1,721,628 research outputs found
Analysis of Balje diagrams for a Wankel expander prototype
No full textMicro-generation thermal power plants are often equipped with volumetric expanders due to the possibility of efficiently use small volumetric flow rates. The choice between the use of one or another type of machine (Scroll, Screw, turbodynamic etc.) is usually performed on the basis of non-dimensional diagrams, such as the Balje diagram. Several types of small-size expanders have already been located on the Balje diagram, while others not, because they still are in their prototypical phase, and one of these is the Wankel expander. To the authors’ knowledge, this paper is the first to analyze the position of this type of expander on the Balje diagram, as a function of the geometrical parameters of the operating chamber (primitive radius, eccentricity and axial depth) and the working fluid. The study was carried out by using a numerical model which has been previously validated by the comparison with experimental data. The results indicated that the Wankel expander can be located on a part of the Balje diagram which was not already covered by other known types of volumetric machine and exhibits a comparable efficiency. This remains true for a great extent of working conditions, sizes and working fluids. The influence of the geometrical aspect ratios of the chamber as well as of the working fluid was also analyzed
CFD optimization of CPC solar collectors
No full textThe use of solar energy for industrial purpose at medium-low temperature is receiving attention. As a matter of fact, this temperature range, usually between 80-200°C, requires low cost devices to convert solar energy into useful heat. In particular, the use of CPCs collectors has been suggested in literature because they can be operated without the use of a tracking system, at least within certain limits. The thermal losses of these devices are often reduced by using an evacuated pipe, but this solution increases the manufacturing costs and reduces the reliability and the optical efficiency of the receiver. A series of alternative methods for the thermal losses reduction has been proposed in this paper, for working temperature up to 200°C. Their effectiveness was evaluated by means of a previously validated CFD model. A cylindrical receiver and a concentration ratio of 2 were taken into account. The results were analyzed in terms of temperature contours and thermal efficiency. In particular, the optical efficiency was focused as a key parameter in the performances of a CPC. As conclusion, it was found that a proper arrangement of the absorber with a baffle may entail an improvement of the thermal efficiency without significantly increasing the complexity of the system
Analysis of Acoustic Requirements of a Small Hall of a Theatre According to the Coupling Factor with the Stage Tower
No full textIn recent years in Italy, the renovation or construction of public buildings, especially auditoriums (for music) and theaters (for prose and the lyric) has become a widespread practice in urban restoration of small and medium-sized towns. The most pervasive tendency in contemporary architectural design of auditoriums and theaters is to realize one-space hall without galleries or balconies, with an accurate furniture design. In the case of theaters, the size of the stage tower is comparable to the one of the audience hall and it has an equivalent absorption area similar to the hall one, depending on the scenes equipments in the stage tower. In this paper the results of the analysis of acoustic requirements of a small theatre hall built in San Miniato (Tuscany region, Italy) are shown and discussed. The analysis has been conducted using the acoustic simulation software RAMSETE. In particular the influence of the stage tower on the room acoustic has been examined, focusing on the coupling factor between the two spaces
Pratiche alimentari e relazioni sociali: una occasione di apertura ad una riflessione multidisciplinare
No full textGoing 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
Coltivare, cucinare e mangiare (anche a scuola)
No full textIl presente lavoro ha l'intento di indagare come il tema dell'alimentazione sia evoluto nel tempo e, nel mondo occidentale, sia legato non solo al valore nutrizionale, ma anche, e talora in misura maggiore, ad aspetti sociali, identitari, salutistici e terapeutici. In tal senso è stata condotta una ricerca volta da una parte a esplorare le pratiche del coltivare, del cucinare e del mangiare all'interno di strutture protette come penitenziari, scuole, case di riposo, comunità, per un totale di 153 strutture; e dall'altra a valutare in quale misura esse siano più o meno legate alle funzioni educative, economiche, sociali e terapeutiche. La metodologia utilizzata si è servita di un questionario semistrutturato compilato insieme ai responsabili delle strutture o agli addetti ai lavori all'interno di tali istituzioni.
Il carattere "relazionale" del cibo è un "tratto fondamentale e fondante sempre presente nella sfera alimentare [...] che ha sempre avuto una sorta di affordance, manifestando non solo la sua necessità come nutrimento ma anche come legame sociale, come connettore di umanità e occasione di scambio e condivisione" (Leveghi, 2015, p. 7). Un altro concetto che si sostanzia nelle pratiche alimentari e vi attribuisce forma e significato sembra essere l'accessibilità sia individuale sia collettiva ai tre momenti (coltivare, cucinare, nutrirsi). In questo senso, la struttura spazio-temporale sviluppata da Torsten Hägerstrand (1970) e l'analisi delle costrizioni temporali nelle quali incorrono gli individui, sono state integrate con le specifiche scelte sociali che concorrono a determinare la creazione e le rappresentazioni dei luoghi e degli spazi delle pratiche alimentari.
Un breve excursus consente di collocare il ragionamento nei vari contesti storici, per interpretare i tre "momenti" nei rispettivi legami col territorio e individuare le scelte culturali specifiche. Il risultato è la classificazione dei luoghi e degli spazi prevalenti nelle pratiche alimentari delle comunità considerate in tre gruppi: funzionali, strutturali, effimeri
Argomenti per un sommario: diritti e differenze tra istituzionalizzazione e progettazione sociale
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