Showing papers by "Indian Institute of Technology Madras published in 1974"
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01 Jan 1974TL;DR: Topics covered include: cardiac ultrastructure and function in the normal and failing heart, myocardial energetics, clinical applications of angiocardiography, use of echocardiographic for evaluating cardiac performance, systolic time intervals in the noninvasive assessment of left ventricular performance in man, and evaluation of passive elastic stiffness for the left ventricle and isolated heart muscle.
Abstract: Recent studies concerning the basic physiological and biochemical principles underlying cardiac muscle contraction, methods for the assessment of cardiac function in the clinical situation, and mathematical approaches to cardiac mechanics are presented. Some of the topics covered include: cardiac ultrastructure and function in the normal and failing heart, myocardial energetics, clinical applications of angiocardiography, use of echocardiography for evaluating cardiac performance, systolic time intervals in the noninvasive assessment of left ventricular performance in man, evaluation of passive elastic stiffness for the left ventricle and isolated heart muscle, a conceptual model of myocardial infarction and cardiogenic shock, application of Huxley's sliding-filament theory to the mechanics of normal and hypertrophied cardiac muscle, and a rheological modeling of the intact left ventricle. Individual items are announced in this issue.
76 citations
TL;DR: In this article, the authors describe the design, construction, and testing of a speed control unit for a separately excited dc motor fed from a three-phase six-pulse fully controlled thyristor bridge.
Abstract: This paper describes the design, construction, and testing of a thyristorized speed control unit for a separately excited dc motor. The motor is fed from a three-phase six-pulse fully controlled thyristor bridge. A speed loop with a proportional plus integral controller maintains the desired speed irrespective of the load variations on the motor. An inner current control loop protects the thyristors from overcurrents. This loop also provides fast response overcoming the effect of disturbances such as variations in supply voltage. The design aspects of the control loops are discussed, and experimental results are given.
64 citations
TL;DR: In this paper, different aspects of tool wear in ultrasonic drilling are presented, such as work material, tool material, work material thickness, tool size and cross sectional area, heat treatment of the tool, static load, cutting time and type of abrasives used.
32 citations
TL;DR: In this paper, a modified method to correctly determine the rubber membrane is presented along with the analysis of test results and some anomalies in these methods are examined, based on analysis and test results, in membrane penetration calibration tests using dummy rods, the writers suggest of the use of an annular flexible top platen leads to more reliable results.
Abstract: The methods available for membrane penetration calibration and some anomalies in these methods are examined. A modified method to correctly determine the rubber membrane is presented along with the analysis of test results. Based on analysis and test results, in membrane penetration calibration tests using dummy rods, the writers’ suggestion of the use of an annular flexible top platen leads to more reliable results and should be preferred to the use of conventional rigid top platen.
31 citations
TL;DR: In this paper, the interaction of pyrimidines with metal ions was investigated by a potentiometric method, and the stability constants of the complexes containing a 1:1 ratio of the ligand to the metal ion were reported at 45° and 0·10 M KNO 3 ionic strength.
27 citations
TL;DR: The electron impact-induced fragmentation in 2′-nitro-4-stilbazole is triggered by the oxidation of the olefinic double bond by the ortho nitro group in the initial step, while such an interaction under the same condition is totally absent in the meta and para isomers.
Abstract: The electron-impact-induced fragmentation in 2′-nitro-4-stilbazole is triggered by the oxidation of the olefinic double bond by the ortho nitro group in the initial step, while such an interaction under the same condition is totally absent in the meta and para isomers. The important fragmentation in 2′-nitro-2-stilbazole is the formation of a cyclised ion with the elimination of the nitro group.
27 citations
TL;DR: In this article, the conductive and radiative heat transfer to the walls of a Fluidized Bed Combustor is calculated based on a gas film-emulsion packet model, where coal and ash particles are assumed to be spherical and the bed is considered to be vigorously bubbling.
27 citations
TL;DR: In this article, the authors considered an isotropic plate continuous over an intermediate-rigid or elastic-support and free and with no in-plane loads at the outer edge.
26 citations
24 citations
TL;DR: In this article, the initial lattice distortion energy spectra of the films have been determined from the resistance-temperature data, and it is found that the resistivity values for films of different thicknesses are in good agreement with the size effect theory.
