Showing papers by "Indian Institute of Technology Bombay published in 1978"
TL;DR: In this paper, the energy levels of two simple examples of screened Coulomb potentials have been analyzed using nonperturbative methods, and the analysis indicates that the energy level as a function of the perturbation parameter has a branch cut along the negative real axis; starting from the origin.
Abstract: The energy levels of two simple examples of screened Coulomb potentials have been analyzed using nonperturbative methods. The analysis indicates that the energy levels as a function of the perturbation parameter ) have a branch cut along the negative real axis; starting from the origin. Furthermore, there are singularities on the second sheet, along ~X~e '' for ~X ~0. As a consequence of these singularities, the energy levels have an asymptotic series in X, which means that orie cannot use a power series in X to describe the energy levels to an arbitrary accuracy, The approximate but nonperturbative expression for the energy levels, which has been obtained by using dispersion relations, predicts energy levels which are in good agreement with those obtained from variational calculations.
57 citations
TL;DR: In this paper, it was shown that at θS 0.9, the formation of a partial bilayer on top of the first layer can be explained by the presence of two forms of "difficultly reducible" oxygen.
54 citations
TL;DR: In this article, the effect of preadsorbed sulfur layer on the anodic oxidation of formic acid at a platinized platinum electrode was investigated and it was shown that, in the presence of the sulfur layer, the oxidation process obeys the following rate expression.
43 citations
TL;DR: This paper presents a structural hypothesis about textures that are describable as recursively nested intensity regions and argues that gray level peaks should be used as textural primitives upon which recursion is based, and the use of several basic peak attributes is proposed for purposes of description.
42 citations
TL;DR: Although this study arose in the design of a buffer for digital voice-data systems, the queueing model developed is quite general and may be useful for other industrial applications.
Abstract: A queueing model with finite buffer size, Poisson arrival process, synchronous transmission and server interruptions is studied through a Bernoulli sequence of independent random variables. An integrated digital voice-data system with Synchronous Time-Division Multiplexing (STDM) for voice sources and Poisson arrival process for data messages is considered as an application for this model. The relationships among overflow probabilities, buffer size and expected queueing delay due to buffering for various traffic intensities are obtained. The results of this study are portrayed on graphs and may be used as guide lines for the buffer design in digital voice-data systems. Although this study arose in the design of a buffer for digital voice-data systems, the queueing model developed is quite general and may be useful for other industrial applications.
39 citations
01 Jan 1978
32 citations
TL;DR: In this article, the role of strain in the fracture of low strength steel in the temperature range of −196 to 28°C and at the crack tip strain rate range of 10 −5 to 10°/sec.
23 citations
TL;DR: In this article, a generalized concept of stresses in molecular systems is presented, which is likely to yield considerable insight into molecular phenomena such as chemical binding, molecular geometry, chemical reactivity and transferability of fragment properties from one molecule to another.
Abstract: In this paper a generalized concept of stresses in molecular systems is presented. The stress tensor in the 3-D space of a molecule, defined in terms of internal fields arising from its nuclear and electronic distributions, has components with forms reminiscent of Maxwell's stress tensor for classical electromagnetic fields. As an illustrative example, the stress tensor has been calculated for the 1s, 2s and 2p x states of the hydrogen atom. The physical significance of the various components of the stress tensor is also examined. The stress concept is likely to yield considerable insight into molecular phenomena such as chemical binding, molecular geometry, chemical reactivity and transferability of fragment properties from one molecule to another.
23 citations
TL;DR: Of various liquid anion-exchangers tested, Amberlite LA-1 was found to be best and separated from scandium, zirconium, thorium and vanadium(V) was done by exploiting differences in the stability of chloro-complexes.
22 citations
TL;DR: In this article, the authors studied the thermal boundary-layer flow past a circular cylinder whose axis is placed normal to an oncoming free stream of an incompressible micropolar fluid.
19 citations
TL;DR: In some prevalent systems such as composite steel-concrete beams, layered wood construction connected with nails, rock joints, and rafted and shell foundations, the assumption of rigid interconnection between the contact surface is questionable as discussed by the authors.
Abstract: In civil engineering practices, there are many structures where surfaces, either curved or plane, remain in contact with one another. In such cases the contact stresses depend on interfacial slip which can significantly affect the overall behavior of the structure. In some prevalent systems such as composite steel-concrete beams, layered wood construction connected with nails, rock joints, and rafted and shell foundations, the assumption of rigid interconnection between the contact surface is questionable. In numerical analysis of such jointed and layered systems using finite elements, the introduction of interface elements has proved to be the most useful.
TL;DR: A new method for the extractive separation of hafnium from zirconium is presented and it is possible to accomplish clean separations of Hf from Zr in ratios from 1:20 to 1:200.
