1,720,986 research outputs found
Why is network reselection an issue for cross-border vehicular applications?
No full textSafety-critical advanced driver-assistance systems (ADAS) are expected to benefit from cellular vehicle-to-everything communication, providing both short-range and long-range wireless connectivity between vehicles and road/network infrastructure equipment. However, upon switching between adjacent coverage areas belonging to different network operators, the wireless connectivity may be discontinued. This issue prevents network service continuity and causes interruption of ADAS service availability. In this paper, we aim at assessing the average duration of service interruption due to such network reselection procedures. We provide performance evaluation results highlighting that there is a wide gap between the best case scenario and the worst case scenario. Moreover, we propose a simple heuristic to limit the downside of the lack of cooperation between network operators; our heuristic algorithm, which does not require a tight integration between the operators, performs much better than the worst case and it is fairly comparable with the best case scenario. Nevertheless the present work highlights the importance of a tighter integration between network operators to reduce the delay to the minimum
Advances in effusive cooling techniques of gas turbines
No full textGas turbine combustion chambers and turbine blades require better cooling techniques to cope with the increase in operating temperatures with each new engine model. Current gas turbine inlet temperatures are approaching 2000 K. Transpiration-cooled components have proved an effective way to achieve high temperatures and erosion resistance for gas turbines operating in aggressive environments, though there is a shortage of durable and proven technical solutions. Effusion cooling, on the other hand, is a relatively simple and more reliable technique offering a continuous coverage of cooling air over the component's hot surfaces. This paper presents a numerical model suitable to design the geometric features of effusive cooling systems of gas turbine hot components, and to evaluate their thermo-fluid-dynamic characteristics. The model has been developed specifically with the aim to show the potential advantages deriving from the adoption of the new Poroform (R) technology. According to this technology the design of the distributions of the diameter and density of holes on the cooled surface allows complete freedom for the thermo-mechanical optimization of the cooled component, with a view to reducing the metal's working temperature and achieving isothermal conditions for large blade areas' In this paper the diameter, density and spacing of the holes, the adiabatic film efficiency and the coolant air consumption of a first stage gas turbine effusion cooled blade are extensively discussed to highlight the system cooling capacity. The results of two cooling solutions for a first-stage gas turbine blade are presented, i.e. the thermo-fluid-dynamic optimized design and one possible manufacturing-oriented optimized design of the cooled component. (c) 2006 Published by Elsevier Ltd
Advances in effusive cooling techniques of gas turbines
No full textGas turbine combustion chambers and turbine blades require better cooling techniques to cope with the increase in operating temperatures with each new engine model. Current gas turbine inlet temperatures are approaching 2000 K. Transpiration-cooled components have proved an effective way to achieve high temperatures and erosion resistance for gas turbines operating in aggressive environments, though there is a shortage of durable and proven technical solutions. Effusion cooling, on the other hand, is a relatively simple and more reliable technique offering a continuous coverage of cooling air over the component’s hot surfaces. This paper presents a numerical model suitable to design the geometric features of effusive cooling systems of gas turbine hot components, and to evaluate their thermo-fluid-dynamic characteristics. The model has been developed specifically with the aim to show the potential advantages deriving
from the adoption of the new Poroform technology. According to this technology the design of the distributions of the diameter and density of holes on the cooled surface allows complete freedom for the thermo-mechanical optimization of the cooled component, with a view to reducing the metal’s working temperature and achieving isothermal conditions for large blade areas.
In this paper the diameter, density and spacing of the holes, the adiabatic film efficiency and the coolant air consumption of a first stage gas turbine effusion cooled blade are extensively discussed to highlight the system cooling capacity.
The results of two cooling solutions for a first-stage gas turbine blade are presented, i.e. the thermo-fluid-dynamic optimized design and one possible manufacturing-oriented optimized design of the cooled component
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
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