Διεθνές Πανεπιστήμιο της Ελλάδος :: Πλοήγηση Ερευνητικές - Επιστημονικές Δημοσιεύσεις/ Scientific Publications ανά Τίτλο

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500 σημεία της πόλης, μία απάντηση : theveriagrid

(2006) Γαρουφάλλου, Εμμανουήλ; Garoufallou, Emmanouel

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7th metadata and semantic research conference

(2013) Garoufallou, Emmanouel; Γαρουφάλλου, Εμμανουήλ

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A brave new world for libraries : the sui generis right

(2013-06-03T10:48:46Z) Konsta, Rania; Gerolimos, Michalis; Γερόλιμος, Μιχάλης; Κώνστα, Ράνια

The ways in which databases1 affect, within a modern information environment, scientific communication, the exchange of ideas among peers, as well as the search and retrieval of information by any potential user through a commercial and financial framework that is still being shaped, has led the European Union the creation of the sui generis right (special right), through which it is the first time ever to establish a copyright on information (EU Directive 96/9/EC).

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A class probability distributions in risk insurance

(ΕΜΕ, 1996) Σαμαθρακής, Βαγής; Samathrakis, Vagis

Εισαγωγή στοχαστικού μοντέλου με εφαρμογές στις τεχνικές μείωσης του κινδύνου

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A classification of the solutions of non-regular, discrete-time descriptor systems

(IEEE, 1997-12) Antoniou, Efstathios; Karampetakis, Nikolas; Vardulakis, Antonis; Καραμπετάκης, Νικόλαος; Βαρδουλάκης, Αντώνης; Αντωνίου, Ευστάθιος

A classification of the solutions of linear, time invariant non-regular, discrete descriptor systems is given in terms of the structural invariant of the associated matrix pencil σE-A. The lack of conditionability (in the general case) implies a partitioning of the behavior and thus a classification of the solution according to their boundary values.

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A combined computational and experimental investigation of nonthermal biological effects on prenatal development due to radiation from low power microwave antennas

(2015-07-08T09:27:12Z) Karkavelas, Georgios; Kosmidou, Elisavet; Zygiridis, Theodoros; Yioultsis, Traianos; Tsiboukis, Theodoros; Xenos, Thomas; Pyrpasopoulou, Athina; Kosmanis, Theodoros; Magras, I.; Hytiroglou, P.; Farsaris, N.; Kotoula, V.; Πυρπασοπούλου, Αθηνά; Φαρσάρης, Ν.; Καρκαβέλας, Γεώργιος; Μαγράς, Ι.; Χυτήρογλου, Π.; Κοτούλα, Β.; Τσιμπούκης, Θεόδωρος; Κοσμάνης, Θεόδωρος; Γιούλτσης, Τραϊανός; Ζυγκιρίδης, Θεόδωρος; Ξένος, Θωμάς

This is an integrated study of the biological effects of pulse-modulated very low power density microwave radiation. It employs a combination of a computational model of the rat and extensive in vivo experiments on rat embryos, during embryogenesis and organogenesis. The whole investigation is further enhanced via an immunological and chemical investigation of the rats' organs. The whole study is one of the first to combine results obtained by the computational, the experimental and the biomolecular investigations and attempts a discussion on existing standards for protection from low power density, long-term electromagnetic field exposure.

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A common sense approach to defining data, information, and metadata

(2006-06) Δέρβος, Δημήτριος; Coleman, Anita-Sundaram; Swertz, C.; Budin, G.; Dervos, Dimitrios

Many competing definitions for the terms data, information, metadata, and knowledge can be traced in the library and information science literature. The lack of a clear consensus in the way reference is made to the corresponding fundamental concepts is intensified if one considers additional disciplinary perspectives, e.g. database technology, data mining, etc. In the present paper, we use a common sense approach borrowed from the data mining community, which has successfully solved many data processing problems, to selectively survey the literature, and define these terms in a way that can advance the interdisciplinary development of information systems.

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A comparative FDTD study of various PML configurations for the termination of nonlinear photonic bandgap waveguide structures

(IEEE, 2003-05) Kosmidou, Elisavet; Tsiboukis, Theodoros; Kosmanis, Theodoros; Κοσμάνης, Θεόδωρος; Τσιμπούκης, Θεόδωρος; Κοσμίδου, Ελισάβετ

A comparative investigation of high-performance PML absorbers for the termination of 2-D nonlinear photonic bandgap (PBG) waveguides, analyzed by the FDTD method, is conducted. Third-order nonlinear materials are considered, whereas existing effective permittivity schemes are properly implemented for the modeling of circular interfaces between linear and nonlinear media.

