PROJECTED ROTATIONAL VELOCITIES OF 136 EARLY B-TYPE STARS IN THE OUTER GALACTIC DISK
Garmany, C. D.; Glaspey, J. W. [National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719 (United States); Bragança, G. A.; Daflon, S.; Fernandes, M. Borges; Cunha, K. [Observatório Nacional-MCTI, Rua José Cristino, 77. CEP: 20921-400, Rio de Janeiro, RJ (Brazil); Oey, M. S. [University of Michigan, Department of Astronomy, 311 West Hall, 1085 S. University Ave., Ann Arbor, MI: 48109-1107 (United States); Bensby, T., E-mail: garmany@noao.edu [Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, SE-22100, Lund (Sweden)
2015-08-15
We have determined projected rotational velocities, v sin i, from Magellan/MIKE echelle spectra for a sample of 136 early B-type stars having large Galactocentric distances. The target selection was done independently of their possible membership in clusters, associations or field stars. We subsequently examined the literature and assigned each star as Field, Association, or Cluster. Our v sin i results are consistent with a difference in aggregate v sin i with stellar density. We fit bimodal Maxwellian distributions to the Field, Association, and Cluster subsamples representing sharp-lined and broad-lined components. The first two distributions, in particular, for the Field and Association are consistent with strong bimodality in v sin i. Radial velocities are also presented, which are useful for further studies of binarity in B-type stars, and we also identify a sample of possible new double-lined spectroscopic binaries. In addition, we find 18 candidate Be stars showing emission at Hα.
Aerts, C; Groot, P J; Degroote, P
2014-01-01
The Fourier Transform method is a popular tool to derive the rotational velocities of stars from their spectral line profiles. However, its domain of validity does not include line-profile variables with time-dependent profiles. We investigate the performance of the method for such cases, by interpreting the line-profile variations of spotted B stars, and of pulsating B tars, as if their spectral lines were caused by uniform surface rotation along with macroturbulence. We perform time-series analysis and harmonic least-squares fitting of various line diagnostics and of the outcome of several implementations of the Fourier Transform method. We find that the projected rotational velocities derived from the Fourier Transform vary appreciably during the pulsation cycle whenever the pulsational and rotational velocity fields are of similar magnitude. The macroturbulent velocities derived while ignoring the pulsations can vary with tens of km/s during the pulsation cycle. The temporal behaviour of the deduced rotat...
Jackson, R J; Lewis, J; Koposov, S E; Sacco, G G; Randich, S; Gilmore, G; Asplund, M; Binney, J; Bonifacio, P; Drew, J E; Feltzing, S; Ferguson, A M N; Micela, G; Neguerela, I; Prusti, T; Rix, H-W; Vallenari, A; Alfaro, E J; Allende~Prieto, C; Babusiaux, C; Bensby, T; Blomme, R; Bragaglia, A; Flaccomio, E; Francois, P; Hambly, N; Irwin, M; Korn, A J; Lanzafame, A C; Pancino, E; Recio-Blanco, A; Smiljanic, R; Van Eck, S; Walton, N; Bayo, A; Bergemann, M; Carraro, G; Costado, M T; Damiani, F; Edvardsson, B; Franciosini, E; Frasca, A; Heiter, U; Hill, V; Hourihane, A; Jofre, P; Lardo, C; de Laverny, P; Lind, K; Magrini, L; Marconi, G; Martayan, C; Masseron, T; Monaco, L; Morbidelli, L; Prisinzano, L; Sbordone, L; Sousa, S G; Worley, C C; Zaggia, S
2015-01-01
The Gaia-ESO Survey (GES) is a large public spectroscopic survey at the European Southern Observatory Very Large Telescope. A key aim is to provide precise radial velocities (RVs) and projected equatorial velocities (v sin i) for representative samples of Galactic stars, that will complement information obtained by the Gaia astrometry satellite. We present an analysis to empirically quantify the size and distribution of uncertainties in RV and v sin i using spectra from repeated exposures of the same stars. We show that the uncertainties vary as simple scaling functions of signal-to-noise ratio (S/N) and v sin i, that the uncertainties become larger with increasing photospheric temperature, but that the dependence on stellar gravity, metallicity and age is weak. The underlying uncertainty distributions have extended tails that are better represented by Student's t-distributions than by normal distributions. Parametrised results are provided, that enable estimates of the RV precision for almost all GES measure...
Reciprocally-Rotating Velocity Obstacles
Giese, Andrew
2014-05-01
© 2014 IEEE. Modern multi-agent systems frequently use highlevel planners to extract basic paths for agents, and then rely on local collision avoidance to ensure that the agents reach their destinations without colliding with one another or dynamic obstacles. One state-of-the-art local collision avoidance technique is Optimal Reciprocal Collision Avoidance (ORCA). Despite being fast and efficient for circular-shaped agents, ORCA may deadlock when polygonal shapes are used. To address this shortcoming, we introduce Reciprocally-Rotating Velocity Obstacles (RRVO). RRVO generalizes ORCA by introducing a notion of rotation for polygonally-shaped agents. This generalization permits more realistic motion than ORCA and does not suffer from as much deadlock. In this paper, we present the theory of RRVO and show empirically that it does not suffer from the deadlock issue ORCA has, permits agents to reach goals faster, and has a comparable collision rate at the cost of performance overhead quadratic in the (typically small) user-defined parameter δ.
Transverse velocity shifts in protostellar jets: rotation or velocity asymmetries?
De Colle, Fabio; Riera, Angels
2016-01-01
Observations of several protostellar jets show systematic differences in radial velocity transverse to the jet propagation direction, which have been interpreted as evidence of rotation in the jets. In this paper we discuss the origin of these velocity shifts, and show that they could be originated by rotation in the flow, or by side to side asymmetries in the shock velocity, which could be due to asymmetries in the jet ejection velocity/density or in the ambient medium. For typical poloidal jet velocities (~ 100-200 km/s), an asymmetry >~ 10% can produce velocity shifts comparable to those observed. We also present three dimensional numerical simulations of rotating, precessing and asymmetric jets, and show that, even though for a given jet there is a clear degeneracy between these effects, a statistical analysis of jets with different inclination angles can help to distinguish between the alternative origins of transverse velocity shifts. Our analysis indicate that side to side velocities asymmetries could ...
A method to deconvolve stellar rotational velocities
Cure, Michel; Cassetti, Julia; Christen, Alejandra
2014-01-01
Rotational speed is an important physical parameter of stars and knowing the distribution of stellar rotational velocities is essential for the understanding stellar evolution. However, it cannot be measured directly but the convolution of the rotational speed and the sine of the inclination angle, $v \\sin i$. We developed a method to deconvolve this inverse problem and obtain the cumulative distribution function (CDF) for stellar rotational velocities extending the work of Chandrasekhar & M\\"unch (1950). This method is applied a) to theoretical synthetic data recovering the original velocity distribution with very small error; b) to a sample of about 12.000 field main--sequence stars, corroborating that the velocity distribution function is non--Maxwellian, but is better described by distributions based on the concept of maximum entropy, such as Tsallis or Kaniadakis distribution functions. This is a very robust and novel method that deconvolve the rotational velocity cumulative distribution function fro...
A method to deconvolve stellar rotational velocities II
Christen, A; Cure, M; Rial, D F; Cassetti, J
2016-01-01
Knowing the distribution of stellar rotational velocities is essential for the understanding stellar evolution. Because we measure the projected rotational speed vsini, we need to solve an ill-posed problem given by a Fredholm integral of the first kind to recover the true rotational velocity distribution. After discretization of the Fredholm integral, we apply the Tikhonov regularization method to obtain directly the probability distribution function for stellar rotational velocities. We propose a simple and straightforward procedure to determine the Tikhonov parameter. We applied Monte Carlo simulations to prove that Tikhonov method is a consistent estimator and asymptotically unbiased. This method is applied to a sample of cluster stars. We obtain confidences intervals using bootstrap method. Our results are in good agreement with the one obtained using the Lucy method, in recovering the probability density distribution of rotational velocities. Furthermore, Lucy estimation lies inside our confidence inter...
Rotating Cavitation Supression Project
National Aeronautics and Space Administration — FTT proposes development of a rotating cavitation (RC) suppressor for liquid rocket engine turbopump inducers. Cavitation instabilities, such as rotating...
Radial velocity planet detection biases at the stellar rotational period
2016-01-01
Future generations of precise radial velocity (RV) surveys aim to achieve sensitivity sufficient to detect Earth mass planets orbiting in their stars' habitable zones. A major obstacle to this goal is astrophysical radial velocity noise caused by active areas moving across the stellar limb as a star rotates. In this paper, we quantify how stellar activity impacts exoplanet detection with radial velocities as a function of orbital and stellar rotational periods. We perform data-driven simulati...
Radial Velocity Planet Detection Biases at the Stellar Rotational Period
Vanderburg, Andrew; Johnson, John Asher; Ciardi, David R; Swift, Jonathan; Kane, Stephen R
2016-01-01
Future generations of precise radial velocity (RV) surveys aim to achieve sensitivity sufficient to detect Earth mass planets orbiting in their stars' habitable zones. A major obstacle to this goal is astrophysical radial velocity noise caused by active areas moving across the stellar limb as a star rotates. In this paper, we quantify how stellar activity impacts exoplanet detection with radial velocities as a function of orbital and stellar rotational periods. We perform data-driven simulations of how stellar rotation affects planet detectability and compile and present relations for the typical timescale and amplitude of stellar radial velocity noise as a function of stellar mass. We show that the characteristic timescales of quasi-periodic radial velocity jitter from stellar rotational modulations coincides with the orbital period of habitable zone exoplanets around early M-dwarfs. These coincident periods underscore the importance of monitoring the targets of RV habitable zone planet surveys through simul...
Trade Space Analysis: Rotational Analyst Research Project
2015-09-01
TRAC-M-TR-15-028 September 2015 Trade Space Analysis: Rotational Analyst Research Project TRADOC Analysis...PAGE INTENTIONALLY LEFT BLANK TRAC-M-TR-15-028 September 2015 Trade Space Analysis: Rotational Analyst Research Project...NUMBERS Trade Space Analysis : Rotational Analyst Research Project TRAC Project Code 060128 6. AUTHOR(S) Kirstin D Smead 7. PERFORMING
Velocity and rotation measurements in acoustically levitated droplets
Saha, Abhishek [University of Central Florida, Orlando, FL 32816 (United States); Basu, Saptarshi [Indian Institute of Science, Bangalore 560012 (India); Kumar, Ranganathan, E-mail: ranganathan.kumar@ucf.edu [University of Central Florida, Orlando, FL 32816 (United States)
2012-10-01
The velocity scale inside an acoustically levitated droplet depends on the levitator and liquid properties. Using Particle Imaging Velocimetry (PIV), detailed velocity measurements have been made in a levitated droplet of different diameters and viscosity. The maximum velocity and rotation are normalized using frequency and amplitude of acoustic levitator, and droplet viscosity. The non-dimensional data are fitted for micrometer- and millimeter-sized droplets levitated in different levitators for different viscosity fluids. It is also shown that the rotational speed of nanosilica droplets at an advanced stage of vaporization compares well with that predicted by exponentially fitted parameters. -- Highlights: ► Demonstrates the importance of rotation in a levitated droplet that leads to controlled morphology. ► Provides detailed measurements of Particle Image Velocimetry inside levitated droplets. ► Shows variation of vortex strength with the droplet diameter and viscosity of the liquid.
Rotational Velocities of Individual Components in Very Low Mass Binaries
Konopacky, Q. M.; Ghez, A. M.; Fabrycky, D. C.; Macintosh, B. A.; White, R. J.; Barman, T. S.; Rice, E. L.; Hallinan, G.; Duchêne, G.
2012-05-01
We present rotational velocities for individual components of 11 very low mass (VLM) binaries with spectral types between M7 and L7.5. These results are based on observations taken with the near-infrared spectrograph, NIRSPEC, and the Keck II laser guide star adaptive optics system. We find that the observed sources tend to be rapid rotators (v sin i > 10 km s-1), consistent with previous seeing-limited measurements of VLM objects. The two sources with the largest v sin i, LP 349-25B and HD 130948C, are rotating at ~30% of their break-up speed, and are among the most rapidly rotating VLM objects known. Furthermore, five binary systems, all with orbital semimajor axes lsim3.5 AU, have component v sin i values that differ by greater than 3σ. To bring the binary components with discrepant rotational velocities into agreement would require the rotational axes to be inclined with respect to each other, and that at least one component is inclined with respect to the orbital plane. Alternatively, each component could be rotating at a different rate, even though they have similar spectral types. Both differing rotational velocities and inclinations have implications for binary star formation and evolution. We also investigate possible dynamical evolution in the triple system HD 130948A-BC. The close binary brown dwarfs B and C have significantly different v sin i values. We demonstrate that components B and C could have been torqued into misalignment by the primary star, A, via orbital precession. Such a scenario can also be applied to another triple system in our sample, GJ 569A-Bab. Interactions such as these may play an important role in the dynamical evolution of VLM binaries. Finally, we note that two of the binaries with large differences in component v sin i, LP 349-25AB and 2MASS 0746+20AB, are also known radio sources.
ROTATIONAL VELOCITIES OF INDIVIDUAL COMPONENTS IN VERY LOW MASS BINARIES
Konopacky, Q. M.; Macintosh, B. A. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Ghez, A. M. [UCLA Division of Astronomy and Astrophysics, Los Angeles, CA 90095-1562 (United States); Fabrycky, D. C. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); White, R. J. [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 (United States); Barman, T. S. [Lowell Observatory, 1400 W. Mars Hill Rd., Flagstaff, AZ 86001 (United States); Rice, E. L. [American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024-5192 (United States); Hallinan, G. [Department of Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Duchene, G., E-mail: macintosh1@llnl.gov, E-mail: konopacky@di.utoronto.ca, E-mail: ghez@astro.ucla.edu, E-mail: fabrycky@ucolick.org, E-mail: white@chara.gsu.edu, E-mail: barman@lowell.edu, E-mail: erice@amnh.org, E-mail: gh@astro.caltech.edu, E-mail: gduchene@berkeley.edu [Astronomy Department, University of California, Berkeley, Hearst Field Annex B-20, CA 94720-3411 (United States)
2012-05-01
We present rotational velocities for individual components of 11 very low mass (VLM) binaries with spectral types between M7 and L7.5. These results are based on observations taken with the near-infrared spectrograph, NIRSPEC, and the Keck II laser guide star adaptive optics system. We find that the observed sources tend to be rapid rotators (v sin i > 10 km s{sup -1}), consistent with previous seeing-limited measurements of VLM objects. The two sources with the largest v sin i, LP 349-25B and HD 130948C, are rotating at {approx}30% of their break-up speed, and are among the most rapidly rotating VLM objects known. Furthermore, five binary systems, all with orbital semimajor axes {approx}<3.5 AU, have component v sin i values that differ by greater than 3{sigma}. To bring the binary components with discrepant rotational velocities into agreement would require the rotational axes to be inclined with respect to each other, and that at least one component is inclined with respect to the orbital plane. Alternatively, each component could be rotating at a different rate, even though they have similar spectral types. Both differing rotational velocities and inclinations have implications for binary star formation and evolution. We also investigate possible dynamical evolution in the triple system HD 130948A-BC. The close binary brown dwarfs B and C have significantly different v sin i values. We demonstrate that components B and C could have been torqued into misalignment by the primary star, A, via orbital precession. Such a scenario can also be applied to another triple system in our sample, GJ 569A-Bab. Interactions such as these may play an important role in the dynamical evolution of VLM binaries. Finally, we note that two of the binaries with large differences in component v sin i, LP 349-25AB and 2MASS 0746+20AB, are also known radio sources.
Rotational Velocities of Individual Components in Very Low Mass Binaries
Konopacky, Q M; Fabrycky, D C; Macintosh, B A; White, R J; Barman, T S; Rice, E L; Hallinan, G; Duchene, G
2012-01-01
We present rotational velocities for individual components of eleven very low mass (VLM) binaries with spectral types between M7 and L7.5. These results are based on observations taken with the near-infrared spectrograph, NIRSPEC, and the Keck II laser guide star adaptive optics (LGS AO) system. We find that the observed sources tend to be rapid rotators (vsini > 10 km/s), consistent with previous seeing-limited measurements of VLM objects. The two sources with the largest vsini, LP 349-25B and HD 130948C, are rotating at ~30% of their break up speed, and are among the most rapidly rotating VLM objects known. Furthermore, five binary systems, all with orbital semi-major axes <3.5 AU, have component vsini values that differ by greater than 3sigma. To bring the binary components with discrepant rotational velocities into agreement would require the rotational axes to be inclined with respect to each other, and that at least one component is inclined with respect to the orbital plane. Alternatively, each comp...
The VLT-FLAMES Tarantula Survey XII. Rotational velocities of the single O-type stars
Ramírez-Agudelo, O H; Sana, H; de Koter, A; Sabín-Sanjulían, C; de Mink, S E; Dufton, P L; Gräfener, G; Evans, C J; Herrero, A; Langer, N; Lennon, D J; Apellániz, J Maíz; Markova, N; Najarro, F; Puls, J; Taylor, W D; Vink, J S
2013-01-01
Aims. Using ground based multi-object optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS), we aim to establish the (projected) rotational velocity distribution for a sample of 216 presumably single O-type stars in 30 Doradus (30 Dor). Methods. We measured projected rotational velocities, \\vrot, by means of a Fourier transform method and a profile fitting method applied on a set of isolated spectral lines. We also used an iterative deconvolution procedure to infer the probability density, $\\rm{P(\\veq)}$, of the equatorial rotational velocity, \\veq. Results. The distribution of \\vrot\\ shows a two-component structure: a peak around 80 \\kms\\ and a high-velocity tail extending up to $\\sim$600 \\kms. This structure is also present in the inferred distribution $\\rm{P(\\veq)}$ with around 80% of the sample having 0 $<$ \\veq\\, $\\leq\\, 300$ \\kms\\ and the other 20% distributed in the high-velocity region. Conclusions. Most of the stars in our sample rotate with a rate less than 20%\\...
The Rotation of the halo of NGC 6822 from the radial velocities of carbon stars
Thompson, Graham P; Sibbons, Lisette F
2016-01-01
Using spectra taken with the AAOmega spectrograph, we measure the radial velocities of over 100 stars, many of which are intermediate age carbon stars, in the direction of the dwarf irregular galaxy NGC 6822. Kinematic analysis suggests that the carbon stars in the sample are associated with NGC 6822, and estimates of its radial velocity and galactic rotation are made from a star-by-star analysis of its carbon star population. We calculate a heliocentric radial velocity for NGC 6822 of $-51\\pm3$ \\kms\\ and show that the population rotates with a mean rotation speed of $11.2\\pm2.1$ \\kms\\ at a mean distance of 1.1 kpc from the galactic centre, about a rotation axis with a position angle of $26^\\circ\\pm13^\\circ$, as projected on the sky. This is close to the rotation axis of the HI gas disk and suggests that NGC 6822 is not a polar ring galaxy, but is dynamically closer to a late type galaxy. However, the rotation axis is not aligned with the minor axis of the AGB isodensity profiles and this remains a mystery.
ROTATING RINDLER SPACE TIME WITH CONSTANT ANGULAR VELOCITY
WANG YONG-CHENG
2000-01-01
A new space time metric is derived from Kerr metric if its mass and location approach to infinite in an appropriate way. The new space-time is an infinitesimal neighborhood nearby one of the two horizon poles of an infinite Kerr black hole. In other words, it is the second order infinitesimal neighborhood nearby one of the two horizon poles of a Kerr black hole. It is fiat and has event horizon and infinite red shift surface. We prove that it is a rotating Rindler space time with constant angular velocity.
The Betelgeuse Project: constraints from rotation
Wheeler, J. Craig; Nance, S.; Diaz, M.; Smith, S. G.; Hickey, J.; Zhou, L.; Koutoulaki, M.; Sullivan, J. M.; Fowler, J. M.
2017-03-01
In order to constrain the evolutionary state of the red supergiant Betelgeuse (α Orionis), we have produced a suite of models with zero-age main sequence masses from 15 to 25 M⊙ in intervals of 1 M⊙ including the effects of rotation. The models were computed with the stellar evolutionary code MESA. For non-rotating models, we find results that are similar to other work. It is somewhat difficult to find models that agree within 1σ of the observed values of R, Teff and L, but modestly easy within 3σ uncertainty. Incorporating the nominal observed rotational velocity, ∼15 km s-1, yields significantly different and challenging constraints. This velocity constraint is only matched when the models first approach the base of the red supergiant branch (RSB), having crossed the Hertzsprung gap, but not yet having ascended the RSB and most violate even generous error bars on R, Teff and L. Models at the tip of the RSB typically rotate at only ∼0.1 km s-1, independent of any reasonable choice of initial rotation. We discuss the possible uncertainties in our modelling and the observations, including the distance to Betelgeuse, the rotation velocity and model parameters. We summarize various options to account for the rotational velocity and suggest that one possibility is that Betelgeuse merged with a companion star of about 1 M⊙ as it ascended the RSB, in the process producing the ring structure observed at about 7 arcmin away. A past coalescence would complicate attempts to understand the evolutionary history and future of Betelgeuse.
The Betelgeuse Project: Constraints from Rotation
Diaz, Manuel; Nance, Sarafina; Sullivan, James; Wheeler, J. Craig
2017-01-01
In order to constrain the evolutionary state of the red supergiant Betelgeuse, we have produced a suite of models with ZAMS masses from 15 to 25 Msun in intervals of 1 Msun including the effects of rotation computed with the stellar evolutionary code MESA. For non--rotating models we find results that are similar to other work. It is somewhat difficult to find models that agree within 1 σ of the observed values of R, Teff and L, but modestly easy within 3 σ uncertainty. Incorporating the nominal observed rotational velocity, ~15 km/s, yields significantly different, and challenging, constraints. This velocity constraint is only matched when the models first approach the base of the red supergiant branch (RSB), having crossed the Hertzsprung gap, but not yet having ascended the RSB and most violate even generous error bars on R, Teff and L. Models at the tip of the RSB typically rotate at only ~0.1 km/s, independent of any reasonable choice of initial rotation. We discuss the possible uncertainties in our modeling and the observations, including the distance to Betelgeuse, the rotation velocity, and model parameters. We summarize various options to account for the rotational velocity and suggest that one possibility is that Betelgeuse merged with a companion star of about 1 Msun as it ascended the RSB, in the process producing the ring structure observed at about 7' away. A past coalescence would complicate attempts to understand the evolutionary history and future of Betelgeuse. To that end, we also present asteroseismology models with acoustic waves driven by inner convective regions that could elucidate the inner structure and evolutionary state.
Rotation and strain rate of Sulawesi from geometrical velocity field
Sarsito, D. A.; Susilo, Simons, W. J. F.; Abidin, H. Z.; Sapiie, B.; Triyoso, W.; Andreas, H.
2017-07-01
One of methods that can be used to determine the tectonic deformation status is rate estimation from geometric rotation and strain using quantitative velocity data from GPS observations. Microplate Sulawesi region located in the zone of triple junction (Eurasia, Australia and Philippine Sea Plates) has very complex tectonic and seismic condition, which is why become very important to know its recent deformation status in order to study neo-tectonic and disaster mitigation. Deformation rate quantification is estimated in two parameters: rotation and geodetic strain rate of each GPS station Delaunay triangle in the study area. The analysis in this study is not done using the grids since there is no rheological information at location that can be used as the interpolation-extrapolation constraints. Our analysis reveals that Sulawesi is characterized by rapid rotation in several different domains and compression-strain pattern that varies depending on the type and boundary conditions of microplate. This information is useful for studying neo tectonic deformation status and earthquake disaster mitigation.
The Betelgeuse Project: Constraints from Rotation
Wheeler, J Craig; Diaz, M; Smith, S G; Hickey, J; Zhou, L; Koutoulaki, M; Sullivan, J M; Fowler, J M
2016-01-01
In order to constrain the evolutionary state of the red supergiant Betelgeuse, we have produced a suite of models with ZAMS masses from 15 to 25 Msun in intervals of 1 Msun including the effects of rotation. The models were computed with the stellar evolutionary code MESA. For non-rotating models we find results that are similar to other work. It is somewhat difficult to find models that agree within 1 sigma of the observed values of R, Teff and L, but modestly easy within 3 sigma uncertainty. Incorporating the nominal observed rotational velocity, ~15 km/s, yields significantly different, and challenging, constraints. This velocity constraint is only matched when the models first approach the base of the red supergiant branch (RSB), having crossed the Hertzsprung gap, but not yet having ascended the RSB and most violate even generous error bars on R, Teff and L. Models at the tip of the RSB typically rotate at only ~0.1 km/s, independent of any reasonable choice of initial rotation. We discuss the possible u...
The VLT-FLAMES Tarantula Survey. XII. Rotational velocities of the single O-type stars
Ramírez-Agudelo, O. H.; Simón-Díaz, S.; Sana, H.; de Koter, A.; Sabín-Sanjulían, C.; de Mink, S. E.; Dufton, P. L.; Gräfener, G.; Evans, C. J.; Herrero, A.; Langer, N.; Lennon, D. J.; Maíz Apellániz, J.; Markova, N.; Najarro, F.; Puls, J.; Taylor, W. D.; Vink, J. S.
2013-12-01
Context. The 30 Doradus (30 Dor) region of the Large Magellanic Cloud, also known as the Tarantula nebula, is the nearest starburst region. It contains the richest population of massive stars in the Local Group, and it is thus the best possible laboratory to investigate open questions on the formation and evolution of massive stars. Aims: Using ground-based multi-object optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS), we aim to establish the (projected) rotational velocity distribution for a sample of 216 presumably single O-type stars in 30 Dor. The sample is large enough to obtain statistically significant information and to search for variations among subpopulations - in terms of spectral type, luminosity class, and spatial location - in the field of view. Methods: We measured projected rotational velocities, νesini, by means of a Fourier transform method and a profile fitting method applied to a set of isolated spectral lines. We also used an iterative deconvolution procedure to infer the probability density, P(νe), of the equatorial rotational velocity, νe. Results: The distribution of νesini shows a two-component structure: a peak around 80 kms-1 and a high-velocity tail extending up to ~600 kms-1. This structure is also present in the inferred distribution P(νe) with around 80% of the sample having 0 low-velocity peak is consistent with what has been found in other studies for late O- and early B-type stars. Conclusions: Most of the stars in our sample rotate with a rate less than 20% of their break-up velocity. For the bulk of the sample, mass loss in a stellar wind and/or envelope expansion is not efficient enough to significantly spin down these stars within the first few Myr of evolution. If massive-star formation results in stars rotating at birth with a large portion of their break-up velocities, an alternative braking mechanism, possibly magnetic fields, is thus required to explain the present
Changing law of launching pitching angular velocity of rotating missile
Liu Guang; Xu Bin; Jiao Xiaojuan; Zhen Tiesheng
2014-01-01
In order to provide accurate launching pitching angular velocity (LPAV) for the exterior trajectory optimization design, multi-flexible body dynamics (MFBD) technology is presented to study the changing law of LPAV of the rotating missile based on spiral guideway. An MFBD virtual prototype model of the rotating missile launching system is built using multi-body dynamics modeling technology based on the built flexible body models of key components and the special force model. The built model is verified with the frequency spectrum analysis. With the flexible body contact theory and nonlinear theory of MFBD technology, the research is conducted on the influence of a series of factors on LPAV, such as launching angle change, clearance between launching canister and missile, thrust change, thrust eccentricity and mass eccentricity, etc. Through this research, some useful values of the key design parameters which are difficult to be measured in physical tests are obtained. Finally, a simplified mathematical model of the changing law of LPAV is presented through fitting virtual test results using the linear regression method and verified by physical flight tests. The research results have important significance for the exterior trajectory optimization design.
ANGULAR VELOCITY AND CORIOLIS EFFECT IN TIME-DEPENDENT QUANTUM MECHANICAL SU2 ROTATION
FAN HONG-YI; SUN MING-ZHAI
2001-01-01
Starting from a time-dependent rotation U (t) in SU2 group element space, we derive its corresponding quantum mechanical dynamic Coriolis term and the relationship between U (t) and rotational angular velocity. Throughout our discussion, the technique of integration within an ordered product of operators is fully used, which has the advantage that the correspondence between the classical rotation and the quantum rotation is in a transparent fashion. A new angular-velocity formula is also derived.
Sharf Abdusalam M.
2014-03-01
Full Text Available In the oil and gas industries, understanding the behaviour of a flow through an annulus gap in a vertical position, whose outer wall is stationary whilst the inner wall rotates, is a significantly important issue in drilling wells. The main emphasis is placed on experimental (using an available rig and computational (employing CFD software investigations into the effects of the rotation speed of the inner pipe on the axial velocity profiles. The measured axial velocity profiles, in the cases of low axial flow, show that the axial velocity is influenced by the rotation speed of the inner pipe in the region of almost 33% of the annulus near the inner pipe, and influenced inversely in the rest of the annulus. The position of the maximum axial velocity is shifted from the centre to be nearer the inner pipe, by increasing the rotation speed. However, in the case of higher flow, as the rotation speed increases, the axial velocity is reduced and the position of the maximum axial velocity is skewed towards the centre of the annulus. There is a reduction of the swirl velocity corresponding to the rise of the volumetric flow rate.
Dufton, P L; Dunstall, P R; Evans, C J; Brott, I; de Mink, S E; Howarth, I D; Kennedy, M; McEvoy, C; Potter, A T; Ramírez-Agudelo, O H; Sana, H; Simón-Díaz, S; Taylor, W; Vink, J S
2012-01-01
Aims: Projected rotational velocities (\\vsini) have been estimated for 334 targets in the VLT-FLAMES Tarantula survey that do not manifest significant radial velocity variations and are not supergiants. They have spectral types from approximately O9.5 to B3. The estimates have been analysed to infer the underlying rotational velocity distribution, which is critical for understanding the evolution of massive stars. Methods: Projected rotational velocities were deduced from the Fourier transforms of spectral lines, with upper limits also being obtained from profile fitting. For the narrower lined stars, metal and non-diffuse helium lines were adopted, and for the broader lined stars, both non-diffuse and diffuse helium lines; the estimates obtained using the different sets of lines are in good agreement. The uncertainty in the mean estimates is typically 4% for most targets. The iterative deconvolution procedure of Lucy has been used to deduce the probability density distribution of the rotational velocities. R...
Lagrangian velocity auto-correlations in statistically-steady rotating turbulence
Del Castello, Lorenzo
2013-01-01
Lagrangian statistics of passive tracers in rotating turbulence is investigated by Particle Tracking Velocimetry. A confined and steadily-forced turbulent flow is subjected to five different rotation rates. The PDFs of the velocity components clearly reveal the anisotropy induced by background rotation. Although the statistical properties of the horizontal turbulent flow field are approximately isotropic, in agreement with previously reported results by van Bokhoven and coworkers [Phys. Fluids 21, 096601 (2009)], the velocity component parallel to the (vertical) rotation axis gets strongly reduced (compared to the horizontal ones) while the rotation is increased. The auto-correlation coefficients of all three components are progressively enhanced for increasing rotation rates, although the vertical one shows a tendency to decrease for slow rotation rates. The decorrelation is approximately exponential. Lagrangian data compare favourably with previously reported Eulerian data for horizontal velocity components...
Remote Evaluation of Rotational Velocity Using a Quadrant Photo-Detector and a DSC Algorithm.
Zeng, Xiangkai; Zhu, Zhixiong; Chen, Yang
2016-04-25
This paper presents an approach to remotely evaluate the rotational velocity of a measured object by using a quadrant photo-detector and a differential subtraction correlation (DSC) algorithm. The rotational velocity of a rotating object is determined by two temporal-delay numbers at the minima of two DSCs that are derived from the four output signals of the quadrant photo-detector, and the sign of the calculated rotational velocity directly represents the rotational direction. The DSC algorithm does not require any multiplication operations. Experimental calculations were performed to confirm the proposed evaluation method. The calculated rotational velocity, including its amplitude and direction, showed good agreement with the given one, which had an amplitude error of ~0.3%, and had over 1100 times the efficiency of the traditional cross-correlation method in the case of data number N > 4800. The confirmations have shown that the remote evaluation of rotational velocity can be done without any circular division disk, and that it has much fewer error sources, making it simple, accurate and effective for remotely evaluating rotational velocity.
Rotational velocities of single and binary O-type stars in the Tarantula Nebula
Ramírez-Agudelo, O H; de Koter, A; Simón-Díaz, S; de Mink, S E; Tramper, F; Dufton, P L; Evans, C J; Gräfener, G; Herrero, A; Langer, N; Lennon, D J; Apellániz, J Maíz; Markova, N; Najarro, F; Puls, J; Taylor, W D; Vink, J S
2014-01-01
Rotation is a key parameter in the evolution of massive stars, affecting their evolution, chemical yields, ionizing photon budget, and final fate. We determined the projected rotational velocity, $v_e\\sin i$, of $\\sim$330 O-type objects, i.e. $\\sim$210 spectroscopic single stars and $\\sim$110 primaries in binary systems, in the Tarantula nebula or 30 Doradus (30\\,Dor) region. The observations were taken using VLT/FLAMES and constitute the largest homogeneous dataset of multi-epoch spectroscopy of O-type stars currently available. The most distinctive feature of the $v_e\\sin i$ distributions of the presumed-single stars and primaries in 30 Dor is a low-velocity peak at around 100\\,$\\rm{km s^{-1}}$. Stellar winds are not expected to have spun-down the bulk of the stars significantly since their arrival on the main sequence and therefore the peak in the single star sample is likely to represent the outcome of the formation process. Whereas the spin distribution of presumed-single stars shows a well developed tai...
The relationship between trunk rotation, upper quarter dynamic stability and pitch velocity.
Bullock, Garrett S; Schmitt, Abigail C; Chasse, Patrick; Little, Barrett A; Diehl, Lee H; Butler, Robert J
2017-02-21
Understanding the relationship between upper quarter mobility, dynamic stability and pitching velocity may be beneficial in elucidating underlying factors that affect pitching performance. The purpose of this study was to investigate upper trunk rotation mobility and upper quarter dynamic stability and their correlation to pitch velocity in NCAA Division I collegiate pitchers. We hypothesized that collegiate pitchers with greater upper trunk rotation mobility and upper extremity dynamic stability would exhibit higher pitching velocity. Trunk rotation and the Upper Quarter Y-Balance Test (YBT-UQ) were measured utilizing standardized protocols. Collegiate pitchers (n=30) then proceeded to complete their team prescribed dynamic and throwing warm up followed by a pitching session from regulation distance at 100% effort. Each pitch was recorded for velocity and pitch type, only fastballs were utilized in analysis. The relationships between trunk rotation and fastball velocity, and YBT-UQ scores and fastball velocity were assessed using a series of two-tail Pearsons Correlations (p<.05). Throwing and non-throwing sides (69.6± 9.5 deg., 70.7± 9.4 deg.) had similar trunk rotation mobility. No statistically significant correlation between upper trunk rotation mobility and pitch velocity was found (throwing arm: r=.131, p<.491; non-throwing arm: r=.135, p<.478). There was also no correlation between the YBT-UQ and fastball velocity. In this study of Division I baseball pitchers, we found no relationship between trunk rotational mobility, upper quarter dynamic stability and pitching velocity. This suggests that increased upper extremity stability and trunk mobility are not directly related to fastball velocity. Understanding factors that associate to velocity may be helpful in predicting pitching performance.
Toure K. Augustin
2014-06-01
Full Text Available This paper studies a variant of an overhead crane model's problem, with a control force in velocity and rotating velocity on the platform. We obtain under certain conditions the well-posedness and the strong stabilization of the closed-loop system. We then analyze the spectrum of the system. Using a method due to Shkalikov, we prove the existence of a sequence of generalized eigenvectors of the system, which forms a Riesz basis for the state energy Hilbert space.
Modeling brain injury response for rotational velocities of varying directions and magnitudes.
Weaver, Ashley A; Danelson, Kerry A; Stitzel, Joel D
2012-09-01
An estimated 1.7 million people in the United States sustain a traumatic brain injury (TBI) annually. To investigate the effects of rotational motions on TBI risk and location, this study modeled rotational velocities of five magnitudes and 26 directions of rotation using the Simulated Injury Monitor finite element brain model. The volume fraction of the total brain exceeding a predetermined strain threshold, the Cumulative Strain Damage Measure (CSDM), was investigated to evaluate global model response. To evaluate regional response, this metric was computed relative to individual brain structures and termed the Structure Cumulative Strain Damage Measure (SCSDM). CSDM increased as input magnitude increased and varied with the direction of rotation. CSDM was 0.55-1.7 times larger in simulations with transverse plane rotation compared to those without transverse plane rotation. The largest SCSDM in the cerebrum and brainstem occurred with rotations in the transverse and sagittal planes, respectively. Velocities causing medial rotation of the cerebellum resulted in the largest SCSDM in this structure. For velocities of the same magnitude, injury risk calculated from CSDM varied from 0 to 97% with variations in the direction of rotation. These findings demonstrate injury risk, as estimated by CSDM and SCSDM, is affected by the direction of rotation and input magnitude, and these may be important considerations for injury prediction.
Pavlenko, Ya V; Jones, H R A; Ivanyuk, O; Pinfield, D J
2012-01-01
We describe our procedure to determine effective temperatures, rotational velocities, microturbulent velocities, and chemical abundances in the atmospheres of Sun-like stars. We use independent determinations of iron abundances using the fits to the observed Fe I and Fe II atomic absorption lines. We choose the best solution from the fits to these spectral features for the model atmosphere that provides the best confidence in the determined log N(Fe), Vt, and vsini. First, we compute the abundance of iron for a set of adopted microturbulent velocities. To determine the most self-consistent effective temperature and microturbulent velocity in any star's atmosphere, we used an additional constraint where we minimise the dependence of the derived abundances of Fe I and Fe II on the excitation potential of the corresponding lines. We analyse the spectra of the Sun and two well known solar type stars, HD1835 and HD10700 to determine their abundances, microturbulent velocity and rotational velocity. For the Sun abu...
Rosales-Guzmán, Carmelo; Belmonte, Aniceto; Torres, Juan P
2014-01-01
We measure the rotational and translational velocity components of particles moving in helical motion using the frequency shift they induced to the structured light beam illuminating them. Under Laguerre-Gaussian mode illumination, a particle with a helical motion reflects light that acquires an additional frequency shift proportional to the angular velocity of rotation in the transverse plane, on top of the usual frequency shift due to the longitudinal motion. We determined both the translational and rotational velocities of the particles by switching between two modes: by illuminating with a Gaussian beam, we can isolate the longitudinal frequency shift; and by using a Laguerre-Gaussian mode, the frequency shift due to the rotation can be determined. Our technique can be used to characterize the motility of microorganisms with a full three-dimensional movement.
Angular momentum projection of tilted axis rotating states
Oi, M.; Onishi, N.; Tajima, N. [Tokyo Univ. (Japan); Horibata, T.
1998-03-01
We applied an exact angular momentum projection to three dimensional cranked HFB (3d-CHFB) states. Tilted axis rotating states (TAR) and principal axis rotating states (PAR) are compared. It is shown that TAR is more adequate than PAR for description of the back bending phenomena driven by tilted rotation or wobbling motion. (author)
The rotational velocities evaluation for the engine mounts gyroscopic loads
Stefan BOGOS
2013-06-01
Full Text Available The default values for the maximum pitch and yaw speeds from CS 23.371, seem to be too conservative that would result in overstressing of the structure.A simplified dynamic simulation is proposed to evaluate more confident velocities for a specific aircraft. The yawing condition is related to the “sudden rudder deflection” and a maneuver with “lateral gust”. The pitching conditions are a result of a “sudden elevator deflection”. The model takes into account the nonlinear effects of the aerodynamic coefficients and controls efficiencies.
Measurement of preoperative and postoperative nasal tip projection and rotation.
Ingels, K.J.A.O.; Orhan, K.S.
2006-01-01
OBJECTIVE: To measure the effect of columellar struts and cephalic trim on tip projection and tip rotation using digitized photographs. METHODS: Using photographs of 62 patients who underwent external rhinoplasty, we retrospectively analyzed nasal tip projection (the Goode method) and rotation
Characterization of the radial velocity signal induced by rotation in late-type dwarfs
Suárez Mascareño, A.; Rebolo, R.; González Hernández, J. I.; Esposito, M.
2017-07-01
We investigate the activity-induced signals related to rotation and magnetic cycles in late-type stars (FGKM) and analyse the Ca II H&K, the H α and the radial velocity time series of 55 stars using the spectra from the HARPS public data base and the light curves provided by the All Sky Automated Survey. We search for short-term and long-term periodic signals in the time series of activity indicators as well as in the photometric light curves. Radial velocity data sets are then analysed to determine the presence of activity-induced signals. We measure a radial velocity signal induced by rotational modulation of stellar surface features in 37 stars, from late-F-type to mid-M-type stars. We report an empirical relationship, with some degree of spectral type dependency, between the mean level of chromospheric emission measured by the log _{10}(R^' }_{HK}) and the measured radial velocity semi-amplitude. We also report a relationship between the semi-amplitude of the chromospheric measured signal and the semi-amplitude of the radial velocity-induced signal, which strongly depends on the spectral type. We find that for a given strength of chromospheric activity (i.e. a given rotation period), M-type stars tend to induce larger rotation-related radial velocity signals than G- and K-type stars.
Warren, W. H., Jr.
1983-01-01
The machine-readable catalog provides mean data on the old Slettebak system for 6472 stars. The catalog results from the review, analysis and transformation of 11460 data from 102 sources. Star identification, (major catalog number, name if the star has one, or cluster identification, etc.), a man projected rotational velocity, and a list of source references re included. The references are given in a second file included with the catalog when it is distributed on magnetic tape. The contents and/formats of the the data and reference files of the machine-readable catalog are described to enable users to read and process the data.
Rotational velocities of low-mass stars in the Pleiades and Hyades
Terndrup, D M; Pinsonneault, M H; Sills, A; Yuan, Y; Jones, B F; Fischer, D; Krishnamurthi, A; Terndrup, Donald M.; Stauffer, John R.; Pinsonneault, Marc H.; Sills, Alison; Yuan, Yongquan; Jones, Burton F.; Fischer, Debra; Krishnamurthi, Anita
1999-01-01
We have obtained high-resolution spectra of 89 M dwarf members of the Pleiades and Hyades and have derived radial velocities, H-alpha equivalent widths, and spectroscopic rotational velocities for these stars. Typical masses of the newly-observed Pleiades and Hyades stars are ~ 0.4 M_{\\sun} and ~ 0.2 M_{\\sun}, respectively. We combine our new observations with previously published data to explore the rotational evolution of young stars with M < 0.4 M_\\sun. The average rotation rate in the Hyades (age 600 Myr) is about 0.4 that of the Pleiades (110 Myr), and the mean equivalent widths of H-alpha are also lower. As found in previous studies, the correlation between rotation and chromospheric activity is identical in both clusters, implying that the lower activity in the Hyades is a result of the lower rotation rates. We show that a simple scaling of the Pleiades rotational distribution for M \\leq 0.4 M_{\\sun}, corrected for the effects of structural evolution, matches that of the Hyades if the average angula...
Martinez-Arnaiz, R; Montes, D; Eiroa, C; Montesinos, B
2010-01-01
Context: Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles and their perturbations alter the line centroids creating a radial velocity jitter that might contaminate" the variations induced by a planet. Precise chromospheric activity measurements are needed to estimate the activity-induced noise that should be expected for a given star. Aims: We obtain precise chromospheric activity measurements and projected rotational velocities for nearby (d < 25 pc) cool (spectral types F to K) stars, to estimate their expected activity-related jitter. As a complementary objective, we attempt to obtain relationships between fluxes in different activity indicator lines, that permit a transformation of traditional activity indicators, i.e, CaII H & K lines, to others that hold noteworthy advanta...
Rotational Angles and Velocities During Down the Line and Diagonal Across Court Volleyball Spikes
Justin R. Brown
2014-05-01
Full Text Available The volleyball spike is an explosive movement that is frequently used to end a rally and earn a point. High velocity spikes are an important skill for a successful volleyball offense. Although the influence of vertical jump height and arm velocity on spiked ball velocity (SBV have been investigated, little is known about the relationship of shoulder and hip angular kinematics with SBV. Other sport skills, like the baseball pitch share similar movement patterns and suggest trunk rotation is important for such movements. The purpose of this study was to examine the relationship of both shoulder and hip angular kinematics with ball velocity during the volleyball spike. Methods: Fourteen Division I collegiate female volleyball players executed down the line (DL and diagonally across-court (DAC spikes in a laboratory setting to measure shoulder and hip angular kinematics and velocities. Each spike was analyzed using a 10 Camera Raptor-E Digital Real Time Camera System. Results: DL SBV was significantly greater than for DAC, respectively (17.54±2.35 vs. 15.97±2.36 m/s, p<0.05. The Shoulder Hip Separation Angle (S-HSA, Shoulder Angular Velocity (SAV, and Hip Angular Velocity (HAV were all significantly correlated with DAC SBV. S-HSA was the most significant predictor of DAC SBV as determined by regression analysis. Conclusions: This study provides support for a relationship between a greater S-HSA and SBV. Future research should continue to 1 examine the influence of core training exercise and rotational skill drills on SBV and 2 examine trunk angular velocities during various types of spikes during play.
Spiral Galaxies - classical description of spiral arms and rotational velocity pattern - toy model
Lobodzinski, Bogdan
2014-01-01
We propose an explanation of features of spiral galaxies: spiral arms and observed flat rotation curves, without the presence of an exotic form of matter. The formalism is based on Boltzmanns transport equation for the collisional matter and the very-low-velocity post-Newtonian approximation of the general relativity equations expressed in the Maxwell-like form. The Maxwell-like formulation provides the base for the explanation of the above phenomena in the language of dynamically created gravitoelectromagnetic fields by the movement of mass streams in the plane of the galaxy disc. In the model we use radical simplifications expressed as neglect of the gravitational interaction between neighbors and approximation of the incompressible mass flow. In this frame we show that if the galaxy is fuelled constantly by mass from an external gas reservoir, then the amplification of the gravitomagnetic field can be large enough to create the rotational velocity pattern and spiral arms without the necessity of introducin...
Flat rotation curves and low velocity dispersions in KMOS star-forming galaxies at z ~ 1
Di Teodoro, E. M.; Fraternali, F.; Miller, S. H.
2016-10-01
The study of the evolution of star-forming galaxies requires the determination of accurate kinematics and scaling relations out to high redshift. In this paper we select a sample of 18 galaxies at z ~ 1, observed in the Hα emission line with KMOS, to derive accurate kinematics using a novel 3D analysis technique. We use the new code 3DBarolo, which models the galaxy emission directly in 3D observational space, without the need to extract kinematic maps. This major advantage of this technique is that it is not affected by beam smearing and thus it enables the determination of rotation velocity and intrinsic velocity dispersion, even at low spatial resolution. We find that (1) the rotation curves of these z ~ 1 galaxies rise very steeply within few kiloparsecs and remain flat out to the outermost radius and (2) the Hα velocity dispersions are low, ranging from 15 to 40 km s-1, which leads to V/σ = 3-10. These characteristics are similar to those of disc galaxies in the local Universe. Finally, we also report no significant evolution of the stellar-mass Tully-Fisher relation. Our results show that disc galaxies are kinematically mature and rotation-dominated at z ~ 1 already. The reduced datacubes as FITS files are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/594/A77
Ito, Y.; Tanjyo, M.; Ohi, S.; Goto, S.; Ishimura, T.
1987-01-01
The ion rotational angular velocity ..cap omega.. and the ion temperature T/sub i/ of a translated field-reversed configuration (FRC) plasma are measured using neutral beam probe spectroscopy. The value of ..cap omega.. is --(1.0--1.2) x ..cap omega..* at the onset time of the n = 2 rotational instability, where ..cap omega..* is the ion diamagnetic frequency for a rigid-rotor equilibrium. The ion rotational direction is the same as the ion diamagnetic direction. The value of ..cap omega.. is smaller than the angular frequency ..omega../sub re/ of the n = 2 instability, which can yield experimental evidence of the ion kinetic effects on the n = 2 instability in the FRC plasma. When the octupole field is applied to the plasma in order to suppress the n = 2 deformation, ..cap omega.. is slightly reduced. The ion temperature T/sub i/ is --70 eV at the onset time of the n = 2 instability.
Estimation of Rotational Velocity of Baseball Using High-Speed Camera Movies
Inoue, Takuya; Uematsu, Yuko; Saito, Hideo
Movies can be used to analyze a player's performance and improve his/her skills. In the case of baseball, the pitching is recorded by using a high-speed camera, and the recorded images are used to improve the pitching skills of the players. In this paper, we present a method for estimating of the rotational velocity of a baseball on the basis of movies recorded by high-speed cameras. Unlike in the previous methods, we consider the original seam pattern of the ball seen in the input movie and identify the corresponding image from a database of images by adopting the parametric eigenspace method. These database images are CG Images. The ball's posture can be determined on the basis of the rotational parameters. In the proposed method, the symmetric property of the ball is also taken into consideration, and the time continuity is used to determine the ball's posture. In the experiments, we use the proposed method to estimate the rotational velocity of a baseball on the basis of real movies and movies consisting of CG images of the baseball. The results of both the experiments prove that our method can be used to estimate the ball's rotation accurately.
Velocity dependence of rotational loss in Evershed-type superconducting bearings
Hull, John R.; Mulcahy, Thomas M.; Labataille, Joseph F.
1997-02-01
Results of free spin down in vacuum are reported for an Evershed-type superconducting bearing in which a permanent magnet (PM) ring is levitated over an array of high-temperature superconductors (HTSs) and under a similar PM ring in magnetic attraction. The velocity dependence of the rotational loss strongly suggests that the observed velocity-dependent losses are primarily due to eddy currents induced in the PM by inhomogeneity of the field produced by the magnetized HTS array. The results show that the Evershed-type bearing is capable of reducing these eddy-current losses to an extremely low level, so that at a maximum magnet rim velocity of 28 m/s, the fractional kinetic-energy loss per hour was 2.4×10-4. Significant levitation heights are also possible, and at a 23 mm height, we measured a low-speed coefficient of friction of 3×10-8.
Girishwar Nath
1970-10-01
Full Text Available A closed form solution of the Navier-Stokes equations has been obtained in the case of steady axisymmetric flow of an incompressible electrically conducting viscous fluid between two concentric rotating cylinders composed of an insulating material under the influence of radial magnetic field. It has been found that the velocity components are less than those of the classical hydrodynamic case. In the presence of the magnetic field, the tangential velocity becomes fully developed in a smaller axial distance than in the absence of the magnetic field. For small Reynolds number, the fully developed tangential velocity is achieved in a small axial distance, but it requires greater axial distance for large Reynolds number.
Jørgensen, L. W.; Sillesen, Alfred Hegaard
1979-01-01
The Doppler-broadened profile of the He II 4685.75 AA line was measured along a chord in a rotating plasma, transverse to the magnetic field. Using a single-particle orbit picture, the corresponding velocity spectrum of ions confirm the measurements, so it can be concluded that the single......-particle orbit picture is valid for the discharge period under investigation, except for the first few microseconds during breakdown when a strong interaction between plasma and remaining neutral gas takes place by Alfvens critical velocity mechanism. A simple relation is given between the measured half......-width and shift of the Doppler profile and the macroscopic quantities of ion velocity and energy. Several Doppler-broadened profiles are shown for different plasma parameters....
Hess, B. J.; Angelaki, D. E.
1997-01-01
The spatial organization of fast phase velocity vectors of the vestibulo-ocular reflex (VOR) was studied in rhesus monkeys during yaw rotations about an earth-horizontal axis that changed continuously the orientation of the head relative to gravity ("barbecue spit" rotation). In addition to a velocity component parallel to the rotation axis, fast phases also exhibited a velocity component that invariably was oriented along the momentary direction of gravity. As the head rotated through supine and prone positions, torsional components of fast phase velocity axes became prominent. Similarly, as the head rotated through left and right ear-down positions, fast phase velocity axes exhibited prominent vertical components. The larger the speed of head rotation the greater the magnitude of this fast phase component, which was collinear with gravity. The main sequence properties of VOR fast phases were independent of head position. However, peak amplitude as well as peak velocity of fast phases were both modulated as a function of head orientation, exhibiting a minimum in prone position. The results suggest that the fast phases of vestibulo-ocular reflexes not only redirect gaze and reposition the eye in the direction of head motion but also reorient the eye with respect to earth-vertical when the head moves relative to gravity. As further elaborated in the companion paper, the underlying mechanism could be described as a dynamic, gravity-dependent modulation of the coordinates of ocular rotations relative to the head.
Determining a rotation of a tetrahedron from a projection
Gardner, Richard J; Theobald, Thorsten
2011-01-01
The following problem, arising from medical imaging, is addressed: Suppose that $T$ is a known tetrahedron in $\\R^3$ with centroid at the origin. Also known is the orthogonal projection $U$ of the vertices of the image $\\phi T$ of $T$ under an unknown rotation $\\phi$ about the origin. Under what circumstances can $\\phi$ be determined from $T$ and $U$?
Hansen, Flemming Yssing; Taub, H.
2009-01-01
The motion of the atoms in a molecule may be described as a superposition of translational motion of the molecular center-of-mass, rotational motion about the principal molecular axes, and an intramolecular motion that may be associated with vibrations and librations as well as molecular conforma......The motion of the atoms in a molecule may be described as a superposition of translational motion of the molecular center-of-mass, rotational motion about the principal molecular axes, and an intramolecular motion that may be associated with vibrations and librations as well as molecular...... conformational changes. We have constructed projection operators that use the atomic coordinates and velocities at any two times, t=0 and a later time t, to determine the molecular center-of-mass, rotational, and intramolecular motions in a molecular dynamics simulation. This model-independent technique...
Order reduction in time integration caused by velocity projection
Arnold, Martion [Martin Luther University, Halle (Germany); Cardona, Alberto [Universdad Nacional Lioral, Santa Fe (Argentina); Bruls, Olivier [University of Liege, Liège (Belgium)
2015-07-15
Holonomic constraints restrict the configuration of a multibody system to a subset of the configuration space. They imply so called hidden constraints at the level of velocity coordinates as well as the original constraint equations may be obtained considering both types of constraints as well as the original constraint equations may be obtained considering both types of constraints in each time step (Stabilized index-2 formulation) or using projection techniques. Both approaches are well established in the time integration of differential-algebraic equations. Recently, we have introduced a generalized-α Lie group time integration method for the stablilized index -2 formulation that achieves second order convergence for all solution components In the present paper, we show that a separate velocity projection would be less favourable since it may result in an order reduction and in large transient errors after each projection step. This undesired numerical behaviour is analysed by a one-step error recursion that considers the coupled error propagation in differential and algebraic solution components. This one-step error recursion has been used before to prove second order convergence for the application of generalized-α methods to constrained systems.
Wu, Bin; Fang, Ling-hui; Chen, Xiao-lei; Zou, Zhi-qiang; Yu, Xu-hua; Chen, Gang
2014-02-01
The necessity of finding new rotating band materials and developing corresponding joining technologies for large-caliber projectiles has been revealed by the recent increase in the ballistic performance of high loads. In this paper, aluminum bronze coatings were fabricated by the high velocity arc spraying (HVAS) technique. Microstructure and microhardness of the prepared coatings were investigated. Ring-on-disk dry sliding wear tests were conducted in an ambient condition to examine the tribological behavior of the coatings. Quasi-static engraving processes of rotating bands made of as-sprayed aluminum bronze coating and bulk copper were studied using rate-controlled push test methodology on an MTS 810 Material Testing System. The results show that the as-sprayed aluminum bronze coatings have a dense microstructure with porosity of about 1.6%. Meanwhile, the as-sprayed coating presents a higher microhardness than pure copper. The friction coefficient of coatings is about 0.2-0.3 in the steady state. Tribological mechanisms of the as-sprayed coatings were discussed. The engraving test results show that the aluminum bronze rotating band presents high bonding strength and good plasticity. The HVAS aluminum bronze coating should be a possible substitute for the state-of-the-art copper rotating band.
Projected Future Climate Analogues and Climate "Velocities" in North America
Shafer, S. L.; Bartlein, P. J.
2014-12-01
Future climate changes may have significant effects on many North American ecosystems. One way of assessing the potential impacts of future climate change is to use future climate analogues of present climate to evaluate the spatial extent and rates of future climate change. We used a set of Coupled Model Intercomparison Project phase 5 (CMIP5) coupled atmosphere-ocean general circulation model (AOGCM) future climate simulations (2006-2100) produced under representative concentration pathway scenario RCP8.5. We regridded these data to a 10-km equal-area grid of North America. Modern climate data (1961-1990 30-year mean) were interpolated to the same 10-km grid. The projected future climate data were analyzed using 10-year mean values of monthly and seasonal temperature and precipitation and a set of derived annual bioclimatic variables (e.g., growing degree days) considered to be ecologically significant. Potential future climate analogues were calculated for each grid cell using Euclidean distances to identify similar climates occurring elsewhere in North America. We identify regions that are projected to retain climates similar to present in the future (e.g., parts of the southeastern United States) and regions where present climates are projected to become less common or to disappear in the future (e.g., high elevation sites in western North America). We also calculate the rates of change in locations of similar climates (i.e., climate analogue velocities) and compare our results with simulated paleoclimate velocities over the past 22 kyr (from TraCE-21ka transient climate simulations for 22 ka-present). We discuss the implications of these results for conservation and natural resource management in North America. We also describe a web application being developed to allow researchers, decision makers, and members of the public, to visualize, explore, and use the climate analogue data.
Effect of Head Rotation on Cerebral Blood Velocity in the Prone Position
Højlund, Jakob; Sandmand, Marie; Sonne, Morten; Mantoni, Teit; Jørgensen, Henrik L.; Belhage, Bo; van Lieshout, Johannes J.; Pott, Frank C.
