scholarly journals High-frequency variations of hydrogen spectral lines in the B3V star η UMa

2015 ◽  
Vol 5 (1) ◽  
pp. 21-23
Author(s):  
S. Pokhvala
Keyword(s):  
Time Resolution ◽  
High Frequency ◽  
Atmospheric Oxygen ◽  
Spectral Lines ◽  
Spectral Class ◽  
Balmer Lines ◽  
Hydrogen Lines ◽  
Frequency Variations

We reported the detection of high-frequency variations in the hydrogen Balmer lines in the hot star η UMa of spectral class B3V. Spectral observations of η UMa were carried out with slitless spectrograph (R∼100) installed on the 60 cm Carl Zeiss telescope in the Andrushivka Observatory. Spectra were obtained with a time resolution in the sub-second range. It has been found that the η UMa shows rapid variations in the hydrogen lines Hα, Hβ, Hγ, as well as variations in the atmospheric oxygen lines. The intensity variations in the hydrogen lines varies from 0.2% to 0.5%, and that of the oxygen lines is approximately 2%.

Short time-scale variability in the spectrum of the hot B3V star ηUMa

2020 ◽  
Vol 10 (1) ◽  
pp. 3-6
Author(s):  
S. Pokhvala
Keyword(s):  
Time Resolution ◽  
Stellar Wind ◽  
Time Scale ◽  
Atmospheric Oxygen ◽  
Short Time Scale ◽  
Low Resolution ◽  
Balmer Lines ◽  
Hydrogen Lines ◽  
Short Time ◽  
Radial Pulsations

We report the results of observations of short time-scale variability in the Hydrogen Balmer lines and HeI lines in the hot B star ηUMa. Spectral observations were carried out with the low-resolution slitless spectrograph (R∼200) installed on the 60 cm Carl Zeiss telescope in the Andrushivka Observatory, Ukraine. Spectra were obtained with a time resolution in the sub-second range. It has been found that the hot B star ηUMa shows rapid variations in the Hydrogen lines Hβ, Hγ, Hδ, Hε and the Helium lines HeI 5016Å HeI 5047Å, as well as variations in the atmospheric oxygen lines. This can be interpreted that their variations are non-radial pulsations and strong stellar wind.

High-frequency variations of spectral lines in cromospherically active stars 61 cyg AB

2015 ◽  
Vol 31 (6) ◽  
pp. 267-275 ◽  
Author(s):  
B. E. Zhilyaev ◽  
A. V. Bondar ◽  
M. V. Andreev ◽  
S. M. Pokhvala ◽  
Yu. M. Ivashchenko ◽  
...  
Keyword(s):  
High Frequency ◽  
Spectral Lines ◽  
Active Stars ◽  
Frequency Variations

Dynamic Stability of a Water Brake Dynamometer

1998 ◽  
Vol 120 (1) ◽  
pp. 89-96 ◽  
Author(s):  
R. A. Van den Braembussche ◽  
H. Malys
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Lumped Parameter Model ◽  
Stable Operation ◽  
Pressure Oscillations ◽  
Lumped Parameter ◽  
Flow Oscillations ◽  
Brake Dynamometer ◽  
Low Torque ◽  
Frequency Variations

A lumped parameter model to predict the high frequency pressure oscillations observed in a water brake dynamometer is presented. It explains how the measured low frequency variations of the torque are a consequence of the variation in amplitude of the high frequency flow oscillations. Based on this model, geometrical modifications were defined, aiming to suppress the oscillations while maintaining mechanical integrity of the device. An experimental verification demonstrated the validity of the model and showed a very stable operation of the modified dynamometer even at very low torque.

scholarly journals High frequency variations of the Earth's orbital parameters and climate change

2002 ◽  
Vol 29 (18) ◽  
pp. 40-1-40-4 ◽  
Author(s):  
C. Bertrand ◽  
M. F. Loutre ◽  
A. Berger
Keyword(s):  
Climate Change ◽  
High Frequency ◽  
Orbital Parameters ◽  
Frequency Variations

scholarly journals Frequency variations of gravity waves interacting with a time-varying tide

2013 ◽  
Vol 31 (10) ◽  
pp. 1731-1743 ◽  
Author(s):  
C. M. Huang ◽  
S. D. Zhang ◽  
F. Yi ◽  
K. M. Huang ◽  
Y. H. Zhang ◽  
...  
Keyword(s):  
Gravity Waves ◽  
High Frequency ◽  
Lower Atmosphere ◽  
Horizontal Wind ◽  
Frequency Variation ◽  
Time Varying ◽  
Transient Nature ◽  
Critical Layers ◽  
Favorable Conditions ◽  
Frequency Variations

Abstract. Using a nonlinear, 2-D time-dependent numerical model, we simulate the propagation of gravity waves (GWs) in a time-varying tide. Our simulations show that when a GW packet propagates in a time-varying tidal-wind environment, not only its intrinsic frequency but also its ground-based frequency would change significantly. The tidal horizontal-wind acceleration dominates the GW frequency variation. Positive (negative) accelerations induce frequency increases (decreases) with time. More interestingly, tidal-wind acceleration near the critical layers always causes the GW frequency to increase, which may partially explain the observations that high-frequency GW components are more dominant in the middle and upper atmosphere than in the lower atmosphere. The combination of the increased ground-based frequency of propagating GWs in a time-varying tidal-wind field and the transient nature of the critical layer induced by a time-varying tidal zonal wind creates favorable conditions for GWs to penetrate their originally expected critical layers. Consequently, GWs have an impact on the background atmosphere at much higher altitudes than expected, which indicates that the dynamical effects of tidal–GW interactions are more complicated than usually taken into account by GW parameterizations in global models.

