Bibliographies thématiques / Velocity variations / Articles de revues
Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Velocity variations.

Articles de revues sur le sujet « Velocity variations »

Auteur : Grafiati
Publié le 10 mars 2023

Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres

Choisissez une source :

Consultez les 50 meilleurs articles de revues pour votre recherche sur le sujet « Velocity variations ».

À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.

Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.

Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.

1

Wang, A., D. Leparoux, O. Abraham et M. Le Feuvre. « Frequency derivative of Rayleigh wave phase velocity for fundamental mode dispersion inversion : parametric study and experimental application ». Geophysical Journal International 224, no 1 (4 septembre 2020) : 649–68. http://dx.doi.org/10.1093/gji/ggaa417.

Texte intégral
Résumé :
SUMMARY Monitoring the small variations of a medium is increasingly important in subsurface geophysics due to climate change. Classical seismic surface wave dispersion methods are limited to quantitative estimations of these small variations when the variation ratio is smaller than 10 per cent, especially in the case of variations in deep media. Based on these findings, we propose to study the contributions of the Rayleigh wave phase velocity derivative with respect to frequency. More precisely, in the first step of assessing its feasibility, we analyse the effects of the phase velocity derivative on the inversion of the fundamental mode in the simple case of a two-layer model. The behaviour of the phase velocity derivative is first analysed qualitatively: the dispersion curves of phase velocity, group velocity and the phase velocity derivative are calculated theoretically for several series of media with small variations. It is shown that the phase velocity derivatives are more sensitive to variations of a medium. The sensitivity curves are then calculated for the phase velocity, the group velocity and the phase velocity derivative to perform quantitative analyses. Compared to the phase and group velocities, the phase velocity derivative is sensitive to variations of the shallow layer and the deep layer shear wave velocity in the same wavelength (frequency) range. Numerical data are used and processed to obtain dispersion curves to test the feasibility of the phase velocity derivative in the inversion. The inversion results of the phase velocity derivative are compared with those of phase and group velocities and show improved estimations for small variations (variation ratio less than 5 per cent) of deep layer shear wave velocities. The study is focused on laboratory experiments using two reduced-scale resin-epoxy models. The differences of these two-layer models are in the deep layer in which the variation ratio is estimated as 16.4 ± 1.1 per cent for the phase velocity inversion and 17.1 ± 0.3 per cent for the phase velocity derivative. The latter is closer to the reference value 17 per cent, with a smaller error.
Styles APA, Harvard, Vancouver, ISO, etc.
2

Hatzes, Artie P. « Radial Velocity Variations from Starspots ». International Astronomical Union Colloquium 170 (1999) : 259–63. http://dx.doi.org/10.1017/s0252921100048648.

Texte intégral
Résumé :
AbstractIn this contribution the radial velocity (RV) variations expected for starspots on solar-type stars are examined. The spot-induced RV amplitude is found to vary linearly with spot filling factor and is less than 1 m−1 for spot sizes comparable to large sunspots and as high as 20 m s−1 for spot filling factors of 1%. Also, for a given spot size the RV amplitude increases linearly with υ sin i. All of these findings confirm the results of Saar & Donahue (1997). It is also shown that two spectral lines with different temperature sensitivity can have different RV amplitudes which may provide a diagnostic for confirming planet detections. The RV variations due to starspots correlate well with the displacement of the line core and centroid and this can be used to correct RV measurements for the effects of cool starspots.
Styles APA, Harvard, Vancouver, ISO, etc.
3

de Cacqueray, Benoit, Philippe Roux, Michel Campillo et Stefan Catheline. « Tracking of velocity variations at depth in the presence of surface velocity fluctuations ». GEOPHYSICS 78, no 1 (1 janvier 2013) : U1—U8. http://dx.doi.org/10.1190/geo2012-0071.1.

Texte intégral
Résumé :
We tested a small-scale experiment that is dedicated to the study of the wave separation algorithm and to the velocity variations monitoring problem itself. It handles the case in which velocity variations at depth are hidden by near-surface velocity fluctuations. Using an acquisition system that combines an array of sources and an array of receivers, coupled with controlled velocity variations, we tested the ability of beam-forming techniques to track velocity variations separately for body waves and surface waves. After wave separation through double beam forming, the arrival time variations of the different waves were measured through the phase difference between the extracted wavelets. Finally, a method was tested to estimate near-surface velocity variations using surface waves or shallow reflection and compute a correction to isolate target velocity variations at depth.
Styles APA, Harvard, Vancouver, ISO, etc.
4

Zhang, Yu-Shen, et Thorne Lay. « Global surface wave phase velocity variations ». Journal of Geophysical Research : Solid Earth 101, B4 (10 avril 1996) : 8415–36. http://dx.doi.org/10.1029/96jb00167.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
5

Andreasen, Jørn-Ole. « Apparent Short-Term Glacier Velocity Variations ». Journal of Glaciology 31, no 107 (1985) : 49–53. http://dx.doi.org/10.1017/s0022143000004986.

Texte intégral
Résumé :
AbstractIn connection with a glacier-hydrological project at a sub-polar glacier in West Greenland, short-term glacier velocity variations were measured. Both the horizontal and the vertical velocity components showed distinct diurnal variations. Close examination indicates that these variations are caused by the change in atmospheric refraction during the day, with the vertical component as the most important.
Styles APA, Harvard, Vancouver, ISO, etc.
6

Moreno, M., J. Torra et E. Oblak. « Local Variations of the Velocity Ellipsoid ». Symposium - International Astronomical Union 169 (1996) : 525–26. http://dx.doi.org/10.1017/s0074180900230271.

