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116 results on '"Pantazis G"'

1. Fitting a triaxial ellipsoid to a geoid model

Author

Panou G., Korakitis R., and Pantazis G.

Subjects
algebraic fitting, coordinates conversion, geometric fitting, least squares method, principal axes, Geodesy, QB275-343
Abstract

The aim of this work is the determination of the parameters of Earth’s triaxiality through a geometric fitting of a triaxial ellipsoid to a set of given points in space, as they are derived from a geoid model. Starting from a Cartesian equation of an ellipsoid in an arbitrary reference system, we develop a transformation of its coefficients into the coordinates of the ellipsoid center, of the three rotation angles and the three ellipsoid semi-axes. Furthermore, we present different mathematical models for some special and degenerate cases of the triaxial ellipsoid. We also present the required mathematical background of the theory of least-squares, under the condition of minimization of the sum of squares of geoid heights. Also, we describe a method for the determination of the foot points of the set of given space points. Then, we prepare suitable data sets and we derive results for various geoid models, which were proposed in the last fifty years. Among the results, we report the semi-axes of the triaxial ellipsoid of geometric fitting with four unknowns to be 6378171.92 m, 6378102.06 m and 6356752.17 m and the equatorial longitude of the major semi-axis –14.9367 degrees. Also, the parameters of Earth’s triaxiality are directly estimated from the spherical harmonic coefficients of degree and order two. Finally, the results indicate that the geoid heights with reference to the triaxial ellipsoid are smaller than those with reference to the oblate spheroid and the improvement in the corresponding rms value is about 20 per cent.

Published
2020
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2. A Comparison of Thawing and Freezing Dark Energy Parametrizations

Author

Pantazis, G., Nesseris, S., and Perivolaropoulos, L.

Subjects
Astrophysics - Cosmology and Nongalactic Astrophysics, General Relativity and Quantum Cosmology, High Energy Physics - Theory
Abstract

Dark energy equation of state $w(z)$ parametrizations with two parameters and given monotonicity are generically either convex or concave functions. This makes them suitable for fitting either freezing or thawing quintessence models but not both simultaneously. Fitting a dataset based on a freezing model with an unsuitable (concave when increasing) $w(z)$ parametrization (like CPL) can lead to significant misleading features like crossing of the phantom divide line, incorrect $w(z=0)$, incorrect slope \etc that are not present in the underlying cosmological model. To demonstrate this fact we generate scattered cosmological data both at the level of $w(z)$ and the luminosity distance $D_L(z)$ based on either thawing or freezing quintessence models and fit them using parametrizations of convex and of concave type. We then compare statistically significant features of the best fit $w(z)$ with actual features of the underlying model. We thus verify that the use of unsuitable parametrizations can lead to misleading conclusions. In order to avoid these problems it is important to either use both convex and concave parametrizations and select the one with the best $\chi^2$ or use principal component analysis thus splitting the redshift range into independent bins. In the latter case however, significant information about the slope of $w(z)$ at high redshifts is lost. Finally, we propose a new family of parametrizations (nCPL) $w(z)=w_0+w_a (\frac{z}{1+z})^n$ which generalizes the CPL and interpolates between thawing and freezing parametrizations as the parameter $n$ increases to values larger than 1., Comment: 17 pages, 19 Figures. The numerical analysis files may be downloaded from https://www.dropbox.com/s/0gyal92olbcwabt/parametrizations.zip?dl=0 . Minor modifications compared to previous version. References added. Accepted in Phys. Rev. D (to appear)

Published
2016
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5. Data-driven algorithms for multi-agent optimization and games

