263 Hits in 0.94 sec

Semantic query suggestion using Twitter Entities

Ioannis Anagnostopoulos, Gerasimos Razis, Phivos Mylonas, Christos-Nikolaos Anagnostopoulos
2015 Neurocomputing  
Anagnostopoulos et al. / Neurocomputing 163 (2015) 137-150  ...  Anagnostopoulos et al. / Neurocomputing 163 (2015) 137-150 7 8 9 10  ... 
doi:10.1016/j.neucom.2014.12.090 fatcat:iow4seggx5halouapbhftejynm

Semantifying Twitter: the influenceTracker ontology [article]

Gerasimos Razis, Ioannis Anagnostopoulos
2014 arXiv   pre-print
In this paper, we propose an ontology schema towards semantification provision of Twitter social analytics. The ontology is deployed over a publicly available service that measures how influential a Twitter account is, by combining its social activity and interaction over Twittersphere. Apart from influential quantity and quality measures, the service provides a SPARQL endpoint where users can perform advance semantic queries through the RDFized Twitter entities (mentions, replies, hashtags,
more » ... plies, hashtags, photos, URLs) over the semantic graph.
arXiv:1409.3771v1 fatcat:sgcnsh6lazgfpnnasbl5baphtu

Discovering similar Twitter accounts using semantics [article]

Gerasimos Razis, Ioannis Anagnostopoulos
2015 arXiv   pre-print
This fact has also been spotted by our work (Razis and Anagnostopoulos, 2014a) .  ...  In a previous work of ours (Razis and Anagnostopoulos, 2014b) we proposed an ontological schema towards semantification provision of Twitter analytics.  ... 
arXiv:1506.00100v1 fatcat:uk6kz7c42bhl5f6s7caakrhjhy

Tile Classification Using the CIELAB Color Model [chapter]

Christos-Nikolaos Anagnostopoulos, Athanassios Koutsonas, Ioannis Anagnostopoulos, Vassily Loumos, Eleftherios Kayafas
2005 Lecture Notes in Computer Science  
An image processing algorithm was developed for tile shade classification on the basis of quantitative measurements in CIELAB color space. A total of 50 tile images of 10 types were recorded, and evaluated with the proposed algorithm in comparison with the conventional classification method. The objectivity of the method is based on the fact that it is not subject to inter-and intra-observer variability arising from human's profile of competency in interpreting subjective and non-quantifiable
more » ... non-quantifiable descriptions.
doi:10.1007/11428831_86 fatcat:7daezi2vhrhbvfpkxhu2h3qts4

InfluenceTracker: Rating the impact of a Twitter account [article]

Gerasimos Razis, Ioannis Anagnostopoulos
2014 arXiv   pre-print
The authors in (Anagnostopoulos et al., 2008) also directly associate social influence with homophily, as it plays an important role that may induce the directly related users to behave in a similar  ... 
arXiv:1404.5239v1 fatcat:xukdxz2l2zandn3pkbgm5q4zyy

Steady state analysis of balanced-allocation routing [article]

Aris Anagnostopoulos, Ioannis Kontoyiannis, Eli Upfal
2002 arXiv   pre-print
We compare the long-term, steady-state performance of a variant of the standard Dynamic Alternative Routing (DAR) technique commonly used in telephone and ATM networks, to the performance of a path-selection algorithm based on the "balanced-allocation" principle; we refer to this new algorithm as the Balanced Dynamic Alternative Routing (BDAR) algorithm. While DAR checks alternative routes sequentially until available bandwidth is found, the BDAR algorithm compares and chooses the best among a
more » ... s the best among a small number of alternatives. We show that, at the expense of a minor increase in routing overhead, the BDAR algorithm gives a substantial improvement in network performance, in terms both of network congestion and of bandwidth requirement.
arXiv:math/0209357v1 fatcat:lm2nysdlpnfrtgmnouwyn3p36a

A methodology for internal Web ethics [article]

Michalis Vafopoulos, Petros Stefaneas, Ioannis Anagnostopoulos, Kieron O'Hara
2012 arXiv   pre-print
The vigorous impact of the Web in time and space arises from the fact that it motivates massive creation, editing and distribution of information by Users with little knowledge. This unprecedented continuum provides novel opportunities for innovation but also puts under jeopardy its survival as a stable construct that nurtures a complex system of connections. We examine the Web as an ethics determined space by demonstrating Hayek's theory of freedom in a three-leveled Web: technological,
more » ... chnological, contextualized and economic. Our approach accounts for the co-dependence of code and values, and assumes that the Web is a self-contained system that exists in and by itself. This view of internal Web ethics directly connects the concept of freedom with issues like centralization of traffic and data control, rights on visiting log file, custom User profiles and the interplay among function, structure and morality of the Web. It is also demonstrated, in the case of Net Neutrality, that generic freedom-coercion trade-offs are incomplete in treating specific cases at work.
arXiv:1202.4238v1 fatcat:l6p5h4rg6vbttpdtyv4us3bnw4