Texte intégral
Résumé :
We have analyzed the distribution of residual velocities of nearby stars (within 200 pc of the Sun) looking for space variations on the velocity ellipsoid. We used a sample of 1071 main sequence stars of spectral types B, A and F selected from the Hipparcos Input Catalogue [7] with uvbyHβ photometric data. Ages have been calculated following [1]. Six subsamples with 8.07 ≤ log(age) ≤ 9.45 have been considered.
Styles APA, Harvard, Vancouver, ISO, etc.
7

Andreasen, Jørn-Ole. « Apparent Short-Term Glacier Velocity Variations ». Journal of Glaciology 31, no 107 (1985) : 49–53. http://dx.doi.org/10.3189/s0022143000004986.

Texte intégral
Résumé :
AbstractIn connection with a glacier-hydrological project at a sub-polar glacier in West Greenland, short-term glacier velocity variations were measured. Both the horizontal and the vertical velocity components showed distinct diurnal variations. Close examination indicates that these variations are caused by the change in atmospheric refraction during the day, with the vertical component as the most important.
Styles APA, Harvard, Vancouver, ISO, etc.
8

Chauhan, A., P. Mullins, M. C. Petch et P. M. Schofield. « Variations in Resting Coronary Flow Velocity ». Clinical Science 84, s28 (1 mars 1993) : 14P. http://dx.doi.org/10.1042/cs084014p.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
9

Ranum, Madeline, Carl Foster, Clayton Camic, Glenn Wright, Flavia Guidotti, Jos J. de Koning, Christopher Dodge et John P. Porcari. « Effect of Running Velocity Variation on the Aerobic Cost of Running ». International Journal of Environmental Research and Public Health 18, no 4 (19 février 2021) : 2025. http://dx.doi.org/10.3390/ijerph18042025.

Texte intégral
Résumé :
The aerobic cost of running (CR), an important determinant of running performance, is usually measured during constant speed running. However, constant speed does not adequately reflect the nature of human locomotion, particularly competitive races, which include stochastic variations in pace. Studies in non-athletic individuals suggest that stochastic variations in running velocity produce little change in CR. This study was designed to evaluate whether variations in running speed influence CR in trained runners. Twenty competitive runners (12 m, VO2max = 73 ± 7 mL/kg; 8f, VO2max = 57 ± 6 mL/kg) ran four 6-minute bouts at an average speed calculated to require ~90% ventilatory threshold (VT) (measured using both v-slope and ventilatory equivalent). Each interval was run with minute-to-minute pace variation around average speed. CR was measured over the last 2 min. The coefficient of variation (CV) of running speed was calculated to quantify pace variations: ±0.0 m∙s−1 (CV = 0%), ±0.04 m∙s−1 (CV = 1.4%), ±0.13 m∙s−1(CV = 4.2%), and ±0.22 m∙s−1(CV = 7%). No differences in CR, HR, or blood lactate (BLa) were found amongst the variations in running pace. Rating of perceived exertion (RPE) was significantly higher only in the 7% CV condition. The results support earlier studies with short term (3s) pace variations, that pace variation within the limits often seen in competitive races did not affect CR when measured at running speeds below VT.
Styles APA, Harvard, Vancouver, ISO, etc.
10

González, Diego M., Klaus Bataille, Tom Eulenfeld et Luis E. Franco. « Temporal seismic wave velocity variations at Láscar volcano ». Andean Geology 43, no 2 (19 mai 2016) : 240. http://dx.doi.org/10.5027/andgeov43n2-a05.

Texte intégral
Résumé :
We report on the first study using Seismic Wave Interferometry to determine variations of seismic velocities through time, in the vicinity of Láscar volcano in Chile. Seismic Wave Interferometry has been used as a powerful tool to determine spatial and temporal changes of seismic velocities within the Earth. Spatial variations of seismic velocities are related to heterogeneities of material properties, which are expected to occur in a complex structure. However, temporal changes are indicative of dynamic process within the elastic media, and thus, this tool can be used to monitor dynamic processes at volcanic zones. We find consistent variations on three stations close to the volcano, with dv/v of ±0.6%, most likely related to the inflation/deflation process due to fluid movement of magmatic or hydrothermal origin within the volcanic structure. During the observed period of velocity variation, OVDAS reported an increase of volcanic activity evidenced by the increase of the number of long period seismic events, increase of gas emissions and the formation of incandescence above the crater. We suggest that this tool can contribute to the understanding of volcano related dynamic processes, as well as for routine volcano monitoring purposes.
Styles APA, Harvard, Vancouver, ISO, etc.
11

Tieman, Hans J. « Migration velocity analysis : Accounting for the effects of lateral velocity variations ». GEOPHYSICS 60, no 1 (janvier 1995) : 164–75. http://dx.doi.org/10.1190/1.1443743.

