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Ελαφριά εικονικοποίηση και παρυφές δικτύου
No full textThe evolution of the fifth generation of networks (5G Networks) brought upon a set of new technology solutions that aim to address the increased demands of users (i.e., high data rates, ultra-low latency and reliability) as well as support diverse requirements of next-generation applications. Communication systems are going through radical transformations, incorporating emerging technologies, such as Network Function Virtualization (NFV), Software-Defined Networks (SDNs), and Cloud orchestration systems.At the same time, micro-data centers are being deployed to the corresponding unified environments, bringing virtualized services closer to the users (i.e., improving service performance and reliability, as well as reducing the communication latency). This new research area is defined as edge computing. However, legacy cloud deployments usually employ traditional virtual machines (VMs), which are resource-costly, face slow time for deployment or scaling up of virtual resources. Given the limited-resource availability as well as the dynamic characteristics of user demands or application requirements in edge clouds, the traditional virtual machines are not suitable in these environments. In this respect, the adoption of alternative lightweight virtualization approaches for edge cloud seek to fulfill such demands, given their particular features e.g. rapid manipulation of virtual resources. Thus, it is essential to seek new flexible orchestration and management solutions that utilize more efficiently the available resources i.e., compared to traditional cloud deployments. In other words, there is a need for systemic adaptations of 5G and Beyond ecosystems towards these goals.The main challenge of the dissertation is to propose novel flexible, adaptable and efficient edge-cloud orchestration solutions utilizing lightweight virtualization technologies, such as containers and Lightweight Virtual Machines (LVM). The latter technologies bring significant adaptability advantages to dynamic changes in network conditions and service requirements, along with fast responsiveness, being crucial for edge cloud deployments in 5G networks. This dissertation addresses crucial issues associated with 5G networks (i.e., elasticity, scalability, heterogeneity and resource efficiency), identifies the associated trade-offs of utilizing lightweight virtualization technologies, implements and investigates lightweight cloud orchestration platforms with orchestration mechanisms (e.g., efficient resource allocation and service elasticity), as well as proposes a new cloud orchestration strategy (i.e., Virtualization Technology Shifting) that takes into account the performance and resource demands of alternative virtualization technologies to address challenging application and resource requirements.Η εξέλιξη των Δικτύων πέμπτης γενιάς (5G Νetworks) επέφερε ένα σύνολο νέων τεχνολογικών λύσεων, οι οποίες έρχονται α) να καλύψουν αυξημένες απαιτήσεις/ανάγκες των χρηστών (υψηλούς ρυθμούς μετάδοσης δεδομένων, μείωση της καθυστέρησης επικοινωνίας και αξιοπιστία), β) να υποστηρίξουν τις ποικιλόμορφες απαιτήσεις των αναδυόμενων επόμενης γενιάς εφαρμογών. Τα συστήματα επικοινωνίας μετασχηματίζονται ριζικά ενσωματώνοντας αναδυόμενες ετερογενείς τεχνολογίες, όπως η Εικονικοποίηση Δικτυακών Λειτουργιών (NFV), τα Προγραμματιζόμενα Δίκτυα (SDN) και τα συστήματα ενορχήστρωσης του Υπολογιστικού Νέφους (ΥΝ).Ταυτόχρονα, στα αντίστοιχα ενοποιημένα περιβάλλοντα αναπτύσσονται τα μικρά νέφη, τα οποία βρίσκονται κοντά στους χρήστες και προσφέρουν εικονικοποιημένες υπηρεσίες υπολογιστικού νέφους, (π.