Studio della fluidodinamica del sistema di ricambio della carica di un motore ad alte prestazioni per la formula SAE

Ottimizzare le prestazioni di un motore a combustione interna è una delle principali attività di studio e interesse da parte delle aziende automotive soprattutto perchè presenta diverse sfaccettature a seconda dell'obiettivo che ci si prepone: aumentare la potenza in un determinato range di funzionamento, rendere il motore più elastico, diminuire i consumi o le emissioni inquinanti. Ognuno di questi aspetti richiede un ampio lavoro di studio preliminare, di progettazione e di prove, sia numeriche che sperimentali. Il presente studio riguarda l'ottimizzazione di un motore di provenienza motociclistica adattato per essere montato su una monoposto per la Formula SAE tramite la progettazione completa del sistema di aspirazione e scarico. Vista la doppia natura di questo lavoro, sia teorica che applicativa, è stato fatto un modello numerico dell'intero sistema, sia con un codice monodimensionale, il Ricardo Wave, con il quale è stato studiato il comportamento globale, sia con codice di calcolo CFD tridimensionale, in particolare con il software Solidworks per la costruzione della geometria, Gambit per la creazione della Mesh e Fluentper l'analisi della fluidodinamica, utilizzato per analizzare il comportamento del flusso nei punti critici quali la flangia, in cui si può instaurare un regime di flusso critico, detto strozzato, o il plenum, la cui dimensione e geometria hanno influenza sul comportamento del motore. E' importante notare come questo studio faccia parte di un più ampio progetto di un veicolo da competizione completo, il che ha di fatto imposto dei limiti di geometria, peso e ingombro totale, definendo quindi quei confini dati dalla fattibilità e dai problemi di layout che un lavoro puramente teorico può, in linea di principio, non considerare

Aeroelastic stability of two long-span arch structures: A collaborative experience in two wind tunnel facilities

In this paper, a rare example of comparison between sectional and full-aeroelastic model tests is presented. Interestingly, the experiments were conducted in two very different wind tunnel facilities by different research teams. The study concerns two long-span steel arch structures recently built in Milan, Italy, for Expo 2015 World Fair. The structures have only aesthetic purposes and are therefore very flexible and light, which makes them sensitive to wind-induced excitation and prone to aeroelastic instabilities. In particular, in smooth flow an interesting phenomenon of interference between vortex-induced vibration and galloping was observed up to high values of the Scruton number. This aeroelastic instability is very dangerous as large-amplitude vibrations can occur in wind speed ranges where they are not expected, at least for what classical theories for vortex-induced vibration and quasi-steady galloping are concerned. Moreover, the provisions of Eurocode 1 resulted clearly unsuitable and non-conservative to address such a phenomenon. Despite the differences in the facilities and in the models, a good agreement was found between the results obtained in the two laboratories. The major discrepancies were observed in the transitional behavior for intermediate values of the Scruton number, the sectional model showing a more unstable behavior. The tests on the full-aeroelastic model also allowed considering the effect of the angle of wind exposure of the structures, both the in-plane and the out-of-plane vibrations of the arches and the dynamic response to turbulent wind. In particular, a set of tests in smooth flow was performed accounting for the presence of the other arch and of the surrounding buildings. A particular dynamic excitation of the in-plane flexural modes of the structures was observed in well defined ranges of flow speeds when one arch is in the wake of the other. Finally, both experimental campaigns highlighted the need for the installation of tuned mass dampers on the real structures to guarantee their safety. The effectiveness of these devices against the observed galloping-type instability was also verified through wind tunnel tests on the full-aeroelastic model

On construction and (non)existence of cc-(almost) perfect nonlinear functions

Functions with low differential uniformity have relevant applications in cryptography. Recently, functions with low $c$-differential uniformity attracted lots of attention. In particular, so-called APcN and PcN functions (generalization of APN and PN functions) have been investigated. Here, we provide a characterization of such functions via quadratic polynomials as well as non-existence results

Complete (q+1)(q+1)-arcs in PG(2,Fq6)\mathrm{PG}(2,\mathbb{F}_{q^6}) from the Hermitian curve

We prove that, if $q$ is large enough, the set of the $\mathbb{F}_{q^6}$-rational points of the Hermitian curve is a complete $(q+1)$-arc in $\mathrm{PG}(2,\mathbb{F}_{q^6})$, addressing an open case from a recent paper by Korchm\'aros, Sz\H{o}nyi and Nagy. An algebraic approach based on the investigation of some algebraic varieties attached to the arc is used

On construction and (non)existence of c-(almost) perfect nonlinear functions

Functions with low differential uniformity have relevant applications in cryptography. Recently, functions with low c-differential uniformity attracted lots of attention. In particular, so-called APcN and PcN functions (generalization of APN and PN functions) have been investigated. Here, we provide a characterization of such functions via quadratic polynomials as well as non-existence results.publishedVersio

An easily recoverable and recyclable homogeneous polyester-based Pd catalytic system for the hydrogenation of α,β-unsaturated carbonyl compounds

Homogeneous catalysis is an efficient tool to carry out hydrogenation processes but the major drawback is represented by the separation of the expensive catalyst from the product mixture. In this view we prepared a polyester-based Pd catalytic system that offers the advantages of both homogenous and heterogeneous catalyses: efficacy, selectivity and recyclability. Here its application in the hydrogenation of selected alpha,beta-unsaturated carbonyl compounds is described

Minimal codewords in Norm-Trace codes

In this paper, we consider the affine variety codes obtained evaluating the polynomials $by=a_kx^k+\dots+a_1x+a_0$, $b,a_i\in\mathbb{F}_{q^r}$, at the affine \F_{q^r}-rational points of the Norm-Trace curve. In particular, we investigate the weight distribution and the set of minimal codewords. Our approach, which uses tools of algebraic geometry, is based on the study of the absolutely irreducibility of certain algebraic varieties