Author

Pantazis, G

Subjects
Multi-agent systems, Scenario approach, Statistical learning
Abstract

Multi-agent optimization and game theory constitute fundamental frameworks for modelling a plethora of engineering problems. In some systems, agents cooperate to optimize a collective cost, thus giving rise to multi-agent optimization programs. In other cases, agents act as selfish entities wishing to minimize their own individual cost subject to local or global constraints. To model such behaviour, non-cooperative game theory is required. Finally, agents though selfish can opt towards the formation of coalitions such that they receive a higher payoff. Such systems are studied under the lenses of cooperative game theory. One of the most crucial challenges in such problems is finding solutions that are robust against the effects of uncertainty. Uncertainty represents our lack of knowledge about how the underlying system behaves and usually originates from unmodelled dynamics or external factors. Its significance is apparent in modern applications such as the electric vehicle charging problem, the optimal power flow problem with power generation from renewable energy sources, transportation and social networks. Following a data-driven approach, this thesis builds a theoretical framework for the provision of robustness certificates for solutions to multi-agent optimization problems and non-cooperative games with an arbitrary cost function and uncertainty in the constraints. The theoretical tools developed allow the provision of collective certificates for sets (and subsets) of solutions that do not necessarily need to be optimal. Focusing on the class of aggregative games, agents’ deviations from an equilibrium solution and uncertain constraints are considered. A data-driven equilibrium seeking algorithm is then proposed such that tunable collective guarantees can be provided for all possible feasible deviations from the equilibrium. Shifting our attention towards a particular class of optimization programs with uncertain cost, prevalent in practical applications, we provide probabilistic guarantees for the randomized optimizer that do not depend on the number of agents but only on the size of the decision vector of each agent. As such, the probabilistic guarantees provided are scalable as the number of agents increases. Finally, a data-driven theoretical framework is established for multi-agent cooperative games with uncertain value functions. Collective stability guarantees for the entire core set, a fundamental concept in cooperative game theory, are provided based on data from the value functions in a probably approximately correct learning fashion. The case where the core can be empty is considered and a methodology to accompany allocations in a relaxed core with stability certificates is proposed.

Published
2023

6. Distributionally robust stability of payoff allocations in stochastic coalitional games

Author

Pantazis, G, Franci, B, Grammatico, S, and Margellos, K

Subjects
Optimization and Control (math.OC), FOS: Mathematics, FOS: Electrical engineering, electronic engineering, information engineering, Systems and Control (eess.SY), Mathematics - Optimization and Control, Electrical Engineering and Systems Science - Systems and Control
Abstract

We consider multi-agent coalitional games with uncertainty in the coalitional values. We provide a novel methodology to study the stability of the grand coalition in the case where each coalition constructs ambiguity sets for the (possibly) unknown probability distribution of the uncertainty. As a less conservative solution concept compared to worst-case approaches for coalitional stability, we consider a stochastic version of the so-called core set, i.e., the expected value core. Unfortunately, without exact knowledge of the probability distribution, the evaluation of the expected value core is an extremely challenging task. Hence, we propose the concept of distributionaly robust (DR) core. Leveraging tools from data-driven DR optimization under the Wasserstein distance, we provide finite-sample guarantees that any allocation which lies in the DR core is also stable with respect to the true probability distribution. Furthermore, we show that as the number of samples grows unbounded, the DR core converges almost surely to the true expected value core. We dedicate the last section to the computational tractability of finding an allocation in the DR core.

Published
2023
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11. Evaluation of the credibility of reflectorless distance measurement

Author

Lambrou, E. and Pantazis, G.

Subjects
Surveying -- Management, Distances -- Measurement, Distances -- Methods, Company business management, Engineering and manufacturing industries, Science and technology
Abstract

Reflectorless distance measurement provides the ability to easily make quick measurements saving time and labor for surveyors. The precision and accuracy of these types of measurements are under discussion because of the variety of parameters that can affect these measurements that are not well-understood. This paper attempts to answer some of the questions that have arisen about the credibility of reflectorless distance measurements ranging up to 50 m. An experiment was carried out using 26 different materials as the reflecting surface (these materials were also of differing colors). Additionally, the experiment used three different angles of incidence of the incoming electromagnetic energy with three different types of reflectorless total stations over a variety of ranges. A further experiment was conducted with an additional total station using 11 different materials at different ranges. To properly evaluate the results, a special supporting base was manufactured for holding the reflecting surface to ensure accuracy in the evaluation. The results are presented in tables and the conclusions that are derived indicate that further investigation is needed, especially at longer distances, as the parameters that influence reflectorless distance measurement in those situations are many more, and more important than at short ranges. DOI: 10.1061/(ASCE)SU.1943-5428.0000029 CE Database subject headings: Experimentation; Distance measurement; Surveys. Author keywords: Reflectorless; Experiment; Material; Credibility.

