Showing papers by "Indian Institute of Technology Bombay published in 1990"
TL;DR: A historical management system (HDBMS) is described which uses an extended relational data model with state-oriented, instead of 'cubic', conceptualization, and retains the elegant structural and algebraic framework of SQL.
Abstract: A historical management system (HDBMS) is described which uses an extended relational data model with state-oriented, instead of 'cubic', conceptualization. Two types of historical relations, called state and event relations, are provided for modeling real-world objects. The query language SQL has been extended for definition, retrieval, and update of historical relations. The extended SQL, called HSQL, is a superset of SQL. The author defines a few primitive algebra operations for historical relations, and uses them as a basis for extensions to SQL. In this way, HSQL retains the elegant structural and algebraic framework of SQL. HSQL contains a few new clauses, many operations and built-in functions on time domain, and facilities for retrospective updates and time-rollback. >
129 citations
23 Apr 1990
TL;DR: Whether the local gray value variation can be exploited in the temporal as well as in the spatial domain in order to achieve further improvements at discontinuities in the optical flow field associated with the image areas of moving objects in image sequences is studied.
Abstract: Recent experimental results by Schnorr 89 with an approach based on a simplified ‘oriented smoothness constraint’ show considerable improvement at expected discontinuities of the optical flow field. It thus appears justified to study whether the local gray value variation can be exploited in the temporal as well as in the spatial domain in order to achieve further improvements at discontinuities in the optical flow field associated with the image areas of moving objects in image sequences. An extension of the oriented smoothness constraint into the temporal domain is presented. In this context, a local estimation approach for the spatio-temporal partial derivatives of optical flow has been developed. This, in turn, is used to compare two approaches for the definition of optical flow.
110 citations
TL;DR: In this paper, the authors have identified the most suitable method of mix design for RAC, from amongst the available conventional methods for mix design, and an empirical relation is suggested to modify the influencing parameter.
73 citations
TL;DR: Khilar et al. as discussed by the authors proposed a critical value of the total ionic strength (CTIS) for mixed salt solutions flowing in porous media, which is defined as the difference between critical flocculation concentration (CFC) and the present definition of CTIS.
65 citations
TL;DR: By numerically solving the Navier-Stokes and energy equations in their three-dimensional parabolic form, the friction and heat transfer characteristics are predicted for laminar flow in a circular tube fitted with regularly spaced twisted-tape elements that are connected by circular rods as mentioned in this paper.
63 citations
23 Apr 1990
TL;DR: The encouraging results show how obstacles can be detected in image sequences taken from a translating camea by evaluation of optical flow vectors estimated with independently developed approaches.
Abstract: The approach discussed in this contribution is an example for the interpretation of temporal variations in image sequences recorded by a translating camera. The encouraging results show how obstacles can be detected in image sequences taken from a translating camea by evaluation of optical flow vectors estimated with independently developed approaches. Further developments are necessary to extend the approach to more general motion and more complex environments.
60 citations
TL;DR: The compound Ru4(CO)11(µ4-Te)2 (1) has been prepared by refluxing a benzene solution containing Fe3(CO), 9( µ3-Te), Ru3( CO)12 (2) was obtained from the reaction of 1 with Ph2PCH2PCh2PPh2 at room temperature as mentioned in this paper, and the structure of 1-4 were established by single-crystal X-ray diffraction analysis.
Abstract: The compound Ru4(CO)11(µ4-Te)2 (1) has been prepared by refluxing a benzene solution containing Fe3(CO)9(µ3-Te)2 and Ru3(CO)12 The compounds Ru3(CO)6(PPh3)3(µ3-Te)2 (2) and Ru4(CO)10(PPh3) (µ4-Te)2 (3) were obtained from the room temperature reaction of 1 with PPh3 Similarly, Ru4(CO)9 (µ - Ph2PCH2PPh2) (µ4 –Te)2 (4) was obtained from the reaction of 1 with Ph2PCH2PPh2 at room temperature The structure of 1-4 were established by single-crystal X-ray diffraction analysis Crystal data: 1, orthorhombic, Pccn, a = 6924 (2) A, b = 16289 (6) A, c = 18054 (6) A, V = 2036 (1) A3, Z = 4, R(F) = 416%; 2, monoclinic P21/ n, a = 10539 (4) A, b = 2739 (1) A, c = 20415 (7) A, β = 9496 (3)°, V = 5870 (4) A3 , Z = 4, R(F)= 496%; 3, orthorhombic, Pbca, a = 19070 (5) A, b = 18157 (4) A, c = 19272 (5) A, V = 6673 (3) A3, Z = 8, R(F) = 365%; 4, triclinic, PĪ, a = 13255 (3) A, b = 17610 (5) A, c = 19189 (5) A, α = 6539 (2)°, β= 7825 (2)°, у = 8413 (2)°, V = 3986 (2) A3, Z = 4, R(F) = 297%
58 citations
TL;DR: In this paper, the authors present an analysis involving fabric spacer material, considering the heat transfer by various modes such as solid conduction, conduction through contact surfaces, radiation through an exposed area between adjacent shields and radiation through the fibrous spacer.
