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Littérature scientifique sur le sujet « Radial velocitie »

Auteur : Grafiati

Publié le 9 mars 2023

Mis à jour le 10 mars 2023

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Articles de revues sur le sujet "Radial velocitie"

Walker, G. A. H., J. Amor, S. Yang et B. Campbell. « Precise Radial Velocities and Radial Velocity Standards ». Symposium - International Astronomical Union 111 (1985) : 587–89. http://dx.doi.org/10.1017/s0074180900079547.

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By imposing absorption lines of HF in stellar spectra we can measure changes in r.v. with a precision of ~10m/s from a single spectrum, provided stellar line profiles are not distorted by atmospheric motions. The precision of absolute radial velocities is currently limited to ~100m/s by knowledge of rest wavelengths. Representative results are presented from our three, active PRV programs: velocity variations of δ Scuti stars; a search for unseen companions to late-type stars; and routine observations of certain IAU velocity ‘standards’.

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Deconto-Machado, A., R. A. Riffel, G. S. Ilha, S. B. Rembold, T. Storchi-Bergmann, R. Riffel, J. S. Schimoia et al. « Ionised gas kinematics in MaNGA AGN ». Astronomy & ; Astrophysics 659 (mars 2022) : A131. http://dx.doi.org/10.1051/0004-6361/202140613.

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Context. Feedback from active galactic nuclei (AGNs) in general seems to play an important role in the evolution of galaxies, although the impact of AGN winds on their host galaxies is still unknown in the absence of a detailed analysis. Aims. We aim to analyse the kinematics of a sample of 170 AGN host galaxies as compared to those of a matched control sample of non-active galaxies from the MaNGA survey in order to characterise and estimate the extents of the narrow-line region (NLR) and of the kinematically disturbed region (KDR) by the AGN. Methods. We defined the observed NLR radius (rNLR, o) as the farthest distance from the nucleus within which both [O III]/Hβ and [N II]/Hα ratios fall in the AGN region of the BPT diagram, and the Hα equivalent width was required to be larger than 3.0 Å. The extent of the KDR (rKDR, o) is defined as the distance from the nucleus within which the AGN host galaxies show a more disturbed gas kinematics than the control galaxies. Results. The AGN [O III]λ5007 luminosity ranges from 1039 to 1041 erg s−1, and the kinematics derived from the [O III] line profiles reveal that, on average, the most luminous AGNs (L[O III] > 3.8 × 1040 erg s−1) possess higher residual differences between the gaseous and stellar velocities and velocitie dispersions than their control galaxies in all the radial bins. Spatially resolved NLRs and KDRs were found in 55 and 46 AGN host galaxies, with corrected radii 0.2 < rKDR, c < 2.3 kpc and 0.4 < rNLR, c < 10.1 kpc and a relation between the two given by log rKDR, c = (0.53 ± 0.12) log rNLR, c + (1.07 ± 0.22), respectively. On average, the extension of the KDR corresponds to about 30% of that of the NLR. Assuming that the KDR is due to an AGN outflow, we have estimated ionised gas mass outflow rates that range between 10−5 and ∼1 M⊙ yr−1, and kinetic powers that range from 1034 to 1040 erg s−1. Conclusions. Comparing the power of the AGN ionised outflows with the AGN luminosities, they are always below the 0.05 LAGN model threshold for having an important feedback effect on their respective host galaxies. The mass outflow rates (and power) of our AGN sample correlate with their luminosities, populating the lowest AGN luminosity range of the correlations previously found for more powerful sources.

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Petersburg, Ryan R., J. M. Joel Ong, Lily L. Zhao, Ryan T. Blackman, John M. Brewer, Lars A. Buchhave, Samuel H. C. Cabot et al. « An Extreme-precision Radial-velocity Pipeline : First Radial Velocities from EXPRES ». Astronomical Journal 159, n^o 5 (1 avril 2020) : 187. http://dx.doi.org/10.3847/1538-3881/ab7e31.

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Philip, A. G. Davis, J. Andersen, A. Batten, M. Duflot, D. Hube, M. Mayor et J. Sahade. « 30. Radial Velocities ». Transactions of the International Astronomical Union 19, n^o 1 (1985) : 375–82. http://dx.doi.org/10.1017/s0251107x00006428.

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This report covers the period June 1981 to June 1984. and includes some material from IAU Colloquium No. 88, October, 1984.). The field of radial velocities has undergone a renaissance in the last few years as the new radial velocity machines have come into use. Not only can stars of much fainter magnitudes be reached, but the precision of the measured radial velocity has been increased by orders of magnitude. Instead of speaking of velocities accurate to kilometers per second it is now possible to measure velocities to tens of meters per second. Research programs, involving these new techniques are now underway involving the study of hundreds, and in some cases, thousands of faint stars.

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Sartoretti, P., D. Katz, M. Cropper, P. Panuzzo, G. M. Seabroke, Y. Viala, K. Benson et al. « Gaia Data Release 2 ». Astronomy & ; Astrophysics 616 (août 2018) : A6. http://dx.doi.org/10.1051/0004-6361/201832836.

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Context. The Gaia Data Release 2 (DR2) contains the first release of radial velocities complementing the kinematic data of a sample of about 7 million relatively bright, late-type stars. Aims. This paper provides a detailed description of the Gaia spectroscopic data processing pipeline, and of the approach adopted to derive the radial velocities presented in DR2. Methods. The pipeline must perform four main tasks: (i) clean and reduce the spectra observed with the Radial Velocity Spectrometer (RVS); (ii) calibrate the RVS instrument, including wavelength, straylight, line-spread function, bias non-uniformity, and photometric zeropoint; (iii) extract the radial velocities; and (iv) verify the accuracy and precision of the results. The radial velocity of a star is obtained through a fit of the RVS spectrum relative to an appropriate synthetic template spectrum. An additional task of the spectroscopic pipeline was to provide first-order estimates of the stellar atmospheric parameters required to select such template spectra. We describe the pipeline features and present the detailed calibration algorithms and software solutions we used to produce the radial velocities published in DR2. Results. The spectroscopic processing pipeline produced median radial velocities for Gaia stars with narrow-band near-IR magnitude GRVS ≤ 12 (i.e. brighter than V ~ 13). Stars identified as double-lined spectroscopic binaries were removed from the pipeline, while variable stars, single-lined, and non-detected double-lined spectroscopic binaries were treated as single stars. The scatter in radial velocity among different observations of a same star, also published in Gaia DR2, provides information about radial velocity variability. For the hottest (Teff ≥ 7000 K) and coolest (Teff ≤ 3500 K) stars, the accuracy and precision of the stellar parameter estimates are not sufficient to allow selection of appropriate templates. The radial velocities obtained for these stars were removed from DR2. The pipeline also provides a first-order estimate of the performance obtained. The overall accuracy of radial velocity measurements is around ~200–300 m s−1, and the overall precision is ~1 km s−1; it reaches ~200 m s−1 for the brightest stars.