Published
2010

17. MERGING GEOMETRIC DOCUMENTATION WITH MATERIALS CHARACTERIZATION AND ANALYSIS OF THE HISTORY OF THE HOLY AEDICULE IN THE CHURCH OF THE HOLY SEPULCHRE IN JERUSALEM

Author

Georgopoulos, A., primary, Lambrou, E., additional, Pantazis, G., additional, Agrafiotis, P., additional, Papadaki, A., additional, Kotoula, L., additional, Lampropoulos, K., additional, Delegou, E., additional, Apostolopoulou, M., additional, Alexakis, M., additional, and Moropoulou, A., additional

Published
2017
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20. Microarray based comparison of Neurofibromatosis Type 2 associated vestibular schwannomas show an over-expression of TSPAN8 compared to the sporadic form

Author

Krischek, B., Gugel, I., Pantazis, G., Bornemann, A., Roder, C., Feigl, G., Roser, F., Schuhmann, M., Bonin, M., and Tatagiba, M.

Subjects
ddc: 610, otorhinolaryngologic diseases, sense organs, 610 Medical sciences, Medicine
Abstract

Objective: Vestibular schwannomas, also known as acoustic neuromas, are benign tumors of the vestibular part of the eighth cranial nerve, the vestibulocochlear nerve. 95% of the cases are sporadic, non-familiar and unilateral. In 5% of the cases they are bilateral and caused by the autosomal[for full text, please go to the a.m. URL], 62. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit der Polnischen Gesellschaft für Neurochirurgen (PNCH)

Published
2011
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25. Ecosystem Services Evaluation from Sustainable Water Management in Agriculture: An Example from An Intensely Irrigated Area in Central Greece

Author

Yiannis Panagopoulos, Dimitrios Karpouzos, Pantazis Georgiou, and Dimitrios Papamichail

Subjects
ecosystem services, hydrologic modelling, irrigated agriculture, Karla reservoir, SWAT, water management, Environmental sciences, GE1-350
Abstract

This study presents the provisional, regulating and cultural ecosystem services that can be delivered by the newly constructed multi-purpose reservoir of Lake Karla located in a water-scarce agricultural area in central Greece. The present short paper takes advantage of literature data and outputs produced from a dynamic GIS hydrologic and management model of the study area with SWAT that simulated hydrology, reservoir operation, irrigation practices and crop production. The paper highlights the net provisional services that the local agricultural society can gain from the full operation of Karla and the additional benefits arising, such as flood control, biodiversity maintenance, aesthetic improvement and touristic opportunities.

Published
2023
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27. CELL BIOLOGY AND SIGNALING