Intracranial meningioma in a patient with osteogenesis imperfecta

Parmenion Tsitsopoulos, Ioannis Anagnostopoulos, Vasileios Tsitouras, Ioannis Venizelos, Philippos Tsitsopoulos
2008 Open Medicine  
AbstractOsteogenesis imperfecta (OI) is a heritable disorder characterized mainly by connective tissue manifestations. In dinstinct cases, several neurological features have also been described. A 46-year-old male with a known family history of OI type I presented with progressive gait disturbances and diminished muscle strength. Brain MRI scans revealed an infiltrative intracranial mass occupying both frontoparietal lobes. The patient underwent surgical intervention. The histological diagnosis
more » ... tological diagnosis was an atypical (Grade II) meningioma. The bony parts demonstrated a mixture of osseous defects due to OI and infiltration by the tumor. At one-year follow up the patient′s muscle power partially returned while repeat MRI scans were negative for tumor recurrence.
doi:10.2478/s11536-008-0053-7 fatcat:3w4tloxxtvdfxlc6t7xqdanhdm

Randomized embeddings with slack, and high-dimensional Approximate Nearest Neighbor [article]

Evangelos Anagnostopoulos, Ioannis Z. Emiris, Ioannis Psarros
2016 arXiv   pre-print
The approximate nearest neighbor problem (ϵ-ANN) in high dimensional Euclidean space has been mainly addressed by Locality Sensitive Hashing (LSH), which has polynomial dependence in the dimension, sublinear query time, but subquadratic space requirement. In this paper, we introduce a new definition of "low-quality" embeddings for metric spaces. It requires that, for some query point q, there exists an approximate nearest neighbor among the pre-images of the k>1 approximate nearest neighbors in
more » ... earest neighbors in the target space. Focusing on Euclidean spaces, we employ random projections in order to reduce the original problem to one in a space of dimension inversely proportional to k. The k approximate nearest neighbors can be efficiently retrieved by a data structure such as BBD-trees. The same approach is applied to the problem of computing an approximate near neighbor, where we obtain a data structure requiring linear space, and query time in O(d n^ρ), for ρ≈ 1-ϵ^2/(1/ϵ). This directly implies a solution for ϵ-ANN, while achieving a better exponent in the query time than the method based on BBD-trees. Better bounds are obtained in the case of doubling subsets of ℓ_2, by combining our method with r-nets. We implement our method in C++, and present experimental results in dimension up to 500 and 10^6 points, which show that performance is better than predicted by the analysis. In addition, we compare our ANN approach to E2LSH, which implements LSH, and we show that the theoretical advantages of each method are reflected on their actual performance.
arXiv:1412.1683v2 fatcat:xb2ev5ctzveetgdvwm5ljszava

Algorithms for Deciding Membership in Polytopes of General Dimension [article]

Evangelos Anagnostopoulos, Ioannis Z. Emiris, Vissarion Fisikopoulos
2018 arXiv   pre-print
We study the fundamental problem of polytope membership aiming at large convex polytopes, i.e. in high dimension and with many facets, given as an intersection of halfspaces. Standard data-structures as well as brute force methods cannot scale, due to the curse of dimen- sionality. We design an efficient algorithm, by reduction to the approx- imate Nearest Neighbor (ANN) problem based on the construction of a Voronoi diagram with the polytope being one bounded cell. We thus trade exactness for
more » ... rade exactness for efficiency so as to obtain complexity bounds polyno- mial in the dimension, by exploiting recent progress in the complexity of ANN search. We employ this algorithm to present a novel boundary data structure based on a Newton-like iterative intersection procedure. We implement our algorithms and compare with brute-force approaches to show that they scale very well as the dimension and number of facets grow larger.
arXiv:1804.11295v1 fatcat:ysagebqr7zcqdkjcphatsdydka

vhMentor: An Ontology Supported Mobile Agent System for Pervasive Health Care Monitoring [chapter]