58 citations
TL;DR: A practical system for performing optimal instruction selection based on tree pattern matching for expression trees and its ability to perform code generation without requiring cost analysis at code generation time is proposed.
44 citations
TL;DR: In this article, the authors presented experimental results on mode I and mixed mode stable crack growth under static loadings through an aluminium alloy (D16AT) for both the sets of tests.
44 citations
TL;DR: In this paper, the axial momentum equation for flow in a tube containing regularly spaced twisted-tape elements has been integrated to yield a correlation for friction factor that reflects the influences of secondary flows and wall shear.
TL;DR: A series of complexes of the type [Pt(phen)(AA)]+ inhibit the intercalation of ethidium bromide in DNA by intercalativebinding at low concentrations and show nonintercalative binding at higher concentrations.
TL;DR: The magnetic susceptibility measurements were performed on CuO before and after quenching from high temperature as discussed by the authors, and it was argued that the large rise in the magnetization at temperatures much below the Neel temperature observed in certain samples may not be of impurity origin.
TL;DR: In this article, a cell model has been proposed to predict the enhancement of gas absorption rates into slurries containing catalyst particles which are smaller than liquid diffusion flim thickness, which accounts for interparticle and particle-film interactions.
TL;DR: The OPS5PLUS expert system shell was used to represent the procedural knowledge to reason and extract both the internal and external part features and their dimensions in order to select form tools for machining.
Abstract: This article reports on the design and implementation of an expert system for automatic identification of machined surfaces on symmetric rotational components manufactured on Automats. The OPS5PLUS expert system shell was used to represent the procedural knowledge to reason and extract both the internal and external part features and their dimensions in order to select form tools for machining. Details ofthe implementation are described, along with examples. The expert system can be integrated easily with other manufacturing applications, such as automated process planning and NC part programming.
TL;DR: In this paper, a bicontinuous double-diamond (OBDD) was shown to occur as a cubic phase between the cylindrical and lamellar morphologies.
Abstract: Diblock copolymer macromolecules may be viewed as giant amphiphiles. Such molecules readily self-assemble into a wide variety of structures which exhibit intermaterial dividing surfaces of approximately constant mean curvature. Order-disorder transitions in bulk materials result in ordered microdomain structures of BCC spheres, hexagonally packed cylinders and stacked lamella. An additional structure, the ordered bicontinuous double-diamond (OBDD) is also shown to occur as a cubic phase between the cylindrical and lamellar morphologies. The interface structure of the OBDD resembles a recently discovered family of constant mean curvature surfaces which include the Schwarz D minimal surface. Another interface structure which approximates Scherk's First Surface is a 90 twist boundary between grains of lamella. Blending of diblock copolymer with homopolymer provides a versatile binary system which displays a critical micelle concentration, spherical and cylindrical micelles, lamellar vesicles as well as ordering transitions depending on composition. The penetration of homopolymer into one side of the near-interface region accounts for the observed variations in interface curvature in blends from that of the pure diblock. Confining geometries, such as external surfaces, thin films and microdroplets can influence interface structures. Chaotic bicontinuous as well as parallel surface structures such as concentric spherical shells are shown to occur in microdroplets of a diblock copolymer which forms lamellar microdomains in the bulk.
TL;DR: In this paper, a 3-noded triangular two singular points finite element is proposed to model two variable order singularities lying at close proximities as in the case of a kinked crack.