Author

Agarwal, M., primary, Nitta, R., additional, Dovat, S., additional, Li, G., additional, Arita, H., additional, Narita, Y., additional, Fukushima, S., additional, Tateishi, K., additional, Matsushita, Y., additional, Yoshida, A., additional, Miyakita, Y., additional, Ohno, M., additional, Collins, V. P., additional, Kawahara, N., additional, Shibui, S., additional, Ichimura, K., additional, Kahn, S. A., additional, Gholamin, S., additional, Junier, M.-P., additional, Chneiweiss, H., additional, Weissman, I., additional, Mitra, S., additional, Cheshier, S., additional, Avril, T., additional, Hamlat, A., additional, Le Reste, P.-J., additional, Mosser, J., additional, Quillien, V., additional, Carrato, C., additional, Munoz-Marmol, A., additional, Serrano, L., additional, Pijuan, L., additional, Hostalot, C., additional, Villa, S. l., additional, Ariza, A., additional, Etxaniz, O., additional, Balana, C., additional, Benveniste, E. T., additional, Zheng, Y., additional, McFarland, B., additional, Drygin, D., additional, Bellis, S., additional, Bredel, M., additional, Lotsch, D., additional, Engelmaier, C., additional, Allerstorfer, S., additional, Grusch, M., additional, Pichler, J., additional, Weis, S., additional, Hainfellner, J., additional, Marosi, C., additional, Spiegl-Kreinecker, S., additional, Berger, W., additional, Bronisz, A., additional, Nowicki, M. O., additional, Wang, Y., additional, Ansari, K., additional, Chiocca, E. A., additional, Godlewski, J., additional, Brown, K., additional, Kwatra, M., additional, Bui, T., additional, Zhu, S., additional, Kozono, D., additional, Li, J., additional, Kushwaha, D., additional, Carter, B., additional, Chen, C., additional, Schulte, J., additional, Srikanth, M., additional, Das, S., additional, Zhang, J., additional, Lathia, J., additional, Yin, L., additional, Rich, J., additional, Olson, E., additional, Kessler, J., additional, Chenn, A., additional, Cherry, A., additional, Haas, B., additional, Lin, Y. H., additional, Ong, S.-E., additional, Stella, N., additional, Cifarelli, C. P., additional, Griffin, R. J., additional, Cong, D., additional, Zhu, W., additional, Shi, Y., additional, Clark, P., additional, Kuo, J., additional, Hu, S., additional, Sun, D., additional, Bookland, M., additional, Darbinian, N., additional, Dey, A., additional, Robitaille, M., additional, Remke, M., additional, Faury, D., additional, Maier, C., additional, Malhotra, A., additional, Jabado, N., additional, Taylor, M., additional, Angers, S., additional, Kenney, A., additional, Ren, X., additional, Zhou, H., additional, Schur, M., additional, Baweja, A., additional, Singh, M., additional, Erdreich-Epstein, A., additional, Fu, J., additional, Koul, D., additional, Yao, J., additional, Saito, N., additional, Zheng, S., additional, Verhaak, R., additional, Lu, Z., additional, Yung, W. K. A., additional, Gomez, G., additional, Volinia, S., additional, Croce, C., additional, Brennan, C., additional, Cavenee, W., additional, Furnari, F., additional, Lopez, S. G., additional, Qu, D., additional, Petritsch, C., additional, Gonzalez-Huarriz, M., additional, Aldave, G., additional, Ravi, D., additional, Rubio, A., additional, Diez-Valle, R., additional, Marigil, M., additional, Jauregi, P., additional, Vera, B., additional, Rocha, A. A. d. l., additional, Tejada-Solis, S., additional, Alonso, M. M., additional, Gopal, U., additional, Isaacs, J., additional, Gruber-Olipitz, M., additional, Dabral, S., additional, Ramkissoon, S., additional, Kung, A., additional, Pak, E., additional, Chung, J., additional, Theisen, M., additional, Sun, Y., additional, Monrose, V., additional, Franchetti, Y., additional, Shulman, D., additional, Redjal, N., additional, Tabak, B., additional, Beroukhim, R., additional, Zhao, J., additional, Buonamici, S., additional, Ligon, K., additional, Kelleher, J., additional, Segal, R., additional, Canton, D., additional, Diaz, P., additional, Scott, J., additional, Hara, K., additional, Kageji, T., additional, Mizobuchi, Y., additional, Kitazato, K., additional, Okazaki, T., additional, Fujihara, T., additional, Nakajima, K., additional, Mure, H., additional, Kuwayama, K., additional, Hara, T., additional, Nagahiro, S., additional, Hill, L., additional, Botfield, H., additional, Hossain-Ibrahim, K., additional, Logan, A., additional, Cruickshank, G., additional, Liu, Y., additional, Gilbert, M., additional, Kyprianou, N., additional, Rangnekar, V., additional, Horbinski, C., additional, Hu, Y., additional, Vo, C., additional, Li, Z., additional, Ke, C., additional, Ru, N., additional, Hess, K. R., additional, Linskey, M. E., additional, Zhou, Y.