating pressure gradient is investigated. An exact solution of the governing equations for the fully developed flow is obtained in closed form. The solution in dimensionless form contains three parameters: the Hartman NumberM2,K2, the reciprocal of the Ekman Number, and ω the frequency of oscillation. The effects of these parameters on the flow field are studied. For large values ofK2 and ω there arise thin double-decker boundary layers near the plates of the channel and thin boundary layers for largeM2.

35 citations


Journal ArticleDOI
TL;DR: The purpose of this paper is to clarify the relations and to provide some selection guides among several time-series identification algorithms that appear in the literature under different names but which are essentially least-squares identification algorithms where only the numerical solution of the least-Squares estimation problem is different.

35 citations


Journal ArticleDOI
TL;DR: In this paper, the combined effect of rotation and Hall current on the MHD Couette flow has been studied and the heat transfer characteristic has also been discussed on taking the viscous and Joule dissipation into account.
Abstract: The combined effect of rotation and Hall current on the MHD Couette flow have been studied. The heat transfer characteristic have also been discussed on taking the viscous and Joule dissipation into account. The primary and the secondary velocity components increase with increase in Hall parameter but the primary velocity decreases with increase in rotation parameter. It is seen that the rate of heat transfer at the stationary plate is independent of both the Hall parameter and the rotation parameter. The rate of heat transfer at the moving plate increases with increase in Hall parameter, while it decreases with increase in rotation parameter. The values of the critical Eckert number at which the direction of the heat flow changes increases with increase in Hall parameter.

34 citations


Journal ArticleDOI
TL;DR: In this paper, the fracture surfaces of a NBR vulcanizate after different test conditions have been studied by scanning electron microscopy, and it has been shown that failure surfaces manifest typical characteristics dependent on the nature of the test.
Abstract: The fracture surfaces of a NBR vulcanizate after different test conditions have been studied by scanning electron microscopy. It has been shown that failure surfaces manifest typical characteristics dependent on the nature of the test. Tensile fracture surface shows occurrence of two different tear rates in the case of a filled NBR vulcanizate, while tear fracture is characterized by a few long flow lines. De Mattia flexing leads to layering of polymer fibers. Heat buildup and abrasion tests generate a ribbed structure on the surface.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the variations of air core diameter, the most important hydrodynamic picture inside a swirl nozzle, with the pertinent guiding parameters like injection condition expressed as the Reynolds number at inlet to the nozzle and the geometrical dimensions of the nozzle, namely, the length and diameter of the swirl chamber, angle of spin chamber and the orifice diameter.
Abstract: Theoretical and experimental studies have been made to investigate the variations of air core diameter, the most important hydrodynamic picture inside a swirl nozzle, with the pertinent guiding parameters like injection condition expressed as the Reynolds number at inlet to the nozzle and the geometrical dimensions of the nozzle, namely, the length and diameter of the swirl chamber, angle of spin chamber and the orifice diameter. The theoretical relations have been established through an approximated analytical solution of the hydrodynamics of flow of a viscous incompressible fluid in a swirl nozzle. A series of experiments have been carried out to support and compare the theoretical results. Finally, it has been recognized that for any nozzle, the air core diameter becomes a direct function of Reynolds number Re i at inlet to the nozzle only at its lower range and then remains constant. Amongst the nozzle geometrics, the ratio of orifice to swirl chamber diameter D 2/D 1 has got the most predominant effect on the air core diameter. An increase in the ratio of orifice to swirl chamber diameter D 2/D 1, and in the spin chamber angle 2α and a decrease in the swirl chamber length to diameter ratio L 1/D 1 increase the ratio of air core to orifice diameter and vice versa.

Journal ArticleDOI
TL;DR: In this paper, the equations governing the fluid flow and heat transfer have been solved subject to the relevant boundary conditions by assuming that the solution consists of two parts: a mean part and a perturbed part.
Abstract: The equations governing the fluid flow and heat transfer have been solved subject to the relevant boundary conditions by assuming that the solution consists of two parts: a mean part and a perturbed part. To obtain the perturbed part of the solution, use has been made of the long-wave approximation. The mean part of the solution has been found to be in good agreement with that of the plane Poiseuille flow. The perturbed part of the solution is the contribution from the waviness of the walls. The mean part, the perturbed part and the total solution of the problem have been evaluated numerically for several sets of values of the parameters. Certain qualitatively interesting properties of the fluid flow and heat transfer, along with the changes in the fluid pressure on the wavy walls, are recorded in § § 5 and 6.