Abstract: A 3-noded triangular two singular points finite element is proposed to model two variable order singularities lying at close proximities as in the case of a kinked crack. The element meets the rigid body mode and the interelement compatibility of the convergence criteria. A degenerate form of the element is a one point variable order singularity element, which meets all the convergence requirements. A number of kinked crack problems have been analysed using the new element and its degenerate form. The computed results are compared with analytical solutions. The accuracy of the results is found to be good.
TL;DR: In this article, a COD-based criterion has been used to predict the load-displacement diagram from initiation to instability in a mixed-mode stable crack growth under static loadings through an aluminium alloy.
15 Oct 1990
TL;DR: In this article, the authors studied the stability of aqueous foams with polymer additives at temperatures ranging from 30 to 80°C and found that the enhancement of stability due to the addition of water-soluble polymer additives as reported by D. Sarma, J. Pandit, and K. C. Khilar is substantially retained, although it is reduced at higher temperatures.
Abstract: The stability of aqueous foams with polymer additives has been studied at temperatures ranging from 30 to 80°C. It is found that the enhancement of stability due to the addition of water-soluble polymer additives as reported by D. S. H. S. Sarma, J. Pandit, and K. C. Khilar (J. Colloid Interface Sci. 124, 339 (1988)) is substantially retained, although it is reduced at higher temperatures. In the case where cosurfactant is the only additive, the enhancement of stability is entirely lost at about 70°C. It is also found that the decrease in drainage half-life and the increase in initial drainage rate are gradual with the increase in temperature, without any indication of sudden transition. The modified lamella drainage analysis is extended and used to qualitatively describe this effect. The experimental data and the analytical results are used to discern the importance of interfacial mobility in the variation of stability with temperature.
TL;DR: In this paper, solid solutions of magnesium ferrite and magnesium titanate are prepared by ceramic technique from α-Fe2O3, TiO2, and magnesium oxalate by heating at high temperature followed by quenching or by slow cooling.
Abstract: Solid solutions of magnesium ferrite and magnesium titanate are prepared by ceramic technique from α-Fe2O3, TiO2, and magnesium oxalate by heating at high temperature followed by quenching or by slow cooling. The compounds crystallise in monophasic cubic spinel structure. The compounds are studied for their initial susceptibility, magnetic hysteresis, and Mossbauer spectral parameters. All these properties are explained as due to the dilution effect of the nonmagnetic ion that changes the particles to single domains.
Feste Losungen von Magnesiumferrit und Magnesiumtitanat werden mittels keramischer Technik aus α-Fe2O3, TiO2 und Magnesiumoxalat durch Erhitzen bei hohen Temperaturen und nachfolgendem Abschrecken oder langsamem Abkuhlen hergestellt. Die Verbindungen kristallisieren in der einphasigen kubischen Spinellstruktur. Die Verbindungen werden hinsichtlich ihrer Anfangssuszeptibilitat, magnetische Hysterese und Mosbauerspektralparameter untersucht. Alle diese Eigenschaften werden mit dem Verdunnungseffekt des nichtmagnetischen Ions erklart, das die Partikel zu einzelnen Domanen andert.
TL;DR: In this paper, the approximate energy release rate for a crack which extends, or "kinks" away from its original direction has been computed by finite element analysis using three different methods: stiffness derivative procedure, J integral method and crack closure integral procedure.
Abstract: The approximate energy release rate for a crack which extends, or “kinks”, away from its original direction has been computed by finite element analysis using three different methods: stiffness derivative procedure, J integral method and crack closure integral procedure. A case study is presented to compare the computational accuracies. It suggests that a satisfactory approximation can be obtained provided that the ratio of kink length to original crack length, l(0)/a⩽0.04, despite the interaction of the crack tip and knee stress singularities.
TL;DR: In this article, the design of robust nonlinear feedback controller is analyzed for a trajectory tracking in a single-input single-output nonlinear state variable system x = f(x + g(x)u, y=cx which arises in nonlinear chemical processes particularly in batch reactor control problems.