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Katz, D., P. Sartoretti, M. Cropper, P. Panuzzo, G. M. Seabroke, Y. Viala, K. Benson et al. « Gaia Data Release 2 ». Astronomy & ; Astrophysics 622 (février 2019) : A205. http://dx.doi.org/10.1051/0004-6361/201833273.

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Context. For Gaia DR2, 280 million spectra collected by the Radial Velocity Spectrometer instrument on board Gaia were processed, and median radial velocities were derived for 9.8 million sources brighter than GRVS = 12 mag. Aims. This paper describes the validation and properties of the median radial velocities published in Gaia DR2. Methods. Quality tests and filters were applied to select those of the 9.8 million radial velocities that have the quality to be published in Gaia DR2. The accuracy of the selected sample was assessed with respect to ground-based catalogues. Its precision was estimated using both ground-based catalogues and the distribution of the Gaia radial velocity uncertainties. Results. Gaia DR2 contains median radial velocities for 7 224 631 stars, with Teff in the range [3550, 6900] K, which successfully passed the quality tests. The published median radial velocities provide a full-sky coverage and are complete with respect to the astrometric data to within 77.2% (for G ≤ 12.5 mag). The median radial velocity residuals with respect to the ground-based surveys vary from one catalogue to another, but do not exceed a few 100 m s−1. In addition, the Gaia radial velocities show a positive trend as a function of magnitude, which starts around GRVS ~ 9 mag and reaches about + 500 m s−1 at GRVS = 11.75 mag. The origin of the trend is under investigation, with the aim to correct for it in Gaia DR3. The overall precision, estimated from the median of the Gaia radial velocity uncertainties, is 1.05 km s−1. The radial velocity precision is a function of many parameters, in particular, the magnitude and effective temperature. For bright stars, GRVS ∈ [4, 8] mag, the precision, estimated using the full dataset, is in the range 220–350 m s−1, which is about three to five times more precise than the pre-launch specification of 1 km s−1. At the faint end, GRVS = 11.75 mag, the precisions for Teff = 5000 and 6500 K are 1.4 and 3.7 km s−1, respectively.

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Faizal, Mohd, Md Seri Suzairin, Mohd Al-Hafiz et Vijay Raj Raghavan. « CFD Studies on Velocity Distribution of Air in a Swirling Fluidized Bed ». Advanced Materials Research 468-471 (février 2012) : 25–29. http://dx.doi.org/10.4028/www.scientific.net/amr.468-471.25.

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This paper presents computational fluid dynamics (CFD) studies to characterize air velocity distribution for various bed configurations in a swirling fluidized bed (SFB). Unlike conventional fluidized beds, a SFB provides radial mixing which is desirable is fluidization. Three velocities components were observed, the tangential velocity, radial velocity and axial velocity. These velocities were created as a result of using annular blade type distributor which mimics the turbine blades. In actual industrial applications, the axial velocity will create fluidization while the tangential velocity provides swirling effect. The presence of radial velocity can be explained as a consequence of centrifugal force generated by the swirling gas. Understanding these velocity distributions will enable optimization of the annular blade distributor design towards a high efficient fluidized bed system.

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Griffin, R. F. « Photoelectric radial velocities, Paper XIV. Variation of the radial velocity of ε Cygni ». Monthly Notices of the Royal Astronomical Society 267, n^o 1 (mars 1994) : 69–76. http://dx.doi.org/10.1093/mnras/267.1.69.

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Lv, Xiao Shi, Guang Yong Wang et Jia Qi Guo. « The Study of the Influence of the Incident Angle, Frequency and Diameter on Blasting Vibration Velocity of the Underground Chamber ». Applied Mechanics and Materials 90-93 (septembre 2011) : 1555–65. http://dx.doi.org/10.4028/www.scientific.net/amm.90-93.1555.

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Based on model tests, the wave function expansion method was used to study scattering on the interaction of explosive stress waves and the underground chamber, and analyze the influence of the incident angle, frequency and diameter on blasting vibration velocity of underground chamber. It is obtained that when the cavern was under the plane waves of the vault, the radial vibration velocity of the vault is the largest among the four measured data, and it is the most intense vibrating place. When the incidence direction offsets from the vault to the horizontal direction on the left, the radial velocity facing burst are all larger than the radial velocity back of the burst. When the incident direction is on the dome, the tangential vibration velocity will increase first and then decrease from the vault to the side wall. When the incident direction is at the haunch, the tangential vibration velocity in the corner should be noticed. With increasing of the frequency, the radial vibration velocity and tangential vibration velocity increase accordingly. At the forward part of the burst, the larger the chamber diameter is, the bigger the radial and tangential velocities are. At the back side of the burst, the bigger the chamber diameter is, the smaller the radial and tangential vibration velocities are.

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Xiao, Qingnong, Ying-Hwa Kuo, Juanzhen Sun, Wen-Chau Lee, Eunha Lim, Yong-Run Guo et Dale M. Barker. « Assimilation of Doppler Radar Observations with a Regional 3DVAR System : Impact of Doppler Velocities on Forecasts of a Heavy Rainfall Case ». Journal of Applied Meteorology 44, n^o 6 (1 juin 2005) : 768–88. http://dx.doi.org/10.1175/jam2248.1.