Journal ArticleDOI
TL;DR: In this article, the effect of temperature on the electrical conductivity of PVC-copper composites has been studied and the results showed that the temperature coefficient of dc resistivity of composites with fillers containing negligible oxide content in the range of 77-303 K is positive, indicating metallic-type conduction.
Abstract: Effect of temperature on the electrical conductivity of PVC-copper composites has been studied. The temperature coefficient of dc resistivity of composites with fillers containing negligible oxide content in the range of 77–303 K is positive, indicating metallic-type conduction. The temperature coefficient of dc resistivity of composites with fillers containing intermediate level of oxide at higher temperatures is negative, indicating a semiconducting behavior. Plots of log conductivity versus log frequency for composites in the insulating region show the hopping-type conduction.

Journal ArticleDOI
TL;DR: In this article, the development and testing of a cyclone type husk fired furnace which can be used either for heating the drying air or for generating steam in a boiler for parboiling of paddy in the rice mill is described.

Journal ArticleDOI
TL;DR: In this paper, the effects of curing temperature (150° and 180°C) and curing system (conventional and efficient vulcanization) on 1) the technical properties, 2) polymer-filler interaction and 3) network structure of NR-BR, NR-SBR, BR, SBR blends were studied.
Abstract: In the present paper we have studied the effects of curing temperature (150° and 180°C) and curing system (conventional and efficient vulcanization) on 1) the technical properties, 2) polymer-filler interaction and 3) network structure of NR-BR, NR-SBR-BR, NR-SBR blends. On the basis of cure rate and interphase crosslinking, it has been suggested that the tendency to form mechanically compatible blends follows the order NR-BR > NR-SBR-BR > NR-SBR. It is the interplay of the network structure and polymer-filler interaction which controls the properties of the blend vulcanizates. The resilience, heat build-up and set properties depend more on the network structure, while the tensile, tear and fatigue resistance are influenced more by the polymer-filler interaction.

Journal ArticleDOI
TL;DR: In this article, the authors presented computer generated design data in terms of load capacity and oil flow for multirecess hydrostatic journal bearings for various L/D ratios, recess to bearing area ratios, number of recesses etc.

Journal ArticleDOI
TL;DR: PVC-Cu composites with chemically deposited ultrafine (0.1 to 0.3 μm diameter) copper particles were prepared by hot-pressing copper-coated PVC powder (−106, +150 μm) at 120° C as mentioned in this paper.
Abstract: PVC-Cu composites with chemically deposited ultrafine (0.1 to 0.3 μm diameter) copper particles were prepared by hot-pressing copper-coated PVC powder (−106, +150 μm) at 120° C. Metallic copper in fine-particle form was deposited on the PVC particles by reducing an ammoniacal cupric acetate solution with hydrazine at 85° C. The electrical resistivity (d.c.) and transverse rupture strength of these composites were measured. Measurement of electrical resistivity indicated that in these composites copper particle network formation was initiated at a copper content of about 0.2 vol%; with further increase of copper content the resistivity dropped sharply from about 1014 (for pure PVC) to about 105 MN m−2 Ωcm at a copper content of about 0.5 vol%. Increase of copper loading beyond 0.5 vol% did not decrease resistivity significantly whereas the rupture strength increased continuously from 120 MN m−2 (for pure PVC) to a value of about 300 MN m−2 with 4 vol% copper loading. This high value of resistivity even after copper particle chain formation and the continuous increase of rupture strength, is thought to be due to formation of a thin layer of polymer film between the copper particles introducing a “quasi-random” character to the otherwise segregated network of copper particles.

Journal ArticleDOI
TL;DR: In this article, the lateral pressure transmittal through different types of backfill material; characterized through a material parameter E/G; subjected to various types of contact pressure on its surface is evaluated theoretically by the use of the concept, in which it is considered that E /G < 2(l + v).


Journal ArticleDOI
TL;DR: In this article, the authors considered thermal instability in a heat conducting micropolar fluid layer under the influence of a transverse magnetic field and solved the eigenvalue problem using finite-difference and Wilkinson's iteration techniques.


Journal ArticleDOI
TL;DR: In this article, a method of including the effect of unknown initial conditions in the general algorithms for transfer function synthesis via Poisson moment functionals was presented, and tested with process data containing zero mean noise and is found to be remarkably immune to such noise.
Abstract: This paper presents a method of including the effect, of unknown initial conditions in the general algorithms for transfer function synthesis recently developed by the authors (Saha and Prasada Rao 1979) via Poisson moment functionals. The proposed technique is of considerable practical importance in problems of parameter identification in which input-output data is available on an arbitrary but active interval of time. The technique is tested with process data containing zero mean noise and is found to be remarkably immune to such noise.