2012-01-01
Background. The prone position is applied to facilitate surgery of the back and to improve oxygenation in the respirator-treated patient. In particular, with positive pressure ventilation the prone position reduces venous return to the heart and in turn cardiac output (CO) with consequences for cerebral blood flow. We tested in healthy subjects the hypothesis that rotating the head in the prone position reduces cerebral blood flow. Methods. Mean arterial blood pressure (MAP), stroke volume (SV), and CO were determined, together with the middle cerebral artery mean blood velocity (MCA Vmean) and jugular vein diameters bilaterally in 22 healthy subjects in the prone position with the head centered, respectively, rotated sideways, with and without positive pressure breathing (10 cmH2O). Results. The prone position reduced SV (by 5.4 ± 1.5%; P < 0.05) and CO (by 2.3 ± 1.9 %), and slightly increased MAP (from 78 ± 3 to 80 ± 2 mmHg) as well as bilateral jugular vein diameters, leaving MCA Vmean unchanged. Positive pressure breathing in the prone position increased MAP (by 3.6 ± 0.8 mmHg) but further reduced SV and CO (by 9.3 ± 1.3 % and 7.2 ± 2.4 % below baseline) while MCA Vmean was maintained. The head-rotated prone position with positive pressure breathing augmented MAP further (87 ± 2 mmHg) but not CO, narrowed both jugular vein diameters, and reduced MCA Vmean (by 8.6 ± 3.2 %). Conclusion. During positive pressure breathing the prone position with sideways rotated head reduces MCA Vmean ~10% in spite of an elevated MAP. Prone positioning with rotated head affects both CBF and cerebrovenous drainage indicating that optimal brain perfusion requires head centering. PMID:22988456
The characteristics of the ion temperature and toroidal rotation velocity in the KSTAR plasma
Ko, Won Ha; Lee, Hyung Ho; Oh, Seung Tae [National Fusion Research Institute, Daejeon (Korea, Republic of)
2012-05-15
Charge exchange spectroscopy (CES) is one of the important diagnostics on the Korea Superconducting Tokamak Advanced Research (KSTAR) to get ion temperature and toroidal rotation velocity. We describe the current status and the improvements made over the last two years. The current system upgraded from a Czerny-Turner spectrometer consists of two spectroscopic systems looking at the KSTAR neutral beam which is modulated 5 Hz for special period. One system has a DS spectrometer (f/2.8) lent from NIFS with pitch-controlled double slit fiber bundle with back- illuminated CCD and the other system has Kspectrometer (F/2.0) made by NFRI with intensified CCD. The K-spectrometer has a grating number of 2400 g/mm, focal length of 200 mm. The upgrade of two high throughput spectrometers enables to improve the time resolution from 200 msec to around 10 msec. This article focuses on improved edge spatial interval from increasing of plasma viewing channels to 5 mm and enhanced time resolution from a high throughput spectrometer with back-illuminated CCD. The upgrade has allowed to measure pedestal ion temperature and toroidal rotation velocity profiles in KSTAR H-mode
Zorec, J.; Frémat, Y.; Domiciano de Souza, A.; Royer, F.; Cidale, L.; Hubert, A.-M.; Semaan, T.; Martayan, C.; Cochetti, Y. R.; Arias, M. L.; Aidelman, Y.; Stee, P.
2016-11-01
Context. Among intermediate-mass and massive stars, Be stars are the fastest rotators in the main sequence (MS) and, as such, these stars are a cornerstone to validate models of structure and evolution of rotating stars. Several phenomena, however, induce under- or overestimations either of their apparent Vsini, or true velocity V. Aims: In the present contribution we aim at obtaining distributions of true rotational velocities corrected for systematic effects induced by the rapid rotation itself, macroturbulent velocities, and binarity. Methods: We study a set of 233 Be stars by assuming they have inclination angles distributed at random. We critically discuss the methods of Cranmer and Lucy-Richardson, which enable us to transform a distribution of projected velocities into another distribution of true rotational velocities, where the gravitational darkening effect on the Vsini parameter is considered in different ways. We conclude that iterative algorithm by Lucy-Richardson responds at best to the purposes of the present work, but it requires a thorough determination of the stellar fundamental parameters. Results: We conclude that once the mode of ratios of the true velocities of Be stars attains the value V/Vc ≃ 0.77 in the main-sequence (MS) evolutionary phase, it remains unchanged up to the end of the MS lifespan. The statistical corrections found on the distribution of ratios V/Vc for overestimations of Vsini, due to macroturbulent motions and binarity, produce a shift of this distribution toward lower values of V/Vc when Be stars in all MS evolutionary stages are considered together. The mode of the final distribution obtained is at V/Vc ≃ 0.65. This distribution has a nearly symmetric distribution and shows that the Be phenomenon is characterized by a wide range of true velocity ratios 0.3 ≲ V/Vc ≲ 0.95. It thus suggests that the probability that Be stars are critical rotators is extremely low. Conclusions: The corrections attempted in the present
Fast Rotation Search with Stereographic Projections for 3D Registration.
Parra Bustos, Alvaro; Chin, Tat-Jun; Eriksson, Anders; Li, Hongdong; Suter, David
2016-11-01
Registering two 3D point clouds involves estimating the rigid transform that brings the two point clouds into alignment. Recently there has been a surge of interest in using branch-and-bound (BnB) optimisation for point cloud registration. While BnB guarantees globally optimal solutions, it is usually too slow to be practical. A fundamental source of difficulty lies in the search for the rotational parameters. In this work, first by assuming that the translation is known, we focus on constructing a fast rotation search algorithm. With respect to an inherently robust geometric matching criterion, we propose a novel bounding function for BnB that is provably tighter than previously proposed bounds. Further, we also propose a fast algorithm to evaluate our bounding function. Our idea is based on using stereographic projections to precompute and index all possible point matches in spatial R-trees for rapid evaluations. The result is a fast and globally optimal rotation search algorithm. To conduct full 3D registration, we co-optimise the translation by embedding our rotation search kernel in a nested BnB algorithm. Since the inner rotation search is very efficient, the overall 6DOF optimisation is speeded up significantly without losing global optimality. On various challenging point clouds, including those taken out of lab settings, our approach demonstrates superior efficiency.
Velocity storage in the human vertical rotational vestibulo-ocular reflex.
Bertolini, G; Ramat, S
2011-03-01
Human horizontal rotational vestibulo-ocular reflex (rVOR) has been extensively investigated: the horizontal semicircular canals sense yaw rotations with high-pass filter dynamics and a time constant (TC) around 5 s, yet the rVOR response shows a longer TC due to a central processing stage, known as velocity storage mechanism (VSM). It is generally assumed that the vertical rVOR behaves similarly to the horizontal one; however, VSM processing of the human vertical rVOR is still to be proven. We investigated the vertical rVOR in eight healthy human subjects using three experimental paradigms: (1) per- and post-rotatory around an earth-vertical axis (ear down rotations, EDR), (2) post-rotatory around an earth-horizontal axis with different stopping positions (static otolith stimulation), (3) per-rotatory around an earth-horizontal axis (dynamic otolith stimulation). We found that the TC of vertical rVOR responses ranged 3-10 s, depending both on gravity and on the direction of rotation. The shortest TC were found in response to post-rotatory earth-horizontal stimulation averaging 3.6 s, while they were prolonged in EDR stimulation, i.e. when the head angular velocity vector is aligned with gravity, with a mean value of about 6.0 s. Overall, the longest TC were observed in per-rotatory earth-horizontal stimulation, averaging 7.8 s. The finding of longer TC in EDR than in post-rotatory earth-horizontal stimulation indicates a role for the VSM in the vertical rVOR, although its contribution appears to be weaker than on the horizontal rVOR and may be directionally asymmetric. The results from per-rotatory earth-horizontal stimulation, instead, imply a role for the otoliths in controlling the duration of the vertical rVOR response. We found no reorientation of the response toward earth horizontal, indicating a difference between human and monkey rVOR.
Liu, Chunfang; Hayakawa, Yoshikazu; Nakashima, Akira
This paper proposes an on-line method for estimating both translational and rotational velocities of a table tennis ball by using only a few consecutive frames of image data which are sensed by two high speed cameras. In order to estimate the translational velocity, three-dimensional (3D) position of the ball's center at each instant of camera frame is obtained, where the on-line method of reconstructing the 3D position from the two-dimensional (2D) image data of two cameras is proposed without the pattern matching process. The proposed method of estimating the rotational velocity belongs to the image registration methods, where in order to avoid the pattern matching process too, a rotation model of the ball is used to make an estimated image data from an image data sensed at the previous instant of camera frame and then the estimated image data are compared with the image data sensed at the next instant of camera frame to obtain the most plausible rotational velocity by using the least square and the conjugate gradient method. The effectiveness of the proposed method is shown by some experimental results in the case of a ball rotated by a rotation machine as well as in the case of a flying ball shot from a catapult machine.
Effect of head rotation on cerebral blood velocity in the prone position
Højlund, Jakob; Sandmand, Marie; Sonne, Morten
2012-01-01
for cerebral blood flow. We tested in healthy subjects the hypothesis that rotating the head in the prone position reduces cerebral blood flow. Methods. Mean arterial blood pressure (MAP), stroke volume (SV), and CO were determined, together with the middle cerebral artery mean blood velocity (MCA V......(mean)) and jugular vein diameters bilaterally in 22 healthy subjects in the prone position with the head centered, respectively, rotated sideways, with and without positive pressure breathing (10 cmH(2)O). Results. The prone position reduced SV (by 5.4 ± 1.5%; P ... MAP (from 78 ± 3 to 80 ± 2 mmHg) as well as bilateral jugular vein diameters, leaving MCA V(mean) unchanged. Positive pressure breathing in the prone position increased MAP (by 3.6 ± 0.8 mmHg) but further reduced SV and CO (by 9.3 ± 1.3 % and 7.2 ± 2.4 % below baseline) while MCA V...
Normal A0--A1 stars with low rotational velocities. I. Abundance determination and classification
Royer, F; Monier, R; Adelman, S; Smalley, B; Pintado, O; Reiners, A; Hill, G; Gulliver, A
2014-01-01
Context. The study of rotational velocity distributions for normal stars requires an accurate spectral characterization of the objects in order to avoid polluting the results with undetected binary or peculiar stars. This piece of information is a key issue in the understanding of the link between rotation and the presence of chemical peculiarities. Aims. A sample of 47 low v sin i A0-A1 stars (v sin i < 65km/s), initially selected as main-sequence normal stars, are investigated with high-resolution and high signal-to-noise spectroscopic data. The aim is to detect spectroscopic binaries and chemically peculiar stars, and eventually establish a list of confirmed normal stars. Methods. A detailed abundance analysis and spectral synthesis is performed to derive abundances for 14 chemical species. A hierarchical classification, taking measurement errors into account, is applied to the abundance space and splits the sample into two different groups, identified as the chemically peculiar stars and the normal sta...
A possible explanation of Galactic Velocity Rotation Curves in terms of a Cosmological Constant
Whitehouse, S B; Whitehouse, Steven B.; Kraniotis, George V.
1999-01-01
This paper describes how the non-gravitational contribution to galactic velo city rotation curves can be explained in terms of a Cosmological Constant ($\\Lambda$).The velocity rotation curve for the nearby galaxy M33 will be analysed in detail while several other galaxies will be superficially studied. It will be shown that the Cosmological Constant leads to a contribution to the acceleration proportional to the radii, at large radii, and depending on the mass of the galaxy. It was found to dominate at approximately 13Kpc for M33. The Cosmological Constant experimentally derived from the M33 data was found to be:$\\Lambda_{Exp}=1.33\\times 10^{-52} cm^{-2}$, which compares favourably with the theoretical value of $\\Lambda_{Theory}=0.91\\times 10^{-54}cm^{-2}$. It will be shown that the Cosmological Constant, in the Weak Field Approximation, leads to a correction term for the Newtonian potential and the corresponding acceleration of a test particle. The extended LNH will then be used to define other cosmological ...
Projection of the rotation form Navier-Stokes equation onto the half-staggered grid
Cho, Ji Ryong [Inje University, Kimhae (Korea, Republic of)
2016-07-15
A projection method for computing incompressible fluid flow is proposed. For the method, the rotation form Navier-Stokes equation (NSE), for which the velocity and the total pressure are employed, is discretized on the half-staggered, finite difference spatial grid. The total pressure couples the static pressure gradient and the convection of momentum in the continuous NSE while the half-staggered grid provides weak pressure-velocity coupling in discrete space. These two features interact synergistically for the discretized NSE to produce smooth pressure fields without additional numerical artifacts such as the momentum interpolation. The method preserves the kinetic energy at the inviscid limit condition. Numerical solutions of the decaying Taylor vortex, the inviscid Taylor vortex, the sudden expansion channel and the square-prism wake are presented.
Multi-view autostereoscopic projection display using rotating screen.
Eldes, Osman; Akşit, Kaan; Urey, Hakan
2013-11-18
A new technique for multi-view autostereoscopic projection display is proposed, and demonstrated. The technique uses two mobile projectors, a rotating retro-reflective diffuser screen, and a head-tracking camera. As two dynamic viewing slits are created at the viewer's position, the slits can track the position of the eyes by rotating the screen. The display allows a viewer to move approximately 700 mm along the horizontal axis, and 500 mm along the vertical axis with an average crosstalk below 5 %. Two screen prototypes with different diffusers have been tried, and they provide luminance levels of 60 Cd/m2, and 160 Cd/m2 within the viewing field.
All-optical animation projection system with rotating fieldstone
Ishii, Yuko; Takayama, Yoshihisa; Kodate, Kashiko
2007-06-01
A simple and compact rewritable holographic memory system using a fieldstone of Ulexite is proposed. The role of the fieldstone is to impose random patterns on the reference beam to record plural images with the random-reference multiplexing scheme. The operations for writing and reading holograms are carried out by simply rotating the fieldstone in one direction. One of the features of this approach is found in a way to generate random patterns without computer drawings. The experimental study confirms that our system enables the smooth readout of the stored images one after another so that the series of reproduced images are projected as an animation.
Rotational and radial velocities of 1.3-2.2 M {sub ☉} red giants in open clusters
Carlberg, Joleen K., E-mail: jcarlberg@dtm.ciw.edu [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015 (United States)
2014-06-01
This study presents the rotational distribution of red giant (RG) stars in 11 old to intermediate age open clusters. The masses of these stars are all above the Kraft break, so they lose negligible amounts of their birth angular momentum (AM) during the main-sequence (MS) evolution. However, they do span a mass range with quite different AM distributions imparted during formation, with the stars less massive than ∼1.6M {sub ☉} arriving on the MS with lower rotation rates than the more massive stars. The majority of RGs in this study are slow rotators across the entire red giant branch regardless of mass, supporting the picture that intermediate-mass stars rapidly spin down when they evolve off the MS and develop convection zones capable of driving a magnetic dynamo. Nevertheless, a small fraction of RGs in open clusters show some level of enhanced rotation, and faster rotators are as common in these clusters as in the field RG population. Most of these enhanced rotators appear to be red clump stars, which is also true of the underlying stellar sample, while others are clearly RGs that are above or below the clump. In addition to rotational velocities, the radial velocities (RVs) and membership probabilities of individual stars are also presented. Cluster heliocentric RVs for NGC 6005 and Pismis 18 are reported for the first time.
Yin, Chenguang; Zheng, Liancun [Univ. of Science and Technology Beijing (China). School of Mathematics and Physics; Zhang, Chaoli [Univ. of Science and Technology Beijing (China). School of Mathematics and Physics; Univ. of Science and Technology Beijing (China). School of Mechanical Engineering; Zhang, Xinxin [Univ. of Science and Technology Beijing (China). School of Mechanical Engineering
2015-09-01
In this article, we discuss the flow and heat transfer of nanofluids over a rotating porous disk with velocity slip and temperature jump. Three types of nanoparticles - Cu, Al{sub 2}O{sub 3}, and CuO - are considered with water as the base fluid. The nonlinear governing equations are reduced into ordinary differential equations by Von Karman transformations and solved using homotopy analysis method (HAM), which is verified in good agreement with numerical ones. The effects of involved parameters such as porous parameter, velocity slip, temperature jump, as well as the types of nanofluids on velocity and temperature fields are presented graphically and analysed.
Multi Point Velocity, Density and Temperature Measurements using LITA Project
National Aeronautics and Space Administration — Laser induced thermal acoustics (LITA) is a nonintrusive, transient-grating optical technique that provides simultaneous high-accuracy measurements of velocity,...
Procrustes rotation as a diagnostic tool for projection pursuit analysis.
Wentzell, Peter D; Hou, Siyuan; Silva, Carolina Santos; Wicks, Chelsi C; Pimentel, Maria Fernanda
2015-06-02
Projection pursuit (PP) is an effective exploratory data analysis tool because it optimizes the projection of high dimensional data using distributional characteristics rather than variance or distance metrics. The recent development of fast and simple PP algorithms based on minimization of kurtosis for clustering data has made this powerful tool more accessible, but under conditions where the sample-to-variable ratio is small, PP fails due to opportunistic overfitting of random correlations to limiting distributional targets. Therefore, some kind of variable compression or data regularization is required in these cases. However, this introduces an additional parameter whose optimization is manually time consuming and subject to bias. The present work describes the use of Procrustes analysis as diagnostic tool that can be used to evaluate the results of PP analysis in an efficient manner. Through Procrustes rotation, the similarity of different PP projections can be examined in an automated fashion with "Procrustes maps" to establish regions of stable projections as a function of the parameter to be optimized. The application of this diagnostic is demonstrated using principal components analysis to compress FTIR spectra from ink samples of ten different brands of pen, and also in conjunction with regularized PP for soybean disease classification. Copyright © 2015 Elsevier B.V. All rights reserved.
A dynamo model of magnetic activity in solar-like stars with different rotational velocities
Karak, Bidya Binay; Leonid L. Kitchatinov; Choudhuri, Arnab Rai
2014-01-01
We attempt to provide a quantitative theoretical explanation for the observations that Ca II H/K emission and X-ray emission from solar-like stars increase with decreasing Rossby number (i.e., with faster rotation). Assuming that these emissions are caused by magnetic cycles similar to the sunspot cycle, we construct flux transport dynamo models of $1M_{\\odot}$ stars rotating with different rotation periods. We first compute the differential rotation and the meridional circulation inside thes...
Simultaneous Temperature and Velocity Diagnostic for Reacting Flows Project
National Aeronautics and Space Administration — A diagnostic technique is proposed for measuring temperature and velocity simultaneously in a high temperature reacting flow for aiding research in propulsion. The...
Hyper Velocity Impact - Damage Assessment System (HVI-DAS) Project
National Aeronautics and Space Administration — A device is proposed that can track the electrical charge dispersion that is created when hyper velocity impact (HVI) occurs between two entities with a closing...
Groh, Jose H; Hillier, D John; Barba, Rodolfo; Fernandez-Lajus, Eduardo; Gamen, Roberto C; Moises, Alessandro; Solivella, Gladys; Teodoro, Mairan
2009-01-01
We report optical observations of the Luminous Blue Variable (LBV) HR Carinae which show that the star has reached a visual minimum phase in 2009. More importantly, we detected absorptions due to Si IV 4088-4116 Angstroms. To match their observed line profiles from 2009 May, a high rotational velocity of vrot=150 +- 20 km/s is needed (assuming an inclination angle of 30 degrees), implying that HR Car rotates at ~0.88 +- 0.2 of its critical velocity for break-up (vcrit). Our results suggest that fast rotation is typical in all strong-variable, bona-fide galactic LBVs, which present S Dor-type variability. Strong-variable LBVs are located in a well-defined region of the HR diagram during visual minimum (the "LBV minimum instability strip"). We suggest this region corresponds to where vcrit is reached. To the left of this strip, a forbidden zone with vrot/vcrit>1 is present, explaining why no LBVs are detected in this zone. Since dormant/ex LBVs like P Cygni and HD 168625 have low vrot, we propose that LBVs can ...
Effect of Head Rotation on Cerebral Blood Velocity in the Prone Position
Jakob Højlund
2012-01-01
%. Conclusion. During positive pressure breathing the prone position with sideways rotated head reduces MCA Vmean ~10% in spite of an elevated MAP. Prone positioning with rotated head affects both CBF and cerebrovenous drainage indicating that optimal brain perfusion requires head centering.
Sadeghi, Jafar
2015-01-01
In order to study quark and anti-quark interaction, one should consider all effects of the medium in motion of the pair. Because the pair, is not produced at rest in QGP. So the velocity of the pair, has some effects on its interactions that should be taken into account. In this paper we apply some conformal transformations for a rotat- ing string dual to a rotating heavy quark in $AdS_3$ which construct an accelerating string dual to an accelerating quark and anti-quark pair. So, we can have a comparison between when pair has angular velocity or not. Then we can study effects of angular velocity on the accelerating quark and anti-quark which are constructed by performing special con- formal transformations, conformal SO(2,2) transformation and particular $SL(2;R)_L$ and $SL(2;R)_R$ transformation. The accelerating quark and anti-quark show different behavior with increasing in angular velocity. With useful numerical solutions we show that quark and anti-quark can deccelerate to achieve each other or accelera...
Computation of fragment velocities and projection angles of an anti-aircraft round
Snyman, IM
2014-09-01
Full Text Available This paper presents the calculation of the terminal ballistic signature of the 35 mm HEI from two viewpoints. The first viewpoint calculates fragment velocities and projection angles by the axial symmetric hydro code ANSYS AUTODYN. The second...
Bizyaev, D.; Walterbos, R. A. M.; Yoachim, P.; Riffel, R. A.; Fernández-Trincado, J. G.; Pan, K.; Diamond-Stanic, A. M.; Jones, A.; Thomas, D.; Cleary, J.; Brinkmann, J.
2017-04-01
We present a study of the kinematics of the extraplanar ionized gas around several dozen galaxies observed by the Mapping of Nearby Galaxies at the Apache Point Observatory (MaNGA) survey. We considered a sample of 67 edge-on galaxies out of more than 1400 extragalactic targets observed by MaNGA, in which we found 25 galaxies (or 37%) with regular lagging of the rotation curve at large distances from the galactic midplane. We model the observed Hα emission velocity fields in the galaxies, taking projection effects and a simple model for the dust extinction into account. We show that the vertical lag of the rotation curve is necessary in the modeling, and estimate the lag amplitude in the galaxies. We find no correlation between the lag and the star formation rate in the galaxies. At the same time, we report a correlation between the lag and the galactic stellar mass, central stellar velocity dispersion, and axial ratio of the light distribution. These correlations suggest a possible higher ratio of infalling-to-local gas in early-type disk galaxies or a connection between lags and the possible presence of hot gaseous halos, which may be more prevalent in more massive galaxies. These results again demonstrate that observations of extraplanar gas can serve as a potential probe for accretion of gas.
Understanding sprint velocity fluctuations for improved project plans with Scrum: a case study
Albero, Filipe; Calvo-Manzano Villalón, José Antonio; Caballero, Edgar; Arcilla, Magdalena
2014-01-01
Starting from the documentation of high sprint velocity fluctuations in a Scrum project, this paper presents a thorough approach to identify the sources of issues arising in the context of Scrum implementation. Given that Scrum provides guidance on identifying process issues but not their root causes, various approaches are explored. This is of great relevance because Scrum defines project schedules relying heavily on sprint velocity and because it is the most widely used agile methodology. T...
Las Vegas Basin Seismic Response Project: Measured Shallow Soil Velocities
Luke, B. A.; Louie, J.; Beeston, H. E.; Skidmore, V.; Concha, A.
2002-12-01
The Las Vegas valley in Nevada is a deep (up to 5 km) alluvial basin filled with interlayered gravels, sands, and clays. The climate is arid. The water table ranges from a few meters to many tens of meters deep. Laterally extensive thin carbonate-cemented lenses are commonly found across parts of the valley. Lenses range beyond 2 m in thickness, and occur at depths exceeding 200 m. Shallow seismic datasets have been collected at approximately ten sites around the Las Vegas valley, to characterize shear and compression wave velocities in the near surface. Purposes for the surveys include modeling of ground response to dynamic loads, both natural and manmade, quantification of soil stiffness to aid structural foundation design, and non-intrusive materials identification. Borehole-based measurement techniques used include downhole and crosshole, to depths exceeding 100 m. Surface-based techniques used include refraction and three different methods involving inversion of surface-wave dispersion datasets. This latter group includes two active-source techniques, the Spectral Analysis of Surface Waves (SASW) method and the Multi-Channel Analysis of Surface Waves (MASW) method; and a new passive-source technique, the Refraction Mictrotremor (ReMi) method. Depths to halfspace for the active-source measurements ranged beyond 50 m. The passive-source method constrains shear wave velocities to 100 m depths. As expected, the stiff cemented layers profoundly affect local velocity gradients. Scale effects are evident in comparisons of (1) very local measurements typified by borehole methods, to (2) the broader coverage of the SASW and MASW measurements, to (3) the still broader and deeper resolution made possible by the ReMi measurements. The cemented layers appear as sharp spikes in the downhole datasets and are problematic in crosshole measurements due to refraction. The refraction method is useful only to locate the depth to the uppermost cemented layer. The surface
Heat Transfer Through A Rotating Ball Bearing At Low Angular Velocities
Isert, Sarah
2011-01-01
Bearings are commonly used in mechanical systems when there are rotating parts in the system. For bearings that run at speeds above about 1000 revolutions per minute, such as those used in aircraft turbines, machining tools, and automotive engines, it is important to take into account the heat transfer through the bearing system due to friction. Heat transfer is generally not considered for applications where the bearing is rotating at low speeds, such as clocks and bicycles. However, for cer...
A dynamo model of magnetic activity in solar-like stars with different rotational velocities
Karak, Bidya Binay; Choudhuri, Arnab Rai
2014-01-01
We attempt to provide a quantitative theoretical explanation for the observations that Ca II H/K emission and X-ray emission from solar-like stars increase with decreasing Rossby number (i.e., with faster rotation). Assuming that these emissions are caused by magnetic cycles similar to the sunspot cycle, we construct flux transport dynamo models of $1M_{\\odot}$ stars rotating with different rotation periods. We first compute the differential rotation and the meridional circulation inside these stars from a mean-field hydrodynamics model. Then these are substituted in our dynamo code to produce periodic solutions. We find that the dimensionless amplitude $f_m$ of the toroidal flux through the star increases with decreasing Rossby number. The observational data can be matched if we assume the emissions to go as the power 3-4 of $f_m$. Assuming that the Babcock-Leighton mechanism saturates with increasing rotation, we can provide an explanation for the observed saturation of emission at low Rossby numbers. The m...
Lillo-Box, J; Mancini, L; Henning, Th; Figueira, P; Ciceri, S; Santos, N
2015-01-01
The Kepler mission has provided high-accurate photometric data in a long time span for more than two hundred thousands stars, looking for planetary transits. Among the detected candidates, the planetary nature of around 15% has been established or validated by different techniques. But additional data is needed to characterize the rest of the candidates and reject other possible configurations. We started a follow-up program to validate, confirm, and characterize some of the planet candidates. In this paper we present the radial velocity analysis (RV) of those presenting large variations, compatible with being eclipsing binaries. We also study those showing large rotational velocities, which prevents us from obtaining the necessary precision to detect planetary-like objects. We present new RV results for 13 Kepler objects of interest (KOIs) obtained with the CAFE spectrograph at the Calar Alto Observatory, and analyze their high-spatial resolution images and the Kepler light curves of some interesting cases. ...
Non Axisymmetric Relativistic Wind Accretion with Velocity Gradients onto a Rotating Black Hole
Cruz-Osorio, A
2016-01-01
We model, for the first time, the Bondi-Hoyle accretion of a fluid with velocity gradients onto a Kerr black hole, by numerically solving the fully relativistic hydrodynamics equations. Specifically, we consider a supersonic ideal gas, which has velocity gradients perpendicular to the relative motion. We measure the mass and specific angular accretion rates to illustrate whether the fluid presents unstable patterns or not. The initial parameters, we consider in this work, are the velocity gradient $\\epsilon_{v}$, the black hole spin $a$, the asymptotic Mach number ${\\cal M}_{\\infty}$ and adiabatic index $\\Gamma$. We show that the flow accretion reaches a fairly stationary regime, unlike in the Newtonian case, where significant fluctuations of the mass and angular momentum accretion rates are found. On the other hand, we consider a special case where both density and velocity gradients of the fluid are taken into account. The spin of the black hole and the asymptotic Newtonian Mach number, for this case, are $...
Objective assessment of surgical technique in rotation and nasal projection variation
Marina Serrato Coelho Fagundes
2016-02-01
Full Text Available ABSTRACT INTRODUCTION: In rhinoplasty, facial esthetic analysis is critical for proper surgical planning. Parameters such as rotation and nasal projection should be routinely evaluated. Few studies have objectively assessed changes in facial angles postoperatively. OBJECTIVE: To evaluate the effectiveness of medial intercrural sutures and of rotation of the nasal tip on the increase of rotation and nasal projection in Caucasian patients undergoing primary rhinoplasty. METHODS: A prospective study carried out between 2011 and 2013, with 27 patients treated with primary rhinoplasty with a basic technique by the same surgeon, with medial intercrural sutures and rotation of the nasal tip. Rotation and nasal projection were measured from photographs obtained preoperatively and after 12 months. RESULTS: All 27 patients completed the study. The mean age was 27.1 years. There was a mean increase of 8.4° in the rotation - a statistically significant value. There was no significant change in the projection. CONCLUSION: The medial intercrural and nasal tip rotation sutures are effective in increasing nasal rotation in Caucasian patients undergoing rhinoplasty.
Large-scale dynamo action driven by velocity shear and rotating convection.
Hughes, David W; Proctor, Michael R E
2009-01-30
By incorporating a large-scale shear flow into turbulent rotating convection, we show that a sufficiently strong shear can promote dynamo action in flows that are otherwise nondynamos. Our results are consistent with a dynamo driven either by the shear-current effect or by a fluctuating alpha effect interacting with the shear, but not with either a classical alpha(2) or alpha omega dynamo.
Gerber, Thomas; Liu Yuzhu; Knopp, Gregor; Hemberger, Patrick; Bodi, Andras; Radi, Peter; Sych, Yaroslav [Molecular Dynamics Group, Paul Scherrer Institut, 5232 Villigen (Switzerland)
2013-03-15
Velocity map imaging (VMI) is used in mass spectrometry and in angle resolved photo-electron spectroscopy to determine the lateral momentum distributions of charged particles accelerated towards a detector. VM-images are composed of projected Newton spheres with a common centre. The 2D images are usually evaluated by a decomposition into base vectors each representing the 2D projection of a set of particles starting from a centre with a specific velocity distribution. We propose to evaluate 1D projections of VM-images in terms of 1D projections of spherical functions, instead. The proposed evaluation algorithm shows that all distribution information can be retrieved from an adequately chosen set of 1D projections, alleviating the numerical effort for the interpretation of VM-images considerably. The obtained results produce directly the coefficients of the involved spherical functions, making the reconstruction of sliced Newton spheres obsolete.
Triaxial projected shell model study of chiral rotation in odd-odd nuclei
Bhat, G.H. [Department of Physics, University of Kashmir, Srinagar, 190 006 (India); Sheikh, J.A. [Department of Physics, University of Kashmir, Srinagar, 190 006 (India); Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996 (United States); Palit, R., E-mail: palit@tifr.res.in [Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Colaba, Mumbai, 400 005 (India)
2012-01-20
Chiral rotation observed in {sup 128}Cs is studied using the newly developed microscopic triaxial projected shell model (TPSM) approach. The observed energy levels and the electromagnetic transition probabilities of the nearly degenerate chiral dipole bands in this isotope are well reproduced by the present model. This demonstrates the broad applicability of the TPSM approach, based on a schematic interaction and angular-momentum projection technique, to explain a variety of low- and high-spin phenomena in triaxial rotating nuclei.
Rotational Viscometers--A Subject for Student Projects
Kraftmakher, Yaakov
2010-01-01
Three variants of the rotational viscometer employing a dc motor are considered. The viscometers are highly suitable for liquids of high viscosity, such as glycerol or oils (that is, for [eta] in the range 10-1000 mPa s). The set-ups are very simple and can serve as a first step to designing devices that are more complicated. Experimentation with…
Luo, Jun; Cai, Zhenbing; Mo, Jiliang; Peng, Jinfang; Zhu, Minhao
2016-05-01
Rotational fretting which exist in many engineering applications has incurred enormous economic loss. Thus, accessible methods are urgently needed to alleviate or eliminate damage by rotational fretting. Surface engineering is an effective approach that is successfully adopted to enhance the ability of components to resist the fretting damage. In this paper, using a high-velocity oxygen fuel sprayed (HVOF) technique WC-17Co coating is deposited on an LZ50 steel surface to study its properties through Vickers hardness testing, scanning electric microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffractrometry (XRD). Rotational fretting wear tests are conducted under normal load varied from 10 N to 50 N, and angular displacement amplitudes vary from 0.125° to 1°. Wear scars are examined using SEM, EDX, optical microscopy (OM), and surface topography. The experimental results reveal that the WC-17Co coating adjusted the boundary between the partial slip regime (PSR) and the slip regime (SR) to the direction of smaller amplitude displacement. As a result, the coefficients of friction are consistently lower than the substrate's coefficients of friction both in the PSR and SR. The damage to the coating in the PSR is very slight. In the SR, the coating exhibits higher debris removal efficiency and load-carrying capacity. The bulge is not found for the coating due to the coating's higher hardness to restrain plastic flow. This research could provide experimental bases for promoting industrial application of WC-17Co coating in prevention of rotational fretting wear.
Malo, Lison; Doyon, René; Lafrenière, David; Albert, Loïc; Gagné, Jonathan
2014-01-01
Based on high-resolution spectra obtained with PHOENIX at Gemini-South, CRIRES at VLT-UT1, and ESPaDOnS at CFHT, we present new measurements of the radial and projected rotational velocities of 219 low-mass stars. The target likely membership was initially established using the Bayesian analysis tool recently presented in \\citet{2013malo}, taking into account only the position, proper motion and photometry of the stars to assess their membership probability. In the present study, we include radial velocity as an additional input to our analysis, and in doing so we confirm the high membership probability for 130 candidates: 27 in $\\beta$ Pictoris, 22 in Tucana-Horologium, 25 in Columba, 7 in Carina, 18 in Argus and 18 in AB Doradus and 13 with an ambiguous membership. Our analysis also confirms the membership of 57 stars proposed in the literature. A subsample of 16 candidates was observed at three or more epochs, allowing us to discover 6 new spectroscopic binaries. The fraction of binaries in our sample is 2...
Hall, Patrick B; Petitjean, P; Paris, I; Ak, N Filiz; Shen, Yue; Gibson, R R; Aubourg, E; Anderson, S F; Schneider, D P; Bizyaev, D; Brinkmann, J; Malanushenko, E; Malanushenko, V; Myers, A D; Oravetz, D J; Ross, N P; Shelden, A; Simmons, A E; Streblyanska, A; Weaver, B A; York, D G
2013-01-01
We report the discovery in the Sloan Digital Sky Survey and the SDSS-III Baryon Oscillation Spectroscopic Survey of seventeen broad absorption line (BAL) quasars with high-ionization troughs that include absorption redshifted relative to the quasar rest frame. The redshifted troughs extend to velocities up to v=12,000 km/s and the trough widths exceed 3000 km/s in all but one case. Approximately 1 in 1000 BAL quasars with blueshifted C IV absorption also has redshifted C IV absorption; objects with C IV absorption present only at redshifted velocities are roughly four times rarer. In more than half of our objects, redshifted absorption is seen in C II or Al III as well as C IV, making low-ionization absorption at least ten times more common among BAL quasars with redshifted troughs than among standard BAL quasars. However, the C IV absorption equivalent widths in our objects are on average smaller than those of standard BAL quasars with low-ionization absorption. We consider several possible ways of generatin...
Gradiometer Based on Nonlinear Magneto-Optic Rotation Project
National Aeronautics and Space Administration — This Phase I SBIR project will demonstrate sensitive measurements of magnetic field gradients by nonlinear atomic spectroscopy. The gradients are determined by...
Trace projection transformation: a new method for measurement of debris flow surface velocity fields
Yan, Yan; Cui, Peng; Guo, Xiaojun; Ge, Yonggang
2016-12-01
Spatiotemporal variation of velocity is important for debris flow dynamics. This paper presents a new method, the trace projection transformation, for accurate, non-contact measurement of a debris-flow surface velocity field based on a combination of dense optical flow and perspective projection transformation. The algorithm for interpreting and processing is implemented in C ++ and realized in Visual Studio 2012. The method allows quantitative analysis of flow motion through videos from various angles (camera positioned at the opposite direction of fluid motion). It yields the spatiotemporal distribution of surface velocity field at pixel level and thus provides a quantitative description of the surface processes. The trace projection transformation is superior to conventional measurement methods in that it obtains the full surface velocity field by computing the optical flow of all pixels. The result achieves a 90% accuracy of when comparing with the observed values. As a case study, the method is applied to the quantitative analysis of surface velocity field of a specific debris flow.
The Transfer Velocity Project: A Comprehensive Look at the Transfer Function
Hayward, Craig
2011-01-01
The 1999-2000 Transfer Velocity Project (TVP) cohort of 147,207 community college students is used to develop both a college-level endogenous model, appropriate for applied research and guidance for campus action, and a student-level model. Survival analysis (Cox regression) is employed to evaluate the relative contribution of 53 student-level…
O'Brien, Ricky T.; Cooper, Benjamin J.; Keall, Paul J.
2013-03-01
Four dimensional cone beam computed tomography (4DCBCT) is an emerging clinical image guidance strategy for tumour sites affected by respiratory motion. In current generation 4DCBCT techniques, both the gantry rotation speed and imaging frequency are constant and independent of the patient’s breathing which can lead to projection clustering. We present a mixed integer quadratic programming (MIQP) model for respiratory motion guided-4DCBCT (RMG-4DCBCT) which regulates the gantry velocity and projection time interval, in response to the patient’s respiratory signal, so that a full set of evenly spaced projections can be taken in a number of phase, or displacement, bins during the respiratory cycle. In each respiratory bin, an image can be reconstructed from the projections to give a 4D view of the patient’s anatomy so that the motion of the lungs, and tumour, can be observed during the breathing cycle. A solution to the full MIQP model in a practical amount of time, 10 s, is not possible with the leading commercial MIQP solvers, so a heuristic method is presented. Using parameter settings typically used on current generation 4DCBCT systems (4 min image acquisition, 1200 projections, 10 respiratory bins) and a sinusoidal breathing trace with a 4 s period, we show that the root mean square (RMS) of the angular separation between projections with displacement binning is 2.7° using existing constant gantry speed systems and 0.6° using RMG-4DCBCT. For phase based binning the RMS is 2.7° using constant gantry speed systems and 2.5° using RMG-4DCBCT. The optimization algorithm presented is a critical step on the path to developing a system for RMG-4DCBCT.
吴静; 姚列明; 朱建华; 韩晓玉; 李文柱
2012-01-01
This paper deals with the profile measurement of impurity ion temperature and toroidal rotation velocity that can be achieved by using the charge exchange recombination spectrum (CXRS) diagnostics tool built on the HL-2A toknmak. By using CXRS, an accurate impurity ion temperature and toroidal plasma rotation velocity profile can be achieved under the condition of neutrM beam injection (NBI) heating. Considering the edge effect of the line of CVI 529.06 nm (n= 8-7), which contains three lines (active exciting spectral line (ACX), passivity exciting spectral line (PCX) and electron exciting spectral line (ICE)), and using three Gaussian fitted curves, we obtain the following experimental results: the core ion temperature of HL-2A device is nearly thousands of eV, and the plasma rotation velocity reaches about 104 m· s^-1. At the end of paper, some explanations are presented for the relationship between the curves and the inner physical mechanism.
Wu, Jing; Yao, Lieming; Zhu, Jianhua; Han, Xiaoyu; Li, Wenzhu
2012-11-01
This paper deals with the profile measurement of impurity ion temperature and toroidal rotation velocity that can be achieved by using the charge exchange recombination spectrum (CXRS) diagnostics tool built on the HL-2A tokamak. By using CXRS, an accurate impurity ion temperature and toroidal plasma rotation velocity profile can be achieved under the condition of neutral beam injection (NBI) heating. Considering the edge effect of the line of CVI 529.06 nm (n = 8~7), which contains three lines (active exciting spectral line (ACX), passivity exciting spectral line (PCX) and electron exciting spectral line (ICE)), and using three Gaussian fitted curves, we obtain the following experimental results: the core ion temperature of HL-2A device is nearly thousands of eV, and the plasma rotation velocity reaches about 104 m · s-1. At the end of paper, some explanations are presented for the relationship between the curves and the inner physical mechanism.
Au, Jason S; Ditor, David S; MacDonald, Maureen J; Stöhr, Eric J
2016-07-01
Recent studies have identified a predictable movement pattern of the common carotid artery wall in the longitudinal direction. While there is evidence that the magnitude of this carotid artery longitudinal wall motion (CALM) is sensitive to cardiovascular health status, little is known about the determinants of CALM The purpose of this integrative study was to evaluate the contribution of left ventricular (LV) cardiac motion and local blood velocity to CALM Simultaneous ultrasound measurements of CALM, common carotid artery mean blood velocity (MBV), and left ventricular motion were performed in ten young, healthy individuals (6 males; 22 ± 1 years). Peak anterograde CALM occurred at a similar time as peak MBV (18.57 ± 3.98% vs. 18.53 ± 2.81% cardiac cycle; t-test: P = 0.94; ICC: 0.79, P longitudinal displacement was not associated with peak CALM (r = 0.11, P = 0.77). These results suggest that the rotational mechanical movement of the LV base may be closely associated with longitudinal mechanics in the carotid artery. This finding may have important implications for interpreting the complex relationship between ventricular and vascular function.
Mock-up stands for a rotating target for CSNS project
Jia, X. J.; Bauer, G. S.; He, W.; Sun, Y. L.; Liang, T. J.; Yin, W.; Zhao, D.
2010-03-01
This paper summarises pre-conceptual solutions for all sub-units of a potential rotating target system for the CSNS project. In order to test the validity of this concept and to gain first experience with a rotating target, the CSNS project has decided to embark on the construction of a mock-up test stand. The purpose is to provide first demonstration of the viability of the above concept by using a full model of the target head components and shaft and a dummy target with the right diameter and weight; confirm that acceptance criteria can be reached; gain experience in running a rotating target; verify certain parameters obtained by calculations. By carrying out a development program, it should be possible to produce a sound basis for a decision as to whether or not CSNS wants to adopt a rotating target as the preferred solution.
The Sloan Digital Sky Survey Reverberation Mapping Project: Velocity Shifts of Quasar Emission Lines
Shen, Yue; Denney, Kelly D; Greene, Jenny E; Grier, C J; Ho, Luis C; Peterson, Bradley M; Petitjean, Patrick; Richards, Gordon T; Schneider, Donald P; Tao, Charling; Trump, Jonathan R
2016-01-01
Quasar emission lines are often shifted from the systemic velocity due to various dynamical and radiative processes in the line-emitting region. The level of these velocity shifts depends both on the line species and on quasar properties. We study velocity shifts for the line peaks of various narrow and broad quasar emission lines relative to systemic using a sample of 849 quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. The coadded (from 32 epochs) spectra of individual quasars have sufficient signal-to-noise ratio (SNR) to measure stellar absorption lines to provide reliable systemic velocity estimates, as well as weak narrow emission lines. The sample also covers a large dynamic range in quasar luminosity (~2 dex), allowing us to explore potential luminosity dependence of the velocity shifts. We derive average line peak velocity shifts as a function of quasar luminosity for different lines, and quantify their intrinsic scatter. We further quantify how well the peak velocit...
Two-dimensional models of early-type fast rotating stars: the ESTER project
Rieutord, Michel
2015-01-01
In this talk I present the latest results of the ESTER project that has taken up the challenge of building two dimensional (axisymmetric) models of stars rotating at any rotation rate. In particular, I focus on main sequence massive and intermediate mass stars. I show what should be expected in such stars as far as the differential rotation and the associated meridional circulation are concerned, notably the emergence of a Stewartson layer along the tangent cylinder of the core. I also indicate what may be inferred about the evolution of an intermediate-mass star at constant angular momentum and how Be stars may form. I finally give some comparisons between models and observations of the gravity darkening on some nearby fast rotators as it has been derived from interferometric observations. In passing, I also discuss how 2D models can help to recover the fundamental parameters of a star.
Cerqueira, A H; Raga, A C; Vasconcelos, M J; De Colle, F
2005-01-01
Using the Yguazu-a three-dimensional hydrodynamic code, we have computed a set of numerical simulations of heavy, supersonic, radiatively cooling jets including variabilities in both the ejection direction (precession) and the jet velocity (intermittence). In order to investigate the effects of jet rotation on the shape of the line profiles, we also introduce an initial toroidal rotation velocity profile, in agreement with some recent observational evidence found in jets from T Tauri stars which seems to support the presence of a rotation velocity pattern inside the jet beam, near the jet production region. Since the Yguazu-a code includes an atomic/ionic network, we are able to compute the emission coefficients for several emission lines, and we generate line profiles for the H, [O I]6300, [S II]6716 and [N II]6548 lines. Using initial parameters that are suitable for the DG Tau microjet, we show that the computed radial velocity shift for the medium-velocity component of the line profile as a function of di...
Bajkova, A T
2016-01-01
Three three-component (bulge, disk, halo) model Galactic gravitational potentials differing by the expression for the dark matter halo are considered. The central (bulge) and disk components are described by the Miyamoto-Nagai expressions. The Allen-Santill'an (I), Wilkinson-Evans (II), and Navarro-Frenk-White (III) models are used to describe the halo. A set of present-day observational data in the range of Galactocentric distances R from 0 to 200 kpc is used to refine the parameters of these models. The model rotation curves have been fitted to the observed velocities by taking into account the constraints on the local matter density \\rho_\\odotand the force K_{z=1.1} acting perpendicularly to the Galactic plane. The Galactic mass within a sphere of radius 50 kpc, M_G (R<=50 kpc)=(0.41+/-0.12)x10^12 M_\\odot, is shown to satisfy all three models. The differences between the models become increasingly significant with increasing radius R. In model I, the Galactic mass within a sphere of radius 200 kpc turns...
van der Male, Pim; van Dalen, Karel N.; Metrikine, Andrei V.
2016-11-01
Existing models for the analysis of offshore wind turbines account for the aerodynamic action on the turbine rotor in detail, requiring a high computational price. When considering the foundation of an offshore wind turbine, however, a reduced rotor model may be sufficient. To define such a model, the significance of the nonlinear velocity and history dependency of the aerodynamic force on a rotating blade should be known. Aerodynamic interaction renders the dynamics of a rotating blade in an ambient wind field nonlinear in terms of the dependency on the wind velocity relative to the structural motion. Moreover, the development in time of the aerodynamic force does not follow the flow velocity instantaneously, implying a history dependency. In addition, both the non-uniform blade geometry and the aerodynamic interaction couple the blade motions in and out of the rotational plane. Therefore, this study presents the Euler-Bernoulli formulation of a twisted rotating blade connected to a rigid hub, excited by either instantaneous or history-dependent aerodynamic forces. On this basis, the importance of the history dependency is determined. Moreover, to assess the nonlinear contributions, both models are linearized. The structural response is computed for a stand-still and a rotating blade, based on the NREL 5-MW turbine. To this end, the model is reduced on the basis of its first three free-vibration mode shapes. Blade tip response predictions, computed from turbulent excitation, correctly account for both modal and directional couplings, and the added damping resulting from the dependency of the aerodynamic force on the structural motion. Considering the deflection of the blade tip, the history-dependent and the instantaneous force models perform equally well, providing a basis for the potential use of the instantaneous model for the rotor reduction. The linearized instantaneous model provides similar results for the rotating blade, indicating its potential
Ocean Circulation in a Rotating Tank - An Outreach Project in Fluid Dynamics
Reckinger, Shanon
2013-11-01
A rotating water tank was designed and built by two senior mechanical engineering undergraduates at Fairfield University. The project was part of a year long senior design course. The rotating water tank is used to simulate oceanic and atmospheric phenomenon for classroom or outreach use. The following year, the tank was used for outreach as part of Fairfield University's Broadening Access to Science Education (BASE) camp. BASE camp is a two week residential camp for high school woman interested in scientific research. It is designed to inform and excite students by giving them a hands-on, research-based experience in the sciences, engineering, and mathematics. An all female research team composed of one mechanical engineering faculty member, two engineering undergraduates, and three high school students used the tank to explore ``how the ocean moves.'' This talk will explain the design project and the outreach project in detail, in hopes of inspiring new fluids education and outreach ideas.
Bajkova, A. T.; Bobylev, V. V.
2016-09-01
Three three-component (bulge, disk, halo) model Galactic gravitational potentials differing by the expression for the dark matter halo are considered. The central (bulge) and disk components are described by the Miyamoto-Nagai expressions. The Allen-Santillán (I), Wilkinson-Evans (II), and Navarro-Frenk-White (III) models are used to describe the halo. A set of present-day observational data in the range of Galactocentric distances R from 0 to 200 kpc is used to refine the parameters of thesemodels. For the Allen-Santillán model, a dimensionless coefficient γ has been included as a sought-for parameter for the first time. In the traditional and modified versions, γ = 2.0 and 6.3, respectively. Both versions are considered in this paper. The model rotation curves have been fitted to the observed velocities by taking into account the constraints on the local matter density ρ ⊙ = 0.1 M ⊙ pc-3 and the force K z =1.1/2 πG = 77 M ⊙ pc-2 acting perpendicularly to the Galactic plane. The Galactic mass within a sphere of radius 50 kpc, M G ( R ≤ 50 kpc) ≈ (0.41 ± 0.12) × 1012 M ⊙, is shown to satisfy all three models. The differences between the models become increasingly significant with increasing radius R. In model I, the Galactic mass within a sphere of radius 200 kpc at γ = 2.0 turns out to be greatest among the models considered, M G ( R ≤ 200 kpc) = (1.45 ±0.30)× 1012 M ⊙, M G ( R ≤ 200 kpc) = (1.29± 0.14)× 1012 M ⊙ at γ = 6.3, and the smallest value has been found in model II, M G ( R ≤ 200 kpc) = (0.61 ± 0.12) × 1012 M ⊙. In our view, model III is the best one among those considered, because it ensures the smallest residual between the data and the constructed model rotation curve provided that the constraints on the local parameters hold with a high accuracy. Here, the Galactic mass is M G ( R ≤ 200 kpc) = (0.75 ± 0.19) × 1012 M ⊙. A comparative analysis with the models by Irrgang et al. (2013), including those using
RACE-OC Project: Rotation and variability in the open cluster NGC2099 (M37)
Messina, S; Parihar, Padmakar; Kang, Y B; Kim, S -L; Rey, S -C; Lee, C -U
2008-01-01
Rotation and solar-type magnetic activity are closely related to each other in stars of G or later spectral types. Presence and level of magnetic activity depend on star's rotation and rotation itself is strongly influenced by strength and topology of the magnetic fields. Open clusters represent especially useful targets to investigate the connection between rotation and activity. The open cluster NGC2099 has been studied as a part of the RACE-OC project, which is aimed at exploring the evolution of rotation and magnetic activity in the late-type members of open clusters of different ages. Time series CCD photometric observations of this cluster were collected during January 2004. The relations between activity manifestations, such as the light curve amplitude, and global stellar parameters are investigated. We have discovered 135 periodic variables, 122 of which are candidate cluster members. Determination of rotation periods of G- and K-type stars has allowed us to better explore evolution of angular moment...
VizieR Online Data Catalog: M4 Core Project with HST. Radial velocities (Malavolta+, 2015)
Malavolta, L.; Piotto, G.; Bedin, L. R.; Sneden, C.; Nascimbeni, V.; Sommariva, V.
2016-07-01
The spectra for our project were originally used by Sommariva et al. (2009A&A...493..947S) to study the internal velocity dispersion of M4 and to search for spectroscopic binaries. A total of 2771 stars covering colour-magnitude diagram (CMD) positions from the upper RGB to about 1mag fainter than the main-sequence turnoff (TO) luminosity were observed between 2003 and 2009, including 306 new spectra obtained in 2009 and targeting MS stars already observed in the previous epochs. Determination of the M 4 velocity dispersion and binary star fraction were the prime motivators for obtaining these data. Therefore nearly all stars were observed at least twice, and three or more spectra were obtained for nearly 40 per cent of the sample. (2 data files).
A number-projected model with generalized pairing interaction in application to rotating nuclei
Satula, W. [Warsaw Univ. (Poland)]|[Joint Institute for Heavy Ion Research, Oak Ridge, TN (United States)]|[Univ. of Tennessee, Knoxville, TN (United States)]|[Royal Institute of Technology, Stockholm (Sweden); Wyss, R. [Royal Institute of Technology, Stockholm (Sweden)
1996-12-31
A cranked mean-field model that takes into account both T=1 and T=0 pairing interactions is presented. The like-particle pairing interaction is described by means of a standard seniority force. The neutron-proton channel includes simultaneously correlations among particles moving in time reversed orbits (T=1) and identical orbits (T=0). The coupling between different pairing channels and nuclear rotation is taken into account selfconsistently. Approximate number-projection is included by means of the Lipkin-Nogami method. The transitions between different pairing phases are discussed as a function of neutron/proton excess, T{sub z}, and rotational frequency, {Dirac_h}{omega}.
Dong, Di; Zhu, Shouping; Qin, Chenghu; Kumar, V; Stein, J V; Oehler, S; Savakis, C; Tian, Jie; Ripoll, J
2013-01-01
Finding the center of rotation is an essential step for accurate three-dimensional reconstruction in optical projection tomography (OPT). Unfortunately current methods are not convenient since they require either prior scanning of a reference phantom, small structures of high intensity existing in the specimen, or active participation during the centering procedure. To solve these problems this paper proposes a fast and automatic center of rotation search method making use of parallel programming in graphics processing units (GPUs). Our method is based on a two step search approach making use only of those sections of the image with high signal to noise ratio. We have tested this method both in non-scattering ex vivo samples and in in vivo specimens with a considerable contribution of scattering such as Drosophila melanogaster pupae, recovering in all cases the center of rotation with a precision 1/4 pixel or less.
Abrashkin, V. I.; Voronov, K. E.; Piyakov, I. V.; Puzin, Yu. Ya.; Sazonov, V. V.; Syomkin, N. D.; Chebukov, S. Yu.
2016-09-01
The mathematical model, which allowed us to reconstruct the rotational motion of the Bion M-1 and Foton M-4 satellites by processing the measurements of onboard magnetometers and the angular velocity sensor, is sufficiently detailed and accurate. If we slightly lower the requirements for accuracy and transfer to a rougher model, i.e., we will not update the biases in measurements of the angular velocity component, then the measurement processing technique can be significantly simplified. The volume of calculations in minimizing the functional of the least-square technique is reduced; the most complicated part of calculations is performed using the standard procedure of computational linear algebra. This simplified technique is described below, and the examples of its application for reconstructing the rotational motion of the Foton M-4 satellite are presented. A noticeable distinction in the reconstructions of motion, constructed by simplified and more exact techniques, is revealed in processing the measurements over time intervals longer than 4 hours.
Centre of Rotation Determination Using Projection Data in X-ray Micro Computed Tomography
Olander, Birger
1994-01-01
There are several methods available to determine the Centre Of Rotation, COR, and align detectors and X-ray focus to COR in X-ray computed tomography. Some methods use narrow rods/needles or specially made alignment objects or phantoms. In X-ray Micro Computed Tomography (or Computerized Micro Tomography), μCT (CMT), methods using sample projection data for COR measurements are preferred since the replacement of alignment objects with samples often displace translation stages and make the ali...
Bekeraité, S.; Walcher, C. J.; Falcón-Barroso, J.; Garcia Lorenzo, B.; Lyubenova, M.; Sánchez, S. F.; Spekkens, K.; van de Ven, G.; Wisotzki, L.; Ziegler, B.; Aguerri, J. A. L.; Barrera-Ballesteros, J.; Bland-Hawthorn, J.; Catalán-Torrecilla, C.; García-Benito, R.
2016-10-01
We measured the distribution in absolute magnitude - circular velocity space for a well-defined sample of 199 rotating galaxies of the Calar Alto Legacy Integral Field Area Survey (CALIFA) using their stellar kinematics. Our aim in this analysis is to avoid subjective selection criteria and to take volume and large-scale structure factors into account. Using stellar velocity fields instead of gas emission line kinematics allows including rapidly rotating early-type galaxies. Our initial sample contains 277 galaxies with available stellar velocity fields and growth curve r-band photometry. After rejecting 51 velocity fields that could not be modelled because of the low number of bins, foreground contamination, or significant interaction, we performed Markov chain Monte Carlo modelling of the velocity fields, from which we obtained the rotation curve and kinematic parameters and their realistic uncertainties. We performed an extinction correction and calculated the circular velocity vcirc accounting for the pressure support of a given galaxy. The resulting galaxy distribution on the Mr-vcirc plane was then modelled as a mixture of two distinct populations, allowing robust and reproducible rejection of outliers, a significant fraction of which are slow rotators. The selection effects are understood well enough that we were able to correct for the incompleteness of the sample. The 199 galaxies were weighted by volume and large-scale structure factors, which enabled us to fit a volume-corrected Tully-Fisher relation (TFR). More importantly, we also provide the volume-corrected distribution of galaxies in the Mr-vcirc plane, which can be compared with cosmological simulations. The joint distribution of the luminosity and circular velocity space densities, representative over the range of -20 > Mr > -22 mag, can place more stringent constraints on the galaxy formation and evolution scenarios than linear TFR fit parameters or the luminosity function alone. Galaxies main
Brown, R. S.; Waugh, R. C.
1980-01-01
The results of a re-evaluation of the propellant combustion data obtained using the dual valve approach for measuring velocity-coupling characteristics of solid propellants are presented. Data analysis and testing procedures are described. The velocity response is compared to pressure-coupled response data within the context of thermal wave response theory. This comparison shows important inconsistencies which cast doubt on inferring the velocity response from pressure-coupled response functions.
