Veljko Papic
University of Belgrade
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Featured researches published by Veljko Papic.
IEEE Transactions on Instrumentation and Measurement | 2007
Irini Reljin; Branimir Reljin; Veljko Papic
The window class, which is generated by multiple time-convolution of weighted-cosine windows, is presented. It is shown that after a convolution of known parent windows, the resultant convoluted (CON) window exhibits high side-lobe attenuation that is capable of suppressing long-range leakage. Moreover, using the expressions describing an error due to the short-range leakage, the optimization procedure was applied to adjust the coefficients of parent windows in order to obtain, as flat as possible, the main lobe of the CON window. As a result, the new window class having both an extremely flat-top (EFT) main lobe and high side-lobe attenuation was generated. Moreover, new windows exhibit faster decaying side lobes than parent windows. The efficiency of EFT windows in high-accuracy harmonic analysis was demonstrated through computer simulations
mediterranean electrotechnical conference | 1998
Irini Reljin; Branimir Reljin; Veljko Papic; P. Kostic
The new window class, generated by the time convolution of well-known classic windows, is presented. By multiple auto-convolution of windows it is possible to obtain both flat-top and high sidelobe attenuation, making new windows very suitable for harmonic amplitude evaluation in the nonsynchronous sampling case (i.e. when noninteger number of cycles lies in the interval of analysis). The expressions describing an error caused by spectral leakage are derived. The new window class is tested on the periodic signal with known harmonic contents. The results obtained confirm the applicability of new windows in the analysis of the periodic signal waveforms.
international conference on industrial technology | 2012
Predrag Tadic; Zeljko Durovic; Branko Kovačević; Veljko Papic
A method for diagnosing faults in steam separators is presented. Faults in the water level, water flow and steam flow sensors are analyzed. Precise models of the steam separator system are difficult to obtain, which makes the most common model-based fault detection and isolation approaches unapplicable. An identification-based method is used instead: parameters of the process are identified in real time, and the resulting data samples, which we denote as residuals, are used as inputs to a CUSUM-type classification scheme. It then decides if a fault is present, and if so, which one. In other words, residuals are first generated by parameter identification, and then evaluated by a modification of the CUSUM test. The choice of the CUSUM algorithm was motivated by its optimality with respect to detection delay. The identified parameters are assumed to be normally distributed. This assumption is experimentally verified: the true probability density functions (PDF) are estimated, and the performance of the detector based on these estimated PDFs is compared to that of the previous detector, based on the Gaussian PDF. The proposed method was tested on real-world data, obtained from the TEKO B1 Unit of the Kostolac Thermal Power Plant in Serbia. The results suggest extremely low probabilities of false alarm, missed detection and false isolation. As for detection delay, just one residual sample is needed for proper fault diagnosis in some cases, while 83 samples are needed in the worst-case scenario.
Journal of Physics: Conference Series | 2014
Aleksandra Marjanovic; M Krstic; Zeljko Djurovic; Goran Kvascev; Veljko Papic
Quality regulation of the combustion process inside the furnace is the basis of high demands for increasing robustness, safety and efficiency of thermal power plants. The paper considers the possibility of spatial temperature distribution control inside the boiler, based on the correction of distribution of coal over the mills. Such control system ensures the maintenance of the flame focus away from the walls of the boiler, and thus preserves the equipment and reduces the possibility of ash slugging. At the same time, uniform heat dissipation over mills enhances the energy efficiency of the boiler, while reducing the pollution of the system. A constrained multivariable extremum seeking algorithm is proposed as a tool for combustion process optimization with the main objective of centralizing the flame in the furnace. Simulations are conducted on a model corresponding to the 350MW boiler of the Nikola Tesla Power Plant, in Obrenovac, Serbia.
mediterranean electrotechnical conference | 2010
Veljko Papic; Zeljko Djurovic; Goran Kvascev; Predrag Tadic
A new simple algorithm for estimating signal-to-noise ratio (SNR) for a signal consisting of one sinusoid in white Gaussian noise is proposed in this paper. Algorithm is based on autocorrelation and modified covariance methods for AR (Autoregressive) spectral estimation. The validity of the algorithm is examined by comparing its SNR estimate with SNR estimate obtained by sinusoid magnitude estimation using Pisarenko harmonic decomposition method and noise variance estimation using modified covariance method. By a large number of simulations this algorithm has proven itself as a comparably precise even in case of significantly noise-contaminated sinusoidal signal.
telecommunications forum | 2016
Jelena Krmar; Veljko Papic
Recognition of humans based on characteristic eye features has taken a significant place in security and identification systems in the past two decades. The complex pattern of the iris, that is unique to an eye, makes iris a great biometric descriptor. The first step in the process of the biometric identification based on iris is its localization in an image. The shape of the iris, its size, position, shades from the light sources and eyelashes make this process difficult. It is reported that most failures to match in iris recognition system result from inaccurate segmentation. This paper will analyze statistical characteristics of iris texture with an attempt to improve the process of segmentation.
telecommunications forum | 2011
Veljko Papic; Zeljko Durovic; Goran Kvascev; Predrag Tadic
This paper presents one way to adaptation of Doppler radar filters. Doppler filters use window function in order to estimate the target velocity. The window function length can be adapted depending on estimated target acceleration and estimated signal to noise ratio in the system. Kalman filter is used for estimation of target acceleration. Signal to noise ratio is estimated using a procedure based on parametric methods of spectral analysis. A new adaptive Doppler-Kalman structure has been presented and efficiency of approach to target velocity estimation is proven by computer simulations.
mediterranean electrotechnical conference | 2010
Veljko Papic; Ruben Puche-Panadero; Predrag Todorov; Zeljko Djurovic
In this paper a new approach for obtaining the coal quality classification is proposed. The main goal is to classify the coal into three classes: “good”, “medium” and “bad” coal based on its calorific value. Instead of having chemical analysis the classification is obtained by using only two electrical signals available from SCADA system, which are the speed of the belt feeder and the current of the mill motor. Two parameters of the cross-correlation function between these signals with mean values of these two signals from SCADA are used to form training set patterns for designing a classifier. The procedure of classifying the coal characterizing pattern has been introduced.
IFAC Proceedings Volumes | 2010
Predrag Tadic; Željko M. Durović; Goran Kvascev; Veljko Papic
Abstract An application of a fixed-size sample (FSS) hypothesis testing algorithm to the problem of detecting shortages in the coal supply subsystems of thermal power plants is presented. Blockage of coal supply leads to the occurrence of possibly hazardous operating conditions; it is therefore treated as a fault, and its detection is posed as a fault detection and isolation (FDI) problem. Physical variables of interest are treated as stochastic processes, and the fault modeled as a change in their mean values. Application of the chosen change detection strategy to data taken from a real process is discussed in detail, and the performance of the algorithm is experimentally verified.
IEE Proceedings - Vision, Image, and Signal Processing | 2006
Veljko Papic; Zeljko Djurovic; Branko Kovačević