110 research outputs found
Study of ad hoc networks
No full textThe object of this dissertation is the study of ad hoc networks. As ad hoc are characterised the wireless networks that are not supported by preexisting infrastructure. This study focuses on two layers of the ISO/OSI networking stack and namely the data link and the network layer. The behaviour of the medium access protocol EY-NPMA was studied via both analytical and numerical means. Aiming at improving the efficiency, two protocols based on EY-NPMA have been designed (EY-NPMA/TP and EY-NPMA/ZP), which allow the dynamic upgrading of the priority levels of a subset of the network population. Also, a mechanism for estimating the offered load was designed and evaluated, allowing the network to use the optimal working parameters of the EY-NPMA protocol (Adaptive EY-NPMA). Adaptive EY-NPMA with variable yield further improves the protocol efficiency by allowing the interaction between the elimination and the yield phases. Finally, the performance of the EDCF medium access protocol was evaluated using numerical methods, while it was also compared with EY-NPMA and EY-NPMA/ZP. In the network layer, the research focused on the problem of routing. Using numerical methods, the value of distributed gateways was quantified in a clustered ad hoc network, while a medium access protocol which enables their usage was designed and evaluated. Also, the SNLSR routing protocol was proposed, which uses sequence numbers in order to reduce the transmission of redundant topology information in the network.Αντικείμενο αυτής της διδακτορικής διατριβής αποτελεί η μελέτη των αδόμητων δικτύων. Ως αδόμητα ορίζονται τα ασύρματα δίκτυα που δεν υποστηρίζονται από προϋπάρχουσα υποδομή. Η μελέτη εστιάζεται σε δύο επίπεδα του μοντέλου ISO/OSI, του επιπέδου ζεύξης και του επιπέδου δικτύου. Στα πλαίσια της διατριβής μελετήθηκε η συμπεριφορά του πρωτοκόλλου πολλαπλής πρόσβασης EY-NPMA, τόσο μέσω αναλυτικών όσο και μέσω αριθμητικών μεθόδων. Με στόχο την βελτίωση της αποδοτικότητας, σχεδιάστηκαν δύο πρωτόκολλα που βασίζονται στο EY-NPMA (EY-NPMA/TP και EY-NPMA/ZP) τα οποία επιτρέπουν την δυναμική αναβάθμιση της προτε- ραιότητας μέρους του δικτυακού πληθυσμού. Επίσης, μελετήθηκε μηχανισμός εκτίμησης του προσφερόμενου φορτίου, ώστε να επιλέγει το EY-NPMA τις βέλτιστες παραμέτρους λειτουργίας σε κάθε περίσταση (προσαρμοστικό EY-NPMA). Το προσαρμοστικό EY-NPMA με μεταβλητή αποκομιδή βελτιώνει περαιτέρω την αποδοτικότητα του πρωτοκόλλου, επιτρέποντας την αλληλε- πίδραση μεταξύ των φάσεων απαλοιφής και αποκομιδής. Τέλος, μέσω προσομοιώσεων αξιολο- γήθηκε η απόδοση του πρωτοκόλλου πολλαπλής πρόσβασης EDCF, ενώ συγκρίθηκε επίσης με τα EY-NPMA και EY-NPMA/ZP. Στο επίπεδο δικτύου, η έρευνα εστίασε στο πρόβλημα της δρομο- λόγησης. Χρησιμοποιώντας αριθμητικές μεθόδους ποσοτικοποιήθηκε η σημασία των κατανεμη- μένων πυλών σε ένα κυψελοποιημένο δίκτυο, ενώ προτάθηκε πρωτόκολλο πολλαπλής πρόσβασης που επιτρέπει την ενεργοποίησή τους. Επίσης, προτάθηκε και αξιολογήθηκε το πρωτόκολλο δρομολόγησης για αδόμητα δίκτυα SNLSR, το οποίο χρησιμοποιεί τους αριθμούς ακολουθίας για την μείωση της πλεονάζουσας πληροφορίας τοπολογίας που εκπέμπεται στο δίκτυο
gCube 4.1.1 - resourceregistry-configuration-default v. 1.0.2
No full text<p>
The gCube System - resourceregistry-configuration-default<br>
--------------------------------------------------<br>
<br>
ResourceRegistry configuration default<br>
<br>
<br>
This software is part of the gCube Framework (https://www.gcube-system.org/): an<br>
open-source software toolkit used for building and operating Hybrid Data<br>
Infrastructures enabling the dynamic deployment of Virtual Research Environments<br>
by favouring the realisation of reuse oriented policies.<br>
<br>
The projects leading to this software have received funding from a series of <br>
European Union programmes including: <br>
* the Sixth Framework Programme for Research and Technological Development - <br>
DILIGENT (grant no. 004260); <br>
* the Seventh Framework Programme for research, technological development and <br>
demonstration - D4Science (grant no. 212488), D4Science-II (grant no. <br>
239019),ENVRI (grant no. 283465), EUBrazilOpenBio (grant no. 288754), iMarine <br>
(grant no. 283644); <br>
* the H2020 research and innovation programme - BlueBRIDGE (grant no. 675680), <br>
EGIEngage (grant no. 654142), ENVRIplus (grant no. 654182), Parthenos (grant <br>
no. 654119), SoBigData (grant no. 654024);<br>
<br>
<br>
Version<br>
--------------------------------------------------<br>
