Showing papers by "Vikram Sarabhai Space Centre published in 1983"
TL;DR: In this paper, a modified finite element formulation to study the postbuckling behavior of elastic circular plates is presented and a discussion on the derivation of nonlinear stiffness matrix for post-buckling analysis is included and the present results are compared with continuum solutions.
52 citations
TL;DR: In this article, a simple finite-element formulation for the study of postbuckling behaviour of orthotropic circular plates is presented in detail, in the form of radial load ratios along with their corresponding empirical formulae in terms of central deflection to thickness ratios of the plates.
37 citations
25 citations
TL;DR: In this paper, the authors derived correlations between kinetic parameters (energy of activation, E), procedural factors (sample mass, m, and heating rate, φ) and the dependent variables (the temperature of inception of reaction, Ti, and temperature Tα at which a constant fraction α has decomposed) for differential thermal analysis (DTA) and differential scanning calorimetry (DSC).
16 citations
TL;DR: In this paper, the authors present a detailed quantitative bound for the dimensionless parameters governing the behavior of pulsating thermally-driven cavity flow, which has not previously been observed and may be present in the work of others.
12 citations
TL;DR: In this paper, the triad and pentad intensities were calculated for the olefinic methylene carbon (C-1), and the pentad placements for the methine carbon(C-2) were also assigned using the data calculated for C-1 carbon.
Abstract: Carbon-13 Fourier-transform spectra (67.88 MHz) of 1,2-polybutadienes (PBDs) (I–IV) were obtained. The triad and pentad intensities were calculated for the olefinic methylene carbon (C-1). Bernoullian and first-order Markov-chain propagation statistics were tested to fit the experimental data. The pentad placements for the olefinic methine carbon (C-2) were also assigned using the data calculated for the C-1 carbon. Fine-structure splitting due to placements higher than pentads was observed for both C-1 and C-2 carbons in PBD samples III and IV.
12 citations
TL;DR: In this article, the effect of adhesion on the viscoelastic properties of the composites has been assessed, and it is found that the increase in adhesion increases the mechanical loss per cycle and modulus.
Abstract: Viscoelastic properties of short-fiber-reinforced natural rubber composites have been studied as a function of temperature and at different levels of adhesion. The effect of adhesion on the viscoelastic properties of the composites has been assessed, and it is found that the increase in adhesion increases the mechanical loss per cycle and modulus. With the increase in temperature the mechanical loss and modulus drop, indicating a possible deterioration of the adhesion at higher temperatures. Presence of carbon black increases the mechanical loss but does not necessarily increase the level of adhesion. The effect of overcuring has also been studied. Complex modulus of the composites displays an exponential behavior with the increase in volume fraction of fiber.
11 citations
11 citations
TL;DR: In this article, the combined effects of the Hall and the ionslip currents in a magnetohydrodynamic boundary layer flow were studied, and it was found that the skin-friction coefficient decreases and the displacement thickness increases due to these currents.
Abstract: The combined effects of the Hall and the ionslip currents in a magnetohydrodynamic (MHD) boundary layer flow are studied. It is found that the skin-friction coefficient decreases and the displacement thickness increases due to these currents.
9 citations
TL;DR: In this paper, a surface-supported catalyst, molybdenum oxide on silica-alumina, was used to yield saturated and unsaturated linear oligomers in the presence of a surface supported catalyst, and the reaction rates, structure, and molecular weight distribution of the products were found to be controlled by the choice of the solvent.
Abstract: Styrene was found to yield saturated and unsaturated linear oligomers in the presence of a surface-supported catalyst, molybdenum oxide on silica-alumina. The reaction rates, the structure, and the molecular weight distribution of the products were found to be controlled by the choice of the solvent. Higher-molecular-weight fractions were favored in isooctane, whereas low-molecular-weight oligomers were preferred in dioxane. The reaction followed first-order kinetics with respect to the monomer. End-group analysis suggests a probable cationic mechanism. Approximate transfer constants KtrKp were deduced from product distribution data. The behavior of the surface-supported catalyst was compared with other cationic catalyst systems.