Dawson, W.M. [N.I. Horticulture and Plant Breeding Station, Armagh (Ireland); Isebrands, J. [USDA Forest Service, North Central Forest Experiment Station, Rhinelander, WI (United States); Namkoong, G. [Univ. of British Columbia, Vancouver, BC (Canada). Dept. of Forest Sciences; Tahvanainen, J. [Univ. of Joensuu (Finland). Dept. of Biology
1996-11-01
The purpose of this evaluation was to inform NUTEK of the scientific quality of the research projects, as seen in an international context. The projects were therefore the main elements considered in the evaluation. The main basis of the evaluation was the scientific quality of the research and its relevance to NUTEK`s aims in the application of industrial research and development. The present report is based on the information contained in the written reports submitted by the grant holders, site visits and discussions between the grant holders and the Committee. The report first gives an overview and general recommendations concerning the overall programme in the field of Short Rotation Forestry for Energy. Thereafter, the 16 projects are evaluated separately
Zhu, Ling; van de Ven, Glenn; Long, R J; Watkins, Laura L; Pota, Vincenzo; Napolitano, Nicola R; Forbes, Duncan A; Brodie, Jean; Foster, Caroline
2016-01-01
We construct a suite of discrete chemo-dynamical models of the giant elliptical galaxy NGC 5846. These models are a powerful tool to constrain both the mass distribution and internal dynamics of multiple tracer populations. We use Jeans models to simultaneously fit stellar kinematics within the effective radius $R_{\\rm e}$, planetary nebula (PN) radial velocities out to $3\\, R_{\\rm e}$, and globular cluster (GC) radial velocities and colours out to $6\\,R_{\\rm e}$. The best-fitting model is a cored DM halo which contributes $\\sim 10\\%$ of the total mass within $1\\,R_{\\rm e}$, and $67\\% \\pm 10\\%$ within $6\\,R_{\\rm e}$, although a cusped DM halo is also acceptable. The red GCs exhibit mild rotation with $v_{\\rm max}/\\sigma_0 \\sim 0.3$ in the region $R > \\,R_{\\rm e}$, aligned with but counter-rotating to the stars in the inner parts, while the blue GCs and PNe kinematics are consistent with no rotation. The red GCs are tangentially anisotropic, the blue GCs are mildly radially anisotropic, and the PNe vary from r...
Zhu, Ling; Romanowsky, Aaron J.; van de Ven, Glenn; Long, R. J.; Watkins, Laura L.; Pota, Vincenzo; Napolitano, Nicola R.; Forbes, Duncan A.; Brodie, Jean; Foster, Caroline
2016-11-01
We construct a suite of discrete chemo-dynamical models of the giant elliptical galaxy NGC 5846. These models are a powerful tool to constrain both the mass distribution and internal dynamics of multiple tracer populations. We use Jeans models to simultaneously fit stellar kinematics within the effective radius Re, planetary nebula (PN) radial velocities out to 3 Re, and globular cluster (GC) radial velocities and colours out to 6 Re. The best-fitting model is a cored dark matter halo which contributes ˜10 per cent of the total mass within 1 Re, and 67 per cent ± 10 per cent within 6 Re, although a cusped dark matter halo is also acceptable. The red GCs exhibit mild rotation with vmax/σ0 ˜ 0.3 in the region R > Re, aligned with but counter-rotating to the stars in the inner parts, while the blue GCs and PNe kinematics are consistent with no rotation. The red GCs are tangentially anisotropic, the blue GCs are mildly radially anisotropic, and the PNe vary from radially to tangentially anisotropic from the inner to the outer region. This is confirmed by general made-to-measure models. The tangential anisotropy of the red GCs in the inner regions could stem from the preferential destruction of red GCs on more radial orbits, while their outer tangential anisotropy - similar to the PNe in this region - has no good explanation. The mild radial anisotropy of the blue GCs is consistent with an accretion scenario.
The BANANA project. V. Misaligned and precessing stellar rotation axes in CV Velorum
Albrecht, Simon; Winn, Joshua N.; Triaud, Amaury [Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Torres, Guillermo [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Fabrycky, Daniel C. [Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, CA 95064 (United States); Setiawan, Johny [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Gillon, Michaël; Jehin, Emmanuel [Institut d' Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, Bat. B5C, Liège 1 (Belgium); Queloz, Didier [Observatoire Astronomique de lÚniversité de Genève, Chemin des Maillettes 51, Sauverny CH-1290 (Switzerland); Snellen, Ignas [Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden (Netherlands); Eggleton, Peter [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94551 (United States)
2014-04-20
As part of the Binaries Are Not Always Neatly Aligned project (BANANA), we have found that the eclipsing binary CV Velorum has misaligned rotation axes. Based on our analysis of the Rossiter-McLaughlin effect, we find sky-projected spin-orbit angles of β{sub p} = –52° ± 6° and β{sub s} = 3° ± 7° for the primary and secondary stars (B2.5V + B2.5V, P = 6.9 days). We combine this information with several measurements of changing projected stellar rotation speeds (vsin i {sub *}) over the last 30 yr, leading to a model in which the primary star's obliquity is ≈65°, and its spin axis precesses around the total angular momentum vector with a period of about 140 yr. The geometry of the secondary star is less clear, although a significant obliquity is also implicated by the observed time variations in the vsin i {sub *}. By integrating the secular tidal evolution equations backward in time, we find that the system could have evolved from a state of even stronger misalignment similar to DI Herculis, a younger but otherwise comparable binary.
The BANANA project. V. Misaligned and precessing stellar rotation axes in CV Velorum
Albrecht, Simon; Torres, Guillermo; Fabrycky, Daniel C; Setiawan, Johny; Gillon, Michael; Jehin, Emmanuel; Triaud, Amaury; Queloz, Didier; Snellen, Ignas; Eggleton, Peter
2014-01-01
As part of the BANANA project (Binaries Are Not Always Neatly Aligned), we have found that the eclipsing binary CV Velorum has misaligned rotation axes. Based on our analysis of the Rossiter-McLaughlin effect, we find sky-projected spin-orbit angles of $\\beta_{\\rm p} = -52\\pm6^{\\circ}$ and $\\beta_{\\rm s}= 3\\pm7^{\\circ}$ for the primary and secondary stars (B2.5V $+$ B2.5V, $P=6.9$ d). We combine this information with several measurements of changing projected stellar rotation speeds ($v \\sin i_{\\star}$) over the last $30$ years, leading to a model in which the primary star's obliquity is $\\approx65^{\\circ}$, and its spin axis precesses around the total angular momentum vector with a period of about $140$ years. The geometry of the secondary star is less clear, although a significant obliquity is also implicated by the observed time variations in the $v \\sin i_{\\star}$. By integrating the secular tidal evolution equations backward in time, we find that the system could have evolved from a state of even stronge...
Nam, Sang Boo
2009-01-01
The transverse and longitudinal Doppler effects of the sunbeam spectra are shown to result in the earth parameters such as the earth-self rotation and revolution velocities, the earth orbit semi-major axis, the earth orbital angular momentum, the earth axial tilt, the earth orbit eccentricity, the local latitude and the mass of the sun. The sunbeam global positioning scheme is realized, including the earth orbital position. PACS numbers: 91.10.Fc, 95.10.Km, 91.10.Da, 91.10.Jf.
Froessling, Nils
1958-01-01
The fundamental boundary layer equations for the flow, temperature and concentration fields are presented. Two dimensional symmetrical and unsymmetrical and rotationally symmetrical steady boundary layer flows are treated as well as the transfer boundary layer. Approximation methods for the calculation of the transfer layer are discussed and a brief survey of an investigation into the validity of the law that the Nusselt number is proportional to the cube root of the Prandtl number is presented.
The catalogue of radial velocity variable hot subluminous stars from the MUCHFUSS project
Geier, S; Heber, U; Schaffenroth, V; Barlow, B N; stensen, R H O; O'Toole, S J; Ziegerer, E; Heuser, C; Maxted, P F L; Gänsicke, B T; Marsh, T R; Napiwotzki, R; Brünner, P; Schindewolf, M; Niederhofer, F
2015-01-01
The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims to find sdBs with compact companions like massive white dwarfs, neutron stars or black holes. Here we provide classifications, atmospheric parameters and a complete radial velocity (RV) catalogue containing 1914 single measurements for an sample of 177 hot subluminous stars discovered based on SDSS DR7. 110 stars show significant RV variability, while 67 qualify as candidates. We constrain the fraction of close massive compact companions {of hydrogen-rich hot subdwarfs} in our sample to be smaller than $\\sim1.3\\%$, which is already close to the theoretical predictions. However, the sample might still contain such binaries with longer periods exceeding $\\sim8\\,{\\rm d}$. We detect a mismatch between the $\\Delta RV_{\\rm max}$-distribution of the sdB and the more evolved sdOB and sdO stars, which challenges our understanding of their evolutionary connection. Furthermore, irregular RV variations of unknown origin with ...
Steffen, Holger; Johansson, Jan; Kierulf, Halfdan Pascal; Kristiansen, Oddgeir; Lidberg, Martin; Tarasov, Lev
2016-04-01
The BIFROST (Baseline Inferences for Fennoscandian Rebound Observations Sea Level and Tectonics) project was started in 1993. The primary goal was to establish a new and useful three-dimensional measurement of crustal movement based on Global Navigation Satellite System (GNSS) observations, that is able to constrain models of the glacial isostatic adjustment (GIA) in Fennoscandia. Station velocities derived from analysis of observations at permanent GNSS stations in the Nordic countries and beyond have been published over the last 15 years. The latest GNSS-based 3D velocity field of Fennoscandia is a result of a re-processing of data from 1993 to 2014 from more than two hundred stations in northern Europe. It is computed using a state-of-the-art strategy. In this poster, we analyse the computed station velocities towards identification of lateral variations in lithospheric thickness and mantle viscosity in Fennoscandia. We therefore focus on the horizontal components. We compare observed velocities against velocities from a large set of GIA models. Preliminary results show that inclusion of lateral mantle viscosity variations in the model is necessary to explain distinct horizontal velocity patterns of the observed motion. However, some patterns can also be explained by strong lithospheric thickness variations, which requires an extended analysis in future.
Lee, Byeong-Cheol; Park, Myeong-Gu; Kim, Kang-Min; Mkrtichian, David E
2012-01-01
Aims. In order to search for and study the nature of the low-amplitude and long-periodic radial velocity (RV) variations of massive stars, we have been carrying out a precise RV survey for supergiants that lie near or inside the Cepheid instability strip. Methods. We have obtained high-resolution spectra of {\\alpha} Per (F5 Ib) from November 2005 to September 2011 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO). Results. Our measurements reveal that {\\alpha} Per shows a periodic RV variation of 128 days and a semi-amplitude of 70 m/s. We find no strong correlation between RV variations and bisector velocity span (BVS), but the 128-d peak is indeed present in the BVS variations among several other significant peaks in periodogram. Conclusions. {\\alpha} Per may have an exoplanet, but the combined data spanning over 20 years seem to suggest that the 128-d RV variations have not been stable on long-term scale, which is somewhat difficult to r...
Zhu, Ling; van de Ven, Glenn; Watkins, Laura L.; Posti, Lorenzo
2016-11-01
We present a new discrete chemo-dynamical axisymmetric modelling technique, which we apply to the dwarf spheroidal galaxy Sculptor. The major improvement over previous Jeans models is that realistic chemical distributions are included directly in the dynamical modelling of the discrete data. This avoids loss of information due to spatial binning and eliminates the need for hard cuts to remove contaminants and to separate stars based on their chemical properties. Using a combined likelihood in position, metallicity and kinematics, we find that our models naturally separate Sculptor stars into a metal-rich and a metal-poor population. Allowing for non-spherical symmetry, our approach provides a central slope of the dark matter density of γ = 0.5 ± 0.3. The metal-rich population is nearly isotropic (with β _r^{red} = 0.0± 0.1), while the metal-poor population is tangentially anisotropic (with β _r^{blue} = -0.2± 0.1) around the half-light radius of 0.26 kpc. A weak internal rotation of the metal-rich population is revealed with vmax/σ0 = 0.15 ± 0.15. We run tests using mock data to show that a discrete data set with ˜6000 stars is required to distinguish between a core (γ = 0) and cusp (γ = 1), and to constrain the possible internal rotation to better than 1σ confidence with our model. We conclude that our discrete chemo-dynamical modelling technique provides a flexible and powerful tool to robustly constrain the internal dynamics of multiple populations, and the total mass distribution in a stellar system.
Szuba, Łukasz; Markowska, Iga; Czamara, Andrzej; Noga, Henryk
2016-10-01
We aimed to use biomechanical testing to assess differences in the power and strength of patients who participated in a short-term, home-based rehabilitation program following arthroscopic labral repair compared with a healthy control group. The functional outcomes of patients who underwent arthroscopic labral repair followed by self-directed short-term rehabilitation at home were compared with age- and body mass index (BMI)-matched healthy controls. Group I included 20 male patients who had undergone arthroscopic labral repair after being diagnosed with recurrent anterior glenohumeral joint instability without bony lesions of the humeral head or glenoid. Postoperatively, they participated in physical therapy for 17±4 appointments, followed by self-guided home-based exercises. Group II included 25 males without injuries. The two groups were matched for age and BMI. The orthopaedic examination, functional tests, and biomechanical measurements were performed under isokinetic conditions at an average of 16±3 months postoperatively. Significant differences were observed in range of shoulder rotation on the operative shoulder compared with the unaffected side and in the dominant arms of the control group. The patients were also found to have significant deficits in biomechanical parameters such as power and peak torque angle. Significant deficits in peak torque, power, and peak torque angle during external and internal shoulder rotation remained up to 16 months after arthroscopic labral repair. Further research is needed to understand the changes in shoulder power assessment after labral repair. Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
PROJECT VeSElkA: ANALYSIS OF BALMER LINE PROFILES OF SLOWLY ROTATING CHEMICALLY PECULIAR STARS
Khalack, V.; LeBlanc, F., E-mail: khalack.viktor@umoncton.ca [Département de Physique et d’Astronomie, Université de Moncton, Moncton, N.-B., E1A 3E9 (Canada)
2015-07-15
We present results for the estimation of gravity, effective temperature, and radial velocity of poorly studied chemically peculiar stars recently observed with the spectropolarimeter Echelle SpectroPolarimetric Device for Observations of Stars at the Canada–France–Hawaii Telescope in the frame of the Vertical Stratification of Element Abundances project. The effective temperature and surface gravity values are determined for the very first time for four of the stars from our sample (HD 23878, HD 83373, HD 95608, and HD 164584). Grids of stellar atmosphere models with the corresponding fluxes have been calculated using version 15 of the PHOENIX code for effective temperatures in the range of 5000–15,000 K, for the logarithm of surface gravities in the range of 3.0–4.5 and for the metallicities from −1.0 to +1.5. We used these fluxes to fit the Balmer line profiles employing the code FITSB2 that produces estimates of the effective temperature, gravity, and radial velocity for each star. When possible, our results are compared to those previously published. The physical characteristics of 16 program stars are discussed with the future aim to study the abundance anomalies of chemical species and the possible vertical abundance stratification in their stellar atmosphere.
Project VeSElkA: Analysis of Balmer line profiles in slowly rotating chemically peculiar stars
Khalack, Viktor
2015-01-01
We present results for the estimation of gravity, effective temperature, and radial velocity of poorly studied chemically peculiar stars recently observed with the spectropolarimeter Echelle SpectroPolarimetric Device for Observations of Stars at the Canada-France-Hawaii Telescope in the frame of the Vertical Stratification of Element Abundances project. The effective temperature and surface gravity values are determined for the very first time for four of the stars from our sample (HD23878, HD83373, HD95608, and HD164584). Grids of stellar atmosphere models with the corresponding fluxes have been calculated using version 15 of the PHOENIX code for effective temperatures in the range of 5000-15,000 K, for the logarithm of surface gravities in the range of 3.0-4.5 and for the metallicities from -1.0 to +1.5. We used these fluxes to fit the Balmer line profiles employing the code FITSB2 that produces estimates of the effective temperature, gravity, and radial velocity for each star. When possible, our results a...
Hill, K W; Bitter, M; Delgado-Aparicio, L; Johnson, D; Feder, R; Beiersdorfer, P; Dunn, J; Morris, K; Wang, E; Reinke, M; Podpaly, Y; Rice, J E; Barnsley, R; O'Mullane, M; Lee, S G
2010-10-01
Imaging x-ray crystal spectrometer (XCS) arrays are being developed as a US-ITER activity for Doppler measurement of T(i) and v profiles of impurities (W, Kr, and Fe) with ∼7 cm (a/30) and 10-100 ms resolution in ITER. The imaging XCS, modeled after a prototype instrument on Alcator C-Mod, uses a spherically bent crystal and 2D x-ray detectors to achieve high spectral resolving power (E/dE>6000) horizontally and spatial imaging vertically. Two arrays will measure T(i) and both poloidal and toroidal rotation velocity profiles. The measurement of many spatial chords permits tomographic inversion for the inference of local parameters. The instrument design, predictions of performance, and results from C-Mod are presented.
Oshagh, M; Boué, G; Montalto, M; Santos, N C; Bonfils, X; Haghighipour, N
2012-01-01
We present an improved version of SOAP (Boisse et al. 2012) named "SOAP-T", which can generate the radial velocity variations and light-curves for systems consisting of a rotating spotted star with a transiting planet. This tool can be used to study the anomalies inside transit light-curves and the Rossiter-McLaughlin effect, to better constrain the orbital configuration and properties of planetary systems and active zones of their host stars. Tests of the code are presented to illustrate its performance and to validate its capability when compared with analytical models and real data. Finally, we apply SOAP-T to the active star, HAT-P-11, observed by the NASA Kepler space telescope and use this system to discuss the capability of this tool in analyzing light-curves for the cases where the transiting planet overlaps with the star's spots.
Oshagh, M.; Boisse, I.; Boué, G.; Montalto, M.; Santos, N. C.; Bonfils, X.; Haghighipour, N.
2013-01-01
We present an improved version of SOAP named "SOAP-T", which can generate the radial velocity variations and light curves for systems consisting of a rotating spotted star with a transiting planet. This tool can be used to study the anomalies inside transit light curves and the Rossiter-McLaughlin effect, to better constrain the orbital configuration and properties of planetary systems and the active zones of their host stars. Tests of the code are presented to illustrate its performance and to validate its capability when compared with analytical models and real data. Finally, we apply SOAP-T to the active star, HAT-P-11, observed by the NASA Kepler space telescope and use this system to discuss the capability of this tool in analyzing light curves for the cases where the transiting planet overlaps with the star's spots. The tool's public interface is available at http://www.astro.up.pt/resources/soap-t/
A Rotating Arc Gap Switch and its Arc Velocity Characteristics%旋转电弧开关及其电弧运动速度特性
郭锐; 何俊佳; 赵纯; 陈立学; 潘坦
2011-01-01
为满足脉冲功率技术对闭合开关高电压、大电流、商电荷转移量、电极烧蚀小、寿命长的要求,设计了一种轴向磁场控制的旋转电弧开关.利用有限元软件分析开关间隙中驱弧磁场的位形及大小,得到间隙中磁感应强度与开关结构参数及电流大小的关系.采用B-dot探针测量电弧的旋转速度.实验电源为时序放电回路,在开关上得到近似梯形状的电流波形,实验中电流为18～72 kA,磁感应强度为0.104～0.628T.通过改变上下线圈的匝数,得到在不同驱弧磁场下电弧的运动速度,并与其他旋转电弧开关的运动速度进行比较.对实验数据进行拟合,可知电弧运动速度与间隙中的轴向磁感应强度大小成指数关系.该关系表明,所设计的开关中,电弧运动速度可以由间隙中的驱弧磁场惟一确定,这与外部磁场驱弧方式相比有很大的区别.%A rotating arc gap switch controlled by axial magnetic field was designed and built to meet the needs of high voltage, high current, large charge transfers, slight electrode erosion and long lifetime. The magnetic field distribution in the gap was analyzed by ANSYS. The relationship between magnetic flux density in the gap and switch geometry and arc current was obtained. B-dot probes were employed to measure the arc rotating velocity. The current was trapezoid-like waveform and generated by a time-sequence discharge power supply. The current was in the range of 18～72 kA and magnetic flux density was 0.104～0.628T. The arc velocity in different magnitude of magnetic flux density was obtained by changing the coil number and the results were compared with other rotating arc gap switches. The arc velocity has exponent relation to the axial magnetic field by fitting the experimental data. The results show that the arc velocity in this kind of switch is individually determined by axial magnetic field. It is significant different from other rotating arc
Zhu, Ling; Watkins, Laura L; Posti, Lorenzo
2016-01-01
We present a new discrete chemo-dynamical axisymmetric modeling technique, which we apply to the dwarf spheroidal galaxy Sculptor. The major improvement over previous Jeans models is that realistic chemical distributions are included directly in the dynamical modelling of the discrete data. This avoids loss of information due to spatial binning and eliminates the need for hard cuts to remove contaminants and to separate stars based on their chemical properties. Using a combined likelihood in position, metallicity and kinematics, we find that our models naturally separate Sculptor stars into a metal-rich and a metal-poor population. Allowing for non-spherical symmetry, our approach provides a central slope of the dark matter density of $\\gamma = 0.5 \\pm 0.3$. The metal-rich population is nearly isotropic (with $\\beta_r^{red} = 0.0\\pm0.1$) while the metal-poor population is tangentially anisotropic (with $\\beta_r^{blue} = -0.2\\pm0.1$) around the half light radius of $0.26$ kpc. A weak internal rotation of the m...
Cloutier, Ryan; Menou, Kristen; Delfosse, Xavier; Dumusque, Xavier; Artigau, Étienne
2016-01-01
M-dwarfs are known to commonly host high-multiplicity planetary systems. Therefore M-dwarf planetary systems with a known transiting planet are expected to contain additional small planets ($r_p \\le 4$ R$_{\\oplus}$, $m_p \\lesssim 20$ M$_{\\oplus}$) that are not seen in transit. In this study we investigate the effort required to detect such planets using precision velocimetry around the sizable subset of M-dwarfs which are slowly rotating ($P_{\\mathrm{rot}} \\gtrsim 40$ days) and hence more likely to be inactive. We focus on the test case of GJ 1132. Specifically, we perform a suite of Monte-Carlo simulations of the star's radial velocity signal featuring astrophysical contributions from stellar jitter due to rotationally modulated active regions and keplarian signals from the known transiting planet and hypothetical additional planets not seen in transit. We then compute the detection completeness of non-transiting planets around GJ 1132 and consequently estimate the number of RV measurements required to detec...
Cloutier, Ryan; Doyon, René; Menou, Kristen; Delfosse, Xavier; Dumusque, Xavier; Artigau, Étienne
2017-01-01
M-dwarfs are known to commonly host high-multiplicity planetary systems. Therefore, M-dwarf planetary systems with a known transiting planet are expected to contain additional small planets (rp ≤ 4 R⊕, mp ≲ 20 M⊕) that are not seen in transit. In this study, we investigate the effort required to detect such planets using precision velocimetry around the sizable subset of M-dwarfs that are slowly rotating (Prot ≳ 40 days), and hence more likely to be inactive. We focus on the test case of GJ 1132. Specifically, we perform a suite of Monte-Carlo simulations of the star’s radial velocity signal, featuring astrophysical contributions from stellar jitter due to rotationally modulated active regions, as well as Keplerian signals from the known transiting planet and hypothetical additional planets not seen in transit. We then compute the detection completeness of non-transiting planets around GJ 1132 and consequently estimate the number of RV measurements required to detect those planets. We show that, with 1 m s‑1 precision per measurement, only ∼50 measurements are required to achieve a 50% detection completeness for all non-transiting planets in the system, as well as planets that are potentially habitable. Throughout this work, we advocate the use of Gaussian process regression as an effective tool for mitigating the effects of stellar jitter including stars with high activity. Given that GJ 1132 is representative of a large population of slowly rotating M-dwarfs, we conclude with a discussion of how our results may be extended to other systems with known transiting planets, such as those that will be discovered with TESS.
Mamon, Gary A; Murante, Giuseppe
2010-01-01
When clusters of galaxies are viewed in projection, one cannot avoid picking up foreground/background interlopers, that lie within the virial cone (VC), but outside the virial sphere. Structural and kinematic deprojection equations are not known for an expanding Universe, where the Hubble flow (HF) stretches the line-of-sight distribution of velocities. We analyze 93 mock relaxed clusters, built from a cosmological simulation. The stacked mock cluster is well fit by an m=5 Einasto DM density profile, with velocity anisotropy (VA) close to the Mamon-Lokas model with anisotropy radius equal to that of density slope -2. The surface density of interlopers is nearly flat out to the virial radius, while their velocity distribution shows a dominant gaussian cluster-outskirts component and a flat field component. This distribution of interlopers in PPS is nearly universal in mass. A local kappa=2.7 sigma velocity cut returns the line-of-sight velocity dispersion profile (LOSVDP) expected from the NFW density and VA p...
Cambonie, T; Aider, J -L
2013-01-01
Circular flush Jets In Cross-Flow were experimentally studied in a water tunnel using Volumetric Particle Tracking Velocimetry, for a range of jet to cross-flow velocity ratios, r, from 0.5 to 3, jet exit diameters $d$ from 0.8 cm to 1 cm and cross-flow boundary layer thickness delta from 1 to 2.5 cm. The analysis of the 3D mean velocity fields allows for the definition, computation and study of Counter-rotating Vortex Pair trajectories. The influences of r, d and delta were investigated. A new scaling based on momentum ratio r_m taking into account jet and cross-flow momentum distributions is introduced based on the analysis of jet trajectories published in the literature. Using a rigorous scaling quality factor Q to quantify how well a given scaling successfully collapses trajectories, we show that the proposed scaling also improves the collapse of CVP trajectories, leading to a final scaling law for these trajectories.
Raeder, Christian; Fernandez-Fernandez, Jaime; Ferrauti, Alexander
2015-07-01
The aim of this study was to investigate the effects of 6 weeks of medicine ball training (MBT) on throwing velocity, throwing precision, and isokinetic strength of shoulder rotators in competitive female handball players. Twenty-eight players (mean ± SD; age: 20.8 ± 3.3 years, height: 170.5 ± 5.6 cm, body mass: 65.2 ± 8.0 kg) were randomly assigned to an MBT group (TG; n = 15) and a control group (CG; n = 13). TG performed a supervised MBT program, 3 times a week for a total of 6 weeks, focusing on handball-specific movement patterns. Both groups, TG and CG, also conducted a supervised shoulder injury prevention program with elastic tubes, as part of the warm-up, finishing with regular handball throws. Results showed a significant group × time interaction in throwing velocity (p handball players, whereas throwing precision remained unaffected. Medicine ball training exercises seem to be a useful and inexpensive strength training strategy in enhancing functional performance by closely mimicking sport-specific movement activities.
Chin-Sheng Chen
2016-05-01
Full Text Available This paper proposes a novel image alignment algorithm based on rotation-discriminating ring-shifted projection for automatic optical inspection. This new algorithm not only identifies the location of the template image within an inspection image but also provides precise rotation information during the template-matching process by using a novel rotation estimation scheme, the so-called ring-shifted technique. We use a two stage framework with an image pyramid searching technique for realizing the proposed image alignment algorithm; in the first stage, the similarity based on hybrid projection transformation with the image pyramid searching technique is employed for quick selection and location of the candidates in the inspection image. In the second stage, the rotation angle of the object is estimated by a novel ring-shifted technique. The estimation is performed only for the most likely candidate which is the one having the highest similarity in the first stage. The experimental results show that the proposed method provides accurate estimation for template matching with arbitrary rotations and is applicable in various environmental conditions.
Catalogues of radial and rotational velocities of 1253 F-K dwarfs in 13 nearby open clusters
Mermilliod, J.-C.; Mayor, M.; Udry, S.
2009-05-01
Context: We conducted a long-term monitoring of solar-type dwarfs in 13 nearby open clusters, d electronic form. Based on observations collected at the Haute-Provence Observatory (France) and with the Danish 1.54-m at the European Southern Observatory, La Silla, Chile. This reaserch has made use of the WEBDA database, operated at the Institute for Astronomy of the University of Vienna, and of the SIMBAD database, operated at CDS, Strasbourg, France This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. Full Tables 8, 10, and 11 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/498/949
Wu, Cheng-Feng; Huang, Huey-Chu
2015-10-01
The Taiwan Chelungpu Fault Drilling Project (TCDP) drilled a 2-km-deep hole 2.4 km east of the surface rupture of the 1999 Chi-Chi earthquake ( M w 7.6), near the town of Dakeng. Geophysical well logs at the TCDP site were run over depths ranging from 500 to 1,900 m to obtain the physical properties of the fault zones and adjacent damage zones. These data provide good reference material for examining the validity of velocity structures using microtremor array measurement; therefore, we conduct array measurements for a total of four arrays at two sites near the TCDP drilling sites. The phase velocities at frequencies of 0.2-5 Hz are calculated using the frequency-wavenumber ( f- k) spectrum method. Then the S-wave velocity structures are estimated by employing surface wave inversion techniques. The S-wave velocity from the differential inversion technique gradually increases from 1.52 to 2.22 km/s at depths between 585 and 1,710 m. This result is similar to those from the velocity logs, which range from 1.4 km/s at a depth of 597 m to 2.98 km/s at a depth of 1,705 m. The stochastic inversion results are similar to those from the seismic reflection methods and the lithostratigraphy of TCDP-A borehole, comparatively. These results show that microtremor array measurement provides a good tool for estimating deep S-wave velocity structure.
Persaud, P.; Stock, J. M.; Fuis, G. S.; Hole, J. A.; Goldman, M.; Scheirer, D. S.
2014-12-01
We have analyzed explosive shot data from the 2011 Salton Seismic Imaging Project (SSIP) across a 2-D seismic array and 5 profiles in the Coachella Valley to produce a 3-D P-wave velocity model that will be used in calculations of strong ground shaking. Accurate maps of seismicity and active faults rely both on detailed geological field mapping and a suitable velocity model to accurately locate earthquakes. Adjoint tomography of an older version of the SCEC 3-D velocity model shows that crustal heterogeneities strongly influence seismic wave propagation from moderate earthquakes (Tape et al., 2010). These authors improve the crustal model and subsequently simulate the details of ground motion at periods of 2 s and longer for hundreds of ray paths. Even with improvements such as the above, the current SCEC velocity model for the Salton Trough does not provide a match of the timing or waveforms of the horizontal S-wave motions, which Wei et al. (2013) interpret as caused by inaccuracies in the shallow velocity structure. They effectively demonstrate that the inclusion of shallow basin structure improves the fit in both travel times and waveforms. Our velocity model benefits from the inclusion of known location and times of a subset of 126 shots detonated over a 3-week period during the SSIP. This results in an improved velocity model particularly in the shallow crust. In addition, one of the main challenges in developing 3-D velocity models is an uneven stations-source distribution. To better overcome this challenge, we also include the first arrival times of the SSIP shots at the more widely spaced Southern California Seismic Network (SCSN) in our inversion, since the layout of the SSIP is complementary to the SCSN. References: Tape, C., et al., 2010, Seismic tomography of the Southern California crust based on spectral-element and adjoint methods: Geophysical Journal International, v. 180, no. 1, p. 433-462. Wei, S., et al., 2013, Complementary slip distributions
Wakker, BP; vanWoerden, H
1997-01-01
High-velocity clouds (HVCs) consist of neutral hydrogen (HI) at velocities incompatible with a simple model of differential galactic rotation; in practice one uses \\v(LSR)\\ greater than or equal to 90 km/s to define HVCs. This review describes the main features of the sky and velocity distributions,
Live-Axis Turning for the Fabrication of Non-Rotationally Symmetric Optics Project
National Aeronautics and Space Administration — The goal of this proposal is to develop a new method to create Non-Rotationally Symmetric (NRS) surfaces that overcomes the limitations of the current techniques and...
VizieR Online Data Catalog: SDSS-RM project: peak velocities of QSOs (Shen+, 2016)
Shen, Y.; Brandt, W. N.; Richards, G. T.; Denney, K. D.; Greene, J. E.; Grier, C. J.; Ho, L. C.; Peterson, B. M.; Petitjean, P.; Schneider, D. P.; Tao, C.; Trump, J. R.
2017-01-01
The SDSS-RM quasar sample includes 849 broad-line quasars at 0.1SDSS-RM project within the SDSS-III (Eisenstein+ 2011AJ....142...72E) Baryon Oscillation Spectroscopic Survey (BOSS, Dawson+ 2013AJ....145...10D), using the BOSS spectrograph on the 2.5m SDSS telescope. The wavelength coverage of BOSS spectroscopy is ~3650-10400Å, with a spectral resolution of R~2000. (1 data file).
2016-01-01
Purpose The aim of this study was to evaluate and compare tooth surface characteristics in extracted human molars after cervical enamel projections (CEPs) were removed with the use of three rotating instruments. Methods We classified 60 extracted molars due to periodontal lesion with CEPs into grade I, II, or III, according to the Masters and Hoskins’ criteria. Each group contained 20 specimens. Three rotating instruments were used to remove the CEPs: a piezoelectric ultrasonic scaler, a periodontal bur, and a diamond bur. Tooth surface characteristics before and after removal of the projections were then evaluated with scanning electron microscopy (SEM). We analyzed the characteristics of the tooth surfaces with respect to roughness and whether the enamel projections had been completely removed. Results In SEM images, surfaces treated with the diamond bur were smoothest, but this instrument caused considerable harm to tooth structures near the CEPs. The piezoelectric ultrasonic scaler group produced the roughest surface but caused less harm to the tooth structure near the furcation. In general, the surfaces treated with the periodontal bur were smoother than those treated with the ultrasonic scaler, and the periodontal bur did not invade adjacent tooth structures. Conclusions For removal of grade II CEPs, the most effective instrument was the diamond bur. However, in removing grade III projections, the diamond bur can destroy both adjacent tooth structures and the periodontal apparatus. In such cases, careful use of the periodontal bur may be an appropriate substitute. PMID:27127691
The Latest Results from Project NIRRVS: Precise Near Infrared Radial Velocity Surveys
Plavchan, Peter; NIRRVS Collaboration
2016-06-01
We will present the latest results from a prototype PRV survey with CSHELL. With CSHELL at the NASA Infrared Telescope Facility atop Mauna Kea (R~46,000), we have completed a PRV 2.3 micron survey to detect exoplanets around ~30 red, low mass, and young stars. We are able to reach long-term radial velocity dispersions of ~30 m/s on our survey targets. We are following up candidate RV variables, and have confirmed other previously known RV variables. With a spectral grasp of only 5 nm at 2.3 microns, this performance with CSHELL is limited by detector artifacts, and fringing in the data and flatfields. iSHELL will replace CSHELL at IRTF, with first light expected in May 2016. iSHELL is a 1.15-5.4 micron high spectral resolution (R~70,000) immersion grating, cross-dispersed, white pupil spectrograph. With iSHELL we should be able to obtain a precision of less than 5 m/s in the NIR with iSHELL from the improvements in spectral grasp alone.
Mora, A; Merin, B; Solano, E; Montesinos, B; de Winter, D; Eiroa, C; Ferlet, R; Grady, CA; Miranda, LF; Oudmaijer, RD; Palacios, J; Quirrenbach, A; Harris, AW; Rauer, H; Cameron, A; Deeg, HJ; Garzon, F; Penny, A; Schneider, J; Tsapras, Y; Wesselius, PR
2001-01-01
In this paper we present the first comprehensive results extracted from the spectroscopic campaigns carried out by the EXPORT (EXoPlanetary Observational Research Team) consortium. During 1998-1999, EXPORT carried out an intensive observational effort in the framework of the origin and evolution of
Bonte, K.; Jacobs, C.; Robbrecht, E.; de Groof, A.; Berghmans, D.; Poedts, S.
2011-05-01
In the context of space weather forecasting, an automated detection of coronal mass ejections (CMEs) becomes more and more important for efficiently handling a large data flow which is expected from recently-launched and future solar missions. In this paper we validate the detection software package "CACTus" by applying the program to synthetic data from our 3D time-dependent CME simulations instead of observational data. The main strength of this study is that we know in advance what should be detected. We describe the sensitivities and strengths of automated detection, more specific for the CACTus program, resulting in a better understanding of CME detection on one hand and the calibration of the CACTus software on the other hand, suggesting possible improvements of the package. In addition, the simulation is an ideal tool to investigate projection effects on CME velocity measurements.
Radial velocity eclipse mapping of exoplanets
Nikolov, Nikolay
2015-01-01
Planetary rotation rates and obliquities provide information regarding the history of planet formation, but have not yet been measured for evolved extrasolar planets. Here we investigate the theoretical and observational perspective of the Rossiter-McLauglin effect during secondary eclipse (RMse) ingress and egress for transiting exoplanets. Near secondary eclipse, when the planet passes behind the parent star, the star sequentially obscures light from the approaching and receding parts of the rotating planetary surface. The temporal block of light emerging from the approaching (blue-shifted) or receding (red-shifted) parts of the planet causes a temporal distortion in the planet's spectral line profiles resulting in an anomaly in the planet's radial velocity curve. We demonstrate that the shape and the ratio of the ingress-to-egress radial velocity amplitudes depends on the planetary rotational rate, axial tilt and impact factor (i.e. sky-projected planet spin-orbital alignment). In addition, line asymmetrie...
赵颖; 朱兴望; 曲世祥; 陈堃
2016-01-01
Background: Pebble Bed Reactor (PBR), most often used in Generation IV high-temperature gas-cooled nuclear reactor, employs pebble-shaped fuel elements. As pebbles flow through the reactor, they will slide and rotate against each other and the wall, causing generation of graphite dust.Purpose:This study aims to investigate the rotation angles and angular velocities of pebble-shaped fuel elements (PSFE). Methods: The rotation angle and angular velocity were studied by using a simulated transparent cylinder to replace the reactor core. A pebble-shaped detection system is employed to test the angular velocities and accumulated rotation angles of PSFEs with wireless interface. The generation of graphite particles by rotational abrasion was also studied.Results:The experimental results show that the initial seeding position has influence on rotation angles and angular velocities. The distribution of rotation angles and angular velocities from the center to the wall can be described as an inverted V-type distribution. The calculation results show that wear mass by rotation accounts for 11%?27% of the total graphite dust.Conclusion: Sliding abrasion is stronger than rotation abrasion in general, graphite generation tends to be overestimated if we only take sliding abrasion into consideration and ignore rotation abrasion.%球床堆采用球形燃料元件,其在循环过程中存在滚动磨损以及滑动磨损并产生石墨粉尘.本文借助一种球形无线探测系统量化了角速度及累计旋转角度,并量化了滚动磨损对石墨粉尘产生的影响.实验结果表明,累计旋转角度和角速度与初始径向位置有关,随着初始径向位置由里向外,呈V字型分布,与仓筒边壁接触的球累计旋转角度和角速度远大于其他位置,边壁滚动效应显著.计算结果表明,滚动磨损对石墨粉尘产生量的贡献在11%?27%,且靠近仓筒边壁处该百分比高于其他位置,边壁效应明显.一般情况下,滚动磨
Naab, T; Emsellem, E; Cappellari, M; Krajnovic, D; McDermid, R M; Alatalo, K; Bayet, E; Blitz, L; Bois, M; Bournaud, F; Bureau, M; Crocker, A; Davies, R L; Davis, T A; de Zeeuw, P T; Duc, P -A; Hirschmann, M; Johansson, P H; Khochfar, S; Kuntschner, H; Morganti, R; Oosterloo, T; Sarzi, M; Scott, N; Serra, P; van de Ven, G; Weijmans, A; Young, L M
2013-01-01
We present a detailed two-dimensional stellar dynamical analysis of a sample of 44 cosmological hydrodynamical simulations of individual central galaxies and their satellites. Kinematic maps of the stellar line-of-sight velocity, velocity dispersion, and higher-order Gauss-Hermite moments $h_3$ and $h_4$ are constructed for each central galaxy and for the most massive satellites. The amount of rotation is quantified using the $\\lambda_{\\mathrm{R}}$-parameter. The velocity, velocity dispersion, $h_3$, and $h_4$ fields of the simulated galaxies show a diversity similar to observed kinematic maps of early-type galaxies in the ATLAS$^{\\rm{3D}}$ survey. This includes fast (regular), slow, and misaligned rotation, hot spheroids with embedded cold disk components as well as galaxies with counter-rotating cores or central depressions in the velocity dispersion. We link the present day kinematic properties to the individual cosmological formation histories of the galaxies. In general, major galaxy mergers have a signi...
A Java Program Generating Barycentric Observer Velocities from JPL Ephemerides
Mathar, Richard J
2016-01-01
This works presents a program which computes velocities of an Earth-bound observatory in the reference frame of the barycenter of the solar system. It feeds from ephemerides files of the Jet Propulsion Laboratory to extract the velocity of the geocenter, optionally with corrections from Earth rotation data of the International Earth Rotation Service, takes a datum (time and geodetic location) of the observer as parameters, and processes these data with the program library of the working group `Standards of Fundamental Astronomy' of the International Astronomical Union. The prospective application of the computed velocities is to subtract their projection onto a pointing direction from observed velocities in a step of data reduction of astronomic radial velocities.
Magnus Fredriksson
2013-12-01
Full Text Available In this paper, a method for utilizing knot information from computed tomography (CT scanning of Scots pine (Pinus sylvestris L. logs was evaluated. A high speed industrial CT scanner is being developed, which will enable scanning of logs in sawmills at production speed. This development calls for the ability to optimize breakdown parameters in a quick manner because there are many decisions to be made and the timeframe for these production decisions is short. One of the important breakdown parameters is in which rotational position to saw a log. The presented method used CT data to create a two-dimensional projection of knot information from a log, in order to minimize the amount of data to analyze. The center of mass of the knot projection relative to the center of the sawing pattern was chosen as the rotational position of the log. The aim was to put large knots on the flat surfaces of the boards, as knots on edge surfaces have a more negative effect on board quality in the sorting rules used in this study. The method was tested by sawing simulation and was compared with the industrial praxis of sawing logs horns down. The results show an increase in board quality and value, albeit for a selected group of Scots pine logs. The method is very sensitive to positioning errors, but it has some potential if sawlog positioning accuracy is improved.
Khorasani Gh
2010-11-01
Full Text Available "n Normal 0 false false false EN-US X-NONE AR-SA MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi;} Background: Proper nasal tip control is a difficult step in rhinoplasty. The aim of this study was to compare the effects of two cartilage modifying methods, Septocolumellar Suture (SCS and Lateral Crural Overlay (LCO, on nasal tip projection and rotation."n"n Methods: In a single-blinded clinical trial, 36 patients who were scheduled for nasal tip deprojection were enrolled. A profile photograph of face was taken from all the patients before and three months post operation. Nasofacial angles, TP:Ln ratio for assessing nasal tip projection, tip columellar angle and nasolabial angles for nasal tip rotation assessment were measured by a computer software. The patients were randomly divided into two groups that underwent open rhinoplasty. "n"n Results: Both the LCO and SCS methods were accompanied by a significant reduction in nasofacial angle and TP:Ln ratio, there was raised nasolabial and rotation angle in comparison to preoperative values. The use of LCO method in comparison to SCS resulted in more increase in the nasolabial angle (11.83±3.05 Vs. 4.56±1.62 degree and Rotation Angle (11.44±3.22 Vs. 1.56±1.04 degree and resulted in more reduction in post-operative TP:Ln ratio in comparison to preoperative measures
Rotations with Rodrigues' Vector
Pina, E.
2011-01-01
The rotational dynamics was studied from the point of view of Rodrigues' vector. This vector is defined here by its connection with other forms of parametrization of the rotation matrix. The rotation matrix was expressed in terms of this vector. The angular velocity was computed using the components of Rodrigues' vector as coordinates. It appears…
Possible Reasons for the Slow Rotation of BF Ori
Shulman, S. G.
2016-03-01
Possible reasons for the very low projected rotation velocity of BF Ori compared to other UX Ori stars are discussed. The hypothesis of a close companion that slows down the star's rotation by a tidal interaction is examined. Based on a theory of synchronization and modern models of evolution, the interaction is calculated numerically for different masses of the companion and values of the semi-major axis. It is shown that in order to obtain the projected velocity observed for BF Ori, the companion must have a mass greater than 0.5M⊙ . Such a large companion should have been discovered observationally. It is suggested that the low rotation velocity of BF Ori is more likely to be related to the distribution of the angular momentum of a protostellar cloud between the angular momentum of the star and the orbital angular momentum of a low-mass companion.
Possibility of the BF Ori rotation slowdown due to the orbital synchronization
Shulman, S. G.
2016-11-01
BF Ori is an UX Ori type star with a very slow projected rotational velocity. We analyzed a possibility of the slowdown due to the synchronization in close binary systems. We hypothesized that BF Ori has a companion and estimated its properties as it might be massive and close enough to make this slowdown possible. The conclusion that the rotational velocity of BF Ori is apparently not a result of the tidal interaction with a low mass companion is made.
Peter F. Newton
2012-01-01
Full Text Available The objectives of this study were to (1 quantitatively summarize the early yield responses of black spruce (Picea mariana (Mill. B.S.P. to forest vegetation management (FVM treatments through a meta-analytical review of the scientific literature, and (2 given (1, estimate the rotational consequences of these responses through model simulation. Based on a fixed-effects meta-analytic approach using 44 treated-control yield pairs derived from 12 experiments situated throughout the Great Lakes—St. Lawrence and Canadian Boreal Forest Regions, the resultant mean effect size (response ratio and associated 95% confidence interval for basal diameter, total height, stem volume, and survival responses, were respectively: 54.7% (95% confidence limits (lower/upper: 34.8/77.6, 27.3% (15.7/40.0, 198.7% (70.3/423.5, and 2.9% (−5.5/11.8. The results also indicated that early and repeated treatments will yield the largest gains in terms of mean tree size and survival. Rotational simulations indicated that FVM treatments resulted in gains in stand-level operability (e.g., reductions of 9 and 5 yr for plantations established on poor-medium and good-excellent site qualities, resp.. The challenge of maintaining coniferous forest cover on recently disturbed sites, attaining statutory-defined free-to-grow status, and ensuring long-term productivity, suggest that FVM will continue to be an essential silvicultural treatment option when managing black spruce plantations.
Wu, Xin-Yi; Ghorui, S. K.; Wang, Long-Jun; Kaneko, K.; Sun, Yang
2017-01-01
We analyze the high-spin structure of the even-even 72-80Kr isotopes using the Projected Shell Model (PSM). With the help of the Pfaffian formulas, we have vigorously extended the quasi-particle (qp) basis of the PSM code and applied in this mass region for the first time. We consider a sufficiently large multi-qp configuration space in order to describe high-spin rotational behavior. The results show that the calculation can reproduce most of the known rotational bands with positive- or negative-parity. Moreover, some side bands appearing in the near-yrast region are predicted. The main structure for each band is discussed in terms of multi-qp configurations. The variations in moment of inertia with spin are explained in terms of successive band crossings among the 2-qp, 4-qp, 6-qp, and 8-qp states. The B (E 2) transition probabilities in these bands are also calculated. To further understand the high-spin behavior of these neutron-deficient nuclei and to confirm predictions of the present work, good high-spin data, especially for B (E 2) transitions, are called for.
Bourda, G
2007-01-01
The "Descartes-Nutation" Project is devoted to the "understanding of the next decimal of precession-nutation, from the theoretical point of view as well as from the observational point of view". In this framework, we made a proposal in order to contribute to the study of (i) the dynamical flattening of the Earth, (ii) the coupling effects of the lunisolar forcing, (iii) the effect of the geophysical fluids on the EOP and (iv) the Nutation observations. We investigate further the links between Earth Orientation and Gravity Field Variations. Indeed, the masses distributions inside the Earth govern the behaviour of the rotation axis in space (precession-nutation) and in the Earth (polar motion), as well as the Earth rotation rate (or equivalently, length of the day). These distributions of masses can be measured by space owing to artificial satellites, the orbitography of which provides the Earth gravity field determination. Then, the temporal variations of the Earth gravity field can be related to the variation...
Su, Wei-Hung; Co, Wei-Ting
2016-06-01
A velocity sensing approach using the fringe projection technique is presented. The moving object is projected with a sinusoidal fringe pattern. A CCD camera located at a different view angle observes the projected fringes on the dynamic object. The long exposure time of the CCD camera makes the fringes blurred by linear motion. The blurred fringes provide additional information to describe the depth displacement, and therefore the velocity vector can be identified. There is no need to take multiple-shot measurements to address the change in 3D positions at a sequence of time. Only one-shot measurement is required. Consequently, there is no need to perform image registration. The full-field approach also makes it possible to simultaneously inspect several objects.
The Atlas3D project - XXVI. HI discs in real and simulated fast and slow rotators
Serra, Paolo; Krajnovic, Davor; Naab, Thorsten; Oosterloo, Tom; Morganti, Raffaella; Cappellari, Michele; Emsellem, Eric; Young, Lisa M; Blitz, Leo; Davis, Timothy A; Duc, Pierre-Alain; Hirschmann, Michaela; Weijmans, Anne-Marie; Alatalo, Katherine; Bayet, Estelle; Bois, Maxime; Bournaud, Frederic; Bureau, Martin; Davies, Roger L; de Zeeuw, P T; Khochfar, Sadegh; Kuntschner, Harald; Lablanche, Pierre-Yves; McDermid, Richard M; Sarzi, Marc; Scott, Nicholas
2014-01-01
One quarter of all nearby early-type galaxies (ETGs) outside Virgo host a disc/ring of HI with size from a few to tens of kpc and mass up to ~1e+9 solar masses. Here we investigate whether this HI is related to the presence of a stellar disc within the host making use of the classification of ETGs in fast and slow rotators (FR/SR). We find a large diversity of HI masses and morphologies within both families. Surprisingly, SRs are detected as often, host as much HI and have a similar rate of HI discs/rings as FRs. Accretion of HI is therefore not always linked to the growth of an inner stellar disc. The weak relation between HI and stellar disc is confirmed by their frequent kinematical misalignment in FRs, including cases of polar and counterrotating gas. In SRs the HI is usually polar. This complex picture highlights a diversity of ETG formation histories which may be lost in the relative simplicity of their inner structure and emerges when studying their outer regions. We find that LCDM hydrodynamical simul...
Planetary Nebula Velocities in the Disk and Bulge of M31
Halliday, C; Carter, D; Douglas, N G; Evans, N W; Irwin, M J; Jackson, Z C; Kuijken, K; Merrett, H R; Merrifield, M R; Quinn, D P; Romanowsky, A J; Wilkinson, M I
2006-01-01
We present radial velocities for a sample of 723 planetary nebulae (PNe) in the disk and bulge of M31, measured using the WYFFOS fibre spectrograph on the William Herschel telescope. Velocities are determined using the [OIII] 5007 Angstrom emission line. Rotation and velocity dispersion are measured to a radius of 50 arcminutes (11.5 kpc), the first stellar rotation curve and velocity dispersion profile for M31 to such a radius. Our kinematics are consistent with rotational support at radii well beyond the bulge effective radius of 1.4kpc, although our data beyond a radius of 5kpc are limited. We present tentative evidence for kinematic substructure in the bulge of M31 to be studied fully in a later work. This paper is part of an ongoing project to constrain the total mass, mass distribution and velocity anisotropy of the disk, bulge and halo of M31.
RADIAL VELOCITY ECLIPSE MAPPING OF EXOPLANETS
Nikolov, Nikolay; Sainsbury-Martinez, Felix, E-mail: nikolay@astro.ex.ac.uk [Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom)
2015-07-20
Planetary rotation rates and obliquities provide information regarding the history of planet formation, but have not yet been measured for evolved extrasolar planets. Here we investigate the theoretical and observational perspective of the Rossiter–McLaughlin effect during secondary eclipse (RMse) ingress and egress for transiting exoplanets. Near secondary eclipse, when the planet passes behind the parent star, the star sequentially obscures light from the approaching and receding parts of the rotating planetary surface. The temporal block of light emerging from the approaching (blueshifted) or receding (redshifted) parts of the planet causes a temporal distortion in the planet’s spectral line profiles resulting in an anomaly in the planet’s radial velocity curve. We demonstrate that the shape and the ratio of the ingress-to-egress radial velocity amplitudes depends on the planetary rotational rate, axial tilt, and impact factor (i.e., sky-projected planet spin–orbital alignment). In addition, line asymmetries originating from different layers in the atmosphere of the planet could provide information regarding zonal atmospheric winds and constraints on the hot spot shape for giant irradiated exoplanets. The effect is expected to be most-pronounced at near-infrared wavelengths, where the planet-to-star contrasts are large. We create synthetic near-infrared, high-dispersion spectroscopic data and demonstrate how the sky-projected spin axis orientation and equatorial velocity of the planet can be estimated. We conclude that the RMse effect could be a powerful method to measure exoplanet spins.
C. L. Fern
2007-02-01
Full Text Available The wave packets of atmospheric gravity waves were numerically generated, with a given characteristic wave period, horizontal wave length and projection mean wind along the horizontal wave vector. Their projection phase and group velocities along the oblique radar beam (vpr and vgr, with different zenith angle θ and azimuth angle φ, were analyzed by the method of phase- and group-velocity tracing. The results were consistent with the theoretical calculations derived by the dispersion relation, reconfirming the accuracy of the method of analysis. The RTI plot of the numerical wave packets were similar to the striation patterns of the QP echoes from the FAI irregularity region. We propose that the striation range rate of the QP echo is equal to the radial phase velocity vpr, and the slope of the energy line across the neighboring striations is equal to the radial group velocity vgr of the wave packet; the horizontal distance between two neighboring striations is equal to the characteristic wave period τ. Then, one can inversely calculate all the properties of the gravity wave responsible for the appearance of the QP echoes. We found that the possibility of some QP echoes being generated by the gravity waves originated from lower altitudes cannot be ruled out.
The Activity and Rotation Limit in the Hyades
Seemann, U.; Reiners, A.; Seifahrt, A.; Kürster, M.
2011-12-01
We conduct a study of K to M type stars to investigate the activity and the rotation limit in the Hyades. We use a sample of 40 stars in this intermediate-age cluster (≍625 Myr) to probe stellar rotation in the threshold region where stellar activity becomes prevalent. Here we present projected equatorial velocities (vrotsin i) and chromospheric activity measurements (Hα) that indicate the existence of fast rotators in the Hyades at spectral types where also the fraction of stars with Hα emission shows a rapid increase ("Hα limit"). The locus of enhanced rotation (and activity) thus seems to be shifted to earlier types in contrast to what is seen as the rotation limit in field stars. The relation between activity and rotation appears to be similar to the one observed in field stars.
The activity and rotation limit in the Hyades
Seemann, U; Seifahrt, A; Kürster, M
2010-01-01
We conduct a study of K to M type stars to investigate the activity and the rotation limit in the Hyades. We use a sample of 40 stars in this intermediate-age cluster (~625 Myr) to probe stellar rotation in the threshold region where stellar activity becomes prevalent. Here we present projected equatorial velocities (vsin i) and chromospheric activity measurements (H{\\alpha}) that indicate the existence of fast rotators in the Hyades at spectral types where also the fraction of stars with H{\\alpha} emission shows a rapid increase ("H{\\alpha} limit"). The locus of enhanced rotation (and activity) thus seems to be shifted to earlier types in contrast to what is seen as the rotation limit in field stars. The relation between activity and rotation appears to be similar to the one observed in fields stars.
Predicted rotation signatures in MHD disc winds and comparison to DG Tau observations
Pesenti, N; Cabrit, S; Ferreira, J; Casse, F; García, P; O'Brien, D
2004-01-01
Motivated by the first detections of rotation signatures in the DG Tau jet (Bacciotti et al. 2002), we examine possible biases affecting the relation between detected rotation signatures and true azimuthal velocity for self-similar MHD disc winds, taking into account projection, convolution as well as excitation gradients effects. We find that computed velocity shifts are systematically smaller than the true underlying rotation curve. When outer slower streamlines dominate the emission, we predict observed shifts increasing with transverse distance to the jet axis, opposite to the true rotation profile. Determination of the full transverse rotation profile thus requires high angular resolution observations ( 50) are ruled out for the medium-velocity component in the DG Tau jet.
Predicted rotation signatures in MHD disc winds and comparison to DG Tau observations.
Pesenti, N.; Dougados, C.; Cabrit, S.; Ferreira, J.; Casse, F.; Garcia, P.; O'Brien, D.
2004-03-01
Motivated by the first detections of rotation signatures in the DG Tau jet (Bacciotti et al. \\cite{bacciotti2002}), we examine possible biases affecting the relation between detected rotation signatures and true azimuthal velocity for self-similar MHD disc winds, taking into account projection, convolution as well as excitation gradients effects. We find that computed velocity shifts are systematically smaller than the true underlying rotation curve. When outer slower streamlines dominate the emission, we predict observed shifts increasing with transverse distance to the jet axis, opposite to the true rotation profile. Determination of the full transverse rotation profile thus requires high angular resolution observations ( 50) are ruled out for the medium-velocity component in the DG Tau jet.
Fractal Aggregation Under Rotation
WU Feng-Min; WU Li-Li; LU Hang-Jun; LI Qiao-Wen; YE Gao-Xiang
2004-01-01
By means of the Monte Carlo simulation, a fractal growth model is introduced to describe diffusion-limited aggregation (DLA) under rotation. Patterns which are different from the classical DLA model are observed and the fractal dimension of such clusters is calculated. It is found that the pattern of the clusters and their fractal dimension depend strongly on the rotation velocity of the diffusing particle. Our results indicate the transition from fractal to non-fractal behavior of growing cluster with increasing rotation velocity, i.e. for small enough angular velocity ω the fractal dimension decreases with increasing ω, but then, with increasing rotation velocity, the fractal dimension increases and the cluster becomes compact and tends to non-fractal.
Fractal Aggregation Under Rotation
WUFeng-Min; WULi-Li; LUHang-Jun; LIQiao-Wen; YEGao-Xiang
2004-01-01
By means of the Monte Carlo simulation, a fractal growth model is introduced to describe diffusion-limited aggregation (DLA) under rotation. Patterns which are different from the classical DLA model are observed and the fractal dimension of such clusters is calculated. It is found that the pattern of the clusters and their fractal dimension depend strongly on the rotation velocity of the diffusing particle. Our results indicate the transition from fractal to non-fractal behavior of growing cluster with increasing rotation velocity, i.e. for small enough angular velocity ω; thefractal dimension decreases with increasing ω;, but then, with increasing rotation velocity, the fractal dimension increases and the cluster becomes compact and tends to non-fractal.
The VLT-FLAMES Tarantula Survey VI: Evidence for rotation of the young massive cluster R136
Hénault-Brunet, V; Evans, C J; Sana, H; Bastian, N; Apellániz, J Maíz; Taylor, W D; Markova, N; Bressert, E; de Koter, A; van Loon, J Th
2012-01-01
Although it has important ramifications for both the formation of star clusters and their subsequent dynamical evolution, rotation remains a largely unexplored characteristic of young star clusters (few Myr). Using multi-epoch spectroscopic data of the inner regions of 30 Doradus in the Large Magellanic Cloud (LMC) obtained as part of the VLT-FLAMES Tarantula Survey, we search for rotation of the young massive cluster R136. From the radial velocities of 36 apparently single O-type stars within a projected radius of 10 pc from the centre of the cluster, we find evidence, at the 95% confidence level, for rotation of the cluster as a whole. We use a maximum likelihood method to fit simple rotation curves to our data and find a typical rotational velocity of ~3 km/s. When compared to the low velocity dispersion of R136, our result suggests that star clusters may form with at least ~20% of the kinetic energy in rotation.