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Abstract In this paper, the impact of Doppler radar radial velocity on the prediction of a heavy rainfall event is examined. The three-dimensional variational data assimilation (3DVAR) system for use with the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) is further developed to enable the assimilation of radial velocity observations. Doppler velocities from the Korean Jindo radar are assimilated into MM5 using the 3DVAR system for a heavy rainfall case that occurred on 10 June 2002. The results show that the assimilation of Doppler velocities has a positive impact on the short-range prediction of heavy rainfall. The dynamic balance between atmospheric wind and thermodynamic fields, based on the Richardson equation, is introduced to the 3DVAR system. Vertical velocity (w) increments are included in the 3DVAR system to enable the assimilation of the vertical velocity component of the Doppler radial velocity observation. The forecast of the hydrometeor variables of cloud water (qc) and rainwater (qr) is used in the 3DVAR background fields. The observation operator for Doppler radial velocity is developed and implemented within the 3DVAR system. A series of experiments, assimilating the Korean Jindo radar data for the 10 June 2002 heavy rainfall case, indicates that the scheme for Doppler velocity assimilation is stable and robust in a cycling mode making use of high-frequency radar data. The 3DVAR with assimilation of Doppler radial velocities is shown to improve the prediction of the rainband movement and intensity change. As a result, an improved skill for the short-range heavy rainfall forecast is obtained. The forecasts of other quantities, for example, winds, are also improved. Continuous assimilation with 3-h update cycles is important in producing an improved heavy rainfall forecast. Assimilation of Doppler radar radial velocities using the 3DVAR background fields from a cycling procedure produces skillful rainfall forecasts when verified against observations.

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Plus de sources

Thèses sur le sujet "Radial velocitie"

FRUSTAGLI, GIUSEPPE. « Exoplanets Characterization : from Ultra-short Period Planets to Ultra-hot Jupiters Atmospheres ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2021. http://hdl.handle.net/10281/311363.

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La scoperta di pianeti che orbitano intorno ad altre stelle è uno degli eventi più importanti nell'astrofisica galattica degli ultimi due decenni. Dalla scoperta del primo esopianeta nel 1995, il numero di esopianeti scoperti è cresciuto sempre più in fretta e attualmente conosciamo più di 4,000 pianeti, molto diversi per dimensioni e distanza dalla stella ospite e anche in fattori come temperatura, massa, densità. La diversità degli esopianeti è un fattore chiave per comprendere la formazione dei sistemi planetari e in particolare la formazione del Sistema Solare e del nostro pianeta, la Terra. Questo è il motivo per cui la scienza osservativa degli esopianeti si sta concentrando su due diversi obiettivi: i) la caratterizzazione degli esopianeti, nel tentativo di determinare il raggio, la massa, la densità e la composizione degli oggetti osservati e ii) la caratterizzazione delle loro atmosfere, stabilendo gli elementi che l'atmosfera di un pianeta può supportare e i meccanismi che guidano i processi atmosferici. Caratterizzazione degli Esopianeti La fotometria, con il metodo dei transiti si è rivelato senza dubbio il metodo di scoperta di esopianeti con il maggior successo. La forza di questo metodo è il numero di parametri che possono essere ottenuti osservando il transito dei pianeti, soprattutto in combinazione con le osservazioni di velocità radiale (VR). In questo contesto, uno dei gruppi più prolifici è il Consorzio GTO di HARPS-N, che sfrutta l'alta risoluzione e l'estrema stabilità dello spettrografo HARPS-N, installato al Telescopio Nazionale Galileo, per caratterizzare e scoprire esopianeti combinando il metodo dei transiti e quello delle velocità radiali. Come collaboratore di questo gruppo, ho studiato un pianeta candidato scoperto dalla Campagna 16 della missione K2, HD 80653 b, una super-Terra che transita davanti alla sua stella con un periodo orbitale molto breve, e ho usato le VR HARPS-N per caratterizzarlo, ottenendo la sua massa e definendone la densità. Il pianeta appartiene ad una particolare classe di esopianeti: i pianeti a periodo ultra-corto, oggetti che orbitano intorno alle loro stelle con periodi estremamente brevi, più piccoli di due raggi terrestri e con composizioni simili a quella terrestre. Caratterizzazione di Atmosfere I gioviani ultra-caldi sono laboratori eccellenti per lo studio delle atmosfere esoplanetarie. Il sodio, per la sua grande sezione d'urto e per il fatto che le sue righe spettrali principali si trovano nel range spettrale della maggior parte degli spettrografi, è l'elemento più studiato, ma lo studio di nuove righe spettrali è cominciato. Righe del ferro, del titanio, del magnesio, ma anche tracce di cromo, scandio e ittrio sono state trovate negli spettri di trasmissione ad alta risoluzione dei pianeti più caldi. I due gioviani ultra-caldi KELT-9 b e KELT-20 b sono stati osservati dal programma atmosfere del gruppo italiano Global architecture of Planetary Systems (GAPS). Come membro del gruppo ho potuto esplorare più in dettaglio il metodo della spettroscopia in transito, creando due diverse routine per la caratterizzazione delle atmosfere. Il primo metodo segue approcci già utilizzati in precedenza, ma è in grado di rilevare righe spettrali deboli come quelle del magnesio, sommandole nello spazio delle velocità. Usando questo approccio ho analizzato gli spettri ad alta risoluzione di KELT-9 b e KELT-20 b e ho ottenuto i loro spettri di trasmissione, rilevando un assorbimento significativo per Na, H, Fe e Mg I. Il secondo metodo estrae gli spettri di trasmissione ad alta risoluzione e li cross-correla con modelli teorici di spettri di trasmissione. Analizzando gli spettri di KELT-20 b e utilizzando la cross-correlazione ho potuto confermare la presenza di Fe I, Fe II e Na I, trovate da analisi precedenti di altri gruppi di ricerca.
The discovery of planets orbiting around stars other than the Sun is by far the most relevant event in the galactic astrophysics of the last two decades. Since the discovery of the first exoplanet in 1995, the number of exoplanets discovered grew fast and we currently know more than 4,000 exoplanets, very diverse in dimension and distance from parent stars and also in factors as temperature, mass, density. The diversity of exoplanets is a key factor to understand more about the formation of planetary systems and in particular the formation of the Solar System and our planet, the Earth. This is the reason why observational exoplanetary science is currently focusing on two different fields: i) the characterization of exoplanets, trying to determine the radius, the mass, the density and the bulk composition of the objects observed, and ii) the characterization of their atmospheres, establishing the elements that the atmosphere of a planet supports and the mechanisms that drive the atmospheric processes. Characterization of Exoplanets Photometry with the transit method has arguably been the most successful exoplanet discovery method to date. The method’s strength is the rich set of parameters that can be obtained from transiting planets, in particular in combination with RV observations. In this framework, one of the most prolific groups is the HARPS-N Guaranteed Time Observations (GTO) Consortium, that makes use of the high resolution (R = 115,000) and extreme stability of the HARPS-N spectrograph, installed on the Telescopio Nazionale Galileo (TNG), to characterize and discover exoplanets by combining transits and RV methods. As a collaborator of this group, I studied a candidate planet discovered by K2 Campaign 16, HD 80653 b, a super-Earth planet transiting the star on a short period orbit, and used HARPS-N RV data to characterize it, finding its mass and defining its bulk density. It belongs to a peculiar class of exoplanets: the Ultra-Short Period (USP) planets, objects that orbit their stars with extremely short periods, smaller than about 2 Earth Radii and compositions similar to that of the Earth. Characterization of Atmospheres Ultra-hot Jupiters are excellent laboratories for the study of exoplanetary atmospheres. Sodium, due to its large cross-section and to the fact it is in the wavelength range of most optical spectrographs, is the most studied element, but new interesting features begin to be analyzed. Lines of iron, titanium, magnesium, but also chromium, scandium and yttrium have been found in the high resolution transmission spectra of the hottest planets. The two ultra-hot Jupiters KELT-9 b and KELT-20 b were observed in the framework of the Global architecture of Planetary Systems (GAPS) Atmosphere program. I explored more in detail the transit spectroscopy method, creating two different routines for atmosphere characterization. The first routine follows previous approaches for high-resolution spectroscopy, but is able to detect weak spectral lines such as those of magnesium, by co-adding the lines in the velocities space. Using this procedure, I analyzed the high-resolution spectra of KELT-9 b and KELT-20 b, obtaining their transmission spectra and detecting significant absorption for Na, H, Fe and Mg I. The second routine extracts the high-resolution transmission spectra of exoplanets and cross-correlates them with theoretical transmission spectra models. I analyzed the high-resolution spectra of KELT-20 b and with the cross-correlation technique I confirmed previous detections of Fe I, Fe II, and Na I.