-a. H., additional, Hu, F., additional, Vinnakota, K., additional, Wolf, S., additional, Kettenmann, H., additional, Jackson, P. J., additional, Larson, J. D., additional, Beckmann, D. A., additional, Moriarity, B. S., additional, Largaespada, D. A., additional, Jalali, S., additional, Agnihotri, S., additional, Singh, S., additional, Burrell, K., additional, Croul, S., additional, Zadeh, G., additional, Kang, S.-H., additional, Yu, M. O., additional, Song, N.-H., additional, Park, K.-J., additional, Chi, S.-G., additional, Chung, Y.-G., additional, Kim, S. K., additional, Kim, J. W., additional, Kim, J. Y., additional, Kim, J. E., additional, Choi, S. H., additional, Kim, T. M., additional, Lee, S.-H., additional, Kim, S.-K., additional, Park, S.-H., additional, Kim, I. H., additional, Park, C.-K., additional, Jung, H.-W., additional, Koldobskiy, M., additional, Ahmed, I., additional, Ho, G., additional, Snowman, A., additional, Raabe, E., additional, Eberhart, C., additional, Snyder, S., additional, Gugel, I., additional, Bornemann, A., additional, Pantazis, G., additional, Mack, S., additional, Shih, D., additional, Sabha, N., additional, Tatagiba, M., additional, Krischek, B., additional, Schulte, A., additional, Liffers, K., additional, Kathagen, A., additional, Riethdorf, S., additional, Westphal, M., additional, Lamszus, K., additional, Lee, J. S., additional, Xiao, J., additional, Patel, P., additional, Schade, J., additional, Wang, J., additional, Deneen, B., additional, Song, H.-R., additional, Leiss, L., additional, Gjerde, C., additional, Saed, H., additional, Rahman, A., additional, Lellahi, M., additional, Enger, P. O., additional, Leung, R., additional, Gil, O., additional, Lei, L., additional, Canoll, P., additional, Sun, S., additional, Lee, D., additional, Ho, A. S. W., additional, Pu, J. K. S., additional, Zhang, X.-q., additional, Lee, N. P., additional, Dat, P. J. R., additional, Leung, G. K. K., additional, Loetsch, D., additional, Steiner, E., additional, Holzmann, K., additional, Pirker, C., additional, Hlavaty, J., additional, Petznek, H., additional, Hegedus, B., additional, Garay, T., additional, Mohr, T., additional, Sommergruber, W., additional, Lukiw, W. J., additional, Jones, B. M., additional, Zhao, Y., additional, Bhattacharjee, S., additional, Culicchia, F., additional, Magnus, N., additional, Garnier, D., additional, Meehan, B., additional, McGraw, S., additional, Hashemi, M., additional, Lee, T. H., additional, Milsom, C., additional, Gerges, N., additional, Trasler, J., additional, Pawlinski, R., additional, Mackman, N., additional, Rak, J., additional, Maherally, Z., additional, Thorne, A., additional, An, Q., additional, Barbu, E., additional, Fillmore, H., additional, Pilkington, G., additional, Tan, S. L., additional, Tan, S., additional, Choi, S., additional, Potts, C., additional, Ford, D. A., additional, Nahle, Z., additional, Kenney, A. M., additional, Matlaf, L., additional, Khan, S., additional, Zider, A., additional, Singer, E., additional, Cobbs, C., additional, Soroceanu, L., additional, McFarland, B. C., additional, Hong, S. W., additional, Rajbhandari, R., additional, Twitty, G. B., additional, Gray, G. K., additional, Yu, H., additional, Benveniste, E. N., additional, Nozell, S. E., additional, Minata, M., additional, Kim, S., additional, Mao, P., additional, Kaushal, J., additional, Nakano, I., additional, Mizowaki, T., additional, Sasayama, T., additional, Tanaka, K., additional, Mizukawa, K., additional, Nishihara, M., additional, Nakamizo, S., additional, Tanaka, H., additional, Kohta, M., additional, Hosoda, K., additional, Kohmura, E., additional, Moeckel, S., additional, Meyer, K., additional, Leukel, P., additional, Bogdahn, U., additional, Riehmenschneider, M. J., additional, Bosserhoff, A. K., additional, Spang, R., additional, Hau, P., additional, Mukasa, A., additional, Watanabe, A., additional, Ogiwara, H., additional, Aburatani, H., additional, Mukherjee, J., additional, Obha, S., additional, See, W., additional, Pieper, R., additional, Otsuka, R., additional, Kung, D., additional, Sinha, T., additional, Meares, G., additional, Nozell, S., additional, Ott, M., additional, Litzenburger, U., additional, Rauschenbach, K., additional, Bunse, L., additional, Pusch, S., additional, Ochs, K., additional, Sahm, F., additional, Opitz, C., additional, von