Malavolta, L; Bedin, L R; Sneden, C; Nascimbeni, V; Sommariva, V
2015-01-01
We present a detailed study of the internal kinematics of the Galactic Globular Cluster M 4 (NGC 6121), by deriving the radial velocities from 7250 spectra for 2771 stars distributed from the upper part of the Red Giant Branch down to the Main Sequence. We describe new approaches to determine the wavelength solution from day-time calibrations and to determine the radial velocity drifts that can occur between calibration and science observations when observing with the GIRAFFE spectrograph at VLT. Two techniques to determine the radial velocity are compared, after a qualitative description of their advantages with respect to other commonly used algorithm, and a new approach to remove the sky contribution from the spectra obtained with fibre-fed spectrograph and further improve the radial velocity precision is presented. The average radial velocity of the cluster is $\\langle v \\rangle = 71.08 \\pm 0.08$ km s$^{-1}$ with an average dispersion of $\\mu_{v_c} = 3.97$ km s$^{-1}$. Using the same dataset and the same ...
Scheins, J J; Herzog, H; Shah, N J
2011-03-01
For iterative, fully 3D positron emission tomography (PET) image reconstruction intrinsic symmetries can be used to significantly reduce the size of the system matrix. The precalculation and beneficial memory-resident storage of all nonzero system matrix elements is possible where sufficient compression exists. Thus, reconstruction times can be minimized independently of the used projector and more elaborate weighting schemes, e.g., volume-of-intersection (VOI), are applicable. A novel organization of scanner-independent, adaptive 3D projection data is presented which can be advantageously combined with highly rotation-symmetric voxel assemblies. In this way, significant system matrix compression is achieved. Applications taking into account all physical lines-of-response (LORs) with individual VOI projectors are presented for the Siemens ECAT HR+ whole-body scanner and the Siemens BrainPET, the PET component of a novel hybrid-MR/PET imaging system. Measured and simulated data were reconstructed using the new method with ordered-subset-expectation-maximization (OSEM). Results are compared to those obtained by the sinogram-based OSEM reconstruction provided by the manufacturer. The higher computational effort due to the more accurate image space sampling provides significantly improved images in terms of resolution and noise.
唐俊铨; 田学隆
2011-01-01
剪切池内旋转锥体的角速度是新型锥板式血液粘度仪的主要信息源,其精度取决于光电传感器和齿形盘.分析了光电传感器的点光源特性和齿形盘的周期性摆动及其加工精度导致的角度误差.针对锥体角速度的单调递减特性、角度误差在单转内的随机性及整个测量过程中呈周期性,采用有理三次样条插值算法对角速度误差进行补偿.实验结果表明:该方法可提高角速度的测量精度,降低传感器的生产成本.%The angular velocity of rotating cone in shear-pool is the main information source of a cone-plate blood viscometer,and its precision depends on the photoelectric sensor and fluted disc. The error sources of angular velocity device are analyzed, that is, the pointolite characteristic of photoelectric sensor, and the angular error due to the cyclical swing and the machining inaccuracy of fluted disc. Since the cone angular velocity is monotone decreasing and the angular error is random in one cycle but is cyclical variation during the whole detecting process,a rational cubic spline interpolation algorithm is adopted to decrease the angular error. Experimental results show that this method can improve the precision of angular velocity and reduce the production cost of sensor.
Rotational properties of single and wide binary subdwarf B stars
Geier, S; Edelmann, H; Napiwotzki, R; Morales-Rueda, L
2011-01-01
We measured projected rotational velocities of more than a hundred apparently single sdBs. A comparison is made with sdB stars in binary systems with orbits so wide, that tidal interaction becomes negligible. All of these stars are slow rotators (vsini<10 km/s) with EC 22081-1916 being the only exception. This single star has the highest projected rotational velocity ever measured for an sdB (vsini=163 km/s) and might have been formed by a merger event. The merger of a red-giant core and a low-mass, main-sequence star or substellar object during a common envelope phase fits particularly well with observations. The implications of our results for hot subdwarf formation are briefly discussed.
Shimada, Mitsuhiro; Shimizu, Yoshifumi R
2016-01-01
Recently we have proposed a reliable method to describe the rotational band in a fully microscopic manner. The method has recourse to the configuration-mixing of several cranked mean-field wave functions after the angular-momentum-projection. By applying the method with the Gogny D1S force as an effective interaction, we investigate the moments of inertia of the ground state rotational bands in a number of selected nuclei in the rare earth region. As another application we try to describe, for the first time, the two-neutron aligned band in $^{164}$Er, which crosses the ground state band and becomes the yrast states at higher spins. Fairly good overall agreements with the experimental data are achieved; for nuclei, where the pairing correlations are properly described, the agreements are excellent. This confirms that the previously proposed method is really useful for study of the nuclear rotational motion.
Perinati, E.; Diebold, S.; Kendziorra, E.;
2012-01-01
We report on our activities, currently in progress, aimed at performing accelerator experiments with soft protons and hyper-velocity dust particles. They include tests of different types of X-ray detectors and related components (such as filters) and measurements of scattering of soft protons...... and hyper-velocity dust particles off X-ray mirror shells. These activities have been identified as a goal in the context of a number of ongoing space projects in order to assess the risk posed by environmental radiation and dust and qualify the adopted instrumentation with respect to possible damage...... or performance degradation. In this paper we focus on tests for the Silicon Drift Detectors (SDDs) used aboard the LOFT space mission. We use the Van de Graaff accelerators at the University of T\\"ubingen and at the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg, for soft proton and hyper...
Yeşiloğlu, Nebil; Sarici, Murat; Temiz, Gökhan; Yildiz, Kemalettin; Mersa, Berkan; Filinte, Gaye Taylan
2014-05-01
Nasal tip surgery is one of the most important parts of rhinoplasty to achieve an attractive nose. There are numerous techniques focusing on the correction of nasal tip rotation and projection. In this article, a new cartilage support derived from the cephalic border of lower lateral cartilages is used for the adjustment of tip rotation and projection, whereas improving supratip fullness is presented. Bilaterally harvested cartilage extensions are resembled as bird's wings and dedicated to the wings that were created by the world's first scientist who flew from one continent to another: Hezarfen Ahmed Çelebi. Thirty-two patients who underwent open-approach rhinoplasty operation including the abovementioned method were evaluated retrospectively. After performing conventional steps of open approach rhinoplasty, a wing is created by making a cephalic incision parallel to the lateral crural axis leaving the medial attachment intact and then undermined. Then, the cartilage is turned over the midline bilaterally as it acts like a curb by pulling or releasing the wings to adjust to the desired tip rotation and projection and sutured to the repaired upper lateral cartilage roof. Other 2 types of using these wings were asymmetric suturing one of the wings to help in the redirection of deviated nasal tip (n = 12) and suturing each other at midline to support the overlying skin like a tent with supratip deficiency (n = 7). The authors presented here both esthetic and functional outcomes of Hezarfen wings' method that was used for both nasal tip adjustments and supratip support.
Rotating Ellis Wormholes in Four Dimensions
Kleihaus, Burkhard
2014-01-01
We present rotating wormhole solutions in General Relativity, which are supported by a phantom scalar field. These solutions evolve from the static Ellis wormhole, when the throat is set into rotation. As the rotational velocity increases, the throat deforms until at a maximal value of the rotational velocity, an extremal Kerr solution is encountered. The rotating wormholes attain a finite mass and quadrupole moment. They exhibit ergospheres and possess bound orbits.
Perinati, E; Kendziorra, E; Santangelo, A; Tenzer, C; Jochum, J; Bugiel, S; Srama, R; Del Monte, E; Feroci, M; Rubini, A; Rachevski, A; Zampa, G; Zampa, N; Rashevskaya, I; Vacchi, A; Azzarello, P; Bozzo, E; Herder, J -W den; Zane, S; Brandt, S; Hernanz, M; Leutenegger, M A; Kelley, R L; Kilbourne, C A; Meidinger, N; Strüder, L; Cordier, B; Götz, D; Fraser, G W; Osborne, J P; Dennerl, K; Freyberg, M; Friedrich, P
2012-01-01
We report on our activities, currently in progress, aimed at performing accelerator experiments with soft protons and hyper-velocity dust particles. They include tests of different types of X-ray detectors and related components (such as filters) and measurements of scattering of soft protons and hyper-velocity dust particles off X-ray mirror shells. These activities have been identified as a goal in the context of a number of ongoing space projects in order to assess the risk posed by environmental radiation and dust and qualify the adopted instrumentation with respect to possible damage or performance degradation. In this paper we focus on tests for the Silicon Drift Detectors (SDDs) used aboard the LOFT space mission. We use the Van de Graaff accelerators at the University of T\\"ubingen and at the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg, for soft proton and hyper-velocity dust tests respectively. We present the experimental set-up adopted to perform the tests, status of the activities...
Shen, Yue; Ho, Luis C; Brandt, W N; Denney, Kelly D; Horne, Keith; Jiang, Linhua; Kochanek, Christopher S; McGreer, Ian D; Merloni, Andrea; Peterson, Bradley M; Petitjean, Patrick; Schneider, Donald P; Schulze, Andreas; Strauss, Michael A; Tao, Charling; Trump, Jonathan R; Pan, Kaike; Bizyaev, Dmitry
2015-01-01
We present host stellar velocity dispersion measurements for a sample of 88 broad-line quasars at 0.10.6) from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. High signal-to-noise ratio coadded spectra (average S/N~30 per 69 km/s pixel) from SDSS-RM allowed decomposition of the host and quasar spectra, and measurement of the host stellar velocity dispersions and black hole (BH) masses using the single-epoch (SE) virial method. The large sample size and dynamic range in luminosity (L5100=10^(43.2-44.7) erg/s) lead to the first clear detection of a correlation between SE virial BH mass and host stellar velocity dispersion far beyond the local universe. However, the observed correlation is significantly flatter than the local relation, suggesting that there are selection biases in high-z luminosity-threshold quasar samples for such studies. Our uniform sample and analysis enable an investigation of the redshift evolution of the M-sigma relation free of caveats by comparing different samples...
Energy velocity and group velocity
陈宇
1995-01-01
A new Lagrangian method for studying the relationship between the energy velocity and the group velocity is described. It is proved that under the usual quasistatic electric field, the energy velocity is identical to the group velocity for acoustic waves in anisotropic piezoelectric (or non-piezoelectric) media.
Delph, J.; Hole, J. A.; Fuis, G. S.; Stock, J. M.; Rymer, M. J.
2011-12-01
The Salton Trough is an active rift in southern California in a step-over between the plate-bounding Imperial and San Andreas Faults. In March 2011, the Salton Seismic Imaging Project (SSIP) investigated the rift's crustal structure by acquiring several seismic refraction and reflection lines. One of the densely sampled refraction lines crosses the northern-most Imperial Valley, perpendicular to the strike-slip faults and parallel to a line of small Quaternary rhyolitic volcanoes. The line crosses the obliquely extensional Brawley Seismic Zone and goes through one of the most geothermally productive areas in the United States. Well logs indicate the valley is filled by several kilometers of late Pliocene-recent lacustrine, fluvial, and shallow marine sediment. The 42-km long seismic line was comprised of eleven 110-460 kg explosive shots and receivers at a 100 m spacing. First arrival travel times were used to build a tomographic seismic velocity image of the upper crust. Velocity in the valley increases smoothly from 5 km/s, indicating diagenesis and gradational metamorphism of rift sediments at very shallow depth due to an elevated geotherm. The velocity gradient is much smaller in the relatively low velocity (Chocolate Mountains. The tomographic model shows that the shallow metasedimentary basement as well as the geothermal and volcanic activity seem to be bounded by the sharp western and eastern margins of the Brawley Seismic Zone. At this location, strongly fractured crust allows both hydrothermal and magmatic fluids to rise to the surface in the most rapidly extending portion of the rift basin.
2D/3D velocity model for the high resolution 2D and 3D seismic data from the CO2SINK Ketzin Project
Ivanova, A.; Asch, G.; Lueth, S.; Goetz, J.
2009-04-01
Seismic traveltime inversion, traveltime tomography and seismic reflection techniques have been applied for two dimensional (2D) and three dimensional (3D) data acquired in conjunction with characterization and monitoring aspects at a carbon dioxide (CO2) geological storage site at Ketzin, Germany (the CO2SINK project) (S.Yordkayhun, 2008). A seismic source comparison from the 2D pilot study regarding acquisition parameters have been tested at the side has shown the weight drop source is suitable concerning the signal penetration, frequency content of the data and minimizing time and costs for the 3D data acquisition. For the Ketzin seismic data, the ability to obtain an accurate 2D/3D interval velocity model is limited by the acquisition geometry, source-generated noise and time shifts due to the near-surface effects producing severe distortions in the data. Moreover, these time shifts are comparable to the dominant periods of the reflections and to the size of structures to be imaged. Therefore, a combination of seismic refraction and state-of-the-art processing techniques, including careful static corrections and more accurate velocity analysis, has resulted in key improvements of the images and has allowed new information about the 2D/3D interval velocities. The results from these studies together with borehole information, hydrogeologic models and seismic modeling will be combined into an integrated 2D/3D velocity model. After that a careful 2D/3D depth migration is to be provided. It can be used as a database for the future monitoring program at the site.
Butsky, Iryna; Macciò, Andrea V.; Dutton, Aaron A.; Wang, Liang; Obreja, Aura; Stinson, Greg S.; Penzo, Camilla; Kang, Xi; Keller, Ben W.; Wadsley, James
2016-10-01
We use the NIHAO (Numerical Investigation of Hundred Astrophysical Objects) cosmological simulations to study the effects of galaxy formation on key properties of dark matter (DM) haloes. NIHAO consists of ≈90 high-resolution smoothed particle hydrodynamics simulations that include (metal-line) cooling, star formation, and feedback from massive stars and supernovae, and cover a wide stellar and halo mass range: 106 ≲ M*/M⊙ ≲ 1011(109.5 ≲ Mhalo/M⊙ ≲ 1012.5). When compared to DM-only simulations, the NIHAO haloes have similar shapes at the virial radius, Rvir, but are substantially rounder inside ≈0.1Rvir. In NIHAO simulations, c/a increases with halo mass and integrated star formation efficiency, reaching ˜0.8 at the Milky Way mass (compared to 0.5 in DM-only), providing a plausible solution to the long-standing conflict between observations and DM-only simulations. The radial profile of the phase-space Q parameter (ρ/σ3) is best fit with a single power law in DM-only simulations, but shows a flattening within ≈0.1Rvir for NIHAO for total masses M > 1011 M⊙. Finally, the global velocity distribution of DM is similar in both DM-only and NIHAO simulations, but in the solar neighbourhood, NIHAO galaxies deviate substantially from Maxwellian. The distribution is more symmetric, roughly Gaussian, with a peak that shifts to higher velocities for Milky Way mass haloes. We provide the distribution parameters which can be used for predictions for direct DM detection experiments. Our results underline the ability of the galaxy formation processes to modify the properties of DM haloes.
The rotation of nearby M dwarfs and implications for exoplanet discovery
Newton, Elisabeth R.; Irwin, Jonathan; Charbonneau, David; West, Andrew A.; Berta-Thompson, Zachory K.; Dittmann, Jason
2015-12-01
Stellar rotation and its associated activity signals can mimic the radial velocity signatures of orbiting planets. Rotation is both mass- and age-dependent; and despite the prevalence of low-mass stars, few have measured rotation periods. The MEarth Project is a transiting planet survey looking for Earths and Super Earths around mid-to-late M dwarfs (interfere with the detection of habitable planets around these stars. We present a catalog of photometric rotation periods and non-detections for the 2300 stars that have been observed by MEarth. The MEarth target list comprises the brightest and nearest low-mass stars and is the sample of M dwarfs best suited for the discovery and atmospheric characterization of habitable planets. We highlight the subset that, based on their photometric rotation, is well-suited as targets for the upcoming generation of radial velocity surveys dedicated to low-mass stars, including SPIROU, CARMENES, and HPFS.
袁从万; 王鹏; 刘海国
2011-01-01
采用文献资料法、专家访谈法、三维高速影像解析法和数理统计法，对现阶段我国优秀女子铁饼运动员旋转技术的时空特征进行分析，得出以下结论：重心和铁饼的分速度大小及比例对运动员技术风格的形成有重要影响；在旋转技术完成瞬间，李艳凤和宋爱民的铁饼合速度分别是最大和最小的，不同的是李艳风水平分速度占的比例大，宋爱民垂直分速度占的比例大，孙太凤在左脚单支撑阶段铁饼速度较快，导致腾空和过渡阶段铁饼速度下降；在左脚单支撑阶段，宋爱民右髋的速度最大导致她重心轨迹偏向左，孙太凤最慢的右髋速度和最快的右肩速度使她的重心轨迹偏右；李艳凤在过渡阶段过快的肩关节速度是她获得较快饼速的主要原因之一。在形成最后用力双支撑瞬间，我国运动员的肩轴角速度要大于髋轴，说明我国运动员已经开始最后用力。%This article adopted the methods of literature, expert interview, photography of three dimensional in high speed, and mathematic statistics to analyze the rotation technique of Chinese elite women＇s discus throwers. It has been shown that size and proportion of component velocity of CG and discus have very important influence to form athlete＇ s technique style ; Body -discus system at flight and transition stage is very complex and the most difficulty controllable. System changes in the two stages have the decisive effect to form personal optimum technique; the second and third rotation axis of Chinese athletes have steady velocity transfer. Hip and knees velocity of the second axis decide the style of displacement. The shoulder velocity of third has a close relation to the space - time characteristics of discus.
Butsky, Iryna; Dutton, Aaron A; Wang, Liang; Stinson, Greg S; Penzo, Camilla; Kang, Xi; Keller, Ben W; Wadsley, James
2015-01-01
We show the effect of galaxy formation on the dark matter (DM) distribution across a wide range of halo masses. We focus on how baryon physics changes the dark matter halo shape, the so called "pseudo phase-space density distribution" and the velocity distribution within the virial radius, Rvir and in the solar neighborhood. This study is based on the NIHAO galaxy formation simulations, a large suite of cosmological zoom-in simulations. The galaxies reproduce key properties of observed galaxies, and hence offer unique insight into how baryons change the dark matter morphology and kinematics. When compared to dark matter only simulations, the NIHAO haloes have similar shapes at Rvir, but are substantially rounder inside ~0.1 Rvir. In DM-only simulations the inner halo has a minor-to-major axis ratio of c/a~0.5. In hydro simulations c/a increases with halo mass and integrated star formation efficiency, reaching ~0.8 at the Milky Way mass, reconciling a long-standing conflict between observations and DM only sim...
Manolopoulou, Maria
2016-01-01
We study the possible rotation of cluster galaxies, developing, testing and applying a novel algorithm which identifies rotation, if such does exits, as well as its rotational centre, its axis orientation, rotational velocity amplitude and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte-Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z<~0.1 with member galaxies selected from the SDSS DR10 spectroscopic database. We find that ~35% of our clusters are rotating when using a set of strict criteria, while loosening the criteria we find this fraction increasing to ~48%. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their X-ray isophotal shape and find for those clusters showing rotation that the significance and strength of their...
Sandage, Allan
1999-01-01
A distance-limited subset of the complete flux-limited sample of Sc galaxies in the Revised Shapley-Ames Catalog of Bright Galaxies is isolated by means of separate Spaenhauer diagrams for six individual van den Bergh luminosity class intervals from Sc I+I.2,.3 to Sc III-IV. The distribution functions of kinematic absolute B^0,i_T(220,50) magnitudes and 21 cm line widths, W_20, corrected to edge-on orientation, have been determined for the same six bins of luminosity class. The individual luminosity functions for each luminosity class are bounded on both the bright and faint ends, showing that the present sample includes no dwarf Sc spirals fainter than M(B_T)(220,50)=-18 belonging to luminosity classes I to III-IV, as defined by the regularity of the spiral pattern. Star-forming galaxies with spiral structures as regular as the ones found in these luminosity classes have absolute magnitudes brighter than M_B(H=50)=-18 and 21 cm line widths larger than W_20/sini=2v_rot(max)=165 km s^-1. Furthermore, the 21 cm line-width distributions move toward smaller rotational velocities as the luminosity classes change from I to III, showing that rotation is a principal parameter determining the regularity of the spiral pattern. Whether it is the only parameter awaits a similar investigation for spirals of all luminosity classes along the complete Hubble sequence. In particular, it has not yet been proved that all Im and Sm galaxies, where, by definition, the spiral arms are either lacking or are semichaotic, have absolute magnitudes that are fainter than M_B=-18 and whose 21 cm LWs are smaller than ~165 km s^-1, presumably because of smaller mass than the high-luminosity, regular spirals. The Teerikorpi ``cluster population incompleteness bias'' is demonstrated again. Here, however, as in Papers II-IV of this series, we use field galaxies to show that the slope and zero point of the Tully-Fisher (T-F) relation are systematically incorrect for flux-limited samples, the error
Doltra, Jordi; Lægdsmand, Mette; Olesen, Jørgen E
2014-01-01
in Denmark, differing in soil and climate, and representative of the selected production systems. The CO2 effects were modelled using projected CO2 concentrations for the A1B emission scenario. Crop rotations were irrigated (sandy soil) and unirrigated (sandy loam soil), and all included systems...... rather than single crops for impact assessments. Potato and sugar beet in arable farming and grain maize in pig farming contributed most to the productivity increase in the future scenarios. The highest productivity was obtained in the arable system on the sandy loam soil, with an increase of 20...
Nardetto, N; Fokin, A; Chapellier, E; Pietrzynski, G; Gieren, W; Graczyk, D; Mourard, D
2013-01-01
High-resolution spectroscopy of pulsating stars is a powerful tool to study the dynamical structure of their atmosphere. Lines asymmetry is used to derive the center-of-mass velocity of the star, while a direct measurement of the atmospheric velocity gradient helps determine the projection factor used in the Baade-Wesselink method of distance determination. We aim at deriving the center-of-mass velocity and the projection factor of the beta-Cephei star alpha-Lup. We present HARPS high spectral resolution observations of alpha-Lup. We calculate the first-moment radial velocities and fit the spectral line profiles by a bi-Gaussian to derive line asymmetries. Correlations between the gamma-velocity and the gamma-asymmetry (defined as the average values of the radial velocity and line asymmetry curves respectively) are used to derive the center-of-mass velocity of the star. By combining our spectroscopic determination of the atmospheric velocity gradient with a hydrodynamical modelof the photosphere of the star, ...
Perotti, Jose; Voska, Ned (Technical Monitor)
2002-01-01
This presentation provides an overview of the development of new hurricane wind sensor (Extreme Velocity Wind Sensor) for the Kennedy Space Center (KSC) which is designed to withstand winds of up to three hundred miles an hour. The proposed Extreme Velocity Wind Sensor contains no moveable components that would be exposed to extreme wind conditions. Topics covered include: need for new hurricane wind sensor, conceptual design, software applications, computational fluid dynamic simulations of design concept, preliminary performance tests, and project status.
Krajnovic, Davor; Bacon, R.; Cappellari, Michele; Davies, Roger L.; de Zeeuw, P. T.; Emsellem, Eric; Falcon-Barroso, Jesus; Kuntschner, Harald; McDermid, Richard M.; Peletier, Reynier F.; Sarzi, Marc; van den Bosch, Remco C. E.; van de Ven, Glenn
2008-01-01
We analysed two-dimensional maps of 48 early-type galaxies obtained with the SAURON and OASIS integral-field spectrographs using kinemetry, a generalization of surface photometry to the higher order moments of the line-of-sight velocity distribution (LOSVD). The maps analysed include: reconstructed
Uniformly rotating neutron stars
Boshkayev, Kuantay
2016-01-01
In this chapter we review the recent results on the equilibrium configurations of static and uniformly rotating neutron stars within the Hartle formalism. We start from the Einstein-Maxwell-Thomas-Fermi equations formulated and extended by Belvedere et al. (2012, 2014). We demonstrate how to conduct numerical integration of these equations for different central densities ${\\it \\rho}_c$ and angular velocities $\\Omega$ and compute the static $M^{stat}$ and rotating $M^{rot}$ masses, polar $R_p$ and equatorial $R_{\\rm eq}$ radii, eccentricity $\\epsilon$, moment of inertia $I$, angular momentum $J$, as well as the quadrupole moment $Q$ of the rotating configurations. In order to fulfill the stability criteria of rotating neutron stars we take into considerations the Keplerian mass-shedding limit and the axisymmetric secular instability. Furthermore, we construct the novel mass-radius relations, calculate the maximum mass and minimum rotation periods (maximum frequencies) of neutron stars. Eventually, we compare a...
Experimental observation using particle image velocimetry of inertial waves in a rotating fluid
Messio, Laura; Morize, Cyprien; Rabaud, Marc; Moisy, Frederic [Univ Paris-Sud; Univ Pierre et Marie Curie, CNRS, Orsay (France); Fluides, Automatique et Systemes Thermiques (FAST), Orsay (France)
2008-04-15
Inertial waves generated by a small oscillating disk in a rotating water filled cylinder are observed by means of a corotating particle image velocimetry system. The wave takes place in a stationary conical wavepacket, whose angle aperture depends on the oscillation frequency. Direct visualisation of the velocity and vorticity fields in a plane normal to the rotation axis are presented. The characteristic wavelength is found to be approximately equal to the disk diameter. The classical dispersion relation for plane waves is verified from the radial location of the wavepacket, and from the ellipticity of the projected velocity diagram. (orig.)
Rotation and surface abundance peculiarities in A-type stars
Takeda, Yoichi; Kang, Dong-Il; Lee, Byeong-Cheol; Kim, Kang-Min
2008-01-01
In an attempt of clarifying the connection between the photospheric abundance anomalies and the stellar rotation as well as of exploring the nature of "normal A" stars, the abundances of seven elements (C, O, Si, Ca, Ti, Fe, and Ba) and the projected rotational velocity for 46 A-type field stars were determined by applying the spectrum-fitting method to the high-dispersion spectral data obtained with BOES at BOAO. We found that the peculiarities (underabundances of C, O, and Ca; an overabundance of Ba) seen in slow rotators efficiently decrease with an increase of rotation, which almost disappear at v_e sin i > 100 km s^-1. This further suggests that stars with sufficiently large rotational velocity may retain the original composition at the surface without being altered. Considering the subsolar tendency (by several tenths dex below) exhibited by the elemental abundances of such rapidly-rotating (supposedly normal) A stars, we suspect that the gas metallicity may have decreased since our Sun was born, contra...
Compact rotating cup anemometer
Wellman, J. B.
1968-01-01
Compact, collapsible rotating cup anemometer is used in remote locations where portability and durability are factors in the choice of equipment. This lightweight instrument has a low wind-velocity threshold, is capable of withstanding large mechanical shocks while in its stowed configuration, and has fast response to wind fluctuations.
The Atlas3D project - XIX. The hot-gas content of early-type galaxies: fast versus slow rotators
Sarzi, Marc; Blitz, Leo; Bois, Maxime; Bournaud, Frederic; Bureau, M; Cappellari, Michele; Crocker, Alison F; Davies, Roger L; Davis, Timothy A; de Zeeuw, P T; Duc, Pierre-Alain; Khochfar, Sadegh; Krajnovic, Davor; Kuntschner, Harald; McDermid, Richard M; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M
2013-01-01
For early-type galaxies, the ability to sustain a corona of hot, X-ray emitting gas could have played a key role in quenching their star-formation history. Yet, it is still unclear what drives the precise amount of hot gas around these galaxies. By combining photometric and spectroscopic measurements for the early-type galaxies observed during the Atlas3D integral-field survey with measurements of their X-ray luminosity based on X-ray data of both low and high spatial resolution we conclude that the hot-gas content of early-type galaxies can depend on their dynamical structure. Specifically, whereas slow rotators generally have X-ray halos with luminosity L_X,gas and temperature T values that are in line with what is expected if the hot-gas emission is sustained by the thermalisaton of the kinetic energy carried by the stellar-mass loss material, fast rotators tend to display L_X,gas values that fall consistently below the prediction of this model, with similar T values that do not scale with the stellar kine...
Balajewicz, Maciej; Dowell, Earl
2015-01-01
For a projection-based reduced order model (ROM) to be stable and accurate, the dynamics of the truncated subspace must be taken into account. This paper proposes an approach for stabilizing and enhancing projection-based fluid ROMs in which truncated modes are accounted for \\textit{a priori} via a minimal rotation of the projection subspace. Attention is focused on the full non-linear compressible Navier-Stokes equations in specific volume form as a step toward a more general formulation for problems with generic non-linearities. Unlike traditional approaches, no empirical turbulence modeling terms are required, and consistency between the ROM and the full order model from which the ROM is derived is maintained. Mathematically, the approach is formulated as a quadratic matrix program on the Stiefel manifold. The reproductive as well as predictive capabilities of the method are evaluated on several compressible flow problems, including a problem involving laminar flow over an airfoil with a high angle of atta...
Synergic effects of 10°/s constant rotation and rotating background on visual cognitive processing
He, Siyang; Cao, Yi; Zhao, Qi; Tan, Cheng; Niu, Dongbin
accelerated the early process of visual cognition. There is a synergic effect between the effects of constant low-speed rotation and rotating speed of the background. Under certain conditions, they both served to facilitate the visual cognitive processing, and it had been started at the stage when extrastriate cortex perceiving the visual signal. Under the condition of constant low-speed rotation in higher cognitive load tasks, the rapid rotation of the background enhanced the magnitude of the signal transmission in the visual path, making signal to noise ratio increased and a higher signal to noise ratio is clearly in favor of target perception and recognition. This gave rise to the hypothesis that higher cognitive load tasks with higher top-down control had more power in counteracting the inhibition effect of higher velocity rotation background. Acknowledgements: This project was supported by National Natural Science Foundation of China (No. 30670715) and National High Technology Research and Development Program of China (No.2007AA04Z254).
MARVY: Mars Velocity Sensor Project
National Aeronautics and Space Administration — The successful landing of the large Mars rover Curiosity on August 5, 2012 outlined the increasing complexity of safely landing large rovers on the planet. A precise...
Santos, Leonardo A dos; Nascimento, José-Dias do; Bedell, Megan; Ramírez, Iván; Bean, Jacob L; Asplund, Martin; Spina, Lorenzo; Dreizler, Stefan; Alves-Brito, Alan; Casagrande, Luca
2016-01-01
It is still unclear how common the Sun is when compared to other similar stars in regards to some of its physical properties, such as rotation. Considering that gyrochronology relations are widely used today to estimate ages of stars in the main sequence, and that the Sun is used to calibrate it, it is crucial to assess if these procedures are acceptable. We analyze the rotational velocities -- limited by the unknown rotation axis inclination angle -- of an unprecedented large sample of solar twins in order to study the rotational evolution of Sun-like stars, and assess if the Sun is a typical rotator. We use high-resolution ($R = 115000$) spectra obtained with the HARPS spectrograph and ESO's 3.6 m telescope at La Silla Observatory. The projected rotational velocities for 82 solar twins are estimated by line profile fitting with synthetic spectra. Macroturbulence velocities are inferred from a prescription that accurately reflects their dependence with effective temperature and luminosity of the stars. Our s...
The unexpected diversity of dwarf galaxy rotation curves
Oman, Kyle A; Fattahi, Azadeh; Frenk, Carlos S; Sawala, Till; White, Simon D M; Bower, Richard; Crain, Robert A; Furlong, Michelle; Schaller, Matthieu; Schaye, Joop; Theuns, Tom
2015-01-01
We examine the circular velocity profiles of galaxies in {\\Lambda}CDM cosmological hydrodynamical simulations from the EAGLE and LOCAL GROUPS projects and compare them with a compilation of observed rotation curves of galaxies spanning a wide range in mass. The shape of the circular velocity profiles of simulated galaxies varies systematically as a function of galaxy mass, but shows remarkably little variation at fixed maximum circular velocity. This is especially true for low-mass dark matter-dominated systems, reflecting the expected similarity of the underlying cold dark matter haloes. This is at odds with observed dwarf galaxies, which show a large diversity of rotation curve shapes, even at fixed maximum rotation speed. Some dwarfs have rotation curves that agree well with simulations, others do not. The latter are systems where the inferred mass enclosed in the inner regions is much lower than expected for cold dark matter haloes and include many galaxies where previous work claims the presence of a con...
Solar rotation gravitational moments
A. Ajabshirizadeh
2005-09-01
Full Text Available Gravitational multipole moments of the Sun are still poorly known. Theoretically, the difficulty is mainly due to the differential rotation for which the velocity rate varies both on the surface and with the depth. From an observational point of view, the multipole moments cannot be directly measured. However, recent progresses have been made proving the existence of a strong radial differential rotation in a thin layer near the solar surface (the leptocline. Applying the theory of rotating stars, we will first compute values of J2 and J4 taking into account the radial gradient of rotation, then we will compare these values with the existing ones, giving a more complete review. We will explain some astrophysical outcomes, mainly on the relativistic Post Newtonian parameters. Finally we will conclude by indicating how space experiments (balloon SDS flights, Golf NG, Beppi-Colombo, Gaia... will be essential to unambiguously determine these parameters.
A rotating molecular jet in Orion
Zapata, Luis A; Muders, Dirk; Schilke, Peter; Menten, Karl; Guesten, Rolf
2009-01-01
We present CO(2-1), $^{13}$CO(2-1), CO(6-5), CO(7-6), and SO(6$_5-5_4$) line observations made with the {\\it IRAM 30 m} and {\\it APEX} radiotelescopes and the {\\it Submillimeter Array} toward the highly collimated and extended southwest lobe of the bipolar outflow {\\it Ori-S6} located in the Orion South region. We report, for all these lines, the detection of velocity asymmetries about the flow axis, with velocity differences roughly on the order of 1 km s$^{-1}$ over distances of about 5000 AU, 4 km s$^{-1}$ over distances of about 2000 AU, and close to the source of between 7 and 11 km s$^{-1}$ over smaller scales of about 1000 AU. We interpret these velocity differences as a signature of rotation but also discuss some alternatives which we recognize as unlikely in view of the asymmetries' large downstream continuation. This rotation across the {\\it Ori-S6} outflow is observed out to (projected) distances beyond 2.5 $\\times$ 10$^4$ AU from the flow's presumed origin. Comparison of our large-scale and small-...
Interacting galaxies: co-rotating and counter-rotating systems with tidal tails
Mesa, Valeria; Alonso, Sol; Coldwell, Georgina; Lambas, Diego G
2013-01-01
We analyse interacting galaxy pairs with evidence of tidal features in the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7). The pairs were selected within $z<0.1$ by requiring a projected separation $r_p < 50 \\kpc$ and relative radial velocity $\\Delta V < 500 \\kms$. We complete spectroscopic pairs using galaxies with photometric redshifts considering $\\Delta V_{phot} < 6800 \\kms$, taking into account the mean photometric redshift uncertainty. We classify by visual inspection pairs of spirals into co-rotating and counter-rotating systems. For a subsample of non-AGN galaxies, counter-rotating pairs have larger star formation rates, and a higher fraction of young, star-forming galaxies. These effects are enhanced by restricting to $r_p < 12 \\kpc$. The distributions of $C$, $D_n(4000)$ and $(M_u-M_r)$ for AGN galaxies show that counter-rotating hosts have bluer colours and younger stellar population than the co-rotating galaxies although the relative fractions of Seyfert, Liner, Composite and Am...
STUDYING THE INTERSTELLAR MAGNETIC FIELD FROM ANISOTROPIES IN VELOCITY CHANNELS
Esquivel, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, 04510 México D.F., México (Mexico); Lazarian, A. [Astronomy Department, University of Wisconsin–Madison, 475 N. Charter Street, Madison, WI (United States); Pogosyan, D., E-mail: esquivel@nucleares.unam.mx, E-mail: lazarian@astro.wisc.edu, E-mail: pogosyan@ualberta.ca [Physics Department, University of Alberta, Edmonton, AB (Canada)
2015-11-20
Turbulence in the interstellar medium is anisotropic due to the ubiquitous magnetic fields. This anisotropy depends on the strength of the magnetic field and leaves an imprint on observations of spectral line maps. We use a grid of ideal magnetohydrodynamic simulations of driven turbulence and produce synthetic position–position–velocity maps to study the turbulence anisotropy in velocity channels of various resolutions. We found that the average structure function of velocity channels is aligned with the projection of the magnetic field on the plane of the sky. We also found that the degree of such anisotropy increases with the magnitude of the magnetic field. For thick velocity channels (low velocity resolution), the anisotropy is dominated by density, and the degree of anisotropy in these maps allows one to distinguish sub-Alfvénic and super-Alfvénic turbulence regimes, but it also depends strongly on the sonic Mach number. For thin channels (high velocity resolution), we find that the anisotropy depends less on the sonic Mach number. An important limitation of this technique is that it only gives a lower limit on the magnetic field strength because the anisotropy is related only to the magnetic field component on the plane of the sky. It can, and should, be used in combination with other techniques to estimate the magnetic field, such as the Fermi-Chandrasekhar method, anisotropies in centroids, Faraday rotation measurements, or direct line-of-sight determinations of the field from Zeeman effect observations.
Slowly rotating scalar field wormholes: the second order approximation
Kashargin, P E
2008-01-01
We discuss rotating wormholes in general relativity with a scalar field with negative kinetic energy. To solve the problem, we use the assumption about slow rotation. The role of a small dimensionless parameter plays the ratio of the linear velocity of rotation of the wormhole's throat and the velocity of light. We construct the rotating wormhole solution in the second order approximation with respect to the small parameter. The analysis shows that the asymptotical mass of the rotating wormhole is greater than that of the non-rotating one, and the NEC violation in the rotating wormhole spacetime is weaker than that in the non-rotating one.
Albrecht, Simon; Winn, Joshua N. [Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Setiawan, Johny [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Torres, Guillermo [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Fabrycky, Daniel C. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, Santa Cruz, CA 95064 (United States)
2013-04-10
With observations of the EP Cru system, we continue our series of measurements of spin-orbit angles in eclipsing binary star systems, the BANANA project (Binaries Are Not Always Neatly Aligned). We find a close alignment between the sky projections of the rotational and orbital angular momentum vectors for both stars ({beta}{sub p} = -1. Degree-Sign 8 {+-} 1. Degree-Sign 6 and |{beta}{sub s}| < 17 Degree-Sign ). We also derive precise absolute dimensions and stellar ages for this system. The EP Cru and DI Her systems provide an interesting comparison: they have similar stellar types and orbital properties, but DI Her is younger and has major spin-orbit misalignments, raising the question of whether EP Cru also had a large misalignment at an earlier phase of evolution. We show that tidal dissipation is an unlikely explanation for the good alignment observed today, because realignment happens on the same timescale as spin-orbit synchronization, and the stars in EP Cru are far from synchronization (they are spinning nine times too quickly). Therefore it seems that some binaries form with aligned axes, while other superficially similar binaries are formed with misaligned axes.
High velocity impact experiment (HVIE)
Toor, A.; Donich, T.; Carter, P.
1998-02-01
The HVIE space project was conceived as a way to measure the absolute EOS for approximately 10 materials at pressures up to {approximately}30 Mb with order-of-magnitude higher accuracy than obtainable in any comparable experiment conducted on earth. The experiment configuration is such that each of the 10 materials interacts with all of the others thereby producing one-hundred independent, simultaneous EOS experiments The materials will be selected to provide critical information to weapons designers, National Ignition Facility target designers and planetary and geophysical scientists. In addition, HVIE will provide important scientific information to other communities, including the Ballistic Missile Defense Organization and the lethality and vulnerability community. The basic HVIE concept is to place two probes in counter rotating, highly elliptical orbits and collide them at high velocity (20 km/s) at 100 km altitude above the earth. The low altitude of the experiment will provide quick debris strip-out of orbit due to atmospheric drag. The preliminary conceptual evaluation of the HVIE has found no show stoppers. The design has been very easy to keep within the lift capabilities of commonly available rides to low earth orbit including the space shuttle. The cost of approximately 69 million dollars for 100 EOS experiment that will yield the much needed high accuracy, absolute measurement data is a bargain!
The integration of angular velocity
Boyle, Michael
2016-01-01
A common problem in physics and engineering is determination of the orientation of an object given its angular velocity. When the direction of the angular velocity changes in time, this is a nontrivial problem involving coupled differential equations. Several possible approaches are examined, along with various improvements over previous efforts. These are then evaluated numerically by comparison to a complicated but analytically known rotation that is motivated by the important astrophysical problem of precessing black-hole binaries. It is shown that a straightforward solution directly using quaternions is most efficient and accurate, and that the norm of the quaternion is irrelevant. Integration of the generator of the rotation can also be made roughly as efficient as integration of the rotation. Both methods will typically be twice as efficient naive vector- or matrix-based methods. Implementation by means of standard general-purpose numerical integrators is stable and efficient, so that such problems can ...
Electronic Control Of Slow Rotations
Howard, David E.; Smith, Dennis A.
1992-01-01
Digital/analog circuit controls both angular position and speed of rotation of motor shaft with high precision. Locks angular position of motor to phase of rotation-command clock signal at binary submultiple of master clock signal. Circuit or modified version used to control precisely position and velocity of robotic manipulator, to control translation mechanism of crystal-growing furnace, to position hands of mechanical clock, or to control angular position and rate of rotation in any of large variety of rotating mechanisms.
Bolund, B.; Segergren, E.; Solum, A.; Perers, R.; Lundstroem, L.; Lindblom, A.; Thorburn, K.; Eriksson, M.; Nilsson, K.; Ivanova, I.; Danielsson, O.; Eriksson, S.; Bengtsson, H.; Sjoestedt, E.; Isberg, J.; Sundberg, J.; Bernhoff, H.; Karlsson, K.-E.; Wolfbrandt, A.; Aagren, O.; Leijon, M.
2004-07-01
The discussion regarding renewable energy has gone on for several years. The many ideas and opinions that are presented in this field reflect the great impact future energy production has on people all over the world. This paper describes the new direction of the division of Electricity at Uppsala University after the admission of the new professor, Mats Leijon, in February 2001. Full electromagnetic dynamics can be used in order to improve performance of existing electromagnetic conversion systems and to adapt new technology to the renewable power in nature. These ideas are adopted in wind power, wave power, water-current power, bio-fuelled plants as well as in conventional hydropower, i.e. in every different area were the division is active. This paper is a coarse description of the different activities at the division and alms to highlight their link to each other. Theoretical and experimental results from the different PhD projects are briefly introduced and summarized. (author)
STARE velocities: 2. Evening westward electron flow
M. Uspensky
2004-04-01
Full Text Available Four evening events and one morning event of joint EISCAT/STARE observations during ~22h are considered and the differences between observed STARE line-of-sight (l-o-s velocities and EISCAT electron drift velocities projected onto the STARE beams are studied. We demonstrate that the double-pulse technique, which is currently in use in the STARE routine data handling, typically underestimates the true phase velocity as inferred from the multi-pulse STARE data. We show that the STARE velocities are persistently smaller (1.5–2 times than the EISCAT velocities, even for the multi-pulse data. The effect seems to be more pronounced in the evening sector when the Finland radar observes at large flow angles. We evaluate the performance of the ion-acoustic approach (IAA, Nielsen and Schlegel, 1985 and the off-orthogonal fluid approach (OOFA, Uspensky et al., 2003 techniques to predict the true electron drift velocity for the base event of 12 February 1999. The IAA technique predicts the convection reasonably well for enhanced flows of >~1000m/s, but not so well for slower ones. By considering the EISCAT N(h profiles, we derive the effective aspect angle and effective altitude of backscatter, and use this information for application of the OOFA technique. We demonstrate that the OOFA predictions for the base event are superior over the IAA predictions and thus, we confirm that OOFA predicts the electron velocities reasonably well in the evening sector, in addition to the morning sector, as concluded by Uspensky et al. (2003. To check how "robust" the OOFA model is and how successful it is for convection estimates without the EISCAT support, we analysed three additional evening events and one additional morning event for which information on N(h profiles was intentionally ignored. By accepting the mean STARE/EISCAT velocity ratio of 0.55 and the mean azimuth rotation of 9° (derived for the basic event, we show that the OOFA performs
Dufton, P L; Evans, C J; Brott, I; Cantiello, M; de Koter, A; de Mink, S E; Fraser, M; Hénault-Brunet, V; Howarth, I D; Langer, N; Lennon, D J; Markova, N; Sana, H; Taylor, W D
2011-01-01
We present a spectroscopic analysis of an extremely rapidly rotating late O-type star, VFTS102, observed during a spectroscopic survey of 30 Doradus. VFTS102 has a projected rotational velocity larger than 500\\kms\\ and probably as large as 600\\kms; as such it would appear to be the most rapidly rotating massive star currently identified. Its radial velocity differs by 40\\kms\\ from the mean for 30 Doradus, suggesting that it is a runaway. VFTS102 lies 12 pcs from the X-ray pulsar PSR J0537-6910 in the tail of its X-ray diffuse emission. We suggest that these objects originated from a binary system with the rotational and radial velocities of VFTS102 resulting from mass transfer from the progenitor of PSR J0537-691 and the supernova explosion respectively.
Ouazzani, R-M
2012-01-01
Information about the rotation rate is contained in the low frequency part of power spectra, where signatures of nonuniform surface rotation are expected, as well as in the frequency splittings induced by the internal rotation rate. We wish to figure out whether the differences between the seismic rotation period as determined by a mean rotational splitting, and the rotation period measured from the low frequency peak in the Fourier spectrum (observed for some of CoRoT's targets) can provide constraints on the rotation profile. For uniform moderate rotators,perturbative corrections to second and third order in terms of the rotation angular velocity \\Omega, may mimic differential rotation. We apply our perturbation method to evaluate mode frequencies accurate up to \\Omega^3 for uniform rotation. Effects of latitudinal dependence are calculated in the linear approximation. In \\beta Cephei pulsators models, third order effects become comparable to that of a horizontal shear similar to the solar one at rotation r...
Differentially Rotating White Dwarfs I: Regimes of Internal Rotation
Ghosh, Pranab; Wheeler, J. Craig
2017-01-01
Most viable models of Type Ia supernovae (SNe Ia) require the thermonuclear explosion of a carbon/oxygen white dwarf that has evolved in a binary system. Rotation could be an important aspect of any model for SNe Ia, whether single or double degenerate, with the white dwarf mass at, below, or above the Chandrasekhar limit. Differential rotation is specifically invoked in attempts to account for the apparent excess mass in the super-Chandrasekhar events. Some earlier work has suggested that only uniform rotation is consistent with the expected mechanisms of angular momentum transport in white dwarfs, while others have found pronounced differential rotation. We show that if the baroclinic instability is active in degenerate matter and the effects of magnetic fields are neglected, both nearly uniform rotation and strongly differential rotation are possible. We classify rotation regimes in terms of the Richardson number, Ri. At small values of Ri ≤slant 0.1, we find both the low-viscosity Zahn regime with a nonmonotonic angular velocity profile and a new differential rotation regime for which the viscosity is high and scales linearly with the shear, σ. Employment of Kelvin–Helmholtz viscosity alone yields differential rotation. Large values of Ri ≫ 1 produce a regime of nearly uniform rotation for which the baroclinic viscosity is of intermediate value and scales as {σ }3. We discuss the gap in understanding of the behavior at intermediate values of Ri and how observations may constrain the rotation regimes attained by nature.
THE ROTATION PERIOD OF HD-77581 (VELA X-1)
ZUIDERWIJK, EJ
1995-01-01
The rotation period of HD 77581, supergiant primary in the X-ray binary Vela X-1, is determined from an analysis of selected absorption line profiles. The rotation rate determined from He I line profiles is 0.67 +/- 0.04 times that of the binary angular velocity, corresponding to a rotation velocity
Differential rotation, flares and coronae in A to M stars
Balona, L. A.; Švanda, M.; Karlický, M.
2016-08-01
Kepler data are used to investigate flares in stars of all spectral types. There is a strong tendency across all spectral types for the most energetic flares to occur among the most rapidly rotating stars. Differential rotation could conceivably play an important role in enhancing flare energies. This idea was investigated, but no correlation could be found between rotational shear and the incidence of flares. Inspection of Kepler light curves shows that rotational modulation is very common over the whole spectral type range. Using the rotational light amplitude, the size distribution of starspots was investigated. Our analysis suggests that stars with detectable flares have spots significantly larger than non-flare stars, indicating that flare energies are correlated with the size of the active region. Further evidence of the existence of spots on A stars is shown by the correlation between the photometric period and the projected rotational velocity. The existence of spots indicates the presence of magnetic fields, but the fact that A stars lack coronae implies that surface convection is a necessary condition for the formation of the corona.
Rotation of cometary meteoroids
Capek, David
2014-01-01
The aim of this study is to estimate the rotational characteristics of meteoroids after their release from a comet during normal activity. The results can serve as initial conditions for further analyses of subsequent evolution of rotation in the interplanetary space. A sophisticated numerical model was applied to meteoroids ejected from 2P/Encke comet. The meteoroid shapes were approximated by polyhedrons with several thousands of surface elements, which have been determined by 3D laser scanning method of 36 terrestrial rock samples. These samples came from three distinct sets with different origin and shape characteristics. Two types of gas-meteoroid interactions (diffuse and specular reflection of gas molecules from the surface of meteoroid) and three gas ejection models (leading to very different ejection velocities) were assumed. The rotational characteristics of ejected meteoroid population were obtained by numerical integration of equations of motion with random initial conditions and random shape sele...
Elliptical Galaxies: Rotationally Distorted, After All
Caimmi, R.
2009-12-01
Full Text Available On the basis of earlier investigations onhomeoidally striated Mac Laurin spheroids and Jacobi ellipsoids (Caimmi and Marmo2005, Caimmi 2006a, 2007, different sequences of configurations are defined and represented in the ellipticity-rotation plane, $({sf O}hat{e}chi_v^2$. The rotation parameter, $chi_v^2$, is defined as the ratio, $E_mathrm{rot}/E_mathrm{res}$, of kinetic energy related to the mean tangential equatorial velocity component, $M(overline{v_phi}^2/2$, to kineticenergy related to tangential equatorial component velocity dispersion, $Msigma_{phiphi}^2/2$, andresidual motions, $M(sigma_{ww}^2+sigma_{33}^2/2$.Without loss of generality (above a thresholdin ellipticity values, the analysis is restricted to systems with isotropic stress tensor, whichmay be considered as adjoint configurationsto any assigned homeoidally striated density profile with anisotropic stress tensor, different angular momentum, and equal remaining parameters.The description of configurations in the$({sf O}hat{e}chi_v^2$ plane is extendedin two respects, namely (a from equilibriumto nonequilibrium figures, where the virialequations hold with additional kinetic energy,and (b from real to imaginary rotation, wherethe effect is elongating instead of flattening,with respect to the rotation axis.An application is made toa subsample $(N=16$ of elliptical galaxies extracted from richer samples $(N=25,~N=48$of early type galaxies investigated within theSAURON project (Cappellari et al. 2006, 2007.Sample objects are idealized as homeoidallystriated MacLaurinspheroids and Jacobi ellipsoids, and theirposition in the $({sf O}hat{e}chi_v^2$plane is inferred from observations followinga procedure outlined in an earlier paper(Caimmi 2009b. The position of related adjoint configurations with isotropic stresstensor is also determined. With a singleexception (NGC 3379, slow rotators arecharacterized by low ellipticities $(0lehat{e}<0.2$, low anisotropy parameters$(0ledelta<0
Childs, Peter R N
2010-01-01
Rotating flow is critically important across a wide range of scientific, engineering and product applications, providing design and modeling capability for diverse products such as jet engines, pumps and vacuum cleaners, as well as geophysical flows. Developed over the course of 20 years' research into rotating fluids and associated heat transfer at the University of Sussex Thermo-Fluid Mechanics Research Centre (TFMRC), Rotating Flow is an indispensable reference and resource for all those working within the gas turbine and rotating machinery industries. Traditional fluid and flow dynamics
Effects of Uniform and Differential Rotation on Stellar Pulsations
Lovekin, C. C.; Deupree, R. G.; Clement, M.J.
2008-01-01
We have investigated the effects of uniform rotation and a specific model for differential rotation on the pulsation frequencies of 10 \\Msun\\ stellar models. Uniform rotation decreases the frequencies for all modes. Differential rotation does not appear to have a significant effect on the frequencies, except for the most extreme differentially rotating models. In all cases, the large and small separations show the effects of rotation at lower velocities than do the individual frequencies. Unf...
Triaxial rotation in atomic nuclei
CHEN Yong-Shou; GAO Zao-Chun
2009-01-01
The Projected Shell Model has been developed to include the spontaneously broken axial symmetry so that the rapidly rotating triaxial nuclei can be described microscopically. The theory provides an useful tool to gain an insight into how a triaxial nucleus rotates, a fundamental question in nuclear structure. We shall address some current interests that are strongly associated with the triaxial rotation. A feasible method to explore the problem has been suggested.
On the rotation and pitching of flat plates
Jin, Yaqing; Ji, Sheng; Chamorro, Leonardo P.
2016-11-01
Wind tunnel experiments were performed to characterize the flow-induced rotation and pitching of various flat plates as a function of the thickness ratio, the location of the axis of rotation and turbulence levels. High-resolution telemetry, laser tachometer, and hotwire were used to get time series of the plates motions and the signature of the wake flow at a specific location. Results show that a minor axis offset can induce high-order modes in the plate rotation under low turbulence due to torque unbalance. The spectral decomposition of the flow velocity in the plate wake reveals the existence of a dominating high-frequency mode that corresponds to a static-like vortex shedding occurring at the maximum plate pitch, where the characteristic length scale is the projected width at maximum pitch. The plate thickness ratio shows inverse relation with the angular velocity. A simple model is derived to explain the linear relation between pitching frequency and wind speed. The spectra of the plate rotation show nonlinear relation with the incoming turbulence, and the dominating role of the generated vortices in the plate motions.
Deriving stellar inclination of slow rotators using stellar activity
Dumusque, X., E-mail: xdumusque@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
2014-12-01
Stellar inclination is an important parameter for many astrophysical studies. Although different techniques allow us to estimate stellar inclination for fast rotators, it becomes much more difficult when stars are rotating slower than ∼2-2.5 km s{sup –1}. By using the new activity simulation SOAP 2.0 which can reproduce the photometric and spectroscopic variations induced by stellar activity, we are able to fit observations of solar-type stars and derive their inclination. For HD 189733, we estimate the stellar inclination to be i=84{sub −20}{sup +6} deg, which implies a star-planet obliquity of ψ=4{sub −4}{sup +18} considering previous measurements of the spin-orbit angle. For α Cen B, we derive an inclination of i=45{sub −19}{sup +9}, which implies that the rotational spin of the star is not aligned with the orbital spin of the α Cen binary system. In addition, assuming that α Cen Bb is aligned with its host star, no transit would occur. The inclination of α Cen B can be measured using 40 radial-velocity measurements, which is remarkable given that the projected rotational velocity of the star is smaller than 1.15 km s{sup –1}.
Oscillatory Couette flow of rotating Sisko fluid
T.HAYAT; S.ABELMAN; M.HAMESE
2014-01-01
The oscillatory Couette flow of a magnetohydrodynamic (MHD) Sisko fluid between two infinite non-conducting parallel plates is explored in a rotating frame. The lower plate is fixed, and the upper plate is oscillating in its own plane. Using MATLAB, a numerical solution to the resulting nonlinear system is presented. The influence of the physical parameters on the velocity components is analyzed. It is found that the effect of rotation on the primary velocity is more significant than that on the secondary velocity. Further, the oscillatory character in the flow is also induced by rotation. The considered flow situation behaves inertialess when the Reynolds number is small.
Mechanism of viscosity effect on magnetic island rotation
Mikhailovskii, A.B.; Konovalov, S.V. [Institute of Nuclear Fusion, Russian Research Centre ' Kurchatov Institute' , Kurchatov Sq., 1, Moscow (Russian Federation); Pustovitov, V.D. [National Inst. for Fusion Science, Toki, Gifu (Japan); Tsypin, V.S. [Institute of Physics, University of Sao Paulo, Rua do Matao, Travessa R, SP (Brazil)
2000-04-01
It is shown that plasma viscosity does not influence the magnetic island rotation directly. Nevertheless, it leads to nonstationarity of the plasma velocity. This nonstationarity is the reason of the viscosity effect on island rotation. (author)
Lekner, John
2008-01-01
Any free-particle wavepacket solution of Schrodinger's equation can be converted by differentiations to wavepackets rotating about the original direction of motion. The angular momentum component along the motion associated with this rotation is an integral multiple of [h-bar]. It is an "intrinsic" angular momentum: independent of origin and…
A Silicon Micromachined Gyroscope Driven by the Rotating Carrier Self
Fuxue Zhang; Xu Mao; Yu Liu; Nan Zhang; Wei Zhang
2006-01-01
This paper reported a silicon micromachined gyroscope which is driven by the rotating carrier's angular velocity, the silicon was manufactured by anisotropy etching. The design, fabrication and packing of the sensing element were introduced in the paper. The imitation experimentation and performance test have certificated that the principle of the gyroscope is correct and the gyroscope can be used to sense yawing or pitching angular velocity of the rotating carrier, and the angular velocity of the rotating carrier itself.
A Correlation Between Circumstellar Disks and Rotation in the Upper Scorpius OB Association
Dahm, S E; White, R J
2011-01-01
We present projected rotational velocities for 20 early-type (B8-A9) and 74 late-type (F2-M8) members of the ~5 Myr old Upper Scorpius OB Association derived from high dispersion optical spectra obtained with the High Resolution Echelle Spectrometer (HIRES) on Keck I and the Magellan Inamori Kyocera Echelle (MIKE) on the Magellan Clay telescope. The spectroscopic sample is composed of stars and brown dwarfs with infrared signatures of circumstellar disks, both primordial and debris, and non-excess sources of comparable spectral type. We merge projected rotational velocities, accretion diagnostics, and Spitzer Space Telescope Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) 24 micron photometry to examine the relationship between rotation and circumstellar disks. The rotational velocities are strongly correlated with spectral type, a proxy for mass, such that the median vsini for B8-A9 type stars is: 195(+/-)70 km/s, F2-K4: 37.8(+/-)7.4 km/s, K5-K9: 13.8(+21.3/-8.2) km/s, M0-M5:...