23 citations
TL;DR: In this paper, a detailed study of the large deflection behavior of skew plates has been made by varying three parameters, viz. skew angle, load, and aspect ratio, and representative non-dimensional solutions have been presented in the form of graphs to elucidate the nonlinear effect due to high loads.
01 Dec 1974
TL;DR: In this paper, a bandpass filter using only two resistors and two operational amplifiers is proposed, and the circuit has a Q equal to the ratio of the resistors.
Abstract: A bandpass filter using only two resistors and two operational amplifiers is suggested. The circuit has a Q equal to the ratio of the ressistors. While Q and gain are insensitive to temperature variations, the variations in center frequency is minimized uing a compensation scheme.
TL;DR: In this article, the ESR spectrum of Cu 2+ has been observed in the host single crystal Na 2 SO 4, where copper is trapped at four chemically as well as magnetically inequivalent sites.
01 Jun 1974
TL;DR: The E-system of roughness measurement can be used either for a two-dimensional or a three-dimensional assessment of surface roughness as mentioned in this paper, and the procedure for computing the two-and three dimensions is described in detail.
Abstract: The E-system of roughness measurement can be used either for a two-dimensional or a three-dimensional assessment of surface roughness. The procedure for computing the two- and three-dimensional env...
TL;DR: In this paper, the authors discuss the influence of abrasive particles on tool wear during ultrasonic machining and discuss the factors that influence the wear of a tool during the process.
TL;DR: The applicability of the split tensile test for the measurement of the tensile strength of cohesive soils is discussed in this paper, where the results of unconfined compression tests and split tensiles tests on cohesive soils compacted dry of optimum are presented.
TL;DR: A review of the studies on the structure of metallic glasses can be found in this paper, where a dense random packing model or modifications thereof can best explain the structure and range of stability of amorphous alloys.
Abstract: Metallic glasses or amorphous alloys have been produced by rapid quenching of alloys from the liquid or vapour phase. This paper is a review of the studies on the structure of metallic glasses. The theory of diffraction by amorphous materials is dealt with at length followed by a description of the procedure of obtaining and analysing the RDF of amorphous alloys. Various models have been put forward to explain the structure of the metallic glasses, and these are fully discussed. A dense random packing model or modifications thereof can best explain the structure and range of stability of amorphous alloys.
TL;DR: In this article, the growth rate of F-centres as a function of the time of X-irradiation and the thermoluminescence (TL) of Xray colored cesium halides have been studied.
Abstract: The growth rate of F-centres as a function of the time of X-irradiation and the thermoluminescence (TL) of X-ray colored cesium halides have been studied. In the case of CsCl and CsBr the effect of cadmium impurity is to suppress the growth of the F-band. The first stage growth of F-centres has been analysed into further ‘exponential’ substages. The first stage in CsBr consists of at least two substages whereas the analysis of CsCl crystals yielded only one substage for the first stage. Two TL glow peaks have been found in X-irradiated CsBr at 110 and 125 °C. The results suggest that these are due to the recombination of the F-centre electrons with holes. In CsCl, the TL glow peaks attributable to F-centres are observed at 100, 120, and 135 °C. In Cd-doped crystals new glow peaks have been observed which have been attributed to centres involving Cd-impurity, by comparison with optical absorption studies. The trap depths of the glow peaks have been evaluated using the ‘initial rise method’.
Es wird die Bildungsgeschwindigkeit von F-Zentren in Abhangigkeit von der Rontgen-bestrahlungsdauer und die Thermolumineszenz (TL) von mit Rontgenstrahlen verfarbten Casiumhalogeniden untersucht. Im Falle von CsCl und CsBr verringern Kadmiumverun-reinigungen das Wachsen der F-Bande. Das erste Stadium der Bildung der F-Zentren wurde in weitere „exponentielle” Unterzustande zerlegt. Das erste Stadium in CsBr besteht aus wenigstens zwei Unterzustanden, wahrend die Analyse von CsCl-Kristallen nur einen Unterzustand fur den ersten Zustand liefert. Zwei TL-Glow-Maxima wurden in rontgenbestrahltem CsBr bei 110 und 125 °C gefunden. Die Ergebnisse zeigen, das diese durch die Rekombination von F-Zentrenelektronen mit Lochern verursacht werden. In CsCl werden die TL-Glowmaxima, die den F-Zentren zugeordnet werden konnen, bei 100, 120 und 135 °C beobachtet. In Cd-dotierten Kristallen wurden neue Glowmaxima gefunden, die durch Vergleich mit optischen Absorptionsuntersuchungen Zentren zugeordnet werden, an denen die Cd-Verunreinigung beteiligt ist. Die Haftstellentiefen der Glowmaxima wurden mit der Methode des „Anfangsanstiegs” berechnet.