Texte intégral
Résumé :
The most common migration velocity analysis algorithms, iterative profile migration, focusing analysis, and stack power analysis are based on restrictive subsurface assumptions that may cause the methods to break down in the presence of lateral velocity variations. Typically, the subsurface is assumed to have either a constant velocity, or at most, a depth variable velocity. Recent innovations include the use of traveltime inversion philosophy to invert migration measurements of the curvature as a function of offset exhibited by an event following migration. Traveltime inversion makes few assumptions regarding the subsurface, but is a rather unstable process. Thus, an important question is, “Under what conditions do the traditional methods break down and make the use of traveltime inversion methods mandatory?” Marrying the common migration analysis with tomography results in a set of equations that, while useful for generating updates from migration measurements, are too complex for answering the above question. However, by restricting the subsurface to low relief structures and assuming small angle wave propagation, these updating equations can be approximated by forms that are identical to the traditional updating equations, except for a factor that is dependent upon the magnitude, position, and spatial wavelength of potential lateral velocity variations. These simpler equations indicate that even relatively long wavelength anomalies can cause updates to point in the wrong direction and iterative procedures to diverge, and under certain conditions, cause the accuracy of these updates to decrease dramatically.
Styles APA, Harvard, Vancouver, ISO, etc.
12

Swan, Herbert W. « Velocities from amplitude variations with offset ». GEOPHYSICS 66, no 6 (novembre 2001) : 1735–43. http://dx.doi.org/10.1190/1.1487115.

Texte intégral
Résumé :
The sensitivity of amplitude variations with offset (AVO) to normal‐moveout (NMO) velocity errors has usually been taken to be a significant limitation of the method. However, this sensitivity can, in most cases, be exploited to obtain more accurate velocities from a fully automated procedure. The error due to velocity in the AVO gradient is in phase quadrature with the AVO zero‐offset intercept. Furthermore, if the majority of reflectors within a suitable data window contain a similar gradient quadrature component, then it may be inferred that this component is due to an NMO velocity error. Both the intercept and gradient traces may be made analytic (complex) by combining them with i times their Hilbert transforms. The imaginary part of their joint correlation coefficient quantifies the gradient quadrature component and is proportional to the average of the fractional NMO velocity error over the data window. Unlike semblance, which is always positive, the sign of the imaginary correlation coefficient indicates whether the NMO velocity is too high or too low. The optimal NMO velocity, according to this criterion, is the one which nulls this imaginary correlation. This criterion minimizes the AVO gradient error, but does not necessarily maximize the full stack energy or yield the optimal stacking velocity. Because a null is picked, not a peak, the NMO velocity resolution is greatly improved. A velocity picking method is presented, which consists of the following steps: AVO analysis, removal of NMO stretch errors, calculation of the joint statistics between the analytic intercepts and gradients, and picking an NMO velocity to null this indicator. The velocity picking may be performed either manually or automatically through iteration. Automatic picking is computationally more efficient than it would be with semblance because only one correlation trace is calculated for each iteration, instead of one for every trial velocity. This efficiency makes velocity picking of every gather in a 3‐D survey feasible.
Styles APA, Harvard, Vancouver, ISO, etc.
13

Yang, Dong Ya, et Jun Gong. « Visualized Equivalent Variational Modeling in Tolerance Analysis of 3D Mechanical Assemblies ». Advanced Materials Research 201-203 (février 2011) : 229–33. http://dx.doi.org/10.4028/www.scientific.net/amr.201-203.229.

Texte intégral
Résumé :
This paper introduces a new, visualized approach for including all the geometric feature variations in the tolerance analysis of mechanical assemblies. It focuses on how to characterize geometric feature variations in vector-loop-based assembly tolerance models. The characterization will be used to help combine the effects of all variations within an assembly in order to perform tolerance analysis of mechanical assemblies by employing commercial 3D kinematic software (e.g. ADAMS). Equivalent variational modeling, based on TAKS method, has been developed for modeling variations in 3D mechanical assemblies. Create a library of Equivalent Variational Joints (EVJs) to allow inclusion all kinds of variations in analysis, and allow the kinematic model to include both geometric and dimensional variation in a velocity analysis. EVJ, for use in tolerance analysis, was developed for commonly used 3D kinematic joint types, and was implemented with examples to explain their use to form Equivalent Variational Mechanisms (EVMs).
Styles APA, Harvard, Vancouver, ISO, etc.
14

ERN, ALEXANDRE. « VORTICITY–VELOCITY FORMULATION OF THE STOKES PROBLEM WITH VARIABLE DENSITY AND VISCOSITY ». Mathematical Models and Methods in Applied Sciences 08, no 02 (mars 1998) : 203–18. http://dx.doi.org/10.1142/s021820259800010x.

Texte intégral
Résumé :
We investigate the vorticity–velocity formulation of the stationary, two-dimensional Stokes problem in the case of variable density and viscosity. The analysis is presented in the low Mach number regime, where the density is independent of spatial variations of the pressure. We introduce a variational framework and prove the equivalence of the vorticity–velocity and velocity–pressure formulations in appropriate functional spaces. We then derive a weak formulation for the Stokes equations in vorticity–velocity form. Finally, when the spatial variations of the density and of the viscosity are small enough, we prove the existence and uniqueness of the solution to the Stokes problem in both vorticity–velocity and velocity–pressure forms.
Styles APA, Harvard, Vancouver, ISO, etc.
15

Hatzes, A. P., et D. E. Mkrtichian. « Radial velocity variations in pulsating Ap stars ». Astronomy & ; Astrophysics 430, no 1 (janvier 2005) : 279–86. http://dx.doi.org/10.1051/0004-6361:20034171.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
16