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Ortiz, Mauricio, Sabine Reffert, Trifon Trifonov, Andreas Quirrenbach, David S. Mitchell, Grzegorz Nowak, Esther Buenzli et al. « Precise radial velocities of giant stars ». EDP SCIENCES S A, 2016. http://hdl.handle.net/10150/622444.

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Context. For over 12 yr, we have carried out a precise radial velocity (RV) survey of a sample of 373 G- and K-giant stars using the Hamilton Echelle Spectrograph at the Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims. We aim at detecting and characterizing substellar and stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods. We obtained high-precision RV measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. To distinguish between RV variations that are due to non-radial pulsation or stellar spots, we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to characterize the system in more detail, we obtained high-resolution images with LMIRCam at the Large Binocular Telescope. Results. We report the probable discovery of a giant planet with a mass of m(p) sin i = 6.92(-0.24)(+0.18) M-Jup orbiting at a(p) = 1.0860(-0.0007)(+0.0006) aufrom the giant star HD 59686 A. In addition to the planetary signal, we discovered an eccentric (e(B) = 0.729(-0.003)(+0.004)) binary companionwith a mass of m(B) sin i = 0.5296(-0.0008)(+0.0011) M-circle dot orbiting at a close separation from the giant primary with a semi-major axis of a(B) = 13.56(-0.14)(+0.18) au. Conclusions. The existence of the planet HD 59686 Ab in a tight eccentric binary system severely challenges standard giant planet formation theories and requires substantial improvements to such theories in tight binaries. Otherwise, alternative planet formation scenarios such as second-generation planets or dynamical interactions in an early phase of the system's lifetime need to be seriously considered to better understand the origin of this enigmatic planet.

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Carleo, Ilaria. « High precision radial velocities with giano spectra ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7388/.

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Radial velocities measured from near-infrared (NIR) spectra are a potential tool to search for extrasolar planets around cool stars. High resolution infrared spectrographs now available reach the high precision of visible instruments, with a constant improvement over time. GIANO is an infrared echelle spectrograph and it is a powerful tool to provide high resolution spectra for accurate radial velocity measurements of exo-planets and for chemical and dynamical studies of stellar or extragalactic objects. No other IR instruments have the GIANO's capability to cover the entire NIR wavelength range. In this work we develop an ensemble of IDL procedures to measure high precision radial velocities on a few GIANO spectra acquired during the commissioning run, using the telluric lines as wevelength reference. In Section 1.1 various exoplanet search methods are described. They exploit different properties of the planetary system. In Section 1.2 we describe the exoplanet population discovered trough the different methods. In Section 1.3 we explain motivations for NIR radial velocities and the challenges related the main issue that has limited the pursuit of high-precision NIR radial velocity, that is, the lack of a suitable calibration method. We briefly describe calibration methods in the visible and the solutions for IR calibration, for instance, the use of telluric lines. The latter has advantages and problems, described in detail. In this work we use telluric lines as wavelength reference. In Section 1.4 the Cross Correlation Function (CCF) method is described. This method is widely used to measure the radial velocities.In Section 1.5 we describe GIANO and its main science targets. In Chapter 2 observational data obtained with GIANO spectrograph are presented and the choice criteria are reported. In Chapter 3 we describe the detail of the analysis and examine in depth the flow chart reported in Section 3.1. In Chapter 4 we give the radial velocities measured with our IDL procedure for all available targets. We obtain an rms scatter in radial velocities of about 7 m/s. Finally, we conclude that GIANO can be used to measure radial velocities of late type stars with an accuracy close to or better than 10 m/s, using telluric lines as wevelength reference. In 2014 September GIANO is being operative at TNG for Science Verification and more observational data will allow to further refine this analysis.

