1,720,980 research outputs found
Attività propedeutiche per la messa in funzione di un impianto termoidraulico ad alta pressione per pretest su simulacri di componenti
Full text linkIn questo documento è trattata l'analisi termoidraulica pre-test di qualifica di una valvola prototipo tramite l'impianto VAPORE. Il codice termoidraulico d'impianto utilizzato è RELAP5. Il codice, opportunamente validato con dati sperimentali, è stato utilizzato per la simulazione delle prove di qualifica della valvola prototipale in oggetto. Sono stati progettati ed eseguiti tre differenti tipologie di tests, diffusamente descritti nel documento. Si ha ragione di credere che i risultati siano significativi, dato che l'input è stato validato sulla base di risultati sperimentali. L'impianto VAPORE si è dimostrato essere in grado di eseguire, con ampio margine in eccesso sulle portate, le prove preventivate
USING MIXED BED ION EXCHANGE IN THE M.A.R.S. NUCLEAR POWER PLANT
No full textRadwaste Solutions a Publication of the American Nuclear Societ
Water two-phase flow through pressure safety valve with variable backpressure: check of calculation methods to estimate mass flow-rate and critical flow conditions
No full textA careful design of pressure safety valves (PSV) is an essential requirement for safeguarding of industrial plants; reliable correlations are available for PSV design in the cases of liquid or gas discharge. Instead, if two-phase flow is possible, especially for low vapour quality (less than 10%), PSV design becomes very difficult owing to complex thermal hydraulic phenomena that happen between the two phases; moreover, in this situation, the prediction of the critical flow onset (which occurs when the fluid velocity becomes equal to the sound velocity in the fluid) is very important for a correct design because it involves a choked flow situation.
Currently there are some calculation methods, based on different simplifying hypotheses, that try to predict the two-phase flow-rate through a PSV knowing the inlet fluid conditions (pressure, quality or temperature) and the outlet pressure; however, none of them is acknowledged as being reliable for every situation and, therefore, there are not standards for PSV design under two-phase conditions.
This paper shows the results of an experimental research carried out through a PSV with steam-water two-phase flow. The experimental data are compared with the results of a calculation method based on the homogeneous model with non equilibrium hypotheses. The performance of the model is evaluated as a function of inlet and outlet parameters; an analysis of model critical flow prediction capability is presented too, with some uncertainties caused by the test procedures (here the mass flow-rate is imposed
On the reciprocal influence of gas injection method and liquid contamination on bubble rising velocity in a liquid column
No full textEfflusso bifase attraverso valvole di sicurezza. Confronto tra i dati sperimentali e le previsioni di alcuni modelli omogenei
No full textLa sicurezza è un’esigenza particolarmente sentita negli impianti in cui situazioni accidentali possono comportare un aumento incontrollato della pressione con conseguenti pericoli per l’incolumità del personale, le popolazioni e l’ambiente. Le valvole di sicurezza sono tra i componenti più utilizzati per limitare entro valori accettabili l’incremento di pressione.
Il loro dimensionamento segue delle norme ben precise ed affidabili per gli efflussi monofase mentre manca una standardizzazione nel caso di efflussi bifase. Nel corso degli ultimi cinquanta anni per la rappresentazione dell’efflusso bifase sono stati sviluppati diversi modelli caratterizzati da diverse ipotesi semplificative; al momento, però, nessun metodo di calcolo è riconosciuto a livello di standard per il dimensionamento delle valvole di sicurezza.
In questo articolo sono presentati alcuni risultati di una ricerca sperimentale in corso sull’impianto VASIB, situato presso l’Istituto di Termofluidodinamica Energetica nel centro ricerche dell’ENEA Casaccia. Le esperienze sono condotte, utilizzando acqua come fluido evolvente, su una valvola di sicurezza reale, for=10mm, per differenti condizioni di ingresso: portata (300÷1500 kg/h), titolo (0÷10%), pressione (0.5÷1.75 MPa). I dati sperimentali sono stati comparati, in funzione dei diversi parametri di ingresso, con le previsioni di un metodo di dimensionamento ultimamente suggerito dall’API (American Petroleum Institute) e un metodo semplificato sviluppato per confronto; entrambe le metodologie utilizzano le ipotesi del modello omogeneo di equilibrio (metodo w
Safety Characteristics of MARS Nuclear Plant
No full textNew design criteria in the field of small and medium sized nuclear reactors will be illustrated; particular consideration will be given to the reactor MARS (Multipurpose Advanced Reactor, Inherently Safe) now under development at the Department of Energetics, University of Rome.
An analysis of plant behaviour during a Station Black-out accident has been performed using the computer program RELAP 5/Mod. 2
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
- …