Mkrtichian, D. E., et A. P. Hatzes. « Radial velocity variations in pulsating Ap stars ». Astronomy & ; Astrophysics 430, no 1 (janvier 2005) : 263–78. http://dx.doi.org/10.1051/0004-6361:20034547.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
17

Figueira, P., N. C. Santos, F. Pepe, C. Lovis et N. Nardetto. « Line-profile variations in radial-velocity measurements ». Astronomy & ; Astrophysics 557 (septembre 2013) : A93. http://dx.doi.org/10.1051/0004-6361/201220779.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
18

Stempels, H. C., G. F. Gahm et P. P. Petrov. « Periodic radial velocity variations in RU Lupi ». Astronomy & ; Astrophysics 461, no 1 (26 septembre 2006) : 253–59. http://dx.doi.org/10.1051/0004-6361:20065268.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
19

Margrave, Gary F. « Direct Fourier migration for vertical velocity variations ». GEOPHYSICS 66, no 5 (septembre 2001) : 1504–14. http://dx.doi.org/10.1190/1.1487096.

Texte intégral
Résumé :
The Stolt f‐x migration algorithm is a direct (i.e. nonrecursive) Fourier‐domain technique based on a change of variables, or equivalently a mapping, that converts the unmigrated spectrum to the migrated spectrum. The algorithm is simple and efficient but limited to constant velocity. A v(z) f‐k migration method, capable of very high accuracy for vertical velocity variations, can be formulated as a nonstationary filter that avoids the change of variables. The result is a direct Fourier‐domain process that, for each wavenumber, applies a nonstationary migration filter to a vector of input frequency samples to create a vector of output frequency samples. The filter matrix is analytically specified in the mixed domain of input frequency and migrated time. It can be moved to the full‐Fourier domain of input frequency and output frequency by a fast Fourier transform. When applied for constant velocity, the v(z) f‐k algorithm is slower than the Stolt method but without the usual artifacts related to complex‐valued frequency‐domain interpolation. Vertical velocity variations, through an rms‐velocity (straight‐ray) assumption, are handled by the v(z) f‐k method with no additional cost. Greater accuracy at slight additional expense is obtained by extending the method to a WKBJ phase‐shift integral. This has the same accuracy as recursive phase shift and is similar in cost. For constant velocity, the full‐Fourier domain migration filter is a discrete approximation to a Dirac delta function whose singularity tracks along a hyperbola determined by the migration velocity. For variable velocity, the migration filter has significant energy between hyperbolic trajectories determined by the minimum and maximum instantaneous velocities. The full‐Fourier domain offers interesting conceptual parallels to Stolt’s algorithm. However, unless a more efficient method of calculating the Fourier filter matrix can be found, the mixed‐domain method will be faster. The mixed‐domain nonstationary filter moves the input data from the Fourier domain to the migrated time domain as it migrates. It is faster because the migration filter is known analytically in the mixed domain.
Styles APA, Harvard, Vancouver, ISO, etc.
20

Irwin, Alan W., Bruce Campbell, Christopher L. Morbey, G. A. H. Walker et S. Yang. « Long-period radial-velocity variations of Arcturus ». Publications of the Astronomical Society of the Pacific 101 (février 1989) : 147. http://dx.doi.org/10.1086/132415.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
21

Yang, Stephenson L. S., Gordon A. H. Walker et Ana M. Larson. « Radial-velocity Variations of Late-type Variables ». International Astronomical Union Colloquium 170 (1999) : 228–32. http://dx.doi.org/10.1017/s0252921100048600.

Texte intégral
Résumé :
AbstractLow-amplitude, radial-velocity variations of bright late-type stars were monitored at the 1.2-m telescope of the Dominion Astrophysical Observatory (DAO) with the hydrogen fluoride (HF) absorption-cell technique. Many of the stars appear to be semi-regular red variables (SRb and SRc) and irregular red variables (Lb). The radial-velocity amplitudes range from a few tens of meters per second to a few kilometers per second while the timescales of the variations appear to range from a few tens of days to a few hundreds of days. These irregular-looking velocities are analysed for multiperiodicities. There are also variations in the chromospheric Ca II 8662 index for a few of the variables.
Styles APA, Harvard, Vancouver, ISO, etc.
22

Irwin, Alan W., Bruce Campbell, C. L. Morbey, G. A. H. Walker et S. Yang. « Long-Period Radial-Velocity Variations of Arcturus ». International Astronomical Union Colloquium 106 (1989) : 144. http://dx.doi.org/10.1017/s0252921100062771.

Texte intégral
Résumé :
We have measured the relative radial velocity of Arcturus using the HF absorption cell technique on 43 occasions from 1981 through 1985. The range of our velocities is 500 m s-1, which is much larger than our estimated internal errors (typically 10 m s-1). This confirms the radial velocity variability of Arcturus that has been previously reported by our group and others based on shorter observational time spans.
Styles APA, Harvard, Vancouver, ISO, etc.
23

Niemela, V. S., R. H. Barbá et M. M. Shara. « The radial velocity variations of WR46 (WN3p) ». Symposium - International Astronomical Union 163 (1995) : 245–47. http://dx.doi.org/10.1017/s0074180900202040.