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Seabroke, George Michael. « Probing the Milky Way galaxy through thick and thin (discs and halo) with the CORrelation RAdial VELocities (CORAVEL) and the RAdial velocity experiment (RAVE) surveys ». Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612308.

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Lindgren, Harri. « Radial velocity measurements of late-type stars ». Lund : Institutionen för astronomi, Lunds universitet, 1994. http://catalog.hathitrust.org/api/volumes/oclc/40300933.html.

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May, Brian Harold. « A survey of radial velocities in the zodiacal dust cloud ». Thesis, New York : Bristol [England] : Springer ; In association with Canopus Publishing, 2008. http://www.loc.gov/catdir/toc/fy1002/2008300421.html.

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Sperauskas, J., S. Bartašiūtė, R. P. Boyle, V. Deveikis, S. Raudeliūnas et A. R. Upgren. « Radial velocities of K–M dwarfs and local stellar kinematics ». EDP SCIENCES S A, 2016. http://hdl.handle.net/10150/622691.

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Aims. The goal of this paper is to present complete radial-velocity data for the spectroscopically selected McCormick sample of nearby K-M dwarfs and, based on these and supplementary data, to determine the space-velocity distributions of late-type stars in the solar neighborhood. Methods. We analyzed nearly 3300 measurements of radial velocities for 1049 K-M dwarfs, that we obtained during the past decade with a CORAVEL-type instrument, with a primary emphasis on detecting and eliminating from kinematic calculations the spectroscopic binaries and binary candidates. Combining radial-velocity data with HIPPARCOS/Tycho-2 astrometry we calculated the space-velocity components and parameters of the galactic orbits in a three-component model potential for the stars in the sample, that we use for kinematical analysis and for the identification of possible candidate members of nearby stellar kinematic groups. Results. We present the catalog of our observations of radial velocities for 959 stars which are not suspected of velocity variability, along with the catalog of U, V, W velocities and Galactic orbital parameters for a total of 1088 K-M stars which are used in the present kinematic analysis. Of these, 146 stars were identified as possible candidate members of the known nearby kinematic groups and suspected subgroups. The distributions of space-velocity components, orbital eccentricities, and maximum distances from the Galactic plane are consistent with the presence of young, intermediate-age and old populations of the thin disk and a small fraction (similar to 3%) of stars with the thick disk kinematics. The kinematic structure gives evidence that the bulk of K-M type stars in the immediate solar vicinity represents a dynamically relaxed stellar population. The star MCC 869 is found to be on a retrograde Galactic orbit (V = -262 km s(-1)) of low inclination (4 degrees) and can be a member of stellar stream of some dissolved structure. The Sun's velocity with respect to the Local Standard of Rest, derived from the distributions of space-velocity components, is (U-circle dot, V-circle dot, W-circle dot) = (9.0 +/- 1.4, 13.1 +/- 0.6, 7.2 +/- 0.8) km s(-1). The radial solar motion derived via the Stromberg's relation, V-circle dot = 14.2 +/- 0.8 km s(-1), agrees within the errors with the value obtained directly from the V distribution of stars on nearly circular orbits.

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May, Brian Harold. « A survey of radial velocities in the zodiacal dust cloud / ». London : Imperial college of science, technology and medecine, 2007. http://catalogue.bnf.fr/ark:/12148/cb41363194j.

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Baldwin, Dan, Andrew Szentgyorgyi, Stuart Barnes, Jacob Bean, Sagi Ben-Ami, Patricia Brennan, Jamie Budynkiewicz et al. « Advanced structural design for precision radial velocity instruments ». SPIE-INT SOC OPTICAL ENGINEERING, 2016. http://hdl.handle.net/10150/622418.

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The GMT-Consortium Large Earth Finder (G-CLEF) is an echelle spectrograph with precision radial velocity (PRV) capability that will be a first light instrument for the Giant Magellan Telescope (GMT). G-CLEF has a PRV precision goal of 40 cm/sec (10 cm/s for multiple measurements) to enable detection of Earth-like exoplanets in the habitable zones of sun-like stars'. This precision is a primary driver of G-CLEF's structural design. Extreme stability is necessary to minimize image motions at the CCD detectors. Minute changes in temperature, pressure, and acceleration environments cause structural deformations, inducing image motions which degrade PRV precision. The instrument's structural design will ensure that the PRV goal is achieved under the environments G-CLEF will be subjected to as installed on the GMT azimuth platform, including: Millikelvin (0.001 K) thermal soaks and gradients 10 millibar changes in ambient pressure Changes in acceleration due to instrument tip/tilt and telescope slewing Carbon fiber/cyanate composite was selected for the optical bench structure in order to meet performance goals. Low coefficient of thermal expansion (C 1E) and high stiffness-to-weight are key features of the composite optical bench design. Manufacturability and serviceability of the instrument are also drivers of the design. In this paper, we discuss analyses leading to technical choices made to minimize G-CLEF's sensitivity to changing environments. Finite element analysis (FEA) and image motion sensitivity studies were conducted to determine PRV performance under operational environments. We discuss the design of the optical bench structure to optimize stiffness to -weight and minimize deformations due to inertial and pressure effects. We also discuss quasi-kinematic mounting of optical elements and assemblies, and optimization of these to ensure minimal image motion under thermal, pressure, and inertial loads expected during PRV observations.

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Ramm, David John. « A spectroscopic study of detached binary systems using precise radial velocities ». Thesis, University of Canterbury. Physics and Astronomy, 2004. http://hdl.handle.net/10092/1525.