<br>
1.0.2-4.1.1-125842 (2016-12-15)<br>
<br>
Please see the file named "changelog.xml" in this directory for the release notes.<br>
<br>
<br>
Authors<br>
--------------------------------------------------<br>
<br>
* Gerasimos Farantatos (g.farantatos-AT-di.uoa.gr), University of Athens, <br>
Department of Informatics and Telecommunications.<br>
<br>
* Second author Alexandros Antoniadis (a.antoniadis-AT-di.uoa.gr), University of Athens, <br>
Department of Informatics and Telecommunications.<br>
<br>
Maintainers<br>
-----------<br>
<br>
* Gerasimos Farantatos (g.farantatos-AT-di.uoa.gr), University of Athens, <br>
Department of Informatics and Telecommunications.<br>
<br>
* Second author Alexandros Antoniadis (a.antoniadis-AT-di.uoa.gr), University of Athens, <br>
Department of Informatics and Telecommunications.<br>
<br>
<br>
Download information<br>
--------------------------------------------------<br>
<br>
Source code is available from SVN: <br>
http://svn.research-infrastructures.eu/public/d4science/gcube/branches/resource-registry/ResourceRegistry-configuration-default/1.0/ResourceRegistry-configuration-default<br>
<br>
Binaries can be downloaded from the gCube website: <br>
https://www.gcube-system.org/<br>
<br>
<br>
Installation<br>
--------------------------------------------------<br>
<br>
Installation documentation is available on-line in the gCube Wiki:<br>
https://wiki.gcube-system.org/gcube/index.php<br>
<br>
Documentation <br>
-------------<br>
Documentation is available on-line in the gCube Wiki:<br>
https://gcube.wiki.gcube-system.org/gcube/index.php/Resource_Registry<br>
<br>
Support <br>
--------------------------------------------------<br>
<br>
Bugs and support requests can be reported in the gCube issue tracking tool:<br>
https://support.d4science.org/projects/gcube/<br>
<br>
<br>
Licensing<br>
--------------------------------------------------<br>
<br>
This software is licensed under the terms you may find in the file named "LICENSE" in this directory.<br>
</p>
gCube 4.2.0 - resourceregistry-configuration-default v. 1.0.2
No full text<p>
The gCube System - resourceregistry-configuration-default<br>
--------------------------------------------------<br>
<br>
ResourceRegistry configuration default<br>
<br>
<br>
This software is part of the gCube Framework (https://www.gcube-system.org/): an<br>
open-source software toolkit used for building and operating Hybrid Data<br>
Infrastructures enabling the dynamic deployment of Virtual Research Environments<br>
by favouring the realisation of reuse oriented policies.<br>
<br>
The projects leading to this software have received funding from a series of <br>
European Union programmes including: <br>
* the Sixth Framework Programme for Research and Technological Development - <br>
DILIGENT (grant no. 004260); <br>
* the Seventh Framework Programme for research, technological development and <br>
demonstration - D4Science (grant no. 212488), D4Science-II (grant no. <br>
239019),ENVRI (grant no. 283465), EUBrazilOpenBio (grant no. 288754), iMarine <br>
(grant no. 283644); <br>
* the H2020 research and innovation programme - BlueBRIDGE (grant no. 675680), <br>
EGIEngage (grant no. 654142), ENVRIplus (grant no. 654182), Parthenos (grant <br>
no. 654119), SoBigData (grant no. 654024);<br>
<br>
<br>
Version<br>
--------------------------------------------------<br>
<br>
1.0.2-4.2.0-125842 (2016-12-16)<br>
<br>
Please see the file named "changelog.xml" in this directory for the release notes.<br>
<br>
<br>
Authors<br>
--------------------------------------------------<br>
<br>
* Gerasimos Farantatos (g.farantatos-AT-di.uoa.gr), University of Athens, <br>
Department of Informatics and Telecommunications.<br>
<br>
* Second author Alexandros Antoniadis (a.antoniadis-AT-di.uoa.gr), University of Athens, <br>
Department of Informatics and Telecommunications.<br>
<br>
Maintainers<br>
-----------<br>
<br>
* Gerasimos Farantatos (g.farantatos-AT-di.uoa.gr), University of Athens, <br>
Department of Informatics and Telecommunications.<br>
<br>
* Second author Alexandros Antoniadis (a.antoniadis-AT-di.uoa.gr), University of Athens, <br>
Department of Informatics and Telecommunications.<br>
<br>
<br>
Download information<br>
--------------------------------------------------<br>
<br>
Source code is available from SVN: <br>
http://svn.research-infrastructures.eu/public/d4science/gcube/branches/resource-registry/ResourceRegistry-configuration-default/1.0/ResourceRegistry-configuration-default<br>
<br>
