Conference Papers
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Item Inverse modeling of heat transfer with application to solidification and quenching(2002) Prabhu, K.N.; Ashish, A.A.The inverse modeling of heat transfer involves the estimation of boundary conditions from the knowledge of thermal history inside a heat conducting body. Inverse analysis is extremely useful in modeling of contact heat transfer at interfaces of engineering surface during materials processing. In the present work, the one-dimensional transient heat conduction equation was inversely modeled in both cartesian as well as cylindrical coordinates. The model is capable of estimating heat flux transients, chill surface temperature, and total heat flow from the source to the sink for an input of thermal history inside the sink. The methodology was adopted to solve boundary heat transfer problems inversely during solidification and quenching. The response of the inverse solution to measured sensor data was studied by carrying out numerical experiments involving the use of varying grid size and time steps, future temperatures, and regularization techniques.Item Identification of voice disorders using speech samples(2003) Nayak, J.; Subbanna Bhat, P.This paper attempts to identify pathological disorders of larynx using Wavelet Analysis. Speech samples carry symptoms of disorder in the place of their origin. The speech signal is subjected to wavelet analysis, and the coefficients are used to identify disorders such as Vocal Fold Paralysis. Multilayer Artificial Neural Network is used for classification of normal and affected signals.Item Simulation study of Borda's profile & parallel plane electrode to assess electric field uniformity(Institute of Electrical and Electronics Engineers Inc., 2003) Punekar, G.S.; Thejovathi, G.; Kishor, N.K.The electrode gaps which results in to uniform electric fields are the most widely used gap configurations in assessing dielectric strength. In the present study simulation results of two electrode gap configurations namely, parallel plane profile and Borda's profile are reported. The charge simulation method (CSM) is used to compute electric fields with errors in simulation being less than 0.04% (in potential). In order to assess the uniformity in electric field in the gap, numerical experiments are conducted by varying parameters like gap spacing, overall radius. Computed electric fields on the surface of the electrode help in comparing non-uniformity in electric fields for the two electrode configurations. Simulation results indicate that for the same overall dimension of the electrode and the gap spacing, parallel plane electrode gives lower non-uniformity factor when compared to the Borda's profile is that the maximum field on the electrode occurs at the edge of the electrode, which is away from the region of interest. Where as the maximum field in case of a plane electrode occurs at the edge of the linear portion of plane profile. Also looking at the field distribution along the gap axis indicates that Borda's profile yields more uniform fields. © 2003 Society of EMC Engineers.Item Performance and emission studies on the effect of injection timing and diesel replacement on a 4-S LPG-Diesel Dual-Fuel Engine(SAE International, 2003) Sudhir, C.V.; Desai, V.; Kumar, S.Y.; Mohanan, P.Reducing the emissions and fuel consumption are no longer future goals; instead they are the demands of the day. People are concerned about rising fuel costs and effects of emissions on the environment. Diesel engines are the major contributors to the increased levels of pollutants. In the present work an attempt is made for effective utilization of diesel engine with reduced fuel consumption, smoke density and NOx emissions. This is achieved by some minor modifications in diesel engine so as to run it as LPG-Diesel Dual-fuel engine with LPG (Liquefied Petroleum Gas) (70% Butane + 30% Propane) induction at air intake. The important aspect of LPG-Diesel dual-fuel engine is that, it shows significant reduction in smoke density, NOx emission and improved brake thermal efficiency with reduced energy consumption. An existing 4-S, single cylinder, naturally aspirated, water-cooled, direct injection, C.I. engine test rig was used for the experimental purpose. With proper instrumentation the tests were conducted under various LPG flow rates, loads, and injection timings. The influence of the diesel replacement by LPG on smoke density, brake specific energy consumption and brake thermal efficiency was studied. The optimal diesel replacement pertaining to the maximum allowable LPG flow limits could be assessed with these experiments. The influence of the injection timing variation on the engine performance and smoke density was analyzed form the experimental results. It was observed that beyond half load operation of the dual-fuel engine, thermal efficiency increased with diesel replacement, and at full load up to 4% improvement was observed compared to full diesel operation. There was drastic reduction in NOx emissions (up to40- 60 %) for the entire load range, except near full load where NOx increased (by38%) beyond full diesel value at normal injection timing. At full load reduction in smoke density up to 40% to 60% was observed compared to full diesel operation. At advance injection timing of 30°btdc the performance of the dual fuel engine was better with lower smoke density, while the NOx emission was found to be higher. Copyright © 2003 SAE International.Item Intelligent approach for efficient operation of electrical distribution automation systems(2003) Manjunatha Sharma, K.; Sreedhar, P.N.The distribution systems play a vital role in making efficient service in terms of power quality, reliability, and economy. The distribution network reconfiguration can be used for planning as well as real time control. This paper presents an efficient approach for network reconfiguration approach based on artificial neural networks. A package "DISTFLOW" is developed adopting the proposed technique. The off-line simulation results and daily load curve data are used for training of the neural network. Further the distribution system operation is optimized by selecting optimum compensation level computed by Genetic Algorithms (G.A). The proposed integrated approach is applied to 140 bus practical system of Surathkal city subdivision, of the power utility Mangalore electricity supply company (MESCOM).Item Estimation of evolutionary spectrum based on STFT and modified group delay(2003) Narasimhan, S.V.; Pavanalatha, S.This