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Προσομοίωση Συστημάτων Επεξεργασίας Δοσοληψιών και Μελέτη Μεθόδων για την Ικανοποίηση Στόχων Επίδοσης
No full textThe transaction concept, based on the concept of contract law, signifies the properties of atomicity, consistency, isolation, and durability for a sequence of actions. These properties, widely known with the acronym ACID, are essential for supporting concurrent access to shared data and for failure handling, especially in distributed environments. The object of this work is the development of an integrated environment for simulation of trancaction processing systems, with the aim to study the operation and performance of such systems. The environment incorporates the TPsim simulator and a mechanism that supports experiment management, so as to automate the process of specifying simulation experiments, conducting the experimental steps, and collecting measurements. The simulator models with considerable detail the operation of a typical trancaction processing system, and enables the estimation of a variety of variables related to resource consumption and system performance. The simulation environment was used for the experimental evaluation of a series of scheduling algorithms for complex units of work, that consist of multiple transactions. Workload units of this type occur often in practice, and represent a special class of workflows. The study of this workload class has started to draw considerable research interest, and this work presents a first performance study. The proposed scheduling algorithms are oriented towards satisfying performance goals, which are specified as requirements about the average response time per workload class. # Η έννοια της δοσοληψίας (transaction), βασισμένη στην νομική έννοια της σύμβασης, υποδηλώνει τις ιδιότητες της ατομικότητας, συνέπειας, απομόνωσης, και μονιμότητας για μια σειρά πράξεων. Οι ιδιότητες αυτές, που αναφέρονται στη βιβλιογραφία με την ακροστοιχίδα ACID (atomicity, consistency, isolation, durability), είναι απαραίτητες για την υποστήριξη ταυτόχρονης προσπέλασης σε κοινόχρηστα δεδομένα και την αντιμετώπιση βλαβών, ειδικά σε κατανεμημένα περιβάλλοντα. Στα πλαίσια της εργασίας αυτής αναπτύχθηκε ένα ολοκληρωμένο περιβάλλον για την προσομοίωση συστημάτων επεξεργασίας δοσοληψιών, με σκοπό την μελέτη της δυναμικής συμπεριφοράς και επίδοσης τέτοιων συστημάτων. Το περιβάλλον περιλαμβάνει τον προσομοιωτή TPsim και ένα μηχανισμό που υποστηρίζει την διαχείριση πειραμάτων προσομοίωσης, ώστε να αυτοματοποιηθεί κατά το δυνατόν η διαδικασία της περιγραφής πειραμάτων, του συντονισμού της εκτέλεσης των πειραματικών βημάτων, και της συλλογής μετρήσεων. Ο προσομοιωτής μοντελοποιεί με σημαντική λεπτομέρεια όλα τα υποσυστήματα ενός τυπικού συστήματος επεξεργασίας δοσοληψιών, και επιτρέπει την εκτίμηση ποικιλίας μεταβλητών σχετικών με την κατανάλωση πόρων και την επίδοση του συστήματος. Το περιβάλλον προσομοίωσης χρησιμοποιήθηκε για την πειραματική αξιολόγηση μιας σειράς αλγορίθμων χρονοπρογραμματισμού για σύνθετες μονάδες φόρτου εξυπηρέτησης, που εκτελούνται ως σειρά από δοσοληψίες. Αυτού του είδους οι μονάδες φόρτου εμφανίζονται συχνά στην πράξη, και αποτελούν μια περίπτωση της κατηγορίας μονάδων φόρτου που αναφέρεται με τον όρο {\sf workflows}. Η μελέτη αυτής της κατηγορίας έχει αρχίσει να συγκεντρώνει σημαντικό ερευνητικό ενδιαφέρον και στην εργασία αυτή γίνεται μια πρώτη μελέτη επίδοσης. Οι προτεινόμενοι αλγόριθμοι χρονοπρογραμματισμού είναι προσανατολισμένοι στην ικανοποίηση στόχων επίδοσης, που διατυπώνονται ως απαιτήσεις για τον μέσο χρόνο απόκρισης ανά κλάση μονάδων φόρτου
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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