Showing papers by "Indian Institute of Technology Madras published in 1991"
TL;DR: An efficient non-hierarchical clustering algorithm, based on initial seeds obtained from the assignment method, for finding part-families and machine cells for group technology (GT) is presented in this article.
Abstract: An efficient nonhierarchical clustering algorithm, based on initial seeds obtained from the assignment method, for finding part-families and machine cells for group technology (GT) is presented. By a process of alternate clustering and generating seeds from rows and columns, the zero-one machine-component incidence matrix was block-diagonalized with the aim of minimizing exceptional elements (intercell movements) and blanks (machine idling). The algorithm is compared with the existing nonhierarchical clustering method and is found to yield favourable results.
215 citations
TL;DR: In this article, the boundary value problem is reduced to a set of coupled ordinary differential equations and then solved by the method of Frobenius by assuming suitable displacement functions, and the results are shown to give results identical to those of a stress function approach for a plane strain problem.
195 citations
TL;DR: In this article, a strain-controlled low cycle fatigue tests have been conducted in air between 298-873 K to ascertain the influence of temperature on LCF behavior of nitrogen-alloyed type 316L stainless steel.
127 citations
TL;DR: In this paper, the metal transfer from the tool electrode to the machined surface is studied by cross-sectional examination, electron spectroscopy for chemical analysis and X-ray diffraction analysis of the work surface.
103 citations
TL;DR: The algorithm is similar to the cepstral smoothing approach for formant extraction using homomorphic deconvolution but the logarithmic operation is replaced by ()' operation and the additive and high resolution properties of group delay functions are exploited to emphasize formant peaks.
99 citations
TL;DR: The screw piles are made of hollow galvanized iron pipes (dia. 25 mm, 44 mm, 60 mm and length 640 mm and 1000 mm) to which helical plates are welded as mentioned in this paper.
94 citations
TL;DR: In this paper, large amplitude free flexural vibrations of laminated orthotropic plates were studied using C 0 shear flexible QUAD-8 plate element and the nonlinear governing equations were solved using the direct iteration technique.
90 citations
75 citations
TL;DR: This algorithm is guaranteed to give the minimum value of form error and is well-suited for implementation on a computer which may be interfaced with a Coordinate Measuring Machine.
Abstract: ISO defines form error based on the concept of minimum zone, but does not describe the methods to obtain the same. In this paper, drawbacks of the available methods are discussed and a new algorithm is presented. This algorithm is guaranteed to give the minimum value of form error. The algorithm is well-suited for implementation on a computer which may be interfaced with a Coordinate Measuring Machine.
72 citations
TL;DR: In this article, the mean and turbulence characteristics of wall jets generated from orifices having the shapes of various segments of a circle are investigated and the influence of the geometry of the orifice on the various wall jet properties is presented and discussed.
Abstract: This paper reports experimental investigations on mean and turbulence characteristics of three-dimensional, incompressible, isothermal turbulent wall jets generated from orifices having the shapes of various segments of a circle. In Part 1, the mean flow characteristics are presented. The turbulence characteristics are presented in Part 2. The influence of the geometry on the characteristic decay region of the wall jet is brought out and the differences with other shapes are discussed. Mean velocity profiles both in the longitudinal and lateral planes are measured and compared with some of the theoretical profiles. Wall jet expansion rates and behavior of skin-friction are discussed. The influence of the geometry of the orifice on the various wall jet properties is presented and discussed. Particularly the differences between this class of geometry and rectangular geometries are critically discussed.
66 citations
TL;DR: In this article, the breakdown voltage of planar junctions equipped with field plates and guard rings is determined by evaluating the ionization integral using the potential distribution computed by solving Poisson's equation in two-dimensions by a finite difference method.
