Showing papers by "Indian Institute of Technology Bombay published in 1993"
TL;DR: A critical review of literature pertinent to the subject matter of this paper was carried out under the following two broad headings: free vibration and transient dynamics as discussed by the authors, which describes the various theoretical developments in fiber reinforced laminated composite and sandwich plates.
183 citations
TL;DR: In this article, a superconducting transition at 12 K was observed in the system YNi4B (nominal composition: YNi3B), and the possibility of a magnetic phase transition at this temperature was ruled out by specific heat measurements.
150 citations
TL;DR: Four new palladium( II) and platinum(II) complexes of formula [M(dipy)(AA)]+ have been synthesized and characterized with amino acids binding as bidentate ligands and the mode of binding between these complexes and DNA seems to be noncovalent.
53 citations
Abstract: The paper outlines the various problems associated with the drilling of CFRP composites. The technique of dimensional analysis is used to investigate the complex correlation between thrust force, cutting speed, feed, hole diameter, point geometry and material thickness during the drilling of holes in CFRP composites, A new non-dimensional number (t/D), thickness of layered composites to drill diameter, is found to influence the thrust force. Four drill point geometries specifically found effective in drilling of FRP were tried and among them the eight facet drill point geometry was found to give the best results.
44 citations
TL;DR: In this article, the effect of hydration and ion penetration in silicon dioxide has been studied by fabricating metaloxide-semiconductor capacitors on oxide exposed to acidic solutions with and without bias.
39 citations
TL;DR: The OSU Formability Test as discussed by the authors was designed, constructed, and used to evaluate several coated and uncoated sheet materials and showed that the new test is more reproducible, even using relatively uncontrolled equipment, more closely follows the desirable plane-strain path, and takes roughly one fifth of the time to perform relative to LDH.
Abstract: A new test for sheet metal formability was designed, constructed, and used to evaluate several coated and uncoated sheet materials. Results from the OSU Formability Test were also compared with standard limiting dome height (LDH) tests and with finite element simulations. These results show that the new test is more reproducible, even using relatively uncontrolled equipment, more closely follows the desirable plane-strain path, and takes roughly one fifth of the time to perform relative to LDH. Moreover, there is good correlation between formability evaluated using the two tests. Strain measurements and finite element simulations revealed that the improvements are a result of the new test geometry, which produces more stable and repeatable plane-strain states near the fracture location.
35 citations
TL;DR: Cobalt(II) was quantitatively extracted at pH 8.0 with 5 x 10(-3)M Cyanex 272 [Bis(2,4,4 trimethyl pentyl) phosphoric acid] in chloroform by atomic absorption spectrometry as well as by spectrophotometry of the complex with nitroso R salt.
34 citations
TL;DR: In this article, a lead oxide was anodized for various times and at various temperatures in the potential region −1.25 to + 2.35 V (vs. SCE), yielding an approximately 10 μm thick film within 20 min of anodization.
34 citations
TL;DR: In this paper, the reaction of the iron chalcogen carbonyl clusters with various inorganic and organic moieties produces a number of higher nuclearity clusters, and the reactivity pattern of these compounds and the structure of the products formed are discussed.
Abstract: Reaction of the iron chalcogen carbonyl clusters Fe2(CO)6(μ-EE′) and Fe3(CO)9(μ3-E)(μ3-E′), [E=Se, Te;E′=S, Se, Te] with various inorganic and organic moieties produce a number of higher nuclearity clusters. The reactivity pattern of these iron chalcogen carbonyl compounds and the structure of the products formed are discussed.
34 citations
TL;DR: In this paper, carbon molecular sieves were synthesized from bituminous coal and coconut shell and were subjected to steam or carbon dioxide activation in the range 500-900 °C.
26 citations
TL;DR: In this article, three different microstructures, Widmanstatten structure, acicular martensite, and α-plates, have been produced through suitable heat treatments for alloy Ti-6Al-2Sn-4Zr-2Mo (0.1Si).
