1,721,003 research outputs found
Experimental observations of an installed-on-pylon contra-rotating open rotor with equal blade number in pusher and tractor configuration
No full textThe application of advanced beamforming techniques for the noise characterization of installed counter rotating open rotors
No full textThe application of advanced beamforming techniques for the noise characterization of installed counter rotating open rotors
No full textThis paper reports on the results of a series of aeroacoustic measurements of a counter rotating open rotor (CROR) installed on a 1=7th scale model of an advanced regional aircraft design. The tests were conducted in a large low speed wind tunnel for a variety of aircraft geometries, angles of attack and low speeds. Data were acquired on three far field beamforming arrays. The study attempts to characterize the installed CROR noise source through the application of several beamforming techniques applied to each individual array and to a global array of the three arrays in combination. Although some results have been achieved in this preliminary study, there are also drawbacks and limitations of the beam-forming processes for the case of model with CRORs, therefore a deeper investigation will be necessary. This work has been conducted as part of the European Clean Sky funded
WENEMOR project which will be completed in August 2013, the testing phase of which was completed in May 2013
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
Dynamika přestupu tepla při vychlazování vysoce rozehřátých povrchů
No full textQuenching phenomenon is one of the most unexplored phenomena in the field of heat transfer. However, quenching is known for a long time especially due to metal hardening. In the several last decades, the phenomenon has come to the fore of interest in connection with nuclear reactor safety and cryogenic technologies. Quenching is defined as an onset of rapid temperature decrease within cooled geometry by relatively cold liquid. The contact between cooled surface and coolant is not a straightforward process. If the surface temperature is high enough, liquid can't touch the surface directly, but it is separated by stable vapor layer. The layer acts as a thermal insulation barrier and the resulting heat transfer is very limited until surface temperature fails bellow so-called Leidenfrost temperature. The actual value of quenching temperature is inuenced by many factors such as dynamics of the coolant, initial wall temperature, material properties of cooled geometry, etc. An experimental loop with an annular flow channel has been built in order to deepen the knowledge on the quenching phenomenon. The flow channel is vertical and it is equipped with changeable electrically heated tubes (models) with the outer diameter of 9mm and length over 1,7m in three different geometrical configurations: Model A - wall thickness (delta) 0,5mm, Model B - delta = 1,0 mm and Model C with variable wall thickness. Each model was exposed to bottom flooding at initial wall temperature levels from 250 degrees of C to 700 degrees of C and with four different coolant mass fluxes for each temperature level (80, 110, 190, 270 kg.m-2.s-1). Results show the complexity of the phenomenon for given configurations and initial experiment parameters. Correlations for all important points in the process were developer i.e. correlations for quenching, critical and nucleate boiling temperature. Another part of the study is suggestion of heat transfer coeficients for the three-regional rewetting model. On top of that correlations for local heat transfer coeficients were proposed. There is also pointed out the effect of pressure pulsation during the flooding and its influence on the process. All these results together with raw experimental results can serve as an input for further investigations of the phenomena and for nuclear reactor safety analyses.Jevy provázející smáčení vysoce rozehřátých povrchů jsou jedněmi z nejméně prozkoumaných jevů z oblasti přenosu tepla. Tyto procesy jsou jako takové známé již dlouhou dobu především díky tepelnému zpracování kovů (angl. quenching). V posledních několika dekádách se tento jev dostal do popředí zájmu především ve spojení s bezpečností jaderných reaktorů a kryogenní technikou. Smáčení je definované jako počátek prudkého poklesu teploty chlazeného objektu, který je způsobený kontaktem s relativně chladným chladivem, např. vodou. Přímý kontakt mezi rozehřátým povrchem a chladivem však není přímočarý proces. Pokud je teplota povrchu dostatečně vysoká, je kapalina oddělena od povrchu parní vrstvou, která brání přímému kontaktu povrch-chladivo. Tato parní vrstva se chová jako tepelně izolační vrstva a přestup tepla je tak značně snížen až do okamžiku, kdy teplota povrchu poklesne pod tzv. Leidenfrostovu teplotu, při které dojde ke kolapsu parní vrstvy. Vlastní hodnota této teploty je závislá na mnoha faktorech, jako například dynamice chladiva, počáteční teplotě povrchu, vlastnostech chlazeného objektu, geometrii, atd. Za účelem prohloubení znalostí o tomto jevu bylo postaveno experimentální zařízení s anulárním průtočným kanálem. Testovací kanál má výšku přes 1.7m a je vybaven měnitelnými průchodem elektrického proudu vyhřívanými modely (trubkami) s vnějším průměrem 9mm. Tyto modely byly použity ve třech variantách: Model A s tloušťkou stěny 0.5mm, Model B - 1.0mm a Model C s proměnnou tloušťkou stěny po výšce. Každý model byl vystaven sérii experimentů se zaplavováním zdola na počátečních tepelných hladinách povrchu od 250°C do 700°C se čtyřmi různými průtoky chladiva 80,110,190,270 kg.m-2s-1. Výsledky ukazují komplexní charakter daného jevu pro danou konfiguraci a parametry. Byly vytvořeny korelace pro všechny důležité body v procesu smáčení, tj. korelace pro teplotu smočení, teplotu kritického tepelného toku a teplotu bublinkového varu. Další částí studie je návrh součinitelů přestupu tepla pro tří-oblastní model smáčení. Navíc jsou zde předloženy korelace pro lokální součinitele přestupu tepla. Poukázáno je ve studii také na efekt tlakových pulzací během zaplavování a jejich vliv na daný proces. Všechny tyto výsledky společně s naměřenými daty mohou sloužit jako vstup pro další studie zaměřené na tento jev, popřípadě pro bezpečnostní analýzy jaderných reaktorů
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
Analýza využití dlouhodobého hmotného majetku, faktory ovlivňující jeho využití
No full textImport 11/07/201
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