101 research outputs found
Verification of active controlled air spring model
In previous works we have described the model of actively controlled bellow-type air spring for compensation system of the vibration-isolation platform with gyroscopic stabilizer. Air pressure inside the air spring is controlled by the electro-magnetic valve, which is controlled by a signal from the displacement sensor. The experimental stand was designed and used for verification of the model. The paper is aimed on description of the model and experiments conducted for its verification
Radial correction controllers of gyroscopic stabilizer
This paper takes up the previous research paper on the considered topic and extends the proportional feedbacks of correction and compensation system by replacing them by PID controllers. The paper presents a part of research of the gyroscopic stabilizer and describes a gyroscopic stabilizer correction and compensation system. Consequently, identification of the effect of correction and compensation system parameters settings for the system behavior is described. Estimation of concrete compensation and correction settings is reported in this stud
The spectroscopic evolution of the symbiotic star AG Draconis. I.The O VI Raman, Balmer, and helium emission line variations during the outburst of 2006-2008
AG Dra is one of a small group of low metallicity S-type symbiotic binaries
with K-type giants that undergoes occasional short-term outbursts of unknown
origin. Our aim is to study the behavior of the white dwarf during an outburst
using the optical Raman lines and other emission features in the red giant
wind. The goal is to determine changes in the envelope and the wind of the
gainer in this system during a major outburst event and to study the coupling
between the UV and optical during a major outburst. Using medium and high
resolution groundbased optical spectra and comparisons with archival and
spectra, we study the evolution of the Raman O VI features and the
Balmer, He I, and He II lines during the outburst from 2006 Sept. through 2007
May and include more recent observations (2009) to study the subsequent
evolution of the source. The O VI Raman features disappeared completely at the
peak of the major outburst and the subsequent variation differs substantially
from that reported during the previous decade. The He I and He II lines, and
the Balmer lines, vary in phase with the Raman features but there is a
double-valuedness to the He I 6678, 7065 relative to the O VI Raman 6825\AA\
variations in the period between 2006-2008 that has not been previously
reported. The variations in the Raman feature ratio through the outburst
interval are consistent with the disappearance of the O VI FUV resonance wind
lines from the white dwarf and of the surrounding O ionized region
within the red giant wind provoked by the expansion and cooling of the white
dwarf photosphere.Comment: 10 pages, 15 figs. A&A (in press, accepted for publication
23/11/2009
Radial correction controllers of gyroscopic stabilizer
This paper takes up the previous research paper on the considered topic and extends the proportional feedbacks of correction and compensation system by replacing them by PID controllers. The paper presents a part of research of the gyroscopic stabilizer and describes a gyroscopic stabilizer correction and compensation system. Consequently, identification of the effect of correction and compensation system parameters settings for the system behavior is described. Estimation of concrete compensation and correction settings is reported in this stud
Time-dependent spectral-feature variations of stars displaying the B[e] phenomenon III. HD 50138
We analyse spectroscopic observations of the B[e] star HD 50138 (MWC 158,
V743 Mon, or IRAS 06491-0654), a member of the FS CMa group, obtained over the
last twenty years. Four different epochs are identified in the observational
data, where the variability of the spectral features is substantially
different. Additionally, two long periods of (3 000 +/- 500) and (5 000 +/-
1000) days are found in the variations of the equivalent widths of the H alpha
and [OI] 6300 A lines and radial velocities of the H alpha line violet peak.
Modest signatures of a regular period of ~34 days in the radial velocities of
the H alpha red peak and H beta central depression are found in the season
2013/2014. The H alpha V/R changes indicate a periodicity of ~50 days. The
correlations between individual spectral features significantly restricts the
model of the object and suggest that it is most likely a binary system with a
highly distorted disc with spiral arms around the primary component. At the
same time, no obvious signs of the secondary component has been found in the
object's spectrum
Properties and nature of Be stars 30. Reliable physical properties of a semi-detached B9.5e+G8III binary BR CMi = HD 61273 compared to those of other well studied semi-detached emission-line binaries
Reliable determination of the basic physical properties of hot emission-line
binaries with Roche-lobe filling secondaries is important for developing the
theory of mass exchange in binaries. It is a very hard task, however, which is
complicated by the presence of circumstellar matter in these systems. So far,
only a small number of systems with accurate values of component masses, radii,
and other properties are known. Here, we report the first detailed study of a
new representative of this class of binaries, BR CMi, based on the analysis of
radial velocities and multichannel photometry from several observatories, and
compare its physical properties with those for other well-studied systems. BR
CMi is an ellipsoidal variable seen under an intermediate orbital inclination
of ~51 degrees, and it has an orbital period of 12.919059(15) d and a circular
orbit. We used the disentangled component spectra to estimate the effective
temperatures 9500(200) K and 4655(50) K by comparing them with model spectra.
They correspond to spectral types B9.5e and G8III. We also used the
disentangled spectra of both binary components as templates for the 2-D
cross-correlation to obtain accurate RVs and a reliable orbital solution. Some
evidence of a secular period increase at a rate of 1.1+/-0.5 s per year was
found. This, together with a very low mass ratio of 0.06 and a normal mass and
radius of the mass gaining component, indicates that BR CMi is in a slow phase
of the mass exchange after the mass-ratio reversal. It thus belongs to a still
poorly populated subgroup of Be stars for which the origin of Balmer emission
lines is safely explained as a consequence of mass transfer between the binary
components.Comment: 17 pages, 5 figures, accepted for publication in Astronomy and
Astrophysics. appears in Astronomy and Astrophysics 201
Coherent states for Hopf algebras
Families of Perelomov coherent states are defined axiomatically in the
context of unitary representations of Hopf algebras possessing a Haar integral.
A global geometric picture involving locally trivial noncommutative fibre
bundles is involved in the construction. A noncommutative resolution of
identity formula is proved in that setup. Examples come from quantum groups.Comment: 19 pages, uses kluwer.cls; the exposition much improved; an example
of deriving the resolution of identity via coherent states for SUq(2) added;
the result differs from the proposals in literatur
Properties and nature of Be stars: 27. Orbital and recent long-term variations of the Pleiades Be star Pleione = BU Tauri
Radial-velocity variations of the H-alpha emission measured on the steep
wings of the H-alpha line, prewhitened for the long-time changes, vary
periodically with a period of (218.025 +/- 0.022)d, confirming the suspected
binary nature of the bright Be star Pleione, a member of the Pleiades cluster.
The orbit seems to have a high eccentricity over 0.7, but we also briefly
discuss the possibility that the true orbit is circular and that the
eccentricity is spurious owing to the phase-dependent effects of the
circumstellar matter. The projected angular separation of the spectroscopic
orbit is large enough to allow the detection of the binary with large optical
interferometers, provided the magnitude difference primary - secondary is not
too large. Since our data cover the onset of a new shell phase up to
development of a metallic shell spectrum, we also briefly discuss the recent
long-term changes. We confirm the formation of a new envelope, coexisting with
the previous one, at the onset of the new shell phase. We find that the full
width at half maximum of the H-alpha profile has been decreasing with time for
both envelopes. In this connection, we briefly discuss Hirata's hypothesis of
precessing gaseous disk and possible alternative scenarios of the observed
long-term changes
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