1,721,038 research outputs found
Smart Morphing Concepts and Applications for Advanced Lifting Surfaces
No full textIn this research study, aeronautical "structural" morphing has been considered, focused
on seamless structural wing shape adaptation, inspired by biologicallife.
Available literature (Chapter 2) shows that international interest in the aeronautical field
is focused in the morphing of specific wing parameters, such as leading or trailing edge
curvature, wing torsion, wing span change, etc., each capable of generating
aerodynamic advantages or better adaptability over a traditional design.
Moreover, to overcame weight, mechanical complexity and costs penalties introduced
by morphing architectures, many of these solutions adopt smart materials as actuators.
Among them, Shape Memory Alloys have attracted a lot of attention and are present in
many applications, due to their favourable force/volume or force/weight ratio: state of
the art about SMAs features, numerical modelling and characterization is presented in
Chapter 3.
The chief objective of this dissertation is to propose plausible architectural solutions for
changing different geometrical parameters of an airfoil; many of them integrate Shape
Memory Alloys within the structure, having both actuation and load-bearing role.
In particular, three airfoil parameters have been taken into account:
airfoil (upper) bump;
airfoil camber at trailing edge (morphing flap);
airfoil chord.
The formation of an airfoil upper bump is one of the first experiences in the morphing
field done by the author and researchers at CIRA: it represents one of the less invasive
possible morphing techniques, not affecting the wing primary load-bearing structure,
and capable of introducing some benefits in transonic regime (Chapter 4).
Then, activities moved towards a greater level of integration and interaction within the
wing structure, trying to substitute a traditional hinged flap with a variable camber
trailing edge, also known as morphing flap (Chapter 5). In parti cular , literature showed
a dearth of real scale applications of morphing technologies with smart materials to civil
transportation class aircrafts. Basing on the partnership with Alenia Aeronautica Spa
industry (which founded part of these activities) , innovative concepts for a morphing
flap have been conceived, suitable for real scale regional transportation aircrafts;
expertise at CIRA in modeling and characterization of Shape Memory Alloys allowed
for an high integration of these alloys both as actuators and structural load-bearingelements. Results of this collaboration brought to the design and manufacture of a
SMA-based actuator (Chapter 6) and a morphing flap architecture highly integrating
such an actuator devi ce (Chapter 7). Moreover, these research activities have raised
great interest in the industriaI partner (Alenia): a patent is pending on both devices
(Appendix) and further studies and collaborations are currently starting.
Finally, new research activities started in the branch of variable chord are presented
(Chapter 8). Chord morphing has the power to increase the airfoil surface and, so, its
lifting capab il ity. Something similar already happens for high lift devices on
transportation aircrafts, where the typical single/double slotted solution for trailing edge
flaps allow not only to increase wing curvature, but also its chord (that is, wing area).
The possibility to match the greater aerodynamic efficiency of a morphing flap with an
airfoil chord (wing area) increase could lead to even better aerodynamic performance.
In this work, an early concept has been studied and manufactured for a morphing
rotorcraft bIade, basing on a three-month collaboration with the Department of
Aerospace Engineering of the Pennsylvania State University (with particular reference
to the Vertical Lift Research Centre of Excellence (VLRCOE)).
The thesis, where possible, has been produced as a collection of publications (both on
journals and to conferences). However, due to the patent pending on some of the
presented activities and prototypes, great part of the research activities has not been
published yet at the moment of writing: for this reason, some chapters will be offered as
traditional reports.
Therefore, the dissertation is organized as follows:
Chapter 2 treats the worldwide state of the art in morphing technologies through
a survey of aeronautical applications that can be found in literature, focused in
the optimization of specific wing parameters, using traditional actuators or
Shape Memory Alloys;
Chapter 3 overviews the Shape Memory Alloys micromechanics and
macroscopic behaviour, together with material modelling and characterization;
then, current applications in various fields exploiting either the super-elastic or
shape memory effect are presented, jointly with new discovered materials in the
"shape memory" field;
Chapter 4 introduces the first studied morphing application, focused on the
bump formation on the upper wing skin for transonic drag reduction (paper): a
device integrating Shape Memory AlIoys has been designed, manufactured and
tested;
Chapter 5 reviews some preliminary studi es carried out toldentify possible
morphing solutions, actuated by SMAs elements, to produce a camber change
Iocalized to the aft part of a wing airfoil, so to mimic a trailing edge flap: several
architectures are presented and numerical results discussed (various papers);
Chapter 6presents the conceived SMA-based smart actuator, expIaining in great
detail its design features and alI the considerations, numerical simulations and
optimizations which brought to the final prototype, experimentalIy tested and
characterized;
Chapter 7 shows in detail an application of the developed smart actuator to a
real scale morphing architecture abIe to mimic a trailing flap: after numerical
simulations, the solution has been built and prototype tested also in presence of
static Ioads;
Chapter 8 deals with the other morphing parameter taken into account in this
research, that is airfoil chord, introducing an early concept for a morphing
rotorcraft bIade, its design constraints and the realized prototype;
Chapter 9 c10ses and comments on the work presented, discussing also future
deveIopments.