Abstract: The breakdown voltages of planar junctions (both nonpunchthrough and punchthrough cases) equipped with field plates and guard rings are determined by evaluating the ionization integral using the potential distribution computed by solving Poisson's equation in two-dimensions by a finite difference method. The influence of various parameters, such as substrate doping concentration, n-layer thickness, field oxide thickness, cylindrical junction curvature, field plate width, and the spacing between field plate and guard ring, on the breakdown voltage is extensively studied. It is shown that an optimum value exists for the field oxide thickness to realize maximum breakdown voltage. The study also shows that the optimum oxide thickness depends upon cylindrical junction curvature, substrate doping concentration, and n-layer thickness. It is further shown that the permittivity of a passivant dielectric layer deposited over field plate structure influences the breakdown voltage when breakdown takes place at the field plate edge. The numerical results are compared with the experimental data, and good agreement between the two is observed. Based on this two-dimensional study, design guidelines are provided for achieving breakdown voltages close to maximum realizable values, by conserving the device area and reducing the ionization at the field plant edge. The results presented clearly demonstrate the superiority of the field plate design using punchthrough structures over nonpunchthrough structures in realizing a given breakdown voltage. >
TL;DR: Time-average speckle interferometry has been applied to obtain displacement patterns on the chest wall produced by cardiac action, in the absence of breathing, during various phases of the cardiac cycle and the functional details of the normal heart are outlined.
Abstract: Time-average speckle interferometry has been applied to obtain displacement patterns on the chest wall produced by cardiac action, in the absence of breathing, during various phases of the cardiac cycle. This has been achieved by an electronic shutter, controlled by the electrocardiogram of the subject. The recorded holographic plates processed under identical conditions are scanned by the pointwise method to obtain the absolute displacements at various locations corresponding to the activities of the various cardiac chambers and valves. These data are transformed to a 40*30 matrix by an interpolation method and, from this, three-dimensional displacement plots are reconstructed by an IBM PC/AT computer. These patterns show the displacements over the entire cardiac area corresponding to the activities of various regions during the cardiac cycle. The apex and aortic valve areas show the maximum displacements during the systolic phase. During the diastolic phase the activities over the low-pressure atrial regions are also observed. The results obtained outline the functional details of the normal heart and the activities over various areas are in agreement with those obtained by other noncontact techniques. >
TL;DR: In this article, a higher-order shear deformation theory is presented for the analysis of laminated anisotropic shells of revolution, based on realistic approximation of the in-plane displacements through the thickness.
TL;DR: The feasibility of processing the Fourier transform (FT) phase of a speech signal to derive the smooth log magnitude spectrum corresponding to the vocal tract system is demonstrated and a technique to extract the vocal tracts component of the group delay function is proposed by using the spectral properties of the excitation signal.
TL;DR: In this article, an estimate for the work function of ITO/n-Si and ITO p-Si junctions was obtained from the electrical properties of the silicon surface.
Abstract: An estimate for the work function ― has been obtained from the electrical properties of ITO/n-Si et ITO/p-Si junctions. Since the evaporation method of preparing junctions does not seem to involve any process that may create some kind of charged layer on the silicon surface, the work function estimated seems to be realistic
TL;DR: In this article, the effects of thickness variation on natural frequencies of laminated conical shells have been studied by using a semi-analytical finite element method, where Love's first approximation thin shell theory is used to solve the problem.
TL;DR: A short and straightforward route has been accomplished for the synthesis of C-2-formyl glycals by a Vilsmeier-Haack reaction of glycals.
TL;DR: In this article, various Zeolite catalysed Diels-Alder reactions of cyclopentadiene, cyclohexadiene and furan with less reactive dienophiles were studied.
TL;DR: In this article, five methods of computing reference evapotranspiration from a reference crop (Penman, radiation, Blaney-Criddle, Hargreaves and pan evaporation) have been studied for their applicability under different climatic conditions.
Abstract: Five methods of computing reference evapotranspiration from a reference crop (Penman, radiation, Blaney-Criddle, Hargreaves and pan evaporation) have been studied for their applicability under different climatic conditions. The Penman method was taken as the standard and the other four methods were compared against this method. Good correlation was obtained between the values estimated by the four methods and the Penman method although differences in magnitude were found. Regression equations were developed to correct those differences in magnitude. The method suitable for the estimation of reference evapotranspiration for each climatic condition is also suggested.
TL;DR: In this paper, the decomposition of nitrous oxide was carried out at the initial pressures of 50 and 200 Torr (1 Torr = 133.3 Pa), and two regions of activity were observed based on the mechanism x x ⩽0.5.
TL;DR: In this article, a semi-analytical finite element analysis is presented for determining the natural frequencies of thin circular isotropic cylindrical shells with variable thickness, where Love's first approximation shell theory is used to solve the problem.
