1,721,295 research outputs found
Resource Management for Advanced Transmission Antenna Satellites
No full textIn satellite communications, narrow spotbeams can provide high power and data rates to the desired location while reducing spatial interference. Advanced transmission antenna technology is critical to generate and switch narrow beams rapidly among a large number of users under quality of service (QoS) constraints such as average delay. In this paper, we jointly optimize resource allocation and congestion control, and compare the performances of two types of satellite transmit antennas: a multiple beam antenna and a phased array antenna. For a multiple beam antenna with traveling wave tube amplifiers (TWTA), throughput is decided by either the most demanding user or the average of all user parameters. For a phased array antenna, joint antenna gain patterning and beam scheduling is given as a function of channel conditions, interference (depending on users' geographical distribution), and average delay requirements. We then develop a low-complexity on-line algorithm of choosing either interference suppression or sequential service for the active users who are closely located within the width of a spotbeam. Due to flexible power allocation, the phased array antenna can provide better performance than the multiple beam antenna when a small number of users are very demanding or many users are densely crowded in a small area.
Resource management for advanced transmission antenna satellites
No full textIn satellite communications, narrow spotbeams can provide high power and data rates to the desired location while reducing spatial interference. Advanced transmission antenna technology is critical to generate and switch narrow beams rapidly among a large number of users under quality of service (QoS) constraints such as average delay. In this paper, we jointly optimize resource allocation and congestion control, and compare the performances of two types of satellite transmit antennas: a multiple beam antenna and a phased array antenna. For a multiple beam antenna with traveling wave tube amplifiers (TWTA), throughput is decided by either the most demanding user or the average of all user parameters. For a phased array antenna, joint antenna gain patterning and beam scheduling is given as a function of channel conditions, interference (depending on users' geographical distribution), and average delay requirements. We then develop a low-complexity on-line algorithm of choosing either interference suppression or sequential service for the active users who are closely located within the width of a spotbeam. Due to flexible power allocation, the phased array antenna can provide better performance than the multiple beam antenna when a small number of users are very demanding or many users are densely crowded in a small area.Defense Advanced Research Projects Agency (NGI Grant
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
Bariatric surgery or medicine for type 2 diabetes?\ud
No full textDiet and medical treatment are the standard treatment for type 2 diabetes. In obese subjects with type 2 diabetes, bariatric surgery is effective in resolving diabetes. Two clinical trials comparing bariatric surgery to medical treatment were evaluated. Both the Surgical Treatment And Medications Potentially Eradicate Diabetes Efficiently (STAMPEDE) trial (laparoscopic Roux-En Y gastric bypass and sleeve gastrectomy) and the DIet and medical therapy versus BAriatric SurgerY in type 2 diabetes (DIBASY) trial (laparoscopic gastric bypass and biliopancreatic-diversion) showed that surgery was more effective than medical care in resolving or managing type 2 diabetes. Larger studies, or a compilation of studies, are needed to determine whether one of these procedures is better, or if they are all similarly effective, and this should also be weighed against the risk of the operations.\ud
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Cost-efficient fiber connection topology design for metropolitan area WDM networks
No full textIn this paper, we provide some analytical insights into physical architectures that can serve as benchmarks for designing a cost-efficient WDM metropolitan area network (MAN). For uniform all-to-all traffic and regular topologies with nodal symmetry, we identify a class of regular graphs--Generalized Moore Graphs--that have several attractive properties by formulating a first-order cost model and characterizing the tradeoff between fiber and switching resources. Our results show that, in conjunction with minimum hop routing, Moore Graphs achieve the minimum cost and simultaneously use the least number of wavelengths. We also take steps to broaden the scope of our work by addressing irregular network topologies, which represent most existing networks. Our results show that Generalized Moore Graphs can be used to provide useful estimates of the cost of irregular networks and can serve as good reference architectures for the designs of practical networks.National Science Foundation (U.S.). Future Optical Network Architecture (Grant CNS-0626800
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