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A comparative study of international and Greek search engines

(2011) Garoufallou, Emmanouel; Γαρουφάλλου, Εμμανουήλ

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A comparative study of international and Greek search engines

(2011) Garoufallou, Emmanouel; Γαρουφάλλου, Εμμανουήλ

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A comparative study of the biological effects of various mobile phone wireless LAN antennas

(IEEE, 2002-03) Kosmanis, Theodoros; Kantartzis, Nikolaos; Tsiboukis, Theodoros; Xenos, Thomas; Yioultsis, Traianos; Kosmidou, Elisavet; Zygiridis, Theodoros; Ζυγκιρίδης, Θεόδωρος; Κανταρτζής, Νικόλαος; Γιούλτσης, Τραϊανός; Ξένος, Θωμάς; Κοσμάνης, Θεόδωρος; Κοσμίδου, Ελισάβετ; Τσιμπούκης, Θεόδωρος

This paper presents a comprehensive electromagnetic and thermal analysis of radiation and its impact on human beings, due to the use of various types of commonly used mobile phones and communication antennas. This is one of the first studies that deals with a wide-range comparative investigation of modern cell phones, unlike the majority of existing work, which do not extend beyond the obsolete generic phone case. The rather severe, although overlooked, case of wireless local area network antennas is also considered, due to their increasing use and the large times of exposure associated with them. Index Terms Biological application of electromagnetic radiation, electromagnetic radiation effects, FDTD methods, mobile antennas

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A conformal FDTD algorithm for the simulation of curved dielectric interfaces in three-dimensional grids

(IOS Press, 2002) Tsiboukis, Theodoros; Kosmanis, Theodoros; Κοσμάνης, Θεόδωρος; Τσιμπούκης, Θεόδωρος

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A conformally-oriented FDTD methodology for the accurate simulation of arbitrarily-angled wedges in general rectangular or curvilinear waveguide structures and shielded microstrips

(ISEF, 1999-09) Kosmanis, Theodoros; Tsiboukis, Theodoros; Kantartzis, Nikolaos; Τσιμπούκης, Θεόδωρος; Κοσμάνης, Θεόδωρος; Κανταρτζής, Νικόλαος

A new locally implemented methodology for the accurate representation of field singularities caused by abrupt corners that are present inside waveguides and shielded microstrip lines is proposed in this paper. The novel technique, manipulating the conformal finite-difference time-domain (FDTD) method, also deals with non-Cartesian structures, containing inclined and curved interfaces. The numerical computation of cut-off frequencies of various curvilinear waveguide and shielded microstrip structures, with perfectly contacting wedges, proves the efficiency of the proposed scheme.

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A critical introduction to metadata for e-science and e-research

(Inderscience Enterprises Ltd, 2014-01) Papatheodorou, Christos; Garoufallou, Emmanouel; Γαρουφάλλου, Εμμανουήλ; Παπαθεοδώρου, Χρήστος

Scientific research is moving towards multi-disciplinary, multi-institutional collaboration and therefore powerful tools and infrastructures based on interoperability principles are needed to support this trend. This paper introduces the special issue on the metadata for e-science and e-research of the International Journal on Metadata, Semantics and Ontologies. This special issue seeks to draw attention to the on-going challenges that scientists and systems developers face in the area of metadata and data management for e-science and e-research. In particular, the objectives of this special issue are (a) to present some of the latest research in this field, especially in relation to the use of metadata for addressing challenges associated with the management of scientific and research data across a broad range of applications; and (b) to highlight some of the challenges associated with the use of metadata, and encourage further research in this area. The special issue includes four papers reporting innovative approaches to key issues in the area of metadata for e-science and e-research, such as metadata modelling and standardisation, data quality and data re-use.

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A Descriptor Systems Package for Mathematica

(2003) Antoniou, Efstathios; Tzekis, P.; Vologiannidis, Stavros; Vardulakis, Antonis; Karampetakis, Nikolas; Καραμπετάκης, Νικόλαος; Αντωνίου, Ευστάθιος; Τζέκης, Π.; Βολογιαννίδης, Σταύρος; Βαρδουλάκης, Αντώνης

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A Fault Diagnosis Expert System Structure with Knowledge Retrieving Capability from Waveforms

(2005-10) Papakostas, Dimitrios; Hatzopoulos, Alkiviadis; Παπακώστας, Δημήτριος; Χατζόπουλος, Αλκιβιάδης

Analogue fault diagnosis can be addressed by expert systems using artificial intelligence methodologies. The structure of such an expert system and its main features are presented in this paper. As a special feature, knowledge which is obtained through the waveforms of specific parameters of the circuit under test is presented. Techniques for comparison between waveforms and conclusion extraction are described. Demonstrative examples of fault location using the expert system are given.