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Spectroscopic orbital elements and/or related parameters have been determined for eight binary systems, using radial-velocity measurements that have a typical precision of about 15 ms⁻¹. The orbital periods of these systems range from about 10 days to 26 years, with a median of about 6 years. Orbital solutions were determined for the seven systems with shorter periods. The measurement of the mass ratio of the longest-period system, HD217166, demonstrates that this important astrophysical quantity can be estimated in a model-free manner with less than 10% of the orbital cycle observed spectroscopically.\\ Single-lined orbital solutions have been derived for five of the binaries. Two of these systems are astrometric binaries: β Ret and ν Oct. The other SB1 systems were 94 Aqr A, θ Ant, and the 10-day system, HD159656. The preliminary spectroscopic solution for θ Ant (P~18 years), is the first one derived for this system. The improvement to the precision achieved for the elements of the other four systems was typically between 1--2 orders of magnitude. The very high precision with which the spectroscopic solution for HD159656 has been measured should allow an investigation into possible apsidal motion in the near future. In addition to the variable radial velocity owing to its orbital motion, the K-giant, ν Oct, has been found to have an additional long-term irregular periodicity, attributed, for the time being, to the rotation of a large surface feature.\\ Double-lined solutions were obtained for HD206804 (K7V+K7V), which previously had two competing astrometric solutions but no spectroscopic solution, and a newly discovered seventh-magnitude system, HD181958 (F6V+F7V). This latter system has the distinction of having components and orbital characteristics whose study should be possible with present ground-based interferometers. All eight of the binary systems have had their mass ratio and the masses of their components estimated.\\ The following comments summarize the motivation for getting these results, and the manner in which the research was carried out. \\ The majority of stars exist in binary systems rather than singly as does the Sun. These systems provide astronomers with the most reliable and proven means to determine many of the fundamental properties of stars. One of these properties is the stellar mass, which is regarded as being the most important of all, since most other stellar characteristics are very sensitive to the mass. Therefore, empirical masses, combined with measurements of other stellar properties, such as radii and luminosities, are an excellent test for competing models of stellar structure and evolution.\\ Binary stars also provide opportunities to observe and investigate many extraordinary astrophysical processes that do not occur in isolated stars. These processes often arise as a result of direct and indirect interactions between the components, when they are sufficiently close to each other. Some of the interactions are relatively passive, such as the circularization of the mutual orbits, whilst others result from much more active processes, such as mass exchange leading to intense radiation emissions. \\ A complete understanding of a binary system's orbital characteristics, as well as the measurement of the all-important stellar masses, is almost always only achieved after the binary system has been studied using two or more complementary observing techniques. Two of the suitable techniques are astrometry and spectroscopy. In favourable circumstances, astrometry can deduce the angular dimensions of the orbit, the total mass of the system, and sometimes, its distance from us. Spectroscopy, on the other hand, can determine the linear scale of the orbit and the ratio of the stellar masses, based on the changing radial velocities of both stars. When a resolved astrometric orbital solution is also available, the velocities of both stars can allow the binary system's parallax to be determined, and the velocities of one star can provide a measure of the system mass ratio.\\ Unfortunately, relatively few binary systems are suited to these complementary studies. Underlying this difficulty are the facts that, typically, astrometrically-determined orbits favour those with periods of years or decades, whereas spectroscopic orbital solutions are more often measured for systems with periods of days to months. With the development of high-resolution astrometric and spectroscopic techniques in recent years, it is hoped that many more binary systems will be amenable to these complementary strategies.\\ Several months after this thesis began, a high-resolution spectrograph, HERCULES, commenced operations at the Mt John University Observatory, to be used in conjuction with the 1-metre McLellan telescope. For late-type stars, the anticipated velocity precision was ≲10 ms⁻¹. The primary goals of this thesis were: 1.~to assess the performance of HERCULES and the related reduction software that subsequently followed, 2.~to carry out an observational programme of 20 or so binary systems, and 3.~to determine the orbital and stellar parameters which characterize some of these systems. The particular focus was on those binaries that have resolved or unresolved astrometric orbital solutions, which therefore may be suited to complementary investigations.\\ HERCULES was used to acquire spectra of the programme stars, usually every few weeks, over a timespan of about three years. High-resolution spectra were acquired for the purpose of measuring precise radial velocities of the stars. When possible, orbital solutions were derived from these velocities, using the method of differential corrections.

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Livres sur le sujet "Radial velocitie"

Davis, Philip A. G., et Latham David W, dir. Stellar radial velocities. Schenectady, N.Y : L. Davis Press, 1985.

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Barbier-Brossat, M. Catalogue bibliographique de vitesses radiales stellaires, 1970-1990 = : Bibliographic catalogue of stellar radial velocities, 1970-1990. Marseille, France : Observatoire de Marseille, 1995.

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Haywood, Raphaëlle D. Radial-velocity Searches for Planets Around Active Stars. Cham : Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-41273-3.

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May, Brian Harold. A Survey of Radial Velocities in the Zodiacal Dust Cloud. New York, NY : Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-77706-1.

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May, Brian Harold. A survey of radial velocities in the zodiacal dust cloud. New York : Springer, 2008.

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A survey of radial velocities in the zodiacal dust cloud. New York : Springer, 2008.

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Cummings, I. N. High precision radial-velocity measurements of late-type evolved stars. [Canterbury] : University of Canterbury, 1998.

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Jones, Andrew Richard. An optical resonance spectrometer for measuring solar and stellar radial velocities to high precision. Birmingham : University of Birmingham, 1986.

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United States. National Aeronautics and Space Administration., dir. Planetary systems around neutron stars : A summary of research, March 1, 1993 through September 30, 1997 : grant no.--NAG W-3405. [Washington, DC : National Aeronautics and Space Administration, 1997.

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Lottman, B. Evaluation of the MV (CAPON) coherent Doppler lidar velocity estimator. MSFC, Ala : National Aeronautics and Space Administration, Marshall Space Flight Center, 1997.

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Chapitres de livres sur le sujet "Radial velocitie"

Walker, G. A. H., J. Amor, S. Yang et B. Campbell. « Precise Radial Velocities and Radial Velocity Standards ». Dans Calibration of Fundamental Stellar Quantities, 587–89. Dordrecht : Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5456-4_81.

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Andersen, Johannes, D. W. Latham, A. Florsch, E. Maurice, M. Mayor, R. D. McClure et A. G. D. Philip. « Radial Velocities ». Dans Reports on Astronomy, 355–62. Dordrecht : Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-2981-4_22.