paper proposes a new estimator for Evolutionary Spectrum (ES) based on short time Fourier transform (STFT) and modified group delay (MGD). Here, the STFT enables crossterm suppression and the MGD preserves the frequency resolution of the rectangular window. It is applicable to deterministic and random signals generated by time varying systems. The proposed method provides signal to noise ratio enhancement due to the use of MGD. The results indicate that for linear chirp signals and for time varying random process, its frequency resolution is close to that of WVD and better than Evolutionary periodogram (EP) and STFT. Further, its noise immunity is better than those of EP and STFT.Item Computation of lightning induced voltages on telecommunication subscriber lines(Institute of Electrical and Electronics Engineers Inc., 2002) Kannu, P.D.; Thomas, M.J.The electric and magnetic fields produced by a lightning stroke in the vicinity of a telecommunication line can illuminate the line and it can acquire induced overvoltages which may be detrimental to the equipments connected to the telecommunication line. The magnitude and waveshape of the electromagnetic fields produced by lightning as well as the induced voltage on telecommunication line are influenced by the finite conductivity of the ground. In this paper, the induced transient voltages on an overhead telecommunication subscriber line due to a nearby lightning stroke to the ground are computed. From the results it is seen that the induced voltage is bipolar for all the observation points except at the line midpoint for the lightning striking point location chosen in this study. It is also observed that the finite ground conductivity decreases the magnitude of the induced voltage at the line terminations where as it increases the induced voltage as the line mid point is approached. The results obtained in this study will be useful in evolving a suitable lightning protection scheme for the rural telephone exchanges which are interconnected using overhead lines instead of underground cables as in the case of urban exchanges. At the same time these rural telephone exchanges have become more vulnerable to transient overvoltages as they are being converted into digital ones with their susceptibility levels for transient overvoltages being much lower than the old electromechanical exchanges. © 2001 Convenor.Item Studies on esters of coconut oil as fuel for LPG-Biodiesel dual fuel engine(American Society of Mechanical Engineers Three Park Avenue New York NY 10016-5990, 2003) Kapilan, N.; Reddy, R.P.; Mohanan, P.The rapid depletion in world petroleum reserves and uncertainty in petroleum supply due to political and economical reasons, as well as, the sharp escalation in the petroleum prices, have stimulated the search for alternatives to petroleum based fuels specially diesel and gasoline. Biodiesel is one of the renewable fuels, which will be the good replacement to diesel. But as a sole fuel, it gives poor performance and higher emissions. From the literature survey, it is observed that not much work has been done to use Methyl Ester (ME) of coconut oil as liquid fuel in sole and dual fuel mode of operation. Hence, in the present work, ME of coconut oil is chosen as a sole fuel to run the diesel engine and an alternative pilot fuel to run LPG-Biodiesel dual fuel engine. In dual fuel mode operation, LPG is used as the inducted gaseous fuel. LPG has been chosen as the inducted fuel on account of its easy availability in abundance in the present time. The existing compression ignition diesel engine was modified to work on dual fuel mode. Tests were carried out on a single cylinder, four strokes, water-cooled, direct injection, compression ignition engine using ME of coconut oil as fuel. To study the effect of injection timing, its is advanced and retarded from the standard injection timing recommended for diesel operation. From the results, it is observed that the advanced injection timing results in better performance and lower emissions of the diesel engine. In dual fuel mode operation, first the engine was started with ME of coconut oil as fuel and then the LPG flow rate was increased. With appropriate proportions of the injected (0.45, 0.65 and 0.75 kg/hr) and inducted fuels it is possible to improve the engine performance and reduce its emissions. From the experimental results, it is found that the pilot fuel rate of 0.65 kg/hr is preferred from the point view of brake thermal efficiency, fuel consumption and smooth running. ME of coconut oil were successfully used as sole fuel and pilot fuel. The performance and emission of the engine in sole fuel mode with better injection timing and dual fuel mode with better pilot quantity were compared. From the comparison, it is observed that the ME of coconut oil can be used as pilot fuel in dual fuel engine compared to sole fuel with regard to performance and emissions.Item Computation of radiated electromagnetic fields from a lightning return stroke(Institute of Electrical and Electronics Engineers Inc., 2003) Kannu, P.D.; Thomas, M.J.This paper presents the computed electric fields produced by a lightning return stroke. It is observed that the rate of rise of lightning current does not influence the vertical component of electric field. The negative pre-pulse magnitude of the horizontal electric field increases with time derivative of the lightning current where as the initial negative peak of the horizontal electric field increases in direct proportion to the return stroke velocity. © 2003 Society of EMC Engineers.Item An analytical model for intersystem handover(Institute of Electrical and Electronics Engineers Inc., 2003) Singh, B.; Aggarwal, K.K.; Kumar, S.Universal Mobile Telecommunication Systems (UMTS) shall be developed in such a way that it will support compatibility with an evolved Global System for Mobile Communications (GSM). In this paper, we investigate intersystem handover between GSM and UMTS based on Wideband Code Division Multiple Access (WCDMA) air-interface. A mathematical model is proposed to evaluate the handover performance. The handover initiation algorithm is based on the absolute value of averaged signal strength thresholds. Average number of handovers and handover initiation delay are used as performance measures. Based on numerical results, it is observed that handover initiation algorithm based on absolute thresholds induces large number of handovers near the cell boundary. Finally, threshold levels are optimized for given system parameters.