Vassiliev, Dmitri
2017-04-01
We consider an infinite three-dimensional elastic continuum whose material points experience no displacements, only rotations. This framework is a special case of the Cosserat theory of elasticity. Rotations of material points are described mathematically by attaching to each geometric point an orthonormal basis that gives a field of orthonormal bases called the coframe. As the dynamical variables (unknowns) of our theory, we choose the coframe and a density. We write down the general dynamic variational functional for our rotational theory of elasticity, assuming our material to be physically linear but the kinematic model geometrically nonlinear. Allowing geometric nonlinearity is natural when dealing with rotations because rotations in dimension three are inherently nonlinear (rotations about different axes do not commute) and because there is no reason to exclude from our study large rotations such as full turns. The main result of the talk is an explicit construction of a class of time-dependent solutions that we call plane wave solutions; these are travelling waves of rotations. The existence of such explicit closed-form solutions is a non-trivial fact given that our system of Euler-Lagrange equations is highly nonlinear. We also consider a special case of our rotational theory of elasticity which in the stationary setting (harmonic time dependence and arbitrary dependence on spatial coordinates) turns out to be equivalent to a pair of massless Dirac equations. The talk is based on the paper [1]. [1] C.G.Boehmer, R.J.Downes and D.Vassiliev, Rotational elasticity, Quarterly Journal of Mechanics and Applied Mathematics, 2011, vol. 64, p. 415-439. The paper is a heavily revised version of preprint https://arxiv.org/abs/1008.3833
Romano, Marcello
2012-01-01
The exact analytic solution is introduced for the rotational motion of a rigid body having three equal principal moments of inertia and subjected to an external torque vector which is constant for an observer fixed with the body, and to arbitrary initial angular velocity. In the paper a parametrization of the rotation by three complex numbers is used. In particular, the rows of the rotation matrix are seen as elements of the unit sphere and projected, by stereographic projection, onto points on the complex plane. In this representation, the kinematic differential equation reduces to an equation of Riccati type, which is solved through appropriate choices of substitutions, thereby yielding an analytic solution in terms of confluent hypergeometric functions. The rotation matrix is recovered from the three complex rotation variables by inverse stereographic map. The results of a numerical experiment confirming the exactness of the analytic solution are reported. The newly found analytic solution is valid for any...
Note: A helical velocity selector for continuous molecular beams.
Szewc, Carola; Collier, James D; Ulbricht, Hendrik
2010-10-01
We report on a modern realization of the classic helical velocity selector for gas phase particle beams. The device operates stably under high vacuum conditions at rotational frequencies limited only by commercial dc motor capabilities. Tuning the rotational frequency allows selective scanning over a broad velocity band. The width of the selected velocity distributions at full-width-half-maximum is as narrow as a few percent of the selected mean velocity and independent of the rotational speed of the selector. The selector generates low vibrational noise amplitudes comparable to mechanically damped state-of-the-art turbo-molecular pumps and is therefore compatible with vibration sensitive experiments like molecule interferometry.
On the coherent rotation of diffuse matter in numerical simulations of clusters of galaxies
Baldi, Anna Silvia; De Petris, Marco; Sembolini, Federico; Yepes, Gustavo; Lamagna, Luca; Rasia, Elena
2017-03-01
We present a study on the coherent rotation of the intracluster medium and dark matter components of simulated galaxy clusters extracted from a volume-limited sample of the MUSIC project. The set is re-simulated with three different recipes for the gas physics: (i) non-radiative, (ii) radiative without active galactic nuclei (AGN) feedback and (iii) radiative with AGN feedback. Our analysis is based on the 146 most massive clusters identified as relaxed, 57 per cent of the total sample. We classify these objects as rotating and non-rotating according to the gas spin parameter, a quantity that can be related to cluster observations. We find that 4 per cent of the relaxed sample is rotating according to our criterion. By looking at the radial profiles of their specific angular momentum vector, we find that the solid body model is not a suitable description of rotational motions. The radial profiles of the velocity of the dark matter show a prevalence of the random velocity dispersion. Instead, the intracluster medium profiles are characterized by a comparable contribution from the tangential velocity and the dispersion. In general, the dark matter component dominates the dynamics of the clusters, as suggested by the correlation between its angular momentum and the gas one, and by the lack of relevant differences among the three sets of simulations.
Differentially-rotating neutron star models with a parametrized rotation profile
Galeazzi, Filippo; Eriguchi, Yoshiharu
2011-01-01
We analyze the impact of the choice rotation law on equilibrium sequences of relativistic differentially-rotating neutron stars in axisymmetry. The maximum allowed mass for each model is strongly affected by the distribution of angular velocity along the radial direction and by the consequent degree of differential rotation. In order to study the wide parameter space implied by the choice of rotation law, we introduce a functional form that generalizes the so called "j-const. law" adopted in all previous work. Using this new rotation law we reproduce the angular velocity profile of differentially-rotating remnants from the coalescence of binary neutron stars in various 3-dimensional dynamical simulations. We compute equilibrium sequences of differentially rotating stars with a polytropic equation of state starting from the spherically symmetric static case. By analyzing the sequences at constant ratio, T/|W|, of rotational kinetic energy to gravitational binding energy, we find that the parameters that best d...
The Brown Dwarf Kinematics Project (BDKP). IV. Radial Velocities of 85 Late-M and L dwarfs with MagE
Burgasser, Adam J; Gagne, Jonathan; Bochanski, John J; Faherty, Jaqueline K; West, Andrew A; Mamajek, Eric E; Schmidt, Sarah J; Cruz, Kelle L
2015-01-01
Radial velocity measurements are presented for 85 late M- and L-type very low mass stars and brown dwarfs obtained with the Magellan Echellette (MagE) spectrograph. Targets primarily have distances within 20 pc of the Sun, with more distant sources selected for their unusual spectral energy distributions. We achieved precisions of 2--3 km/s, and combined these with astrometric and spectrophotometric data to calculate $UVW$ velocities. Most are members of the thin disk of the Galaxy, and velocity dispersions indicate a mean age of 5.2$\\pm$0.2 Gyr for sources within 20 pc. We find significantly different kinematic ages between late-M dwarfs (4.0$\\pm$0.2 Gyr) and L dwarfs (6.5$\\pm$0.4 Gyr) in our sample that are contrary to predictions from prior simulations. This difference appears to be driven by a dispersed population of unusually blue L dwarfs which may be more prevalent in our local volume-limited sample than in deeper magnitude-limited surveys. The L dwarfs exhibit an asymmetric $U$ velocity distribution w...
Cirrus Crystal Terminal Velocities.
Heymsfield, Andrew J.; Iaquinta, Jean
2000-04-01
Cirrus crystal terminal velocities are of primary importance in determining the rate of transport of condensate from upper- to middle-tropospheric levels and profoundly influence the earth's radiation balance through their effect on the rate of buildup or decay of cirrus clouds. In this study, laboratory and field-based cirrus crystal drag coefficient data, as well as analytical descriptions of cirrus crystal shapes, are used to derive more physically based expressions for the velocities of cirrus crystals than have been available in the past.Polycrystals-often bullet rosettes-are shown to be the dominant crystal types in synoptically generated cirrus, with columns present in varying but relatively large percentages, depending on the cloud. The two critical parameters needed to calculate terminal velocity are the drag coefficient and the ratio of mass to cross-sectional area normal to their fall direction. Using measurements and calculations, it is shown that drag coefficients from theory and laboratory studies are applicable to crystals of the types found in cirrus. The ratio of the mass to area, which is shown to be relatively independent of the number of bullets in the rosette, is derived from an analytic model that represents bullet rosettes containing one to eight bullets in 19 primary geometric configurations. The ratio is also derived for columns. Using this information, a general set of equations is developed to calculate the terminal velocities and masses in terms of the aspect ratio (width divided by length), ice density, and rosette maximum dimension. Simple expressions for terminal velocity and mass as a function of bullet rosette maximum dimension are developed by incorporating new information on bullet aspect ratios.The general terminal velocity and mass relations are then applied to a case from the First International Satellite Cloud Climatology Project (ISCCP) Research Experiment (FIRE) 2, when size spectra from a balloon-borne ice crystal
Optomechanics for absolute rotation detection
Davuluri, Sankar
2016-07-01
In this article, we present an application of optomechanical cavity for the absolute rotation detection. The optomechanical cavity is arranged in a Michelson interferometer in such a way that the classical centrifugal force due to rotation changes the length of the optomechanical cavity. The change in the cavity length induces a shift in the frequency of the cavity mode. The phase shift corresponding to the frequency shift in the cavity mode is measured at the interferometer output to estimate the angular velocity of absolute rotation. We derived an analytic expression to estimate the minimum detectable rotation rate in our scheme for a given optomechanical cavity. Temperature dependence of the rotation detection sensitivity is studied.
THE BROWN DWARF KINEMATICS PROJECT (BDKP). IV. RADIAL VELOCITIES OF 85 LATE-M AND L DWARFS WITH MagE
Burgasser, Adam J. [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States); Logsdon, Sarah E. [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States); Gagné, Jonathan [Institute for Research on Exoplanets (iREx), Université de Montréal, Département de Physique, C.P. 6128 Succ. Centre-ville, Montréal, QC H3C 3J7 (Canada); Bochanski, John J. [Rider University, 2083 Lawrenceville Road, Lawrenceville, NJ 08648 (United States); Faherty, Jaqueline K. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States); West, Andrew A. [Department of Astronomy, Boston University, 725 Commonwealth Avenue Boston, MA 02215 (United States); Mamajek, Eric E. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Schmidt, Sarah J. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Cruz, Kelle L., E-mail: aburgasser@ucsd.edu [Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10034 (United States)
2015-09-15
Radial velocity measurements are presented for 85 late M- and L-type very low-mass stars and brown dwarfs obtained with the Magellan Echellette spectrograph. Targets primarily have distances within 20 pc of the Sun, with more distant sources selected for their unusual spectral energy distributions. We achieved precisions of 2–3 km s{sup −1}, and combined these with astrometric and spectrophotometric data to calculate UVW velocities. Most are members of the thin disk of the Galaxy, and velocity dispersions indicate a mean age of 5.2 ± 0.2 Gyr for sources within 20 pc. We find signficantly different kinematic ages between late-M dwarfs (4.0 ± 0.2 Gyr) and L dwarfs (6.5 ± 0.4 Gyr) in our sample that are contrary to predictions from prior simulations. This difference appears to be driven by a dispersed population of unusually blue L dwarfs which may be more prevalent in our local volume-limited sample than in deeper magnitude-limited surveys. The L dwarfs exhibit an asymmetric U velocity distribution with a net inward flow, similar to gradients recently detected in local stellar samples. Simulations incorporating brown dwarf evolution and Galactic orbital dynamics are unable to reproduce the velocity asymmetry, suggesting non-axisymmetric perturbations or two distinct L dwarf populations. We also find the L dwarfs to have a kinematic age-activity correlation similar to more massive stars. We identify several sources with low surface gravities, and two new substellar candidate members of nearby young moving groups: the astrometric binary DENIS J08230313–4912012AB, a low-probability member of the β Pictoris Moving Group; and 2MASS J15104786–2818174, a moderate-probability member of the 30–50 Myr Argus Association.
Rotations, quaternions, and double groups
Altmann, Simon L
2005-01-01
This self-contained text presents a consistent description of the geometric and quaternionic treatment of rotation operators, employing methods that lead to a rigorous formulation and offering complete solutions to many illustrative problems.Geared toward upper-level undergraduates and graduate students, the book begins with chapters covering the fundamentals of symmetries, matrices, and groups, and it presents a primer on rotations and rotation matrices. Subsequent chapters explore rotations and angular momentum, tensor bases, the bilinear transformation, projective representations, and the g
On the Rotation of Post-T Tauri Stars in Associations
De la Reza, R; Reza, Ramiro de la; Pinzon, Giovanni
2004-01-01
Nearby associations are excellent objects for the study of the initial spin up phase during the PMS evolution. An empirical approach is adopted here to infer their rotations properties and relations to X-ray emission. Three nearby associations are considered. The TW Hya association with an age of 8 Myr, the Beta Pictoris moving group with 12 Myr and a combination of Tucana and Horologium associations (30 Myr). Two low and high rotation modes are considered for each association with stellar masses less than 1.5M and greater than 1.5M respectively. We infer representative equatorial rotation velocities Vo from the observed distribution of projected rotational velocities vsini. A spin up is found for the high rotation mode, whereas in the low rotation mode the Vo do not increase significantly. This insufficient increase of Vo is probably the cause of a decrease of the total mean specific angular momentum for the low mass stars between 8 and 30 Myr. However, for the high mass stars, where a sufficient spin up is ...
Martins, F.; Simón-Díaz, S.; Barbá, R. H.; Gamen, R. C.; Ekström, S.
2017-02-01
Context. Massive star evolution remains only partly constrained. In particular, the exact role of rotation has been questioned by puzzling properties of OB stars in the Magellanic Clouds. Aims: Our goal is to study the relation between surface chemical composition and rotational velocity, and to test predictions of evolutionary models including rotation. Methods: We have performed a spectroscopic analysis of a sample of fifteen Galactic O7-8 giant stars. This sample is homogeneous in terms of mass, metallicity and evolutionary state. It is made of stars with a wide range of projected rotational velocities. Results: We show that the sample stars are located on the second half of the main sequence, in a relatively narrow mass range (25-40 M⊙). Almost all stars with projected rotational velocities above 100 km s-1 have N/C ratios about ten times the initial value. Below 100 km s-1 a wide range of N/C values is observed. The relation between N/C and surface gravity is well reproduced by various sets of models. Some evolutionary models including rotation are also able to consistently explain slowly rotating, highly enriched stars. This is due to differential rotation which efficiently transports nucleosynthesis products and allows the surface to rotate slower than the core. In addition, angular momentum removal by winds amplifies surface braking on the main sequence. Comparison of the surface composition of O7-8 giant stars with a sample of B stars with initial masses about four times smaller reveal that chemical enrichment scales with initial mass, as expected from theory. Conclusions: Although evolutionary models that include rotation face difficulties in explaining the chemical properties of O- and B-type stars at low metallicity, some of them can consistently account for the properties of main-sequence Galactic O stars in the mass range 25-40 M⊙.
The Radial Velocity Experiment (RAVE) : Second data release
Zwitter, T.; Siebert, A.; Munari, U.; Freeman, K. C.; Siviero, A.; Watson, F. G.; Fulbright, J. P.; Wyse, R. F. G.; Campbell, R.; Seabroke, G. M.; Williams, M.; Steinmetz, M.; Bienayme, O.; Gilmore, G.; Grebel, E. K.; Helmi, A.; Navarro, J. F.; Anguiano, B.; Boeche, C.; Burton, D.; Cass, P.; Dawe, J.; Fiegert, K.; Hartley, M.; Russell, K.; Veltz, L.; Bailin, J.; Binney, J.; Bland-Hawthorn, J.; Brown, A.; Dehnen, W.; Evans, N. W.; Fiorentin, P. Re; Fiorucci, M.; Gerhard, O.; Gibson, B.; Kelz, A.; Kuijken, K.; Matijevic, G.; Minchev, I.; Parker, Q. A.; Penarrubia, J.; Quillen, A.; Read, M. A.; Reid, W.; Roeser, S.; Ruchti, G.; Scholz, R. -D.; Smith, M. C.; Sordo, R.; Tolstoi, E.; Tomasella, L.; Vidrih, S.; De Boer, E. Wylie
We present the second data release of the Radial Velocity Experiment ( RAVE), an ambitious spectroscopic survey to measure radial velocities and stellar atmosphere parameters ( temperature, metallicity, surface gravity, and rotational velocity) of up to one million stars using the 6 dF multi-object
Demonstrating the Direction of Angular Velocity in Circular Motion
Demircioglu, Salih; Yurumezoglu, Kemal; Isik, Hakan
2015-01-01
Rotational motion is ubiquitous in nature, from astronomical systems to household devices in everyday life to elementary models of atoms. Unlike the tangential velocity vector that represents the instantaneous linear velocity (magnitude and direction), an angular velocity vector is conceptually more challenging for students to grasp. In physics…
Hydromagnetic Flow between Two Rotating Coaxial Discs
Abdul Aleem Khan
1970-01-01
Full Text Available This paper relates to the steady flow of an electrically incompressible viscous fluid between two parallel coaxial rotating discs with a transverse magnetic field when the discs are rotating in the same direction with the same velocity and there is a source at the centre.
Entropic destruction of a rotating heavy quarkonium
Zhang, Zi-qiang; Ma, Chong; Hou, De-fu; Chen, Gang
2016-01-01
Using the AdS/CFT duality, we study the destruction of a rotating heavy quarkonium due to the entropice force in $\\mathcal{N}=4$ SYM theory and a confining YM theory. It is shown that in both theories increasing the angular velocity leads to decreasing the entropic force. This result implies that the rotating quarkonium dissociates harder than the static case.
The maximum rotation of a galactic disc
Bottema, R
1997-01-01
The observed stellar velocity dispersions of galactic discs show that the maximum rotation of a disc is on average 63% of the observed maximum rotation. This criterion can, however, not be applied to small or low surface brightness (LSB) galaxies because such systems show, in general, a continuously
Linear stability analysis of magnetized jets: the rotating case
Bodo, G; Rossi, P; Mignone, A
2016-01-01
We perform a linear stability analysis of magnetized rotating cylindrical jet flows in the approximation of zero thermal pressure. We focus our analysis on the effect of rotation on the current driven mode and on the unstable modes introduced by rotation. We find that rotation has a stabilizing effect on the current driven mode only for rotation velocities of the order of the Alfv\\'en velocity. Rotation introduces also a new unstable centrifugal buoyancy mode and the "cold" magnetorotational instability. The first mode is analogous to the Parker instability with the centrifugal force playing the role of effective gravity. The magnetorotational instability can be present, but only in a very limited region of the parameter space and is never dominant. The current driven mode is characterized by large wavelenghts and is dominant at small values of the rotational velocity, while the buoyancy mode becomes dominant as rotation is increased and is characterized by small wavelenghts.
Roy, Arpita; Mahadevan, S.; Chakraborty, A.; Pathan, F. M.; Anandarao, B. G.
2010-01-01
The Physical Research Laboratory Advanced Radial-velocity All-sky Search (PARAS) is an efficient fiber-fed cross-dispersed high-resolution echelle spectrograph that will see first light in early 2010. This instrument is being built at the Physical Research laboratory (PRL) and will be attached to the 1.2m telescope at Gurushikhar Observatory at Mt. Abu, India. PARAS has a single-shot wavelength coverage of 370nm to 850nm at a spectral resolution of R 70000 and will be housed in a vacuum chamber (at 1x10-2 mbar pressure) in a highly temperature controlled environment. This renders the spectrograph extremely suitable for exoplanet searches with high velocity precision using the simultaneous Thorium-Argon wavelength calibration method. We are in the process of developing an automated data analysis pipeline for echelle data reduction and precise radial velocity extraction based on the REDUCE package of Piskunov & Valenti (2002), which is especially careful in dealing with CCD defects, extraneous noise, and cosmic ray spikes. Here we discuss the current status of the PARAS project and details and tests of the data analysis procedure, as well as results from ongoing PARAS commissioning activities.
The rotation of Galaxy Clusters
Tovmassian, Hrant M
2015-01-01
The method for detection of the galaxy cluster rotation based on the study of distribution of member galaxies with velocities lower and higher of the cluster mean velocity over the cluster image is proposed. The search for rotation is made for flat clusters with $a/b>1.8$ and BMI type clusters which are expected to be rotating. For comparison there were studied also round clusters and clusters of NBMI type, the second by brightness galaxy in which does not differ significantly from the cluster cD galaxy. Seventeen out of studied 65 clusters are found to be rotating. It was found that the detection rate is sufficiently high for flat clusters, over 60\\%, and clusters of BMI type with dominant cD galaxy, ~ 35%. The obtained results show that clusters were formed from the huge primordial gas clouds and preserved the rotation of the primordial clouds, unless they did not have merging with other clusters and groups of galaxies, in the result of which the rotation has been prevented.
Stellar Rotation in Young Clusters. II. Evolution of Stellar Rotation and Surface Helium Abundance
Huang, W
2005-01-01
We derive the effective temperatures and gravities of 461 OB stars in 19 young clusters by fitting the H-gamma profile in their spectra. We use synthetic model profiles for rotating stars to develop a method to estimate the polar gravity for these stars, which we argue is a useful indicator of their evolutionary status. We combine these results with projected rotational velocity measurements obtained in a previous paper on these same open clusters. We find that the more massive B-stars experience a spin down as predicted by the theories for the evolution of rotating stars. Furthermore, we find that the members of binary stars also experience a marked spin down with advanced evolutionary state due to tidal interactions. We also derive non-LTE-corrected helium abundances for most of the sample by fitting the He I 4026, 4387, 4471 lines. A large number of helium peculiar stars are found among cooler stars with Teff < 23000 K. The analysis of the high mass stars (8.5 solar masses < M < 16 solar masses) s...
The rotation curves of galaxies at intermediate redshift
Vogt, N P; Haynes, M P; Courteau, S; Vogt, Nicole P; Herter, Terry; Haynes, Martha P; Courteau, Stephane
1996-01-01
We have undertaken a pilot project to measure the rotation velocities of spiral galaxies in the redshift range 0.18 < z < 0.4 using high dispersion long slit spectroscopy obtained with the Palomar 5m telescope. One field galaxy and three cluster objects known to have strong emission lines were observed over wavelength ranges covering the redshifted lines of [OII], CaII K, H beta, and [OIII]. Two of the objects show extended line emission that allows the tracing of the rotation curve in one or more lines. A line width similar to that obtained with single dish telescopes for the 21-cm HI line observed in lower redshift galaxies can be derived from the observed H beta, [OII], and [OIII] emission by measuring a characteristic width from the velocity histogram. These moderately distant galaxies have much stronger emission lines than typical low-redshift spirals but they appear to be kinematically similar. Application of the Tully-Fisher relation suggests that the two galaxies with rotation curves are intrins...
CONFRONTING COLD DARK MATTER PREDICTIONS WITH OBSERVED GALAXY ROTATIONS
Obreschkow, Danail; Meyer, Martin; Power, Chris; Staveley-Smith, Lister [International Centre for Radio Astronomy Research (ICRAR), M468, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009 (Australia); Ma, Xiangcheng [The University of Sciences and Technology of China, Centre for Astrophysics, Hefei, Anhui 230026 (China); Zwaan, Martin [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching b. Muenchen (Germany); Drinkwater, Michael J. [School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072 (Australia)
2013-04-01
The rich statistics of galaxy rotations as captured by the velocity function (VF) provide invaluable constraints on galactic baryon physics and the nature of dark matter (DM). However, the comparison of observed galaxy rotations against cosmological models is prone to subtle caveats that can easily lead to misinterpretations. Our analysis reveals full statistical consistency between {approx}5000 galaxy rotations, observed in line-of-sight projection, and predictions based on the standard cosmological model ({Lambda}CDM) at the mass-resolution of the Millennium simulation (H I line-based circular velocities above {approx}50 km s{sup -1}). Explicitly, the H I linewidths in the H I Parkes All Sky Survey (HIPASS) are found to be consistent with those in S{sup 3}-SAX, a post-processed semi-analytic model for the Millennium simulation. Previously found anomalies in the VF can be plausibly attributed to (1) the mass-limit of the Millennium simulation, (2) confused sources in HIPASS, (3) inaccurate inclination measurements for optically faint sources, and (4) the non-detectability of gas-poor early-type galaxies. These issues can be bypassed by comparing observations and models using linewidth source counts rather than VFs. We investigate if and how well such source counts can constrain the temperature of DM.
Fen Wei
2016-01-01
Full Text Available In order to sufficiently capture the useful fault-related information available in the multiple vibration sensors used in rotation machinery, while concurrently avoiding the introduction of the limitation of dimensionality, a new fault diagnosis method for rotation machinery based on supervised second-order tensor locality preserving projection (SSTLPP and weighted k-nearest neighbor classifier (WKNNC with an assembled matrix distance metric (AMDM is presented. Second-order tensor representation of multisensor fused conditional features is employed to replace the prevailing vector description of features from a single sensor. Then, an SSTLPP algorithm under AMDM (SSTLPP-AMDM is presented to realize dimensional reduction of original high-dimensional feature tensor. Compared with classical second-order tensor locality preserving projection (STLPP, the SSTLPP-AMDM algorithm not only considers both local neighbor information and class label information but also replaces the existing Frobenius distance measure with AMDM for construction of the similarity weighting matrix. Finally, the obtained low-dimensional feature tensor is input into WKNNC with AMDM to implement the fault diagnosis of the rotation machinery. A fault diagnosis experiment is performed for a gearbox which demonstrates that the second-order tensor formed multisensor fused fault data has good results for multisensor fusion fault diagnosis and the formulated fault diagnosis method can effectively improve diagnostic accuracy.
Velocity measurement in life combustion systems with high temperature anemometer - HTA
Staudinger, G.; Mory, A.; Pilz, R.; Zimmel, M. [Technische Universitaet Graz, Graz (Austria). Inst. fuer Verfahrenstechnik, Abt. fuer Apparatebau und Mechanische Verfahrenstechnik
1998-12-31
An anemometer was developed which allows to measure velocities in dusty atmospheres at temperatures up to 1200{degree}C in a range between 1 and 40 m/s. The most important features of this vane-anemometer are its frictionless aerostatic bearing and the internal air cooling. The frequency of rotation is detected with a high temperature resistant optical fibre. In the project velocities and velocity-fields were measured in the combustion chambers of a 300 MW{sub el} power plant, a 27 MW{sub th} waste incinerator and in different pilot- and semi-industrial plants. The fuels used were coal, biomass, and municipal waste. 11 figs., 2 tabs.
Statistics of Centroids of Velocity
Esquivel, A
2009-01-01
We review the use of velocity centroids statistics to recover information of interstellar turbulence from observations. Velocity centroids have been used for a long time now to retrieve information about the scaling properties of the turbulent velocity field in the interstellar medium. We show that, while they are useful to study subsonic turbulence, they do not trace the statistics of velocity in supersonic turbulence, because they are highly influenced by fluctuations of density. We show also that for sub-Alfv\\'enic turbulence (both supersonic and subsonic) two-point statistics (e.g. correlation functions or power-spectra) are anisotropic. This anisotropy can be used to determine the direction of the mean magnetic field projected in the plane of the sky.
Searching for IMBHs in Galactic globular clusters through radial velocities of individual stars
Lanzoni, Barbara
2016-02-01
I present an overview of our ongoing project aimed at building a new generation of velocity dispersion profiles ad rotation curves for a representative sample of Galactic globular clusters, from the the radial velocity of hundreds of individual stars distributed at different distances from the cluster center. The innermost portion of the profiles will be used to constrain the possible presence of intermediate-mass black holes. The adopted methodology consists of combining spectroscopic observations acquired with three different instruments at the ESO-VLT: the adaptive-optics assisted, integral field unit (IFU) spectrograph SINFONI for the innermost and highly crowded cluster cores, the multi-IFU spectrograph KMOS for the intermediate regions, and the multi-fiber instrument FLAMES/GIRAFFE-MEDUSA for the outskirts. The case of NGC 6388, representing the pilot project that motivated the entire program, is described in some details.
Protodiscs around Hot Magnetic Rotator Stars
Maheswaran, M
2008-01-01
We develop equations and obtain solutions for the structure and evolution of a protodisc region that is initially formed with no radial motion and super-Keplerian rotation speed when wind material from a hot rotating star is channelled towards its equatorial plane by a dipole-type magnetic field. Its temperature is around $10^7$K because of shock heating and the inflow of wind material causes its equatorial density to increase with time. The centrifugal force and thermal pressure increase relative to the magnetic force and material escapes at its outer edge. The protodisc region of a uniformly rotating star has almost uniform rotation and will shrink radially unless some instability intervenes. In a star with angular velocity increasing along its surface towards the equator, the angular velocity of the protodisc region decreases radially outwards and magnetorotational instability (MRI) can occur within a few hours or days. Viscosity resulting from MRI will readjust the angular velocity distribution of the pro...
Evidence of Wigner rotation phenomena in the beam splitting experiment at the LCLS
Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2016-07-15
A result from particle tracking states that, after a microbunched electron beam is kicked, its trajectory changes while the orientation of the microbunching wavefront remains as before. Experiments at the LCLS showed that radiation in the kicked direction is produced practically without suppression. This could be explained if the orientation of the microbunching wavefront is readjusted along the kicked direction. In previous papers we showed that when the evolution of the electron beam modulation is treated according to relativistic kinematics, the orientation of the microbunching wavefront in the ultrarelativistic asymptotic is always perpendicular to the electron beam velocity. There we refrained from using advanced theoretical concepts to explain or analyze the wavefront rotation. For example, we only hinted to the relation of this phenomenon with the concept of Wigner rotation. This more abstract view of wavefront rotation underlines its elementary nature. The Wigner rotation is known as a fundamental effect in elementary particle physics. The composition of non collinear boosts does not result in a simple boost but, rather, in a Lorentz transformation involving a boost and a rotation, the Wigner rotation. Here we show that during the LCLS experiments, a Wigner rotation was actually directly recorded for the first time with a ultrarelativistic, macroscopic object: an ultrarelativistic electron bunch in an XFEL modulated at nm-scale of the size of about 10 microns. Here we point out the role of Wigner rotation in the analysis and interpretation of experiments with ultrarelativistic, microbunched electron beams in FELs. After the beam splitting experiment at the LCLS it became clear that, in the ultrarelativistic asymptotic, the projection of the microbunching wave vector onto the beam velocity is a Lorentz invariant, similar to the helicity in particle physics.
Locomotion gaits of a rotating cylinder pair
van Rees, Wim M.; Novati, Guido; Koumoutsakos, Petros; Mahadevan, L.
2015-11-01
Using 2D numerical simulations of the Navier-Stokes equations, we demonstrate that a simple pair of rotating cylinders can display a range of locomotion patterns of biological and engineering interest. Steadily counter-rotating the cylinders causes the pair to move akin to a vortex dipole for low rotation rates, but as the rotational velocity is increased the direction of motion reverses. Unsteady rotations lead to different locomotion gaits that resemble jellyfish (for in-phase rotations) and undulating swimmers (for out-of-phase rotations). The small number of parameters for this simple system allows us to systematically map the phase space of these gaits, and allows us to understand the underlying physical mechanisms using a minimal model with implications for biological locomotion and engineered analogs.
Advances in Rotational Seismic Measurements
Pierson, Robert [Applied Technology Associates, Albuquerque, NM (United States); Laughlin, Darren [Applied Technology Associates, Albuquerque, NM (United States); Brune, Robert [Applied Technology Associates, Albuquerque, NM (United States)
2016-10-19
Rotational motion is increasingly understood to be a significant part of seismic wave motion. Rotations can be important in earthquake strong motion and in Induced Seismicity Monitoring. Rotational seismic data can also enable shear selectivity and improve wavefield sampling for vertical geophones in 3D surveys, among other applications. However, sensor technology has been a limiting factor to date. The US Department of Energy (DOE) and Applied Technology Associates (ATA) are funding a multi-year project that is now entering Phase 2 to develop and deploy a new generation of rotational sensors for validation of rotational seismic applications. Initial focus is on induced seismicity monitoring, particularly for Enhanced Geothermal Systems (EGS) with fracturing. The sensors employ Magnetohydrodynamic (MHD) principles with broadband response, improved noise floors, robustness, and repeatability. This paper presents a summary of Phase 1 results and Phase 2 status.
Rotational Diffusion of Particles in Turbulence
Variano, Evan; Meyer, Colin; Byron, Margaret
2011-11-01
We experimentally compare the rotation of spherical and ellipsoidal particles in homogeneous, isotropic turbulence. We find that the particle orientation is well described by a Gaussian diffusion process. This theoretical model would predict that the Lagrangian autocorrelation function for angular velocity is a negative exponential. We measure this Lagrangian autocorrelation function using stereoscopic particle image velocimetry (SPIV) applied to particles whose size is within the inertial subrange of the ambient turbulence. The SPIV resolves 3 velocity components in a nearly 2-dimensional planar volume, which we use as inputs for a nonlinear optimization to quantify the solid body rotation of the particles. This provides us the angular velocity timeseries for individual particles. Through ensemble statistics, we determine the Lagrangian autocorrelation function of angular velocity, from which we can quantify the turbulent rotational diffusivity and its behavior between the extremes of short-term non-Fickian transport and long-term Fickian diffusion.
Rotational diffusion of particles in turbulence
Meyer, Colin R
2013-01-01
Through laboratory measurements, we compare the rotation of spherical and ellipsoidal particles in homogeneous, isotropic turbulence. We find that the particles' angular velocity statistics are well described by an Ornstein-Uhlenbeck (OU) process. This theoretical model predicts that the Lagrangian autocovariance of particles' angular velocity will decay exponentially. We measure the autocovariance using stereoscopic particle image velocimetry (SPIV) applied to particles whose size is within the inertial subrange of the ambient turbulence. The SPIV resolves the motion of points interior to the particles, from which we calculate the solid body rotation of the particles. This provides us with the angular velocity time series for individual particles. Through ensemble statistics, we determine the autocovariance of angular velocity and confirm that it matches the form predicted by an OU process. We can further use the autocovariance curve to quantify the turbulent rotational diffusivity.
Khochfar, Sadegh; Emsellem, Eric; Serra, Paolo; Bois, Maxime; Alatalo, Katherine; Bacon, R.; Blitz, Leo; Bournaud, Frederic; Bureau, M.; Cappellari, Michele; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Krajnovic, Davor; Kuntschner, Harald; Lablanche, Pierre-Yves; McDermid, Richard M.; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Weijmans, Anne-Marie; Young, Lisa M.
2011-01-01
We propose a simple model for the origin of fast and slow rotator early-type galaxies (ETG) within the hierarchical Lambda cold dark matter (Lambda CDM) scenario, that is based on the assumption that the mass fraction of stellar discs in ETGs is a proxy for the specific angular momentum expressed vi
Khochfar, Sadegh; Emsellem, Eric; Serra, Paolo; Bois, Maxime; Alatalo, Katherine; Bacon, R.; Blitz, Leo; Bournaud, Frédéric; Bureau, M.; Cappellari, Michele; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Krajnović, Davor; Kuntschner, Harald; Lablanche, Pierre-Yves; McDermid, Richard M.; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Weijmans, Anne-Marie; Young, Lisa M.
2011-01-01
We propose a simple model for the origin of fast and slow rotator early-type galaxies (ETG) within the hierarchical Λcold dark matter (ΛCDM) scenario, that is based on the assumption that the mass fraction of stellar discs in ETGs is a proxy for the specific angular momentum expressed via λR. Within
Khochfar, Sadegh; Emsellem, Eric; Serra, Paolo; Bois, Maxime; Alatalo, Katherine; Bacon, R.; Blitz, Leo; Bournaud, Frédéric; Bureau, M.; Cappellari, Michele; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Krajnović, Davor; Kuntschner, Harald; Lablanche, Pierre-Yves; McDermid, Richard M.; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Weijmans, Anne-Marie; Young, Lisa M.
2011-01-01
We propose a simple model for the origin of fast and slow rotator early-type galaxies (ETG) within the hierarchical Λcold dark matter (ΛCDM) scenario, that is based on the assumption that the mass fraction of stellar discs in ETGs is a proxy for the specific angular momentum expressed via λR. Within
Destabilization of free convection by weak rotation
Gelfgat, Alexander
2011-01-01
This study offers an explanation of a recently observed effect of destabilization of free convective flows by weak rotation. After studying several models where flows are driven by a simultaneous action of convection and rotation, it is concluded that the destabilization is observed in the cases where centrifugal force acts against main convective circulation. At relatively low Prandtl numbers this counter action can split the main vortex into two counter rotating vortices, where the interaction leads to instability. At larger Prandtl numbers, the counter action of the centrifugal force steepens an unstable thermal stratification, which triggers Rayleigh-B\\'enard instability mechanism. Both cases can be enhanced by advection of azimuthal velocity disturbances towards the axis, where they grow and excite perturbations of the radial velocity. The effect was studied considering a combined convective/rotating flow in a cylinder with a rotating lid and a parabolic temperature profile at the sidewall. Next, explana...
Rotation of cometary meteoroids
Čapek, D.
2014-08-01
Aims: The rotation of meteoroids caused by gas drag during the ejection from a cometary nucleus has not been studied yet. The aim of this study is to estimate the rotational characteristics of meteoroids after their release from a comet during normal activity. Methods: The basic dependence of spin rate on ejection velocity and meteoroid size is determined analytically. A sophisticated numerical model is then applied to meteoroids ejected from the 2P/Encke comet. The meteoroid shapes are approximated by polyhedrons, which have been determined by a 3D laser scanning method of 36 terrestrial rock samples. These samples come from three distinct sets with different origins and characteristics, such as surface roughness or angularity. Two types of gas-meteoroid interactions and three gas ejection models are assumed. The rotational characteristics of ejected meteoroid population are obtained by numerical integration of equations of motion with random initial conditions and random shape selection. Results: It is proved that the results do not depend on a specific set of shape models and that they are applicable to the (unknown) shapes of real meteoroids. A simple relationship between the median of meteoroid spin frequencies bar{f} (Hz), ejection velocities vej (m s-1), and sizes D (m) is determined. For diffuse reflection of gas molecules from meteoroid's surface it reads as bar{f≃ 2× 10-3 v_ej D-0.88}, and for specular reflection of gas molecules from meteoroid's surface it is bar{f≃ 5× 10-3 v_ej D-0.88}. The distribution of spin frequencies is roughly normal on log scale, and it is relatively wide: a 2σ-interval can be described as (0.1, 10)× bar{f}. Most of the meteoroids are non-principal axis rotators. The median angle between angular momentum vector and spin vector is 12°. About 60% of meteoroids rotate in long-axis mode. The distribution of angular momentum vectors is not random. They are concentrated in the perpendicular direction with respect to the gas
Kawata, Takuya; Alfredsson, P. Henrik
2016-07-01
Plane Couette flow under spanwise, anticyclonic system rotation [rotating plane Couette flow (RPCF)] is studied experimentally using stereoscopic particle image velocimetry for different Reynolds and rotation numbers in the fully turbulent regime. Similar to the laminar regime, the turbulent flow in RPCF is characterized by roll cells, however both instantaneous snapshots of the velocity field and space correlations show that the roll cell structure varies with the rotation number. All three velocity components are measured and both the mean flow and all four nonzero Reynolds stresses are obtained across the central parts of the channel. This also allows us to determine the wall shear stress from the viscous stress and the Reynolds stress in the center of the channel, and for low rotation rates the wall shear stress increases with increasing rotation rate as expected. The results show that zero absolute vorticity is established in the central parts of the channel of turbulent RPCF for high enough rotation rates, but also that the mean velocity profile for certain parameter ranges shows an S shape giving rise to a negative velocity gradient in the center of the channel. We find that from an analysis of the Reynolds stress transport equation using the present data there is a transport of the Reynolds shear stress towards the center of the channel, which may then result in a negative mean velocity gradient there.
Martins, F; Barba, R H; Gamen, R C; Ekstroem, S
2016-01-01
Massive star evolution remains only partly constrained. In particular, the exact role of rotation has been questioned by puzzling properties of OB stars in the Magellanic Clouds. Our goal is to study the relation between surface chemical composition and rotational velocity, and to test predictions of evolutionary models including rotation. We have performed a spectroscopic analysis of a sample of fifteen Galactic O7-8 giant stars. This sample is homogeneous in terms of mass, metallicity and evolutionary state. It is made of stars with a wide range of projected rotational velocities. We show that the sample stars are located on the second half of the main sequence, in a relatively narrow mass range (25-40 Msun). Almost all stars with projected rotational velocities above 100 km/s have N/C ratios about ten times the initial value. Below 100 km/s a wide range of N/C values is observed. The relation between N/C and surface gravity is well reproduced by various sets of models. Some evolutionary models including ro...
Scott, Nicholas; Davies, Roger L; Kleijn, Gijs Verdoes; Bois, Maxime; Alatalo, Katherine; Blitz, Leo; Bournaud, Frederic; Bureau, Martin; Crocker, Alison; Davis, Timothy A; de Zeeuw, P T; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnovic, Davor; Kuntschner, Harald; McDermid, Richard M; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M
2012-01-01
We explore the connection between the local escape velocity, V_esc, and the stellar population properties in the ATLAS3D survey, a complete, volume-limited sample of nearby early-type galaxies. We make use of ugriz photometry to construct Multi-Gaussian Expansion models of the surface brightnesses of our galaxies. We are able to fit the full range of surface brightness profiles found in our sample, and in addition we reproduce the results of state-of-the-art photometry in the literature with residuals of 0.04 mags. We utilise these photometric models and SAURON integral-field spectroscopy, combined with Jeans dynamical modelling, to determine the local V_esc derived from the surface brightness. We find that the local V_esc is tightly correlated with the Mgb and Fe5015 linestrengths and optical colours, and anti-correlated with the Hbeta linestrength. In the case of the Mgb and Colour - V_esc relations we find that the relation within individual galaxies follows the global relation between different galaxies. ...
Pareja, M J
2003-01-01
For relativistic stars rotating slowly and differentially with a positive angular velocity, some properties in relation to the positiveness of the rate of rotational dragging and of the angular momentum density are derived. Also, a new proof for the bounds on the rotational mass-energy is given.
Decoding center-out hand velocity from MEG signals during visuomotor adaptation.
Bradberry, Trent J; Rong, Feng; Contreras-Vidal, José L
2009-10-01
During reaching or drawing, the primate cortex carries information about the current and upcoming position of the hand. Researchers have decoded hand position, velocity, and acceleration during center-out reaching or drawing tasks from neural recordings acquired invasively at the microscale and mesoscale levels. Here we report that we can continuously decode information about hand velocity at the macroscale level from magnetoencephalography (MEG) data acquired from the scalp during a center-out drawing task with an imposed hand-cursor rotation. The grand mean (n=5) correlation coefficients (CCs) between measured and decoded velocity profiles were 0.48, 0.40, 0.38, and 0.28 for the horizontal dimension of movement and 0.32, 0.49, 0.56, and 0.23 for the vertical dimension of movement where the order of the CCs indicates pre-exposure, early-exposure, late-exposure, and post-exposure to the hand-cursor rotation. By projecting the sensor contributions to decoding onto whole-head scalp maps, we found that a macroscale sensorimotor network carries information about detailed hand velocity and that contributions from sensors over central and parietal scalp areas change due to adaptation to the rotated environment. Moreover, a 3-D linear estimation of distributed current sources using standardized low-resolution brain electromagnetic tomography (sLORETA) permitted a more detailed investigation into the cortical network that encodes for hand velocity in each of the adaptation phases. Beneficial implications of these findings include a non-invasive methodology to examine the neural correlates of behavior on a macroscale with high temporal resolution and the potential to provide continuous, complex control of a non-invasive neuromotor prosthesis for movement-impaired individuals.
Modeling the Radial Velocity Curve of the Water Vapor Maser in VX UMa
Salter, D. M.; Benson, P. J.; Strelnitski, V. S.
1999-12-01
VX UMa is a unique Mira-type star that demonstrates a triple-peaked spectrum of its 1.35-cm H2O maser emission. We used the high-precision curves of radial velocities of the spectral peaks, obtained by Benson & Little-Marenin from 1988 to 1992, as probes of the kinematics of the masing region. The pronounced periodicity of the radial velocity of the central component, with a period equal to the pulsational period of the optical variations, suggests the involvement of pulsations in the observed excursions of radial velocity. However, the radial velocity of the central spectral component produced by a symmetrical, pulsating spherical layer should be constantly zero. Rotation seems to be the most obvious mechanism to impart a small non-zero component to the central feature. We assume that the bulk of maser radiation originates in the equatorial "belt" around the star and approximate this region as a two-dimensional, rotating and pulsating ring. We found that any combination of rotation and pulsation produces a quadruple peaked, not a triple peaked spectrum. Therefore, some asymmetry in the disk or unequal absorption of the two central peaks by ionized gas (e.g. in the shock responsible for the maser emission) is needed. We demonstrate that one of the central peaks can then undergo periodic changes of its radial velocity with the period of pulsation, as observed. A VLBA experiment that may verify our model is under way. This project was supported by the NSF/REU grant AST-9820555.
Rotational properties of the O-type star population in the Tarantula region
Ramírez-Agudelo, O H; Sana, H; de Koter, A; Sabín-Sanjulían, C; de Mink, S E; Dufton, P L; Gräfener, G; Evans, C J; Herrero, A; Langer, N; Lennon, D J; Apellániz, J Maíz; Markova, N; Najarro, F; Puls, J; Taylor, W D; Vink, J S
2013-01-01
The 30 Doradus (30\\,Dor) region in the Large Magellanic Cloud (also known as the Tarantula Nebula) is the nearest massive starburst region, containing the richest sample of massive stars in the Local Group. It is the best possible laboratory to investigate aspects of the formation and evolution of massive stars. Here, we focus on rotation which is a key parameter in the evolution of these objects. We establish the projected rotational velocity, $v_{e}\\sin i$, distribution of an unprecedented sample of 216 radial velocity constant ($\\rm{\\Delta RV\\, \\leq\\, 20 \\,km s^{-1}}$) O-type stars in 30\\,Dor observed in the framework of the VLT-FLAMES Tarantula Survey (VFTS). The distribution of $v_{e}\\sin i$ shows a two-component structure: a peak around 80 $\\rm{km s^{-1}}$ and a high-velocity tail extending up to $\\sim$600 $\\rm{km s^{-1}}$. Around 75% of the sample has 0 $\\leq\\, v_{e}\\sin i \\leq$ 200 $\\rm{km s^{-1}}$ with the other 25% distributed in the high-velocity tail. The presence of the low-velocity peak is consi...
Brott, Ines; Hunter, Ian; de Koter, Alex; Langer, Norbert; Dufton, Philip L; Cantiello, Matteo; Trundle, Carrie; Lennon, Danny J; de Mink, Selma E; Yoon, Sung-Chul; Anders, Peter
2011-01-01
Rotational mixing in massive stars is a widely applied concept, with far reaching consequences for stellar evolution. Nitrogen surface abundances for a large and homogeneous sample of massive B-type stars in the LMC were obtained by the VLT-FLAMES Survey of Massive Stars. This sample is the first covering a broad range of projected stellar rotational velocities, with a large enough sample of high quality data to allow for a statistically significant analysis. We use the sample to provide the first rigorous test of the theory of rotational mixing in massive stars. We calculated a grid of stellar evolution models, using the FLAMES sample to calibrate some of the uncertain mixing processes. We developed a new population-synthesis code, which uses this grid to simulate a large population of stars with masses, ages and rotational velocity distributions consistent with those from the FLAMES sample. The synthesized population is then filtered by the selection effects in the observed sample, to enable a direct compar...
Velocity anticipation in the optimal velocity model
DONG Li-yun; WENG Xu-dan; LI Qing-ding
2009-01-01
In this paper,the velocity anticipation in the optimal velocity model (OVM) is investigated.The driver adjusts the velocity of his vehicle by the desired headway,which depends on both instantaneous headway and relative velocity.The effect of relative velocity is measured by a sensitivity function.A specific form of the sensitivity function is supposed and the involved parameters are determined by the both numerical simulation and empirical data.It is shown that inclusion of velocity anticipation enhances the stability of traffic flow.Numerical simulations show a good agreement with empirical data.This model provides a better description of real traffic,including the acceleration process from standing states and the deceleration process approaching a stopped car.
Tachoastrometry: astrometry with radial velocities
Pasquini, L; Lombardi, M; Monaco, L; Leão, I C; Delabre, B
2014-01-01
Spectra of composite systems (e.g., spectroscopic binaries) contain spatial information that can be retrieved by measuring the radial velocities (i.e., Doppler shifts) of the components in four observations with the slit rotated by 90 degrees in the sky. By using basic concepts of slit spectroscopy we show that the geometry of composite systems can be reliably retrieved by measuring only radial velocity differences taken with different slit angles. The spatial resolution is determined by the precision with which differential radial velocities can be measured. We use the UVES spectrograph at the VLT to observe the known spectroscopic binary star HD 188088 (HIP 97944), which has a maximum expected separation of 23 milli-arcseconds. We measure an astrometric signal in radial velocity of 276 \\ms, which corresponds to a separation between the two components at the time of the observations of 18 $\\pm2$ milli-arcseconds. The stars were aligned east-west. We describe a simple optical device to simultaneously record p...
Allen, M. J.; Tatham, D.; Faulkner, D. R.; Mariani, E.; Boulton, C.
2017-08-01
The Alpine Fault, a transpressional plate boundary between the Australian and Pacific plates, is known to rupture quasiperiodically with large magnitude earthquakes (Mw 8). The hydraulic and elastic properties of fault zones are thought to vary over the seismic cycle, influencing the nature and style of earthquake rupture and associated processes. We present a suite of laboratory permeability and P (Vp) and S (Vs) wave velocity measurements performed on fault lithologies recovered during the first phase of the Deep Fault Drilling Project (DFDP-1), which sampled principal slip zone (PSZ) gouges, cataclasites, and fractured ultramylonites, with all recovered lithologies overprinted by abundant secondary mineralization, recording enhanced fluid-rock interaction. Core material was tested in three orthogonal directions, orientated relative to the down-core axis and, when present, foliation. Measurements were conducted with pore pressure (H2O) held at 5 MPa over an effective pressure (Peff) range of 5-105 MPa. Permeabilities and seismic velocities decrease with proximity to the PSZ with permeabilities ranging from 10-17 to 10-21 m2 and Vp and Vs ranging from 4400 to 5900 m/s in the ultramylonites/cataclasites and 3900 to 4200 m/s at the PSZ. In comparison with intact country rock protoliths, the highly variable cataclastic structures and secondary phyllosilicates and carbonates have resulted in an overall reduction in permeability and seismic wave velocity, as well as a reduction in anisotropy within the fault core. These results concur with other similar studies on other mature, tectonic faults in their interseismic period.
Magnetized galactic halos and velocity lags
Henriksen, Richard N
2016-01-01
We present an analytic model of a magnetized galactic halo surrounding a Mestel gravitating disc. The magnetic field is taken to be in energy equipartition with the pressure dominant rotating halo gas ({\\it not} with the cosmic rays), and the whole system is in a steady state. A more flexible `anisotropic equipartition' model is also explored. A definite pressure law is required to maintain the equilibrium, but the halo density is constant. The velocity/magnetic system is scale-free. The objective is to find the rotational velocity lag in such a halo. The magnetic field is not force-free so that angular momentum may be transported from the halo to the intergalactic medium. We find that the `X'-shaped structure observed for halo magnetic fields can be obtained together with a simple analytic formula for the rate of decline of the velocity with height $z$. The formula also predicts the change in lag with radius, $r$.
Measurements of translation, rotation and strain: new approaches to seismic processing and inversion
Bernauer, M.; Fichtner, A.; Igel, H.
2012-01-01
We propose a novel approach to seismic tomography based on the joint processing of translation, strain and rotation measurements. Our concept is based on the apparent S and P velocities, defined as the ratios of displacement velocity and rotation amplitude, and displacement velocity and divergence a
Do stars converging to the slow-rotator sequence possess inflated radii?
Lanzafame, Alessandro C; Distefano, Elisa
2016-01-01
Average stellar radii in open clusters can be estimated from rotation periods and projected rotational velocities under the assumption of random orientation of the spin axis. Such estimates are independent of distance, interstellar absorption, and models, but their validity can be limited by missing data (truncation) or data that only represent upper/lower limits (censoring). We present a new statistical analysis method to estimate average stellar radii in the presence of censoring and truncation. We use theoretical distribution functions of the projected stellar radius $R \\sin i$ to define a likelihood function in the presence of censoring and truncation. Average stellar radii in magnitude bins are then obtained by a maximum likelihood parametric estimation procedure. This method is capable of recovering the average stellar radius within a few percent with as few as $\\approx$ 10 measurements. Here it is applied for the first time to the dataset available for the Pleiades. We find an agreement better than $\\a...
Confirmation of bistable stellar differential rotation profiles
Käpylä, P J; Brandenburg, A
2014-01-01
(abridged) Context: Solar-like differential rotation is characterized by a rapidly rotating equator and slower poles. However, theoretical models and numerical simulations can also result in a slower equator and faster poles when the overall rotation is slow. Aims: We study the critical rotational influence under which differential rotation flips from solar-like (fast equator, slow poles) to an anti-solar one (slow equator, fast poles). We also estimate the non-diffusive ($\\Lambda$-effect) and diffusive (turbulent viscosity) contributions to the Reynolds stress. Methods: We perform three-dimensional numerical simulations of mildly turbulent convection in spherical wedge geometry. We regulate the convective velocities by varying the amount of heat transported by thermal conduction, turbulent diffusion, and resolved convection. Results: Increasing the efficiency of resolved convection leads to a reduction of the rotational influence on the flow and a sharp transition from solar-like to anti-solar differential r...
Are rotating planes of satellite galaxies ubiquitous?
Phillips, John I; Bullock, James S; Boylan-Kolchin, Michael
2015-01-01
We compare the dynamics of satellite galaxies in the Sloan Digital Sky Survey to simple models in order to test the hypothesis that a large fraction of satellites co-rotate in coherent planes. We confirm the previously-reported excess of co-rotating satellite pairs located near diametric opposition with respect to the host, but show that this signal is unlikely to be due to rotating discs (or planes) of satellites. In particular, no overabundance of co-rotating satellites pairs is observed within $\\sim 20^{\\circ}-50^{\\circ}$ of direct opposition, as would be expected for planar distributions inclined relative to the line-of-sight. Instead, the excess co-rotation for satellite pairs within $\\sim 10^{\\circ}$ of opposition is consistent with random noise associated with undersampling of an underlying isotropic velocity distribution. We conclude that at most $10\\%$ of the hosts in our sample harbor co-rotating satellite planes (as traced by the luminous satellite population).
A Stellar Rotation Census of B Stars: from ZAMS to TAMS
Huang, Wenjin; McSwain, M Virginia
2010-01-01
Two recent observing campaigns provide us with moderate dispersion spectra of more than 230 cluster and 370 field B stars. Combining them and the spectra of the B stars from our previous investigations ($\\sim$430 cluster and $\\sim$100 field B stars) yields a large, homogeneous sample for studying the rotational properties of B stars. We derive the projected rotational velocity $V\\sin i$, effective temperature, gravity, mass, and critical rotation speed $V_{\\rm crit}$ for each star. We find that the average $V\\sin i$ is significantly lower among field stars because they are systematically more evolved and spun down than their cluster counterparts. The rotational distribution functions of $V_{\\rm eq}/V_{\\rm crit}$ for the least evolved B stars show that lower mass B stars are born with a larger proportion of rapid rotators than higher mass B stars. However, the upper limit of $V_{\\rm eq}/V_{\\rm crit}$ that may separate normal B stars from emission line Be stars (where rotation promotes mass loss into a circumst...
Instabilities in Coaxial Rotating Jets
无
2000-01-01
The aim of this study is the characterization of the cylindrical mixing layer resulting layer resulting from the interaction of two coaxial swirling jets.The experimental part of this study was performed in a cylindrical water tunnel,permitting an independent rotation of two coaxial jets.The rotations are generated by means of 2×36 blades localized in two swirling chambers.As expected,the evolution of the main instabiltiy modes presents certain differences compared to the plane-mixing-layer case ,Experimental results obtained by tomography showed the existence of vortex rings and streamwise vortex paris in the near field region.This method also permitted the observation of the evolution and interaction of different modes.PIV velocity measurements realized in the meridian plans and the plans perpendicular to the jet axis show that rotation distrots the typical top-hat axial velocity profile.The transition of the the axial velocity profile from jet-like into wake-like is also observed.
Rotating Rayleigh-Taylor turbulence
Boffetta, G.; Mazzino, A.; Musacchio, S.
2016-09-01
The turbulent Rayleigh-Taylor system in a rotating reference frame is investigated by direct numerical simulations within the Oberbeck-Boussinesq approximation. On the basis of theoretical arguments, supported by our simulations, we show that the Rossby number decreases in time, and therefore the Coriolis force becomes more important as the system evolves and produces many effects on Rayleigh-Taylor turbulence. We find that rotation reduces the intensity of turbulent velocity fluctuations and therefore the growth rate of the temperature mixing layer. Moreover, in the presence of rotation the conversion of potential energy into turbulent kinetic energy is found to be less effective, and the efficiency of the heat transfer is reduced. Finally, during the evolution of the mixing layer we observe the development of a cyclone-anticyclone asymmetry.
On the non-synchronous rotation of binary systems?
Li, ZhiXiong; Huang, RunQian; Wang, ShuMin
2014-06-01
During the evolution of the binary system, many physical processes occur, which can influence the orbital angular velocity and the spin angular velocities of the two components, and influence the non-synchronous or synchronous rotation of the system. These processes include the transfer of masses and angular momentums between the component stars, the loss of mass and angular momentum via stellar winds, and the deformation of the structure of component stars. A study of these processes indicates that they are closely related to the combined effects of tide and rotation. This means, to study the synchronous or non-synchronous rotation of binary systems, one has to consider the contributions of different physical processes simultaneously, instead of the tidal effect alone. A way to know whether the rotation of a binary system is synchronous or non-synchronous is to calculate the orbital angular velocity and the spin angular velocities of the component stars. If all of these angular velocities are equal, the rotation of the system is synchronous. If not, the rotation of the system is non-synchronous. For this aim, a series of equations are developed to calculate the orbital and spin angular velocities. The evolutionary calculation of a binary system with masses of 10 M ⊙ + 6 M ⊙ shows that the transfer of masses and angular momentums between the two components, and the deformation of the components structure in the semidetached or in the contact phase can change the rotation of the system from synchronous into non-synchronous rotation.
Pareja, M J
2004-01-01
For general relativistic equilibrium stellar models (stationary axisymmetric asymptotically flat and convection-free) with differential rotation, it is shown that for a wide class of rotation laws the distribution of angular velocity of the fluid has a sign, say "positive", and then both the dragging rate and the angular momentum density are positive. In addition, the "mean value" (with respect to an intrinsic density) of the dragging rate is shown to be less than the mean value of the fluid angular velocity (in full general, without having to restrict the rotation law, nor the uniformity in sign of the fluid angular velocity); this inequality yields the positivity and an upper bound of the total rotational energy.
Observation of nondispersing classical-like molecular rotation
Korobenko, Aleksey; Milner, Valery
2014-01-01
Using the technique of an optical centrifuge, we produce rotational wave packets which evolve in time along either classical-like or non-classical trajectories. After releasing O2 and D2 molecules from the centrifuge, we track their field-free rotation by monitoring the molecular angular distribution with velocity map imaging. Due to the dispersion of the created rotational wave packets in oxygen, we observe a gradual transition between "dumbbell"-shaped and "cross"-shaped distributions, both rotating with a classical rotation frequency. In deuterium, a much narrower rotational wave packet is produced and shown to evolve in a truly classical non-dispersing fashion.