Deimling, A., additional, Wick, W., additional, Platten, M., additional, Peruzzi, P., additional, Read, R., additional, Fenton, T., additional, Wykosky, J., additional, Vandenberg, S., additional, Babic, I., additional, Iwanami, A., additional, Yang, H., additional, Mischel, P., additional, Thomas, J., additional, Ronellenfitsch, M. W., additional, Thiepold, A. L., additional, Harter, P. N., additional, Mittelbronn, M., additional, Steinbach, J. P., additional, Rybakova, Y., additional, Kalen, A., additional, Sarsour, E., additional, Goswami, P., additional, Silber, J., additional, Harinath, G., additional, Aldaz, B., additional, Fabius, A. W. M., additional, Turcan, S., additional, Chan, T. A., additional, Huse, J. T., additional, Sonabend, A. M., additional, Bansal, M., additional, Guarnieri, P., additional, Soderquist, C., additional, Yun, J., additional, Kennedy, B., additional, Sisti, J., additional, Bruce, S., additional, Bruce, R., additional, Shakya, R., additional, Ludwig, T., additional, Rosenfeld, S., additional, Sims, P. A., additional, Bruce, J. N., additional, Califano, A., additional, Stockhausen, M.-T., additional, Kristoffersen, K., additional, Olsen, L. S., additional, Poulsen, H. S., additional, Stringer, B., additional, Day, B., additional, Barry, G., additional, Piper, M., additional, Jamieson, P., additional, Ensbey, K., additional, Bruce, Z., additional, Richards, L., additional, Boyd, A., additional, Sufit, A., additional, Burleson, T., additional, Le, J. P., additional, Keating, A. K., additional, Sundstrom, T., additional, Varughese, J. K., additional, Harter, P., additional, Prestegarden, L., additional, Petersen, K., additional, Azuaje, F., additional, Tepper, C., additional, Ingham, E., additional, Even, L., additional, Johnson, S., additional, Skaftnesmo, K. O., additional, Lund-Johansen, M., additional, Bjerkvig, R., additional, Ferrara, K., additional, Thorsen, F., additional, Takeshima, H., additional, Yamashita, S., additional, Yokogami, K., additional, Mizuguchi, S., additional, Nakamura, H., additional, Kuratsu, J., additional, Fukushima, T., additional, Morishita, K., additional, Tang, Y., additional, Vaka, D., additional, Chen, S., additional, Ponnuswami, A., additional, Cho, Y.-J., additional, Monje, M., additional, Nakamura, T., additional, Cahill, D., additional, Tiemann, K., additional, Hedman, H., additional, Niclou, S. P., additional, Timmer, M., additional, Tjiong, R., additional, Rohn, G., additional, Goldbrunner, R., additional, Stavrinou, P., additional, Perrech, M., additional, Tokita, M., additional, Mikheev, S., additional, Sellers, D., additional, Mikheev, A., additional, Kosai, Y., additional, Rostomily, R., additional, Tritschler, I., additional, Seystahl, K., additional, Schroeder, J. J., additional, Weller, M., additional, Wade, A., additional, Robinson, A. E., additional, Phillips, J. J., additional, Gong, Y., additional, Ma, Y., additional, Cheng, Z., additional, Thompson, R., additional, Fan, Q.-W., additional, Cheng, C., additional, Gustafson, W., additional, Charron, E., additional, Zipper, P., additional, Wong, R., additional, Chen, J., additional, Lau, J., additional, Knobbe-Thosen, C., additional, Jura, N., additional, Reifenberger, G., additional, Shokat, K., additional, Weiss, W., additional, Wu, S., additional, Hu, J., additional, Taylor, T., additional, Villa, G. R., additional, Mischel, P. S., additional, Gonias, S. L., additional, Yamashita, D., additional, Kondo, T., additional, Takahashi, H., additional, Inoue, A., additional, Kohno, S., additional, Harada, H., additional, Ohue, S., additional, Ohnishi, T., additional, Li, P., additional, Ng, J., additional, Yuelling, L., additional, Du, F., additional, Curran, T., additional, Yang, Z.-j., additional, Zhu, D., additional, Castellino, R. C., additional, Van Meir, E. G., additional, Begum, G., additional, Wang, Q., additional, Yang, S.-S., additional, Lin, S.-H., additional, and Kahle, K., additional