Journal ArticleDOI
TL;DR: In this article, a simple correlation has been developed to predict the expansion of a liquid fluidized bed, consisting of particles varying in size and/or density, which is valid over the voidage range from ϵmf to ϵr = 0.96 and gives directly the expanded bed height.
Abstract: A simple correlation has been developed to predict the expansion of a liquid fluidized bed, consisting of particles varying in size and/or density, which is of the following form: The relationship is valid over the voidage range from ϵmf to ϵr = 0.96 and gives directly the expanded bed height Le without the determination of the bed porosity ϵe as in existing correlations. The size and density of the solids varied from 30/40 to 72/80 mesh BSS and from 1.67 to 4.33 gm/cm3 respectively while the range of Ret varied from 0.12 to 43.66. The standard deviation for measurements on unicomponent and multicomponent systems has been calculated to be 11.5% and 19.6% respectively at an L/D ratio of 2.0. On a etabli une correlation simple pour prevoir l'expansion d'un lit fluidise en phase liquide, forme de particules de dimensions et/ou de densite variables; cette correlation est de la forme suivante: Cette relation est valable sur une gamme de degre de vide de ϵmf a ϵe = 0.96, et fournit directement la hauteur Le du lit, sans qu'on ait a determiner la porosite ϵe du lit, comme c'est le cas pour les autres correlations existantes. Les dimensions des solides variaient entre 30/40 et 72/80 mailles BSS et leurs densites etaient comprises entre 1.67 et 4.33 g/cc, alors que Ret variait entre 0.12 et 43.66. On a calcule que pour un rapport L/D de 2, les ecarts normaux dans le cas des mesures effectuees dans des systemes a composants simples et multiples etaient respectivement de 11.5% et 19.6.%

Journal ArticleDOI
TL;DR: In this article, an optimum substrate temperature of 453 K was found for the preparation of thin film In 2 Te 3 by electron beam evaporation, which exhibited a maximum hole mobility of 48 cm 2 V -1 s -1 and a maximum concentration of 4.2 × 10 18 cm -3.

Journal ArticleDOI
TL;DR: In this paper, a series of binary alkali borate glasses has been investigated to study the energy storage mechanism of these materials and the broad and complex nature of the glow pattern is attributed to distribution of trap depths in these materials.
Abstract: Thermoluminescence behaviour of a series of binary alkali borate glasses has been investigated to study their energy storage mechanism. Sodium borate glasses of varying composition have been prepared and their glow curves recorded after exposing them to X-rays (CuKα radiation, 30 kV, 10 mA) of different dosages at room temperature. The effect of the nature and concentration of alkali oxide and the dose of irradiation on the nature of thermoluminescent glow curves were also studied. Borate glasses containing different concentrations of Na2O exhibit significantly different glow curves. These glow curves have been analysed and the nature of traps responsible for TL emission are tentatively identified. The broad and complex nature of the glow pattern is attributed to distribution of trap depths in these materials. The viability of borate glasses in the construction of TL dosimeters are discussed.

Journal ArticleDOI
01 Dec 1980-Polymer
TL;DR: In this paper, the degree of paracrystallinity in cellulose fibres of hemp, jute, and ramie has been investigated and a method of determining this parameter has been proposed.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the dielectric constant (K), loss (tan δ), and conductivity (σ) of PbI2 as a function of frequency in the range 102 to 107 Hz and at temperatures between 77 to 560 K.
Abstract: Dielectric constant (K), loss (tan δ), and conductivity (σ) of single crystals of PbI2 are measured (E ∥ c-axis) as a function of frequency in the range 102 to 107 Hz and at temperatures between 77 to 560 K. At room temperature (≈ 303 K), the K-value at 106 Hz is 6.7. The dielectric constant of this crystals increases slowly with temperature up to about 300 K (this increase being practically frequency-independent) beyond which the K increase is fast and frequency-dependent; this later stage of increase of K is attributed to an appreciable space charge polarisation (due to crystal defects) at such temperatures. The activation energy for intrinsic conduction (beyond 450 K) is calculated to be 0.44 eV from the lg σ versus 1/T plots at different frequencies. The lg (ΔK) versus 1/T plots at different frequencies for this crystal (where ΔK is the difference between the value of the dielectric constant at any temperature T and that value at room temperature) are straight lines from about 400 K, having the same slope for all frequencies; the activation energy is 0.41 eV. This agreement between the two activation energy values suggests that the same charge carriers are responsible for the two processes.


Journal ArticleDOI
TL;DR: In this article, the problem of thermal stresses in a hollow anisotropic cylinder of finite extent arising from axisymmetric temperature variations at the plane ends, the inner and outer curved surfaces being in contact with rigid and smooth insulators was dealt with.
Abstract: This paper deals with the problem of thermal stresses in a hollow anisotropic cylinder of finite extent arising from axisymmetric temperature variations at the plane ends, the inner and outer curved surfaces being in contact with rigid and smooth insulators. An exact solution is developed using potential functions of displacement. Numerical results are given for cylinders made of magnesium (anisotropic) and copper (isotropic).