Abstract: Three different microstructures, Widmanstatten structure, acicular martensite, and α-plates, have been produced through suitable heat treatments for alloy Ti-6Al-2Sn-4Zr-2Mo (0.1Si). The influence of these microstructures on pitting corrosion in 1 M NaBr solution has been studied using polarization technique. It is found that the parameters, pitting potential (Epit) and protection potential (Epp), are significantly influenced by the heat treatment conditions. Epit increases in the order α-plate < Widmanstatten structure < acicular martensite, while in the case of Epp, the value increases in the order Widmanstatten structure < α-plates < acicular martensite. The poor Epp value in the case of Widmanstatten structure is attributed to the inherent variations in Mo and Al content between the plates accompanied by the formation of this phase.
TL;DR: Oxygen isotopic measurements of larger benthic foraminifers from western India suggest that the Palaeogene temperature varied between 22deg;c and 32deg;C in this region as discussed by the authors.
Abstract: Oxygen isotopic measurements of larger benthic foraminifers from western India suggest that the Palaeogene temperature varied between 22deg;C and 32deg;C in this region. The warm climate of the Palaeocene and the Early Eocene, hovering around 32°C, deteriorated in late Middle Eocene (corresponding to planktic zones P13-P14) when the temperature dropped by 6deg;C. With progressive cooling through the Late Eocene, the temperature reached 22deg;C during Early Oligocene times. The cooling trend set in the Middle Eocene seems to have been terminated towards the end of the Palaeogene when the temperature rose to 25°C. □Palaeotemperature, Palaeogene, oxygen isotopes, larger foraminifiers, India.
TL;DR: In this paper, the authors demonstrate the existence of a rich spectrum of collective resonances as a function of the number of shells for n = 1 (C 60 ), 2,10 and 40.
TL;DR: In this paper, a problem of two unequal elliptical holes subjected to internal pressures and shears is solved using the Kolosoff Muskhelishvili stress functions, and the Schwarz alternating method of successive relaxation for multiply connected regions.
Abstract: A problem of two unequal elliptical holes subjected to internal pressures and shears are solved using the Kolosoff Muskhelishvili stress functions, and the Schwarz alternating method of successive relaxation for multiply connected regions
TL;DR: In this article, the effect of mode I and equivalent mixed mode and mode II overload on subsequent mode I crack propagation was studied on compact tension shear specimens of D16AT Al alloy.
TL;DR: In this paper, self-similar solutions for converging spherical and cylindrical strong shock waves in a non-ideal gas satisfying the Mie-Gruneisen type were investigated.
Abstract: The self-similar solutions for converging spherical and cylindrical strong shock waves in a non-ideal gas satisfying the equation of state of the Mie-Gruneisen type are investigated. The equations governing the flow, which are highly non-linear hyperbolic partial differential equations, are first reduced to a Poincare-type ordinary differential equation with suitable approximation. Such an approximation helps in obtaining the self-similar solutions and the similarity exponent numerically by phase-plane analysis.
TL;DR: In this paper, the conditions under which the UMVUE is also a UMMSEUE (uniformly minimum mean squared error unbiased estimator), are investigated, and some examples are also given.
Abstract: In this paper, we obtain some results concerning the UMVUE (uniformly minimum variance unbiased estimator ) of the selected parameter say, for example, the mean. For the squared error loss, the conditions under which the UMVUE is also a UMMSEUE(uniformly minimum mean squared error unbiased estimator), are Investigated, As an application, the UMVUE of θ$sub:I$esub: (or θ$sub:j$esub:), the reciprocal of the natural parameter of the population selected from k independent populations with densities belonging to one parametric continuous exponential family, is also derived. This unifies most of the existing results. The UMVUE of θ$sub:I$esub: is shown to be a UMMSEUE. Some examples are also given.
14 Jul 1993
TL;DR: This paper describes a project in which a vehicle is able to autonomously perform a complete driving mission on selected nonpublic road networks by combining the knowledge of a digital map as supplied by a navigation system with the local actual information about the road gathered from tv cameras.
Abstract: This paper describes a project in which a vehicle is able to autonomously perform a complete driving mission on selected nonpublic road networks. This was accomplished by combining the knowledge of a digital map as supplied by a navigation system (Travelpilot) with the local actual information about the road gathered from tv cameras. The robustness is increased by using a set of three cameras with overlapping viewing range.
TL;DR: In this article, the effect of frequency and load ratio in terms of striation spacing was analyzed at the microscopic scale in order to study the effects of mixed mode crack growth on subsequent mode I fatigue crack propagation.
