1,720,954 research outputs found
The Non-Saturated Multiserver Job Queuing Model with Two Job Classes: A Matrix Geometric Analysis
No full textDatacenters comprise large quantities of processors, memory, and input/output modules. These resources are shared among requests (jobs) submitted by datacenter users. Jobs differ in their frequency of arrivals, demand for resources, and execution times. Resource sharing generates contention, especially in heavily loaded systems, that must therefore implement effective scheduling policies for incoming jobs. The First-In First-Out (FIFO) policy is often used for batch jobs, but may produce under-utilization of resources, in terms of wasted servers. This is due to the fact that a job that requires many resources can block jobs arriving later that could be served because they require fewer resources. The mathematical construct often used to study this problem is the Multiserver Job Queuing Model (MJQM), where servers represent resources which are requested and used by jobs in different quantities. Unfortunately, very few explicit results are known for the MJQM, especially at realistic system loads (i.e., before saturation). In this paper, we propose the first exact analytical model of the non-saturated MJQM in case of two classes of customers with exponentially distributed service times and an arbitrary number of identical servers. Our analysis is based on the matrix geometric method. Our results provide insight into datacenter dynamics, thus supporting the design of more complex schedulers, capable of improving performance and energy consumption within large datacenters
Stability Condition for the Multi-server Job Queuing Model: Sensitivity Analysis
No full textA Multiserver Job Queuing Model (MJQM) is a queuing system that can be instrumental in the study of the dynamics of resource allocation in datacenters. The queue comprises a waiting line with infinite capacity and a large number of servers. In this paper, we look at the case of an infinite number of servers. Jobs are termed “multiserver” because each one is characterized by a resource demand in terms of number of simultaneously used servers and by a service duration. In a MJQM, jobs are clustered into classes, and a number of used servers is deterministically associated with each class. Instead, holding times are independent and identically distributed random variables whose distributions depend on the class of the job. We consider the case of just two job classes: “small” jobs use just one server, while “big” jobs use all servers in the system. The service discipline is First-Come-First-Served (FCFS). This means that if the job at the head-of-line (HOL) cannot enter service because the number of free servers is not sufficient to meet the job requirement, it blocks all subsequent jobs, even if there are sufficient free servers for them. Despite its importance, only few results exist for the MJQM, whose analysis is challenging, especially because the MJQM is not work-conserving. This implies that even the stability region of the MJQM is known only in special cases. In a previous work, we obtained a closed-form stability condition for MJQM with big and small jobs under the assumption of exponentially distributed service times for small jobs. In this paper, we compute the stability condition of MJQM with big and small jobs, with an infinite number of servers, considering different distributions of the service times of small jobs. Simulations are used to support the analytical results and to investigate the impact of service time distributions on the expected job waiting time before saturation
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
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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