1. Journal Articles
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Item Aqueous corrosion behaviour of ductile iron and ductile iron containing 1 wt. pct. chromium(1997) Surendranathan A.O.; Hebbar, K.R.; Sudhaker Nayak, H.V.Ductile irons with graphite in spheroidal form enjoy the processing characteristics of grey iron and mechanical properties of steel. This paper describes the corrosion behaviour of ductile iron containing 1 wt. % chromium in sea water, dilute sulphuric acid and dilute sodium hydroxide solutions and compares with that of unalloyed ductile iron. Study is made in as-cast, annealed and cold worked (upto 28% reduction in thickness) conditions at three different temperatures. Since the alloying addition brings changes in the proportion of phases, the corrosion behaviour of the two materials studied were different, though alloying addition is small, indicating corrosion behaviour to be structure sensitive.Item Use of mining and seismological parameters as premonitors of rockbursts(1997) Srinivasan, C.; Arora, S.K.; Yaji, R.K.Comprising one of the deepest mines in the world, the gold mining region of the Kolar Gold Fields (KGF) in southern India is known to be confronted with the acute problem of rockbursts that pose a hazard to workmen and cause disruptions in the production schedule. In combination with mining parameters, seismological data of these rockbursts events systematically monitored over the years using a regional seismic network have been employed to examine and model premonitory characteristics of the events. Linear empirical relations are established relying on correlations seen between the seismic energy released due to a rockburst, total tonnage of ore mined out and total number of rockbursts, as well as seismic events in some shallow and deep workings currently active at KGF. The deterministic model, although not free from certain limitations at present, has been applied to predict rockburst activity with some success. � 1997 Elsevier Science Ltd.Item TWO-STAGE SEQUENTIALLY OPERATED REGENERATIVE CONVERTERS WITH CONTROLLED FLYWHEELING.(1985) Bhat, Subbanna, P.; Dubey, Gopal, K.Separately excited dc motors fed by sequentially operated multistage converters are commonly used in mainline traction. The drive performance can be greatly improved by operating the fully controlled converters with controlled flywheeling. The analysis and performance of a dc drive fed by two-stage sequentially operated fully controlled converters with controlled flywheeling are described. The modes of operation of the converter system are identified, and a method for calculating performance, taking these modes of operation into account, is presented. The nomograms and an analytical method of calculating them are presented for computing the optimum value of filter inductance. The performance of the drive with controlled flywheeling is compared with performance using normal control. The modes of operation and certain aspects of drive performance are verified experimentally.Item Topological energy-function analysis of stability of power systems(1987) Padiyar, K.R.; Sastry, H.S.Y.In this paper the direct stability evaluation of power systems, with voltage-dependent loads, using topological energy function is given with applications. This is based on the philosophy of a structure-preserving model for power systems. The loads are modelled as arbitrary functions of respectively bus voltages. A classical model is assumed for generators and system equations are formed using centre of angle (COA) reference. A topological energy function is developed and applied for the stability evaluation using the potential-energy boundary surface (PEBS) method. Examples of a 4-machine and a 7-machine system are considered for illustration. The critical clearing time (Tcr) is obtained both by digital simulation and by the direct method for various load characteristics and for different fault locations. � 1987.Item Transportation of granite statues(1989) Basavarajaiah, B.S.This paper deals with the problems faced during the transportation of two large granite monolith statues weighing 180 t and 120 t respectively through the narrow and winding country-roads on the western plains of the state of Karnataka. A brief resume of the problems faced during this operation and how these were overcome successfully have been presented.Item Wood burning cook stoves(1989) Nijaguna, B.T.; Uppin, S.B.The major domestic energy needs of people in the under-developed and developing countries are met by burning wood in cook stoves. The quest for energy conservation and its efficient use has motivated researchers the world over to look for improvements in wood burning cook stoves. Even a marginal increase in efficiency can contribute considerably to a total