1. Journal Articles
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/1/6
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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 Use of inclined compound triangular notch-weir to improve discharge range(2009) Shivapur, A.V.; Mulangi, R.H.; Govardhan, Swamy, H.S.The notch-weir having simple geometric shapes is unable to measure small as well as occasional large flows. In such situation compound weirs find application. In the present paper authors have reported their study on the use inclined compound notch-weir consisting of two triangular sections with different vertex angles. The notch plane is placed inclined to the general flow surface in the channel. The general discharge equation has been evolved through the semi analytical cum experimental procedure. Results show a significant improvement in discharging rate compared to normal weir. The lower triangular portion of the notch-weir handles the smaller flow whereas the upper part helps to measures the occasional high flows. Further advantages of the inclined compound weir in reducing afflux near the structure are also discussed. � 2009 Taylor & Francis Group, LLC.Item Unslotted multichannel channel-access protocol for distributed direct-sequence networks(2004) Raghavan, A.R.; Baum, C.W.A multichannel reservation-based channel-access protocol is investigated in this paper. The available system bandwidth is divided into distinct frequency channels. Under the protocol, one channel (the control channel) is used to exchange reservation messages and the remaining channels (the traffic channels) are used for information-bearing traffic. The performance of this scheme is compared to that of a single-channel reservation-based protocol. A simple contention-based slotted-Aloha protocol is also considered. Performance results take into account the effects of multiple-access interference on acquisition and packet errors. Results show that the reservation-based approach is advantageous under conditions of high traffic. In addition, a pacing mechanism that mitigates multiple-access interference and promotes fairness is described, and results are presented that demonstrate its effectiveness.Item Ultrafast nonlinear optical properties of dye-doped PMMA discs irradiated by 40 fs laser pulses(2009) Xia, Y.; Jiang, Y.; Fan, R.; Dong, Z.; Zhao, W.; Chen, D.; Umesh, G.The two-photon absorption (TPA) characteristics of PMMA discs doped with three different dyes were studied using an fs-pulsed Ti-Sapphire laser as the pump source, and employing the open-aperture Z-scan technique. TPA cross-sections obtained for PMMA doped with the dyes PM597, DCM and rhodamine 6G-rhodamine B (co-doped) were found to be equal to 24.7, 33.3 and 32.3 GM, respectively (1 GM=10-50 cm4 s phot-1 mol-1). Furthermore, two-photon fluorescence was measured for the samples containing DCM and rhodamine 6G-rhodamine B (co-doped). Compared to the one-photon fluorescence spectrum, the peaks in the two-photon fluorescence spectrum were red shifted and the extent of red shift increased with increasing doping concentration. We have also observed that the red shift in the two-photon fluorescence peak of the samples in the solid form is much larger than that in the solution state. This phenomenon could be explained by a twisted intra-molecular charge transfer model. � 2009 Elsevier Ltd. All rights reserved.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 Transition metals supported on activated carbon as benzene hydroxylation catalysts(2005) Choi, J.-S.; Kim, T.-H.; Choo, K.-Y.; Sung, J.-S.; Saidutta, M.B.; Song, S.-D.; Rhee, Y.-W.The direct conversion of benzene to phenol by hydroxylation with hydrogen peroxide was carried out over catalyst containing various transition metals impregnated on activated carbon. Iron and vanadium impregnated catalysts gave better yields of phenol compared to copper impregnated catalysts. The activity of transition metals supported on activated carbon catalyst in the production of phenol was V > Fe > Cu. In addition to the role of transition metals in catalyzing the hydroxylation reaction, the hydrophobic nature of the activated carbon surface and also the surface acidity and basicity seems to have enhanced the performance of these catalysts. � 2005 Springer Science + Business Media, Inc.Item ?(3) measurements and optical limiting in dibenzylideneacetone and its derivatives(2006) Kiran, A.J.; Chandrasekharan, K.; Nooji, S.R.; Shashikala, H.D.; Umesh, G.; Kalluraya, B.We investigated the third order nonlinear optical properties of dibenzylidene acetone (1,5-diphenyl-1, 4-pentadeine-3-one) and its derivatives. The nonlinear measurements were performed by using single beam Z-scan technique with Q-switched Nd:YAG nanosecond laser pulses at 532 nm. Open aperture data for dibenzylidene and its derivatives demonstrate the presence of two-photon absorption at this wavelength. The dependence of ?(3) on donor/acceptor type substituents to the basic compound clearly shows the electronic origin of nonlinearity and hence demonstrates that the mechanism by which the third order nonlinear response enhanced is not by the thermal effects, but instead due to the strong nonlinear absorption and nonlinear refraction of the compounds. The derivatives of the basic compound show very good optical limiting behavior. � 2005 Elsevier B.V. All rights reserved.Item Widely programmable high-frequency active RC filters in CMOS technology(2009) Laxminidhi, T.; Prasadu, V.; Pavan, S.We propose a circuit technique that enables the realization of widely programmable high-frequency active RC filters in CMOS technology. A fifth-order Chebyshev ladder filter having a digitally programmable 3-dB bandwidth (from 44 to 300 MHz) is used as a vehicle to validate our ideas. The opamp uses feedforward compensation for achieving high dc gain and wide bandwidth. The integrating resistors are realized as a series combination of a triode-operated MOSFET and a fixed polysilicon resistor. A charge-pump-based servo loop servoes the integrating resistor to a stable off-chip resistor. The principle of "constant capacitance scaling"is applied to the opamp and the integrating resistors so that the shape of the frequency response is maintained when the bandwidth is scaled over a 7 7times; range. The filter core, designed in a 0.18-?m CMOS process, consumes 54 mW from 1.8-V supply and has a dynamic range of 56.6 dB. � 2009 IEEE.Item Wave transmission and reflection for two rows of perforated hollow piles(2002) Rao, S.; Shirlal, K.G.; Rao, N.B.S.A laboratory investigation on perforated hollow piles in two rows was conducted in a two dimensional regular wave flume to study the wave transmission and reflection characteristics. The influence of incident wave steepness, relative clear spacing between the piles and rows of piles on transmission co-efficient and reflection co-efficient have been investigated. The effect of staggering of piles in the rows on both transmission and reflection co-efficients was also studied. The present study has revealed that for perforated pile groups incident wave steepness, relative clear spacing between the piles, relative clear spacing between the rows of piles influence both transmission and reflection co-efficients. Staggering of piles reduces reflection from the perforated piles. Perforated piles have smaller transmission and reflection co-efficient values compared to that of non-perforated piles at lower wave steepness.