The Experts below are selected from a list of 76062 Experts worldwide ranked by ideXlab platform
Steven S Vogt - One of the best experts on this subject based on the ideXlab platform.
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ad leonis radial Velocity Signal of stellar rotation or spin orbit resonance
The Astronomical Journal, 2018Co-Authors: Mikko Tuomi, H R A Jones, G Angladaescude, Paul R Butler, Marcin Kiraga, J R Barnes, Steven S VogtAbstract:This is an Open Access article. Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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ad leonis radial Velocity Signal of stellar rotation or spin orbit resonance
arXiv: Earth and Planetary Astrophysics, 2018Co-Authors: Mikko Tuomi, H R A Jones, G Angladaescude, Paul R Butler, Marcin Kiraga, Steven S VogtAbstract:AD Leonis is a nearby magnetically active M dwarf. We find Doppler variability with a period of 2.23 days as well as photometric Signals: (1) a short period Signal which is similar to the radial Velocity Signal albeit with considerable variability; and (2) a long term activity cycle of 4070$\pm$120 days. We examine the short-term photometric Signal in the available ASAS and MOST photometry and find that the Signal is not consistently present and varies considerably as a function of time. This Signal undergoes a phase change of roughly 0.8 rad when considering the first and second halves of the MOST data set which are separated in median time by 3.38 days. In contrast, the Doppler Signal is stable in the combined HARPS and HIRES radial velocities for over 4700 days and does not appear to vary in time in amplitude, phase, period or as a function of extracted wavelength. We consider a variety of star-spot scenarios and find it challenging to simultaneously explain the rapidly varying photometric Signal and the stable radial Velocity Signal as being caused by starspots co-rotating on the stellar surface. This suggests that the origin of the Doppler periodicity might be the gravitational tug of a planet orbiting the star in spin-orbit resonance. For such a scenario and no spin-orbit misalignment, the measured $v \sin i$ indicates an inclination angle of 15.5$\pm$2.5 deg and a planetary companion mass of 0.237$\pm$0.047 M$_{\rm Jup}$.
Suarez A Mascareno - One of the best experts on this subject based on the ideXlab platform.
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hades rv programme with harps n at tng v a super earth on the inner edge of the habitable zone of the nearby m dwarf gj 625
Astronomy and Astrophysics, 2017Co-Authors: Suarez A Mascareno, R Rebolo, J Gonzalez I Hernandez, S Velasco, B ToledopadronAbstract:We report the discovery of a super-Earth orbiting at the inner edge of the habitable zone of the star GJ 625 based on the analysis of the radial-Velocity (RV) time series from the HARPS-N spectrograph, consisting of 151 HARPS-N measurements taken over 3.5 yr. GJ 625 b is a planet with a minimum mass M sin i of 2.82 ± 0.51 M ⊕ with an orbital period of 14.628 ± 0.013 days at a distance of 0.078 AU from its parent star. The host star is the quiet M2 V star GJ 625, located at 6.5 pc from the Sun. We find the presence of a second radial-Velocity Signal in the range 74–85 days that we relate to stellar rotation after analysing the time series of Ca II H&K and H α spectroscopic indicators, the variations of the FWHM of the CCF, and the APT2 photometric light curves. We find no evidence linking the short-period radial-Velocity Signal to any activity proxy.
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characterization of the radial Velocity Signal induced by rotation in late type dwarfs
Monthly Notices of the Royal Astronomical Society, 2017Co-Authors: Suarez A Mascareno, R Rebolo, J Gonzalez I Hernandez, M EspositoAbstract:We investigate the activity induced Signals related to rotation in late type stars (FGKM). We analyse the Ca II H&K, the H alpha and the radial Velocity time-series of 55 stars using the spectra from the HARPS public database and the light-curves provided by the ASAS survey. We search for short term periodic Signals in the time-series of activity indicators as well as in the photometric light-curves. Radial Velocity data sets are then analysed to determine the presence of activity induced Signals. We measure a radial Velocity Signal induced by rotational modulation of stellar surface features in 37 stars, from late F-type to mid M-type stars. We report an empirical relationship, with some degree of spectral type dependency, between the mean level of chromospheric emission measured by the log(Rhk) and the measured radial Velocity semi amplitude. We also report a relationship betweeen the semi amplitude of the chromospheric measured Signal and the semi amplitude of the radial Velocity induced Signal, which strongly depends on the spectral type. We find that for a given strength of chromospheric activity (i.e. a given rotation period) M-type stars tend to induce larger rotation related radial Velocity Signals than G and K-type stars.
