1. Journal Articles
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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 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.Item The effect of the thickness of the porous material on the parallel plate channel flow when the walls are provided with non-erodible porous lining(1976) Channabasappa, M.N.; Umapathy, K.G.; Nayak, I.V.Flow through a channel whose walls are lined with non-erodible porous material is investigated using Beavers and Joseph slip boundary condition. It is shown that the effect of porous lining is to increase the mass flow rate and to decrease the friction factor. 1976 Martinus Nijhoff Publishers.Item Systems analysis of tank irrigation: II. delayed start and water deficit(1989) Prasad, R.; Mayya, S.G.Tank irrigation systems in the semiarid regions of India are discussed in this paper. To optimize the grain yield of rice, it is essential to start the agricultural operations in the second week of July so that favorable climatic conditions will prevail during flowering and yield formation stages. Because of low inflow during the initial few weeks of the crop season, often farmers are forced to delay planting until sufficient sowing rain and inflow have occurred or to adopt deficit irrigation during this period. The delayed start affects the grain yield, but will lead to an improved irrigation efficiency. A delayed start of agricultural operations with increased irrigation efficiency leads to the energy resources becoming critical during the peak requirement week, particularly those of female labor and animal power. This necessitates augmenting these resources during weeks of their peak use, either by reorganizing the traditional methods of cultivation or by importing from outside the system. ASCE.Item Systems analysis of tank irrigation: I. crop staggering(1989) Mayya, S.G.; Prasad, R.The irrigation potential of a tank system, thousands of which are found in South India, depends upon a number of factors other than water availability. These factors are mainly influenced by the agricultural technology adopted, food practices of people and livestock, the interdependence of land-human-livestock components of life, and socioeconomic practices prevailing in rural areas. The system needs to pertain not only to grain yield but also to fodder production. In semiarid regions of India, uneven distribution and insufficient rainfall during the initial crop season develops water stress in plants. Relatively higher irrigation efficiency, which is possible to attain in tank systems, leads to an increase in the energy resources required for various agricultural operations. An attempt is made in this paper to investigate the effect of these factors on the optimal use of irrigation potential of a minor irrigation tank system. The method involves developing a linear programming (LP) model to optimize the net profit from the system and to determine the optimal cropping pattern under the influence of various parameters, e.g., animal power, labor, fodder production, the resources of farmers, and the nutritional energy requirement of the system, in addition to water availability. The crucial nature of these factors as well as the irrigation efficiency is analyzed. The solution reveals the effectiveness of prevailing agricultural practices consistent with the availability of water resources in the initial crop season. ASCE.Item Switched digital video access networks(1996) Bankapur, R.J.; Beuscher, H.J.; Runyon, J.P.; Sanku, A.C.R.; Sehgal, C.S.Telecommunications service providers are upgrading their network infrastructure to enhance telephony and to enable future video and data services. This discussion focuses on an access network that serves as a platform for transporting telephony and asynchronous transfer mode (ATM) data to the customer premises using fiber-in-the-loop (FITL) technology. The platform provides the building blocks that will enable service providers to furnish a wide variety of offerings, such as interactive and broadcast video, Internet access, and other high-bandwidth data communications. The platform is called the switched digital video (SDV) access network. This paper describes the SDV access network, and it also presents an example of how SDV network elements could be configured with other broadband network elements to provide an interactive video services network.