1,720,979 research outputs found
Preliminary Sizing of an Hypersonic Airbreathing Airliner
No full textThe purpose of this paper is to identify, for given technology levels (TRL) and mission requirements, those parameters
that are critical for preliminary sizing of a hypersonic airbreathing airliner. Mission requirements will dictate a solution
space of possible vehicle architecture capable of meeting cruise conditions as well as of taking-off (TO) and landing. In
practice, once defined a range of cruise vehicle architectures, constraints are imposed (as to all passenger airliners), such as:
1. take off (=TO) and landing distance (so-called field length, FL): FL no longer than for the B-747-400, or 10000 ft; 2.
completing TO with one engine off; 3. max acceleration at TO and climb-out (CO) = 0.4 g; 4. Hydrogen fuel (Meeting NOx
emission limits (EINOx) is a further constraint not discussed in this paper).
These constraints enable focusing on a realistic design out of the broad range of vehicles capable of performing the given
mission. Thus a realistic vehicle must not only integrate aerodynamics and propulsion system; in fact, it is the result of
many iterations in the design space, until performance and constraints are successfully achieved and met.
The Gross Weight at Take Off (TOGW) was deliberately discarded as a constraint, based on Previous studies by Czysz.
Typically, limiting from the beginning the TOGW leads to a vicious spiral where weight and propulsion system
requirements keep growing, eventually denying convergence. In designing passenger airliners, in fact, it is the payload
that is assumed fixed from the start, not the total weight.
A parametric analysis of the hypersonic vehicle architecture is presented: in particular, optimal size, weight and
geometrical shape are defined for different mission requirements. This analysis has shown that, it is possible to define a
range of possible successful solutions for the European LAPCAT II project
Unusual cerebral malformations in the Apert syndrome. A report of two newborn infants [Rare malformazioni cerebrali nella sindrome di Apert. Descrizione di due casi in età neonatale]
No full text
Il trattamento delle fratture dell'estremità distale dell'omero
No full textThe treatment of humeral articular fractures, just like that of any other fracture, must be directed to obtain the best possible anatomical reconstruction. The osteosynthesis has to give a good stability to allow an early mobilization ofthe limb. In our study we reviewed the results from the surgical treatment of distal humerus fractures in patients operated in our Orthopaedic Department of the University of`Trieste, from 1995 to 2003. The group counts 73 patients with an average follow-up of over 6 years. All patients had been operated with an open osteosynthesis. The clinical evaluation followed the Cassebaum scheme; we also evaluated heterotopic ossifications. The group of patients studied has revealed to be significant for a long-term study for the following reasons: a) it is representative for all AO types of fractures; b) patients' age ranged from 20 to 86 years; c) many cases had associated lesions (which gives a good glance of how patients were managed in these situations); d) the study was executed by only one orthopaedic, with a uniform method. Results were excellent in 23 cases (31.5%), good in 27 cases (37.0%), satisfactory in 18 cases (24.7%) and bad in 5 (6.8%). Concluding, we can state that distal humerus fractures are not frequent yet severe fractures. Their treatment requires an accurate pre-operatory planning; good surgical experience and a good postoperatory rehabilitation
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
Sizing of TBCC Hypersonic Airbreathing Vehicles
No full textWith the overall goal to clarify the physics of compressible (supersonic) combustion, a 3D LES of the HyShot supersonic combustor has been performed and is reported in this paper. HyShot is an (originally) Australian program to assess feasibility of supersonic combustion by means of a ballistic test flight. The HyShot combustion chamber is shaped as a box 75×9.8 mm in cross section and 300 mm long. Hydrogen is injected at 90 degrees with respect to the supersonic airstream 40 mm downstream from the combustor inlet by means of four 2 mm diameter choked orifices. Air enters the channel at a Mach number that, in the actual test, depended on the flight trajectory; in this simulation, the trajectory point is that at height = 28 km, where the Mach number was 2.79, P=82.11 kPa and T = 1229 K. A structured grid of about 14×106 nodes discretizes the actual combustor shape, where hydrogen-air combustion is treated by means of a detailed chemical kinetics model including 9 species and 37 reactions. Numerical results indicate that hydrogen penetrates in the air stream generating 3D bow shock structures upstream of the injection orifices as seen in experiments. In these regions recirculation zones upstream and downstream of the fuel injection orifices are observed as expected; the OH predicted by LES indicates that a flame starts already in the upstream recirculation zone. Interactions among the essentially 1D airstream entering the combustor, the heat released and the 3D jets produce large vorticity rates and therefore enhance and accelerate turbulent mixing. Combustion is predicted very fast and efficient: only 0.5% of hydrogen is found unburned at the combustor exit. Copyright © 2010 by A. Ingenito and C. Bruno
Il gesso in natura e nell’arte
No full textAbstract
Gypsum (CaSO4 ∙ 2H2O) is a relatively common mineral forming mainly by evaporation of seawater.
