1,720,988 research outputs found
High Throughput Disk Scheduling with Fair Bandwidth Distribution
No full textMainstream applications–such as file copy/transfer, Web, DBMS, or video streaming–typically issue synchronous diskrequests. As shown in this paper, this fact may cause work-conserving schedulers to fail both to enforce guarantees and to provide a high disk throughput. A high throughput can be however recovered by just idling the disk for a short time interval after the completion of each request. In contrast, guarantees may still be violated by existing timestamp-based schedulers, because of the rules they use to tag requests.Budget Fair Queueing (BFQ), the new disk scheduler presented in this paper, is an example of how disk idling, combined with properback-shifting of request timestamps, may allow a timestamp-based disk scheduler to preserve both guarantees and a high throughput.Under BFQ each application is always guaranteed–over any time interval and independently of whether it issues synchronous requests–a bounded lag with respect to its reserved fraction of the total number of bytes transferred by the disk device.We show the single-disk performance of our implementation of BFQ in the Linux kernel through experiments with real and emulated mainstream applications
W-CBS: A Scheduling Algorithm for Supporting QoS in IEEE 802.11e
No full textThis paper presents a new scheduling algorithm, the Wireless Constant Bandwidth Server (W-CBS) for the Access Points of an IEEE 802.11e wireless networks to support traffic streams with Quality of Service guarantees, in particular in the case of multimedia applications which present variable bit rate traffic. The performance of W-CBS is compared to that of the reference scheduler defined in 802.11e standard using the ns2 simulator. The results show that the W-CBS outperforms the reference scheduler with VBR traffic, in terms of resource utilization and maximum admitted flows
Wireless link emulation in OneLab
No full textThis paper presents a work in progress to add emulation
of IEEE 802.11 wireless links to the OneLab platform - a
PlanetLab derivative. As for other emulators, our goal is
to enable researchers to run repeatable experiments under
controlled network conditions, and overcome limitations due
to unavailable or expensive hardware.
Our emulation model aims at reproducing the effects of
wireless media on live traffic, but at the packet level and
with a timing resolution in the order of 100μs or higher,
comparable with the resolution of events visible to appli-
cation processes. To this purpose, we define a simplified,
packet level model of the wireless link, and extend the pop-
ular dummynet emulator to support this model.
In the paper we describe the overall architecture of our
emulation extension, discuss the wireless model used, and
illustrate the user- and system- interfaces to configure and
access the emulated environment
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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