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2. Content-Based Recommender Systems Taxonomy

Author

Papadakis Harris, Papagrigoriou Antonis, Kosmas Eleftherios, Panagiotakis Costas, Markaki Smaragda, and Fragopoulou Paraskevi

Subjects
content-based systems, recommendation systems, survey, taxonomy, Electronic computers. Computer science, QA75.5-76.95
Abstract

In the era of internet access, recommender systems try to alleviate the difficulty consumers face while trying to find items (e.g. services, products, or information) that better match their needs. To do so, a recommender system selects and proposes (possibly unknown) items that may be of interest to some candidate consumer, by predicting her/his preference for this item. Given the diversity of needs between consumers and the enormous variety of items to be recommended, a large set of approaches have been proposed by the research community. This paper provides a review of the approaches proposed in the entire research area of content-based recommender systems, and not only in one part of it. To facilitate understanding, we provide a categorization of each approach based on the tools and techniques employed, which results to the main contribution of this paper, a content-based recommender systems taxonomy. This way, the reader acquires a quick and complete understanding of this research area. Finally, we provide a comparison of content-based recommender systems according to their ability to efficiently handle well-known drawbacks.

Published
2023
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8. Unsupervised Color-Based Flood Segmentation in UAV Imagery.

Author

Simantiris, Georgios and Panagiotakis, Costas

Subjects
*DRONE aircraft, *IMAGE analysis, *LANDSAT satellites, *IMAGE segmentation
Abstract

We propose a novel unsupervised semantic segmentation method for fast and accurate flood area detection utilizing color images acquired from unmanned aerial vehicles (UAVs). To the best of our knowledge, this is the first fully unsupervised method for flood area segmentation in color images captured by UAVs, without the need of pre-disaster images. The proposed framework addresses the problem of flood segmentation based on parameter-free calculated masks and unsupervised image analysis techniques. First, a fully unsupervised algorithm gradually excludes areas classified as non-flood, utilizing calculated masks over each component of the LAB colorspace, as well as using an RGB vegetation index and the detected edges of the original image. Unsupervised image analysis techniques, such as distance transform, are then applied, producing a probability map for the location of flooded areas. Finally, flood detection is obtained by applying hysteresis thresholding segmentation. The proposed method is tested and compared with variations and other supervised methods in two public datasets, consisting of 953 color images in total, yielding high-performance results, with 87.4% and 80.9% overall accuracy and F1-score, respectively. The results and computational efficiency of the proposed method show that it is suitable for onboard data execution and decision-making during UAV flights. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Visit Planner: A Personalized Mobile Trip Design Application based on a Hybrid Recommendation Model.

Author

Papadakis, Harris, Panagiotakis, Costas, Fragopoulou, Paraskevi, Chalkiadakis, Georgios, Streviniotis, Errikos, Ziogas, Ioannis-Panagiotis, Koutsmanis, Michail, and Bariamis, Panagiotis

Abstract

The paper presents Visit Planner (ViP), a mobile application prototype that provides a solution to the challenging tourist trip design problem. ViP follows a holistic approach offering personalized recommendations for Points of Interest (POIs) based on preferences either explicitly collected by the application, or inferred by the users' ongoing interaction with the system. ViP proposes to the final user, a trajectory of POIs calculated using an Expectation Maximization method that maximizes user satisfaction taking into consideration a variety of time and spatial constraints for both users and POIs. Additionally, POIs are divided into categories, so that a certain number of POIs from each category to be included in the final itinerary. The application is implemented as a user-interactive system that allows the flexibility for easy content adaptation and facilitates management of content and services by the user. The prototype has been implemented for Android-based smartphones, on an open application environment, using standard communication protocols and open database technology. Currently, it is applied to the city of Agios Nikolaos in Crete, and is available for download from Google play. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Personalized Video Summarization Based Exclusively on User Preferences

Author

Panagiotakis, Costas, Papadakis, Harris, Fragopoulou, Paraskevi, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Jose, Joemon M., editor, Yilmaz, Emine, editor, Magalhães, João, editor, Castells, Pablo, editor, Ferro, Nicola, editor, Silva, Mário J., editor, and Martins, Flávio, editor

Published
2020
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13. A Two-Stage Approach for Commonality-Based Temporal Localization of Periodic Motions

Author

Panagiotakis, Costas, Argyros, Antonis, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Tzovaras, Dimitrios, editor, Giakoumis, Dimitrios, editor, Vincze, Markus, editor, and Argyros, Antonis, editor

Published
2019
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27. Beat Synchronous Dance Animation Based on Visual Analysis of Human Motion and Audio Analysis of Music Tempo

Author

Panagiotakis, Costas, Holzapfel, Andre, Michel, Damien, Argyros, Antonis A., Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Bebis, George, editor, Boyle, Richard, editor, Parvin, Bahram, editor, Koracin, Darko, editor, Li, Baoxin, editor, Porikli, Fatih, editor, Zordan, Victor, editor, Klosowski, James, editor, Coquillart, Sabine, editor, Luo, Xun, editor, Chen, Min, editor, and Gotz, David, editor

Published
2013
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28. Voting Clustering and Key Points Selection

Author

Panagiotakis, Costas, Fragopoulou, Paraskevi, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Wilson, Richard, editor, Hancock, Edwin, editor, Bors, Adrian, editor, and Smith, William, editor

Published
2013
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29. Interactive Image Segmentation via Graph Clustering and Synthetic Coordinates Modeling