The Mediterranean basin has been the cradle for the use of gypsum in art because large outcrops are widespread throughout the entire region. The gypsum here is mainly a result of the “salinity crisis”, which about 6 million years ago (Messinian) deposited a succession of up to 400 m in total thickness, divided into two main units: the Lower and the Upper Gypsum. This relatively younger deposits together with older minor deposits of Permian, Triassic, Cretaceous and Miocene age can be found in Albania, Algeria, Austria, Cyprus, Egypt, France, Greece, Israel, Italy, Jordan, Spain, Tunisia, Turkey. Outside the Mediterranean basin significant gypsum rocks with an archaeological interest are present in Iraq.
Gypsum was quarried in ancient time for in three main uses: 1) construction stone and sculptures, 2) windows panels (lapis specularis) and 3) binder for mortar, plaster and stucco works.
1) As construction stone, gypsum rocks were used because of their candid (microcrystalline alabaster) or sparkling (selenite large crystals) attractive appearance and because these rocks are light, soft, easy to cut, shape and carve.
Examples are the Minoan Crete (since the middle Bronze Age), including the famous Minos throne (alabaster), the palaces and temples of ancient Assyria (alabaster, 9th-7th century BCE), the walls in Eraclea Minoa in Sicily (selenite, 6th-1st BCE), the Etruscan cinerary urns in Tuscany (alabaster 5th-1st BCE), the ancient city wall of Bologna (selenite, 5th-8th CE).
2) cleavage fragments of large transparent crystals (lapis specularis) were used by the Romans in windows panels instead of glass; the crystals were quarried in Cyprus, Italy, Spain, Turkey and Northern Africa. Best examples are from Pompeii (1st CE, Italy).
3) the property of gypsum to harden when mixed with water after being dehydrated in kilns gave rise to its use as a binder in mortar, stucco and plasterworks; prestigious examples are: the art of carved stucco works of the Islamic world such as the Moroccan Medersas (14th-16th CE), the royal palace of the Alhambra in Granada (Spain, 14th CE), the pink mortars prepared from the Triassic gypsum of Albarracín (Spain) and Sologno (Italy) and the Scagliola colorata handicrafts panels imitating semiprecious stone works in Carpi (Italy, 17th-18th CE); ornamental stones were imitate in panels and entire columns in Germany and Italy starting since the 16th CE; stucco decorations were one of the distinguishing features of the exuberance of the Baroque and Rococo art.
Riassunto
Il gesso (CaSO4 ∙ 2H2O) è un minerale relativamente comune che si forma principalmente per evaporazione dell'acqua di mare. Il bacino del Mediterraneo è stato la culla per l'uso del gesso nell'arte perché estesi affioramenti sono diffusi in tutta la regione. Il gesso nell’area mediterranea è principalmente il risultato della "crisi della salinità", che circa 6 milioni di anni fa (Messiniano) ha depositato una successione di fino a 400 m di spessore totale, suddivisa in due unità principali: i Gessi Inferiori e i Gessi Superiori. Questi depositi relativamente più giovani insieme a depositi minori di età permiana, triassica, cretacea e miocenica si trovano in Albania, Algeria, Austria, Cipro, Egitto, Francia, Grecia, Israele, Italia, Giordania, Spagna, Tunisia, Turchia. Al di fuori del bacino del Mediterraneo rocce di gesso di interesse geoarcheologico sono presenti in Iraq.
Il gesso veniva estratto nei tempi antichi per tre usi principali: 1) pietra da costruzione e sculture, 2) pannelli di finestre (lapis specularis) e 3) leganti per malte, intonaci e stucchi.
1) Come pietra da costruzione, le rocce gessose sono state utilizzate a causa del loro aspetto candido (alabastro microcristallino) o scintillante di grandi cristalli (selenite) e perché queste rocce sono leggere e tenere, quindi facili da tagliare, modellare e scolpire. Troviamo esempi significativi nella Creta minoica (dall'età del bronzo medio), tra cui il famoso trono Minosse (alabastro), i palazzi e i templi dell'antica Assiria (alabastro, IX-VII secolo a.C.), le mura di Eraclea Minoa in Sicilia (selenite, VI-I a.C.), le urne cinerarie etrusche in Toscana (alabastro V-I a.C.), l'antica cinta muraria di Bologna (selenite, V-VIII d.C.).
2) frammenti di sfaldatura di grandi cristalli trasparenti, lapis specularis, furono usati dai Romani in pannelli di finestre al posto del vetro; i cristalli venivano estratti a Cipro, Italia, Spagna, Turchia e Nord Africa. I migliori esempi si trovano a Pompei (I secolo d.C.).
3) la proprietà del gesso da indurire una volta mescolato con acqua dopo essere stato disidratato nelle fornaci ha dato origine al suo utilizzo come legante in malte, stucchi e intonaci; esempi prestigiosi sono l'arte dello stucco intagliato del mondo islamico, come nelle mederse marocchine (XIV-XVI secolo), il palazzo reale dell'Alhambra a Granada (Spagna, XIV secolo), gli intonaci rosa preparati con il gesso Triassico ad Albarracín (Spagna) e Sologno (Italia) e i pannelli in scagliola colorata ad imitazione dei commessi in pietra dura a Carpi (Italia, XVIII-XVIII secolo); i primi esempi di imitazione delle pietre ornamentali in pannelli e intere colonne sono documentati in Germania e in Italia a partire dal XVI secolo; le decorazioni in stucco di gesso erano veri e propri tratti distintivi dell'esuberanza dell'arte barocca e rococò
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