1,720,988 research outputs found
Improving wireless network performance using sensor hints
No full textThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 59-62).Users of wireless devices often switch between being stationary and in motion while transferring data. Protocols that perform well in the static setting (where the channel conditions are relatively stable), however, tend to perform poorly when in motion (where channel conditions change rapidly), and vice versa. To circumvent this problem, we note that commodity smartphones and tablet devices come equipped with a variety of sensors, including accelerometers, multiple positioning sensors, magnetic compasses, and inertial sensors (gyros) that can provide hints about the device's mobility. In this thesis, we posit that these sensors can be profitably used to improve the performance of wireless network protocols running on these mobile devices and introduce an architecture for using external sensor hints for this purpose. We validate this idea with many different wireless protocols. First, we show how access points can perform better rate adaptation by changing strategies when they receive hints about a client's mobility. Second, we show how probing protocols for topology maintenance in mesh networks can increase both their efficiency and accuracy by adaptively probing based on movement. Third, we show how vehicular mesh networks can use directionality hints to improve the connectivity of routes. Finally, we outline several other novel applications of external sensor hints for improving wireless network performance. We evaluate our protocols using trace-driven simulation and real-world experiments. We show that our hint-aware rate adaptation protocol increases throughput by 30% to 50% on average over frame-based and SNR-based protocols. Our hint-aware probing protocol reduces the bandwidth consumed by probing to accurately estimate link delivery probabilities-by a factor of 20 in our experiments. And, our hint-aware route selection in vehicular mesh networks increases route stability by a factor of 4 to 5 compared to a hint-free approach in our simulations.by Lenin Ravindranath Sivalingam.S.M
Improving the performance and reliability of mobile applications
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.Cataloged from PDF version of thesis.Includes bibliographical references (pages 129-133).The mobile application ("app") ecosystem has grown at a tremendous pace with millions of apps and hundreds of thousands of app developers. Mobile apps run across a wide range of network, hardware, location, and usage conditions that are hard for developers to emulate or even anticipate during lab testing. Hence, app failures and performance problems are common in the wild. Scarce resources, shift away from familiar synchronous programming models, and poor development support has made it more difficult for app developers to overcome these problems. This dissertation focuses on systems that make it significantly easy for app developers to diagnose and improve their mobile apps. To reduce user annoyance and survive the brutally competitive mobile app marketplace, developers need systems that (i) identify potential failures before the app is released, (ii) diagnose problems after the app is deployed in the wild, and (iii) provide reliable app performance in the face of varying conditions in the wild. This dissertation presents systems that satisfy these needs. VanarSena makes it easy to diagnose common failures in mobile apps before deployment, AppInsight makes it easy to monitor mobile apps after deployment, and Timecard allows mobile apps to adapt to conditions in the wild and provide consistent performance. For the legion of amateur app developers with fewer resources at hand, these systems significantly reduce the barrier for diagnosing and improving mobile apps. The systems are built on top of a binary instrumentation framework that automatically rewrites app binary at bytecode level. Hence, using them requires minimal effort on part of the app developer. The systems include novel instrumentation techniques to automatically track the runtime behavior of the app. To cope with the scarcity of resources, they include resource-aware mechanisms that incur negligible overhead. To make them immediately deployable, they are designed to require no modification to the OS or runtime. We have built VanarSena, AppInsight, and Timecard for the Windows Phone platform. VanarSena does automated app testing by systematically emulating user interactions and fault conditions from the wild to uncover app failures. VanarSena uncovered 2,969 distinct crashes in more than 1,100 apps in the app store. AppInsight does light-weight monitoring of mobile apps in the wild. It automatically instruments the app binary to track performance and failures. AppInsight uncovered several performance bottlenecks and crashes in the wild and has provided useful feedback to developers. Timecard enables apps to adapt at runtime and provide consistent performance in the face of varying conditions in the wild. Timecard can tightly control the response time around a desired user-perceived delay.by Lenin Ravindranath Sivalingam.Ph. D
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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