Binaries can be downloaded from the gCube website: <br>
https://www.gcube-system.org/<br>
<br>
<br>
Installation<br>
--------------------------------------------------<br>
<br>
Installation documentation is available on-line in the gCube Wiki:<br>
https://wiki.gcube-system.org/gcube/index.php<br>
<br>
Documentation <br>
-------------<br>
Documentation is available on-line in the gCube Wiki:<br>
https://gcube.wiki.gcube-system.org/gcube/index.php/Resource_Registry<br>
<br>
Support <br>
--------------------------------------------------<br>
<br>
Bugs and support requests can be reported in the gCube issue tracking tool:<br>
https://support.d4science.org/projects/gcube/<br>
<br>
<br>
Licensing<br>
--------------------------------------------------<br>
<br>
This software is licensed under the terms you may find in the file named "LICENSE" in this directory.<br>
</p>
gCube 4.3.0 - resourceregistry-configuration-default v. 1.0.2
No full text<p>
The gCube System - resourceregistry-configuration-default<br>
--------------------------------------------------<br>
<br>
ResourceRegistry configuration default<br>
<br>
<br>
This software is part of the gCube Framework (https://www.gcube-system.org/): an<br>
open-source software toolkit used for building and operating Hybrid Data<br>
Infrastructures enabling the dynamic deployment of Virtual Research Environments<br>
by favouring the realisation of reuse oriented policies.<br>
<br>
The projects leading to this software have received funding from a series of <br>
European Union programmes including: <br>
* the Sixth Framework Programme for Research and Technological Development - <br>
DILIGENT (grant no. 004260); <br>
* the Seventh Framework Programme for research, technological development and <br>
demonstration - D4Science (grant no. 212488), D4Science-II (grant no. <br>
239019),ENVRI (grant no. 283465), EUBrazilOpenBio (grant no. 288754), iMarine <br>
(grant no. 283644); <br>
* the H2020 research and innovation programme - BlueBRIDGE (grant no. 675680), <br>
EGIEngage (grant no. 654142), ENVRIplus (grant no. 654182), Parthenos (grant <br>
no. 654119), SoBigData (grant no. 654024);<br>
<br>
<br>
Version<br>
--------------------------------------------------<br>
<br>
1.0.2-4.3.0-125842 (2017-03-20)<br>
<br>
Please see the file named "changelog.xml" in this directory for the release notes.<br>
<br>
<br>
Authors<br>
--------------------------------------------------<br>
<br>
* Gerasimos Farantatos (g.farantatos-AT-di.uoa.gr), University of Athens, <br>
Department of Informatics and Telecommunications.<br>
<br>
* Second author Alexandros Antoniadis (a.antoniadis-AT-di.uoa.gr), University of Athens, <br>
Department of Informatics and Telecommunications.<br>
<br>
Maintainers<br>
-----------<br>
<br>
* Gerasimos Farantatos (g.farantatos-AT-di.uoa.gr), University of Athens, <br>
Department of Informatics and Telecommunications.<br>
<br>
* Second author Alexandros Antoniadis (a.antoniadis-AT-di.uoa.gr), University of Athens, <br>
Department of Informatics and Telecommunications.<br>
<br>
<br>
Download information<br>
--------------------------------------------------<br>
<br>
Source code is available from SVN: <br>
http://svn.research-infrastructures.eu/public/d4science/gcube/branches/resource-registry/ResourceRegistry-configuration-default/1.0/ResourceRegistry-configuration-default<br>
<br>
Binaries can be downloaded from the gCube website: <br>
https://www.gcube-system.org/<br>
<br>
<br>
Installation<br>
--------------------------------------------------<br>
<br>
Installation documentation is available on-line in the gCube Wiki:<br>
https://wiki.gcube-system.org/gcube/index.php<br>
<br>
Documentation <br>
-------------<br>
Documentation is available on-line in the gCube Wiki:<br>
https://gcube.wiki.gcube-system.org/gcube/index.php/Resource_Registry<br>
<br>
Support <br>
--------------------------------------------------<br>
<br>
Bugs and support requests can be reported in the gCube issue tracking tool:<br>
https://support.d4science.org/projects/gcube/<br>
<br>
<br>
Licensing<br>
--------------------------------------------------<br>
<br>
This software is licensed under the terms you may find in the file named "LICENSE" in this directory.<br>
</p>
State and Church in Byzantium during the Civil War of 1321-1328: the Emperor Andronikos II Palaiologos and the Patriarchs Gerasimos I and Esaias