8 citations
TL;DR: In this paper, the cis-trans isomerization of polybutadiene double bonds during metathesis degradation using WCl6/(CH3)4Sn catalyst system has been estimated kinetically along with productive met athesis.
Abstract: The cis-trans isomerization of polybutadiene double bonds during metathesis degradation using WCl6/(CH3)4Sn catalyst system has been estimated kinetically along with productive metathesis. The isomerization was followed both for noncrosslinked and for crosslinked polybutadiene. Ninety-six percent cis-1, 4 units are found to isomerize into ca. 75% trans-1, 4 units. The rate of stereomutation is found to be different in the presence and absence of a low-molecular-weight olefin. The results are explained with the help of a stereo model originally proposed by Katz (Advances in Organometallic Chemistry, Academic, New York, 1977, Vol. 16.)
TL;DR: In this article, the effect of shear deformation and rotary inertia on nonlinear flutter boundary is studied for various thicknesses of panel for end conditions of simply supported, clamped and partial restraint against rotation by a unified approach.
01 Oct 1983
TL;DR: In this article, the response of a gyropendulum subject to vertical harmonic excitation was analyzed and the principal region of instability lying about the nutational frequency of the system was identified.
Abstract: This paper concerns the response of a gyropendulum subject to vertical harmonic excitation. Instability of the Mathieu type is shown to occur, the principal region of instability lying about the nutational frequency of the system. Experimental results are presented which clearly indicate the validity of the theoretical prediction. It is also shown that an unstable gyroscopic system can be stabilized by vibrating the equipment with the proper choice of vibration parameters. In such cases, the additional stabilizing factor has been analytically derived. Based on the above analysis, practical suggestions for instrument design are also provided.
TL;DR: In this article, a numerical analysis is made of the unsteady two-dimensional heat and mass transfer in the vapour gas region of a gas-loaded heat pipe, and the parabolic mass, momentum, energy and species conservation equations for a symmetrical heat pipe are solved.
Abstract: A numerical analysis is made of the unsteady two-dimensional heat and mass transfer in the vapour gas region of a gas-loaded heat pipe. The parabolic mass, momentum, energy and species conservation equations for a symmetrical heat pipe are solved and the quantitative behaviour of the start up transient in the vapour gas region is presented.
TL;DR: The concept of nodal averaging technique with multiple design variables per element is studied in this paper as an alternate formulation for the nodal variables as design variables using tapered finite elements in the optimality criterion approach.
TL;DR: A new type of circuit model which is TSC for a fault set, consisting of all possible, i.e., unrestricted stuck-at faults on all the gate input and output signal lines is proposed.
Abstract: All the totally self checking (TSC) circuits known so far [3]-[8] restrict their fault sets to either single or multiple but unidirectional stuck-at faults. Meyer and Sundstrom [20] have considered on line diagnosis of unrestricted faults but the class of circuits proposed by them does not fall under the category of TSC circuits. This paper proposes a new type of circuit model which is TSC for a fault set, consisting of all possible, i.e., unrestricted stuck-at faults on all the gate input and output signal lines. The model uses redundancy in both space and time domains and realizes combinatorial functions. Some important properties of the model are brought out by a set of lemmas and theorems. The viability of the model is demonstrated by a circuit example which uses CMOS technology.
01 Apr 1983
TL;DR: In this article, the theory of a gyroscope moving under gravity was extended to two types of suspension, free motion and forced horizontal vibration, and the fast precession was measured experimentally for the first time.
Abstract: The paper extends the theory of a gyroscope moving under gravity. Two types of suspension are investigated. In each case results are obtained for free motion and for forced horizontal vibration. As far as is known, fast precession was measured experimentally for the first time.