Abstract: The design of robust nonlinear feedback controller is analysed for a trajectory tracking in a single-input single-output nonlinear state variable system x = f(x) + g(x)u, y=cx which arises in nonlinear chemical processes particularly in batch reactor control problems. Simulation results for the batch reactor temperature tracking problem show the effectiveness of the control scheme and its robustness to modelling errors. The method is also applicable to multi-input multi-output system where the number of inputs is equal to that of outputs. The controller design is also analyzed for situations wrier: the kinetics, the activation energy and Ihe heat of reaction are unknown and also only limited measurement of state-variables are available. The method of Youcef-Toumi and Ito (1987) is applied to such problems and the effectiveness of control system is shown by simulation.
TL;DR: In this article, a covolume dependent mixing rule for the energy parameter enables the prediction of solubility of solids in supercritical fluids, which avoids the use of difficult-to-obtain critical properties and acentric factors.
Abstract: Inclusion of a covolume dependent mixing rule for the energy parameter enables the prediction of solubility of solids in supercritical fluids. This approach avoids the use of difficult-to-obtain critical properties and acentric factors and involves simple characteristic properties, namely the van der Waals volume and the heat of sublimation of the solid. These properties are predicted using the molecular structure and the Bondi's group contribution method. The predictions of solubilities by the proposed model, including those not employed in the development of the model, are found to be in good agreement with the experimental data on solubilities of a range of solids in supercritical carbon dioxide, ethane, and ethylene.
TL;DR: In this paper, the peak-to-peak ferromagnetic resonance (FMR) linewidth was shown to be linearly proportional to the volume fraction of the crystalline phase formed during annealing in ferromagnetostrictive cobalt-based glasses.
Abstract: It has been shown theoretically that the peak-to-peak ferromagnetic resonance (FMR) line-width (ΔHpp) should be proportional to the volume fraction (f) of the crystalline phase formed during annealing in ferromagnetic glasses. However, in the case of zero-magnetostrictive cobalt-based glasses (γ=0), ΔHpp should remain constant due to very low values of anisotropy. In Co68Fe4Mo1Si17B10 glass (γ=0), ΔHpp has been found to remain unaffected upon progressive crystallization. In Fe65Cr8B27 glass, ΔHpp has been found to be linearly proportional tof. Using this dependence, the activation energy of crystallization (Ea) has been calculated. The value ofEa obtained from the FMR technique (248 kJ mol−1) agrees quite well with those from DTA studies using Kissinger's or Ozawa's technique.
TL;DR: Incorporation of the edge placement technique in a register assignment algorithm is shown to enhance the profitability of optimisation, and reduce the complexity of the bi-directional data flows.
TL;DR: In this article, the transformation of C 8 aromatics has been studied on platinum, palladium and nickel, each supported on ZSM-5 zeolite, and it was shown that as low as 0.02% platinum is sufficient to obtain good C8 aromatics conversion.
TL;DR: In this article, the hydrogenation of cottonseed oil has been carried out in a batch reactor using both unmodified and chromia modified nickel catalysts, and the optimum content in the catalyst was found to be 0.17 Cr/Ni atomic ratio; the data corresponded to 5 hr reaction time.
Abstract: The hydrogenation of cottonseed oil has been carried out in a batch reactor using both unmodified and chromia modified nickel catalysts. The process variables include chromium to nickel atomic ratio (0.00–0.35), catalyst particle size (200–400 micron), temperature (120–140°C) and pressure (5–10 bar). Chromia was found to suppress the stearate formation completely, although it retarded the overall hydrogenation activity of nickel. Its optimum content in the catalyst was found to be 0.17 Cr/Ni atomic ratio; the data corresponded to 5 hr reaction time. The kinetics of the process was tested and found to follow a first order reaction with respect to linoleate and half order with respect to hydrogen. The activation energy was found to be 11.8 kcal/mole.
TL;DR: In this article, the conformation of the hormone bradykinin in DMSO-d6 was investigated using proton NMR spectroscopy at 500 MHz using 2D COSY and NOESY techniques.
Abstract: The conformation of the hormone bradykinin (Arg–Pro–Pro–Gly–Phe–Ser–Pro–Phe–Arg) in DMSO-d6 was investigated using proton NMR spectroscopy at 500 MHz. Complete resonance assignments were made using 2D COSY and NOESY techniques. The chemical shifts, magnitudes of the 3JNH-CαH couplings, temperature coefficient data on backbone NH protons and intramolecular NOEs were used to obtain information on the conformation. The nonapeptide assumes a rigid structure in DMSO-d6. Based on the experimental results, a model is proposed using computer-aided molecular graphics.