Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 28 for “"Disk Model"”.
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Radial-zoned thermal accretion disk model around black holes
… energy astrophysics, the theory of accretion disks around black holes. Accretion disk models are applied to the dynamics of compact objects surrounded by material with organized angular momentum. The disk forms due to the process by which differentially rotating fluid layers interact with each …
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Zooming in on quasar accretion disks using chromatic microlensing
Observing the temperature profiles of accretion disks around black holes is a fundamental test of an important astrophysical process. However, angular resolution limitations have prevented such a measurement for distant quasars. We present a new method for determining the size of quasar accretion …
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Applications of axial and radial compressor dynamic system modeling
… are related by the underlying dynamic system modeling approach that is common in all of them. Two types of models are introduced, suitable for modeling the dynamic behavior of axial and centrifugal compression systems: a compact single semi-actuator disk model, Model I, and a new modular multi …
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Hyperbolic transformations on cubics in H²
… within this work are based on the Poincaré disk model of H², where H² is understood to mean the hyperbolic plane. The thesis explores the properties of both the untransformed cubic (the original locus of centroids) and the transformed cubic (the original cubic taken under a linear fractional …
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Hyperbolic transformations on cubics in H²
… within this work are based on the Poincaré disk model of H², where H² is understood to mean the hyperbolic plane. The thesis explores the properties of both the untransformed cubic (the original locus of centroids) and the transformed cubic (the original cubic taken under a linear fractional …
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Magnetically torqued thin accretion disks
We consider geometrically thin accretion disks around millisecond X-ray pulsars. We start with the Shakura-Sunyaev thin disk model as a basis and modify the disk equations with a magnetic torque from the central neutron star. Disk solutions are computed for a range of neutron star magnetic fields. …
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Circumstellar Structure Properties of Young Stellar Objects: Envelopes, Bipolar Outflows, and Disks
… envelopes, bipolar outflows, and circumstellar disks, have been studied using radio interferometers: the Berkeley-Illinois-Maryland Association (BIMA) array and the Combined Array for Research in Millimeter-wave Astronomy (CARMA). (1) Envelopes: Three Class 0 YSOs (L1448 IRS 2, L1448 IRS 3, and …
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Stochastic Optimization and Optimal Control for Complex Networked Infrastructures
… control strategies, nonlinear nature of physical models and unpredictable netloads (e.g., renewable energy and water demands). These tendencies promise to deliver unprecedented flexibility and smart features in these systems, but require more sophisticated modelling and operation schemes. In …
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Spectroscopic and spectro-astrometric analysis of T Tauri Stars
… the composition of the protoplanetary disk from which the solar system formed. To infer this, we study analogs to the early solar system called T Tauri stars. These objects are low-mass, pre-main sequence stars surrounded by circumstellar disks of material from which planets are …
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Astrophysical maser radiation from Keplerian disks near active galactic nuclei
… maser radiation emerging from gaseous disks at the nuclei of active galaxies. In at least one galaxy (NGC 4258), such maser radiation is observed and arises from a disk around a presumed massive black hole. The heating, cooling, and excitation mechanisms necessary for creating the …
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Relativistic Radiative Hydrodynamics Calculation of Accretion Flow into Supermassive Black Hole
… flow simulation. We are able to use the models to constrain observational parameters of Sgr A*. We also compute the synchrotron emissivity and absorptivity from first principles, in order to verify improved approximate equations for the RT calculation. The code can handle a wide range of …
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The Influence of a Skewed Disk on a Flexible Rotating Shaft
… to verify the existing theory of skewed disk forced response predictions. The experimental tests were conducted on a horizontal flexible shaft rotor system supported in two hydrodynamic journal bearings. The computer simulations were conducted with a program that uses a matrix transfer …
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Probing for optical and HI diffuse gas in MHONGOOSE galaxy UGCA 250
… velocity lag with respect to the galactic disk. Similarly, there is a wealth of observational evidence for extraplanar gas in the form of neutral atomic hydrogen (HI) associated with spiral galaxies. The presence of extraplanar hydrogen emission around nearby galaxies is believed to be a …
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A Unified Framework for Characterization of Mode and Spike Routes to Rotating Stall
… rotor using a low order, non-linear actuator disk model. The actuator disk representation is capable of capturing stall inception behavior given an axisymmetric total-to-static pressure rise characteristic. A parametric study of the effect of the derivative of the total-to-static pressure rise …
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Dust in circumstellar disks
… distribution of dust particles in circumstellar disks. Using millimetre interferometric observations of optically thick disks around T Tauri stars, I provide conclusive evidence for the presence of millimetre- to centimetre-sized dust aggregates. These findings demonstrate that dust grain growth …
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Time-dependent Accretion Flows onto Black Holes
… hole X-ray binaries (BHXB). The standard thin disk model fails to reproduce the spectra of these systems. They exhibit a blackbody-like component, generally attributed to the cold standard disk, and a hard power law-like component extending to several 100 keV, which cannot be accounted for by …
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Numerical Simulations of Oil Spills and Wind Turbine Flows for Applications in Offshore Environmental Sustainability
… A number of high-fidelity numerical simulation models are developed and applied to tackle these challenging problems, including the large-eddy simulation model for the oceanic and atmospheric turbulent flows, the Eulerian large-eddy simulation model for particle plume dispersion in ocean …
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Planetary Systems in Polarized Light: Debris Disk Observations and Instrumentation
… observations can be useful for imaging debris disks and characterizing exoplanet atmospheres. With that in mind, this thesis has been constructed with two main aspects: i) observational studies of two debris disk systems, Beta Pic and HD 157587, using the Gemini Planet Imager and ii) the …
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Electrochemical models for electrode behavior in retinal prostheses
The focus of this thesis is the modeling, characterization, and improvement of microfabricated electrodes for the Retinal Implant Project. The ultimate goal of the Project is to build a retinal prosthesis able to restore a limited degree of visual function in people suffering from certain types of …
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Star formation and disk stability in nearby galaxies
… of apparent cutoffs in star formation in the disks of galaxies as well as apparent thresholds in empirical laws of star formation have led many workers in the field to seek out the drivers and regulators of star formation in galaxies. Although the intricate details of these drivers are yet to …
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