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| 2. |
- Lacagnina, Giovanni, et al.
(författare)
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Effects of spatial resolution on PIV investigation of a turbulent orifice jet
- 2012
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Ingår i: 16th International Symposium on Applications of Laser Techniques to Fluid Mechanics, Lisbon.
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Konferensbidrag (refereegranskat)abstract
- Some of the most interesting turbulent phenomena are jets, the study of which is useful to reach a deep knowledge of mixing in fluids. Among all jets, there exists one, the orifice jet, which is still not fully understood because of its intrinsic complexity, e.g. the "vena contracta" phenomenon, though its wide range of applications ranging over underwater propulsion, pollution dispersion and studies on the cardiocirculatory system. In this work, the attention is focused to the large-scale statistics (mean field and higher statistical moments of the velocity) and to the small-scale statistics (velocity derivative statistical moments), with a special care regarding the effect of spatial resolution on Particle Image Velocimetry (PIV) measurements. To investigate the effect of spatial resolution on the measurements, framed areas of different size have been considered by changing the magnification factor (namely the object plane distance). Making reference to the orifice diameter D, squared regions 2D x 2D, 3D x 3D, 4D x 4D and 5D x 5D have been framed on the acquisition camera. Regarding to the large scales, first of all the occurrence of the vena contracta phenomenon for an orifice jet has been shown in several ways. In addition, it has been highlighted the small influence of spatial resolution on low order statistical moments, which slightly rises, due to local averaging, as the order of the statistics becomes higher. Then small scale features of the jet have been examined, particularly with interest to the evaluation of spatial derivatives of velocity components and then to the fulfillment of isotropy hypotheses of the jet. Based on those data, an incomplete local isotropy condition is attained, although restricted to the near zone, and an influence of spatial resolution high on the determination of local features of such a jet and moderate on the overall behavior of spatial derivatives and to the deductions about symmetry hypotheses.
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| 3. |
- Lacagnina, Giovanni, 1982-, et al.
(författare)
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PIV investigations on optical magnification and small scales in the near-field of an orifice jet
- 2015
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Ingår i: Experiments in Fluids. - : Springer. - 0723-4864 .- 1432-1114. ; 56
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Tidskriftsartikel (refereegranskat)abstract
- Among turbulent jets, the orifice jet is still far from being fully understood especially due to the phenomenon of “vena contracta”, which takes place in the near field. In this work, the attention is focused to large-scale statistics (mean field and higher statistical moments of the velocity) and to small-scale statistics (velocity derivative statistical moments) of such a jet, with a special focus onto the effect of optical magnification on particle image velocimetry measurements. In order to investigate this effect on the measurements, framed areas of different size have been considered by changing the magnification factor through the object plane distance. The obtained results show that a limit on the choice of this parameter exists for a proper description of both small and large scales.
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| 4. |
- Lacagnina, Giovanni, 1982-, et al.
(författare)
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Simultaneous size and velocity measurements of cavitating microbubbles using interferometric laser imaging
- 2011
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Ingår i: Experiments in Fluids. - : Springer Science and Business Media LLC. - 0723-4864 .- 1432-1114. ; 50, s. 1153-1167
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, interferometric laser imaging droplet sizing—ILIDS—is applied to incipient cavitation in the wake of a marine propeller model with the aim to evaluate simultaneously bubbles velocity and diameter. Until now, the feasibility of this technique has been demonstrated especially in sprays of water droplets in air where an optimal light scattering is obtained thanks to the spherical shape and to the given relative refractive index. In the present setup, to allow simultaneous size–velocity measurements, a single camera is used and the object distance over lens diameter ratio is kept as small as possible, thus increasing the size measurement resolution. These details, together with the algorithms used for image analysis at each single frame and in two consecutive frames, allow deriving cavitation bubble size and velocity distributions in the propeller wake.
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| 5. |
- Sinibaldi, Giorgia, et al.