No full textThe goal of the present research work is to determine the role of church in political events during the war between Andronikos II and Andronikos III Palaiologoi (1321-1328) in the Byzantine empire. Its urgency is defined by incomplete explanation of this aspect in Russian and foreign historiography. The first part of the article is devoted to the study of relations between the state and the church during the Andronikos II Palaiologos’ earlier rule (1282-1320). The author concludes that under the church troubles patriarchs sought to rely on the ruling emperor but happened to have no support. As far as state-church relations during the civil war are concerned, they are studied in the second part of the research work. The author puts an emphasis on the patriarchs Gerasimos I (1320-1321) and Esaias’ (1323-1334) political position and clears up the degree of their participation in the conflict between the emperors. He finds out that the church role in political events at that time was high enough. The crisis of power led to a change in relations between patriarchs and Andronikos II; in other words, during the civil war period they did not support him and came down on the side of his grandson. At the same time the synod remained loyal to the ruling emperor
A spectral approach to moho depths estimation from gravity measurements in Epirus (NW Greece).
No full textDC-DC Converters for Photovoltaic Powered DC Microgrid
No full textThe modern world demands more and more electric energy. At the same time, almost a billion more people are expected to gain access to electricity over the next decade. All of the above compose a very challenging future, where a continuously increasing amount of electric energy will be needed. However, the planet is not able to provide us anymore with the necessary resources for that, jeopardizing the environmental stability. The aim of this thesis is the design and testing of power electronics converters that will contribute positively to the production and distribution of sustainable energy. In particular, a Maximum Power Point Tracking Converter is designed and tested. The 6.4kW converter is able to connect to two separate PV strings. The output of the converter is connected to a bipolar DC distribution grid. Afterwards, a 3.68kW Voltage Balancing Converter was designed for the stabilization of the voltage between the two phases of a bipolar DC grid. Particular interest is given to the challenges that arouse for the power supply of a DC Micro-Grid from a Photo-Voltaic plant. The project took place in the DC lab of the company DC Opportunities.Electrical Engineering | Sustainable Energy Technolog
Photoelectrode design principles for efficient photo-charging of solar redox flow batteries
No full textIn connection with attempts to increase the Solar Redox Flow Battery (SRFB) viability, an investigation was done into the charge carrier transport mechanisms entailed at the photoelectrode interlayer interfaces. On the basis of a preliminary study, the investigation focused on the development of a suitable conducting layer at the electrolyte/electrode interface as well as the development and control of a hole extraction layer, based on the device electronic structure and energy levels matching. Research was conducted into the properties of various prospective materials that could improve charge carrier transport at the electrolyte/photoelectrode interface. Once the optimal configuration is determined, the photoelectrode and redox couples are prepared and characterized and the photocharging performance of the device is optimized. Furthermore, the control of the formation conditions of a hole extraction layer took place, in order to yield improved internal charge carrier separation and transport. Various hole transport layers were assessed in SRFB system in relation to the photo-charging performance. The described process resulted in the development of a conducting layer through the growth of well distributed islands, which led to a high solar-to-chemical conversion of 9.4%. Through the control of the formation conditions of the hole extraction layer, better spatial separation of the photogenerated charge carriers was achieved, leading to improved device performance. Despite the enhanced viability of each device in terms of efficiency, further research into the long-term stability is essential for its practical implementation. This mainly relates to electrolyte degradation to form solid precipitates and photocorrosion of the absorber semiconductor materials in acidic conditions.Electrical Engineering | Sustainable Energy Technolog
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