Author

Panagiotakis, Costas, Papadakis, Harris, Grinias, Elias, Komodakis, Nikos, Fragopoulou, Paraskevi, Tziritas, Georgios, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Wilson, Richard, editor, Hancock, Edwin, editor, Bors, Adrian, editor, and Smith, William, editor

Published
2013
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30. Video Synopsis Based on a Sequential Distortion Minimization Method

Author

Panagiotakis, Costas, Ovsepian, Nelly, Michael, Elena, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Wilson, Richard, editor, Hancock, Edwin, editor, Bors, Adrian, editor, and Smith, William, editor

Published
2013
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33. Lymphocyte Segmentation Using the Transferable Belief Model

Author

Panagiotakis, Costas, Ramasso, Emmanuel, Tziritas, Georgios, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Ünay, Devrim, editor, Çataltepe, Zehra, editor, and Aksoy, Selim, editor

Published
2010
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34. Unsupervised Trajectory Sampling

Author

Pelekis, Nikos, Kopanakis, Ioannis, Panagiotakis, Costas, Theodoridis, Yannis, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Goebel, Randy, editor, Siekmann, Jörg, editor, Wahlster, Wolfgang, editor, Balcázar, José Luis, editor, Bonchi, Francesco, editor, Gionis, Aristides, editor, and Sebag, Michèle, editor

Published
2010
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35. Trajectory Voting and Classification Based on Spatiotemporal Similarity in Moving Object Databases

Author

Panagiotakis, Costas, Pelekis, Nikos, Kopanakis, Ioannis, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Adams, Niall M., editor, Robardet, Céline, editor, Siebes, Arno, editor, and Boulicaut, Jean-François, editor

Published
2009
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37. Shape-Motion Based Athlete Tracking for Multilevel Action Recognition

Author

Panagiotakis, Costas, Ramasso, Emmanuel, Tziritas, Georgios, Rombaut, Michèle, Pellerin, Denis, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Perales, Francisco J., editor, and Fisher, Robert B., editor

Published
2006
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40. Recognition and Tracking of the Members of a Moving Human Body

Author

Panagiotakis, Costas, Tziritas, Georgios, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Perales, Francisco J., editor, and Draper, Bruce A., editor

Published
2004
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46. SURVEYING PARENTAL MEDIATION AND DIGITAL LITERACY. WERE PARENTS READY DURING COVID-19?

Author

Daskalaki, Evangelia, Panagiotakis, Costas, Papadakis, Harris, and Fragopoulou, Paraskevi

Subjects
*COMPUTER literacy, *COVID-19 pandemic, *DIGITAL technology, *SURVEYS, *AGE groups
Abstract

The pandemic initiated an extensive and sudden digital transformation in the society. It forced parents and children to take a digital surge in their lives. The aim of our survey is to explore to what extend children's online behavior has changed during the pandemic, to study whether demographic factors and digital literacy of parents, are associated with the changes observed, and lastly to explore to what extend parents are familiar with age and content classification systems online, which will allow them to make informed decisions about media content consumed by their children. The study reveals that a significant percentage of parents (29.8%) report changes in the online habits of their children. Furthermore, our research affirms that digital literacy of parents is the key to overcome potential online risks of children, especially during the pandemic. Notably, the age group 9-12 is the age group, which shows the biggest percentage of parents noticing changes in their child's online habits. Finally, it is revealed that parents were unprepared to follow this fast transformation pace, and only a low percentages of them appears to be familiar with age (49.8%) and content classification systems (27.9%) online. [ABSTRACT FROM AUTHOR]

Published
2022

47. Equivalent key frames selection based on Iso-Content principles

Author

Panagiotakis, Costas, Doulamis, Anastasios, and Tziritas, Georgios

Subjects
Digital video -- Analysis, Algorithms -- Analysis, Digital video, Algorithm, Business, Computers, Electronics, Electronics and electrical industries
Abstract

We present a key frames selection algorithm based on three iso-content principles (Iso-Content Distance, Iso-Content Error and Iso-Content Distortion), so that the selected key frames are equidistant in video content according to the used principle. Two automatic approaches for defining the most appropriate number of key frames are proposed by exploiting supervised and unsupervised content criteria. Experimental results and the comparisons with existing methods from literature on large dataset of real-life video sequences illustrate the high performance of the proposed schemata. Index Terms--Key frame selection, video-content representation, video summarization, equal distance principle.

Published
2009

49. Automatic P-phase picking based on local-maxima distribution

Author

Panagiotakis, Costas, Kokinou, Eleni, and Vallianatos, Filippos

Subjects
Algorithms -- Usage, Signal processing -- Methods, Seismic prospecting -- Methods, Reliability (Engineering) -- Evaluation, Algorithm, Digital signal processor, Business, Earth sciences, Electronics and electrical industries
Abstract

In this paper, we propose a method for the automatic identification of P-phase arrival based on the distribution of local maxima (LM) in earthquake seismograms. The method efficiently combines energy and frequency characteristics of the LM distribution (LMD). The P detection is mainly based on the energy of a seismic event in the case the earthquake has higher amplitude than seismic background noise. Otherwise, it is based on the frequency of LM. Thus, the method provides robust detection of P-phase arrival in any quality type of seismic data. Moreover, it uses two sequential sliding signal windows yielding very high accuracy on the P-phase estimation. A hierarchical P-phase detection algorithm dramatically reduces the computational cost, making possible a real-time implementation. Experimental results from a large database of more than 80 low, medium, and high signal-to-noise ratio seismic events and comparison with existing methods in the literature indicate the reliable performance of the proposed scheme. Index Terms--Automatic picking, P-phase arrival identification, seismic-signal analysis, signal segmentation.

Published
2008

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