Texte intégral
Résumé :
Spectral observations of the WN3p star WR46 (HD 104994) obtained during June 1993 and January/February 1994 display large amplitude radial velocity variations of the strong emission lines Nv 4603-19Å and HeII 4686A, on a time scale of a fraction of a day. The most probable period found is 0.311 d, similar to the photometric period found by previous authors. The amplitude of the radial velocity variations of Nv emission is almost twice that of HeII. Noting the similarity of WR46 with low mass X-ray binaries, we suggest that the emission line spectrum corresponds to that of a luminous accretion disk in an evolved binary system.
Styles APA, Harvard, Vancouver, ISO, etc.
24

Parolai, S., D. Spallarossa et C. Eva. « Lateral variations ofPnwave velocity in northwestern Italy ». Journal of Geophysical Research : Solid Earth 102, B4 (10 avril 1997) : 8369–79. http://dx.doi.org/10.1029/96jb03834.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
25

Anthony, M. Y., D. H. Evans et M. I. Levene. « Cyclical variations in cerebral blood flow velocity. » Archives of Disease in Childhood 66, no 1 Spec No (1 janvier 1991) : 12–16. http://dx.doi.org/10.1136/adc.66.1_spec_no.12.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
26

Lazier, J. R. N., et D. G. Wright. « Annual Velocity Variations in the Labrador Current ». Journal of Physical Oceanography 23, no 4 (avril 1993) : 659–78. http://dx.doi.org/10.1175/1520-0485(1993)023<0659:avvitl>2.0.co;2.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
27

Sumaruk, T. P., et P. V. Sumaruk. « Dependence of the velocity changes of secular variations on the position of observatory and time ». Geofizicheskiy Zhurnal 43, no 3 (28 juillet 2021) : 181–92. http://dx.doi.org/10.24028/gzh.v43i3.236388.

Texte intégral
Résumé :
According to the data of world observatories net secular variations of geomagnetic fields from internal and outer sources have been studied. Averaged 3-year data have been used for this purpose. Procedure of calculations of secular variations from internal and outer sources according to observatories data has been submitted. 1979 has been chosen as a zero level for accounting secular variations from outer sources because the sign of the large-scale magnetic field has changed this year. It has been shown that the value of secular variations from outer sources is different for different regions and increases with the growth of the latitude of magnetic observatory. Maximal values of secular variations are observed in the northern polar cap as well as at the longitudes of the eastern focus of secular variation. It has been shown that at the DIK, CSS, TIK observatories secular variations have maximal values. Groups of observatories have been segregated with symmetric and asymmetric changes of secular variation comparing to 1979. Symmetric changes of secular variation during two Hail’s cycles are observed at the observatories in circumpolar area (ALE, NAL, BJN), in auroral and middle latitudes. Maximal asymmetry of secular variation is observed at the observatories GDH, BLC, FCC, as well as at certain subauroral observatories and the regions with raised seismic activity. Secular variation from outer sources depends on the value of the large scale magnetic field of the Sun. The value of secular variation from the inner sources has been modulated by the outer sources and depends on special features of underlying surfaces of the observatories, induction currents in particular.
Styles APA, Harvard, Vancouver, ISO, etc.
28

Rosenbush, A. « R CrB : Long‐period variations of radial velocity and velocity of outflow ». Astronomische Nachrichten 340, no 5 (juin 2019) : 398–408. http://dx.doi.org/10.1002/asna.201913634.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
29

Hanson, Brian, et Roger leb Hooke. « Short-term velocity variations and basal coupling near a bergschrund, Storglaciären, Sweden ». Journal of Glaciology 40, no 134 (1994) : 67–74. http://dx.doi.org/10.1017/s0022143000003804.

Texte intégral
Résumé :
AbstractDistance measurements using an automated electronic distance-measurement system in the north cirque of Storglaciären, Sweden, during the summer of 1989, revealed a diurnal variation in glacier speed. Amplitude and timing of the diurnal cycle correlate well with the timing and intensity of the diurnal temperature cycle, indicating that speed responds to variations in daily melt with a lag of approximately 4 h. One 2 d period of non-diurnal velocity variations corresponded with a large rainfall event. Finite-element modeling suggests that these velocity variations must be closely related to water inputs in the cirque rather than to longitudinal coupling with lower parts of the glacier.
Styles APA, Harvard, Vancouver, ISO, etc.
30

Hanson, Brian, et Roger leb Hooke. « Short-term velocity variations and basal coupling near a bergschrund, Storglaciären, Sweden ». Journal of Glaciology 40, no 134 (1994) : 67–74. http://dx.doi.org/10.3189/s0022143000003804.

Texte intégral
Résumé :
AbstractDistance measurements using an automated electronic distance-measurement system in the north cirque of Storglaciären, Sweden, during the summer of 1989, revealed a diurnal variation in glacier speed. Amplitude and timing of the diurnal cycle correlate well with the timing and intensity of the diurnal temperature cycle, indicating that speed responds to variations in daily melt with a lag of approximately 4 h. One 2 d period of non-diurnal velocity variations corresponded with a large rainfall event. Finite-element modeling suggests that these velocity variations must be closely related to water inputs in the cirque rather than to longitudinal coupling with lower parts of the glacier.
Styles APA, Harvard, Vancouver, ISO, etc.
31

Ibrahim, Muhammad Yusuf, Normansyah, Wien Lestari et Mariyanto Mariyanto. « Pull-Up Effect Correction and Oil In Place Sensitivity Test by Comparing Velocity Model Method in JAX-Field, Offshore North West Java ». IOP Conference Series : Earth and Environmental Science 873, no 1 (1 octobre 2021) : 012073. http://dx.doi.org/10.1088/1755-1315/873/1/012073.