TL;DR: In this article, the morphological and microstructural changes that occur during mechanical alloying of 7010 aluminum alloy with and without the addition of SiC particulate reinforcement are studied.
Abstract: The process of mechanical alloying (MA), originally developed as a means to produce oxide dispersion strengthened nickel - base superalloys has since been adopted for producing a wide variety of materials such as solid solution alloys, metal matrix composites, intermetallics, amorphous/nanocrystalline materials etc. As far as light metals are concerned the majority of the studies has been on aluminum. Mechanical alloying has been quite successfully employed to produce low density, high strength, high modulus, and high temperature resistant aluminum alloys and composites by incorporation of appropriate alloying elements [Mg, Cu, Li, Tc etc.] and particle reinforcements [SiC[sub p], Al[sub 2]O[sub 3], BN etc.]. The present report is concerned with studies on the morphological and microstructural changes that occur during MA of the elemental powders of 7010 aluminum alloy with and without the addition of SiC particulate reinforcement.
TL;DR: In this paper, experimental and finite element results are presented on mode I and mixed mode (involving I and II only) stable crack growth under static loading through an aircraft grade aluminium alloy (D16AT) in three point bending.
Abstract: Experimental and finite element results are presented on mode I and mixed mode (involving I and II only) stable crack growth under static loading through an aircraft grade aluminium alloy (D16AT) in three point bending. The results include load-displacement diagrams, J-integrals, plastic zones, tunneling (or crack front curving), etc. During experiment a substantial amount of tunneling is observed, the extent of which increases as the extension progresses in both mode I and mixed mode. The tunneling reduces as ao/w increases. The crack extends initially almost along a straight line at an angle with the initial crack in a mixed mode. The maximum load is observed to be as high as 1.6 times the initiation load in the whole range examined. From the finite element study it is seen that, in a mixed mode, the J-integral at the onset of extension is the lowest compared with the values at the later stages. The plastic zone size grows as the stable extension progresses; the growth is approximately the maximum along the crack extension line. The direction of initial crack extension in a mixed mode can be predicted through an elastic finite element analysis and using the criterion of maximum tangential principal stress. The study also indicates that the load-displacement diagram associated with a mixed mode stable crack growth can be predicted reasonably accurately using the criterion of crack opening angle.
01 Nov 1993
TL;DR: In this article, a commercial strontium ferrite target was sputtered onto fused quartz substrates maintained at temperatures up to 900 degrees C. The thin composition corresponded to that of the target and the in-plane and perpendicular hysteresis loops were rectangular with remanence ratios of 0.8 and 0.6.
Abstract: Strontium ferrite films were deposited by RF sputtering of a commercial strontium ferrite target onto fused quartz substrates maintained at temperatures up to 900 degrees C. Films deposited at T 800 degrees C had crystalline M-type strontium ferrite structures. The thin composition corresponded to that of the target. Films deposited at 800 degrees C were partially oriented in the [110] direction with the c-axis in the plane. Postannealing led to an increase in the magnetization, indicating incomplete formation of ferrite in the as-deposited state. Both in-plane and perpendicular hysteresis loops are rectangular with remanence ratios of 0.8 and 0.6, respectively, showing partial orientation with the c-axis. The torque curve is consistent with the above, although there are some additional anomalous peaks. >
TL;DR: It is concluded that the Newmark method with an adequate check on the solution accuracy could give qualitatively the same results as the Runge-Kutta method.
TL;DR: In this article, the authors reported two activation energy (Q) values for superplastic deformation of Zr-2.5 wt% Nb alloy at test temperatures of 600 C and above.