scholarly journals High Frequency Variations of Earth Rotation Parameters from GPS and GLONASS Observations

Sensors ◽  
2015 ◽  
Vol 15 (2) ◽  
pp. 2944-2963 ◽  
Author(s):  
Erhu Wei ◽  
Shuanggen Jin ◽  
Lihua Wan ◽  
Wenjie Liu ◽  
Yali Yang ◽  
...  
Keyword(s):  
Earth Rotation ◽  
High Frequency ◽  
Earth Rotation Parameters ◽  
Rotation Parameters ◽  
Frequency Variations

scholarly journals The Three-Dimensional Locating of VHF Broadband Lightning Interferometers

Atmosphere ◽  
2018 ◽  
Vol 9 (8) ◽  
pp. 317 ◽  
Author(s):  
Hengyi Liu ◽  
Shi Qiu ◽  
Wansheng Dong
Keyword(s):  
Time Resolution ◽  
High Frequency ◽  
Three Dimensional ◽  
High Time Resolution ◽  
Very High Frequency ◽  
Time Difference Of Arrival ◽  
Lightning Discharges ◽  
Total Lightning ◽  
Locating Information ◽  
Very High

VHF (Very High Frequency) lightning interferometers can locate and observe lightning discharges with a high time resolution. Especially the appearance of continuous interferometers makes the 2-D location of interferometers further improve in time resolution and completeness. However, there is uncertainty in the conclusion obtained by simply analyzing the 2-D locating information. Without the support of other 3-D total lightning locating networks, the 2-station interferometer becomes an option to obtain 3-D information. This paper introduces a 3-D lightning location method of a 2-station broadband interferometer, which uses the theodolite wind measurement method for reference, and gives the simulation results of the location accuracy. Finally, using the multi-baseline continuous 2-D locating method and the 3-D locating method, the locating results of one intra-cloud flash and the statistical results of the initiation heights of 61 cloud-to-ground flashes and 80 intra-cloud flashes are given. The results show that the two-station interferometer has high observation accuracy on both sides of the connection between the two sites. The locating accuracy will deteriorate as the distance between the radiation source and the two stations increases or the height decreases. The actual locating results are similar to those of the existing VHF TDOA (Time Difference of Arrival) lightning locating network.

scholarly journals The Radial Velocity Curve of V652 Her (BD+13°3224)

1985 ◽  
Vol 87 ◽  
pp. 109-115
Author(s):  
P.W. Hill ◽  
C.S. Jeffery
Keyword(s):  
Radial Velocity ◽  
Time Resolution ◽  
High Frequency ◽  
Velocity Curve ◽  
Velocity Data ◽  
Effective Surface ◽  
Radial Velocity Curve ◽  
Minimum Radius ◽  
Helium Star ◽  
Radial Velocity Data

AbstractNew radial velocity data for the pulsating extreme helium star V652 Her (BD+13°3224) have been obtained with a time resolution of 100 s. High frequency structure in the radial velocity curve is detected, and a comparison with previous data suggests that the detailed shape of the velocity curve is variable. The data imply that the effective surface gravity must increase by a factor of 4 at minimum radius.

scholarly journals Callus induction and regeneration of Alkanna orientalis var. Orientalis and A. sieheana

2019 ◽  
Vol 48 (3) ◽  
pp. 633-640 ◽  
Author(s):  
Cenney Yaman ◽  
Serkan Uranbey ◽  
Hussein Abdullah Ahmed ◽  
Sabahattin Özcan ◽  
Osman Tugay ◽  
...  
Keyword(s):  
Shoot Regeneration ◽  
Callus Induction ◽  
High Frequency ◽  
Stem Segment ◽  
Leaf Base ◽  
Cotyledonary Leaf ◽  
Frequency Variations ◽  
Alkanna Orientalis ◽  
Stem Segments

Callus induction and proliferation of Alkanna orientalis var. orientalis and Alkanna sieheana containing valuable alkannin/shikonin (A/S) derivates were investigated using leaf base and stem segment explants. Stem segments and cotyledonary leaf base of both species were cultured on Murashige and Skoog medium fortified with different concentrations of BAP, Kn, NAA, IAA and IBA for callus induction and shoot regeneration. High frequency reproducible, prolific and compact calli formation was obtained from the stem segments of both species in all media tested. The frequency variations of callus induction and shoot regeneration were discussed in terms of different species, plant growth regulators and explant resources. A. orientalis and A. sieheana may be considered to be alternative plants for the A/S production in vitro.

Latitudinal insolation gradients throughout the Holocene II – High frequency variations

2020 ◽  
Vol 66 (8) ◽  
pp. 1992-2000
Author(s):  
Rodolfo G. Cionco ◽  
Willie W.-H. Soon ◽  
Ana G. Elias ◽  
Nancy E. Quaranta
Keyword(s):  
High Frequency ◽  
The Holocene ◽  
Frequency Variations
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