(författare)
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Aeroacoustics and aerodynamics of impinging supersonic jets : Analysis of the screech tones
- 2013
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Ingår i: Physics of fluids. - : American Institute of Physics (AIP). - 1070-6631 .- 1089-7666. ; 25:8
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between acoustics and aerodynamics of a supersonic jet is an actual fundamental topic which has been a matter of discussion in the last decades. The present paper is devoted to the experimental analysis of free and impinging jets with particular attention on the effect of an impinging surface on screech tones. The acoustics is studied using free-field microphones, while Particle Image Velocimetry is used to investigate the velocity field. The analysis of acquired data allowed to verify and explain the coupling between acoustic discrete tones and mean and fluctuating flow velocities.
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| 6. |
- Sinibaldi, Giorgia, et al.
(författare)
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Analysis of the Characteristic Acoustic Tones of an Impinging Jet
- 2013
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Ingår i: 19th AIAA/CEAS Aeroacoustics Conference. - Reston, Virginia : American Institute of Aeronautics and Astronautics. - 9781624102134
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Konferensbidrag (refereegranskat)abstract
- The acoustic emission of a supersonic jet is an interesting and fundamental issue due to the several technological applications and the diverse physical aspects to be still clarified. An experimental analysis of the characteristic acoustic tones of a supersonic impinging jet has been carried out with a particular attention on the effect of the nozzle pressure ratio and the distance of the impinging surface. The screech tones, typical of an imperfectly expanded supersonic free jet, have been first investigated to have an idea of the deflection from the free jet behavior due to the impinging surface. Then the analysis has been focused on smaller distances of the impinging plate from the jet exit to evaluate the behavior of the impinging tones. The difference between screech and impinging tones, due to the different interactions in the generating feedback mechanism, has been observed.
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| 7. |
- Cavarretta, Elena, et al.
(författare)
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The role of echocardiography in sports cardiology : An expert opinion statement of the Italian Society of Sports Cardiology (SIC sport)
- 2024
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Ingår i: International Journal of Cardiology. - 0167-5273. ; 410
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Tidskriftsartikel (refereegranskat)abstract
- Transthoracic echocardiography (TTE) is routinely required during pre-participation screening in the presence of symptoms, family history of sudden cardiac death or cardiomyopathies <40-year-old, murmurs, abnormal ECG findings or in the follow-up of athletes with a history of cardiovascular disease (CVD). TTE is a cost-effective first-line imaging modality to evaluate the cardiac remodeling due to long-term, intense training, previously known as the athlete's heart, and to rule out the presence of conditions at risk of sudden cardiac death, including cardiomyopathies, coronary artery anomalies, congenital, aortic and heart valve diseases. Moreover, TTE is useful for distinguishing physiological cardiac adaptations during intense exercise from pathological behavior due to an underlying CVD. In this expert opinion statement endorsed by the Italian Society of Sports Cardiology, we discussed common clinical scenarios where a TTE is required and conditions falling in the grey zone between the athlete's heart and underlying cardiomyopathies or other CVD. In addition, we propose a minimum dataset that should be included in the report for the most common indications of TTE in sports cardiology clinical practice.
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| 8. |
- Franchini, Mariagrazia, et al.
(författare)
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The Gaia-ESO Survey : Carbon Abundance in the Galactic Thin and Thick Disks
- 2020
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Ingår i: Astrophysical Journal. - : IOP PUBLISHING LTD. - 0004-637X .- 1538-4357. ; 888:2
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Tidskriftsartikel (refereegranskat)abstract
- This paper focuses on carbon, which is one of the most abundant elements in the universe and is of high importance in the field of nucleosynthesis and galactic and stellar evolution. The origin of carbon and the relative importance of massive and low- to intermediate-mass stars in producing it is still a matter of debate. We aim at better understanding the origin of carbon by studying the trends of [C/H], [C/Fe], and [C/Mg] versus [Fe/H] and [Mg/H] for 2133 FGK dwarf stars from the fifth Gaia-ESO Survey internal data release (GES iDR5). The availability of accurate parallaxes and proper motions from Gaia DR2 and radial velocities from GES iDR5 allows us to compute Galactic velocities, orbits, absolute magnitudes, and, for 1751 stars, Bayesian-derived ages. Three different selection methodologies have been adopted to discriminate between thin- and thick-disk stars. In all the cases, the two stellar groups show different [C/H], [C/Fe], and [C/Mg] and span different age intervals, with the thick-disk stars being, on average, older than the thin-disk ones. The behaviors of [C/H], [C/Fe], and [C/Mg] versus [Fe/H], [Mg/H], and age all suggest that C is primarily produced in massive stars. The increase of [C/Mg] for young thin-disk stars indicates a contribution from low-mass stars or the increased C production from massive stars at high metallicities due to the enhanced mass loss. The analysis of the orbital parameters R-med and supports an "inside-out" and "upside-down" formation scenario for the disks of the Milky Way.