RADIAL VELOCITIES FROM VLT-KMOS SPECTRA OF GIANT STARS IN THE GLOBULAR CLUSTER NGC 6388
Lapenna, E.; Mucciarelli, A.; Lanzoni, B.; Ferraro, F. R.; Dalessandro, E. [Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy); Origlia, L. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani, 1, I-40127 Bologna (Italy); Valenti, E. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München (Germany); Cirasuolo, M. [Institute for Astronomy, University of Edinburgh and STFC, UK Astronomy Technology Center Royal Observatory, Blackford Hill, EH9 3HJ, Edinburgh (United Kingdom)
2015-01-01
We present new radial velocity measurements for 82 stars, members of the Galactic globular cluster (GC) NGC 6388, obtained from ESO-VLT K-band Multi Object Spectrograph (KMOS) spectra acquired during the instrument Science Verification. The accuracy of the wavelength calibration is discussed and a number of tests of the KMOS response are presented. The cluster systemic velocity obtained (81.3 ± 1.5 km s{sup –1}) is in very good agreement with previous determinations. While a hint of ordered rotation is found between 9'' and 20'' from the cluster center, where the distribution of radial velocities is clearly bimodal, more data are needed before drawing any firm conclusions. The acquired sample of radial velocities has also been used to determine the cluster velocity dispersion (VD) profile between ∼9'' and 70'', supplementing previous measurements at r < 2'' and r > 60'' obtained with ESO-SINFONI and ESO-FLAMES spectroscopy, respectively. The new portion of the VD profile nicely matches the previous ones, better defining the knee of the distribution. The present work clearly shows the effectiveness of a deployable integral field unit in measuring the radial velocities of individual stars for determining the VD profile of Galactic GCs. It represents the pilot project for an ongoing large program with KMOS and FLAMES at the ESO-VLT, aimed at determining the next generation of VD and rotation profiles for a representative sample of GCs.
Phillips, J.S.
1991-12-01
The Yucca Mountain Site Characterization Project (YMP), managed by the Office of Geologic Disposal of the Office of Civilian Radioactive Waste Management of the US Department of Energy, is examining the feasibility of siting a repository for commercial, high-level nuclear wastes at Yucca Mountain on and adjacent to the Nevada Test Site (NTS). This work, intended to extend our understanding of the ground motion at Yucca Mountain resulting from testing of nuclear weapons on the NTS, was funded by the Yucca Mountain project and the Military Applications Weapons Test Program. This report summarizes one aspect of the weapons test seismic investigations conducted in FY88. Pseudo relative velocity response spectra (PSRV) have been calculated for a large body of surface ground motions generated by underground nuclear explosions. These spectra have been analyzed and fit using multiple linear regression techniques to develop a credible prediction technique for surface PSRVs. In addition, a technique for estimating downhole PSRVs at specific stations is included. A data summary, data analysis, prediction development, prediction evaluation, software summary and FORTRAN listing of the prediction technique are included in this report.
Hanasoge, Shravan M.; Duvall, Thomas L., Jr.; Sreenivasan, Katepalli R.
2012-01-01
Convection in the solar interior is thought to comprise structures at a continuum of scales, from large to small. This conclusion emerges from phenomenological studies and numerical simulations though neither covers the proper range of dynamical parameters of solar convection. In the present work, imaging techniques of time-distance helioseismology applied to observational data reveal no long-range order in the convective motion. We conservatively bound the associated velocity magnitudes, as a function of depth and the spherical-harmonic degree l to be 20-100 times weaker than prevailing estimates within the wavenumber band l ux of a solar luminosity outwards? The Sun is seemingly a much faster rotator than previously thought, with advection dominated by Coriolis forces at scales l < 60.
Diamagnetic pumping in a rotating convection zone
Kitchatinov, L. L.; Nepomnyashchikh, A. A.
2016-10-01
Solar dynamo models require some mechanism for magnetic field concentration near the base of the convection zone in order to generate super-kilogauss toroidal fields with sufficiently large (∼ 1024 Mx) magnetic flux. We consider the downward diamagnetic pumping near the base of the convection zone as a possible concentration mechanism and derive the pumping velocities with allowance for the effect of rotation. Transport velocities for poloidal and toroidal fields differ in rotating fluid. The toroidal field is transported downward along the radius only but the pumping velocity for the poloidal field has an equatorward meridional component also. Previous results for cases of slow and rapid rotation are reproduced and the diamagnetic pumping expressions adapted for use in dynamo models are presented.
Diamagnetic pumping in a rotating convection zone
Kitchatinov, L
2016-01-01
Solar dynamo models require some mechanism for magnetic field concentration near the base of the convection zone in order to generate super-kilogauss toroidal fields with sufficiently large (~10^{24} Mx) magnetic flux. We consider the downward diamagnetic pumping near the base of the convection zone as a possible concentration mechanism and derive the pumping velocities with allowance for the effect of rotation. Transport velocities for poloidal and toroidal fields differ in rotating fluid. The toroidal field is transported downward along the radius only but the pumping velocity for the poloidal field has an equatorward meridional component also. Previous results for cases of slow and rapid rotation are reproduced and the diamagnetic pumping expressions adapted for use in dynamo models are presented.
Velocity profiles in strongly turbulent Taylor-Couette flow
Grossmann, S.; Lohse, D.; Sun, C.
2014-01-01
We derive the velocity profiles in strongly turbulent Taylor-Couette flow for the general case of independently rotating cylinders. The theory is based on the Navier-Stokes equations in the appropriate (cylinder) geometry. In particular, we derive the axial and the angular velocity profiles as funct
THE FLOW IN ROTATING CURVED CIRCULAR PIPE
无
2000-01-01
The combined effects of the system rotation (Coriolis force) and curvature (centrifugal force) on the flow in rotating curved circular pipe with small curvature are examined by perturbation method. A second-order perturbation solution is presented. The secondary flow structure and the primary axial velocity distributions are studied in detail. The loops of the secondary flow are more complex than those in a curved pipe without rotation or a rotating straight pipe. Its numbers depend on the body force ratio F which represents the ratio of the Coriolis to the centrifugal force. The maximum of the axial velocity is pushed to either outer bend or inner bend, which is also determined by F. The results are confirmed by the results of other authors who studied the same problem by different methods.
Dynamics of Rotating, Magnetized Neutron Stars
Liebling, Steven L.
2010-01-01
Using a fully general relativistic implementation of ideal magnetohydrodynamics with no assumed symmetries in three spatial dimensions, the dynamics of magnetized, rigidly rotating neutron stars are studied. Beginning with fully consistent initial data constructed with Magstar, part of the Lorene project, we study the dynamics and stability of rotating, magnetized polytropic stars as models of neutron stars. Evolutions suggest that some of these rotating, magnetized stars may be minimally uns...
Systematic Search for Rotation at the Base of Outflows from T Tauri Stars
Bacciotti, Francesca
2002-07-01
We wish to search for rotation signatures in the initial portion {first 100 AU} of a sample of outflows emanating from T Tauri stars {TTSs}. This project originates from our detection of systematic transverse radial velocity shifts in STIS spectra of the DG Tau jet {Bacciotti et al., 2002}. The shifts, observed in a region where the flow is already collimated, but has not yet manifestly interacted with its environment, are consistent with the predictions of magneto- centrifugal launching models, and may constitute the first observed indication for rotation in the initial portion of a jet flow. Rotation is a fundamental ingredient in star formation theories, thus we propose to confirm the above result by carrying out a systematic survey in similar flows. We plan to take for each jet a STIS spectrum in the 6300 - 6800 Angstrom range, with the slit perpendicular to the flow direction and at a distance of about 0.''3 from the source {i.e., in our targets, 40 - 70 AU along the jet depending on inclination angle}. Since the flows are resolved transversely with HST, the proposed slit orientation allows for the direct detection of systematic velocity shifts. Where found, we will check for consistency between the sense of rotation observed and that of the underlying disk through CO interferometric measurements. As a by-product, estimates of the excitation conditions across the flow {including ionization fraction} and of the mass outflow rates will be derived.
Stellar rotation effects in polarimetric microlensing
Sajadian, Sedighe
2016-01-01
It is well known that the polarization signal in microlensing events of hot stars is larger than that of main-sequence stars. Most hot stars rapidly rotate around their stellar axes. The stellar rotation makes ellipticity and gravity-darkening effects which break the spherical symmetry of the source shape and the circular symmetry of the source surface brightness respectively. Hence, it causes a net polarization signal for the source star. This polarization signal should be considered in polarimetry microlensing of fast rotating stars. For moderate rotating stars, lensing can magnify or even characterize small polarization signals due to the stellar rotation through polarimetry observations. The gravity-darkening effect due to a rotating source star makes asymmetric perturbations in polarimetry and photometry microlensing curves whose maximum happens when the lens trajectory crosses the projected position of the rotation pole on the sky plane. The stellar ellipticity makes a time shift (i) in the position of ...
Kissin, Yevgeni
2015-01-01
The internal rotation of post-main sequence stars is investigated, in response to the convective pumping of angular momentum toward the stellar core, combined with a tight magnetic coupling between core and envelope. The spin evolution is calculated using model stars of initial mass 1, 1.5 and $5\\,M_\\odot$, taking into account mass loss on the giant branches and the partitioning of angular momentum between the outer and inner envelope. We also include the deposition of orbital angular momentum from a sub-stellar companion, as influenced by tidal drag as well as the excitation of orbital eccentricity by a fluctuating gravitational quadrupole moment. A range of angular velocity profiles $\\Omega(r)$ is considered in the deep convective envelope, ranging from solid rotation to constant specific angular momentum. We focus on the backreaction of the Coriolis force on the inward pumping of angular momentum, and the threshold for dynamo action in the inner envelope. Quantitative agreement with measurements of core ro...
Trirotron: triode rotating beam radio frequency amplifier
Lebacqz, Jean V.
1980-01-01
High efficiency amplification of radio frequencies to very high power levels including: establishing a cylindrical cloud of electrons; establishing an electrical field surrounding and coaxial with the electron cloud to bias the electrons to remain in the cloud; establishing a rotating electrical field that surrounds and is coaxial with the steady field, the circular path of the rotating field being one wavelength long, whereby the peak of one phase of the rotating field is used to accelerate electrons in a beam through the bias field in synchronism with the peak of the rotating field so that there is a beam of electrons continuously extracted from the cloud and rotating with the peak; establishing a steady electrical field that surrounds and is coaxial with the rotating field for high-energy radial acceleration of the rotating beam of electrons; and resonating the rotating beam of electrons within a space surrounding the second field, the space being selected to have a phase velocity equal to that of the rotating field to thereby produce a high-power output at the frequency of the rotating field.
Hernandez, X; Cervantes-Sodi, B; Ibarra-Medel, H J; Lopez-Cruz, O
2015-01-01
For any MONDian extended theory of gravity where the rotation curves of spiral galaxies are explained through a change in physics rather than the hypothesis of dark matter, a generic dynamical behaviour is expected for pressure supported systems: an outer flattening of the velocity dispersion profile occurring at a characteristic radius, where both the amplitude of this flat velocity dispersion and the radius at which it appears are predicted to show distinct scalings with the total mass of the system. By carefully analysing dynamics of globular clusters, elliptical galaxies and galaxy clusters, we are able to significantly extend the astronomical scales over which MONDian gravity has been tested, from those of spiral galaxies, to the much larger range covered by pressure supported systems. We show that a universal projected velocity dispersion profile accurately describes various classes of pressure supported systems, and further, that the expectations of extended gravity are met, across twelve orders of mag...
VELOCITY BUNCHING OF HIGH-BRIGHTNESS ELECTRON BEAMS
Anderson, S G; Musumeci, P; Rosenzweig, J B; Brown, W J; England, R J; Ferrario, M; Jacob, J S; Thompson, M C; Travish, G; Tremaine, A M; Yoder, R
2004-10-15
Velocity bunching has been recently proposed as a tool for compressing electron beam pulses in modern high brightness photoinjector sources. This tool is familiar from earlier schemes implemented for bunching dc electron sources, but presents peculiar challenges when applied to high current, low emittance beams from photoinjectors. The main difficulty foreseen is control of emittance oscillations in the beam in this scheme, which can be naturally considered as an extension of the emittance compensation process at moderate energies. This paper presents two scenarios in which velocity bunching, combined with emittance control, is to play a role in nascent projects. The first is termed ballistic bunching, where the changing of relative particle velocities and positions occur in distinct regions, a short high gradient linac, and a drift length. This scenario is discussed in the context of the proposed ORION photoinjector. Simulations are used to explore the relationship between the degree of bunching, and the emittance compensation process. Experimental measurements performed at the UCLA Neptune Laboratory of the surprisingly robust bunching process, as well as accompanying deleterious transverse effects, are presented. An unanticipated mechanism for emittance growth in bends for highly momentum chirped beam was identified and studied in these experiments. The second scenario may be designated as phase space rotation, and corresponds closely to the recent proposal of Ferrario and Serafini. Its implementation for the compression of the electron beam pulse length in the PLEIADES inverse Compton scattering (ICS) experiment at LLNL is discussed. It is shown in simulations that optimum compression may be obtained by manipulation of the phases in low gradient traveling wave accelerator sections. Measurements of the bunching and emittance control achieved in such an implementation at PLEIADES, as well as aspects of the use of velocity-bunched beam directly in ICS experiments
Velocity bunching of high-brightness electron beams
S. G. Anderson
2005-01-01
Full Text Available Velocity bunching has been recently proposed as a tool for compressing electron beam pulses in modern high brightness photoinjector sources. This tool is familiar from earlier schemes implemented for bunching dc electron sources, but presents peculiar challenges when applied to high current, low emittance beams from photoinjectors. The main difficulty foreseen is control of emittance oscillations in the beam in this scheme, which can be naturally considered as an extension of the emittance compensation process at moderate energies. This paper presents two scenarios in which velocity bunching, combined with emittance control, is to play a role in nascent projects. The first is termed ballistic bunching, where the changing of relative particle velocities and positions occur in distinct regions, a short high gradient linac, and a drift length. This scenario is discussed in the context of the proposed ORION photoinjector. Simulations are used to explore the relationship between the degree of bunching, and the emittance compensation process. Experimental measurements performed at the UCLA Neptune Laboratory of the surprisingly robust bunching process, as well as accompanying deleterious transverse effects, are presented. An unanticipated mechanism for emittance growth in bends for highly momentum chirped beam was identified and studied in these experiments. The second scenario may be designated as phase space rotation, and corresponds closely to the recent proposal of Ferrario and Serafini. Its implementation for the compression of the electron beam pulse length in the PLEIADES inverse Compton scattering (ICS experiment at LLNL is discussed. It is shown in simulations that optimum compression may be obtained by manipulation of the phases in low gradient traveling wave accelerator sections. Measurements of the bunching and emittance control achieved in such an implementation at PLEIADES, as well as aspects of the use of velocity-bunched beam directly
Broadband Rotational Spectroscopy
Pate, Brooks
2014-06-01
The past decade has seen several major technology advances in electronics operating at microwave frequencies making it possible to develop a new generation of spectrometers for molecular rotational spectroscopy. High-speed digital electronics, both arbitrary waveform generators and digitizers, continue on a Moore's Law-like development cycle that started around 1993 with device bandwidth doubling about every 36 months. These enabling technologies were the key to designing chirped-pulse Fourier transform microwave (CP-FTMW) spectrometers which offer significant sensitivity enhancements for broadband spectrum acquisition in molecular rotational spectroscopy. A special feature of the chirped-pulse spectrometer design is that it is easily implemented at low frequency (below 8 GHz) where Balle-Flygare type spectrometers with Fabry-Perot cavity designs become technologically challenging due to the mirror size requirements. The capabilities of CP-FTMW spectrometers for studies of molecular structure will be illustrated by the collaborative research effort we have been a part of to determine the structures of water clusters - a project which has identified clusters up to the pentadecamer. A second technology trend that impacts molecular rotational spectroscopy is the development of high power, solid state sources in the mm-wave/THz regions. Results from the field of mm-wave chirped-pulse Fourier transform spectroscopy will be described with an emphasis on new problems in chemical dynamics and analytical chemistry that these methods can tackle. The third (and potentially most important) technological trend is the reduction of microwave components to chip level using monolithic microwave integrated circuits (MMIC) - a technology driven by an enormous mass market in communications. Some recent advances in rotational spectrometer designs that incorporate low-cost components will be highlighted. The challenge to the high-resolution spectroscopy community - as posed by Frank De
Rotge, J. R.; Simmons, B. J.; Kroncke, G. T.; Stech, D. J.
1986-05-01
Research efforts were concentrated on passive ring laser rotation sensor technology. Initial efforts were performed on supportive projects, e.g., laser stabilization, followed by a 0.62 sq m passive resonant ring laser gyro (PRRLG), leading to the development of a 60 sq m system mounted on the pneumatically supported isolation test platform (Iso-Pad) at FJSRL. Numerous sub-system tasks and a feasibility 0.62 sq m PRRLG were completed, supporting projections of very high resolution performance by a large 60 sq m PRRLG. The expected performance of the large PRRLG, on the order of 10 to the minus 10th power ERU (earth rate units), would provide an accurate error model applicable to Air Force operational ring laser gyros, a new source of geophysical data, e.g., earth wobble and variations in earth rotation, a proven design concept applicable to Air Force sensor needs as reference to MX instruments tests, and relativity experiments. This report documents the many accomplishments leading to, and the status of the large PRRLG at the date of the PRRLG stop order, November 1985.
Transverse Spectral Velocity Estimation
Jensen, Jørgen Arendt
2014-01-01
A transverse oscillation (TO)-based method for calculating the velocity spectrum for fully transverse flow is described. Current methods yield the mean velocity at one position, whereas the new method reveals the transverse velocity spectrum as a function of time at one spatial location. A convex...
Rotating blade vibration analysis using shells
Leissa, A. W.; Lee, J. K.; Wang, A. J.
1981-01-01
Shallow shell theory and the Ritz method are employed to determine the frequencies and mode shapes of turbomachinery blades having both camber and twist, rotating with non-zero angles of attack. Frequencies obtained for different degrees of shallowness and thickness are compared with results available in the literature, obtained from finite element analyses of nonrotating blades. Frequencies are also determined for a rotating blade, showing the effects of changing the (1) angular velocity of rotation, (2) disk radius and (3) angle of attack, as well as the significance of the most important body force terms.
Rotating Black Holes and Coriolis Effect
Wu, Xiaoning; Yuan, Pei-Hung; Cho, Chia-Jui
2015-01-01
In this work, we consider the fluid/gravity correspondence for general rotating black holes. By using the Petrov-like boundary condition in near horizon limit, we study the correspondence between gravitational perturbation and fluid equation. We find that the dual fluid equation for rotating black holes contains a Coriolis force term, which is closely related to the angular velocity of the black hole horizon. This can be seen as a dual effect for the frame-dragging effect of rotating black hole under the holographic picture.
Rotating black holes and Coriolis effect
Chou, Chia-Jui; Wu, Xiaoning; Yang, Yi; Yuan, Pei-Hung
2016-10-01
In this work, we consider the fluid/gravity correspondence for general rotating black holes. By using the suitable boundary condition in near horizon limit, we study the correspondence between gravitational perturbation and fluid equation. We find that the dual fluid equation for rotating black holes contains a Coriolis force term, which is closely related to the angular velocity of the black hole horizon. This can be seen as a dual effect for the frame-dragging effect of rotating black hole under the holographic picture.
Rotating black holes and Coriolis effect
Chia-Jui Chou; Xiaoning Wu; Yi Yang; Pei-Hung Yuan
2016-01-01
In this work, we consider the fluid/gravity correspondence for general rotating black holes. By using the Petrov-like boundary condition in near horizon limit, we study the correspondence between gravitational perturbation and fluid equation. We find that the dual fluid equation for rotating black holes contains a Coriolis force term, which is closely related to the angular velocity of the black hole horizon. This can be seen as a dual effect for the frame-dragging effect of rotating black ho...
Rotating black holes and Coriolis effect
Chia-Jui Chou
2016-10-01
Full Text Available In this work, we consider the fluid/gravity correspondence for general rotating black holes. By using the suitable boundary condition in near horizon limit, we study the correspondence between gravitational perturbation and fluid equation. We find that the dual fluid equation for rotating black holes contains a Coriolis force term, which is closely related to the angular velocity of the black hole horizon. This can be seen as a dual effect for the frame-dragging effect of rotating black hole under the holographic picture.
A revised rotation curve of the Milky Way with maser astrometry
Xiao-Sheng Xin; Xing-Wu Zheng
2013-01-01
We reconstruct the rotation curve of the Milky Way using the new trigonometric parallax and proper motion data for masers in 43 high-mass star-forming regions obtained by VLBI,as well as the existing data from the literature,based on a new set of galactic constants (R0,(O)0) =(8.4 kpc,254 km s-1) measured by Reid et al.The revised rotation curve of the Milky Way is almost flat or slightly rising in the region from about 6 to 15 kpc.The rotation velocities within 5 kpc of the Galactic center,as determined by VLBI,differ from those obtained by measurement of the HI-and CO-line tangent velocities.We fitted the revised rotation curve arising from three mass components:the bulge,disk and dark matter halo.The total mass of the Milky Way is found to be 2.3× 1011 M⊙ (20 kpc).This is about 10％ larger than that from Sofue et al,and is comparable with the mass of M31,3.4× 1011 M⊙ (35 kpc),given by Carignan et al.The limited accurate observational data,especially the VLBI data,do not permit a fully satisfactory fit to the rotation curve.The extensive parallax and proper motion data that will be produced by the Bar and Spiral Structure Legacy Survey project in the next few years should lead to considerable progress in understanding the rotation curve and dark matter halo of the Milky Way.
Counter-Rotating Tandem Motor Drilling System
Kent Perry
2009-04-30
Gas Technology Institute (GTI), in partnership with Dennis Tool Company (DTC), has worked to develop an advanced drill bit system to be used with microhole drilling assemblies. One of the main objectives of this project was to utilize new and existing coiled tubing and slimhole drilling technologies to develop Microhole Technology (MHT) so as to make significant reductions in the cost of E&P down to 5000 feet in wellbores as small as 3.5 inches in diameter. This new technology was developed to work toward the DOE's goal of enabling domestic shallow oil and gas wells to be drilled inexpensively compared to wells drilled utilizing conventional drilling practices. Overall drilling costs can be lowered by drilling a well as quickly as possible. For this reason, a high drilling rate of penetration is always desired. In general, high drilling rates of penetration (ROP) can be achieved by increasing the weight on bit and increasing the rotary speed of the bit. As the weight on bit is increased, the cutting inserts penetrate deeper into the rock, resulting in a deeper depth of cut. As the depth of cut increases, the amount of torque required to turn the bit also increases. The Counter-Rotating Tandem Motor Drilling System (CRTMDS) was planned to achieve high rate of penetration (ROP) resulting in the reduction of the drilling cost. The system includes two counter-rotating cutter systems to reduce or eliminate the reactive torque the drillpipe or coiled tubing must resist. This would allow the application of maximum weight-on-bit and rotational velocities that a coiled tubing drilling unit is capable of delivering. Several variations of the CRTDMS were designed, manufactured and tested. The original tests failed leading to design modifications. Two versions of the modified system were tested and showed that the concept is both positive and practical; however, the tests showed that for the system to be robust and durable, borehole diameter should be substantially larger
Multidimensional Simulations of Rotating Pair Instability Supernovae
Chatzopoulos, E; Couch, S M
2013-01-01
We study the effects of rotation on the dynamics, energetics and Ni-56 production of Pair Instability Supernova explosions by performing rotating two-dimensional ("2.5-D") hydrodynamics simulations. We calculate the evolution of eight low metallicity (Z = 10^-3, 10^-4 Zsun) massive (135-245 Msun) PISN progenitors with initial surface rotational velocities 50% that of the critical Keplerian value using the stellar evolution code MESA. We allow for both the inclusion and the omission of the effects of magnetic fields in the angular momentum transport and in chemical mixing, resulting in slowly-rotating and rapidly-rotating final carbon-oxygen cores, respectively. Increased rotation for carbon-oxygen cores of the same mass and chemical stratification leads to less energetic PISN explosions that produce smaller amounts of Ni-56 due to the effect of the angular momentum barrier that develops and slows the dynamical collapse. We find a non-monotonic dependence of Ni-56 production on rotational velocity in situation...
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Rotating embedded black holes: Entropy and Hawking's radiation
2004-01-01
In this paper we derive a class of rotating embedded black holes. Then we study Hawking's radiation effects on these embedded black holes. The surface gravity, entropy and angular velocity are given for each of these black holes.
Electrovacuum Static Counter-Rotating Relativistic Dust Disks
González, G A
2002-01-01
A detailed study of the Counter-Rotating Model (CRM) for generic electrostatic (magnetostatic) axially symmetric thin disks without radial pressure is presented. We find a general constraint over the counter-rotating tangential velocities needed to cast the surface energy-momentum tensor of the disk as the superposition of two counter-rotating charged dust fluids. We then show that this constraint is satisfied if we take the two counter-rotating streams as circulating along electrogeodesics with equal and opposite tangential velocities. We also find explicit expressions for the energy densities, electrostatic (magnetostatic) charge densities and velocities of the counter-rotating fluids. Three specific examples are considered where we obtain some CRM well behaved based in simple solutions to the Einstein-Maxwell equations. The considered solutions are Reissner-Nordstrom in the electrostatic case, its magnetostatic counterpart and two solutions obtained from Taub-NUT and Kerr solutions.
张晓娟; 智光
2011-01-01
Objective To assess the regional rotation in canine with myocardial ischemia and acute myocardial infarction by velocity vector imaging( VVI ).Methods Myocardial ischemia and infarction model were successfully made by partly and fully ligating the left anterior descending coronary artery ( LAD ) in twelve mongrel dogs. The ventricle rotation and strain were measured by VVI. Results The results revealed: The LAD part ligation: rotation decreased in ventricular septal before LAD ligation status in LAD part ligation status( P ＜0. 05 ). The strain and strain rate has no significant difference. The LAD ful ligation: the rotation rate, rotation, circumferential strain and strain rate of the anterior septal, anterior wall and ventricular septal were significantly decreased in myocardial infarction status compared with those in the normal status, and were also significantly decreased compared with those in the myocardial ischemia status( P ＜0. 05 ). The strain and strain rate in the anterior septal,anterior wall and ventricular septal were significantly decreased in myocardial infarction status compared with those in the normal status( P ＜0. 05 ), but not significantly decreased compared with those in partly ligation status. Conclusion VVI can non-invasively and sensitively assess the left ventricular rotation and the results indicated the ventricular rotation is more sensitive than the strain and strain rate in evaluation of the ventricular systolic function.%目的 应用速度向量成像(VVI)技术评价心肌缺血及心肌梗死状态下犬心肌旋转运动特征.方法 选用杂种犬12只,在超声实时引导下结扎前降支定量制备前降支轻度狭窄(狭窄率:50%～75%)与完全闭塞模型,应用VVI技术分析前降支结扎前、轻度狭窄与完全闭塞状态下左心室旋转特征的改变.结果 12只杂种犬成功制备前降支轻度狭窄与完全闭塞模型,应用VVI技术对缺血与梗死状态下心肌旋
The VLT-FLAMES Tarantula Survey XVIII. Classifications and radial velocities of the B-type stars
Evans, C J; Dufton, P L; Howarth, I D; Walborn, N R; Markova, N; Clark, J S; de Mink, S E; de Koter, A; Dunstall, P R; Hénault-Brunet, V; Apellániz, J Maíz; McEvoy, C M; Sana, H; Simón-Díaz, S; Taylor, W D; Vink, J S
2015-01-01
We present spectral classifications for 438 B-type stars observed as part of the VLT-FLAMES Tarantula Survey (VFTS) in the 30 Doradus region of the Large Magellanic Cloud. Radial velocities are provided for 307 apparently single stars, and for 99 targets with radial-velocity variations which are consistent with them being spectroscopic binaries. We investigate the spatial distribution of the radial velocities across the 30 Dor region, and use the results to identify candidate runaway stars. Excluding potential runaways and members of two older clusters in the survey region (SL 639 and Hodge 301), we determine a systemic velocity for 30 Dor of 271.6 +/- 12.2 km/s from 273 presumed single stars. Employing a 3-sigma criterion we identify nine candidate runaway stars (2.9% of the single stars with radial-velocity estimates). The projected rotational velocities of the candidate runaways appear to be significantly different to those of the full B-type sample, with a strong preference for either large (>345 km/s) or...
Rotation and mass in the Milky Way and spiral galaxies
Sofue, Yoshiaki
2017-02-01
Rotation curves are the basic tool for deriving the distribution of mass in spiral galaxies. In this review, we describe various methods to measure rotation curves in the Milky Way and spiral galaxies. We then describe two major methods to calculate the mass distribution using the rotation curve. By the direct method, the mass is calculated from rotation velocities without employing mass models. By the decomposition method, the rotation curve is deconvolved into multiple mass components by model fitting assuming a black hole, bulge, exponential disk, and dark halo. The decomposition is useful for statistical correlation analyses among the dynamical parameters of the mass components. We also review recent observations and derived results.
A neural circuit for angular velocity computation
Samuel B Snider
2010-12-01
Full Text Available In one of the most remarkable feats of motor control in the animal world, some Diptera, such as the housefly, can accurately execute corrective flight maneuvers in tens of milliseconds. These reflexive movements are achieved by the halteres, gyroscopic force sensors, in conjunction with rapidly-tunable wing-steering muscles. Specifically, the mechanosensory campaniform sensilla located at the base of the halteres transduce and transform rotation-induced gyroscopic forces into information about the angular velocity of the fly's body. But how exactly does the fly's neural architecture generate the angular velocity from the lateral strain forces on the left and right halteres? To explore potential algorithms, we built a neuro-mechanical model of the rotation detection circuit. We propose a neurobiologically plausible method by which the fly could accurately separate and measure the three-dimensional components of an imposed angular velocity. Our model assumes a single sign-inverting synapse and formally resembles some models of directional selectivity by the retina. Using multidimensional error analysis, we demonstrate the robustness of our model under a variety of input conditions. Our analysis reveals the maximum information available to the fly given its physical architecture and the mathematics governing the rotation-induced forces at the haltere's end knob.
Velocity selective optical pumping
Aminoff, C. G.; Pinard, M.
1982-01-01
We consider optical pumping with a quasi monochromatic tunable light beam, in the low intensity limit where a rate equation regime is obtained The velocity selective optical pumping (V.S.O.P.) introduces a correlation between atomic velocity and internal variables in the ground (or metastable) state. The aim of this article is to evaluate these atomic observables (orientation, alignment, population) as a function of velocity, using a phenomenological description of the relaxation effect of co...
Vortex statistics in turbulent rotating convection
Kunnen, R.P.J.; Clercx, H.J.H.; Geurts, B.J.
2010-01-01
The vortices emerging in rotating turbulent Rayleigh-Bénard convection in water at Rayleigh number Ra=6.0×108 are investigated using stereoscopic particle image velocimetry and by direct numerical simulation. The so-called Q criterion is used to detect the vortices from velocity fields. This criter
Hydrogen Pellet-Rotating Plasma Interaction
Jørgensen, L. W.; Sillesen, Alfred Hegaard; Øster, Flemming
1977-01-01
Spectroscopic measurements on the interaction between solid hydrogen pellets and rotating plasmas are reported. It was found that the light emitted is specific to the pellet material, and that the velocity of the ablated H-atoms is of the order of l0^4 m/s. The investigation was carried out...
Effects of rotation in AGB stars
Luciano, Piersanti; Oscar, Straniero
2013-01-01
In this paper we analyze the effects induced by rotation on low mass Asymptotic Giant Branch stars. We compute two sets of models, M=2.0 Msun at [Fe/H]=0 and M=1.5 Msun at [Fe/H]=-1.7, respectively, by adopting Main Sequence rotation velocities in the range 0 - 120 km/s. At high metallicity, we find that the Goldreich-Schubert-Fricke instability, active at the interface between the convective envelope and the rapid rotating core, contaminates the 13C-pocket (the major neutron source) with 14N (the major neutron poison), thus reducing the neutron flux available for the synthesis of heavy elements. As a consequence, the yields of heavy-s elements (Ba, La, Nd, Sm) and, to a less extent, those of light-s elements (Sr, Y, Zr) decrease with increasing rotation velocities up to 60 km/s. However, for larger initial rotation velocities, the production of light-s and, to a less extent, that of heavy-s begins again to increase, due to mixing induced by meridional circulations. At low metallicity, the effects of meridion...
Velocity profiles in strongly turbulent Taylor-Couette flow
Grossmann, Siegfried; Sun, Chao
2013-01-01
We derive the velocity profiles in strongly turbulent Taylor-Couette flow for the general case of independently rotating cylinders. The theory is based on the Navier-Stokes equations in the appropriate (cylinder) geometry. In particular, we derive the axial and the angular velocity profiles as functions of distance from the cylinder walls and find that both follow a logarithmic profile, with downwards-bending curvature corrections, which are more pronounced for the angular velocity profile as compared to the axial velocity profile, and which strongly increase with decreasing ratio $\\eta$ between inner and outer cylinder radius. In contrast, the azimuthal velocity does not follow a log-law. We then compare the angular and azimuthal velocity profiles with the recently measured profiles in the ultimate state of (very) large Taylor numbers. Though the {\\em qualitative} trends are the same -- down-bending for large wall distances and (properly shifted and non-dimensionalized) angular velocity profile $\\omega^+(r)$...
Edge localized mode rotation and the nonlinear dynamics of filaments
Morales, J. A.; Bécoulet, M.; Garbet, X.; Dif-Pradalier, G.; Huijsmans, G. T. A.; Fil, A.; Nardon, E.; Passeron, C.; Latu, G. [CEA, IRFM, 13108 St. Paul-Lez-Durance (France); Orain, F.; Hoelzl, M. [Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching (Germany); Pamela, S. [CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Cahyna, P. [Institute of Plasma Physics ASCR, Za Slovankou 1782/3, 182 00 Prague 8 (Czech Republic)
2016-04-15
Edge Localized Modes (ELMs) rotating precursors were reported few milliseconds before an ELM crash in several tokamak experiments. Also, the reversal of the filaments rotation at the ELM crash is commonly observed. In this article, we present a mathematical model that reproduces the rotation of the ELM precursors as well as the reversal of the filaments rotation at the ELM crash. Linear ballooning theory is used to establish a formula estimating the rotation velocity of ELM precursors. The linear study together with nonlinear magnetohydrodynamic simulations give an explanation to the rotations observed experimentally. Unstable ballooning modes, localized at the pedestal, grow and rotate in the electron diamagnetic direction in the laboratory reference frame. Approaching the ELM crash, this rotation decreases corresponding to the moment when the magnetic reconnection occurs. During the highly nonlinear ELM crash, the ELM filaments are cut from the main plasma due to the strong sheared mean flow that is nonlinearly generated via the Maxwell stress tensor.
Edge localized mode rotation and the nonlinear dynamics of filaments
Morales, J. A.; Bécoulet, M.; Garbet, X.; Orain, F.; Dif-Pradalier, G.; Hoelzl, M.; Pamela, S.; Huijsmans, G. T. A.; Cahyna, P.; Fil, A.; Nardon, E.; Passeron, C.; Latu, G.
2016-04-01
Edge Localized Modes (ELMs) rotating precursors were reported few milliseconds before an ELM crash in several tokamak experiments. Also, the reversal of the filaments rotation at the ELM crash is commonly observed. In this article, we present a mathematical model that reproduces the rotation of the ELM precursors as well as the reversal of the filaments rotation at the ELM crash. Linear ballooning theory is used to establish a formula estimating the rotation velocity of ELM precursors. The linear study together with nonlinear magnetohydrodynamic simulations give an explanation to the rotations observed experimentally. Unstable ballooning modes, localized at the pedestal, grow and rotate in the electron diamagnetic direction in the laboratory reference frame. Approaching the ELM crash, this rotation decreases corresponding to the moment when the magnetic reconnection occurs. During the highly nonlinear ELM crash, the ELM filaments are cut from the main plasma due to the strong sheared mean flow that is nonlinearly generated via the Maxwell stress tensor.
Alignment of suprathermally rotating grains
Lazarian, A.
1995-12-01
It is shown that mechanical alignment can be efficient for suprathermally rotating grains, provided that they drift with supersonic velocities. Such a drift should be widely spread due to both Alfvenic waves and ambipolar diffusion. Moreover, if suprathermal rotation is caused by grain interaction with a radiative flux, it is shown that mechanical alignment may be present even in the absence of supersonic drift. This means that the range of applicability of mechanical alignment is wider than generally accepted and that it can rival the paramagnetic one. We also study the latter mechanism and re-examine the interplay between poisoning of active sites and desorption of molecules blocking the access to the active sites of H_2 formation, in order to explain the observed poor alignment of small grains and good alignment of large grains. To obtain a more comprehensive picture of alignment, we briefly discuss the alignment by radiation fluxes and by grain magnetic moments.
Kick velocity induced by magnetic dipole and quadrupole radiation
Kojima, Yasufumi
2010-01-01
We examine the recoil velocity induced by the superposition of the magnetic dipole and quadrupole radiation from a pulsar/magnetar born with rapid rotation. The resultant velocity depends on not the magnitude, but rather the ratio of the two moments and their geometrical configuration. The model does not necessarily lead to high spatial velocity for a magnetar with a strong magnetic field, which is consistent with the recent observational upper bound. The maximum velocity predicted with this model is slightly smaller than that of observed fast-moving pulsars.
Measurement of Phase Difference for Micromachined Gyros Driven by Rotating Aircraft
Wei Zhang; Zengping Zhang; Fuxue Zhang
2013-01-01
This paper presents an approach for realizing a phase difference measurement of a new gyro. A silicon micromachined gyro was mounted on rotating aircraft for aircraft attitude control. Aircraft spin drives the silicon pendulum of a gyro rotating at a high speed so that it can sense the transverse angular velocity of the rotating aircraft based on the gyroscopic precession principle when the aircraft has transverse rotation. In applications of the rotating aircraft single channel control syste...
EXPERIMENTAL STUDY OF A ROTATING PACKED BED DISTILLATION COLUMN
Nascimento, JVS; Ravagnani, TMK; Pereira, JAFR
2009-01-01
The purpose of this work was to study the mass transfer performance of rotating packed beds applying the "Higee" process. The operations were carried out with the n-hexane/n-heptane distilling system at atmospheric pressure and under total reflux conditions. The rotating speed could be varied between 300 and 2500 rpm, which provided centrifugal forces from 5 to 316 times the Earth's gravity. The effects of concentration, vapor velocity, rotating speed and packing type (two different Raschig r...
Experimental study of a rotating packed bed distillation column
Nascimento,J. V. S.; Ravagnani,T. M. K.; Pereira,J. A. F. R.
2009-01-01
The purpose of this work was to study the mass transfer performance of rotating packed beds applying the "Higee" process. The operations were carried out with the n-hexane/n-heptane distilling system at atmospheric pressure and under total reflux conditions. The rotating speed could be varied between 300 and 2500 rpm, which provided centrifugal forces from 5 to 316 times the Earth's gravity. The effects of concentration, vapor velocity, rotating speed and packing type (two different Raschig r...
Rotation and activity at 3 Gyr with Ruprecht 147
Curtis, Jason L.; Wright, J.
2014-01-01
Stellar rotation slows and magnetic activity wanes over time, making these properties useful diagnostics to determine the ages of stars. While gyrochronology and Skumanich-type activity relations have been empirically calibrated for younger stars using nearby open clusters, few benchmark clusters older than 1 Gyr exist that are close enough to have activity levels measured for their main sequence stars. Pace (2013) claims that magnetic activity can no longer be used as an age indicator after ~1 Gyr (from NGC 752), but no open cluster has been available to substantiate this claim until now. We have recently demonstrated that Ruprecht 147 is the oldest nearby open cluster, with an age of 3 Gyr and a distance of ~300 pc, which bridges the age gap between NGC 752 at 1 Gyr and M67 and the Sun at 4 Gyr (Curtis et al. 2013). We have measured projected rotational velocities (vsini) and magnetic activity indices (Calcium H&K) for >50 FGK dwarfs with high signal-to-noise spectra taken with the MMT Hectochelle, Magellan MIKE, Keck HIRES, and Tillinghast 1.5-m FAST spectrographs. We will discuss how our rotation and activity measurements for this 3 Gyr open cluster shed light on the rotation- and activity- age relations for old and late-type stars. We will also present new cluster members from our ongoing M dwarf survey with SALT RSS, discuss stellar multiplicity in light of our recently acquired Robo-AO imaging, and review our efforts to locate and characterize the white dwarf population.
Task Space Angular Velocity Blending for Real-Time Trajectory Generation
Volpe, Richard A. (Inventor)
1997-01-01
The invention is embodied in a method of controlling a robot manipulator moving toward a target frame F(sub 0) with a target velocity v(sub 0) including a linear target velocity v and an angular target velocity omega(sub 0) to smoothly and continuously divert the robot manipulator to a subsequent frame F(sub 1) by determining a global transition velocity v(sub 1), the global transition velocity including a linear transition velocity v(sub 1) and an angular transition velocity omega(sub 1), defining a blend time interval 2(tau)(sub 0) within which the global velocity of the robot manipulator is to be changed from a global target velocity v(sub 0) to the global transition velocity v(sub 1) and dividing the blend time interval 2(tau)(sub 0) into discrete time segments (delta)t. During each one of the discrete time segments delta t of the blend interval 2(tau)(sub 0), a blended global velocity v of the manipulator is computed as a blend of the global target velocity v(sub 0) and the global transition velocity v(sub 1), the blended global velocity v including a blended angular velocity omega and a blended linear velocity v, and then, the manipulator is rotated by an incremental rotation corresponding to an integration of the blended angular velocity omega over one discrete time segment (delta)t.
Cosmology and galactic rotation curves
Mannheim, P D
1995-01-01
We explore the possibility that the entire departure of galactic rotational velocities from their luminous Newtonian expectation be cosmological in origin, and show that within the framework of conformal gravity (but not Einstein gravity apparently) every static observer sees the overall Hubble flow as a local universal linear potential which is able to account for available data without any need for dark matter. We find that the Universe is necessarily an open one with 3-space scalar curvature given by k = -3.5\\times 10^{-60}cm^{-2}.
The maximum rotation of a galactic disc
Bottema, R
1997-01-01
The observed stellar velocity dispersions of galactic discs show that the maximum rotation of a disc is on average 63% of the observed maximum rotation. This criterion can, however, not be applied to small or low surface brightness (LSB) galaxies because such systems show, in general, a continuously rising rotation curve until the outermost measured radial position. That is why a general relation has been derived, giving the maximum rotation for a disc depending on the luminosity, surface brightness, and colour of the disc. As a physical basis of this relation serves an adopted fixed mass-to-light ratio as a function of colour. That functionality is consistent with results from population synthesis models and its absolute value is determined from the observed stellar velocity dispersions. The derived maximum disc rotation is compared with a number of observed maximum rotations, clearly demonstrating the need for appreciable amounts of dark matter in the disc region and even more so for LSB galaxies. Matters h...
2000-01-01
Using a pulsed ultrasound field, the two-dimensional velocity vector can be determined with the invention. The method uses a transversally modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation. The new...
2000-01-01
Using a pulsed ultrasound field, the two-dimensional velocity vector can be determined with the invention. The method uses a transversally modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation. The new...
Rotation of Jets from Young Stars: New Clues from the Hubble Space Telescope Imaging Spectrograph
Coffey, D; Woitas, J; Ray, T P; Eislöffel, J; Coffey, Deirdre; Bacciotti, Francesca; Woitas, Jens; Ray, Thomas P.; Eisl\\"offel, Jochen
2004-01-01
We report findings from the first set of data in a current survey to establish conclusively whether jets from young stars rotate. We observed the bi-polar jets from the T Tauri stars TH28 and RW Aur, and the blue-shifted jet from T Tauri star LkH$\\alpha$321, using the Hubble Space Telescope Imaging Spectrograph (HST/STIS). Forbidden emission lines (FELs) show distinct and systematic velocity asymmetries of 10 -- 25 (+/- 5) km/s at a distance of 0".3 from the source, representing a (projected) distance of ~ 40 AU along the jet in the case of RW Aur, ~ 50 AU for TH28, and 165 AU in the case of LkH$\\alpha$321. These velocity asymmetries are interpreted as rotation in the initial portion of the jet where it is accelerated and collimated. For the bi-polar jets, both lobes appear to rotate in the same direction. Values obtained were in agreement with the predictions of MHD disk-wind models (Bacciotti et al 2002, Anderson et al 2003, Dougados et al 2003, Pesenti et al 2003). Finally, we determine, from derived toroi...
Energy Transfer in Rotating Turbulence
Cambon, Claude; Mansour, Nagi N.; Godeferd, Fabien S.; Rai, Man Mohan (Technical Monitor)
1995-01-01
The influence or rotation on the spectral energy transfer of homogeneous turbulence is investigated in this paper. Given the fact that linear dynamics, e.g. the inertial waves regime tackled in an RDT (Rapid Distortion Theory) fashion, cannot Affect st homogeneous isotropic turbulent flow, the study of nonlinear dynamics is of prime importance in the case of rotating flows. Previous theoretical (including both weakly nonlinear and EDQNM theories), experimental and DNS (Direct Numerical Simulation) results are gathered here and compared in order to give a self-consistent picture of the nonlinear effects of rotation on tile turbulence. The inhibition of the energy cascade, which is linked to a reduction of the dissipation rate, is shown to be related to a damping due to rotation of the energy transfer. A model for this effect is quantified by a model equation for the derivative-skewness factor, which only involves a micro-Rossby number Ro(sup omega) = omega'/(2(OMEGA))-ratio of rms vorticity and background vorticity as the relevant rotation parameter, in accordance with DNS and EDQNM results fit addition, anisotropy is shown also to develop through nonlinear interactions modified by rotation, in an intermediate range of Rossby numbers (Ro(omega) = (omega)' and Ro(omega)w greater than 1), which is characterized by a marco-Rossby number Ro(sup L) less than 1 and Ro(omega) greater than 1 which is characterized by a macro-Rossby number based on an integral lengthscale L and the micro-Rossby number previously defined. This anisotropy is mainly an angular drain of spectral energy which tends to concentrate energy in tile wave-plane normal to the rotation axis, which is exactly both the slow and the two-dimensional manifold. In Addition, a polarization of the energy distribution in this slow 2D manifold enhances horizontal (normal to the rotation axis) velocity components, and underlies the anisotropic structure of the integral lengthscales. Finally is demonstrated the
Larsson, Stig [Svaloef Weibull AB, Svaloef (Sweden); Cuingnet, Christian; Clause, Pierre [Association pour le Developpement des Culture Energetiques, Lille (France); Jakobsson, Ingvar [Swedish Univ. of Agricultural Sciences, Uppsala (Sweden); Dawson, Malcolm [Queens Univ., Northern Ireland (United Kingdom); Backlund, Arne [A and B Backlund ApS, Charlottenlund (Denmark); Mavrogianopoulus, George [Agricultural Univ. of Athens (Greece)
2003-01-01
This report summarises results and experiences gathered from field trials with recycling of pre-treated wastewater, diverted human urine mixed with water, and municipal sludge, within plantations of willow species specifically selected for biomass production. Experimental sites were established in Sweden (Roma), France (Orchies), Northern Ireland (Culmore) and Greece (Larissa). The project was carried out during a 4-year period with financial support from the EU FAIR Programme. The experimental sites were supplied with primary effluent from municipal treatment plants (Culmore and Larissa), stored industrial effluent from a chicory processing plant (Orchies), biologically treated and stored municipal wastewater (Roma) and human urine mixture from diverting low-flush toilets mixed with water (Roma). Application rates of the wastewaters or the urine mixture were equivalent to the calculated evapotranspiration rate at each site. Wastewaters were also applied up to three times this value to evaluate any possible negative effects. Estimations and evaluations were carried out mainly concerning: biomass growth, potential biological attacks of the plantations, plant water requirements, fertilisation effects of the wastewater, plant uptake of nutrients and heavy metals from applied wastewater, possible soil or groundwater impact, sanitary aspects, and potentials for removal in the soil-plant filter of nutrients and biodegradable organic material from applied wastewater. The results clearly indicated that biomass production in young willow plantations could be enhanced substantially after recycling of wastewater resources. The impact on soil and groundwater of nutrients (nitrogen and phosphorus) and heavy metals (copper, zinc, lead and cadmium) was limited, even when the application of water and nutrients exceeded the plant requirements. Also, the soil-plant system seemed to function as a natural treatment filter for pre-treated (primary settled) wastewater, with a treatment
Velocity-aligned Doppler spectroscopy
Xu, Z.; Koplitz, B.; Wittig, C.
1989-03-01
The technique of velocity-aligned Doppler spectrosocopy (VADS) is presented and discussed. For photolysis/probe experiments with pulsed initiation, VADS can yield Doppler profiles for nascent photofragments that allow detailed center-of-mass (c.m.) kinetic energy distributions to be extracted. When compared with traditional forms of Doppler spectroscopy, the improvement in kinetic energy resolution is dramatic. Changes in the measured profiles are a consequence of spatial discrimination (i.e., focused and overlapping photolysis and probe beams) and delayed observation. These factors result in the selective detection of species whose velocities are aligned with the wave vector of the probe radiation k/sub pr/, thus revealing the speed distribution along k/sub pr/ rather than the distribution of nascent velocity components projected upon this direction. Mathematical details of the procedure used to model VADS are given, and experimental illustrations for HI, H/sub 2/S, and NH/sub 3/ photodissociation are presented. In these examples, pulsed photodissociation produces H atoms that are detected by sequential two-photon, two-frequency ionization via Lyman-..cap alpha.. with a pulsed laser (121.6+364.7 nm), and measuring the Lyman-..cap alpha.. Doppler profile as a function of probe delay reveals both internal and c.m. kinetic energy distributions for the photofragments. Strengths and weaknesses of VADS as a tool for investigating photofragmentation phenomena are also discussed.
Wu, Wen Hua; Meijer, Onno G.; Bruijn, Sjoerd M.; Hu, Hai; Van Dieën, Jaap H.; Lamoth, Claudine J. C.; Van Royen, Barend J.; Beek, Peter J.
2008-01-01
Walking is impaired in Pregnancy-related Pelvic girdle Pain (PPP). Walking velocity is reduced, and in postpartum PPP relative phase between horizontal pelvis and thorax rotations was found to be lower at higher velocities, and rotational amplitudes tended to be larger. While attempting to confirm t
CRITICISM OF LAKES ANALYSIS OF THE ROTATION CURVES OF DWARF SPIRALS
MILGROM, M
1991-01-01
Lake (1989) analyzes the rotation curves of a few dwarf spiral galaxies, and claims that their observed rotation velocities are, systematically, smaller than the velocities predicted by MOND. I point out some facts that should have been, at least, mentioned by Lake, as they are essential for assessi
Rotating optical tubes for vertical transport of atoms
Al Rsheed, Anwar; Lyras, Andreas; Aldossary, Omar M.; Lembessis, Vassilis E.
2016-12-01
The classical dynamics of a cold atom trapped inside a vertical rotating helical optical tube (HOT) is investigated by taking also into account the gravitational field. The resulting equations of motion are solved numerically. The rotation of the HOT induces a vertical motion for an atom initially at rest. The motion is a result of the action of two inertial forces, namely, the centrifugal force and the Coriolis force. Both inertial forces force the atom to rotate in a direction opposite to that of the angular velocity of the HOT. The frequency and the turning points of the atom's global oscillation can be controlled by the value and the direction of the angular velocity of the HOT. However, at large values of the angular velocity of the HOT the atom can escape from the global oscillation and be transported along the axis of the HOT. In this case, the rotating HOT operates as an optical Archimedes' screw for atoms.
Rotating Optical Tubes: An Archimedes' Screw for Atoms
Rsheed, Anwar Al; Aldossary, Omar M; Lembessis, Vassilis E
2016-01-01
The classical dynamics of a cold atom trapped inside a vertical rotating helical optical tube (HOT) is investigated by taking also into account the gravitational field. The resulting equations of motion are solved numerically. The rotation induces a vertical motion for an atom initially at rest. The motion is a result of the action of two inertial forces, namely the centrifugal force and the Coriolis force. Both inertial forces force the atom to rotate in a direction opposite to that of the angular velocity of the HOT. The frequency and the turning points of the atom's global oscillation can be controlled by the value and the direction of the angular velocity of the HOT. However, at large values of the angular velocity of the HOT the atom can escape from the global oscillation and be transported along the axis of the HOT. In this case, the rotating HOT operates as an Optical Archimedes' Screw (OAS) for atoms.
Rapid Rotation Above and Below the Substellar Boundary
Basri, G.
1999-05-01
I present the results of a multiyear survey of very low mass stars and brown dwarfs, at high spectral resolution. The echelle spectra were gathered with the HIRES spectrometer at the Keck Observatory. One primary purpose was to determine rotational velocities for many objects of the late M and L spectral classes. Some of these objects are confirmed brown dwarfs, others are stars near the bottom of the main sequence, and some might be either. I show that the initial indication provided by BRI 0021, that such objects tend to be rapidly rotating and display little H-alpha emission, proves to be a common characteristic. There is a general trend to higher rotation velocities as one looks to objects of lower luminosity; the fastest rotator found so far is the brown dwarf Kelu-1 at 80 km/s (which implies a rotation period of about 90 minutes!). The most active object, PC 0025 (which may well be a brown dwarf), is a relatively slow rotator and probably very young. I discuss a possible explanation for these results: the dynamos for these objects are fully turbulent, driven by convection (and therefore indirectly by the object's luminosity), and quenched when the rotational velocities become too fast in comparison to the convective velocities. I thank the NSF for its support through grant AST96-18439.
Back to epicycles - relativistic Coulomb systems in velocity space
Ben-Ya'acov, Uri
2017-05-01
The study of relativistic Coulomb systems in velocity space is prompted by the fact that the study of Newtonian Kepler/Coulomb systems in velocity space, although less familiar than the analytic solutions in ordinary space, provides a much simpler (also more elegant) method. The simplicity and elegance of the velocity-space method derives from the linearity of the velocity equation, which is the unique feature of 1/r interactions for Newtonian and relativistic systems alike. The various types of possible trajectories are presented, their properties deduced from the orbits in velocity space, accompanied with illustrations. In particular, it is found that the orbits traversed in the relativistic velocity space (which is hyperbolic (H 3) rather than Euclidean) are epicyclic - circles whose centres also rotate - thus the title. Dedicated to the memory of J. D. Bekenstein - physicist, teacher and human
Terminal Velocity Infall in QSO Absorption Line Halos
Benjamin, Robert A.
We explore the hypothesis that clouds detected in quasar absorption line systems are falling at a terminal velocity toward the center of high redshift gaseous galactic halos. Since both the ionization level and terminal velocity of halo clouds increase with increasing distance from the central galaxy, velocity resolved profiles of highly ionized gas are predicted to have a greater width than low ionization gas. A line of sight passing through the center of gaseous halo (an idealized damped Ly alpha system), yields low ionization absorption at the velocity of the galaxy, flanked by high ionization on either side. Reasonable halo parameters yield total velocity extents for C IV of Delta v_{C IV}=100-200 km s^{-1}, in agreement with many systems observed by Lu et al (1997). The remaining systems may better described by the rotating disk model of Prochaska & Wolfe (1998). Finally, observational tests are suggested for verifying or falsifying the terminal velocity hypothesis for these systems.
Superluminal Recession Velocities
Davis, T M; Davis, Tamara M.; Lineweaver, Charles H.
2000-01-01
Hubble's Law, v=HD (recession velocity is proportional to distance), is a theoretical result derived from the Friedmann-Robertson-Walker metric. v=HD applies at least as far as the particle horizon and in principle for all distances. Thus, galaxies with distances greater than D=c/H are receding from us with velocities greater than the speed of light and superluminal recession is a fundamental part of the general relativistic description of the expanding universe. This apparent contradiction of special relativity (SR) is often mistakenly remedied by converting redshift to velocity using SR. Here we show that galaxies with recession velocities faster than the speed of light are observable and that in all viable cosmological models, galaxies above a redshift of three are receding superluminally.
The evolution of rotating very massive stars with LMC composition
Köhler, K; de Koter, A; de Mink, S E; Crowther, P A; Evans, C J; Gräfener, G; Sana, H; Sanyal, D; Schneider, F R N; Vink, J S
2015-01-01
We present a dense model grid with tailored input chemical composition appropriate for the Large Magellanic Cloud. We use a one-dimensional hydrodynamic stellar evolution code, which accounts for rotation, transport of angular momentum by magnetic fields, and stellar wind mass loss to compute our detailed models. We calculate stellar evolution models with initial masses of 70-500 Msun and with initial surface rotational velocities of 0-550 km/s, covering the core-hydrogen burning phase of evolution. We find our rapid rotators to be strongly influenced by rotationally induced mixing of helium, with quasi-chemically homogeneous evolution occurring for the fastest rotating models. Above 160 Msun, homogeneous evolution is also established through mass loss, producing pure helium stars at core hydrogen exhaustion independent of the initial rotation rate. Surface nitrogen enrichment is also found for slower rotators, even for stars that lose only a small fraction of their initial mass. For models above 150 MZAMS, a...
Synchronous states of slowly rotating pendula
Kapitaniak, Marcin [Division of Dynamics, Technical University of Lodz, Stefanowskiego 1/15, 90-924 Lodz (Poland); Centre for Applied Dynamics Research, School of Engineering, University of Aberdeen, AB24 3UE Aberdeen, Scotland (United Kingdom); Czolczynski, Krzysztof; Perlikowski, Przemysław; Stefanski, Andrzej [Division of Dynamics, Technical University of Lodz, Stefanowskiego 1/15, 90-924 Lodz (Poland); Kapitaniak, Tomasz, E-mail: tomasz.kapitaniak@p.lodz.pl [Division of Dynamics, Technical University of Lodz, Stefanowskiego 1/15, 90-924 Lodz (Poland)
2014-08-01
Coupled systems that contain rotating elements are typical in physical, biological and engineering applications and for years have been the subject of intensive studies. One problem of scientific interest, which among others occurs in such systems is the phenomenon of synchronization of different rotating parts. Despite different initial conditions, after a sufficiently long transient, the rotating parts move in the same way — complete synchronization, or a permanent constant shift is established between their displacements, i.e., the angles of rotation — phase synchronization. Synchronization occurs due to dependence of the periods of rotating elements motion and the displacement of the base on which these elements are mounted. We review the studies on the synchronization of rotating pendula and compare them with the results obtained for oscillating pendula. As an example we consider the dynamics of the system consisting of n pendula mounted on the movable beam. The pendula are excited by the external torques which are inversely proportional to the angular velocities of the pendula. As the result of such excitation each pendulum rotates around its axis of rotation. It has been assumed that all pendula rotate in the same direction or in the opposite directions. We consider the case of slowly rotating pendula and estimate the influence of the gravity on their motion. We classify the synchronous states of the identical pendula and observe how the parameters mismatch can influence them. We give evidence that synchronous states are robust as they exist in the wide range of system parameters and can be observed in a simple experiment.
