1,721,052 research outputs found
Reduction of the tonal noise annoyance of axial flow fans by means of optimal blade spacing
No full textA method for the reduction of tonal noise annoyance from axial flow rotors is presented which is
based on the uneven circumferential blade spacing. After a short description of the basic theory of
the tonal noise generation from turbomachinery bladings, the existing methods for the circumferential
spacing choice are analyzed and their practical drawbacks pointed out. A new systematic
approach is presented in which a large number of balanced geometries are generated and then evaluated
by means of an arbitrary objective function. To test the method, several objective functions
have been calculated and the effect of the main parameters has been analyzed. Finally an optimized
rotor representative of automotive applications has been realized and tested in the Johnson Electric-
GATE semianechoic room in presence of a strong upstream velocity perturbation. The resulting
acoustic pressure power spectra have been compared with those of an evenly spaced rotor equipped
with the same blades, thus allowing for estimating the interference function of the unevenly spaced
rotor. The good agreement with the theoretically expected trend proves that even in presence of
strong velocity perturbation the obtained acoustic pressure power spectrum changes according to
the theory which may thus be employed
Experimental study of the tonal noise generated by axial fans in presence of stator-rotor interaction
No full textNel presente lavoro viene studiato il rumore tonale dovuto all’interazione aerodinamica fra la girante di un ventilatore assiale e le scie generate da organi statorici di monte che, per semplicità, vengono simulati mediante una barra posta a monte della girante stessa. Viene descritta una serie di prove effettuate in camera semianecoica su quattro diverse giranti appositamente realizzate, al duplice scopo di effettuare uno studio dell’effetto delle modifiche della geometria (spaziatura asimmetrica delle pale e legge di impilamento dei profili) sul rumore generato e di fornire dati utili alla validazione di codici di previsione attualmente in fase di sviluppo presso l’Università di Genova.
I risultati delle misure effettuate mostrano che, rispetto alla girante con pala equispaziata impilata radialmente, la spaziatura asimmetrica non comporta variazioni significative della portata e neanche del livello globale di pressione sonora; quindi, per lo specifico caso considerato, il miglioramento è attribuibile soltanto ad aspetti soggettivi legati alla percezione dei suoni da parte dell’orecchio umano. Invece, nel caso di pale curve, si ha una forte riduzione del rumore emesso a cui però si accompagna anche una riduzione marcata delle prestazioni; si tratta quindi di un intervento acusticamente efficace ma che richiede un ridisegno fluidodinamico della girante
Quale governance per il sistema universitario post-Covid?
No full textQuesto capitolo intende affrontare proprio il tema della governance del sistema universitario
italiano, attraverso un percorso espositivo che presenterà dapprima, in modo schematico,
le caratteristiche della governance prima del Covid-19 per poi focalizzare l’attenzione sugli interventi operati durante la crisi stessa e successivamente, in relazione agli interventi previsti
dal PNRR, per comprenderne le relazioni con le caratteristiche della governance e le relative
implicazioni. Infine il percorso si chiuderà con alcune proposte per la governance del futuro,
sulla base delle lezioni che emergono non solo dal passato ma anche dal periodo Covid e dal
primo periodo di gestione del PNRR
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
Validation of a 2-D Automotive Fan Design Procedure by means of CFD
No full textThe present paper is part of a more comprehensive study concerning the reliability of a 2D design code for automotive axial fans which has been developed at GATE and is based on the simplified radial equilibrium equation. A typical ringed fan rotor, designed by means of the 2D code, has been numerically studied in twelve different configurations of increasing complexity. This allowed to consider most of the geometrical and fluid dynamic differences between the 2D design and the complex 3D environment of a fan test rig. All the configurations have been studied by means of a commercial CFD package. A careful comparison of the resulting performance yielded useful guide lines for a faster and more reliable preliminary design
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
Possible multiple myeloma dedifferentiation following thalidomide therapy: a report of four cases
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