1,721,006 research outputs found
Multistage Shared-per-Wavelength Optical Packet Switch: Heuristic Scheduling Algorithm and Performance
No full textAn optical switch architecture is presented based on the shared-per-wavelength strategy for contention resolution in the wavelength domain, which impacts on wavelength converters requirements and switch organization.
The general sharing concept is first introduced and the related practical solution as a multi-stage switch architecture is presented and thoroughly analyzed both in performance and control perspectives.
Heuristic scheduling to manage packet forwarding in synchronous context is developed and discussed in terms of computational complexity. A simple accurate analytical model is developed and validated against simulation to numerically evaluate packet loss performance of the shared-per-wavelength switch.
The main achievement of the work is represented by the proposal of a feasible approach which leads to remarkable cost saving in terms of optical gates and wavelength converters under the conditions outlined
Evaluation of packet scheduling in hybrid optical/electrical switch
No full textThis paper presents a hybrid optical/electrical
switch for high-capacity future network development. A
switch architecture to provide packet switching by solving
contention in wavelength and time domains is considered,
relying on available optical and electrical technology. Physical
and logical aspects regarding switch feasibility and management,
in relation to the hybrid nature of the switch, are
addressed. Scheduling algorithms to support multi-service
packet forwarding are compared with optimally exploit
optical and electrical subsystems according to traffic characteristics
and needs. The main outcomes of the paper suggest
criteria to design high-capacity packet switches, based
on present-day technology constraints and quality of service
requirements, to achieve a fair balance between optical transparency
and loss performance
Sharing Wavelength Converters in Multistage Optical Packet Switches
No full textThis paper describes a multistage switch based on the broadcast-and-select principle. It implements shared per node wavelength conversion for contention resolution in optical packet-switched networks. A novel scheduling algorithm is proposed to control packet forwarding in synchronous context. An analytical model is provided to calculate the packet loss probability related to the multistage configuration. Results show how the sharing of wavelength converters impacts on node performance, and provide a meaningful support for cost-performance benchmarking studies
Performance of Scheduling Algorithms in Multi-Stage Optical Packet Switches with Sparse Wavelength Converters
No full textThis paper describes the scheduling algorithms to control the optical packet forwarding in a multi-stage switch based on the broadcast-and-select principle. The aim of control algorithms is to fully exploit switch resources while avoiding contention in the wavelength and space domains.
A multi-stage switch based on the shared per node wavelength conversion scheme is considered in a synchronous context. An analytical model is provided to calculate the packet loss probability in relation to different reference traffic scenarios. Results show how the sharing of wavelength converters impacts on node performance depending on the scheduling algorithm applied, and provide a meaningful support for optical packet switch design
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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