Velocity moments of dark matter haloes
Wojtak, R; Gottlöber, S; Mamon, G A; Wojtak, Radoslaw; Lokas, Ewa L.; Gottloeber, Stefan; Mamon, Gary A.
2006-01-01
Using cosmological N-body simulations we study the line-of-sight velocity distribution of dark matter haloes focusing on the lowest-order even moments, dispersion and kurtosis, and their application to estimate the mass profiles of cosmological structures. For each of the ten massive haloes selected from the simulation box we determine the virial mass, concentration and the anisotropy parameter. In order to emulate observations from each halo we choose randomly 300 particles and project their velocities and positions along the line of sight and on the surface of the sky, respectively. After removing interlopers we calculate the profiles of the line-of-sight velocity moments and fit them with the solutions of the Jeans equations. The estimates of virial mass, concentration parameter and velocity anisotropy obtained in this way are in good agreement with the values found from the full 3D analysis.
Fluid physics of a rotating membrane separator
Akonur, Alp
Rotating membrane separation is a powerful dynamic filtration technique used in separation and filtration of suspensions. Rotating membrane separation is superior compared to the conventional filtration techniques owing to the special character of the flow field, namely the supercritical cylindrical Couette flow, observed in the form of nonwavy and wavy toroidal vortices. The underlying physics are investigated by extending the previous particle image velocity (PIV) measurements performed in a radial-axial plane to a radial-azimuthal plane for nonwavy Taylor Couette flow and wavy cylindrical Couette flow. These measurements are matched to previous measurements to obtain the first time- resolved, three-dimensional, three-component velocity field for cylindrical Couette flow. The nonwavy toroidal vortices of Taylor-Couette flow become stronger with increasing Taylor number. The azimuthal velocity varies axially due to the redistribution of the azimuthal momentum by the vortical motion, which results in a substantial increase in the angular momentum at outflow regions and a decrease at inflow regions. For wavy vortex flow, the waviness of the vortices results in a variation of the azimuthal velocity in any given latitudinal place. Streams of axial flow carry fluid along the length of the annulus winding around the vortices radially from the inner cylinder to the outer cylinder, and azimuthally about one-half wavelength. The azimuthal velocity near the centers of the vortices is similar to the velocity of the traveling azimuthal wave. Large shear stresses occur near the inner and outer cylinders especially at the high Taylor numbers. In the middle of the annulus, the shear stress is substantially less. In filtration flow, where radial and axial flows are imposed on cylindrical Couette flow, simultaneous use of particle image velocimetry (PIV) and particle tracking velocimetry (PTV) provides fluid and particle velocities. Results indicate no major differences in the
Angle estimation of simultaneous orthogonal rotations from 3D gyroscope measurements.
Stančin, Sara; Tomažič, Sašo
2011-01-01
A 3D gyroscope provides measurements of angular velocities around its three intrinsic orthogonal axes, enabling angular orientation estimation. Because the measured angular velocities represent simultaneous rotations, it is not appropriate to consider them sequentially. Rotations in general are not commutative, and each possible rotation sequence has a different resulting angular orientation. None of these angular orientations is the correct simultaneous rotation result. However, every angular orientation can be represented by a single rotation. This paper presents an analytic derivation of the axis and angle of the single rotation equivalent to three simultaneous rotations around orthogonal axes when the measured angular velocities or their proportions are approximately constant. Based on the resulting expressions, a vector called the simultaneous orthogonal rotations angle (SORA) is defined, with components equal to the angles of three simultaneous rotations around coordinate system axes. The orientation and magnitude of this vector are equal to the equivalent single rotation axis and angle, respectively. As long as the orientation of the actual rotation axis is constant, given the SORA, the angular orientation of a rigid body can be calculated in a single step, thus making it possible to avoid computing the iterative infinitesimal rotation approximation. The performed test measurements confirm the validity of the SORA concept. SORA is simple and well-suited for use in the real-time calculation of angular orientation based on angular velocity measurements derived using a gyroscope. Moreover, because of its demonstrated simplicity, SORA can also be used in general angular orientation notation.
Angle Estimation of Simultaneous Orthogonal Rotations from 3D Gyroscope Measurements
Sara Stančin
2011-09-01
Full Text Available A 3D gyroscope provides measurements of angular velocities around its three intrinsic orthogonal axes, enabling angular orientation estimation. Because the measured angular velocities represent simultaneous rotations, it is not appropriate to consider them sequentially. Rotations in general are not commutative, and each possible rotation sequence has a different resulting angular orientation. None of these angular orientations is the correct simultaneous rotation result. However, every angular orientation can be represented by a single rotation. This paper presents an analytic derivation of the axis and angle of the single rotation equivalent to three simultaneous rotations around orthogonal axes when the measured angular velocities or their proportions are approximately constant. Based on the resulting expressions, a vector called the simultaneous orthogonal rotations angle (SORA is defined, with components equal to the angles of three simultaneous rotations around coordinate system axes. The orientation and magnitude of this vector are equal to the equivalent single rotation axis and angle, respectively. As long as the orientation of the actual rotation axis is constant, given the SORA, the angular orientation of a rigid body can be calculated in a single step, thus making it possible to avoid computing the iterative infinitesimal rotation approximation. The performed test measurements confirm the validity of the SORA concept. SORA is simple and well-suited for use in the real-time calculation of angular orientation based on angular velocity measurements derived using a gyroscope. Moreover, because of its demonstrated simplicity, SORA can also be used in general angular orientation notation.
Rotator cuff repair - slideshow
... this page: //medlineplus.gov/ency/presentations/100229.htm Rotator cuff repair - series—Normal anatomy To use the sharing ... to slide 4 out of 4 Overview The rotator cuff is a group of muscles and tendons that ...
Energy extraction from Kerr black holes by rigidly rotating strings
Kinoshita, Shunichiro; Tanabe, Kentaro
2016-01-01
In this paper, we show that a rigidly rotating string can extract the rotational energy from a rotating black hole. We consider Nambu-Goto strings stationary with respect to a co-rotating Killing vector with an uniform angular velocity $\\omega$ in the Kerr spacetime. We show that a necessary condition of the energy-extraction process is that an effective horizon on the string worldsheet, which corresponds to the inner light surface, is inside the ergosphere of the Kerr black hole and the angular velocity $\\omega$ is less than that of the black hole $\\Omega_\\mathrm{h}$. Furthermore, we discuss global configurations of such strings in both of a slow-rotation limit and the extremal Kerr case.
Rotations of small, inertialess triaxial ellipsoids in isotropic turbulence
Pujara, Nimish
2016-01-01
The statistics of rotational motion of small, inertialess triaxial ellipsoids are computed along Lagrangian trajectories extracted from direct numerical simulations of homogeneous isotropic turbulence. The particle angular velocity and its components along the three principal axes of the particle are considered, expanding on the results presented by \\citet{ChevillardMeneveau13}. The variance of the particle angular velocity, referred to as the particle enstrophy, is found to increase for particles with elongated shapes. This trend is explained by considering the contributions of vorticity and strain-rate to particle rotation. It is found that the majority of particle enstrophy is due to fluid vorticity. Strain-rate-induced rotations, which are sensitive to shape, are mostly cancelled by strain-vorticity interactions. The remainder of the strain-rate-induced rotations are responsible for weak variations in particle enstrophy. For particles of all shapes, the majority of the enstrophy is in rotations about the ...
Near-Infrared Structure of Fast and Slow Rotating Disk Galaxies
Schechtman-Rook, Andrew
2014-01-01
We investigate the stellar disk structure of six nearby edge-on spiral galaxies using high-resolution JHKs-band images and 3D radiative transfer models. To explore how mass and environment shape spiral disks, we selected galaxies with rotational velocities between 69 150 km/sec) galaxies, only NGC 4013 has the super-thin+thin+thick nested disk structure seen in NGC 891 and the Milky Way, albeit with decreased oblateness, while NGC 1055, a disturbed massive spiral galaxy, contains disks with hz $\\lesssim$ 200 pc. NGC 4565, another fast-rotator, contains a prominent ring at a radius ~5 kpc but no super-thin disk. Despite these differences, all fast-rotating galaxies in our sample have inner truncations in at least one of their disks. These truncations lead to Freeman Type II profiles when projected face-on. Slow-rotating galaxies are less complex, lacking inner disk truncations and requiring fewer disk components to reproduce their light distributions. Super-thin disk components in undisturbed disks contribute...
Two Sun-like Superflare Stars Rotating as Slow as the Sun
Nogami, Daisaku; Honda, Satoshi; Maehara, Hiroyuki; Notsu, Shota; Shibayama, Takuya; Shibata, Kazunari
2014-01-01
We report on the results of high dispersion spectroscopy of two `superflare stars', KIC 9766237, and KIC 9944137 with Subaru/HDS. Superflare stars are G-type main sequence stars, but show gigantic flares compared to the Sun, which have been recently discovered in the data obtained with the Kepler spacecraft. Though most of these stars are thought to have a rotation period shorter than 10 days on the basis of photometric variabilities, the two targets of the present paper are estimated to have a rotation period of 21.8 d, and 25.3 d. Our spectroscopic results clarified that these stars have stellar parameters similar to those of the Sun in terms of the effective temperature, surface gravity, and metallicity. The projected rotational velocities derived by us are consistent with the photometric rotation period, indicating a fairy high inclination angle. The average strength of the magnetic field on the surface of these stars are estimated to be 1-20 G, by using the absorption line of Ca II 8542. We could not det...
Two sun-like superflare stars rotating as slow as the Sun*
Nogami, Daisaku; Notsu, Yuta; Honda, Satoshi; Maehara, Hiroyuki; Notsu, Shota; Shibayama, Takuya; Shibata, Kazunari
2014-04-01
We report on the results of high dispersion spectroscopy of two "superflare stars," KIC 9766237 and KIC 9944137 with Subaru/HDS. Superflare stars are G-type main sequence stars, but show gigantic flares compared to the Sun, which have recently been discovered in the data obtained with the Kepler spacecraft. Though most of these stars are thought to have a rotation period shorter than 10 d on the basis of photometric variabilities, the two targets of the present paper are estimated to have rotation periods of 21.8 d and 25.3 d. Our spectroscopic results clarified that these stars have stellar parameters similar to those of the Sun in terms of the effective temperature, surface gravity, and metallicity. The projected rotational velocities derived by us are consistent with the photometric rotation period, indicating a fairly high inclination angle. The average strength of the magnetic field on the surface of these stars are estimated to be 1-20 G, by using the absorption line of Ca II 8542. We could not detect any hint of binarity in our spectra, although more data are needed to firmly rule out the presence of an unseen low-mass companion. These results claim that the spectroscopic properties of these superflare stars are very close to those of the Sun, and support the hypothesis that the Sun might cause a superflare.
National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and sound velocity data were collected using CTD, XCTD, and XBT casts in the Arctic Ocean, Mediterranean Sea - Eastern Basin, North Pacific...
Rotational nuclear models and electron scattering
Moya de Guerra, E.
1986-05-01
A review is made of the basic formalism involved in the application of nuclear rotational models to the problem of electron scattering from axially symmetric deformed nuclei. Emphasis is made on the use of electron scattering to extract information on the nature of the collective rotational model. In this respect, the interest of using polarized beam and target is discussed with the help of illustrative examples. Concerning the nuclear structure four rotational models are considered: Two microscopic models, namely the Projected Hartree-Fock (PHF) and cranking models; and two collective models, the rigid rotor and the irrotational flow models. The problem of current conservation within the different models is also discussed.
Finite rotation and nonlinear beam kinematics
Hodges, Dewey H.
1987-01-01
Standard means of representing finite rotation in rigid-body kinematics, including orientation angles, Euler parameters, and Rodrigues parameters, are reviewed and compared. General kinematical relations for a beam theory that treats arbitrarily large rotation are then presented. The standard methods of representing finite rotations are applied to these kinematical expressions, and comparison is made among the standard methods and additional methods found in the literature, such as quasi-coordinates and linear combinations of projection angles. The method of Rodrigues parameters is shown to stand out for both its simplicity and generality when applied to beam kinematics, a result that is really missing from the literature.
Ryan, J. W.; Ma, C.; Caprette, D. S.
1993-01-01
The Goddard VLBI group reports the results of analyzing 1648 Mark 3 data sets acquired from fixed and mobile observing sites through the end of 1991, and available to the Crustal Dynamics Project. Two large solutions were used to obtain Earth rotation parameters, nutation offsets, radio source positions, site positions, site velocities, and baseline evolution. Site positions are tabulated on a yearly basis for 1979 to 1995, inclusive. Site velocities are presented in both geocentric Cartesian and topocentric coordinates. Baseline evolution is plotted for 200 baselines, and individual length determinations are presented for an additional 356 baselines. This report includes 155 quasar radio sources, 96 fixed stations and mobile sites, and 556 baselines.
Gramkow, Claus
1999-01-01
In this article two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very offten the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong...... approximations to the Riemannian metric, and that the subsequent corrections are inherient in the least squares estimation. Keywords: averaging rotations, Riemannian metric, matrix, quaternion...
Evolution induced by dry minor mergers on to Fast Rotator S0 galaxies
Tapia, Trinidad; Querejeta, Miguel; Balcells, Marc; González-Garc'\\ia, A César; Prieto, Mercedes; Aguerri, J Alfonso L; Gallego, Jesús; Zamorano, Jaime; Rodríguez-Pérez, Cristina; Borlaff, Alejandro; .,
2014-01-01
We have analysed collisionless N-body simulations of intermediate and minor dry mergers on to S0s to test whether these mergers can generate S0 galaxies with intermediate kinematics between Fast and Slow Rotators. We find that minor mergers induce a lower decrease of the global rotational support than encounters of lower mass ratios, giving rise to S0s with intermediate properties between Fast and Slow Rotators. The resulting remnants are intrinsically more triaxial, less flattened, and span the whole range of apparent ellipticities up to $\\epsilon_\\mathrm{e} \\sim 0.8$. They do not show lower apparent ellipticities in random projections than initially; on the contrary, the formation of oval distortions and the disc thickening raise the percentage of projections at $0.4 0.9$), but exhibit a wide range of triaxialities ($0.20 < T < 1.00$). In the plane of global anisotropy of velocities ($\\delta$) vs. intrinsic ellipticity ($\\epsilon_\\mathrm{e,intr}$), some of our models extend the linear trend found in ...
Gramkow, Claus
2001-01-01
In this paper two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very often the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong...
Rotation in turbulence of aquatic organisms modeled as particles
Variano, Evan; Byron, Margaret; Bellani, Gabriele
2012-11-01
We investigate which length and time scales are relevant for determining the rotation of aquatic organisms and their gametes. We are interested in parameter space beyond the Stokes regime, and also the effect of particle shape on rotation. We report experimental measurements that use custom-manufactured particles to model aquatic organisms, which are designed with the necessary optical properties so that we can measure their rotation, simultaneously with the vorticity statistics of the surrounding fluid. Lagrangian timeseries of particles' angular velocity allows investigation of rotational diffusion.
Modelling binary rotating stars by new population synthesis code BONNFIRES
Lau, Herbert H B; Schneider, Fabian R N
2013-01-01
BONNFIRES, a new generation of population synthesis code, can calculate nuclear reaction, various mixing processes and binary interaction in a timely fashion. We use this new population synthesis code to study the interplay between binary mass transfer and rotation. We aim to compare theoretical models with observations, in particular the surface nitrogen abundance and rotational velocity. Preliminary results show binary interactions may explain the formation of nitrogen-rich slow rotators and nitrogen-poor fast rotators, but more work needs to be done to estimate whether the observed frequencies of those stars can be matched.
`Superresonance' from a rotating acoustic black hole
Basak, S; Basak, Soumen; Majumdar, Parthasarathi
2003-01-01
Using the analogy between a shrinking fluid vortex (`draining bathtub'), modelled as a (2+1) dimensional fluid flow with a sink at the origin, and a rotating (2+1) dimensional black hole with an ergosphere, it is shown that a scalar sound wave is reflected from such a vortex with an {\\it amplification} for a specific range of frequencies of the incident wave, depending on the angular velocity of rotation of the vortex. We discuss the possibility of observation of this phenomenon, especially for inviscid fluids like liquid HeII, where vortices with quantized angular momentum may occur.
Resolving Two Dimensional Angular Velocity within a Rotary Tumbler
Helminiak, Nathaniel; Helminiak, David; Cariapa, Vikram; Borg, John
2015-11-01
In this study, a horizontally oriented cylindrical tumbler, filled at variable depth with cylindrical media, was rotated at various constant speeds. A monoplane layer of media was photographed with a high-speed camera and images were post processed with Particle Tracking Velocimetry (PTV) algorithms in order to resolve both the translational and rotational flow fields. Although the translational velocity fields have been well characterized, contemporary resources enabled the ability to expand upon and refine data regarding rotational characteristics of particles within a rotary tumbler. The results indicate that particles rotate according to intermittent no-slip interactions between the particles and solid body rotation. Particles within the bed, not confined to solid body rotation, exhibited behavior indicative of gearing between particles; each reacting to the tangential component of contact forming rotation chains. Furthermore, it was observed that solid body interactions corresponded to areas of confined motion, as areas of high interaction dissuaded no-slip rotation, while areas of developing flow tended towards no-slip rotation. Special thanks to: NASA Wisconsin Space Grant Consortium Program as well as Marquette University OPUS College of Engineering.
Balasubramaniam, K. S.; Keil, S. L.; Smaldone, L. A.
1996-05-01
We investigate the three dimensional structure of solar pores and their surroundings using high spatial and spectral resolution data. We present evidence that surface velocities decrease around pores with a corresponding increase in the line-of-sight (LOS) velocities. LOS velocities in pores increase with the strength of the magnetic field. Surface velocities show convergence toward a weak downflow which appear to trace boundaries resembling meso-granular and super granular flows. The observed magnetic fields in the pores appear near these boundaries. We analyze the vertical velocity structure in pores and show that they generally have downflows decreasing exponentially with height, with a scale height of about 90 km. Evidence is also presented for the expanding nature of flux tubes. Finally we describe a phenomenological model for pores. This work was supported by AFOSR Task 2311G3. LAS was partially supported by the Progetto Nazionale Astrofisica e Fisica Cosmica of MURST and Scambi Internazionali of the Universita degli Studi di Napoli Frederico II. National Solar Observatory, NOAO, is operated for the National Science Foundation by AURA, Inc.
The Relationship Between Maximum Isometric Strength and Ball Velocity in the Tennis Serve
Corbi, Francisco; Fuentes, Juan Pedro; Fernández-Fernández, Jaime
2016-01-01
Abstract The aims of this study were to analyze the relationship between maximum isometric strength levels in different upper and lower limb joints and serve velocity in competitive tennis players as well as to develop a prediction model based on this information. Twelve male competitive tennis players (mean ± SD; age: 17.2 ± 1.0 years; body height: 180.1 ± 6.2 cm; body mass: 71.9 ± 5.6 kg) were tested using maximum isometric strength levels (i.e., wrist, elbow and shoulder flexion and extension; leg and back extension; shoulder external and internal rotation). Serve velocity was measured using a radar gun. Results showed a strong positive relationship between serve velocity and shoulder internal rotation (r = 0.67; p elbow and shoulder flexion – extension, leg and back extension and shoulder external rotation (r = 0.36 – 0.53; p = 0.377 – 0.054). Bivariate and multivariate models for predicting serve velocity were developed, with shoulder flexion and internal rotation explaining 55% of the variance in serve velocity (r = 0.74; p < 0.001). The maximum isometric strength level in shoulder internal rotation was strongly related to serve velocity, and a large part of the variability in serve velocity was explained by the maximum isometric strength levels in shoulder internal rotation and shoulder flexion. PMID:28149411
Discovery of XO-6b: A Hot Jupiter Transiting a Fast Rotating F5 Star on an Oblique Orbit
Crouzet, N.; McCullough, P. R.; Long, D.; Montanes Rodriguez, P.; Lecavelier des Etangs, A.; Ribas, I.; Bourrier, V.; Hébrard, G.; Vilardell, F.; Deleuil, M.; Herrero, E.; Garcia-Melendo, E.; Akhenak, L.; Foote, J.; Gary, B.; Benni, P.; Guillot, T.; Conjat, M.; Mékarnia, D.; Garlitz, J.; Burke, C. J.; Courcol, B.; Demangeon, O.
2017-03-01
Only a few hot Jupiters are known to orbit around fast rotating stars. These exoplanets are harder to detect and characterize and may be less common than around slow rotators. Here, we report the discovery of the transiting hot Jupiter XO-6b, which orbits a bright, hot, and fast rotating star: V = 10.25, T eff⋆ = 6720 ± 100 K, v sin i ⋆ = 48 ± 3 km s‑1. We detected the planet from its transits using the XO instruments and conducted a follow-up campaign. Because of the fast stellar rotation, radial velocities taken along the orbit do not yield the planet’s mass with a high confidence level, but we secure a 3σ upper limit M p orbit with a sky-projected obliquity {\\boldsymbol{λ }}=-20\\buildrel{\\circ}\\over{.} 7+/- 2\\buildrel{\\circ}\\over{.} 3. The rotation period of the star is shorter than the orbital period of the planet: P rot P orb = 3.77 days. Thus, this system stands in a largely unexplored regime of dynamical interactions between close-in giant planets and their host stars.
Rotating and rolling rigid bodies and the "hairy ball" theorem
Bormashenko, Edward; Kazachkov, Alexander
2017-06-01
Rotating and rolling rigid bodies exemplify a fascinating theorem of topology, jokingly called the "hairy ball" theorem, which demands that any continuous tangent vector field on the sphere has at least one point where the field is zero. We demonstrate via a gedanken experiment how drilling through a rotating ball, thereby converting it into a torus, leads to the elimination of zero-velocity points on the ball surface. Using the same reasoning, zero-velocity points can be removed from the surface of a drilled spinning top. We discuss the location of zero-velocity points on the surfaces of rigid bodies rolling with no slip and with slip. Observations made from different reference frames identify various zero-velocity points. Illustrative experiments visualizing zero-velocity points are presented.
Quantitative velocity modulation spectroscopy
Hodges, James N.; McCall, Benjamin J.
2016-05-01
Velocity Modulation Spectroscopy (VMS) is arguably the most important development in the 20th century for spectroscopic study of molecular ions. For decades, interpretation of VMS lineshapes has presented challenges due to the intrinsic covariance of fit parameters including velocity modulation amplitude, linewidth, and intensity. This limitation has stifled the growth of this technique into the quantitative realm. In this work, we show that subtle changes in the lineshape can be used to help address this complexity. This allows for determination of the linewidth, intensity relative to other transitions, velocity modulation amplitude, and electric field strength in the positive column of a glow discharge. Additionally, we explain the large homogeneous component of the linewidth that has been previously described. Using this component, the ion mobility can be determined.
Rotation and flattening of globular clusters
Fall, S. M.; Frenk, C. S.
1985-01-01
Methods for measuring globular cluster ellipticities and the results of such measurements are reviewed, and the processes that determine the shapes of globular clusters and the ways in which they change with time are discussed. The use of the virial tensor theorem to study the connection between the global rotation, velocity anisotropy, and the shape of a self-gravitating system is addressed, and the employment of N-body models to simulate the evolution of globular clusters with initially anisotropic velocity distributions is examined. The application of a simple evaporation model and Fokker-Planck integrations to study the two-body diffusion in globular clusters is reviewed.
Stochl, Jan; Croudace, Tim
2013-01-01
Why some humans prefer to rotate clockwise rather than anticlockwise is not well understood. This study aims to identify the predictors of the preferred rotation direction in humans. The variables hypothesised to influence rotation preference include handedness, footedness, sex, brain hemisphere lateralisation, and the Coriolis effect (which results from geospatial location on the Earth). An online questionnaire allowed us to analyse data from 1526 respondents in 97 countries. Factor analysis showed that the direction of rotation should be studied separately for local and global movements. Handedness, footedness, and the item hypothesised to measure brain hemisphere lateralisation are predictors of rotation direction for both global and local movements. Sex is a predictor of the direction of global rotation movements but not local ones, and both sexes tend to rotate clockwise. Geospatial location does not predict the preferred direction of rotation. Our study confirms previous findings concerning the influence of handedness, footedness, and sex on human rotation; our study also provides new insight into the underlying structure of human rotation movements and excludes the Coriolis effect as a predictor of rotation.
Rasmusson, Allan; Hahn, Ute; Larsen, Jytte Overgaard
2013-01-01
to identify the specific tissue region under study. In order to use the spatial rotator in practice, however, it is necessary to be able to identify intersection points between cell boundaries and test rays in a series of parallel focal planes, also at the peripheral parts of the cell boundaries. In cases......This paper presents a new local volume estimator, the spatial rotator, which is based on measurements on a virtual 3D probe, using computer assisted microscopy. The basic design of the probe builds upon the rotator principle which requires only a few manual intersection markings, thus making...... the spatial rotator fast to use. Since a 3D probe is involved, it is expected that the spatial rotator will be more efficient than the the nucleator and the planar rotator, which are based on measurements in a single plane. An extensive simulation study shows that the spatial rotator may be more efficient...
The Prescribed Velocity Method
Nielsen, Peter Vilhelm
The- velocity level in a room ventilated by jet ventilation is strongly influenced by the supply conditions. The momentum flow in the supply jets controls the air movement in the room and, therefore, it is very important that the inlet conditions and the numerical method can generate a satisfactory...... description of this momentum flow. The Prescribed Velocity Method is a practical method for the description of an Air Terminal Device which will save grid points close to the opening and ensure the right level of the momentum flow....
Magnetohydrodynamic Flow Between Concentric Rotating Porous Cylinders
S. N. Dube
1971-10-01
Full Text Available An attempt has been made to study the steady laminar flow of a incompressible electrically conducting fluid between infinitely long concentric rotating porous cylinders under the influence of radial magnetic field. A solution has been obtained under the assumption of uniform conditions along the axis of the cylinders. The cylinders being porous, a hyperbolic radial velocity distribution has been superimposed over the circumferential velocity produced due to rotation. There is a Bernoulli type pressure variation in the radial in the direction. When the inner cylinder is at rest the shearing stress at it and the torque transmitted to it decrease as R (=v/Sub/1y/Sub1/v= v/Sub2y/Sub2/v increases and the magnetic parameter lambda (=4sigma mue/sube/sup2A/Sup2/Mue will further decrease them.
Toward Realistic Dynamics of Rotating Orbital Debris, and Implications for Lightcurve Interpretation
Ojakangas, Gregory W.; Cowardin, H.; Hill, N.
2011-01-01
Optical observations of rotating space debris near GEO contain important information on size, shape, composition, and rotational states, but these aspects are difficult to extract due to data limitations and the high number of degrees of freedom in the modeling process. For tri-axial rigid debris objects created by satellite fragmentations, the most likely initial rotation state has a large component of initial angular velocity directed along the intermediate axis of inertia, leading to large angular reorientations of the body on the timescale of the rotation period. This lends some support to the simplest possible interpretation of light curves -- that they represent sets of random orientations of the objects of study. However, effects of internal friction and solar radiation are likely to cause significant modification of rotation states within a time as short as a few orbital periods. In order to examine the rotational dynamics of debris objects under the influences of these effects, a set of seven first-order coupled equations of motion were assembled in state form: three are Euler equations describing the rates of change of the components of angular velocity in the body frame, and four describe the rates of change of the components of the unit quaternion. Quaternions are a four-dimensional extension of complex numbers that form a seamless, singularity-free representation of body orientation on S3. The Euler equations contain explicit terms describing torque from solar radiation in terms of spherical harmonics, and terms representing effects of a prescribed rate of internal friction. Numerical integrations of these equations of motion are being performed, and results will be presented. Initial tests show that internal friction without solar radiation torque leads to rotation about the maximum principal axis of inertia, as required, and solar radiation torque is expected to lead to spin-up of objects. Because the axis of maximum rotational inertia tends to be
Computer program calculates velocities and streamlines in turbomachines
Katsanis, T.
1968-01-01
Computer program calculates the velocity distribution and streamlines over widely separated blades of turbomachines. It gives the solutions of a two dimensional, subsonic, compressible nonviscous flow problem for a rotating or stationary circular cascade of blades on a blade-to-blade surface of revolution.
Tu Cheng-Xu
2014-01-01
Full Text Available The field characteristics of two side-by-side rotating circular cylinders in a cross-flow is investigated under different rotation types, at T/D = 1.11,1.6, and 3, respectively (T is the center spacing between the cylinders, and D is the cylinder diameter. A similar flow pattern which is the most efficient to narrow the lowpressure area is identified for rotation type A, independent of T/D ratio, and two typical flow patterns are found under different spacings for rotation type B and type C, respectively. It is confirmed that there is an optimal rotational speed of 1.7-2, under rotation type A to attenuate the vortices, velocity drop, and turbulence intensity tremendously. As rotational speed increases to the optimal value, both the velocity drop and turbulence intensity decrease and their distributions are smooth. The results indicate that the shear layers which are accelerated following the free-stream direction would have significant influence on the flow modification, and different rotation types actually arrange these shear layers in diverse ways to change the flow pattern. Pitch ratio is capable to transform the gap flow, which is usually including the shear layers referred, thus this parameter can modify the wake of the two cylinders at different rotation types.
Map projections cartographic information systems
Grafarend, Erik W; Syffus, Rainer
2014-01-01
This book offers a timely review of map projections including sphere, ellipsoid, rotational surfaces, and geodetic datum transformations. Coverage includes computer vision, and remote sensing space projective mappings in photogrammetry.
Theory and simulations of rotating convection
Barker, Adrian J; Lithwick, Yoram
2014-01-01
We study thermal convection in a rotating fluid, with the ultimate goal of explaining the structure of convection zones in rotating stars and planets. We first derive mixing-length theory for rapidly-rotating convection, arriving at the results of Stevenson (1979) via simple physical arguments. The theory predicts the properties of convection as a function of the imposed heat flux and rotation rate, independent of microscopic diffusivities. In particular, it predicts the mean temperature gradient; the rms velocity and temperature fluctuations; and the size of the eddies that dominate heat transport. We test all of these predictions with high resolution three-dimensional hydrodynamical simulations. The results agree remarkably well with the theory across more than two orders of magnitude in rotation rate. For example, the temperature gradient is predicted to scale as the rotation rate to the 4/5th power at fixed flux, and the simulations yield $0.75\\pm 0.06$. We conclude that the mixing length theory is a soli...
Acoustic reconstruction of the velocity field in a furnace using a characteristic flow model.
Li, Yanqin; Zhou, Huaichun; Chen, Shiying; Zhang, Yindi; Wei, Xinli; Zhao, Jinhui
2012-06-01
An acoustic method can provide a noninvasive, efficient and full-field reconstruction of aerodynamic fields in a furnace. A simple yet reasonable model is devised for reconstruction of a velocity field in a cross section of a tangential furnace from acoustic measurements based on typical physical characteristics of the field. The solenoidal component of the velocity field is modeled by a curved surface, derived by rotating a curve of Gaussian distribution, determined by six characteristic parameters, while the nonrotational component is governed by a priori knowledge. Thus the inverse problem is translated into determination of the characteristic parameters using a set of acoustic projection data. First numerical experiments were undertaken to simulate the acoustic measurement, so as to preliminarily validate the effectiveness of the model. Based on this, physical experiments under different operating conditions were performed in a pilot-scale setup to provide a further test. Hot-wire anemometry and strip floating were applied to compare with acoustic measurements. The acoustic measurements provided satisfactory consistency with both of these approaches. Nevertheless, for a field with a relatively large magnitude of air velocities, the acoustic measurement can give more reliable reconstructions. Extension of the model to measurements of hot tangential furnaces is also discussed.
On the Structure Orientation in Rotating and Sheared Homogeneous Turbulence
Aguirre, Joylene C.; Moreau, Adam F.; Jacobitz, Frank G.
2016-11-01
The results of direct numerical simulations are used to study the effect of rotation on the orientation of structures and the evolution of the turbulent kinetic energy in homogeneous sheared turbulence. Shear flows without rotation, with moderate rotation, and with strong rotation are considered and the rotation axis is either parallel or anti-parallel to the mean flow vorticity. In the case of moderate rotation, an anti-parallel configuration increases the growth rate of the turbulent kinetic energy, while a parallel configuration decreases the growth rate as compared to the flow without rotation. The orientation of turbulent structures present in the flows are characterized using the three-dimensional, two-point autocorrelation coefficient of velocity magnitude and vorticity magnitude. An ellipsoid is fitted to the surface defined by a constant autocorrelation coefficient value and the major and minor axes are used to determine the inclination angle of flow structures in the plane of shear. It was found that the inclination angle assumes a maximum value for the anti-parallel configuration with moderate rotation. Again, the inclination angle for the parallel configuration with moderate rotation is reduced as compared to the case without rotation. The smallest inclination angles are found for the strongly rotating cases. Hence, the inclination angle is directly related to the growth rate of the turbulent kinetic energy. University of San Diego Shiley-Marcos School of Engineering and McNair Scholars.
Brand, Neal; Quintanilla, John A.
2013-01-01
Using a simultaneously falling softball as a stopwatch, the terminal velocity of a whiffle ball can be obtained to surprisingly high accuracy with only common household equipment. This classroom activity engages students in an apparently daunting task that nevertheless is tractable, using a simple model and mathematical techniques at their…
The Vertical Structure of the Halo Rotation
Kinman, T. D.; Bragaglia, A.; Cacciari, C.; Buzzoni, A.; Spagna, A.
New GSC-II proper motions and radial velocities of RR Lyrae and Blue Horizontal Branch stars near the North Galactic Pole are used to show that the Galactic Halo 5 kpc above the Plane has a significantly retrograde galactic rotation. Streaming motions cannot be excluded. Based on observations collected at the Kitt Peak and TNG Observatories. Funded by MIUR-Cofin 2001 (PI: Gratton).
Velocity Map Imaging the Scattering Plane of Gas Surface Collisions
Hadden, David J; Leng, Joseph G; Greaves, Stuart J
2016-01-01
The ability of gas-surface dynamics studies to resolve the velocity distribution of the scattered species in the 2D sacattering plane has been limited by technical capabilities and only a few different approaches have been explored in recent years. In comparison, gas-phase scattering studies have been transformed by the near ubiquitous use of velocity map imaging. We describe an innovative means of introducing a surface within the electric field of a typical velocity map imaging experiment. The retention of optimum velocity mapping conditions was demonstrated by measurements of iodomethane-d3 photodissociation and SIMION calculations. To demonstrate the systems capabilities the velocity distributions of ammonia molecules scattered from a PTFE surface have been measured for multiple product rotational states.
A multilayer neural network model for perception of rotational motion
郭爱克; 孙海坚; 杨先一
1997-01-01
A multilayer neural nerwork model for the perception of rotational motion has been developed usingReichardt’s motion detector array of correlation type, Kohonen’s self-organized feature map and Schuster-Wagner’s oscillating neural network. It is shown that the unsupervised learning could make the neurons on the second layer of the network tend to be self-organized in a form resembling columnar organization of selective directions in area MT of the primate’s visual cortex. The output layer can interpret rotation information and give the directions and velocities of rotational motion. The computer simulation results are in agreement with some psychophysical observations of rotation-al perception. It is demonstrated that the temporal correlation between the oscillating neurons would be powerful for solving the "binding problem" of shear components of rotational motion.
Turbulent drag in a rotating frame
Campagne, Antoine; Gallet, Basile; Cortet, Pierre-Philippe; Moisy, Frédéric
2016-01-01
What is the turbulent drag force experienced by an object moving in a rotating fluid? This open and fundamental question can be addressed by measuring the torque needed to drive an impeller at constant angular velocity $\\omega$ in a water tank mounted on a platform rotating at a rate $\\Omega$. We report a dramatic reduction in drag as $\\Omega$ increases, down to values as low as $12$\\% of the non-rotating drag. At small Rossby number $Ro = \\omega/\\Omega$, the decrease in drag coefficient $K$ follows the approximate scaling law $K \\sim Ro$, which is predicted in the framework of nonlinear inertial wave interactions and weak-turbulence theory. However, stereoscopic particle image velocimetry measurements indicate that this drag reduction rather originates from a weakening of the turbulence intensity in line with the two-dimensionalization of the large-scale flow.
Vorticity production through rotation, shear and baroclinicity
Del Sordo, Fabio
2010-01-01
In the absence of rotation and shear, and under the assumption of constant temperature or specific entropy, purely potential forcing by localized expansion waves is known to produce irrotational flows that have no vorticity. Here we study the production of vorticity under idealized conditions when there is rotation, shear, or baroclinicity, to address the problem of vorticity generation in the interstellar medium in a systematic fashion. We use three-dimensional periodic box numerical simulations to investigate the various effects in isolation. We find that for slow rotation, vorticity production in an isothermal gas is small in the sense that the ratio of the root-mean-square values of vorticity and velocity is small compared with the wavenumber of the energy carrying motions. For Coriolis numbers above a certain level, vorticity production saturates at a value where the aforementioned ratio becomes comparable with the wavenumber of the energy carrying motions. Shear also raises the vorticity production, but...
Rotational motion of Foton M-4
Abrashkin, V. I.; Voronov, K. E.; Piyakov, I. V.; Puzin, Yu. Ya.; Sazonov, V. V.; Semkin, N. D.; Chebukov, S. Yu.
2016-07-01
The actual controlled rotational motion of the Foton M-4 satellite is reconstructed for the mode of single-axis solar orientation. The reconstruction was carried out using data of onboard measurements of vectors of angular velocity and the strength of the Earth's magnetic field. The reconstruction method is based on the reconstruction of the kinematic equations of the rotational motion of a solid body. According to the method, measurement data of both types collected at a certain time interval are processed together. Measurements of the angular velocity are interpolated by piecewise-linear functions, which are substituted in kinematic differential equations for a quaternion that defines the transition from the satellite instrument coordinate system to the inertial coordinate system. The obtained equations represent the kinematic model of the satellite rotational motion. A solution of these equations that approximates the actual motion is derived from the condition of the best (in the sense of the least squares method) match between the measurement data of the strength vector of the Earth's magnetic field and its calculated values. The described method makes it possible to reconstruct the actual rotational satellite motion using one solution of kinematic equations over time intervals longer than 10 h. The found reconstructions have been used to calculate the residual microaccelerations.
Wave propagation and group velocity
Brillouin, Léon
1960-01-01
Wave Propagation and Group Velocity contains papers on group velocity which were published during the First World War and are missing in many libraries. It introduces three different definitions of velocities: the group velocity of Lord Rayleigh, the signal velocity of Sommerfeld, and the velocity of energy transfer, which yields the rate of energy flow through a continuous wave and is strongly related to the characteristic impedance. These three velocities are identical for nonabsorbing media, but they differ considerably in an absorption band. Some examples are discussed in the last chapter
Pierson, Bob [Applied Technology Associates, Albuquerque, NM (United States); Laughlin, Darren [Applied Technology Associates, Albuquerque, NM (United States)
2013-10-29
Under this Department of Energy (DOE) grant, A-Tech Corporation d.b.a. Applied Technology Associates (ATA), seeks to develop a seven-degree-of-freedom (7-DOF) seismic measurement tool for high-temperature geothermal applications. The Rotational-Enabled 7-DOF Seismometer includes a conventional tri-axial accelerometer, a conventional pressure sensor or hydrophone, and a tri-axial rotational sensor. The rotational sensing capability is novel, based upon ATA's innovative research in rotational sensing technologies. The geothermal industry requires tools for high-precision seismic monitoring of crack formation associated with Enhanced Geothermal System (EGS) stimulation activity. Currently, microseismic monitoring is conducted by deploying many seismic tools at different depth levels along a 'string' within drilled observation wells. Costs per string can be hundreds of thousands of dollars. Processing data from the spatial arrays of linear seismometers allows back-projection of seismic wave states. In contrast, a Rotational-Enabled 7-DOF Seismometer would simultaneously measure p-wave velocity, s-wave velocity, and incident seismic wave direction all from a single point measurement. In addition, the Rotational-Enabled 7-DOF Seismometer will, by its nature, separate p- and s-waves into different data streams, simplifying signal processing and facilitating analysis of seismic source signatures and geological characterization. By adding measurements of three additional degrees-of-freedom at each level and leveraging the information from this new seismic observable, it is likely that an equally accurate picture of subsurface seismic activity could be garnered with fewer levels per hole. The key cost savings would come from better siting of the well due to increased information content and a decrease in the number of confirmation wells drilled, also due to the increase in information per well. Improved seismic tools may also increase knowledge, understanding
Isosynchronous paths on a rotating surface
Ashby, Neil
2014-01-01
In special relativity, clock networks may be self-consistently synchronized in an inertial frame by slowly transporting clocks, or by exchanging electromagnetic signals between network nodes. However, clocks at rest in a rotating coordinate system--such as on the surface of the rotating earth--cannot be self-consistently synchronized by such processes, due to the Sagnac effect. Discrepancies that arise are proportional to the area swept out by a vector from the rotation axis to the portable clock or electromagnetic pulse, projected onto a plane normal to the rotation axis. This raises the question whether paths of minimal or extremal length can be found, for which the Sagnac discrepancies are zero. This paper discusses the variational problem of finding such "isosynchronous" paths on rotating discs and rotating spheres. On a disc, the problem resembles the classical isoperimetric problem and the paths turn out to be circular arcs. On a rotating sphere, however, between any two endpoints there are an infinite ...
Relativistic Rotating Vector Model
Lyutikov, Maxim
2016-01-01
The direction of polarization produced by a moving source rotates with the respect to the rest frame. We show that this effect, induced by pulsar rotation, leads to an important correction to polarization swings within the framework of rotating vector model (RVM); this effect has been missed by previous works. We construct relativistic RVM taking into account finite heights of the emission region that lead to aberration, time-of-travel effects and relativistic rotation of polarization. Polarizations swings at different frequencies can be used, within the assumption of the radius-to-frequency mapping, to infer emission radii and geometry of pulsars.
Gulshani, Parviz
2016-01-01
We derive in a simple manner and from first principles the Inglis semi-classical phenomenological cranking model for nuclear collective rotation. The derivation transforms the nuclear Schrodinger equation (instead of the Hamiltonian) to a rotating frame using a product wavefunction and imposing no constraints on either the wavefunction or the nucleon motion. The difference from Inglis model is that the frame rotation is driven by the motions of the nucleons and not externally. Consequently, the transformed Schrodinger equation is time-reversal invariant, and the total angular momentum is the sum of those of the intrinsic system and rotating frame. In this article, we choose the rotation of the frame to be given by a combination of rigid and irrotational flows. The dynamic angular velocity of the rotating frame is determined by the angular momentum of the frame and by a moment of inertia that is determined by the nature of the flow combination. The intrinsic-system and rotating-frame angular momenta emerge to ...
Pashitskii, E. A.
2017-07-01
On the basis of a two-component (two-fluid) hydrodynamic model, it is shown that the probable phenomenon of solar core rotation with a velocity higher than the average velocity of global rotation of the Sun, discovered by the SOHO mission, can be related to fast solid-body rotation of the light hydrogen component of the solar plasma, which is caused by thermonuclear fusion of hydrogen into helium inside the hot dense solar core. Thermonuclear fusion of four protons into a helium nucleus (α-particle) creates a large free specific volume per unit particle due to the large difference between the densities of the solar plasma and nuclear matter. As a result, an efficient volumetric sink of one of the components of the solar substance—hydrogen—forms inside the solar core. Therefore, a steady-state radial proton flux converging to the center should exist inside the Sun, which maintains a constant concentration of hydrogen as it burns out in the solar core. It is demonstrated that such a converging flux of hydrogen plasma with the radial velocity v r ( r) = -β r creates a convective, v r ∂ v φ/∂ r, and a local Coriolis, v r v φ/ r,φ nonlinear hydrodynamic forces in the solar plasma, rotating with the azimuthal velocity v φ. In the absence of dissipation, these forces should cause an exponential growth of the solid-body rotation velocity of the hydrogen component inside the solar core. However, friction between the hydrogen and helium components of the solar plasma due to Coulomb collisions of protons with α-particles results in a steady-state regime of rotation of the hydrogen component in the solar core with an angular velocity substantially exceeding the global rotational velocity of the Sun. It is suggested that the observed differential (liquid-like) rotation of the visible surface of the Sun (photosphere) with the maximum angular velocity at the equator is caused by sold-body rotation of the solar plasma in the radiation zone and strong turbulence in
Galactic Rotation Described with Bulge+Disk Gravitational Models
Gallo, C F
2008-01-01
Observations reveal that mature spiral galaxies consist of stars, gases and plasma approximately distributed in a thin disk of circular shape, usually with a central bulge. The rotation velocities quickly increase from the galactic center and then achieve a constant velocity from the core to the periphery. The basic dynamic behavior of a mature spiral galaxy, such as the Milky Way, is well described by simple models balancing Newtonian gravitational forces against the centrifugal forces associated with a rotating thin axisymmetric disk. In this research, we investigate the effects of adding central bulges to thin disk gravitational models. Even with the addition of substantial central bulges, all the critical essential features of our thin disk gravitational models are preserved. (1) Balancing Newtonian gravitational and centrifugal forces at every point within the disk yields computed radial mass distributions that describe the measured rotation velocity profiles of mature spiral galaxies successfully. (2) T...
Rotating Bullets from A Variable Protostar
Chen, Xuepeng; Zhang, Qizhou; Launhardt, Ralf; Henning, Thomas
2016-01-01
We present SMA CO(2-1) observations toward the protostellar jet driven by SVS13A, a variable protostar in the NGC1333 star-forming region. The SMA CO(2-1) images show an extremely high-velocity jet composed of a series of molecular 'bullets'. Based on the SMA CO observations, we discover clear and large systematic velocity gradients, perpendicular to the jet axis, in the blueshifted and redshifted bullets. After discussing several alternative interpretations, such as twin-jets, jet precession, warped disk, and internal helical shock, we suggest that the systematic velocity gradients observed in the bullets result from the rotation of the SVS13A jet. From the SMA CO images, the measured rotation velocities are 11.7-13.7 km/s for the blueshifted bullet and 4.7+/-0.5 km/s for the redshifted bullet. The estimated specific angular momenta of the two bullets are comparable to those of dense cores, about 10 times larger than those of protostellar envelopes, and about 20 times larger than those of circumstellar disks...
Inverse Magnus effect on a rotating sphere
Kim, Jooha; Park, Hyungmin; Choi, Haecheon; Yoo, Jung Yul
2011-11-01
In this study, we investigate the flow characteristics of rotating spheres in the subcritical Reynolds number (Re) regime by measuring the drag and lift forces on the sphere and the two-dimensional velocity in the wake. The experiment is conducted in a wind tunnel at Re = 0 . 6 ×105 - 2 . 6 ×105 and the spin ratio (ratio of surface velocity to the free-stream velocity) of 0 (no spin) - 0.5. The drag coefficient on a stationary sphere remains nearly constant at around 0.52. However, the magnitude of lift coefficient is nearly zero at Re Magnus effect, depending on the magnitudes of the Reynolds number and spin ratio. The velocity field measured from a particle image velocimetry (PIV) indicates that non-zero lift coefficient on a stationary sphere at Re > 2 . 0 ×105 results from the asymmetry of separation line, whereas the inverse Magnus effect for the rotating sphere results from the differences in the boundary-layer growth and separation along the upper and lower sphere surfaces. Supported by the WCU, Converging Research Center and Priority Research Centers Program, NRF, MEST, Korea.
Electromagnetic instabilities in rotating magnetized viscous objects
Nekrasov, Anatoly
2009-01-01
We study electromagnetic streaming instabilities in thermal viscous regions of rotating astrophysical objects, such as, magnetized accretion disks, molecular clouds, their cores, and elephant trunks. The obtained results can also be applied to any regions of interstellar medium, where different equilibrium velocities between charged species can arise. We consider a weakly ionized multicomponent plasma consisting of neutrals and magnetized electrons, ions, and dust grains. The effect of perturbation of collisional frequencies due to density perturbations of species is taken into account. We obtain general expressions for perturbed velocities of species involving the thermal pressure and viscosity in the case in which perturbations propagate perpendicular to the background magnetic field. The dispersion relation is derived and investigated for axisymmetric perturbations. New compressible instabilities generated due to different equilibrium velocities of different charged species are found in the cold and therma...
Aufdenberg, J P; Berger, D H; Brummelaar, T A; Folco, E D; Foresto, V C; Kervella, P; McAlister, H A; Merand, A; Ridgway, S T; Sturmann, J; Sturmann, L; Turner, N H
2006-01-01
We have obtained high-precision interferometric measurements of Vega with the CHARA Array and FLUOR beam combiner in the K' band at projected baselines between 103m and 273m. The measured visibility amplitudes beyond the first lobe are significantly weaker than expected for a slowly rotating star characterized by a single effective temperature and surface gravity. Our measurements, when compared to synthetic visibilities and synthetic spectrophotometry from a Roche-von Zeipel gravity-darkened model atmosphere, provide strong evidence for the model of Vega as a rapidly rotating star viewed very nearly pole-on. Our best fitting model indicates that Vega is rotating at ~91% of its angular break-up rate with an equatorial velocity of 275 km/s. Together with the measured vsin(i), this velocity yields an inclination for the rotation axis of 5 degrees. For this model the pole-to-equator effective temperature difference is 2250 K, a value much larger than previously derived from spectral line analyses. The derived eq...
Evidence of radius inflation in stars approaching the slow-rotator sequence
Lanzafame, A. C.; Spada, F.; Distefano, E.
2017-01-01
Context. Average stellar radii in open clusters can be estimated from rotation periods and projected rotational velocities under the assumption that the spin axis has a random orientation. These estimates are independent of distance, interstellar absorption, and models, but their validity can be limited by lacking data (truncation) or data that only represent upper or lower limits (censoring). Aims: We present a new statistical analysis method to estimate average stellar radii in the presence of censoring and truncation. Methods: We used theoretical distribution functions of the projected stellar radius Rsini to define a likelihood function in the presence of censoring and truncation. Average stellar radii in magnitude bins were then obtained by a maximum likelihood parametric estimation procedure. Results: This method is capable of recovering the average stellar radius within a few percent with as few as aboutten measurements. Here we apply this for the first time to the dataset available for the Pleiades. We find an agreement better than ≈10 percent between the observed R vs. MK relationship and current standard stellar models for 1.2 ≥ M/M⊙ ≥ 0.85 with no evident bias. Evidence of a systematic deviation at 2σ level are found for stars with 0.8 ≥ M/M⊙ ≥ 0.6 that approach the slow-rotator sequence. Fast rotators (P Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/597/A63
Topographic instability of flow in a rotating fluid
K. I. Patarashvili
2006-01-01
Full Text Available Here are presented the results of experimental and theoretical studies on a stability of zonal geostrophic flows in the rotating layer of the shallow water. In the experiments, a special apparatus by Abastumani Astrophysical Observatory Georgian Academy of Science was used. This apparatus represents a paraboloid of rotation, which can be set in a regulable rotation around the vertical axis. Maximal diameter of the paraboloid is 1.2 m, radius of curvature in the pole is 0.698 m. In the paraboloid, water spreads on walls as a layer uniform on height under the period of rotation 1.677 s. Against a background of the rotating fluid, the zonal flows are formed by the source-sink system. It consists of two concentric circular perforations on the paraboloid bottom (width is 0.3 cm, radiuses are 8.4 and 57.3 cm, respectively; water can be pumped through them with various velocities and in all directions. It has been established that under constant vertical depth of the rotating fluid the zonal flows are stable. There are given the measurements of the radial profiles for the water level and velocity in the stationary regime. It has been found that zonal flows may lose stability under the presence of the radial gradient of full depth formed by a change of angular velocity of paraboloid rotation. An instability origin results in the loss of flow axial symmetry and in the appearance of self-excited oscillations in the zonal flow. At the given angular velocity of rotation, instability is observed only in the definite range of intensities of the source-sink system. The theoretical estimations are performed in the framework of the equations of the shallow water theory, including the terms describing the bottom friction. It has been shown that the instability of zonal flows found experimentally has a topographical nature and is related with non-monotone dependence of the potential vorticity on radius.
Flat rotation curves using scalar-tensor theories
Cervantes-Cota, Jorge L.; Rodriguez-Meza, M. A.; Nunez, Dario
2007-01-01
We computed flat rotation curves from scalar-tensor theories in their weak field limit. Our model, by construction, fits a flat rotation profile for velocities of stars. As a result, the form of the scalar field potential and DM distribution in a galaxy are determined. By taking into account the constraints for the fundamental parameters of the theory $(\\lambda, \\alpha)$, it is possible to obtain analytical results for the density profiles. For positive and negative values of $\\alpha$, the DM...
Geier, S; Podsiadlowski, Ph; Edelmann, H; Napiwotzki, R; Kupfer, T; Mueller, S
2010-01-01
The origin of hot subdwarf B stars (sdBs) is still unclear. About half of the known sdBs are in close binary systems for which common envelope ejection is the most likely formation channel. Little is known about this dynamic phase of binary evolution. Due to the tidal influence of the companion in close binary systems, the rotation of the primary becomes synchronised to its orbital motion. In this case it is possible to constrain the mass of the companion, if the primary mass, its projected rotational velocity as well as its surface gravity are known. For the first time we measured the projected rotational velocities of a large sdB binary sample from high resolution spectra. We analysed a sample of 51 sdB stars in close binaries, 40 of which have known orbital parameters comprising half of all such systems known today. Synchronisation in sdB binaries is discussed both from the theoretical and the observational point of view. The masses and the nature of the unseen companions could be constrained in 31 cases. ...
Accurate Compensation of Attitude Angle Error in a Dual-Axis Rotation Inertial Navigation System
Jiang, Rui; Yang, Gongliu; Zou, Rui; Wang, Jing; Li, Jing
2017-01-01
In the dual-axis rotation inertial navigation system (INS), besides the gyro error, accelerometer error, rolling misalignment angle error, and the gimbal angle error, the shaft swing angle and the axis non-orthogonal angle also affect the attitude accuracy. Through the analysis of the structure, we can see that the shaft swing angle and axis non-orthogonal angle will produce coning errors which cause the fluctuation of the attitude. According to the analysis of the rotation vector, it can be seen that the coning error will generate additional drift velocity along the rotating shaft, which can reduce the navigation precision of the system. In this paper, based on the establishment of the modulation average frame, the vector projection is carried out, and then the attitude conversion matrix and the attitude error matrix mainly including the shaft swing angle and axis non-orthogonal are obtained. Because the attitude angles are given under the static condition, the shaft swing angle and the axis non-orthogonal angle are estimated by the static Kalman filter (KF). This kind of KF method has been widely recognized as the standard optimal estimation tool for estimating the parameters such as coning angles (α1 , α2), initial phase angles (ϕ1,ϕ2), and the non-perpendicular angle (η). In order to carry out the system level verification, a dual axis rotation INS is designed. Through simulation and experiments, the results show that the amplitudes of the attitude angles’ variation are reduced by about 20%–30% when the shaft rotates. The attitude error equation is reasonably simplified and the calibration method is accurate enough. The attitude accuracy is further improved. PMID:28304354
Deconstructing Mental Rotation
Larsen, Axel
2014-01-01
A random walk model of the classical mental rotation task is explored in two experiments. By assuming that a mental rotation is repeated until sufficient evidence for a match/mismatch is obtained, the model accounts for the approximately linearly increasing reaction times (RTs) on positive trials...... alignment take place during fixations at very high speed....
Philip E. Pope; Jeffery O. Dawson
1989-01-01
Short-rotation plantations offer several advantages over longer, more traditional rotations. They enhance the natural productivity of better sites and of tree species with rapid juvenile growth. Returns on investment are realized in a shorter period and the risk of loss is reduced compared with long term investments. Production of wood and fiber can be maximized by...
Faraday rotation measure synthesis
Brentjens, MA; de Bruyn, AG
2005-01-01
We extend the rotation measure work of Burn ( 1966, MNRAS, 133, 67) to the cases of limited sampling of lambda(2) space and non-constant emission spectra. We introduce the rotation measure transfer function (RMTF), which is an excellent predictor of n pi ambiguity problems with the lambda(2) coverag
Le Vine, David
2016-01-01
Faraday rotation is a change in the polarization as signal propagates through the ionosphere. At L-band it is necessary to correct for this change and measurements are made on the spacecraft of the rotation angle. These figures show that there is good agreement between the SMAP measurements (blue) and predictions based on models (red).
Velocity Structure Diagnostics of Simulated Galaxy Clusters
Biffi, Veronica; Boehringer, Hans
2010-01-01
Gas motions in the hot intracluster medium of galaxy clusters have an important effect on the mass determination of the clusters through X-ray observations. The corresponding dynamical pressure has to be accounted for in addition to the hydrostatic pressure support to achieve a precise mass measurement. An analysis of the velocity structure of the ICM for simulated cluster-size haloes, especially focusing on rotational patterns, has been performed, demonstrating them to be an intermittent phenomenon, strongly related to the internal dynamics of substructures. We find that the expected build-up of rotation due to mass assembly gets easily destroyed by passages of gas-rich substructures close to the central region. Though, if a typical rotation pattern is established, the corresponding mass contribution is estimated to be up to ~17% of the total mass in the innermost region, and one has to account for it. Extending the analysis to a larger sample of simulated haloes we statistically observe that (i) the distrib...
De Lorenci, V A
1996-01-01
We investigate which mapping we have to use to compare measurements made in a rotating frame to those made in an inertial frame. Using a "Lorentz-like" coordinate transformation we obtain that creation-anihilation operators of a massless scalar field in the rotating frame are not the same as those of an inertial observer. This leads to a new vacuum state (a rotating vacuum) which is a superposition of positive and negative frequency Minkowski particles. After this, introducing an apparatus device coupled linearly with the field we obtain that there is a strong correlation between number of rotating particles (in a given state) obtained via canonical quantization and via response function of the rotating detector. Finally, we analyse polarization effects in circular accelerators in the proper frame of the electron making a connection with the inertial frame point of view.
Science and Art--Rotating and Vibrating Soap Films.