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A framework for the ex-ante evaluation of ERP software

(Palgrave Macmillan, 2001) Stefanou, Constantinos; Στεφάνου, Κωνσταντίνος

It has been widely reported that a large number of ERP implementations fail to meet expectations. This is indicative, firstly, of the magnitude of the problems involved in ERP systems implementation and, secondly, of the importance of the ex-ante evaluation and selection process of ERP software. This paper argues that ERP evaluation should extend its scope beyond operational improvements arising from the ERP software/product per se to the strategic impact of ERP on the competitive position of the organisation. Due to the complexity of ERP software, the intangible nature of both costs and benefits, which evolve over time, and the organisational, technological and behavioural impact of ERP, a broad perspective of the ERP systems evaluation process is needed. The evaluation has to be both quantitative and qualitative and requires an estimation of the perceived costs and benefits throughout the life-cycle of ERP systems. The paper concludes by providing a framework of the key issues involved in the selection process of ERP software and the associated costs and benefits.

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A framework of CRM development phases and key success factors

(2015-07-03T08:12:58Z) Sarmaniotis, Christos; Stefanou, Constantinos; Σαρμανιώτης, Χρήστος; Στεφάνου, Κωνσταντίνος

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A generalized methodology based on higher-order conventional and non-standard FDTD concepts for the systematic development of enhanced dispersionless wide-angle absorbing perfectly matched layers

(2015-07-09T09:29:24Z) Kosmanis, Theodoros; Kantartzis, Nikolaos; Tsiboukis, Theodoros; Κοσμάνης, Θεόδωρος; Κανταρτζής, Νικόλαος; Τσιμπούκης, Θεόδωρος

A generalized theory of higher-order finite-difference time-domain (FDTD) schemes for the construction of new dispersionless Berenger and Maxwellian unsplit-field perfectly matched layers (PMLs), is presented in this paper. The technique incorporates both conventional and non-standard approximating concepts. Superior accuracy and modelling attributes are further attained by biasing the FDTD increments on generalizations of Padé formulae and derivative definitions. For the inevitably widened spatial stencils, we adopt the compact operators procedure, whereas temporal integration is alternatively performed via the four-stage Runge–Kutta integrator. In order to terminate the PML outer boundaries and decrease the absorber's necessary thickness, various higher-order lossy absorbing boundary conditions (ABCs) are implemented. Based on the previous theory, we finally introduce an enhanced reflection-annihilating PML for wide-angle absorption. The novel unsplit-field PML has a non-diagonal symmetric complex tensor anisotropy and by an appropriate choice of its parameters together with new conductivity profiles, it can successfully absorb waves of grazing incidence, thus allowing its imposition much closer to electrically large structures. Numerical results reveal that the proposed 2- and 3-D PMLs suppress dispersion and anisotropy errors, alleviate the near-grazing incidence effect and achieve significant savings in the overall computational resources. Copyright © 2000 John Wiley & Sons, Ltd.

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A hybrid FDTD-wavelet-Galerkin technique for the numerical analysis of field singularities inside waveguides

(IEEE, 2000-08-06) Tsiboukis, Theodoros; Kantartzis, Nikolaos; Kosmanis, Theodoros; Κοσμάνης, Θεόδωρος; Τσιμπούκης, Θεόδωρος; Κανταρτζής, Νικόλαος

A novel hybrid finite difference time domain-wavelet-Galerkin (FDTD-WG) technique is presented for the accurate representation of electromagnetic field solutions in regions of fast field transitions. Its fundamental concept lies in the combination of the robust FDTD method with the wavelet-Galerkin formulation, which in its turn can efficiently treat highly varying phenomena. The computational domain is, therefore, divided into regions of smooth and fast field variations. Proper determination of these two areas leads to improved simulations and significantly reduced computational burden, turning the proposed scheme into a powerful tool. Numerical results derived from the manipulation of various waveguides, proves the validity and efficacy of the new scheme

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Πλοήγηση Ερευνητικές - Επιστημονικές Δημοσιεύσεις/ Scientific Publications ανά Τίτλο