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| 9. |
- Franchini, Mariagrazia, et al.
(författare)
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The Gaia-ESO Survey : Oxygen Abundance in the Galactic Thin and Thick Disks*
- 2021
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Ingår i: Astronomical Journal. - : Institute of Physics Publishing (IOPP). - 0004-6256 .- 1538-3881. ; 161:1
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the oxygen abundances of a stellar sample representative of the two major Galactic populations: the thin and thick disks. The aim is to investigate the differences between members of the Galactic disks and contribute to the understanding of the origin of oxygen chemical enrichment in the Galaxy. The analysis is based on the [O i] = 6300.30 A oxygen line in high-resolution spectra (R similar to 52,500) obtained from the Gaia-ESO public spectroscopic Survey (GES). By comparing the observed spectra with a theoretical data set computed in LTE with the SPECTRUM synthesis and ATLAS12 codes, we derive the oxygen abundances of 516 FGK dwarfs for which we have previously measured carbon abundances. Based on kinematic, chemical, and dynamical considerations, we identify 20 thin and 365 thick disk members. We study the potential trends of both subsamples in terms of their chemistry ([O/H], [O/Fe], [O/Mg], and [C/O] versus [Fe/H] and [Mg/H]), age, and position in the Galaxy. The main results are that (a) [O/H] and [O/Fe] ratios versus [Fe/H] show systematic differences between thin and thick disk stars with an enhanced O abundance of thick disk stars with respect to thin disk members and a monotonic decrement of [O/Fe] with increasing metallicity, even at metal-rich regime; (b) there is a smooth correlation of [O/Mg] with age in both populations, suggesting that this abundance ratio can be a good proxy of stellar ages within the Milky Way; and (c) thin disk members with [Fe/H] 0 display a [C/O] ratio smaller than the solar value, suggesting a possibly outward migration of the Sun from lower Galactocentric radii.
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| 10. |
- Jung, Christian, et al.
(författare)
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A comparison of very old patients admitted to intensive care unit after acute versus elective surgery or intervention
- 2019
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Ingår i: Journal of critical care. - : W B SAUNDERS CO-ELSEVIER INC. - 0883-9441 .- 1557-8615. ; 52, s. 141-148
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Tidskriftsartikel (refereegranskat)abstract
- Background: We aimed to evaluate differences in outcome between patients admitted to intensive care unit (ICU) after elective versus acute surgery in a multinational cohort of very old patients (80 years; VIP). Predictors of mortality, with special emphasis on frailty, were assessed.Methods: In total, 5063 VIPs were induded in this analysis, 922 were admitted after elective surgery or intervention, 4141 acutely, with 402 after acute surgery. Differences were calculated using Mann-Whitney-U test and Wilcoxon test. Univariate and multivariable logistic regression were used to assess associations with mortality.Results: Compared patients admitted after acute surgery, patients admitted after elective surgery suffered less often from frailty as defined as CFS (28% vs 46%; p < 0.001), evidenced lower SOFA scores (4 +/- 5 vs 7 +/- 7; p < 0.001). Presence of frailty (CFS >4) was associated with significantly increased mortality both in elective surgery patients (7% vs 12%; p = 0.01), in acute surgery (7% vs 12%; p = 0.02).Conclusions: VIPs admitted to ICU after elective surgery evidenced favorable outcome over patients after acute surgery even after correction for relevant confounders. Frailty might be used to guide clinicians in risk stratification in both patients admitted after elective and acute surgery.
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