Abstract: The current fabrication route of Zr-2.5 wt% Nb pressure tubes develops a two phase structure of strongly textured, fine, elongated [alpha]-Zr grain and a grain-boundary network of [beta]-Zr phase. This network of [beta]-phase causes the microstructure to be stable even at high temperature, since grain-growth requires long-range diffusion of Nb. Recently three modified fabrication routes have been developed with a view to achieve reduced in-reactor dimensional changes in pressure tubes. During tensile testing of specimens machined from a Zr-2.5 wt% Nb pressure tube, manufactured by a fabrication route, broadly similar to the modified route-2, large elongations (> 100%) were obtained at test temperatures of 600 C and above. these observations indicated the possible occurrence of superplasticity in this alloy during high temperature deformation. Nuttall reported two activation energy (Q) values for superplastic deformation of Zr-2.5 wt% Nb alloy. The higher value can be matched with that for lattice diffusion in [alpha]-Zr at relatively lower temperature, whereas the lower value is comparable with the activation energy for lattice diffusion in [beta]-Zr at higher temperature. The abnormality in the observed values of Q in Zr-2.5 wt% Nb alloy was attributed to the variation in strain-rate sensitivity, composition and volume fraction of [alpha]more » and [beta]-phases with temperatures. Further studies on superplasticity in Zr-2.5 wt% Nb alloy was thus felt necessary and led to the present investigation.« less
TL;DR: In this article, the Galerkin method with cubic B-splines as basis functions has been extended to two-dimensional problems, for the Dirichlet type boundary conditions, resulting in a non-homogeneous part in the approximation.
TL;DR: In this paper, the search behavior of the genetic algorithm has been modeled in a Markovian framework and strong convergence proved, and the limiting analysis of the algorithm reveals the vital interplay of the randomized operators.
Abstract: Genetic algorithms are stochastic search procedures based on randomized operators such as crossover and mutation. Many of the earlier works that have attempted to analyse the behaviour of genetic algorithms have marginalized the role of these operators through gross abstractions. In this paper, we place in perspective these operators within the genetic search strategy. Certain important properties of these operators have been brought out through simple formalisms. The search behaviour of the genetic algorithm has been modeled in a Markovian framework and strong convergence proved. The limiting analysis of the algorithm reveals the vital interplay of the randomized operators.
18 Aug 1993
TL;DR: Polarization phase difference (PPD) and polarization index (PI) images were generated using P-, L- and C-bands polarimetric AIRSAR data collected over Mahantango watershed area in Central Pennsylvania during July 1990.
Abstract: Polarization phase difference (PPD) and polarization index (PI) images were generated using P-, L- and C-bands polarimetric AIRSAR data collected over Mahantango watershed area in Central Pennsylvania during July 1990. Three corn fields were identified in the image for detailed analysis. The mean PPD for corn fields is found to be increasing with increasing wavelength. The vegetation index involving cross and like polarization is better than the vegetation index with only like polarizations. >
TL;DR: The results conclusively proved the applicability of the new steroidal proxyl nitroxide (SPN) as a potential spin probe for spin labeling studies.
TL;DR: From the analysis of the data, it is concluded that Sm ions at one site are in the trivalent state and those at the second site are either divalent or weakly valence fluctuating.
Abstract: T. Fukuhara, I. Sakamoto, and H. Sato [J. Phys.: Condens. Matter 3, 8917 (1991)] reported valence fluctuations of Sm ions in ${\mathrm{SmRuSn}}_{3}$, which orders antiferromagnetically at 6 K. We have carried out x-ray, microprobe, heat-capacity, susceptibility, and resistivity measurements on a sample of nearly the same stoichiometry. There are two inequivalent Sm sites in ${\mathrm{SmRuSn}}_{3}$ and from the analysis of our data we conclude that Sm ions at one site are in the trivalent state and those at the second site are either divalent or weakly valence fluctuating.
TL;DR: In this paper, a study of NiCrAl-base alloys in air and air containing 1% sulphur dioxide at 1000°C was carried out and the alloys used were in the cast, forged and single-crystalline form.
Abstract: Oxidation studies have been carried out on NiCrAl-base alloys in air and air containing 1% sulphur dioxide at 1000°C. The alloys used were in the cast, forged and single-crystalline form. There was considerable difference in the oxidation behavior of the as-cast alloy and that of forged alloy, when the environment contained sulphur dioxide. In the absence of the latter, the behavior of the two alloys was not very different. The oxidation behavior of the single crystals was also very similar to that of the cast and forged alloys, when the atmosphere was oxidizing. A few single-crystalline alloys, however, underwent catastrophic oxidation when about 1% sulphur dioxide gas was present, in a manner similar to that of the cast alloy. Oxidation tests at 1000°C as well as detailed scale analysis indicated that the different microstructure, especially large difference in grain size was probably the main reason for the large difference in their oxidation behavior.