The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
P L Cottrell - One of the best experts on this subject based on the ideXlab platform.
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Velocity Distribution of stars in the solar neighbourhood
Monthly Notices of the Royal Astronomical Society, 1999Co-Authors: J Skuljan, J B Hearnshaw, P L CottrellAbstract:A two-dimensional Velocity Distribution in the UV plane has been obtained for stars in the solar neighbourhood, using Hipparcos astrometry for over 4000 ‘survey’ stars with parallaxes greater than 10 mas and radial velocities found in the Hipparcos Input Catalogue. In addition to the already known grouping characteristics (field stars plus young moving groups), the Velocity Distribution seems to exhibit a more complex structure characterized by several longer branches running almost parallel to each other across the UV plane. By using the wavelet transform technique to analyse the Distribution, the branches are visible at relatively high significance levels of 90 per cent or higher. They are roughly equidistant with a separation of about 15 km s−1 for early-type stars and about 20 km s−1 for late-type stars, creating an overall quasi-periodic structure which can also be detected by means of a two-dimensional Fourier transform. This branch-like Velocity Distribution might be caused by the Galactic spiral structure.
Scott Tremaine - One of the best experts on this subject based on the ideXlab platform.
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the stellar Velocity Distribution in the solar neighbourhood
Monthly Notices of the Royal Astronomical Society, 2004Co-Authors: Richard S De Simone, Xiaoan Wu, Scott TremaineAbstract:We explore the heating of the Velocity Distribution in the solar neighbourhood by stochastic spiral waves. Our investigation is based on direct numerical integration of initially circular test-particle orbits in the sheared sheet. We confirm the conclusion of other investigators that heating by spiral structure can explain the principal features of the age–Velocity dispersion relation and other parameters of the Velocity Distribution in the solar neighbourhood. In addition, we find that heating by strong transient spirals can naturally explain the presence of small-scale structure in the Velocity Distribution (‘moving groups’). Heating by spiral structure also explains why the stars in a single Velocity-space moving group have a wide range of ages, a result that is difficult to understand in the traditional model in which these structures result from inhomogeneous star formation. Thus we suggest that old moving groups arise from irregularities in the Galactic potential rather than from irregularities in the star formation rate.
J Skuljan - One of the best experts on this subject based on the ideXlab platform.
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Velocity Distribution of stars in the solar neighbourhood
Monthly Notices of the Royal Astronomical Society, 1999Co-Authors: J Skuljan, J B Hearnshaw, P L CottrellAbstract:A two-dimensional Velocity Distribution in the UV plane has been obtained for stars in the solar neighbourhood, using Hipparcos astrometry for over 4000 ‘survey’ stars with parallaxes greater than 10 mas and radial velocities found in the Hipparcos Input Catalogue. In addition to the already known grouping characteristics (field stars plus young moving groups), the Velocity Distribution seems to exhibit a more complex structure characterized by several longer branches running almost parallel to each other across the UV plane. By using the wavelet transform technique to analyse the Distribution, the branches are visible at relatively high significance levels of 90 per cent or higher. They are roughly equidistant with a separation of about 15 km s−1 for early-type stars and about 20 km s−1 for late-type stars, creating an overall quasi-periodic structure which can also be detected by means of a two-dimensional Fourier transform. This branch-like Velocity Distribution might be caused by the Galactic spiral structure.
Richard S De Simone - One of the best experts on this subject based on the ideXlab platform.
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the stellar Velocity Distribution in the solar neighbourhood
Monthly Notices of the Royal Astronomical Society, 2004Co-Authors: Richard S De Simone, Xiaoan Wu, Scott TremaineAbstract:We explore the heating of the Velocity Distribution in the solar neighbourhood by stochastic spiral waves. Our investigation is based on direct numerical integration of initially circular test-particle orbits in the sheared sheet. We confirm the conclusion of other investigators that heating by spiral structure can explain the principal features of the age–Velocity dispersion relation and other parameters of the Velocity Distribution in the solar neighbourhood. In addition, we find that heating by strong transient spirals can naturally explain the presence of small-scale structure in the Velocity Distribution (‘moving groups’). Heating by spiral structure also explains why the stars in a single Velocity-space moving group have a wide range of ages, a result that is difficult to understand in the traditional model in which these structures result from inhomogeneous star formation. Thus we suggest that old moving groups arise from irregularities in the Galactic potential rather than from irregularities in the star formation rate.
Shinobu Koda - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of liquid Velocity Distribution in a sonochemical reactor
Ultrasonics Sonochemistry, 2013Co-Authors: Zheng Xu, Keiji Yasuda, Shinobu KodaAbstract:Abstract Ultrasonically induced flow is an important phenomenon observed in a sonochemical reactor. It controls the mass transport of sonochemical reaction and enhances the reaction performance. In the present paper, the liquid Velocity Distribution of ultrasonically induced flow in the sonochemical reactor with a transducer at frequency of 490 kHz has been numerically simulated. From the comparison of simulation results and experimental data, the ultrasonic absorption coefficient in the sonochemical reactor has been evaluated. To simulate the liquid Velocity near the liquid surface above the transducer, which is the main sonochemical reaction area, it is necessary to include the acoustic fountain shape into the computational domain. The simulation results indicate that the liquid Velocity increases with acoustic power. The variation of liquid height also influences the behavior of liquid Velocity Distribution and the mean Velocity above the transducer centre becomes a maximum when the liquid height is 0.4 m. The liquid Velocity decreases with increasing the transducer plate radius at the same ultrasonic power.
