306,307 research outputs found
CICLI DISSIPATIVI E TUBI DI CALORE.
No full textThe behavior of the device known as ′′heat pipe′′ is studied using an irreversible cycle with no overall extgernal work. This cycle has been carefully described in T, S diagram, examining the thermodynamics of capillary phenomena. Starting from this analysis, the following are described: a ′′internal characteristics′′ , due to the thermodynamics and fluid dynamics of the device; an ′′external characteristic′′ defined by the external heat transfer conditions
Gli studi nel Regno Unito della seconda generazione
No full textIl lavoro illustra il contributo di alcuni economisti italiani, segnatamente Pasinetti e Garegnani, allo sviluppo e all'affermazione della scuola sraffiana anglo italiana. Il lavoro mette in evidenza anche le ragioni del progressivo declino, iniziato negli anni '70, di questa scuola di pensiero. Nell'ultima parte vengono illustrati i legami fra alcuni studiosi italiani con il pensiero di Hicks
Thermal analysis of insulated metal substrates for automotive electronic assemblies
No full textTwo types of insulated metal substrates for surface mounting technology (SMT) for automotive applications were thermally examined by means of the TRAIT method [P.E. Bagnoli, C. Casarosa, M. Ciampi, E. Dallago, Thermal resistance analysis by induced transient (TRAIT) method for power electronic devices thermal characterization. Part I: fundamentals and theory, IEEE Transactions on Power Electronics 13 (1998) 1208–1219]. The results showed a noticeably lower static thermal resistance than other solutions commonly used. Moreover, TRAIT analysis provided evidence that the residue thermal resistance has to be ascribed to the epoxy insulating layer of the IMS substrates, suggesting that the differences between different types of IMS substrates are due to differences in the dielectric deposition technology
CONSIDERAZIONI SU CICLI CON IRREVERSIBILITA' MECCANICHE INTERNE [Consideration on the Cycles with Internal Irreversibilities of Mechanical Nature]
No full textStarting from the fundamental relations relying upon the first and second law of thermodynamics, the cycles with no overall external work are examined in this paper. The restricted conditions to which such systems must satisfy under pre-defined assumptions, are determined. Some of these cycles, which exhibit internal irreversibilities of mechanical nature (cicli dissipativi) are studied in detail; as an instance of application for cycles with a recirculating fluid, the case of the single-phase thermosyphon is analyzed
OSSERVAZIONI SU TUBI DI CALORE A MEDIA TEMPERATURA [Observations on Heat Pipes at Medium Temperatures]
No full textAfter a short review of the current status of studies on this subject, the paper describes an analytical optimization method. Experimental apparatus is described and results of tests of a heat pipe operating with water up to the temperature of about 150 C are presented. In particular, the effect of condenser parameters on the heat transfer is investigated
Inner tracking devices at the belle II experiment
No full textIn the future Belle II experiment at the SuperKEKB collider in Tsukuba, Japan, charged particle tracking in the vicinity of the e+e- interaction point is provided by a two-layer silicon pixel detector based on the novel DEPFET technology (PXD) and by a four-layer silicon strip detector (SVD). In this presentation, I review the technology and the design of these two devices, and describe the current state of their construction
DIMENSIONAMENTO DI UN GEOTERMOCONVETTORE: SOLUZIONI, CRITERI E METODI DI CALCOLO
No full textOn the basis of studies carried out during the Progetto Finalizzato Energetica 2, an unconventional system for heat extraction from a geothermal aquifer without fluid withdrawal has been conceived and developed. In the system a special two-phase thermosyphon, called a geothermal convector (GTC), is used. This device operates with a downhole evaporator and a condenser at the ground level. In this paper the problems of this application are described: the fundamental elements for determining the device performance and the thermal design criteria are reported. Moreover, a method for designing the system for activating the geothermal fluid convection inside the well is given. Finally, to exemplify the possible results of this design procedure, a GTC prototype, in an advanced stage of realization, is described
VALUTAZIONI SPERIMENTALI E TEORICHE DI GRADIENTI TERMICI IN UN TRAVELLING GRADIENT RIG
No full textAfter a brief exposition of the scope of the traveling gradient method, a heat pipe employed as a thermostat in a ′′Traveling Gradient Rig′′ is described. Experimental results of temperature distribution along the axis of a thermocouple with maximum gradients of about 27 degree K/mm are reported. Their shape and slope is analyzed theoretically
Il termosifone bifase impiegato quale dissipatore di calore per diodi e tiristori di potenza
No full textThis work deals with a two-phase thermosyphon applied to cooling power electronic components. The difference between a typical heat sink with thermal gradient and one with a two-phase thermosyphon is shown. On the basis of general design criteria, a cooling device of this type for a 1. 0 kw thyristor has been realized. Heat transfer performance of this dissipator has been experimentally determined: the thermal resistance of about 0. 025 degree C/W, obtained by using this radiator with forced convection in air, is very similar to that offered by the devices employing water in forced convectio
Alcune note su filosofia e didattica della matematica in Francesco Cecioni. Le Lezioni sui fondamenti della matematica
No full textIn questo contributo, esponiamo e commentiamo le principali idee sviluppate da Francesco
Cecioni nelle sue Lezioni sui fondamenti della matematica, pubblicate nel 1958. Il testo
comprende buona parte del materiale delle lezioni svolte da Cecioni per il corso di matematiche
complementari all’università di Pisa. Siamo convinti che questo volume non abbia ricevuto
l’attenzione che merita. Vi sono, infatti, esposte interessanti concezioni su numerosi aspetti
fondazionali della matematica. Noi abbiamo selezionato quelli che ci sembravano più rilevanti.
Abbiamo così esposto la concezione generale della matematica per come emerge dallo scritto di
Cecioni, deducendola: 1) dall’analisi di come egli intende la natura dell’aritmetica; 2) dal
modo in cui interpreta l’assioma di scelta. Qui sono notevoli le critiche di Cecioni alla
proposizione zermeliana; 3) dal confronto istituito da Cecioni tra implicazione logica e
causalità; 4) dalla sua concezione del rapporto tra matematica e logica simbolica. Siamo certi
che il lettore troverà spunti stimolanti e originali nelle idee di Cecioni, anche se alcune
potranno non esser condivise
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