Laurence Le Coq - One of the best experts on this subject based on the ideXlab platform.
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local experimental methodology for the study of microparticles resuspension in ventilated duct during fan acceleration
Journal of Aerosol Science, 2020Co-Authors: Felicie Theron, Djihad Debba, Laurence Le CoqAbstract:Abstract The purpose of this study is to develop an experimental methodology with relevant space and time resolutions to track the Velocity properties responsible for the resuspension of microparticles during the acceleration stage of a fan start. Microparticles release is investigated over a time period of several seconds, i.e. at short time. This methodology involves Velocity Signal measurements thanks to Hot Wire Anemometry, and an optical counting method to build resuspension kinetics curves. During the fan acceleration the Velocity evolution is characterized by two stages: a first increase without fluctuations, and then the acceleration with fluctuations. The same behavior is observed whatever the distance to the wall at which Velocity is considered. The resuspension phenomenon seems to be initiated by a threshold turbulent kinetic energy, i.e. by turbulent events powerful enough to release microparticles having the lowest adhesion forces. For the studied particles properties/wall properties/aeraulic conditions, a significant fraction of particles remains on the duct wall at the end of experiments, despite the fact that the remaining fraction is stabilized. This may reveal that the highest energy levels of flow events seen by microparticles were not powerful enough to release particles having the highest adhesion forces.
Darina B Murray - One of the best experts on this subject based on the ideXlab platform.
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jet impingement heat transfer part ii a temporal investigation of heat transfer and local fluid velocities
International Journal of Heat and Mass Transfer, 2007Co-Authors: Tadhg S Odonovan, Darina B MurrayAbstract:Impinging jets are a means of achieving high heat transfer coefficients both locally and on an area averaged basis. The temporal nature of both the fluid flow and heat transfer has been investigated for Reynolds numbers from 10,000 to 30,000 and non-dimensional surface to jet exit distance, H/D, from 0.5 to 8. At the impingement surface simultaneous acquisition of both local heat flux and local Velocity Signal has facilitated a comprehensive analysis of the effect that fluid flow has on the heat transfer. Results are presented in the form of surface heat transfer and fluid Velocity Signal spectra, and coherence and phase difference between the corresponding Velocity and heat flux Signals. It has been shown that the evolution of vortices with distance from the jet exit has an influence on the magnitude of the heat transfer coefficient in the wall jet.
Peter X Liu - One of the best experts on this subject based on the ideXlab platform.
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robust adaptive fuzzy output feedback control system for robot manipulators
IEEE-ASME Transactions on Mechatronics, 2011Co-Authors: Shafiqul Islam, Peter X LiuAbstract:In this paper, we propose a novel hybrid control system for the trajectory tracking control problem of robotic systems. The design combines fuzzy system with robust adaptive control algorithm. The fuzzy system approximates the certainty equivalent-based optimal controller, while a robustifying adaptive control term is used to cope with uncertainties due to the presence of the external disturbance, fuzzy approximation errors, and other modeling errors. Using the Lyapunov method, we first develop a stable hybrid controller by assuming that the system output and its derivatives are available for feedback control design. Then, an output-feedback form of the position-Velocity (state-feedback) controller is proposed, where the unknown Velocity Signal is replaced by the output of a model-free linear estimator. We show that the tracking of the output-feedback design can converge asymptotically to the performance achieved under the state-feedback control design. Finally, the proposed method is evaluated on a robotic system to demonstrate the theoretical development.