Finally, an Appendix is present, reproducing the patent communication from the
European Patent Office with all the details
Sistemi a Phased Array di Microfoni per Identificazione, Localizzazione e Inseguimento di Aeromobili
No full textL'obiettivo principale della Tesi di Dottorato è stato quello di realizzare un sistema prototipale acustico innovativo, basato su sistemi passivi a phased array di microfoni per l’identificazione, la localizzazione e l’inseguimento di una sorgente di rumore in movimento, con particolare riferimento agli aeromobili. Le metodologie sviluppate sono state sperimentali, numeriche e teoriche. Nella prima parte del lavoro di tesi è stato affrontato il problema della localizzazione di sorgenti di rumore singole e multiple. Partendo da un’analisi dettagliata dello stato dell’arte sono state selezionate le tecniche di Time Delay of Arrival e Beam-forming. E’ seguita una fase applicativa, riguardante la progettazione teorico/numerica, la realizzazione e la messa a punto di un sistema prototipale per la localizzazione ed il tracking di una o più sorgenti di rumore in movimento. Il sistema è stato validato numericamente nel caso di più sorgenti simultanee e sperimentalmente per una singola sorgente nella camera anecoica disponibile al CIRA. In una seconda parte, è stato affrontato il problema della identificazione di una sorgente di rumore in base al riconoscimento della sua firma acustica. Partendo da un’analisi dettagliata dello stato dell’arte, è stata messa a punto una tecnica innovativa basata sulla decomposizione wavelet del segnale di rumore e su un classificatore a reti neurali. Si è proceduto con una fase applicativa, riguardante la progettazione, la realizzazione e la messa a punto di un sistema prototipale per la classificazione di una sorgente di rumore. Il sistema è stato validato sperimentalmente mediante una campagna di misura del rumore emesso da cinque differenti aeromobili nelle fasi di decollo e atterraggio presso l’aeroporto di Capodichino. I principali risultati ottenuti hanno riguardato la definizione e dimostrazione prototipale di un sistema acustico innovativo che, attraverso il superamento delle principali limitazioni tecnologiche dei sistemi esistenti, introduce significative innovazioni metodologiche e tecnologiche nel campo del controllo del traffico aereo, consentendo l’identificazione e il tracciamento degli aeromobili in volo e a terra mediante il rilevamento passivo e l’ analisi wavelet (tempo-frequenza) delle emissioni acustiche dei velivoli stessi. Lo sfruttamento dei risultati della ricerca consentirà l’industrializzazione di un sistema acustico di controllo del traffico aereo in zona di aerodromo del tutto innovativo, in grado di contribuire all’incremento di competitività a livello nazionale in termini di: miglioramento della sicurezza del sistema di trasporto aereo; riduzione drastica dell’impatto ambientale, grazie all’assenza di emissioni elettromagnetiche; riduzione dei costi di implementazione e gestione del servizio di controllo del traffico aereo. Il sistema prototipale sviluppato è stato citato nella sezione “Offers Industrial Technologies” nell’articolo “Limiting the problem of noise pollution at airports”, del CORDIS (www.cordis.europa.eu), il servizio di informazione telematico comunitario in materia di ricerca e sviluppo per la scienza, fonte d'informazione ufficiale per gli inviti a presentare proposte nell'ambito dei programmi Quadro. Uno degli scopi principali del CORDIS è di migliorare l'utilizzo dei risultati delle ricerche da parte delle imprese comunitarie ponendo l'accento sui settori essenziali per la competitività dell'Europa
Manufatti piezoelettrici organici ottenuti a partire da precursori liquidi di basso peso molecolare.
No full textI materiali piezoelettrici sono ampiamente usati come sensori elettromeccanici in svariati settori dell’industria; essi, infatti, producono una risposta elettrica a seguito di una sollecitazione meccanica (effetto piezoelettrico diretto), o una risposta meccanica a seguito di una sollecitazione elettrica (effetto piezoelettrico inverso). Molto diffusi sono i materiali piezoelettrici inorganici, o quelli polimerici a base di poli(vinilidenefluoruro). La presente richiesta di brevetto si riferisce all’invenzione di nuovi manufatti piezoelettrici basati su materiali completamente organici, ottenuti da precursori liquidi di basso peso molecolare ed elevato momento di dipolo elettrico, non polimerici. Il precursore liquido è versato in opportuno stampo e, tramite una procedura di orientamento sotto alto campo elettrico, le molecole vengono allineate, in media, coi loro dipoli elettrici paralleli al campo elettrico; una contemporanea reticolazione chimica rende permanente tale allineamento, portando all’ottenimento di un manufatto non centrosimmetrico, piezoelettrico, della forma desiderata. Si dimostra, inoltre, risposta piezoelettrica in un esempio di materiale di questo tipo
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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