Showing papers by "Indian Institute of Technology Bombay published in 1995"
TL;DR: In this paper, a correlation was developed to predict the influence of ash on volatile yield, initial decomposition temperature and rate of pyrolysis in wood and twelve other types of biomass.
762 citations
TL;DR: In this article, the Iosipescu shear test was used to evaluate the inplane shear strength of fiber angle test specimens and a model for predicting the cutting forces and the dependence of cutting direction on machinability requirements was presented.
Abstract: With the increasing use of fiber reinforced plastic (FRP) composites outside the defense, space and aerospace industries, namely, civilian industries, machining of these materials is assuming a significant role. Unit cost rather than solely performance at any cost will be the consideration for the implementation of FRP composites to consumer industries. The current knowledge of machining FRP composites, unfortunately, is inadequate for its optimum utilization in many applications. This paper presents some observations made on the orthogonal machining of unidirectional carbon fiber reinforced plastic (UD-CFRP) laminates with different fiber orientations. Iosipescu shear test was adopted to evaluate the inplane shear strength of varied fiber angle test specimens. A model for predicting the cutting forces and the dependence of cutting direction on machinability requirements is presented.
306 citations
TL;DR: In this article, tensile specimens of Type 316L stainless steel having grain sizes in the range 3.1-86.7 μm were deformed to 34% strain at temperatures 24, 400 and 700°C and strain rate 1 × 10−4s−1 to investigate the Hall-Petch (H-P) relationship, the nature of stress-strain curves and the substructure development.
Abstract: Tensile specimens of Type 316L stainless steel having grain sizes in the range 3.1–86.7 μm were deformed to 34% strain at temperatures 24, 400 and 700°C and strain rate 1 × 10−4s−1 to investigate the Hall-Petch (H-P) relationship, the nature of stress-strain curves and the substructure development. Upto ∼5% strain the H-P relationship exhibits bi-linearity whereas the single Hall-Petch relation is exhibited at larger strains. The presence of bi-linearity is explained by the back stress associated with the difference in the dislocation densities in the vicinity of grain boundary and in the grain interior. The log stress (σ)-log strain (e) plots depict three regimes and follow the relationship σ = Ken in each regime, but with varying magnitudes of the strength coefficient (K) and strain-hardening exponent (n).
187 citations
TL;DR: A normalized correlation method is used for the preparation of montages when there is no rotational shift between neighboring images, and a pyramidal approach is developed to reduce the computation.
86 citations
TL;DR: In this paper, the degradation mechanism of starch-filled LDPE strips was characterized using a single screw Brabender extruder and various laboratory tests (starch hydrolysis by α-amylase at 95 °C, thermal oxidation in an air oven at 80 °C and exposure to 254 nm UV radiation).
84 citations
TL;DR: Results of the resistivity, magnetic, and specific-heat data clearly suggest coexistence of superconductivity and magnetism (of Er spins) in ErNi 2 B 2 C (T c ≊10.5 K) below ≊7 K.
Abstract: Discovery of a quaternary superconducting system Y-Ni-B-C has been reported recently. Our structural studies on ${\mathrm{YNi}}_{2}$${\mathrm{B}}_{2}$C (${\mathit{T}}_{\mathit{c}}$\ensuremath{\approxeq}15.5 K) reveal large and anisotropic thermal vibrations of C atoms in the Y-C plane of the structure. No crystallographic phase transition is observed down to 50 K. Our specific-heat data suggest that ${\mathrm{YNi}}_{2}$${\mathrm{B}}_{2}$C is a strong-coupling superconductor. Results of our resistivity, magnetic, and specific-heat data clearly suggest coexistence of superconductivity and magnetism (of Er spins) in ${\mathrm{ErNi}}_{2}$${\mathrm{B}}_{2}$C (${\mathit{T}}_{\mathit{c}}$\ensuremath{\approxeq}10.5 K) below \ensuremath{\approxeq}7 K.
82 citations
TL;DR: Using the tensor calculus representation, the Taylor expansion of the gray-value derivatives as well as of the optical flow in a spatiotemporal neighborhood is built by providing a unifying framework for all existing local differential approaches and allows to derive new systems of equations for the estimation of the Optical flow and of its derivatives.
77 citations
TL;DR: In this paper, the authors use the Lie group invariance to determine the class of self-similar solutions to a problem concerning plane and radially symmetric flows of a relaxing gas involving shocks of arbitrary strength.