Published
2013
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30. Focal cortical dysplasias

Author

Fauser, S, Schulze-Bonhage, BA, Honegger, J, Carmona, H, Rona, S, Huppertz, HJ, Bast, T, Strobl, K, Pantazis, G, Steinhoff, BJ, Korinthenberg, R, Rating, D, Volk, B, Zentner, J, Fauser, S, Schulze-Bonhage, BA, Honegger, J, Carmona, H, Rona, S, Huppertz, HJ, Bast, T, Strobl, K, Pantazis, G, Steinhoff, BJ, Korinthenberg, R, Rating, D, Volk, B, and Zentner, J

Published
2005

37. An optimization technique for the fourier analysis of the light curves of totally-eclipsing systems of algol-type

Author

Niarchos, P.G. Pantazis, G.

Subjects
Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics
Abstract

A fully automatized technique for the evaluation of geometric and photometric elements of Algol-type systems exhibiting total eclipses is presented. The method requires observations in at least two wavelengths and enables us to choose the most probable solution from a grid of solutions performed with various possible phase angles of the first contact of the eclipse. © 1990 Kluwer Academic Publishers.

Published
1990

44. Use of Factor Analysis (FA), Artificial Neural Networks (ANNs), and Multiple Linear Regression (MLR) for Electrical Conductivity Prediction in Aquifers in the Gallikos River Basin, Northern Greece

Author

Christos Mattas, Lamprini Dimitraki, Pantazis Georgiou, and Panagiota Venetsanou

Subjects
artificial neural network, multiple linear regression, groundwater, electrical conductivity, factor analysis, Science
Abstract

Due to the fact of water resource deterioration from human activities and increased demand over the last few decades, optimization of management practices and policies is required, for which more reliable data are necessary. Cost and time are always of importance; therefore, methods that can provide low-cost data in a short period of time have been developed. In this study, the ability of an artificial neural network (ANN) and a multiple linear regression (MLR) model to predict the electrical conductivity of groundwater samples in the GallikosRiver basin, northern Greece, was examined. A total of 233 samples were collected over the years 2004–2005 from 89 sampling points. Descriptive statistics, Pearson correlation matrix, and factor analysis were applied to select the inputs of the water quality parameters. Input data to the ANN and MLR were Ca, Mg, Na, and Cl. The best results regarding the ANN were provided by a model that included one hidden layer of three neurons. The mean absolute percentage error, modeling efficiency, and root mean square error were used to evaluate the performances of the methods and to compare the prediction capabilities of the ANN and MLR. We concluded that the ANN and MLR models were valid and had similar accuracy (using the same inputs) with a large number of samples, but in the case of a smaller data set, the MLR showed a better performance.

Published
2021
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45. Assessment of Minimum Water Level in Lakes and Reservoirs Based on Their Morphological and Hydrological Features

Author

Charalampos Doulgeris, Panagiota Koukouli, Pantazis Georgiou, Paschalis Dalampakis, and Dimitrios Karpouzos

Subjects
minimum lake level, hydromorphological analysis, Lake Vegoritida catchment, Greek lakes, Science
Abstract

The sustainable management of lakes and reservoirs requires the determination of their minimum environmental water level. Even though the assessment of minimum water level depends on a number of biotic and abiotic factors of the lake ecosystem, in many cases these factors are not entirely known and, furthermore, their evaluation is usually a challenging and laborious task. On the other hand, the lakes/reservoirs may comprise an important water resource to meet the requirements arising from economic activities. In this paper, the morphological and hydrological features of four lakes of northern Greece were analysed in order to assess their minimum environmental water level. The hydromorphological analysis was based on the relationship of the lake surface area and volume with water level as well as the water inflow from the lake’s hydrological catchment area, considering as the lake’s critical volume storage, the annual water volume flowing into a lake from its hydrological catchment area with a probability of exceedance 50% of a long time series of hydrological years. By combining morphological and hydrological features, the proposed methodology aimed to extend the analysis based solely on morphological features, and assess more comprehensively the minimum environmental water level in the four lakes, ensuring also the rising from the minimum level to the maximum (overflow) level for most of the hydrological years.

Published
2020
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46. Effect of Water Stress on the Physiological Characteristics of Five Basil (Ocimum basilicum L.) Cultivars

Author

Iakovos Kalamartzis, George Menexes, Pantazis Georgiou, and Christos Dordas

Subjects
water potential, chlorophyll content, chlorophyll fluorescence, photosynthesis, essential oil content, Agriculture
Abstract

Water stress in one of the most important abiotic stresses that affects the productivity of many crop species worldwide. In addition, the climate change creates new challenges for crop adaptation especially as water resources become limited and the increase in water stress becomes more pronounced even in areas where there is adequate water supply. The objective of the present study was to determine the effect of water stress on physiological characteristics of five cultivars of basil under field conditions. Water stress affected leaf temperature, dry herb yield, leaf water potential, assimilation rate and gas exchange parameters, quantum yield, instantaneous water use efficiency (WUE), and essential oil content. From the physiological characteristics water potential and assimilation rate can be used for the selection of basil cultivars tolerant to water stress. In addition, essential oil content was lower under water stress indicating that essential oil content is correlated with water availability. From the present study it is obvious that there are tolerant basil cultivars to water stress and can be found using physiological traits such as water potential and assimilation rate and can be used to save and use water more sustainable and also conserve the water resources.