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Fairall, A. P., K. C. Freeman, D. W. Latham, B. W. Carney, J. C. Mermilliod, G. Burki, R. P. Stefanik et C. D. Scarfe. « Radial Velocities ». Dans Reports on Astronomy, 319–24. Dordrecht : Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1100-3_22.

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West, Richard M. « Radial Velocities ». Dans Reports on Astronomy, 375–82. Dordrecht : Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5392-5_22.

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Scarfe, C. D., J. B. Hearnshaw, W. D. Cochran, L. N. da Costa, A. P. Fairall, F. C. Fekel, K. C. Freeman et al. « Commission 30. Radial Velocities (Vitesses Radiales) ». Dans Reports on Astronomy, 521–26. Dordrecht : Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5762-9_39.

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Latham, David W. « Radial Velocity ». Dans Encyclopedia of Astrobiology, 1399–400. Berlin, Heidelberg : Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-11274-4_1331.

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Latham, David W. « Radial Velocity ». Dans Encyclopedia of Astrobiology, 2106. Berlin, Heidelberg : Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44185-5_1331.

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Latham, David W. « Radial Velocity ». Dans Encyclopedia of Astrobiology, 1. Berlin, Heidelberg : Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-27833-4_1331-3.

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Latham, David W., et Nader Haghighipour. « Radial-Velocity Planets ». Dans Encyclopedia of Astrobiology, 2107–13. Berlin, Heidelberg : Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44185-5_1839.

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Latham, David W. « Radial-Velocity Planets ». Dans Encyclopedia of Astrobiology, 1400–1404. Berlin, Heidelberg : Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-11274-4_1839.

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Actes de conférences sur le sujet "Radial velocitie"

Brizuela, Edward A. « A Contribution to the Study of Exit Flow Angle in Radial Turbines ». Dans ASME 1991 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1991. http://dx.doi.org/10.1115/91-gt-010.

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The emergence and evolution of relative whirling motions in the exducer region of an Inward Flow Radial Turbine is discussed. Existing models of relative motion are reviewed and expanded by consideration of the effect of centrifugal forces differences arising from velocity gradients. It is shown that the often observed phenomenon of outlet overturn/underturn is inherent to the use of straight-helix exducers. Explicit mathematical relationships between exit velocities and radius are not available. If, however, such relationships could be considered linear, it is shown that two new reference radii may be identified such that the net outlet properties can be measured or computed at these locations as lump parameters. These radii are different from the often used hydraulic radius. The new models and reference radii are verified using published experimental data.

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Jones, Hugh R. A., John Rayner, Larry Ramsey, David Henry, Bill Dent, David Montgomery, Andy Vick et al. « Precision radial velocity spectrograph ». Dans SPIE Astronomical Telescopes + Instrumentation, sous la direction de Ian S. McLean et Mark M. Casali. SPIE, 2008. http://dx.doi.org/10.1117/12.789807.

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Schwarz, C., M. M. Montgomery, E. L. Martin, Klaus Werner et T. Rauch. « Radial Velocities of Accreting White Dwarfs ». Dans 17TH EUROPEAN WHITE DWARF WORKSHOP. AIP, 2010. http://dx.doi.org/10.1063/1.3527842.

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Geyer, Edward H., et Thilo Bauer. « Reversion radial velocity (REVRAVEL) : a new principle for a stellar radial velocity spectrometer ». Dans SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation, sous la direction de Jinxue Wang et Paul B. Hays. SPIE, 1994. http://dx.doi.org/10.1117/12.187597.

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Kilic, Muhsin, Xiaopeng Gan et J. Michael Owen. « Turbulent Flow Between Two Discs Contra-Rotating at Differential Speeds ». Dans ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1994. http://dx.doi.org/10.1115/94-gt-054.

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This paper describes a combined computational and experimental study of the turbulent flow between two contra-rotating discs for −1 ≤ Γ ≤ 0 and Reφ ≃ 1.2 × 106, where Γ is the ratio of the speed of the slower disc to that of the faster one and Reφ is the rotational Reynolds number. The computations were conducted using an axisymmetric elliptic multigrid solver and a low-Reynolds-number k-ε turbulence model. Velocity measurements were made using LDA at nondimensional radius ratios of 0.6 ≤ x ≤ 0.85. For Γ = 0, the rotor-stator case, Batchelor-type flow occurs: there is radial outflow and inflow in boundary layers on the rotor and stator, respectively, between which is an inviscid rotating core of fluid where the radial component of velocity is zero and there is an axial flow from stator to rotor. For Γ = −1, anti-symmetrical contra-rotating discs, Stewartson-type flow occurs with radial outflow in boundary layers on both discs and inflow in the viscid nonrotating core. At intermediate values of Γ, two cells separated by a streamline that stagnates on the slower disc are formed: Batchelor-type flow and Stewartson-type flow occur radially outward and inward, respectively, of the stagnation streamline. Agreement between the computed and measured velocities is mainly very good, and no evidence was found of nonaxisymmetric or unsteady flow.

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Gibson, Rose, Gautam Vasisht, Rebecca Oppenheimer, Chalres Beichman, Stephanie Leifer, Jason Fucik, Christopher Paine, Mahmood Bagheri et Bryson Cale. « Achieving 1 m/s instrument radial velocity stability with the Palomar Radial Velocity Instrument ». Dans Ground-based and Airborne Instrumentation for Astronomy IX, sous la direction de Christopher J. Evans, Julia J. Bryant et Kentaro Motohara. SPIE, 2022. http://dx.doi.org/10.1117/12.2644698.

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de Paolo, Tony, Eric Terrill et Anthony Kirincich. « Improving SeaSonde radial velocity accuracy and variance using radial metrics ». Dans OCEANS 2015 - Genova. IEEE, 2015. http://dx.doi.org/10.1109/oceans-genova.2015.7271360.

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Seifahrt, Andreas, Jacob L. Bean, Tomonori Usuda, Motohide Tamura et Miki Ishii. « Measuring Radial Velocities in the Near-infrared ». Dans EXOPLANETS AND DISKS : THEIR FORMATION AND DIVERSITY : Proceedings of the International Conference. AIP, 2009. http://dx.doi.org/10.1063/1.3215884.