61 citations
TL;DR: In this article, a combined field and laboratory study has been made on chromite-bearing oxidized serpentinite rocks of Sukinda in Orissa, India, which indicated the possibility of chromium mobilization from the chromite ores into the waterbodies.
Abstract: Among the dominant species of chromium, the trivalent form widely occurs in nature in chromite ores or in silicate minerals and is extremely immobile. The higher oxidation state Cr(VI), is, however, rarely found in nature, is more mobile, and several times more toxic than Cr(III). Cr(VI) occurs in chromates and dichromates manufactured from chromite ores. The hexavalent state is stable in an oxidizing alkaline environment, whereas the trivalent state is stable in a reducing acidic environment. Serpentinization and Mg release during deuteric alteration of ultramafic rocks create alkaline pore water and lateritization is an intensive oxidation process. Chromite ore bodies in oxidized serpentinite therefore may generate hexavalent chromium from the inert chromites and cause hazardous chromium pollution of the water. With this end in view, a combined field and laboratory study has been made on chromite-bearing oxidized serpentinite rocks of Sukinda in Orissa, India. Laboratory leaching studies on mine overburden samples, chemical analyses of streamwater, and hydrolysate incrustation on detrital grains taken from stream beds have indicated the possibility of chromium mobilization from the chromite ores into the waterbodies.
53 citations
TL;DR: In this paper, a statistical thermodynamic theory for hydrogen-bonding interactions between polymeric gels and solvents is developed, which is shown to provide quantitative predictions of swelling behavior of poly(ethylene oxide) gels in chloroform and water and qualitative predictions of thermoreversible volume transitions of poly (N-isopropyl acrylamide) (PNIPA) gel in water.
47 citations
TL;DR: This equipment provides an experimental platform for studying driver-vehicle interactions with the option to automatically evaluate actual traffic situations around the vehicle in real-time and offers an approach to record and disentangle the multitude of factors which influence the often subconscious-reactions of a driver.
TL;DR: In this article, a detailed analysis of the dielectric properties and phases present coupled with micro-structural detail indicate that the second phase in the grain boundary has a pronounced effect on the surface properties and not the pyrochlore phase.
Abstract: Stoichiometric and 2 wt. % excess lead oxide containing lead magnesium niobate (PMN) ceramics have been prepared by partial oxalate route. Dielectric measurements with frequency showed a typical relaxor behavior for stoichiometric PMN, while PMN with excess PbO shows a scatter in the dielectric curves at all temperatures above Tc. Under the same processing conditions, the dielectric constant (Kmax) decreases drastically from 16,300 to 9500 at 1 KHz for PMN without and with excess PbO, respectively. Microstructure studies revealed a second phase (unreacted PbO) segregated in the grain boundaries for excess PbO samples. A careful analysis of the data on dielectric properties and phases present coupled with microstructural detail indicate that the second phase in the grain boundary has a pronounced effect on the dielectric properties and not the pyrochlore phase.
TL;DR: An LQG/H/sub /spl infin// controller synthesis is presented for a flexible one-link manipulator with noncolocated sensing and is found to satisfy both performance and stability requirements.
Abstract: An LQG/H/sub /spl infin// controller synthesis is presented for a flexible one-link manipulator with noncolocated sensing. The challenge of the problem lies in the nonminimum phase characteristics and the ill-conditioned nature of the plant. The inner-loop LQG controller provides adequate damping to the flexible modes and numerically conditions the system while the outer-loop H/sub /spl infin// controller provides stability in the face of unstructured perturbation. With only tip position sensing and using a fourth-order model, a controller is synthesized. It is tested with an eighth-order model of the plant and is found to satisfy both performance and stability requirements.
TL;DR: The primary advantage of genetic algorithms, viz. the generalized search operators, enables easy combinations of these global search algorithms with local search heuristics to provide an efficient hybrid algorithm for the mapping problem without compromising the solution quality.
TL;DR: In this article, the Fischer-Tropsch synthesis of lower hydrocarbons on silicalite-1 supported cobalt and cobalt-manganese catalysts was reported.
