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Stanimirovic P.S.,University of Nis | Chountasis S.,Hellenic Transmission System Operator SA | Pappas D.,Athens University of Economics and Business | Stojanovic I.,University of Nis
Mathematical Methods in the Applied Sciences | Year: 2013

We propose an image restoration method. The method generalizes image restoration algorithms that are based on the Moore-Penrose solution of certain matrix equations that define the linear motion blur. Our approach is based on the usage of least squares solutions of these matrix equations, wherein an arbitrary matrix of appropriate dimensions is included besides the Moore-Penrose inverse. In addition, the method is a useful tool for improving results obtained by other image restoration methods. Toward that direction, we investigate the case where the arbitrary matrix is replaced by the matrix obtained by the Haar basis reconstructed image. The method has been tested by reconstructing an image after the removal of blur caused by the uniform linear motion and filtering the noise that is corrupted with the image pixels. The quality of the restoration is observable by a human eye. Benefits of using the method are illustrated by the values of the improvement in signal-to-noise ratio and in the values of peak signal-to-noise ratio. © 2013 John Wiley & Sons, Ltd. © 2013 John Wiley & Sons, Ltd. Source

Katsikis V.N.,Technological Educational Institute of Piraeus | Chountasis S.,Hellenic Transmission System Operator SA | Pappas D.,Athens University of Economics and Business
Mathematical Problems in Engineering | Year: 2010

The field of image restoration has seen a tremendous growth in interest over the last two decades. The recovery of an original image from degraded observations is a crucial method and finds application in several scientific areas including medical imaging and diagnosis, military surveillance, satellite and astronomical imaging, and remote sensing. The proposed approach presented in this work employs Fourier coefficients for moment-based image analysis. The main contributions of the presented technique, are that the image is first analyzed in orthogonal basis matrix formulation increasing the selectivity on image components, and then transmitted in the spectral domain. After the transmission has taken place, at the receiving end the image is transformed back and reconstructed from a set of its geometrical moments. The calculation of the Moore-Penrose inverse of r × m matrices provides the computation framework of the method. The method has been tested by reconstructing an image represented by an r × m matrix after the removal of blur caused by uniform linear motions. The noise during the transmission process is another issue that is considered in the current work. © 2010 Spiros Chountasis et al. Source

Savelonas M.A.,National and Kapodistrian University of Athens | Chountasis S.,Hellenic Transmission System Operator SA
Signal Processing | Year: 2010

This paper presents a novel noise-robust scheme for watermark embedding and extraction, applicable on the broad scientific field of information security, including digital encryption for secure transmission. The proposed scheme employs Fourier coefficients for moment-based image analysis and the fractional Fourier transformation for watermark embedding. This approach maintains the advantages of spatial and frequency domain representations, offers two additional degrees of freedom associated with the fractional Fourier transformation angles, whereas it provides increased detectability of the embedded watermarks at the received end. The experimental evaluation of the proposed scheme leads to the conclusion that it is more robust in the presence of noise than previous schemes for watermark embedding and extraction. © 2010 Elsevier B.V. All rights reserved. Source

Kanellos F.D.,National Technical University of Athens | Kanellos F.D.,Hellenic Transmission System Operator SA | Tsekouras G.J.,Hellenic Naval Academy | Hatziargyriou N.D.,National Technical University of Athens
Electric Power Systems Research | Year: 2011

In this paper models of Wind Parks (WPs) appropriate for simulation purposes of large power systems with high wind power penetration are developed. The proposed models of the WPs are developed using system identification theory. Data obtained from the simulation of detailed WP models are used for system identification. The obtained models are general and they can be applied to different configurations of WPs as only system's input/output data are used and not any internal states of the model. Simulation results confirm the accuracy and the advantages of the proposed WP equivalent models. © 2010 Elsevier B.V. All rights reserved. Source

Prousalidis J.M.,National Technical University of Athens | Tsekouras G.J.,Hellenic Naval Academy | Kanellos F.,Hellenic Transmission System Operator SA
2011 IEEE Electric Ship Technologies Symposium, ESTS 2011 | Year: 2011

The current trends in ship technology are turning ships into more energy efficient ones. Thus, the extensive electrification of ship systems, including propulsion, is a most appealing alternative as, the more electrified a ship, the greener and more efficient it turns. In this paper, a brief overview of novel trends regarding electric energy generator schemes is made, and it is shown that these result in new challenges leading to amendments of the traditional concepts dominating over design and operation standards. The discussion is supported by the results of a model comprising a ship generic power grid with multi-type supply units. © 2011 IEEE. Source

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