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Showing 1 to 20 of 68 for “"pulsations"”.
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Modeling and Control of Gas Turbine Thermoacoustic Pulsations
Diese Arbeit befasst sich mit der Analyse thermoakustischer Instabilitäten in Gasturbinen-Brennkammern. Passive Methoden wurden entwickelt, um die durch die Instabilitäten entstehenden Druckschwankungen zu unterdrücken. Zunächst wurden unter der Annahme kleiner Mach-Zahlen die thermoakustischen …
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Heartbeat Stars and the Ringing of Tidal Pulsations
… software is the ability to model tidally induced pulsations simultaneously with the binary star features, enabling a complete and accurate heartbeat star model to be determined. Tidally induced pulsations are stellar oscillations driven by the tidal force of the companion star. Approximately 20% …
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Damping acoustic pressure pulsations in pipelines using Helmholtz resonators
… turbomachinery generate acoustic pressure pulsations, which propagate into the pipeline and interact with piping components, potentially causing vibrations, increased fretting wear, and even fatigue failure. In this thesis, an acoustic damping device known as the Helmholtz resonator (HR) is …
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A theoretical study of stellart pulsations in young brown dwarfs
… on the recently proposed phenomenon of ‘stellar pulsations’ in young brown dwarfs by the seminal study of Palla and Baraffe (2005) (PB05, thereafter). The PB05 study presents results of a non-adiabatic linear stability analysis showing that young brown dwarfs should become pulsationally unstable …
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Pulsations in the white dwarf primary of a cataclysmic variable star
The field of Asteroseismology provides powerful techniques for the study of pulsating white dwarf stars. If these techniques could be applied to the white dwarf primaries of Cataclysmic Variable stars, the study of accretion in interacting binary systems would benefit enormously. Our understanding …
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Studies of non-adiabatic pulsations in the atmospheres of the roAp stars
The roAp stars are high overtone pulsators characterised by strong global magnetic fields with effective field strength of between a few hundred to a few thousand Gauss. They also show overabundances in rare-earths and iron peak element. Multi-colour photometry of roAp stars shows that their …
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Noise due to pressure pulsations in a pressure-balanced sliding vane pump
… pump noise was related to the pump's pressure pulsations. The pulsations consisted of three types of pressure oscillations: the pressure ripple with a fundamental component at the vane passage frequency together with harmonics; the low-frequency pressure oscillation with a fundamental component …
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Passive damping mechanism of Herschel-Quincke tubes for pressure pulsations in piping systems
The acoustic pressure pulsations in industrial piping systems can induce fluctuating loads on inline equipment which may cause fatigue failure and in severe cases, initiate a phenomenon known as acoustic resonance. Passive damping devices such as the Herschel-Quincke (HQ) Tube can be implemented …
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The Effect of Tidal Interactions On Hot Subdwarf B Stars and Their Pulsations
… Asteroseismological analysis of the observed pulsations shows that they do not quite fit with the theoretical models, especially in the close binary systems. We present a method for computing tidal distortion and associated frequency shifts. Validation is by application to polytropes and …
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Ionospheric Disturbances: Midlatitude Pi2 Magnetospheric ULF Pulsations and Medium Scale Traveling Ionospheric Disturbances
… magnetospheric Pi2 ultra low frequency (ULF) pulsations in the vicinity of the plasmapause. Prior to these pulsations, two Earthward moving fast plasma flows were detected by spacecraft in the magnetotail. Signatures of inner magnetospheric compression observed by the Blackstone radar provide …
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Heat transfer from in-line and perpendicular arrangements of cylinders in steady and pulsating crossflow
… to determine the effect of organized flow pulsations on mean heat transfer from a single cylinder, in-line arrangements and perpendicular arrangements of cylinders. Pulsation frequencies of up to twice the natural vortex shedding frequency and zero to peak. amplitudes as high as 36 percent …
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On the Characteristics of Fires in Tunnels
… the outcome. During two of the fire tests, large pulsations of the gas flow inside the tunnel were observed. These pulsations were registered only when the measured heat release rate was higher than 125 MW - 135 MW. Two different periods of pulsations were registered, short periods of …
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Pulsating aurora: Source region & morphology
… the frequencies of equatorial electron flux pulsations and pulsating aurora luminosity fluctuations at the ionospheric footprint. We use simultaneous satellite-based data from GOES 13 and ground-based data from the THEMIS allsky imager array to show that there is a direct correlation between …
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Nonlinear behaviour of pulsating white dwarfs
… investigated the nonlinear properties of the pulsations of two white dwarfs, namely DA G29-38 and DB GD358. The data at my disposal comprised numerous single- and multi-sites time series photometric campaigns, including light curves from four Whole Earth Telescope runs conducted respectively …
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Investigation of velocity gradient as driving force of flow pulsation in fuel assemblies
The presence of quasi-periodic flow pulsations in fuel assemblies has been observed since the 1960's but is still not fully understood. Current design and licensing practices for nuclear reactor fuel mostly rely on 1-dimensional subchannel simulation tools, which might not accurately predict the …
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Effect of Local Bed Hydrodynamics on the Distribution of Liquid in a Fluidized Bed
… were investigated. The effects of spray pulsations and atomization gas flowrate on liquid distribution were also studied. Effects of bed hydrodynamics on the initial liquid distribution and on the subsequent drying were studied separately. The results indicate that jet pulsations or …
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Time-Domain Astrophysics with the Transiting Exoplanet Survey Satellite
… insights that these "tidally tilted" pulsations enable. In particular, we focus on developing models to track the amplitude and phase of these pulsations as a function of orbital phase, as well as tools to perform physically-motivated modeling of the binary components. Chapters 6-7 …
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Atmospheric temperature structure in the RoAp stars
… to F0 V-IV. About 20 years ago rapid non-radial pulsations were discovered in the coolest members of the CP2 group, namely the roAp stars. These pulsations are due to high over-tone, low degree p modes with periods between 5.6 and 15 minutes. Since then, studies of these rapid oscillations have …
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Development of ground-based search -coil magnetometer systems in the polar regions and studies of ULF Pc 1--2 wave propagation in the ionospheric waveguide
… developed for the observations of geomagnetic pulsations in the ultra low frequency (ULF) range (a few mHz to a few Hz). The design, fabrication, and test/calibration have been performed to detect very weak geomagnetic pulsations with approximately a few pT resolution over the frequency range 0 …
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