TL;DR: In this paper, a single-crystal EPR study of copper(II) doped into the ammonium salt of catena-di-μ-chromato-diammine zincate (CDSZ) was carried out at room temperature and at 77 K. The spin Hamiltonian parameters correspond to a dz2 ground state consistent with axial compression of the ammonia ligands around the central atom reported from X-ray data.
TL;DR: In this paper, the authors reviewed the computational approach to the two-dimensional envelope and the extension of the same method to compute the threedimensional envelope is explained with reference to 2D profiles obtainable with single stylus instruments.
TL;DR: In this paper, the role of roughness in the performance of such fits was investigated, and the ability for such assemblies to withstand repeated dismantling was also analyzed, where the authors showed that the load carrying capacity of press and shrink fitted assemblies, among other factors, depends appreciably on the roughness of the mating parts.
Abstract: The load carrying capacity of press and shrink fitted assemblies, among other factors, depends appreciably on the roughness of the mating parts. Experimental investigations showed the role of roughness in the performance of such fits. The ability for such assemblies to withstand repeated dismantling was also analysed. Details and discussions of the results obtained are presented in this paper.
TL;DR: The results of electron paramagnetic resonance studies of VO2+ in KBr and KI are reported over a wide temperature range as discussed by the authors, and the spin-Hamiltonian parameters at room and liquid-nitrogen temperatures are determined, and study of their dependence on the lattice constant shows that the hyperfine parameter (A0) increases while g0 and linewidth decrease.
01 Jul 1974
TL;DR: The example of double-exponentially distributed working-times is used to examine the dependancy of these characteristics on repair-times, and to calculate the optimal repair-rate.
Abstract: Es wird die Zuverlassigkeit eines Systems mit mehreren redundanten Einheiten untersucht, bei dem nicht nur die tatige Einheit, sondern auch die Reserveeinheiten ausfallen und bei dem gestorte Einheiten repariert werden konnen. Es wird vorausgesetzt, das die Reparaturzeiten und die Lebensdauern der Reserveeinheiten exponentialverteilt sind, wahrend die Betriebsdauern der tatigen Einheiten, unabhangig von ihrem Alter beim Einsatz, beliebig verteilt sind. Unter diesen Voraussetzungen werden die mittlere Zeit bis zum Ausfall des Systems und die langfristige Verfugbarkeit des Systems explizit fur den Fall dreier Einheiten bestimmt. Am Beispiel doppel-exponentialverteilter Betriebsdauern werden die Abhangigkeit dieser Grosen von der Reparaturgeschwindigkeit untersucht und die optimale Reparaturrate bestimmt.
TL;DR: A new bronze-type phase of composition (NH 4 ) 0.40±0.02 V 2 O 5 is obtained around 230°C during the thermal decomposition of NH 4 VO 3 in hydrogen atmosphere as discussed by the authors.
TL;DR: In this article, the dynamics of a fifteen layer thick semi-infinite slab having the NaCl structure with the free surfaces normal to the [110] direction has been investigated and it was found to be unstable towards the lowest lying acoustic modes for a range of wave vectors along [10] and [01] directions in the Brillouin zone.
TL;DR: In this article, the correlation between the surface roughness (R a and R t ), groove wear and built up edge was discussed, and the variation of the groove wear profile, built-up edge adhering to the machined surface and surface roughs have been studied.
TL;DR: In this article, the reactions of zinc oxide with α-Fe2O3 and with γ-Fe 2O3 leading to the formation of zinc ferrite (ZnFe 2 O4) have been studied at different partial pressures of oxygen in the temperature range 500-800°C.
TL;DR: In this article, the authors used a simple pulse circuit and ionization probes to measure the burning velocity of a combustible mixture, and computed the burning velocities from this data.
TL;DR: In this article, a method of analysing large amplitude vibrations of circular plates with mixed boundary conditions is explained and illustrated with an example where part of the boundary is clamped and the remaining simply-supported.