Institution
University of Piraeus
Education•Piraeus, Attiki, Greece•
About: University of Piraeus is a education organization based out in Piraeus, Attiki, Greece. It is known for research contribution in the topics: Context (language use) & Computer science. The organization has 1731 authors who have published 6209 publications receiving 106699 citations.
Papers published on a yearly basis
Papers
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TL;DR: A method for trajectory segmentation and sampling based on the representativeness of the (sub)trajectories in the MOD is proposed, and the effectiveness of the proposed scheme is verified in comparison with other sampling techniques.
Abstract: Moving Object Databases (MOD), although ubiquitous, still call for methods that will be able to understand, search, analyze, and browse their spatiotemporal content. In this paper, we propose a method for trajectory segmentation and sampling based on the representativeness of the (sub)trajectories in the MOD. In order to find the most representative subtrajectories, the following methodology is proposed. First, a novel global voting algorithm is performed, based on local density and trajectory similarity information. This method is applied for each segment of the trajectory, forming a local trajectory descriptor that represents line segment representativeness. The sequence of this descriptor over a trajectory gives the voting signal of the trajectory, where high values correspond to the most representative parts. Then, a novel segmentation algorithm is applied on this signal that automatically estimates the number of partitions and the partition borders, identifying homogenous partitions concerning their representativeness. Finally, a sampling method over the resulting segments yields the most representative subtrajectories in the MOD. Our experimental results in synthetic and real MOD verify the effectiveness of the proposed scheme, also in comparison with other sampling techniques.
94 citations
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01 Jul 2009
TL;DR: It is shown that the proposed scheme can be efficiently and effectively applied for medical image retrieval from large databases, providing unsupervised semantic interpretation of the results, which can be further extended by knowledge representation methodologies.
Abstract: In this paper, we propose a novel scheme for efficient content-based medical image retrieval, formalized according to the PAtterns for Next generation DAtabase systems (PANDA) framework for pattern representation and management. The proposed scheme involves block-based low-level feature extraction from images followed by the clustering of the feature space to form higher-level, semantically meaningful patterns. The clustering of the feature space is realized by an expectation-maximization algorithm that uses an iterative approach to automatically determine the number of clusters. Then, the 2-component property of PANDA is exploited: the similarity between two clusters is estimated as a function of the similarity of both their structures and the measure components. Experiments were performed on a large set of reference radiographic images, using different kinds of features to encode the low-level image content. Through this experimentation, it is shown that the proposed scheme can be efficiently and effectively applied for medical image retrieval from large databases, providing unsupervised semantic interpretation of the results, which can be further extended by knowledge representation methodologies.
94 citations
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TL;DR: The first stage results indicate a decline in efficiency over the sample period, while the second stage results confirm that the competition for market shares is a major driver of efficiency in the Greek insurance industry.
93 citations
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TL;DR: This paper introduces an approach based on interval DEA that allows the evaluation of the units with missing values along with the other units with available crisp data and estimates new values for the initial interval bounds that may turn the unit to an efficient one.
93 citations
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TL;DR: In this paper, the authors examined human reliability with reference to all accidents involving Greek-flagged ships during 1993-2006, a time-scale that spans over the pre- and post-ISM period.
93 citations
Authors
Showing all 1766 results
Name | H-index | Papers | Citations |
---|---|---|---|
Nicholas Apergis | 56 | 445 | 14876 |
Natalia Andrienko | 52 | 253 | 11239 |
Yannis Theodoridis | 47 | 223 | 9426 |
Marianna Sigala | 44 | 218 | 7458 |
George P. Patrinos | 43 | 353 | 8785 |
Abbas Jamalipour | 43 | 518 | 11332 |
Anastasios Tselepides | 40 | 78 | 4948 |
Stefanos Gritzalis | 40 | 312 | 5425 |
Stefan Schwarz | 37 | 209 | 4544 |
Demetrios G. Sampson | 36 | 306 | 4886 |
Christos Douligeris | 36 | 347 | 4835 |
Alexander Artikis | 35 | 158 | 3217 |
Michael H. Neumann | 34 | 105 | 3415 |
Ilias Maglogiannis | 33 | 273 | 4810 |
Gregoris Mentzas | 32 | 257 | 4293 |