TL;DR: Although this problem arose in the study of data interpolation in STDM and TASI systems, the queueing model developed is quite general and may be useful for other industrial applications.
TL;DR: In this article, a finite difference scheme with triangular mesh is presented for the analysis of skew plate problems with large deflections, which is independent of the boundary condition and uses energy principles to derive a set of nonlinear algebraic equations which are solved by using Newton-Raphson iterative method with incremental loading.
TL;DR: In this article, a three noded, 18 d.o.f. superparametric beam element is developed for beams of variable rectangular cross section, arbitrarily curved in space, which is combined with the existing eight noded 40 d.O.F. super-parametric shell element for shell beam systems, and some simple problems of beams and a four-beam slab are analyzed.
TL;DR: ExpressExpressions for trapping and detrapping rates, which describe transitions from (and to) the host crystal to (and from) the trap states, are derived from the point of view of their ϰ-dependence as discussed by the authors.
Abstract: Expressions for trapping (and detrapping) rates, which describe transitions from (and to) the ϰ-states of the host crystal to (and from) the trap states, and which serve as inputs in a theory of sensitized fluorescence in molecular crystals, are derived from the point of view of their ϰ-dependence. They are shown to be consistent with experimental observations.
Ausdrucke fur die Anhaft- (und Anregungs)raten, die die Ubergange von (und zu) den ϰ-Zustanden des Wirtskristalls zu (und von) Haftstellen beschreiben und die als Eingangswerte in eine Theorie der sensibilisierten Fluoreszenz in Molekulkristallen dienen, werden vom Standpunkt ihrer ϰ-Abhangigkeit abgeleitet. Es wird gezeigt, das sie mit experimentellen Beobachtungen konsistent sind.
Book•
01 Jan 1978TL;DR: In this paper, a detailed discussion of fundamental concepts including linear elastic fracture mechanics (LEFM), yielding fracture mechanics, mixed mode fracture, and computational aspects of LEM are discussed.
Abstract: Fracture mechanics studies the development and spreading of cracks in materials. The study uses two techniques including analytical and experimental solid mechanics. The former is used to determine the driving force on a crack and the latter is used to measure material's resistance to fracture. The text begins with a detailed discussion of fundamental concepts including linear elastic fracture mechanics (LEFM), yielding fracture mechanics, mixed mode fracture and computational aspects of linear elastic fracture mechanics. It explains important topics including Griffith theory of brittle crack propagation and its Irwin and Orowan modification, calculation of theoretical cohesive strength of materials through an atomic model and analytical determination of crack tip stress field. This book covers MATLAB programs for calculating fatigue life under variable amplitude cyclic loading. The experimental measurements of fracture toughness parameters KIC, JIC and crack opening displacement (COD) are provided in the last chapter.
TL;DR: In this paper, an improved substructure analysis method suitable for structures like multi-storied buildings and towers is presented, which is based on peculiar geometry of these structures which could be used for numbering the boundary joints for a substructure either in the beginning or towards the end.
TL;DR: In this paper, it was shown that tma coordinates with all the metal ions through sulphur and one of the oxygen atoms of the carboxylate group, and that all the complexes except that of Hg(II) decompose into their respective sulphates through the formation of intermediate sulphides.
11 Oct 1978
TL;DR: Eine Klassifikation wird mit Hilfe struktureller Methoden in einem durch Schwerpunkt and Vorzugsrichtungen des Objektes bestimmten Koordinatensystem durchgefuhrt.
Abstract: Es wird uber erste Ergebnisse zur Detektion von “man-made-objects” in Grauwertbildern berichtet. Bei der eindimensionalen Vorverarbeitung in Zeilen- und Spaltenrichtung werden nur die Extremwerte zur Berechnung eines Linienbildes durch lineare Regression benutzt. Jeder Linie zugeordnet sind u. a. Lagekoordinaten, Kontrastrichtung, mittlerer Kontrast und Streuung. Durch Schwellwerte fur Kontrast und Streuung und Filterung nach Vorzugsrichtungen ergibt sich die Position des Flachenschwerpunktes des Zielobjektes fur die bisher verarbeiteten 5 Fahrzeuge in guter Naherung. Eine Klassifikation wird mit Hilfe struktureller Methoden in einem durch Schwerpunkt und Vorzugsrichtungen des Objektes bestimmten Koordinatensystem durchgefuhrt.
TL;DR: This procedure presents a better picture of the effectiveness of the pulsewidth modulation schemes and presents a method of translating the frequency-spectrum characteristics of a pulsewidth-modulated inverter into its output filter kVA characteristics.
