Performance Simulation of Marine Cycloidal Propellers: A Both Theoretical and Heuristic Approach

open4The importance of mathematical and numerical simulation in marine engineering is growing together with the complexity of the designed systems. In general, simulation a makes it possible to improve the engineering design, reducing working time and costs of production as well. In this respect, the implementation of a simulation model for cycloidal propellers is presented. Cycloidal thrusters are being increasingly used in marine applications. Their best performance concerns low-speed applications, due to their ability to steer thrust in any direction. The proposed simulator is able to assess the performance of cycloidal propellers in terms of the generated thrust and torque, without resorting to consuming and demanding computational tools, such as CFD methods. This feature makes the presented model particularly suitable for the simulation in the time domain of the maneuverability of surface units, equipped with cycloidal propellers. In this regard, after embodying the implemented model in an already existing simulation platform for maneuverability, we show the most significant outputs concerning some simulated maneuvers, performed at cruise speed.openMarco Altosole, Silvia Donnarumma, Valentina Spagnolo, Stefano VignoloAltosole, Marco; Donnarumma, Silvia; Spagnolo, Valentina; Vignolo, Stefan

LOFT as a discovery machine for jetted Tidal Disruption Events

This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of jetted tidal disruption events. For a summary, we refer to the paper.Comment: White Paper in Support of the Mission Concept of the Large Observatory for X-ray Timin

The assembly of massive galaxies from NIR observations of the Hubble Deep Field South

We use a deep K(AB)<25 galaxy sample in the Hubble Deep Field South to trace the evolution of the cosmological stellar mass density from z~ 0.5 to z~3. We find clear evidence for a decrease of the average stellar mass density at high redshift, 2<z<3.2, that is 15^{+25}_{-5}% of the local value, two times higher than what observed in the Hubble Deep Field North. To take into account for the selection effects, we define a homogeneous subsample of galaxies with 10^{10}M_\odot \leq M_* \leq 10^{11}M_\odot: in this sample, the mass density at z>2 is 20^{+20}_{-5} % of the local value. In the mass--limited subsample at z>2, the fraction of passively fading galaxies is at most 25%, although they can contribute up to about 40% of the stellar mass density. On the other hand, star--forming galaxies at z>2 form stars with an average specific rate at least ~4 x10^{-10} yr$^{-1}$, 3 times higher than the z<~1 value. This implies that UV bright star--forming galaxies are substancial contributors to the rise of the stellar mass density with cosmic time. Although these results are globally consistent with $\Lambda$--CDM scenarios, the present rendition of semi analytic models fails to match the stellar mass density produced by more massive galaxies present at z>2.Comment: Accepted for publication on ApJLetter

Design and Validation of Dynamic Positioning for Marine Systems: a Case Study

The design of a DP-system is a challenging task with several technical fields involved in the problem solution. Numerical simulation is a powerful tool in order to aid the designer during the system development and to speed up the design process. This paper presents the simulation methodology adopted to design and test the dynamic positioning system for a vessel with a standard propulsion configuration. Simulation results and sea trial measurements are compared to illustrate the reliability of the proposed simulation platform

Valutazione dell'efficacia di un coadiuvante topico a base di argento micronizzato, zinco acetato e acido laurico nel trattamento dell'acne lieve-moderata

L'acne è una dermatosi ad eziopatogenesi multifattoriale in cui differenti fattori contribuiscono al mantenimento del processo infiammatorio. Il ruolo del P. acnes è stato, infatti, rideterminato in quanto trigger principale della risposta infiammatoria, essendo in grado di attivare la liberazione di numerose citochine proinfiammatorie. Non a caso, gli antibiotici sono tra i farmaci cardine della terapia topica dell'acne. Il loro uso è, tuttavia, limitato dallo sviluppo di resistenze batteriche. Ne deriva la necessità di utilizzare nuove molecole, le cui proprietà antibatteriche non siano suscettibili di fenomeni di resistenza. Tra le molecole che hanno destato maggiore interesse, per l'azione antibatterica non antibiotico-dipendente, e, pertanto, non soggetta allo sviluppo di resistenze, annoveriamo l'acido laurico, l'argento micronizzato e lo zinco acetato. Il nostro studio si propone di valutare l'efficacia nel trattamenti dell'acne lieve-moderata di una terapia topica a base di argento micronizzato, acido laurico e zinco acetato attraverso una valutazione sia oggettiva, mediante GAGS e Sebutape, che soggettiva, mediante l'ausilio di un nuovo strumento di valutazione della componente psicologica del paziente acneico: l'acne radar

Powerful high energy emission of the remarkable BL Lac object S5 0716+714

BL Lac objects of the intermediate subclass (IBLs) are known to emit a substantial fraction of their power in the energy range 0.1--10 GeV. Detecting gamma-ray emission from such sources provides therefore a direct probe of the emission mechanisms and of the underlying powerhouse. The AGILE gamma-ray satellite detected the remarkable IBL S5 0716+714 (z \simeq 0.3) during a high state in the period from 2007 September - October, marked by two very intense flares reaching peak fluxes of 200\times10^{-8} ph / cm^2 s above 100 MeV, with simultaneous optical and X-ray observations. We present here a theoretical model for the two major flares and discuss the overall energetics of the source. We conclude that 0716+714 is among the brightest BL Lac's ever detected at gamma-ray energies. Because of its high power and lack of signs for ongoing accretion or surrounding gas, the source is an ideal candidate to test the maximal power extractable from a rotating supermassive black hole via the pure Blandford-Znajek (BZ) mechanism. We find that during the 2007 gamma-ray flares our source approached or just exceeded the upper limit set by BZ for a black hole of mass 10^9 M_sunComment: 12 pages, 3 figure