saving in energy consumption and therefore conservation. Analysis of cooking using wood shows that better energy efficiency can be achieved by complete and controlled combustion of wood, maximum energy transfer to food cooked and reducing the energy losses. The various component design features that contribute to better utilisation of wood energy are discussed. These can be of use in emerging designs, or in the modifications to the existing designs. In addition to dealing with the sizing factors, the rating or performance testing of wood stoves is detailed, thus providing a basis for comparison of different stoves. Operational guidelines that contribute to increased efficiency during cooking are provided.Item WAVE FORCE COEFFICIENTS ON SUBMARINE PIPELINES - AN OVERVIEW.(1984) Pranesh, M.R.; Somanatha, G.S.The use of submarine pipelines for economical and safe transportation of hydrocarbons is inevitable. As the applicability of pipelines are extended to other purposes, pipeline mileage is increasing alarmingly and into more hostile environment. Since wave force on submarine pipelines is identified to be a major force estimation of wave forces is of vital importance for design purposes. In this paper, an attempt has been made to identify possible reasons for discrepancies in the results of hydrodynamic coefficients. Various experimental results of wave forces on pipelines in newly constructed 2 m wide wave flume are also compared with the results available in literature. Based on the analysis, hydrodynamic coefficients to be used in the design are suggested.Item Wave attenuation characteristics of single row of perforated hollow piles in laboratory(1999) Subba, Rao; Rao, N.B.S.; Prasad, J.S.Laboratory investigation on perforated hollow piles in a single row was conducted in a two dimensional regular wave flume to study the performance of such an arrangement in dissipating wave energy. The influence of spacing between the piles, size of perforations, different percentage of perforations and water depth on wave attenuation has been investigated. It is found that water depth has insignificant effect on transmission coefficient (K(t)) at higher wave steepness. K(t) decreases as the relative clear spacing of piles (b/D) decreases and also it decreases as the incident wave steepness increases. At lower value of b/D, K(t) decreases with increase in percentage of perforations. For the same percentage of perforations, the pile groups with larger size of perforations transmit more wave energy than pile groups with smaller size of perforations. The perforated hollow pile breakwater is an alternative solution to protect the coast from erosion where the erosion is due to wave energy concentration or onshore offshore movement of sand.Item Variable-feedrate CNC interpolators for constant material removal rates along Pythagorean-hodograph curves(1998) Farouki, R.T.; Manjunathaiah, J.; Nicholas, D.; Yuan, G.-F.; Jee, S.An NC system that machines a curved shape at fixed depth of cut experiences time-varying cutting forces due to the 'curvature effect' - the material removal rate is higher than nominal in concave regions, and lower in convex regions. A curvature-dependent feedrate function that automatically compensates for this effect is formulated, and it is shown that, for Pythagorean-hodograph (PH) curves, the periodic real time computation of reference points in accordance with this function can be analytically reduced to a sequence of root-finding problems for simple monotone functions. Empirical results from an implementation of this variable-feedrate interpolators on an open-architecture CNC milling machine are presented and compared with results from fixed-feedrate interpolators. The curvature-compensated feedrate scheme has important potential applications in ensuring part accuracy and in optimizing part programs consistent with a prescribed accuracy. � 1998 Elsevier Science Ltd. All rights reserved.Item THREE-PHASE REGENERATIVE CONVERTER WITH CONTROLLED FLYWHEELING.(1985) Bhat, Subbanna, P.; Dubey, Gopal, K.The low-speed performance of a dc drive can be improved by operating the three-phase fully controlled bridge converter with controlled flywheeling. The analysis and performance of the drive with controlled flywheeling is described. The modes of operation of the converter system are identified, and a method for calculating performance, taking these modes of operation into account, is presented. Nomograms and an analytical method of calculating them are presented for computing the optimum value of the filter inductance. The performance of the drive with controlled flywheeling is compared with performance using conventional control. The modes of operation and certain aspects of drive performance are verified experimentally.