Abstract: Fischer-Tropsch synthesis of lower hydrocarbons on silicalite-1 supported cobalt and cobalt-manganese catalysts is reported. The catalysts were prepared by impregnating the calcined support with the corresponding metal nitrate solutions. Co 3 O 4 was found to be the only phase present in the manganese free catalyst, while addition of manganese favoured the formation of the mixed spinel (Co 1− x Mn x ) 3 O 4 phase. Addition of manganese decreased the reduction temperature of Co 3 O 4 and also presumably reduced its particle size. The catalysts showed good activity and selectivity for light hydrocarbons in the C 2 –C 4 range, particularly propene and also showed very low water gas shift activity. Addition of manganese increased CO conversion rate at 250°C. The alkene selectivity of the Co/Sil catalyst decreased slightly by the addition of manganese.
TL;DR: It is shown that while differential receivers exhibit a far lower crosstalk than single-ended ones, it is possible to obtain low crosStalk values in the latter case by means of suitable power supply decoupling.
Abstract: This paper presents an analysis as well as experimental results on developing receiver arrays for parallel digital datalinks for 10-100 m in the Gb/s range. Interchannel crosstalk can be a dominant limiting factor on the bit-error-rate in such parallel arrays. We present a novel analysis of the physical origins of crosstalk arising from the power-supply distribution, as well as an efficient circuit simulation technique for the effect of crosstalk on digital signal transmission in multichannel systems. It is shown that while differential receivers exhibit a far lower crosstalk than single-ended ones, it is possible to obtain low crosstalk values in the latter case by means of suitable power supply decoupling. Experimental results in the form of two low crosstalk multichannel receiver arrays are presented to corroborate the theory. >
TL;DR: Fluorescence quenching and CD studies indicated the membrane-bound conformation of apo-α-LA was some conformational state that is between the soluble, fully folded conformation and the molten globule state.
Abstract: The insertion of soluble proteins into membranes has been a topic of considerable interest. We have studied the insertion of bovine alpha-lactalbumin into single-bilayer vesicles prepared from egg phosphatidylcholine (PC). Fluorescence studies indicated rapid and tight binding of apo-alpha-lactalbumin (apo-alpha-LA) to PC vesicles as a function of pH. The binding was maximal at pH values which favor the formation of the molten globule state. As an increase of hydrophobic surface is observed in the molten globule state, this conformational state can provide a molecular basis for insertion of soluble proteins into membranes. The membrane-bound complex formed at low pH (3.0) could be isolated and was found to be stable at neutral pH. The structural characterization of the apo-alpha-LA-PC complex was studied by fluorescence quenching using iodide, acrylamide, and 9,10-dibromostearic acid. The results obtained indicated that some of the tryptophans of apo-alpha-LA were buried in the membrane interior and some were exposed on the outer side. Fluorescence quenching and CD studies indicated the membrane-bound conformation of apo-alpha-LA was some conformational state that is between the soluble, fully folded conformation and the molten globule state.
TL;DR: Various considerations and the steps in the development of ANN for the design expert system are illustrated with an example of optimal design of RC beams.
TL;DR: In this paper, a kaizen system was designed and installed in a large manufacturing organization as a part of a TQM exercise and detailed studies were carried out by collecting extensive data over a period of 23 months, and by using statistical methods to understand the dynamics in the kaizen process.
Abstract: A kaizen system was designed and installed in a large manufacturing organization as a part of a TQM exercise. Detailed studies were carried out by collecting extensive data over a period of 23 months, and by using statistical methods to understand the dynamics in the kaizen process. The kaizen process was found to be an auto regressive process, which leads to habit formation in making improvements. The process was observed to be influenced by seven controllable variables, which affect the quantity and quality of improvements. Reveals that implementation of kaizen as the first step in the TQM journey can lead to a self‐sustaining, controllable process of setting up a culture of continuous improvement.
TL;DR: In this paper, an elastic-plastic finite element scheme based on the small deformation theory of incremental plasticity has been proposed for stable crack growth in mixed mode through doubly stiffened and unstiffened compact tension (CT) specimens of D16AT aluminium alloy.
TL;DR: In this article, specific heat capacities, apparent molar heat capacity, densities, and evident molar volumes have been determined for cytosine, uracil, thymine, adenine, cytidine, 2′-deoxycytidine, uridine, thymidine and adenosine at temperatures from 25°C to 55°C.
Abstract: Specific heat capacities, apparent molar heat capacities, densities, and apparent molar volumes have been determined for cytosine, uracil, thymine, adenine, cytidine, 2′-deoxycytidine, uridine, thymidine and adenosine at temperatures from 25°C to 55°C. The results of these measurements have been used to calculate for the first time, the thermodynamic quantities:C
p,2
o
, (∂C
p,2
o
/∂T)p, (∂2
C
p,2
o
∂T
2)p,V
2
o
, (∂V
2
o
/∂T)p, and (∂2
V
2
o
/∂T
2)p. The-CH2-group contribution has been calculated at different temperatures. It has also been observed from the data for the nucleic acid bases and nucleosides that the additivity ruleC
p,2
o
(nucleoside)-C
p,2
o
(base) +C
p,2
o
(water)=C
p,2
o
(ribose) does not hold in these cases.