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Betters, Christopher H., Alex Murray, Joss Bland-Hawthorn et Sergio G. Leon-Saval. « Precision radial velocities with inexpensive compact spectrographs ». Dans SPIE Astronomical Telescopes + Instrumentation, sous la direction de Christopher J. Evans, Luc Simard et Hideki Takami. SPIE, 2016. http://dx.doi.org/10.1117/12.2232126.

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Pease, Leonard F., Judith Ann Bamberger et Michael J. Minette. « Jet Erosion of Particle Beds : Projecting Critical Suspension Velocities From Effective Clearing / Cleaning Radii ». Dans ASME 2022 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/fedsm2022-85965.

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Abstract Here we explore the relationship between effective cleaning/clearing radii, ECR, and critical suspension velocities, Ucs. Although one set of physics controls both the radial extent of erosion (i.e., the ECR) and the velocity needed to erode from the center of jet impingement to any given location (i.e., Ucs, typically defined from nozzle center to the vessel center), the relationship between these two remains unexplored quantitatively for nominally non-cohesive solids. Here we advance the model of Kuhn, et al., (PNNL-22816, 2013) as described by Pease, et al. (FEDSM2017-69444, 2017) to evaluate the relationship between the effective clearing/cleaning radius and the nozzle velocity on flat surfaces including flat bottomed vessels. Two governing dimensionless groups are identified. We present both a closed form analytical but transcendental solution and a non-iterative approximation modeled after the Serghides approximation of Colebrook’s nonlinear equation for both ECR versus nozzle velocity and Ucs. Comparison of the model to data from flume testing on a flat surface finds reasonable agreement.

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Rapports d'organisations sur le sujet "Radial velocitie"

Richards, John Alfred. GMTI radar minimum detectable velocity. Office of Scientific and Technical Information (OSTI), avril 2011. http://dx.doi.org/10.2172/1011708.

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DOERRY, ARMIN W., BRIAN P. MILESHOSKY et DOUGLAS L. BICKEL. Tangential Velocity Measurement Using Interferometric MTI Radar. Office of Scientific and Technical Information (OSTI), novembre 2002. http://dx.doi.org/10.2172/805861.

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Larsen, M. F. Radar Interferometric Studies of Jetstream Vertical Velocities and Precipitating Regions. Fort Belvoir, VA : Defense Technical Information Center, mai 2000. http://dx.doi.org/10.21236/ada380321.

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Doerry, Armin Walter, Volker Horndt, Douglas Lloyd Bickel et Richard M. Naething. Estimating Radar Velocity using Direction of Arrival Measurements. Office of Scientific and Technical Information (OSTI), septembre 2014. http://dx.doi.org/10.2172/1323271.

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Ray, Laura, Madeleine Jordan, Steven Arcone, Lynn Kaluzienski, Benjamin Walker, Peter Ortquist Koons, James Lever et Gordon Hamilton. Velocity field in the McMurdo shear zone from annual ground penetrating radar imaging and crevasse matching. Engineer Research and Development Center (U.S.), décembre 2021. http://dx.doi.org/10.21079/11681/42623.

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The McMurdo shear zone (MSZ) is strip of heavily crevassed ice oriented in the south-north direction and moving northward. Previous airborne surveys revealed a chaotic crevasse structure superimposed on a set of expected crevasse orientations at 45 degrees to the south-north flow (due to shear stress mechanisms). The dynamics that produced this chaotic structure are poorly understood. Our purpose is to present our field methodology and provide field data that will enable validation of models of the MSZ evolution, and here, we present a method for deriving a local velocity field from ground penetrating radar (GPR) data towards that end. Maps of near-surface crevasses were derived from two annual GPR surveys of a 28 km² region of the MSZ using Eulerian sampling. Our robot-towed and GPS navigated GPR enabled a dense survey grid, with transects of the shear zone at 50 m spacing. Each survey comprised multiple crossings of long (> 1 km) crevasses that appear in echelon on the western and eastern boundaries of the shear zone, as well as two or more crossings of shorter crevasses in the more chaotic zone between the western and eastern boundaries. From these maps, we derived a local velocity field based on the year-to-year movement of the same crevasses. Our velocity field varies significantly from fields previously established using remote sensing and provides more detail than one concurrently derived from a 29-station GPS network. Rather than a simple velocity gradient expected for crevasses oriented approximately 45 degrees to flow direction, we find constant velocity contours oriented diagonally across the shear zone with a wavy fine structure. Although our survey is based on near-surface crevasses, similar crevassing found in marine ice at 160 m depth leads us to conclude that this surface velocity field may hold through the body of meteoric and marine ice. Our success with robot-towed GPR with GPS navigation suggests we may greatly increase our survey areas.

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Mahajan, S. M., G. Z. Machabeli et A. D. Rogava. Escaping radio emission from pulsars : Possible role of velocity shear. Office of Scientific and Technical Information (OSTI), janvier 1997. http://dx.doi.org/10.2172/468589.

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Clothiaux, Eugene E., Karen Johnson, Tami Toto, Pavlos Kollias, Katia Lamer, Scott E. Giangrande et Mariko Oue. Scanning ARM Cloud Radar—Advanced—Velocity Azimuth Display Value-Added Product. Office of Scientific and Technical Information (OSTI), janvier 2018. http://dx.doi.org/10.2172/1418465.

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Bickel, Douglas L. A Concept for Platform Velocity Estimation Using a Multiphase Center Radar. Office of Scientific and Technical Information (OSTI), novembre 2019. http://dx.doi.org/10.2172/1592858.

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Larsen, M. F. Radar interferometer Investigations of the Horizontal Winds, Vertical Velocities : EPSCoR Supplement for Student Support. Fort Belvoir, VA : Defense Technical Information Center, février 1997. http://dx.doi.org/10.21236/ada337289.

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Cohen, Arthur. Calculations of Temperature, Conductive Heat Flux, and Heat Wave Velocities Due to Radiant Heating of Opaque Materials. Fort Belvoir, VA : Defense Technical Information Center, novembre 2011. http://dx.doi.org/10.21236/ada553570.

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