Texte intégral
Résumé :
Abstract The pull-up effect is the condition of lithology elevated in seismic imaging because of rapid seismic wave propagation through carbonate build-up on it. Pull-up effect conditions can lead to misinterpretation, so it needs to be corrected until the actual geological conditions are obtained. This research was conducted in the JAX-field working area of PT Pertamina Hulu Energi ONWJ. The target reservoirs of this study are in the Main (Upper Cibulakan) Formation under the Carbonate Parigi Formation. The reflectors of the target reservoirs show pull-up effect in time domain seismic data. Thus, building a velocity model for velocity anomaly correction is needed to reduce uncertainty for structure maps and oil in place calculation. The method of correcting the pull-up effect in this study uses three variations of the velocity model: variation structurally controlled model, variation RMS velocity with well control, variation calibrated RMS velocities model. The three variations of the velocity model result can correct the pull-up effect on JAX-Field. Velocity model with variation RMS velocity with well control had the lowest error with 17,31 feet average of depth difference with actual depth from well. Based on three velocity models, the value of original oil in place on the JAX-32 reservoir surface had a range of 59,14-84,59 mmbo, while on the JAX-35A surface has a range of 27,77-31,23 mmbo. These values can be considered in reserve calculation sensitivity.
Styles APA, Harvard, Vancouver, ISO, etc.
32

Luan, Yi, Hongfeng Yang, Baoshan Wang, Wei Yang, Weitao Wang, Jun Yang et Xiaobin Li. « Time-Lapse Monitoring of Daily Velocity Changes in Binchuan, Southwestern China, Using Large-Volume Air-Gun Source Array Data ». Seismological Research Letters 93, no 2A (5 janvier 2022) : 914–30. http://dx.doi.org/10.1785/0220210160.

Texte intégral
Résumé :
Abstract Temporal changes of seismic velocities in the Earth’s crust can be induced by stress perturbations or material damage from reasons such as strong ground motion, volcanic activities, and atmospheric effects. However, monitoring the temporal changes remains challenging, because most of them generally exist in small travel-time differences of seismic data. Here, we present an excellent case of daily variations of the subsurface structure detected using a large-volume air-gun source array of one-month experiment in Binchuan, Yunnan, southwestern China. The seismic data were recorded by 12 stations within ∼10 km away from the source and used to detect velocity change in the crust using the deconvolution method and sliding window cross-correlation method, which can eliminate the “intercept” error when cutting the air-gun signals and get the real subsurface variations. Furthermore, the multichannel singular spectral analysis method is used to separate the daily change (∼1 cycle per day) from the “long-period” change (&lt;1 cycle per day) or noise. The result suggests that the daily velocity changes at the two nearest stations, 53277 (offset ∼700 m) and 53278 (offset ∼2.3 km), are well correlated with air temperature variation with a time lag of 5.0 ± 1.5 hr, which reflects that the velocity variations at the subsurface are likely attributed to thermoelastic strain. In contrast, both daily and long-period velocity changes at distant stations correlate better with the varying air pressure than the temperature, indicating that the velocity variations at deeper depth are dominated by the elastic loading of air pressure. Our results demonstrate that the air-gun source is a powerful tool to detect the velocity variation of the shallow crust media.
Styles APA, Harvard, Vancouver, ISO, etc.
33

Hatzes, Artie P., et William D. Cochran. « Radial Velocity Variability of K Giants ». International Astronomical Union Colloquium 130 (1991) : 386–88. http://dx.doi.org/10.1017/s0252921100079987.

Texte intégral
Résumé :
AbstractAt McDonald Observatory we have been monitoring the relative radial velocities of a sample of K giants. The technique employed uses the telluric O2 lines near 6300 Å as a reference for measuring the stellar line shifts. We demonstrate that precisions of 10 m s−1 are possible with this technique. We present radial velocity data covering a 2 year time span for α Boo, α Tau, and β Gem. All of these stars show both long term variations (~ several hundred days) with a peak-to-peak amplitude of about 400 m s−1 and short term variations (~ few days) with a peak-to-peak amplitude of about 100 m s−1. The long term variations may be due to the rotational modulation of surface active regions whereas the short term variations may be indicative of pulsations.
Styles APA, Harvard, Vancouver, ISO, etc.
34

Santos, N. C., M. Mayor, D. Naef, D. Queloz et S. Udry. « Bisector analysis as a diagnostic of intrinsic radial-velocity variations ». Symposium - International Astronomical Union 202 (2004) : 121–23. http://dx.doi.org/10.1017/s007418090021766x.

Texte intégral
Résumé :
In this contribution we present the results of the application of the bisector of the cross-correlation function as a diagnostic of activity-related radial-velocity variations. The results show that the technique is very effective. We present examples for which the application of the bisector analysis was essential to establish the planetary nature of the candidate or to exclude an orbital signature. An analysis of the behaviour of the bisector for active dwarfs of different spectral types shows that the relation between the bisector and the radial-velocity variation depends in a great extent on thevsiniof the star. The results may shed a new light on the intrinsic sources of radial-velocity variation for different types of solar-type dwarfs.
Styles APA, Harvard, Vancouver, ISO, etc.
35

Sarma, M. S. S. R. K. N., C. Raghava Reddy et K. Niranjan. « HF Doppler radar observations of sporadic E at an Indian low latitude station, Visakhapatnam ». Annales Geophysicae 27, no 2 (2 février 2009) : 537–45. http://dx.doi.org/10.5194/angeo-27-537-2009.