Abstract: The paper discusses two-and three-level types of pulse-width modulation and presents a method of translating the frequency-spectrum characteristics of a pulsewidth-modulated inverter into its output filter kVA characteristics. The effect of the modulation scheme on the kVA ratings of the inverter and its transformer are also discussed. This procedure presents a better picture of the effectiveness of the pulsewidth modulation schemes.
TL;DR: In this paper, the results of a chromatographic study of scandium on Dowex 50W-X8 were reported, and the results were evaluated in terms of the elution constant and bed distribution coefficient as H2SO4 > CH3COONH4 > NH4Cl > NaCl > HNO3 > HCl > NH 4NO3.
Abstract: Cation exchange chromatographic studies of scandium on Dowex 50W-X8 are reported. Mineral acids and their salts were tested as eluants. Their efficiency was evaluated in terms of the elution constant and the bed distribution coefficient as H2SO4 > CH3COONH4 > NH4Cl > NaCl > HNO3 > HCl > NH4NO3. Scandium was separated from alkali, alkaline earths, iron, zinc, cadmium, mercury, copper, indium, aluminum, vanadium, uranium, and bismuth by the process of selective elution. It was separated from titanium, zirconium, hafnium, and antimony by the process of selective sorption. Separation of cobalt, nickel, manganese, lead, and silver from scandium was accomplished with sodium chloride as an eluant. The separation from thorium was carried out by gradient elution with hydrochloric acid.
TL;DR: In this article, the availability and reliability analysis of a single-server two-unit hot standby system subject to preventive maintenance and repair is presented. But the analysis is carried out by identifying suitable imbedded regenerative stochastic processes.
TL;DR: In this article, the long optical vibrations of hexagonal BN are studied using the valence force constants of the borazine molecule and it is shown that the in-plane interactions are adequately described by the transferred molecular force constants.
Abstract: The long optical vibrations of hexagonal BN are studied using the valence force constants of the borazine molecule. It is shown that the in-plane interactions are adequately described by the transferred molecular force constants. The elastic constant (c11 + c12), calculated from the above model compares well with the experimentally deduced value. It is argued that the interplanar forces cannot be satisfactorily described by a simple Lennard-Jones potential.
Die langwelligen optischen Schwingungen von hexagonalem BN werden mit den Valenzkraftkonstanten des Borazinmolekuls untersucht. Es wird gezeigt, das die intra-planaren Wechselwirkungen adequat durch die ubertragenen Molekularkraftkonstanten beschrieben werden. Die elastischen Konstanten (c11 + c12), die mit diesem Modell berechnet werden, stimmen gut mit den experimentell ermittelten Werten uberein. Es wird angenommen, das die interplanaren Krafte nicht durch ein einfaches Lennard-Jones-Potential beschrieben werden konnen.
TL;DR: In this paper, the effect of circuit parameters on the inverter operation is discussed and the minimum circuit turnoff time during transient operation is evaluated in order to specify the safe operating frequency.
Abstract: Voltage-fed discontinuous current mode high-frequency inverters are widely used for induction heating and melting. An exact analysis of such a circuit with series-parallel compensated load is carried out in terms of dimensionless quantities. The effect of circuit parameters on the inverter operation is discussed. Minimum circuit turnoff time during transient operation is evaluated in order to specify the safe operating frequency. Control of circuit performance is discussed. It is shown that a feedback control system which maintains ?' between 35 and 40/s=deg/ ensures proper operating conditions.
01 Jun 1978
TL;DR: Gallium(III) can be quantitatively extracted at trace levels with monothiodibenzoylmethane in benzene at pH 5.0 and determined spectrophotometrically as its Rhodamine B complex in the organic phase, in the range 1.4-26 mug of gallium.
11 Oct 1978
TL;DR: In this article, the authors discuss the eindimensionale methodik der Linguistik auf zwei dimensionen auszudehnen, um linguistische Verfahren auch zur Beschreibung and Erkennung komplexer zweidimensionaler Muster (Bilder) einsetzen zu konnen.
Abstract: Es wird uber die wichtigsten Bestrebungen berichtet, die eindimensionale Methodik der Linguistik auf zwei Dimensionen auszudehnen, um dadurch linguistische Verfahren auch zur Beschreibung und Erkennung komplexer zweidimensionaler Muster (Bilder) einsetzen zu konnen. Won den dabei entwickelten Bildbeschreibungssprachen werden die PDL von Shaw, die Geflecht-Sprache von Feder, die Gewebe-Sprache von Pfaltz und Rosenfeld, die Graphen-Sprache von Pavlidis und die Baum-Sprache von Brainerd und Fu vorgestellt. Die verschiedenen Spracharten werden formal definiert, anhand von Beispielen erlautert und in ihren gegenseitigen Beziehungen diskutiert.