TL;DR: The chemical composition of Tattapani thermal springs, together with the experimental results on host rock-meteoric water interaction at 100°C, indicate dissolution of K-feldspars and albite during the initial stages of reaction as discussed by the authors.
TL;DR: In this paper, a new fracture initiation criterion is proposed, which is based on the results obtained by Theocaris and Andrianopoulos [Engng Fracture Mech. 16, 425-432 (1982)] for the case of uniaxial, biaxonial and shear loading at infinity.
TL;DR: In this article, an elastic-plastic finite element scheme based on the small deformation theory of incremental plasticity has been used to study stable crack growth in mixed mode through three point bend (TPB) specimens of D16AT aluminium alloy.
18 Jun 1995
TL;DR: In this article, the concept of tunable dual and triple band microstrip antennas with nearly quarter wavelength monolithic stubs loaded at the radiating edges of the rectangular or square patch was proposed.
Abstract: Dual band printed microstrip antennas using single layer and multilayer patches have been reported. Triple band performance has been reported for a square patch antenna using a spurline filter and the perturbation technique. This paper proposes the concept of tunable dual and triple band microstrip antennas with nearly quarter wavelength monolithic stubs loaded at the radiating edges of the rectangular or square patch.
TL;DR: In this article, an annular geometry analysis of a gas-fluidized bed of glass beads is carried out using an ANNular geometry model and it is shown that the fluidized bed behaves like a Bingham plastic.
23 Oct 1995
TL;DR: This work proposes a method that, instead of analyzing an image region in isolation, uses a block shift-variant interactive blur model to account for the interaction among neighboring subimages.
Abstract: The recovery of depth from defocus involves calculating the depth of various points in a scene by modeling the effect that the focal parameters of the camera have on images acquired with a small depth of field. We propose a method that, instead of analyzing an image region in isolation, uses a block shift-variant interactive blur model to account for the interaction among neighboring subimages. Simulation results are presented on the performance of the model.
TL;DR: In this paper, stable crack growth through three-point bend (TPB) and stiffened and unstiffened compact tension (CT) specimens of D16AT aluminium alloy has been studied both theoretically and experimentally.
Abstract: The stable crack growth through three-point bend (TPB) and stiffened and unstiffened compact tension (CT) specimens of D16AT aluminium alloy has been studied both theoretically and experimentally. The specimen thickness is 8 mm. The variation of load with crack opening displacement, the extent of stable crack growth, the cumulative plastically deformed zone and crack edge profiles have been obtained experimentally. These are also predicted theoretically under the assumption of either a state of plane stress or plane strain using a finite element scheme and the COA criterion. Generally, the experimental results agree well with the predictions based on the plane stress condition. There appears to be no significant variation in size of the experimental cumulative plastic zone across the specimen thickness, thereby indicating that the constraint on the plastic zone does not develop near the mid-thickness region.
01 May 1995-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, the effect of various welding parameters, e.g., the welding current, the wire radius etc., on the weld bead penetration characteristics has been investigated, and the occurrence or nonoccurrence of finger penetration, routinely found in the GMA welding at high welding currents, has been satisfactorily explained by the cylindrical heat source model.
Abstract: In the modeling of the gas metal-arc (GMA) welding process, heat inputs to the workpiece by the arc and the metal transfers have been considered separately. The heat energy delivered due to the metal transfer has been approximated in the form of a cylindrical volumetric heat source, whose dimensions of the radius and the height are dependent on the molten metal droplet characteristics. The pinch instability theory (PIT) and the static force balance theory (SFBT) of drop detachment have independently been used to obtain the expressions for various characteristics of the drop,i.e., the drop radius, the drop velocity, and the drop frequency at various welding parameters. The occurrence or the nonoccurrence of finger penetration, routinely found in the GMA welding at high welding currents, has been satisfactorily explained by the cylindrical heat source model. The effect of various welding parameters,e.g., the welding current, the wire radiusetc., on the weld bead penetration characteristics has been investigated. In this modeling effort, the heat conduction equation has been solved in three dimensions.