Stella C. Christopoulou, Theodore Kotsilieris, Ioannis Anagnostopoulos, Christos-Nikolaos Anagnostopoulos, Phivos Mylonas
2017 Advances in Experimental Medicine and Biology  
Healthcare provision is a set of activities that demands the collaboration of several stakeholders (e.g. physicians, nurses, managers, patients etc.) who hold distinct expertise and responsibilities. In addition, medical knowledge is diversely located and often shared under no central coordination and supervision authority, while medical data flows remain mostly passive regarding the way data is delivered to both clinicians and patients. In this paper, we propose the implementation of a virtual
more » ... tation of a virtual health Mentor (vhMentor) which stands as a dedicated ontology schema and FIPA compliant agent system. Agent technology proves to be ideal for developing healthcare applications due to its distributed operation over systems and data sources of high heterogeneity. Agents are able to perform their tasks by acting pro-actively in order to assist individuals to overcome limitations posed during accessing medical data and executing nonautomatic error-prone processes. vhMentor further comprises the Jess rules engine in order to implement reasoning logic. Thus, on the one hand vhMentor is a prototype that fills the gap between healthcare systems and the care provision community, while on the other hand allows the blending of next generation distributed services in healthcare domain.
doi:10.1007/978-3-319-57348-9_5 pmid:28971416 fatcat:jsobdlh2mnedlcaxh7cy6nbeqm

The Wisconsin breast cancer problem: Diagnosis and TTR/DFS time prognosis using probabilistic and generalised regression information classifiers

Ioannis Anagnostopoulos, Christos Anagnostopoulos, Dimitrios Vergados, Angelos Rouskas, George Kormentzas
2006 Oncology Reports  
This study addresses the breast cancer diagnosis and prognosis problem by employing two neural network architectures with the Wisconsin diagnostic and prognostic breast cancer (WDBC/WPBC) datasets. A probabilistic approach is dedicated to solve the diagnosis problem, detecting malignancy among cases (instances) as derived from fine needle aspirate (FNA) tests, while the second architecture estimates the time interval that possibly contains the right endpoint of disease-free survival (DFS) of
more » ... urvival (DFS) of the patient. The accuracy of the neural classifiers reaches nearly 98% for the diagnosis and 93% for the prognosis problem, while the prognostic recurrence predictions were evaluated using survival analysis through the Kaplan-Meier approximation method. Both architectures were compared with other similar approaches. The robustness and real-time response of the proposed classifiers were further tested over the web as a potential integrated web-based decision support system.
doi:10.3892/or.15.4.975 fatcat:jgjc67b6cfagpizwr3l6kjxxwa

Public Spending as LOD: The Case of Greece

Michalis N. Vafopoulos, Marios Meimaris, Ioannis Anagnostopoulos, Agis Papantoniou, Ioannis Xidias, Giorgos Alexiou, Giorgos Vafeiadis, Michailis Klonaras, Vasilis Loumos
2013 Social Science Research Network  
The PSGR project is the first attempt to generate, curate, interlink and distribute daily updated public spending data in LOD formats that can be useful to both expert (i.e. scientists and professionals) and naïve users. The PSGR ontology is based on the UK payments ontology and reuses, among others, the W3C Registered Organization Vocabulary and the Core Business Vocabulary. RDFized data are linked to product classifications, Geonames and DBpedia resources. Online services contain advanced
more » ... ontain advanced search features and domain level information (e.g. local government), simple and complex visualizations based on network analysis, linked information about payment entities and SPARQL endpoints. During February 2013, the growing dataset consists of approximately 2 mil. payment decisions valued 44,5 bil. euros forming 65 mil. triples.
doi:10.2139/ssrn.2233998 fatcat:7lurxei5erhp3pqh3hbthni5oi

Evaluation of Diversification Techniques for Legal Information Retrieval

Marios Koniaris, Ioannis Anagnostopoulos, Yannis Vassiliou
2017 Algorithms  
Ioannis Anagnostopoulos analyzed the results, helped to draft the initial manuscript and revised the final version. Yannis Vassiliou provided feedback and revised the final manuscript.  ... 
doi:10.3390/a10010022 fatcat:tlp2bw4odjhsdmo5fn47tzqhou

Viral content propagation in Online Social Networks [article]

Giannis Haralabopoulos, Ioannis Anagnostopoulos, Sherali Zeadally
2018 arXiv   pre-print
Information flows are the result of a constant exchange in Online Social Networks (OSNs). OSN users create and share varying types of information in real-time throughout a day. Virality is introduced as a term to describe information that reaches a wide audience within a small time-frame. As a case, we measure propagation of information submitted in Reddit, identify different patterns and present a multi OSN diffusion analysis on Twitter, Facebook, and 2 hosting domains for images and
more » ... mages and multimedia, ImgUr and YouTube. Our results indicate that positive content is the most shared and presents the highest virality probability, and the overall virality probability of user created information is low. Finally, we underline the problems of limited access in OSN data. Keywords: Online Social Networks, Virality, Diffusion, Viral Content, Reddit, Twitter, Facebook, ImgUr, YouTube
arXiv:1712.02245v2 fatcat:dtfw34eolngorg2dibvmpffif4
« Previous Showing results 1 — 15 out of 263 results