χ. βελτιώνουν την απόδοση, την αξιοπιστία της υπηρεσίας, μειώνουν την καθυστέρηση της επικοινωνίας). Αυτή η νέα ερευνητική περιοχή ορίζεται ως νεφοϋπολογιστική στις παρυφές του δικτύου (Edge Computing). Ωστόσο, τα παραδοσιακά περιβάλλοντα νεφοϋπολογιστικής χρησιμοποιούν συνήθως παραδοσιακά λειτουργικά συστήματα πλήρους κλίμακας (VMs), τα οποία είναι δαπανηρά σε πόρους, αντιμετωπίζουν πολύ αργό χρόνο εκκίνηση ή κλιμάκωσης των εικονικών πόρων. Δεδομένης της περιορισμένης διαθεσιμότητας των πόρων, καθώς και των ποικίλων δυναμικών χαρακτηριστικών των απαιτήσεων των χρηστών ή των απαιτήσεων των εφαρμογών στις παρυφές της νεφοϋπολογιστικής, οι παραδοσιακές εικονικές μηχανές δεν είναι κατάλληλες σε αυτά τα περιβάλλοντα. Από την άποψη αυτή, η υιοθέτηση εναλλακτικών προσεγγίσεων ελαφριάς εικονικοποίησης στις παρυφές του δικτύου επιδιώκει να ικανοποιήσει αυτές τις απαιτήσεις αξιοποιώντας τα ιδιαίτερα χαρακτηριστικά τους, όπως η ταχεία διαχείριση των εικονικών πόρων. Συνεπώς, είναι απαραίτητο να αναζητηθούν νέες ευέλικτες λύσεις ενορχήστρωσης και διαχείρισης που να αξιοποιούν αποτελεσματικότερα τους διαθέσιμους πόρους, σε σύγκριση με τα παραδοσιακά περιβάλλοντα νεφοϋπολογιστικής. Με άλλα λόγια, υπάρχει ανάγκη για συστημικές προσαρμογές των οικοσυστημάτων πέμπτης και των επόμενων γενιών δικτύων (5G and Beyond) προς την κατεύθυνση αυτών των στόχων. Η κύρια πρόκληση της διατριβής είναι να προταθούν νέες ευέλικτες και προσαρμόσιμες αποδοτικές λύσεις ενορχήστρωσης του νέφους στις παρυφές του δικτύου χρησιμοποιώντας τεχνολογίες ελαφριάς εικονικοποίησης, όπως οι τεχνολογίες υποδοχέων (Containers) και ελαφριών εικονικών μηχανών (LVM). Οι τελευταίες τεχνολογίες επιφέρουν σημαντικά πλεονεκτήματα προσαρμοστικότητας στις δυναμικές αλλαγές των συνθηκών του δικτύου και των απαιτήσεων των υπηρεσιών, προσφέροντας γρήγορη απόκριση, που είναι ζωτικής σημασίας για την λειτουργία των νεφών στις παρυφές της νεφοϋπολογιστικής στα δίκτυα πέμπτης γενιάς. Η παρούσα διατριβή εστιάζει σε κρίσιμα ζητήματα που σχετίζονται με τα δίκτυα πέμπτης γενιάς (δηλ., ελαστικότητα, επεκτασιμότητα, ετερογένεια και αποδοτικότερη χρήση των πόρων) και προσδιορίζει σχετικά εναλλακτικά οφέλη της χρήσης διαφορετικών ελαφριών μηχανών εικονικοποίησης. Γι΄αυτό το σκοπό υλοποιεί και διερευνά πλατφόρμες ενορχήστρωσης των νεφών στις παρυφές του δικτύου με μηχανισμούς ενορχήστρωσης (π.χ. αποτελεσματική κατανομή των πόρων και ελαστικότητα των υπηρεσιών), και προτείνει μια νέα στρατηγική ενορχήστρωσης νέφους (εναλλαγή των τεχνολογιών εικονοποίησης) λαμβάνοντας υπόψη το αντίκτυπο της απόδοσης και κατανάλωσης των πόρων των εναλλακτικών τεχνολογιών εικονικοποίησης για την αντιμετώπιση των απαιτήσεων των εφαρμογών και πόρων
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
A Comparative Evaluation of Edge Cloud Virtualization Technologies
No full textEdge cloud computing is a crucial enabler for applications or network services with stringent communication requirements in the 5G networks and beyond era. Although edge compute resources contribute to a significant portion of end-to-end performance (e.g., delay), the involved performance trade-offs in relation to the utilized virtualization technologies and application functions are not yet thoroughly investigated. In this context, we study the performance dynamics of alternative edge cloud technologies, including different unikernel flavors, container builds, and implementations of exemplary Web services. Our experiments do not target identifying a single best option, rather than the involved performance trade-offs with respect to both service and infrastructure viewpoints as well as realistic edge cloud tasks, including on service operation, cloud resource or service elasticity, dynamic resource allocation and removal. We provide insights gained from a relevant extensive comparative evaluation based on a novel edge cloud experimentation infrastructure. Our experimental results inspired a conceptual edge cloud orchestration platform and its basic design guidelines, i.e., mixing and matching heterogeneous edge cloud virtual entities with particular operational or performance requirements.1921351136
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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