TL;DR: In this paper, the Chaotic vibrations of a harmonically excited non-linear oscillator with Coulomb damping are investigated by numerical solution in a range of excitation frequencies.
TL;DR: In this article, a dual field grating has been introduced for use in Talbot interferometry, and the results of an experimental investigation on setting sensitivity when using these gratings for testing are presented.
Abstract: A dual field grating has been introduced for use in Talbot interferometry. We report here results of an experimental investigation on setting sensitivity when using these gratings for testing.
TL;DR: A method for real-time implementation of any two-level three-phase pulse-width-modulator (PWM) invertor waveform is discussed, and the suggested scheme realizes the PWM waveforms without harmonic distortion.
Abstract: A method for real-time implementation of any two-level three-phase pulse-width-modulator (PWM) invertor waveform is discussed. The hardware and software of the scheme are built around the 16 b 8086 microprocessor and its peripherals, with a few additional digital ICs. The suggested scheme realizes the PWM waveforms without harmonic distortion. The implementation procedure is a universal one and it generates in real time any two-level three-phase PWM waveform with the chosen hardware structure. There is no need for hardware alteration for realization of different types of PWM waveforms. >
TL;DR: In this article, X-ray diffraction data and the electrical and optical properties of these thin films as a function of substrate temperature (553 −713 K) were reported and the growth rate of SnO2 films prepared from anhydrous and pentahydrate (SnCl4 ¼ 5H2O) tin chloride as starting material.
TL;DR: In this article, experiments have been carried out on a scale model of stratified hot-water storage tanks to study the effects of operating conditions on the thermoclines and on the extraction efficiency.
TL;DR: In this paper, the authors describe the preparation conditions for stabilizing the bulk superconductivity (T c=9.5 K ) in the nominal Bi 2 Sr 2 CuO ∼ 6 composition corresponding to the n=1 phase in the Bi 2 Ca n−1 Cu n O 2n+4 system.
Abstract: Preparation conditions for stabilizing the bulk superconductivity (T c=9.5 K ) in the nominal Bi 2 Sr 2 CuO ∼ 6 composition corresponding to the n=1 phase in the Bi 2 Sr 2 Ca n−1 Cu n O 2n+4 system are described. The samples Bi 2.1 Sr 1 .9 CuO y and Bi 2.2 Sr 1.8 CuO y become superconducting at 10 K and 12 K, respectively. Single-phase compounds (space group Amaa) could be synthesized for the range 0⩽x⩽1.0 in the series Bi 2 Sr 2−x La x CuO 6+y but the orthorhombicity decreased gradual ly with increase in x and the structure became tetragonal at x=1.0. The T c (R=0) value increased to a maximum of 19 K for x=0.4, corresponding to a value of ∼2.2 for the formal valence of copper. For x⩾0.5 a sudden loss of superconductivity is observed. Simultaneous substitution of Pb for Bi, and, La for Sr yields further improvement in superconducting characteristics, hitting a peak of 26 K (R=0) for x=0.4 in the series Bi 2−x Pb x Sr 2−x R x CuO y (R=La). The R=Nd- and and Pr-s ubstituting compounds showed lower values of T c for the same extent of doping (x=0.4). Interestingly, doping of Pb alone (i.e., Bi 2−x Pb x Sr 2 CuO y ) results in suppression of superconductivity altogether. The electrical resistivity, magnetic susceptibility and the cell parameter data are presented for varying levels of different substituents and discussed.
TL;DR: The fact that weakly triangulated graphs are perfect is used to derive several insightful duality relationships for Class 3Polygon, which is a special type of orthogonal polygon called Class 3 polygon that is a weakly Triangulated graph.
TL;DR: It is shown how this idea can be modified slightly to yield an O ( n = m ) algorithm, and how this algorithm is wrong, and a corrected version of the same is provided.
Abstract: Let G = ( V , E ) be an interval graph , with | V | = n , and | E | = m . An O ( n 2 log n ) algorithm was proposed in Kratsch ( Inform Comput. 74 , 140–158 (1987)) to find the bandwidth of G . We show that this algorithm is wrong, and provide a corrected version of the same. Also, it was observed in [4] that the bandwidth of a proper interval graph can be computed in O ( n log n + m ) time. We show how this idea can be modified slightly to yield an O ( n = m ) algorithm.