1,720,965 research outputs found
Experimental evidence of non-ideal compressible effects in expanding flow of a high molecular complexity vapor
Full text linkSupersonic expansions of a molecularly complex vapor occurring within the non-ideal thermodynamic region in the close proximity of liquid-vapor saturation curve were characterized experimentally for the first time. Results for two planar converging–diverging nozzles in the adapted regime and at different inlet conditions, from highly non-ideal to dilute gas state, are reported. Measurements of upstream total pressure and temperature are performed in the plenum ahead of the nozzle, while static pressure and supersonic Mach number measurements are carried out along the nozzle centerline. The investigated expansions are of interest for both fundamental research on non-ideal compressible flows and industrial applications, especially in the energy field. Siloxane MDM (octamethyltrisiloxane, C8H24O2Si3), a high molecular complexity organic compound, is used. Local pressure ratio P/ PTand Mach number M measurements display a dependence on the inlet total state, a typical non-ideal feature different from dilute gas conditions
Experimental observation and thermodynamic modeling of non-ideal expanding flows of siloxane MDM vapor for ORC applications
Full text linkThis paper reports extensive experimental results characterizing the supersonic expansion of an organic vapor in non-ideal thermodynamic conditions typical of organic Rankine cycle (ORC) turbines. Data are also employed to assess the accuracy of different thermodynamic models used to describe non-ideal expansions. Experiments were carried out on a converging-diverging nozzle test section, where siloxane vapor MDM expanded in the proximity of the saturation curve, the typical operating region of ORC expanders, thus proving the importance of the present investigation for ORC technology. Indeed, detailed experimental data representative of ORC expansions, useful for design tool assessment, were lacking in the open literature up to date. Two nozzles, featuring exit Mach number of 2.0 and 1.5, were tested from highly non-ideal states to dilute gas conditions. The nozzle flow was characterized by measuring total pressure, total temperature and static pressure along the axis. The Mach number was measured at the centerline through schlieren imaging. Vapor expansion was found to be dependent on inlet conditions, thus proving the flow non-ideality. State-of-the-art thermodynamic models proved their capability of fully describing the flow non-ideality, while simpler and easier to implement equations of state, such as van der Waals, can be acceptable for preliminary expander calculations
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
Construction of a Test Facility for Demonstration of a Liquid Lead-bismuth-cooled 10 kW Thermal Receiver in a Solar Furnace Arrangement - SOMMER
Full text linkLiquid metals have been proposed in the past as high temperature heat transfer media in concentrating solar power (CSP) systems. Until the mid 80s test facilities were operated with liquid sodium-cooled central receivers. After a period of reduced interest in that approach, several new efforts have been reported recently, particularly from the US, South Africa and Australia. In addition, several recent publications have highlighted the attractive properties of liquid metals for CSP applications. A newcontribution to this topic has been launched by Karlsruhe Institute of Technology (KIT) and the Solar Institute of the German
Aerospace Center (DLR), combining their experience in CSP and liquid metal technology. The overall goals of this project are planning, design, construction and operation of a small concentrating solar power system in the 10 kW thermal range (named SOMMER) using liquid metal as heat transfer fluid for re-gaining operation experience and validating design methodology and providing a complete design concept for a large pilot CSP plant based on liquid metal technology, up to evaluation of O&M cost and levelized cost of electricity. This paper describes the current status of the work on the design and setup of SOMMER, the research goals of this facility, first results of numerical activities in view of the liquid metal cooled receiver design and the connection to the design activities for the pilot plant
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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