Ramme, Goran
1993-01-01
Describes activities concerning interference phenomena derived from illuminated rotating soap films. Suggests reflecting incident light off of the soap film onto a projection screen. Discusses several possible experiments, how to make soap solutions, and vibrating soap films. (MVL)
Inferring information about rotation from stellar oscillations
Goupil, M J; Lochard, J; Dziembowski, W A; Pamyatnykh, A A
2003-01-01
The first part of this paper aims at illustrating the intense scientific activity in the field of stellar rotation although, for sake of shortness, we cannot be exhaustive nor give any details. The second part is devoted to the rotation as a pertubation effect upon oscillation frequencies. The discussion focuses on one specific example: the p-modes frequency small separation which provides information about properties of the stellar inner layers. It is shown that the small separation can be affected by rotation at the level of 0.1-0.2 microHz for a 1.4 Mo model rotating with an equatorial velocity of 20 km/s at the surface. This is of the same order of magnitude as the expected precision on frequencies with a 3 months observation and must therefore be taken into account. We show however that it is possible to recover the small separation free of these contaminating effects of rotation, provided enough high quality data are available as will be with space seismic missions such as Eddington.
Rotational inhomogeneities from pre-big bang?
Giovannini, Massimo
2005-01-01
The evolution of the rotational inhomogeneities is investigated in the specific framework of four-dimensional pre-big bang models. While minimal (dilaton-driven) scenarios do not lead to rotational fluctuations, in the case of non-minimal (string-driven) models, fluid sources are present in the pre-big bang phase. The rotational modes of the geometry, coupled to the divergenceless part of the velocity field, can then be amplified depending upon the value of the barotropic index of the perfect fluids. In the light of a possible production of rotational inhomogeneities, solutions describing the coupled evolution of the dilaton field and of the fluid sources are scrutinized in both the string and Einstein frames. In semi-realistic scenarios, where the curvature divergences are regularized by means of a non-local dilaton potential, the rotational inhomogeneities are amplified during the pre-big bang phase but they decay later on. Similar analyses can also be performed when a contraction occurs directly in the str...
Basic tests of a rotation seismograph; Kaiten jishinkei no kaihatsu
Matsubayashi, H.; Kawamura, S.; Watanabe, F.; Hirai, Y.; Kasahara, K. [Nippon Geophysical Prospecting Co. Ltd., Tokyo (Japan)
1996-05-01
For the purpose of developing a rotational seismograph capable of measuring the rotational component of seismic waves, vibratory gyroscopes were installed in the ground for the measurement of vibration of the ground, and the measurements were compared with the values obtained from tests using conventional velocity type seismographs. In the experiment, the plank was hammered on the east side and west side. The seismographs were arranged in two ways: one wherein they were installed at 7 spots at intervals of 1m toward the south beginning at a position 3m south of the vibration source with their rotation axes oriented vertical, with velocity type seismographs provided at the same spots; and the other wherein three rotational seismographs were installed 3m south of the vibration source with their rotation axes respectively oriented vertical, in the direction of N-S, and in the direction of E-W, with a velocity type seismograph provided at the same spot. It was found as the result that the rotational seismograph has a flat band on the lower frequency side and that it may be applied to elastic wave observation across a wide band. Accordingly, it is expected that it will be applied to exploration that uses the SH wave, to structural assessment that uses the Love wave, and to collecting knowledge about the features of natural earthquakes. 2 refs., 8 figs.
Dark Matter Velocity Spectroscopy.
Speckhard, Eric G; Ng, Kenny C Y; Beacom, John F; Laha, Ranjan
2016-01-22
Dark matter decays or annihilations that produce linelike spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming experiments will have the precision needed. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.
Minimum Length - Maximum Velocity
Panes, Boris
2011-01-01
We study a framework where the hypothesis of a minimum length in space-time is complemented with the notion of reference frame invariance. It turns out natural to interpret the action of the obtained reference frame transformations in the context of doubly special relativity. As a consequence of this formalism we find interesting connections between the minimum length properties and the modified velocity-energy relation for ultra-relativistic particles. For example we can predict the ratio between the minimum lengths in space and time using the results from OPERA about superluminal neutrinos.
Dark Matter Velocity Spectroscopy
Speckhard, Eric G; Beacom, John F; Laha, Ranjan
2016-01-01
Dark matter decays or annihilations that produce line-like spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming and proposed experiments will make significant improvements. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.
Notsu, Yuta; Maehara, Hiroyuki; Notsu, Shota; Shibayama, Takuya; Nogami, Daisaku; Shibata, Kazunari
2014-01-01
We conducted high dispersion spectroscopic observations of 50 superflare stars with Subaru/HDS. These 50 stars were selected from the solar-type superflare stars that we had discovered from the Kepler data. More than half (34 stars) of these 50 target superflare stars show no evidence of binarity, and we estimated stellar parameters of these 34 stars in our previous study (Notsu et al. 2015, hereafter called Paper I). According to our previous studies using Kepler data, superflare stars show quasi-periodic brightness variations whose amplitude (0.1-10\\%) is much larger than that of the solar brightness variations (0.01-0.1\\%) caused by the existence of sunspots on the rotating solar surface. In this study, we investigated whether these quasi-periodic brightness variations of superflare stars are explained by the rotation of a star with fairly large starspots, by using stellar parameters derived in Paper I. First, we confirmed that the value of the projected rotational velocity $v \\sin i$ is consistent with th...
A Hydrodynamical Model of a Rotating Wind Source and Its Effects on the Collapse of a Rotating Core
Guillermo Arreaga-Garcia
2015-01-01
Full Text Available This work presents three-dimensional hydrodynamical simulations with the fully parallel GAGDET2 code, to model a rotating source that emits wind in order to study the subsequent dynamics of the wind in three independent scenarios. In the first scenario we consider several models of the wind source, which is characterized by a rotation velocity Vrot and an escape velocity Vesc, so that the models have a radially outward wind velocity magnitude Vrad given by 1, 2, 4, 6, and 8 times Vrot. In the second scenario, we study the interaction of winds emitted from a binary system in two kinds of models: one in which the source remains during the wind emission and a second one in which all the source itself becomes wind. In the third scenario we consider the interaction of a rotating source that emits wind within a collapsing and rotating core. In this scenario we consider only wind models of the second kind built over a new initial radial mesh, such that the angular velocity of the wind Ωw is 1, 100, and 1000 times the angular velocity of the core Ωc.
Flow between two stretchable rotating disks with Cattaneo-Christov heat flux model
Hayat, Tasawar; Qayyum, Sumaira; Imtiaz, Maria; Alsaedi, Ahmed
An analysis is performed to investigate flow between two stretchable rotating disks. Thermal equation is constructed by Cattaneo-Christov heat flux theory. Porous medium is also taken into account. The nonlinear partial differential equations are first converted to ordinary differential equations and then computed for the convergent series solutions. Discussion about impact of dimensionless parameters on velocities, temperature and skin friction coefficient is given. It is observed that the radial velocity at upper disk enhances for larger values of ratio of corresponding stretching rate to angular velocity. Velocity in y-direction decays with an increase in rotational parameter. Magnitude of temperature profile decays for larger Prandtl number and thermal relaxation parameter.
Combined imaging and velocity estimation by Joint Migration Inversion
Staal, X.R.
2015-01-01
Seismic imaging projects aim to reveal the structure of the earths crust from seismic data. These projects typically include three separate processing steps, being: • attenuation of multiple reflections in the seismic data. • estimating seismic wave propagation velocities from the seismic data. • ma
de Mink, S E; Izzard, R G; Sana, H; de Koter, A
2012-01-01
Rotation is thought to be a major factor in the evolution of massive stars, especially at low metallicity, with consequences for their chemical yields, ionizing flux and final fate. The natal rotation-rate distribution of stars is of high priority given its importance as a constraint on theories of massive star formation and as input for models of stellar populations in the local Universe and at high redshift. Recently, it has become clear that the majority of massive stars interact with a binary companion before they die. We investigate how this affects the distribution of rotation rates. For this purpose, we simulate a massive binary-star population typical for our Galaxy assuming continuous star formation. We find that, because of binary interaction, 20^+5_-10% of all massive main-sequence stars have projected rotational velocities in excess of 200km/s. We evaluate the effect of uncertain input distributions and physical processes and conclude that the main uncertainties are the mass transfer efficiency an...
Control of fluid-containing rotating rigid bodies
Gurchenkov, Anatoly A
2013-01-01
This book is devoted to the study of the dynamics of rotating bodies with cavities containing liquid. Two basic classes of motions are analyzed: rotation and libration. Cases of complete and partial filling of cavities with ideal liquid and complete filling with viscous liquid are treated. The volume presents a method for obtaining relations between angular velocities perpendicular to main rotation and external force momentums, which are treated as control. The developed models and methods of solving dynamical problems as well as numerical methods for solving problems of optimal control can be
High-velocity Bipolar Molecular Emission from an AGN Torus
Gallimore, Jack F.; Elitzur, Moshe; Maiolino, Roberto; Marconi, Alessandro; O'Dea, Christopher P.; Lutz, Dieter; Baum, Stefi A.; Nikutta, Robert; Impellizzeri, C. M. V.; Davies, Richard; Kimball, Amy E.; Sani, Eleonora
2016-09-01
We have detected in ALMA observations CO J=6\\to 5 emission from the nucleus of the Seyfert galaxy NGC 1068. The low-velocity (up to ±70 km s-1 relative to systemic) CO emission resolves into a 12 × 7 pc structure, roughly aligned with the nuclear radio source. Higher-velocity emission (up to ±400 km s-1) is consistent with a bipolar outflow in a direction nearly perpendicular (≃80°) to the nuclear disk. The position-velocity diagram shows that in addition to the outflow, the velocity field may also contain rotation about the disk axis. These observations provide compelling evidence in support of the disk-wind scenario for the active galactic nucleus obscuring torus.
High-Velocity Bipolar Molecular Emission from an AGN Torus
Gallimore, Jack F; Maiolino, Roberto; Marconi, Alessandro; O'Dea, Christopher P; Lutz, Dieter; Baum, Stefi A; Nikutta, Robert; Impellizzeri, C M V; Davies, Richard; Kimball, Amy E; Sani, Eleonora
2016-01-01
We have detected in ALMA observations CO J = 6 - 5 emission from the nucleus of the Seyfert galaxy NGC 1068. The low-velocity (up to +/- 70 km/s relative to systemic) CO emission resolves into a 12x7 pc structure, roughly aligned with the nuclear radio source. Higher-velocity emission (up to +/- 400 km/s) is consistent with a bipolar outflow in a direction nearly perpendicular (roughly 80 degrees) to the nuclear disk. The position-velocity diagram shows that in addition to the outflow, the velocity field may also contain rotation about the disk axis. These observations provide compelling evidence in support of the disk-wind scenario for the AGN obscuring torus.
Mass Distribution in Rotating Thin-Disk Galaxies According to Newtonian Dynamics
James Q. Feng
2014-04-01
Full Text Available An accurate computational method is presented for determining the mass distribution in a mature spiral galaxy from a given rotation curve by applying Newtonian dynamics for an axisymmetrically rotating thin disk of finite size with or without a central spherical bulge. The governing integral equation for mass distribution is transformed via a boundary-element method into a linear algebra matrix equation that can be solved numerically for rotation curves with a wide range of shapes. To illustrate the effectiveness of this computational method, mass distributions in several mature spiral galaxies are determined from their measured rotation curves. All the surface mass density profiles predicted by our model exhibit approximately a common exponential law of decay, quantitatively consistent with the observed surface brightness distributions. When a central spherical bulge is present, the mass distribution in the galaxy is altered in such a way that the periphery mass density is reduced, while more mass appears toward the galactic center. By extending the computational domain beyond the galactic edge, we can determine the rotation velocity outside the cut-off radius, which appears to continuously decrease and to gradually approach the Keplerian rotation velocity out over twice the cut-off radius. An examination of circular orbit stability suggests that galaxies with flat or rising rotation velocities are more stable than those with declining rotation velocities especially in the region near the galactic edge. Our results demonstrate the fact that Newtonian dynamics can be adequate for describing the observed rotation behavior of mature spiral galaxies.
Nedjeljko Frančula
2013-06-01
Full Text Available Map Projection Transitions is a very successful web application about map projections. The web page (http://www.jasondavies.com/maps/transition presents a world map with graticule and country borders in the oblique Aitoff projection, with the South Pole. The map is not static, but animated. The South Pole moves toward the bottom and Earth rotates around its poles. The animation lasts five seconds, after which the projection changes and movement continues for five seconds, after which the projection changes again. Names of projections appear in a separate window. There are a total of 56 projections. The South Pole eventually becomes invisible and the North Pole appears at the top. Various parts of Earth appear in the center of the map by rotating around the poles.
Effect of the geometry of workpiece on polishing velocity in free annular polishing
Quantang Fan; Jianqiang Zhu; Bao'an Zhang
2007-01-01
Base on Coulomb friction model, the workpieces with different geometry rotating in free annular polishing are simulated. From simulation, the following conclusions are drawn. The angular velocity of workpiece is higher than that of polishing pad if the ring rotates uncontrolled in free annular polishing. The circular workpiece can synchronize with polishing pad through controlling the rotation of ring, which depends on the radii of ring and workpiece, the friction coefficients of polishing pad-workpiece and ring-workpiece,and the angular velocity of polishing pad. The workpiece with sharp corner cannot contact with the ring contiguously, which causes the contact state changing and the angular velocity of workpiece fluctuating ceaselessly, and this type of workpiece should be controlled with clamp to rotate synchronistically with the polishing pad.
Rotation and Mass in the Milky Way and Spiral Galaxies
Sofue, Yoshiaki
2016-01-01
[PASJ Review Paper] Rotation curves are the basic tool for deriving the distribution of mass in spiral galaxies. In this review, we describe various methods to measure rotation curves in the Milky Way and spiral galaxies. We then describe two major methods to calculate the mass distribution using the rotation curve. By the direct method, the mass is calculated from rotation velocities without employing mass models. By the decomposition method, the rotation curve is deconvolved into multiple mass components by model fitting assuming a black hole, bulge, exponential disk and dark halo. The decomposition is useful for statistical correlation analyses among the dynamical parameters of the mass components. We also review recent observations and derived results. ( Full resolution copy is available at URL: http://www.ioa.s.u-tokyo.ac.jp/~sofue/htdocs/PASJreview2016/ )
Rotation of Boar Semen Doses During Storage Affects Sperm Quality.
Schulze, M; Rüdiger, K; Waberski, D
2015-08-01
It is common practice to rotate boar semen doses during storage for prevention of sperm sedimentation. In this study, the effect of rotation of boar semen doses during storage on sperm quality was investigated. Manual turning twice daily and automatic rotation five times per hour resulted in the following effects: alkalinization of the BTS-extender, loss of membrane integrity at day 3, and loss of motility and changes in sperm kinematics during a thermoresistance test at day 5. Using a pH-stabilized variant of BTS extender, sperm motility and velocity decreased in continuously rotated samples, whereas membrane integrity and mitochondrial activity remain unaffected. It is concluded that rotation of semen samples adversely affects sperm quality and, therefore, should no longer be recommended for AI practice.
Synchronization of magnetic dipole rotation in an ac magnetic field
Belovs, M; Cebers, A, E-mail: aceb@tesla.sal.lv [University of Latvia, Zellu-8, Riga, LV-1002 (Latvia)
2011-07-22
The synchronization of the rotation of magnetic dipoles due to weak dipolar interactions is studied. The set of equations is analyzed by the time averaging technique. It is found that dipoles synchronously oscillate at low applied fields and rotate synchronously at large applied fields. The mean angular velocity of synchronous rotation increases with the field strength and reaches a constant value equal to the angular frequency of the field above the critical value of the field strength. The critical value of the field strength above which the synchronous rotation takes place can be calculated from dimensionless parameters using a model derived from first principles by others. The values thus obtained are in good agreement with the values we obtain from a numerical simulation. Thus, we may conclude that the liquid flow observed in these systems may be caused by synchronized rotations of the dipoles.
ON THE NATURE OF RAPIDLY ROTATING SINGLE EVOLVED STARS
Da Silva, R. Rodrigues; Canto Martins, B. L.; De Medeiros, J. R., E-mail: renan@dfte.ufrn.br [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Campus Universitário, Natal RN (Brazil)
2015-03-01
We present an analysis of the nature of the rapidly rotating, apparently single giant based on rotational and radial velocity measurements carried out by the CORAVEL spectrometers. From the analyzed sample, composed of 2010 spectroscopic, apparently single, evolved stars of luminosity classes IV, III, II, and Ib with spectral types G and K, we classified 30 stars that presented unusual, moderate to rapid rotation. This work reports, for the first time, the presence of these abnormal rotators among subgiant, bright giant, and Ib supergiant stars. To date, this class of stars was reported only among giant stars of luminosity class III. Most of these abnormal rotators present an IRAS infrared excess, which, in principle, can be related to dust around these stars.
Binzel, R. P.; Green, J. R.; Opal, C. B.
1986-01-01
Thomas et al. (1984) analyzed 14 Voyager 2 images of Saturn's satellite Hyperion and interpreted them to be consistent with a coherent (nonchaotic) rotation period of 13.1 days. This interpretation was criticized by Peale and Wisdom (1984), who argued that the low sampling frequency of Voyager data does not allow chaotic or nonchaotic rotation to be distinguished. New observations obtained with a higher sampling frequency are reported here which conclusively show that the 13.1 day period found by Thomas et al. was not due to coherent rotation.
Lorenci, V.A. de; Svaiter, N.F. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)
1996-11-01
It was investigated which mapping has to be used to compare measurements made in a rotating frame to those made in an inertial frame. Using a non-Galilean coordinate transformation, the creation-annihilation operators of a massive scalar field in the rotating frame are not the same as those of an inertial observer. This leads to a new vacuum state(a rotating vacuum) which is a superposition of positive and negative frequency Minkowski particles. Polarization effects in circular accelerators in the proper frame of the electron making a connection with the inertial frame point of view were analysed. 65 refs.
Optimal technique for maximal forward rotating vaults in men's gymnastics.
Hiley, Michael J; Jackson, Monique I; Yeadon, Maurice R
2015-08-01
In vaulting a gymnast must generate sufficient linear and angular momentum during the approach and table contact to complete the rotational requirements in the post-flight phase. This study investigated the optimization of table touchdown conditions and table contact technique for the maximization of rotation potential for forwards rotating vaults. A planar seven-segment torque-driven computer simulation model of the contact phase in vaulting was evaluated by varying joint torque activation time histories to match three performances of a handspring double somersault vault by an elite gymnast. The closest matching simulation was used as a starting point to maximize post-flight rotation potential (the product of angular momentum and flight time) for a forwards rotating vault. It was found that the maximized rotation potential was sufficient to produce a handspring double piked somersault vault. The corresponding optimal touchdown configuration exhibited hip flexion in contrast to the hyperextended configuration required for maximal height. Increasing touchdown velocity and angular momentum lead to additional post-flight rotation potential. By increasing the horizontal velocity at table touchdown, within limits obtained from recorded performances, the handspring double somersault tucked with one and a half twists, and the handspring triple somersault tucked became theoretically possible. Copyright © 2015 Elsevier B.V. All rights reserved.
Rotation Profiles of Solar-like Stars with Magnetic Fields
无
2008-01-01
We investigate the rotation profile of solar-like stars with magnetic fields. A diffu-sion coefficient of magnetic angular momentum transport is deduced. Rotating stellar models with different mass incorporating the coefficient are computed to give the rotation profiles. The total angular momentum of a solar model with only hydrodynamic instabilities is about 13 times larger than that of the Sun at the age of the Sun, and this model can not reproduce quasi-solid rotation in the radiative region. However, the solar model with magnetic fields not only can reproduce an almost uniform rotation in the radiative region, but also a total angular momentum that is consistent with the helioseismic result at the 3 σ level at the age of the Sun. The rotation of solar-like stars with magnetic fields is almost uniform in the radiative region, but for models of 1.2-1.5 M⊙, there is an obvious transition region between the convective core and the radiative region, where angular velocity has a sharp radial gradient, which is different from the rotation profile of the Sun and of massive stars with magnetic fields. The change of angular velocity in the transition region increases with increasing age and mass.
Absolute rotation detection by Coriolis force measurement using optomechanics
Davuluri, Sankar; Li, Yong
2016-10-01
In this article, we present an application of the optomechanical cavities for absolute rotation detection. Two optomechanical cavities, one in each arm, are placed in a Michelson interferometer. The interferometer is placed on a rotating table and is moved with a uniform velocity of \\dot{\\bar{y}} with respect to the rotating table. The Coriolis force acting on the interferometer changes the length of the optomechanical cavity in one arm, while the length of the optomechanical cavity in the other arm is not changed. The phase shift corresponding to the change in the optomechanical cavity length is measured at the interferometer output to estimate the angular velocity of the absolute rotation. An analytic expression for the minimum detectable rotation rate corresponding to the standard quantum limit of measurable Coriolis force in the interferometer is derived. Squeezing technique is discussed to improve the rotation detection sensitivity by a factor of \\sqrt{{γ }m/{ω }m} at 0 K temperature, where {γ }m and {ω }m are the damping rate and angular frequency of the mechanical oscillator. The temperature dependence of the rotation detection sensitivity is studied.
Velocity centroids as tracers of the turbulent velocity statistics
Lazarian, A E A
2004-01-01
We use the results of magnetohydrodynamic (MHD) simulations to emulate spectroscopic observations, and produce maps of variations of velocity centroids to study their scaling properties. We compare them with those of the underlying velocity field, and analytic predictions presented in a previous paper (Lazarian & Esquivel 2003). We tested, with success, a criteria for recovering velocity statistics from velocity centroids derived in our previous work. That is, if >> (where S is a 2D map of ``unnormalized'', v velocity, and I integrated intensity map -column density-), then the structure function of the centroids is dominated by the structure function of velocity. We show that it is possible to extract the velocity statistics using centroids for subsonic and mildly supersonic turbulence (e.g. Mach numbers ~2.5). While, towards higher Mach numbers other effects could affect significantly the statistics of centroids.
Statistics of Velocity from Spectral Data Modified Velocity Centroids
Lazarian, A
2003-01-01
We address the problem of studying interstellar (ISM) turbulence using spectral line data. We construct a measure that we term modified velocity centroids (MVCs) and derive an analytical solution that relates the 2D spectra of the modified centroids with the underlying 3D velocity spectrum. We test our results using synthetic maps constructed with data obtained through simulations of compressible MHD turbulence. We prove that the MVCs are able to restore the underlying spectrum of turbulent velocity. We show that the modified velocity centroids (MVCs) are complementary to the the Velocity Channel Analysis (VCA) technique that we introduced earlier. Employed together they make determining of the velocity spectral index more reliable. At the same time we show that MVCs allow to determine velocity spectra when the underlying statistics is not a power law and/or the turbulence is subsonic.
Cup anemometer calibration: effect of flow velocity distribution
Piccato, A.; Spazzini, P. G.; Malvano, R.
2011-10-01
The effects of different working conditions and specifically of different velocity profiles on the output of a commercial cup anemometer were analysed experimentally. A simple mathematical model is also presented and provides results in line with the experiments. Results show that a cup anemometer with certain geometrical features can be calibrated through a rotating drag rig by correcting for the bias on the instrument output. The increase in uncertainty caused by this systematic correction was evaluated and applied to the results. The correction was validated by checking the compatibility of calibrations of a cup anemometer at the rotating rig and in a wind tunnel.
Bovy, Jo
2016-01-01
The spatial variations of the velocity field of local stars provide direct evidence of Galactic differential rotation. The local divergence, shear, and vorticity of the velocity field---the traditional Oort constants---can be measured based purely on astrometric measurements and in particular depend linearly on proper motion and parallax. I use data for 304,267 main-sequence stars from the Gaia DR1 Tycho-Gaia Astrometric Solution to perform a local, precise measurement of the Oort constants at a typical heliocentric distance of 230 pc. The pattern of proper motions for these stars clearly displays the expected effects from differential rotation. I measure the Oort constants to be: A = 15.3+/-0.4+/- 0.5 (syst.) km/s/kpc, B = -11.9+/-0.4 km/s/kpc, C = -3.2+/-0.4 km/s/kpc and K = -3.3+/-0.6 km/s/kpc, where the systematic uncertainty in A is due to its uncertain correction for the asymmetric drift. These measurements imply local values for the rotational frequency of \\Omega_0 = 27.1+/-0.5+/- 0.5 (syst.) km/s/kpc,...
... cuff are common. They include tendinitis, bursitis, and injuries such as tears. Rotator cuff tendons can become ... cuff depends on age, health, how severe the injury is, and how long you've had the ...
Simulating Lahars Using A Rotating Drum
Neather, Adam; Lube, Gert; Jones, Jim; Cronin, Shane
2014-05-01
A large (0.5 m in diameter, 0.15 m wide) rotating drum is used to investigate the erosion and deposition mechanics of lahars. To systematically simulate the conditions occurring in natural mass flows our experimental setup differs from the common rotating drum employed in industrial/engineering studies. Natural materials with their typical friction properties are used, as opposed to the frequently employed spherical glass beads; the drum is completely water-proof, so solid/air and solid/liquid mixtures can be investigated; the drum velocity and acceleration can be precisely controlled using a software interface to a micro-controller, allowing for the study of steady, unsteady and intermediate flow regimes. The drum has a toughened glass door, allowing high-resolution, high-speed video recording of the material inside. Vector maps of the velocities involved in the flows are obtained using particle image velocimetry (PIV). The changes in velocity direction and/or magnitude are used to locate the primary internal boundaries between layers of opposite flow direction, as well as secondary interfaces between shear layers. A range of variables can be measured: thickness and number of layers; the curvature of the free surface; frequency of avalanching; position of the centre of mass of the material; and the velocity profiles of the flowing material. Experiments to date have focussed on dry materials, and have had a fill factor of approximately 0.3. Combining these measured variables allows us to derive additional data of interest, such as mass and momentum flux. It is these fluxes that we propose will allow insight into the erosion/deposition mechanics of a lahar. A number of conclusions can be drawn to date. A primary interface separates flowing and passive region (this interface has been identified in previous studies). As well as the primary interface, the flowing layer separates into individual shear layers, with individual erosion/deposition and flow histories. This
Minimal information in velocity space
Evrard, Guillaume
1995-01-01
Jaynes' transformation group principle is used to derive the objective prior for the velocity of a non-zero rest-mass particle. In the case of classical mechanics, invariance under the classical law of addition of velocities, leads to an improper constant prior over the unbounded velocity space of classical mechanics. The application of the relativistic law of addition of velocities leads to a less simple prior. It can however be rewritten as a uniform volumetric distribution if the relativistic velocity space is given a non-trivial metric.
2D velocity fields of simulated interacting disc galaxies
Kronberger, T; Schindler, S; Ziegler, B L
2007-01-01
We investigate distortions in the velocity fields of disc galaxies and their use to reveal the dynamical state of interacting galaxies at different redshift. For that purpose, we model disc galaxies in combined N-body/hydrodynamic simulations. 2D velocity fields of the gas are extracted from these simulations which we place at different redshifts from z=0 to z=1 to investigate resolution effects on the properties of the velocity field. To quantify the structure of the velocity field we also perform a kinemetry analysis. If the galaxy is undisturbed we find that the rotation curve extracted from the 2D field agrees well with long-slit rotation curves. This is not true for interacting systems, as the kinematic axis is not well defined and does in general not coincide with the photometric axis of the system. For large (Milky way type) galaxies we find that distortions are still visible at intermediate redshifts but partly smeared out. Thus a careful analysis of the velocity field is necessary before using it for...
Electromagnetic rotational actuation.
Hogan, Alexander Lee
2010-08-01
There are many applications that need a meso-scale rotational actuator. These applications have been left by the wayside because of the lack of actuation at this scale. Sandia National Laboratories has many unique fabrication technologies that could be used to create an electromagnetic actuator at this scale. There are also many designs to be explored. In this internship exploration of the designs and fabrications technologies to find an inexpensive design that can be used for prototyping the electromagnetic rotational actuator.
Rotational spectrum of phenylglycinol
Simão, Alcides; Peña, Isabel; Cabezas, Carlos; Alonso, José L.
2014-11-01
Solid samples of phenylglycinol were vaporized by laser ablation and investigated through rotational spectroscopy in a supersonic expansion using two different techniques: chirped pulse Fourier transform microwave spectroscopy and narrow band molecular beam Fourier transform microwave spectroscopy. One conformer, bearing an O-H···N and an N-H···π intramolecular hydrogen bonds, could be successfully identified by comparison of the experimental rotational and 14N nuclear quadruple coupling constants with those predicted theoretically.
Earth rotation and geodynamics
Bogusz Janusz; Brzezinski Aleksander; Kosek Wieslaw; Nastula Jolanta
2015-01-01
This paper presents the summary of research activities carried out in Poland in 2011-2014 in the field of Earth rotation and geodynamics by several Polish research institutions. It contains a summary of works on Earth rotation, including evaluation and prediction of its parameters and analysis of the related excitation data as well as research on associated geodynamic phenomena such as geocentre motion, global sea level change and hydrological processes. The second part of the paper deals wit...
Mean velocity and moments of turbulent velocity fluctuations in the wake of a model ship propulsor
Pego, J.P. [Universitaet Erlangen-Nuernberg, LSTM, Erlangen, Lehrstuhl fuer Stroemungsmechanik, Erlangen (Germany); Faculdade de Engenharia da Universidade do Porto, Porto (Portugal); Lienhart, H.; Durst, F. [Universitaet Erlangen-Nuernberg, LSTM, Erlangen, Lehrstuhl fuer Stroemungsmechanik, Erlangen (Germany)
2007-08-15
Pod drives are modern outboard ship propulsion systems with a motor encapsulated in a watertight pod, whose shaft is connected directly to one or two propellers. The whole unit hangs from the stern of the ship and rotates azimuthally, thus providing thrust and steering without the need of a rudder. Force/momentum and phase-resolved laser Doppler anemometry (LDA) measurements were performed for in line co-rotating and contra-rotating propellers pod drive models. The measurements permitted to characterize these ship propulsion systems in terms of their hydrodynamic characteristics. The torque delivered to the propellers and the thrust of the system were measured for different operation conditions of the propellers. These measurements lead to the hydrodynamic optimization of the ship propulsion system. The parameters under focus revealed the influence of distance between propeller planes, propeller frequency of rotation ratio and type of propellers (co- or contra-rotating) on the overall efficiency of the system. Two of the ship propulsion systems under consideration were chosen, based on their hydrodynamic characteristics, for a detailed study of the swirling wake flow by means of laser Doppler anemometry. A two-component laser Doppler system was employed for the velocity measurements. A light barrier mounted on the axle of the rear propeller motor supplied a TTL signal to mark the beginning of each period, thus providing angle information for the LDA measurements. Measurements were conducted for four axial positions in the slipstream of the pod drive models. The results show that the wake of contra-rotating propeller is more homogeneous than when they co-rotate. In agreement with the results of the force/momentum measurements and with hypotheses put forward in the literature (see e.g. Poehls in Entwurfsgrundlagen fuer Schraubenpropeller, 1984; Schneekluth in Hydromechanik zum Schiffsentwurf, 1988; Breslin and Andersen in Hydrodynamics of ship propellers, 1996
Mean velocity and moments of turbulent velocity fluctuations in the wake of a model ship propulsor
Pêgo, J. P.; Lienhart, H.; Durst, F.
2007-08-01
Pod drives are modern outboard ship propulsion systems with a motor encapsulated in a watertight pod, whose shaft is connected directly to one or two propellers. The whole unit hangs from the stern of the ship and rotates azimuthally, thus providing thrust and steering without the need of a rudder. Force/momentum and phase-resolved laser Doppler anemometry (LDA) measurements were performed for in line co-rotating and contra-rotating propellers pod drive models. The measurements permitted to characterize these ship propulsion systems in terms of their hydrodynamic characteristics. The torque delivered to the propellers and the thrust of the system were measured for different operation conditions of the propellers. These measurements lead to the hydrodynamic optimization of the ship propulsion system. The parameters under focus revealed the influence of distance between propeller planes, propeller frequency of rotation ratio and type of propellers (co- or contra-rotating) on the overall efficiency of the system. Two of the ship propulsion systems under consideration were chosen, based on their hydrodynamic characteristics, for a detailed study of the swirling wake flow by means of laser Doppler anemometry. A two-component laser Doppler system was employed for the velocity measurements. A light barrier mounted on the axle of the rear propeller motor supplied a TTL signal to mark the beginning of each period, thus providing angle information for the LDA measurements. Measurements were conducted for four axial positions in the slipstream of the pod drive models. The results show that the wake of contra-rotating propeller is more homogeneous than when they co-rotate. In agreement with the results of the force/momentum measurements and with hypotheses put forward in the literature (see e.g. Poehls in Entwurfsgrundlagen für Schraubenpropeller, 1984; Schneekluth in Hydromechanik zum Schiffsentwurf, 1988; Breslin and Andersen in Hydrodynamics of ship propellers, 1996
SOAP: A Tool for the Fast Computation of Photometry and Radial Velocity Induced by Stellar Spots
Boisse, I.; Bonfils, X.; Santos, N. C.; Figueira, P.
2013-04-01
Dark spots and bright plages are present on the surface of dwarf stars from spectral types F to M, even in their low-active phase (like the Sun). Their appearance and disappearance on the stellar photosphere, combined with the stellar rotation, may lead to errors and uncertainties in the characterization of planets both in radial velocity (RV) and photometry. Spot Oscillation and Planet (SOAP) is a tool offered to the community that enables to simulate spots and plages on rotating stars and computes their impact on RV and photometric measurements. This tool will help to understand the challenges related to the knowledge of stellar activity for the next decade: detect telluric planets in the habitable zone of their stars (from G to M dwarfs), understand the activity in the low-mass end of M dwarf (on which future projects, like SPIRou or CARMENES, will focus), limitation to the characterization of the exoplanetary atmosphere (from the ground or with Spitzer, JWST), search for planets around young stars. These can be simulated with SOAP in order to search for indices and corrections to the effect of activity.
Visual control of walking velocity.
François, Matthieu; Morice, Antoine H P; Bootsma, Reinoud J; Montagne, Gilles
2011-06-01
Even if optical correlates of self-motion velocity have already been identified, their contribution to the control of displacement velocity remains to be established. In this study, we used a virtual reality set-up coupled to a treadmill to test the role of both Global Optic Flow Rate (GOFR) and Edge Rate (ER) in the regulation of walking velocity. Participants were required to walk at a constant velocity, corresponding to their preferred walking velocity, while eye height and texture density were manipulated. This manipulation perturbed the natural relationship between the actual walking velocity and its optical specification by GOFR and ER, respectively. Results revealed that both these sources of information are indeed used by participants to control walking speed, as demonstrated by a slowing down of actual walking velocity when the optical specification of velocity by either GOFR or ER gives rise to an overestimation of actual velocity, and vice versa. Gait analyses showed that these walking velocity adjustments result from simultaneous adaptations in both step length and step duration. The role of visual information in the control of self-motion velocity is discussed in relation with other factors.
An Approximate Solution for Flow between Two Disks Rotating about Distinct Axes at Different Speeds
H. Volkan Ersoy
2007-01-01
Full Text Available The flow of a linearly viscous fluid between two disks rotating about two distinct vertical axes is studied. An approximate analytical solution is obtained by taking into account the case of rotation with a small angular velocity difference. It is shown how the velocity components depend on the position, the Reynolds number, the eccentricity, the ratio of angular speeds of the disks, and the parameters satisfying the conditions u=0 and ν=0 in midplane.
Wei, Zhiyuan; Ding, Lijie; Wei, Kai; Wang,Ziwei; Dai, Rucheng
2016-01-01
The case of a rotating object traveling through viscous fluid appears in many phenomena like the banana ball and missile movement. In this work, we build a model to predict the trajectory of such rotating objects with near-cylinder geometry. The analytical expression of Magnus force is given and a wind tunnel experiment is carried out, which shows the Magnus force is well proportional to the product of angular velocity and centroid velocity. The trajectory prediction is consistent with the tr...
Rotating superconductor magnet for producing rotating lobed magnetic field lines
Hilal, Sadek K.; Sampson, William B.; Leonard, Edward F.
1978-01-01
This invention provides a rotating superconductor magnet for producing a rotating lobed magnetic field, comprising a cryostat; a superconducting magnet in the cryostat having a collar for producing a lobed magnetic field having oppositely directed adjacent field lines; rotatable support means for selectively rotating the superconductor magnet; and means for energizing the superconductor magnet.
Coriolis Effects in the Dynamics of a Rotating Elastic Structure
Brøns, Morten; Hjorth, Poul G.; Kliem, Wolfhard
1996-01-01
Small oscillations of a rotating elasticum with a mass at the free end are investigated with Poincare-Lindstedt series. It is shown that the mass moves on a figure-eight shaped curve in a direction determined by the sign of the angular velocity and hence that the Coriolis force influences...
Hybrid state-space time integration of rotating beams
Krenk, Steen; Nielsen, Martin Bjerre
2012-01-01
An efficient time integration algorithm for the dynamic equations of flexible beams in a rotating frame of reference is presented. The equations of motion are formulated in a hybrid state-space format in terms of local displacements and local components of the absolute velocity. With inspiration ...
The Kinetic Energy of a Rotating Figure Skater.
Chen, Wei R.; Troelstra, Arne A.
1998-01-01
When a rotating figure skater's fully extended arms are pulled back toward the torso, the angular velocity is noticeably increased and the kinetic energy of the skater can also be shown to increase. Discusses the change of the kinetic energy during such a process, and the work necessary for such an increase is derived using a dynamic equilibrium…
Temperature Profile of a Fluid between Two Rotating Porous Cylinders
Bal Krishan
1970-07-01
Full Text Available An exact expression for the temperature profile between two concentric rotating porous cylinders has been obtained. The results are presented graphically. For the wide gap, there is a sharp rise in temperature when the ratio between the angular velocities of the outer and the inner cylinders tends to zero.
Structure functions in rotating Rayleigh–Bénard convection
Kunnen, R.P.J.; Clercx, H.J.H.; Geurts, Bernardus J.
2011-01-01
A combined numerical–experimental investigation on the scaling of velocity structure functions in turbulent rotating Rayleigh–B´enard convection is carried out. Direct numerical simulations in a cylindrical domain and a horizontally periodic domain are compared with experiments using a cylindrical t
SOAP. A tool for the fast computation of photometry and radial velocity induced by stellar spots
Boisse, I.; Bonfils, X.; Santos, N. C.
2012-09-01
We define and put at the disposal of the community SOAP, Spot Oscillation And Planet, a software tool that simulates the effect of stellar spots and plages on radial velocimetry and photometry. This paper describes the tool release and provides instructions for its use. We present detailed tests with previous computations and real data to assess the code's performance and to validate its suitability. We characterize the variations of the radial velocity, line bisector, and photometric amplitude as a function of the main variables: projected stellar rotational velocity, filling factor of the spot, resolution of the spectrograph, linear limb-darkening coefficient, latitude of the spot, and inclination of the star. Finally, we model the spot distributions on the active stars HD 166435, TW Hya and HD 189733, which reproduce the observations. We show that the software is remarkably fast, allowing several evolutions in its capabilities that could be performed to study the next challenges in the exoplanetary field connected with the stellar variability. The tool is available at http://www.astro.up.pt/soap
Velocity structure of uppermost mantle beneath North China from Pn tomography and its implications
汪素云; 许忠淮; 裴顺平
2003-01-01
20301 Pn arrival time data are collected from the seismological bulletins of both national and regional seismic networks. Pn travel time residuals are tomographically inverted for the Pn velocity structure of uppermost mantle beneath North China. The result indicates that the average Pn velocity in North China is 7.92 km/s, and the velocity varies laterally from ?0.21 to +0.29 km/s around the average. The approximately NNE trending high and low velocity regions arrange alternatively west-eastward. From west to east we can see high velocity in the middle Ordos region, the Shanxi graben low, the Jizhong depression high, the west Shandong uplift and Bohai Sea low, and the high velocity region to the east of the Tanlu fault. In the southern boundary zone of the North China block, except for the high velocity in the Qingling Mountains region, the velocity is generally lower than the average. Obvious velocity anisotropy is seen in the Datong Cenozoic volcanic region, with the fast velocity direction in NNE-SSW. Notable velocity anisotropy is also seen around the Bay of Bohai Sea, and the fast velocity directions seem to show a rotation pattern, possibly indicating a flow-like deformation in the uppermost mantle there. The Pn velocity variations show a reversed correlation with the Earth's heat flow. The low Pn velocity regions generally show high heat flow, e.g., the Shanxi graben and Bohai Sea region. While the high Pn velocity regions usually manifest low heat flow, e.g., the region of Jizhong depression. This indicates that the Pn velocity variation in the study region is mainly aroused by the regional temperature difference in the uppermost mantle. Strong earthquakes in the crust tend to occur in the region with the abnormal low Pn velocity, or in the transition zone between high and low Pn velocity regions. The earthquakes in the low velocity region are shallower, while that in the transition zone are deeper.
Owen, Albert K.
1993-01-01
The mathematical relations between the measured velocity fields for the same compressor rotor flow field resolved by two fringe type laser anemometers at different observational locations are developed in this report. The relations allow the two sets of velocity measurements to be combined to produce a total velocity vector field for the compressor rotor. This report presents the derivation of the mathematical relations, beginning with the specification of the coordinate systems and the velocity projections in those coordinate systems. The vector projections are then transformed into a common coordinate system. The transformed vector coordinates are then combined to determine the total velocity vector. A numerical example showing the solution procedure is included.
Direct and inverse energy cascades in a forced rotating turbulence experiment
Campagne, Antoine; Moisy, Frédéric; Cortet, Pierre-Philippe
2014-01-01
We present experimental evidence for a double cascade of kinetic energy in a statistically stationary rotating turbulence experiment. Turbulence is generated by a set of vertical flaps which continuously injects velocity fluctuations towards the center of a rotating water tank. The energy transfers are evaluated from two-point third-order three-component velocity structure functions, which we measure using stereoscopic particle image velocimetry in the rotating frame. Without global rotation, the energy is transferred from large to small scales, as in classical three-dimensional turbulence. For nonzero rotation rates, the horizontal kinetic energy presents a double cascade: a direct cascade at small horizontal scales and an inverse cascade at large horizontal scales. By contrast, the vertical kinetic energy is always transferred from large to small horizontal scales, a behavior reminiscent of the dynamics of a passive scalar in two-dimensional turbulence. At the largest rotation rate the flow is nearly two-di...
A New Rotation Phenomena of Cells Induced by Homegeneous Electric Field
Hatakeyama, Toyomasa; Yagi, Hiroshi
1990-05-01
When at least two plant protoplasts are located close to each other under homogeneous electric field, almost all of the cells rotate in the vicinity of its frequency of 10 kHz and specific cells in the vicinity of 10 MHz. The first rotation occurs in the plane constituted by the connecting line between two cells and the applied electric field line. This angular velocity increases with the square of the field strength. On the other hand, the second rotation or new rotation occurs in any plane and its angular velocity complicatedly depends on the field strength. Furthermore, when two cells are arranged in such a way that their connecting line is parallel to the applied field, the second rotation occurs but the first does not. The distinctive feature of the second rotation can be explained by the anisotropic dielectric in the cell due to the shape of its vacuole.
Formation of asteroid pairs by rotational fission.
Pravec, P; Vokrouhlický, D; Polishook, D; Scheeres, D J; Harris, A W; Galád, A; Vaduvescu, O; Pozo, F; Barr, A; Longa, P; Vachier, F; Colas, F; Pray, D P; Pollock, J; Reichart, D; Ivarsen, K; Haislip, J; Lacluyze, A; Kusnirák, P; Henych, T; Marchis, F; Macomber, B; Jacobson, S A; Krugly, Yu N; Sergeev, A V; Leroy, A
2010-08-26
Pairs of asteroids sharing similar heliocentric orbits, but not bound together, were found recently. Backward integrations of their orbits indicated that they separated gently with low relative velocities, but did not provide additional insight into their formation mechanism. A previously hypothesized rotational fission process may explain their formation-critical predictions are that the mass ratios are less than about 0.2 and, as the mass ratio approaches this upper limit, the spin period of the larger body becomes long. Here we report photometric observations of a sample of asteroid pairs, revealing that the primaries of pairs with mass ratios much less than 0.2 rotate rapidly, near their critical fission frequency. As the mass ratio approaches 0.2, the primary period grows long. This occurs as the total energy of the system approaches zero, requiring the asteroid pair to extract an increasing fraction of energy from the primary's spin in order to escape. We do not find asteroid pairs with mass ratios larger than 0.2. Rotationally fissioned systems beyond this limit have insufficient energy to disrupt. We conclude that asteroid pairs are formed by the rotational fission of a parent asteroid into a proto-binary system, which subsequently disrupts under its own internal system dynamics soon after formation.
Discussion of material rotation and stress rate
Dienes, J.K.
1985-10-01
Characterization of material behavior can be divided into two parts, the analysis of deformation and the underlying physics, though these are intimately related. A significant advance in the analysis of deformation was made when the polar decomposition theorem was introduced, making it possible to separate large deformations into a stretch and a rotation. Consequences of the theorem affect the way rate processes should be characterized. In particular, rate of material rotation is different from vorticity, and the stress rate for finite strains is different from the usual stress rate of Zaremba, Jaumann, and Noll. It is convenient to define a strain rate that is different from the stretching that is the symmetric part of the velocity gradient. These concepts are described in detail in a 1979 paper. Various criticisms of that paper have appeared in the Journal of Applied Mechanics, which are discussed herein. To illustrate the distinction, it is shown that the rate of rotation in a classical vortex does not vanish, though the vorticity is zero. It is also shown that the rate of material rotation recently computed by Nemat-Nasser, which involves an eigenvalue expansion, is equivalent to the one given in the 1979 paper, which makes use of matrix inversion, and it asseverated that the matrix inversion approach is computationally more efficient. 17 refs.
Development of an optimal velocity selection method with velocity obstacle
Kim, Min Geuk; Oh, Jun Ho [KAIST, Daejeon (Korea, Republic of)
2015-08-15
The Velocity obstacle (VO) method is one of the most well-known methods for local path planning, allowing consideration of dynamic obstacles and unexpected obstacles. Typical VO methods separate a velocity map into a collision area and a collision-free area. A robot can avoid collisions by selecting its velocity from within the collision-free area. However, if there are numerous obstacles near a robot, the robot will have very few velocity candidates. In this paper, a method for choosing optimal velocity components using the concept of pass-time and vertical clearance is proposed for the efficient movement of a robot. The pass-time is the time required for a robot to pass by an obstacle. By generating a latticized available velocity map for a robot, each velocity component can be evaluated using a cost function that considers the pass-time and other aspects. From the output of the cost function, even a velocity component that will cause a collision in the future can be chosen as a final velocity if the pass-time is sufficiently long enough.
Kővári, Zs; Strassmeier, K G; Carroll, T A; Weber, M; Kriskovics, L; Oláh, K; Vida, K; Granzer, T
2016-01-01
According to most stellar dynamo theories, differential rotation (DR) plays a crucial role for the generation of toroidal magnetic fields. Numerical models predict surface differential rotation to be anti-solar for rapidly-rotating giant stars, i.e., their surface angular velocity could increase with stellar latitude. However, surface differential rotation has been derived only for a handful of individual giant stars to date. The spotted surface of the K-giant KU Pegasi is investigated in order to detect its time evolution and quantify surface differential rotation. We present altogether 11 Doppler images from spectroscopic data collected with the robotic telescope STELLA between 2006--2011. All maps are obtained with the surface reconstruction code iMap. Differential rotation is extracted from these images by detecting systematic (latitude-dependent) spot displacements. We apply a cross-correlation technique to find the best differential rotation law. The surface of KU Peg shows cool spots at all latitudes a...
Nonmodal phenomena in differentially rotating dusty plasmas
Poedts, Stefaan; Rogava, Andria D.
2000-10-01
In this paper the foundation is layed for the nonmodal investigation of velocity shear induced phenomena in a differentially rotating flow of a dusty plasma. The simplest case of nonmagnetized flow is considered. It is shown that, together with the innate properties of the dusty plasma, the presence of differential rotation, Coriolis forces, and self-gravity casts a considerable richness on the nonmodal dynamics of linear perturbations in the flow. In particular: (i) dust-acoustic waves acquire the ability to extract energy from the mean flow and (ii) shear-induced, nonperiodic modes of collective plasma behavior-shear-dust-acoustic vortices-are generated. The presence of self-gravity and the nonzero Coriolis parameter (``epicyclic shaking'') makes these collective modes transiently unstable. .
Electropumping of water with rotating electric fields
Hansen, Jesper Schmidt; De Luca, Sergio; Todd, Billy
2013-01-01
of the fluid. By selectively tuning the degree of hydrophobicity of the solid walls one can generate a net unidirectional flow. Our results for the linear streaming and angular velocities of the confined water are in general agreement with the extended hydrodynamical theory for this process, though also...... require some sort of direct intrusion into the nanofluidic system, and involve mechanical or electronic components. In this paper, we present the first nonequilibrium molecular dynamics results to demonstrate that non-intrusive electropumping of liquid water on the nanoscale can be performed by subtly...... exploiting the coupling of spin angular momentum to linear streaming momentum. A spatially uniform rotating electric field is applied to water molecules, which couples to their permanent electric dipole moments. The resulting molecular rotational momentum is converted into linear streaming momentum...
Shapes of rotating superfluid helium nanodroplets
Bernando, Charles; Tanyag, Rico Mayro P.; Jones, Curtis; Bacellar, Camila; Bucher, Maximilian; Ferguson, Ken R.; Rupp, Daniela; Ziemkiewicz, Michael P.; Gomez, Luis F.; Chatterley, Adam S.; Gorkhover, Tais; Müller, Maria; Bozek, John; Carron, Sebastian; Kwok, Justin; Butler, Samuel L.; Möller, Thomas; Bostedt, Christoph; Gessner, Oliver; Vilesov, Andrey F.
2017-02-01
Rotating superfluid He droplets of approximately 1 μm in diameter were obtained in a free nozzle beam expansion of liquid He in vacuum and were studied by single-shot coherent diffractive imaging using an x-ray free electron laser. The formation of strongly deformed droplets is evidenced by large anisotropies and intensity anomalies (streaks) in the obtained diffraction images. The analysis of the images shows that in addition to previously described axially symmetric oblate shapes, some droplets exhibit prolate shapes. Forward modeling of the diffraction images indicates that the shapes of rotating superfluid droplets are very similar to their classical counterparts, giving direct access to the droplet angular momenta and angular velocities. The analyses of the radial intensity distribution and appearance statistics of the anisotropic images confirm the existence of oblate metastable superfluid droplets with large angular momenta beyond the classical bifurcation threshold.
Hartle formalism for rotating Newtonian configurations
Boshkayev, Kuantay; Quevedo, Hernando; Kalymova, Zhanerke; Zhami, Bakytzhan
2016-11-01
We apply the Hartle formalism to study equilibrium configurations in the framework of Newtonian gravity. This approach allows one to study in a simple manner the properties of the interior gravitational field in the case of static as well as stationary rotating stars in hydrostatic equilibrium. It is shown that the gravitational equilibrium conditions reduce to a system of ordinary differential equations which can be integrated numerically. We derive all the relevant equations up to the second order in the angular velocity. Moreover, we find explicitly the total mass, the moment of inertia, the quadrupole moment, the polar and equatorial radii, the eccentricity and the gravitational binding energy of the rotating body. We also present the procedure to calculate the gravitational Love number. We test the formalism in the case of white dwarfs and show its compatibility with the known results in the literature.
Pedestrians rotation measurement in bidirectional streams
Feliciani, Claudio
2016-01-01
This study presents an experimental measurement of pedestrians' body rotation in bidirectional streams. A mock-up corridor monitored using a camera placed on azimuthal position is used to study pedestrians' behavior in unidirectional and bidirectional flows. Additionally, a commercial tablet is fixed on the chest of sample pedestrians to examine their body rotation (or yawing) which cannot be obtained using position tracking alone. Angular velocity is recorded and simultaneously stored in a central location using a wireless network, thus allowing the analysis of body movements with a high sampling rate and a limited delay. To investigate the influence of major/minor flow proportion (flow-ratio) on bidirectional streams two different situations were tested: the balanced configuration (with equal flows in both directions) and an unbalanced configuration (with different major and minor flow). Results clearly show that unidirectional flow is more stable compared to the bidirectional case, requiring less time to c...
Short rotation Wood Crops Program
Wright, L.L.; Ehrenshaft, A.R.
1990-08-01
This report synthesizes the technical progress of research projects in the Short Rotation Woody Crops Program for the year ending September 30, 1989. The primary goal of this research program, sponsored by the US Department of Energy's Biofuels and Municipal Waste Technology Division, is the development of a viable technology for producing renewable feedstocks for conversion to biofuels. One of the more significant accomplishments was the documentation that short-rotation woody crops total delivered costs could be $40/Mg or less under optimistic but attainable conditions. By taking advantage of federal subsidies such as those offered under the Conservation Reserve Program, wood energy feedstock costs could be lower. Genetic improvement studies are broadening species performance within geographic regions and under less-than-optimum site conditions. Advances in physiological research are identifying key characteristics of species productivity and response to nutrient applications. Recent developments utilizing biotechnology have achieved success in cell and tissue culture, somaclonal variation, and gene-insertion studies. Productivity gains have been realized with advanced cultural studies of spacing, coppice, and mixed-species trials. 8 figs., 20 tabs.
Velocity dependant splash behaviour
Hamlett, C. A. E.; Shirtcliffe, N. J.; McHale, G.; Ahn, S.; Doerr, S. H.; Bryant, R.; Newton, M. I.
2012-04-01
Extreme soil water repellency can occur in nature via condensation of volatile organic compounds released during wildfires and can lead to increased erosion rate. Such extreme water repellent soil can be classified as superhydrophobic and shares similar chemical and topographical features to specifically designed superhydrophobic surfaces. Previous studies using high speed videography to investigate single droplet impact behaviour on artificial superhydrophobic have revealed three distinct modes of splash behaviour (rebound, pinned and fragmentation) which are dependent on the impact velocity of the droplet. In our studies, using high-speed videography, we show that such splash behaviour can be replicated on fixed 'model' water repellent soils (hydrophobic glass beads/particles). We show that the type of splash behaviour is dependent on both the size and chemical nature of the fixed particles. The particle shape also influences the splash behaviour as shown by drop impact experiments on fixed sand samples. We have also studied soil samples, as collected from the field, which shows that the type of droplet splash behaviour can lead to enhanced soil particle transport.
Head rotation trajectories compared with eye saccades by main sequence relationships.
Stark, L; Zangemeister, W H; Edwards, J; Grinberg, J; Jones, A; Lehman, S; Lubock, P; Narayan, V; Nystrom, M
1980-08-01
A helmet apparatus permitted duration, peak velocity, and peak acceleration measurements as functions of magnitude of horizontal head rotation; these "main sequence" data give evidence for multipulse-step neurological signals appropriate for time optimal control of head rotation similar to those of saccadic eye movements.
Direct measurements of anisotropic energy transfers in a rotating turbulence experiment
Lamriben, Cyril; Moisy, Frédéric
2011-01-01
We investigate experimentally the influence of a background rotation on the energy transfers in decaying grid turbulence. The anisotropic energy flux density, ${\\bf F} ({\\bf r}) = $, where $\\delta {\\bf u}$ is the vector velocity increment over separation ${\\bf r}$, is determined for the first time using Particle Image Velocimetry. We show that rotation induces an anisotropy of the energy flux $\
Mode- and plasma rotation in a resistive shell reversed-field pinch
Malmberg, J.-A.; Brzozowski, J.; Brunsell, P. R.; Cecconello, M.; Drake, J. R.
2004-02-01
Mode rotation studies in a resistive shell reversed-field pinch, EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Control. Fusion 43, 1 (2001)] are presented. The phase relations and nonlinear coupling of the resonant modes are characterized and compared with that expected from modeling based on the hypothesis that mode dynamics can be described by a quasi stationary force balance including electromagnetic and viscous forces. Both m=0 and m=1 resonant modes are studied. The m=1 modes have rotation velocities corresponding to the plasma flow velocity (20-60 km/s) in the core region. The rotation velocity decreases towards the end of the discharge, although the plasma flow velocity does not decrease. A rotating phase locked m=1 structure is observed with a velocity of about 60 km/s. The m=0 modes accelerate throughout the discharges and reach velocities as high as 150-250 km/s. The observed m=0 phase locking is consistent with theory for certain conditions, but there are several conditions when the dynamics are not described. This is not unexpected because the assumption of quasi stationarity for the mode spectra is not fulfilled for many conditions. Localized m=0 perturbations are formed in correlation with highly transient discrete dynamo events. These perturbations form at the location of the m=1 phase locked structure, but rotate with a different velocity as they spread out in the toroidal direction.
Durazo, R.; Hernandez, X.; Cervantes Sodi, B.; Sánchez, S. F.
2017-03-01
For any MONDian extended theory of gravity where the rotation curves of spiral galaxies are explained through a change in physics rather than the hypothesis of dark matter, a generic dynamical behavior is expected for pressure supported systems: an outer flattening of the velocity dispersion profile occurring at a characteristic radius, where both the amplitude of this flat velocity dispersion and the radius at which it appears are predicted to show distinct scalings with the total mass of the system. By carefully analyzing the dynamics of globular clusters and elliptical galaxies, we are able to significantly extend the astronomical diversity of objects in which MONDian gravity has been tested, from spiral galaxies to the much larger mass range covered by pressure supported systems. We show that a universal projected velocity dispersion profile accurately describes various classes of pressure supported systems, and further, that the expectations of extended gravity are met across seven orders of magnitude in mass. These observed scalings are not expected under dark matter cosmology, and would require particular explanations tuned at the scales of each distinct astrophysical system.
Gehan, Charlotte; Michel, Eric
2016-01-01
Stellar oscillations give seismic information on the internal properties of stars. Red giants are targets of interest since they present mixed modes, which behave as pressure modes in the convective envelope and as gravity modes in the radiative core. Mixed modes thus directly probe red giant cores, and allow in particular the study of their mean core rotation. The high-quality data obtained by CoRoT and Kepler satellites represent an unprecedented perspective to obtain thousands of measurements of red giant core rotation, in order to improve our understanding of stellar physics in deep stellar interiors. We developed an automated method to obtain such core rotation measurements and validated it for stars on the red giant branch. In this work, we particularly focus on the specific application of this method to red giants having a rapid core rotation. They show complex spectra where it is tricky to disentangle rotational splittings from mixed-mode period spacings. We demonstrate that the method based on the id...