Published
2020
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47. The Use of Appropriate Cultivar of Basil (Ocimum basilicum) Can Increase Water Use Efficiency under Water Stress

Author

Iakovos Kalamartzis, Christos Dordas, Pantazis Georgiou, and George Menexes

Subjects
drought tolerance, dry weight yield, essential oil content, leaf area index, ocimum basilicum, Agriculture
Abstract

Drought is one of the major yield constraints of crop productivity for many crops. In addition, nowadays, climate change creates new challenges for crop adaptation in stressful environments. The objective of the present study was to determine the effect of water stress on five cultivars of basil (Mrs Burns, Cinnamon, Sweet, Red Rubin, Thai) and whether water use efficiency (WUE) can be increased by using the appropriate cultivar. Water stress affected the fresh and dry weight and also the partitioning of dry matter to leaves, flowers, and stems. Also, there are cultivars, such as Mrs Burns and Sweet, which were not affected by the limited amount of water and continued to produce a high amount of dry matter and also showed high essential oil yield. Essential oil content was not affected by the irrigation; however, essential oil yield was affected by the irrigation, and the highest values were found at Mrs Burns. The water use efficiency was affected by the cultivar and irrigation level, and the highest was found at Mrs Burns. The results show that using appropriate cultivars basil can achieve higher WUE and allow saving water resources and utilizing fields in areas with limited water resources for irrigation.

Published
2020
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48. Time series analysis of water quality parameters

Author

Abdollah Taheri Tizro, Maryam Ghashghaie, Pantazis Georgiou, and Konstantinos Voudouris

Subjects
Water Quality, Time series, ARIMA, ACF, PACF, Environmental technology. Sanitary engineering, TD1-1066
Abstract

Water quality is a worldwide problem which affects human beings lives fundamentally. Water scarcity is intensified in result of quality deterioration. Different factors such as population increase, economic development and water pollution could be considered as the origins of the problem. The study and forecasting of water quality is necessary to prevent serious water quality deteriorations in future. Different methodologies have been used to predict and estimate the quality of water. In present study using time series modeling, the quality of Hor Rood River is studied at Kakareza station using time series analysis. 9 parameters of water quality are studied such as: TDS, EC, HCO3-, SO42-, Mg2+, Ca2+, Na+, pH and SAR. Investigation of observed time series show that there is an increasing trend for all parameters unless Na+, pH and SAR. The order of model for each parameter was determined using auto correlation function (ACF) and partial auto correlation function (PACF) of time series. ARIMA (autoregressive, integrated, moving average) model was found suitable to generate and forecast the quality of river water. AIC, R2, RMSE and VE % criteria were used for evaluating the generation and forecasting results. Results show that time series modeling is quite capable of water quality forecasting. For all generated and forecasted parameters the value of R2 was greater than 0.66 Except for SO42-. The value of R2 for generated SO42- was 0.48 and this value was 0.43 for forecasting this parameter. Also the study show that the quality of water is deteriorating based on an increasing trend for the majority of parameters and needs serious managerial actions.

Published
2014

49. Late cytomegalovirus polyradiculopathy following haploidentical CD34+-selected hematopoietic stem cell transplantation.

Author

Zeiser, R., Grüllich, C., Bertz, H., Pantazis, G., Hufert, F. T., Bley, T. A., and Finke, J.

Subjects
CYTOMEGALOVIRUSES, STEM cell transplantation, CD antigens, HEMATOPOIETIC stem cells, CYTOMEGALOVIRUS diseases, POLYRADICULOPATHY
Abstract

Summary:A 55-year-old man with acute myeloid leukemia in second relapse presented 4 months after haploidentical CD34+-selected hematopoietic stem cell transplantation (HSCT) with symmetric, progressive neurological deficits of the lower extremities. Although there was no molecular evidence for drug resistance in the cerebral-spinal fluid, antiviral combination therapy failed to control the rapidly progressing CMV polyradiculopathy (PRP) and encephalitis, which were confirmed by autopsy studies. Late CMV PRP as an unusual manifestation of CMV disease should be kept in mind in patients with suggestive neurological symptoms after HSCT.Bone Marrow Transplantation (2004) 33, 243-245. doi:10.1038/sj.bmt.1704311 [ABSTRACT FROM AUTHOR]

Published
2004
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