Texte intégral
Résumé :
Abstract. 5.5 MHz HF Doppler radar observations of Sporadic E over an Indian low latitude station, Visakhapatnam (17.7° N, 83.3° E and Dip 20°) with 10 s resolution showed quasi-periodic variations of the echo strength and Doppler velocity variations with periods of a few minutes to a few tens of minutes. The echo strength and Doppler velocity variations with time in different range bins of the ES echo showed variations which are some times similar and some times significantly different in successive range bins at intervals of 7.5 km. The ES echo occurs with the height of maximum echo strength in the range of 100 km to 120 km and some times at 130 km. The altitude variation of the average Doppler velocity is highly variable and the height of maximum echo strength is not the same as the height of maximum Doppler velocity. Observations of ES echoes at different times of the day are presented to bring out the differences between the day and night time ES echoes. The relationship between Radar and ES parameters derived from Ionograms is poorer than that of mid latitudes which is quite consistent with the expectations based on gradient drift instability.
Styles APA, Harvard, Vancouver, ISO, etc.
36

Thethy, Bhavraj, David Tairych et Daniel Edgington-Mitchell. « Mechanics of the influx phase in the jet regurgitant mode of a powered resonance tube ». International Journal of Aeroacoustics 18, no 2-3 (avril 2019) : 279–98. http://dx.doi.org/10.1177/1475472x19840001.

Texte intégral
Résumé :
Time-resolved visualisation of shock wave motion within a powered resonant tube (PRT) is presented for the regurgitant mode of operation. Shock position and velocity are measured as functions of both time and space from ultra-high-speed schlieren visualisations. The shock wave velocity is seen to vary across the resonator length for both the incident and reflected waves. Three mechanisms are explored as explanations for the variation in velocity: change in local fluid velocity, variation in shock strength and variations in local temperature. For the incident wave, local fluid velocity and shock strength are extracted from the data and both are demonstrated to contribute to the observed variation, with a non-trivial remainder likely explained by variation in temperature.
Styles APA, Harvard, Vancouver, ISO, etc.
37

Stodden, David F., Glenn S. Fleisig, Scott P. McLean, Stephen L. Lyman et James R. Andrews. « Relationship of Pelvis and Upper Torso Kinematics to Pitched Baseball Velocity ». Journal of Applied Biomechanics 17, no 2 (mai 2001) : 164–72. http://dx.doi.org/10.1123/jab.17.2.164.

Texte intégral
Résumé :
Generating consistent maximum ball velocity is an important factor for a baseball pitcher’s success. While previous investigations have focused on the role of the upper and lower extremities, little attention has been given to the trunk. In this study it was hypothesized that variations in pelvis and upper torso kinematics within individual pitchers would be significantly associated with variations in pitched ball velocity. Nineteen elite baseball pitchers were analyzed using 3-D high-speed motion analysis. For inclusion in this study, each pitcher demonstrated a variation in ball velocity of at least 1.8 m/s (range: 1.8–3.5 m/s) during his 10 fastball pitch trials. A mixed-model analysis was used to determine the relationship between 12 pelvis and upper torso kinematic variables and pitched ball velocity. Results indicated that five variables were associated with variations in ball velocity within individual pitchers: pelvis orientation at maximum external rotation of the throwing shoulder (p= .026), pelvis orientation at ball release (p= .044), upper torso orientation at maximum external rotation of the throwing shoulder (p= .007), average pelvis velocity during arm cocking (p= .024), and average upper torso velocity during arm acceleration (p= .035). As ball velocity increased, pitchers showed an increase in pelvis orientation and upper torso orientation at the instant of maximal external rotation of the throwing shoulder. In addition, average pelvis velocity during arm cocking and average upper torso velocity during arm acceleration increased as ball velocity increased. From a practical perspective, the athlete should be coached to strive for proper trunk rotation during arm cocking as well as strength and flexibility in order to generate angular velocity within the trunk for maximum ball velocity.
Styles APA, Harvard, Vancouver, ISO, etc.
38

Winkler, Kenneth W. « Borehole damage indicator from stress-induced velocity variations ». GEOPHYSICS 70, no 1 (janvier 2005) : F11—F16. http://dx.doi.org/10.1190/1.1852772.

Texte intégral
Résumé :
I develop a simple technique to indicate the onset of stress-induced mechanical damage near a wellbore. Stress concentrations near a wellbore can cause the yield strength of the rock to be exceeded. The resulting mechanical damage causes a decrease in acoustic velocity that precedes the development of breakouts. With laboratory experiments on stressed boreholes, I show that high-resolution, shallow acoustic measurements made inside the borehole can detect these stress-induced velocity changes. The onset of damage can be predicted by comparing these shallow measurements to a deep velocity measurement in undamaged rock. When the maximum shallow velocity is decreased by damage and approaches the deep velocity, I infer that damage has occurred and breakouts and/or borehole failure are imminent. If implemented in the oilfield, this technique could form the basis for a real-time damage warning for drillers that allows for preventive action.
Styles APA, Harvard, Vancouver, ISO, etc.
39

Carlberg, R. G., et C. J. Grillmair. « VELOCITY VARIATIONS IN THE PHOENIX–HERMUS STAR STREAM ». Astrophysical Journal 830, no 2 (18 octobre 2016) : 135. http://dx.doi.org/10.3847/0004-637x/830/2/135.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
40

Figueira, P., N. C. Santos, F. Pepe, C. Lovis et N. Nardetto. « Line-profile variations in radial-velocity measurements(Corrigendum) ». Astronomy & ; Astrophysics 582 (octobre 2015) : C2. http://dx.doi.org/10.1051/0004-6361/201220779e.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
41

Marschall, Laurence A., Michael A. Seeds et Robert J. Davis. « Radial-velocity and light variations of IR Cephei ». Astronomical Journal 106 (septembre 1993) : 1123. http://dx.doi.org/10.1086/116711.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
42

Smith, P. H., R. S. McMillan et W. J. Merline. « Evidence for periodic radial velocity variations in Arcturus ». Astrophysical Journal 317 (juin 1987) : L79. http://dx.doi.org/10.1086/184916.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
43

Bertrand, Alexandre, et Colin MacBeth. « Seawater velocity variations and real-time reservoir monitoring ». Leading Edge 22, no 4 (avril 2003) : 351–55. http://dx.doi.org/10.1190/1.1572089.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
44

Winkler, Kenneth W. « Azimuthal velocity variations caused by borehole stress concentrations ». Journal of Geophysical Research : Solid Earth 101, B4 (10 avril 1996) : 8615–21. http://dx.doi.org/10.1029/96jb00093.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
45

Willems, B., et C. Aerts. « Tidally induced radial-velocity variations in close binaries ». Astronomy & ; Astrophysics 384, no 2 (mars 2002) : 441–51. http://dx.doi.org/10.1051/0004-6361:20020021.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
46

Chauhan, Anoop, Paul Mullins, Suren Thuraisingham, Gerard Taylor, Michael Petch et Peter Schofield. « Measurements of variations in resting coronary flow velocity ». International Journal of Angiology 2, no 02 (22 avril 2011) : 75–81. http://dx.doi.org/10.1007/bf02651563.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
47

Lehmann, Holger, et Gerhard Scholz. « Radial Velocity and Magnetic Variations of a Draconis ». International Astronomical Union Colloquium 138 (1993) : 612–16. http://dx.doi.org/10.1017/s0252921100021084.

Texte intégral
Résumé :
AbstractBased on photographic Zeeman spectra a magnetic field has been detected for the giant star α Dra. One of the two periods derived for the magnetic changes can be interpreted as the half rotational period corresponding to a slight variation of the radial velocity of 3.57 days. The application of an eguatorially symmetric rotator model with a magnetic field dominated by the quadrupole moment leads to a good agreement with the observed magnetic variation. The orbital elements of α Dra were newly derived.
Styles APA, Harvard, Vancouver, ISO, etc.
48

Prieur, Jean-Yves, et Jacques Joffrin. « Ultrasonic velocity variations in La2–xSrxCuO4 single crystals ». physica status solidi (c) 1, no 11 (novembre 2004) : 3061–64. http://dx.doi.org/10.1002/pssc.200405402.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
49

Jing, Lou, P. V. Ridd, C. L. Mayocchi et M. L. Heron. « Wave-induced Benthic Velocity Variations in Shallow Waters ». Estuarine, Coastal and Shelf Science 42, no 6 (juin 1996) : 787–802. http://dx.doi.org/10.1006/ecss.1996.0050.

Texte intégral
Styles APA, Harvard, Vancouver, ISO, etc.
50

Aðalgeirsdóttir, G., A. M. Smith, T. Murray, M. A. King, K. Makinson, K. W. Nicholls et A. E. Behar. « Tidal influence on Rutford Ice Stream, West Antarctica : observations of surface flow and basal processes from closely spaced GPS and passive seismic stations ». Journal of Glaciology 54, no 187 (2008) : 715–24. http://dx.doi.org/10.3189/002214308786570872.

Texte intégral
Résumé :
AbstractHigh-resolution surface velocity measurements and passive seismic observations from Rutford Ice Stream, West Antarctica, 40 km upstream from the grounding line are presented. These measurements indicate a complex relationship between the ocean tides and currents, basal conditions and ice-stream flow. Both the mean basal seismicity and the velocity of the ice stream are modulated by the tides. Seismic activity increases twice during each semi-diurnal tidal cycle. The tidal analysis shows the largest velocity variation is at the fortnightly period, with smaller variations superimposed at diurnal and semi-diurnal frequencies. The general pattern of the observed velocity is two velocity peaks during each semi-diurnal tidal cycle, but sometimes three peaks are observed. This pattern of two or three peaks is more regular during spring tides, when the largest-amplitude velocity variations are observed, than during neap tides. This is the first time that velocity and level of seismicity are shown to correlate and respond to tidal forcing as far as 40 km upstream from the grounding line of a large ice stream.
Styles APA, Harvard, Vancouver, ISO, etc.
Vous pouvez également être intéressé par les bibliographies sur le sujet « Velocity variations » pour d’autres types de sources :
Thèses Livres
Nous offrons des réductions sur tous les plans premium pour les auteurs dont les œuvres sont incluses dans des sélections littéraires thématiques. Contactez-nous pour obtenir un code promo unique!

Vers la bibliographie