Open Access. Powered by Scholars. Published by Universities.®
- Institution
- Keyword
-
- Gravitational waves (2)
- AdS (1)
- Artificial Intelligence (1)
- Astronomy (1)
- Black hole (1)
-
- Black holes (1)
- Cadmium (1)
- Convolution Neural Network (1)
- Cosmology (1)
- Cross section (1)
- Einstein field equations (1)
- Einstein's equations (1)
- General Relativity (1)
- General relativity (1)
- Gravitational lensing (1)
- Neutron star (1)
- Neutron stars (1)
- Non-destructive assay techniques (1)
- Pulsar (1)
- Q-value (1)
- Radio (1)
- Static coordinates (1)
- Telescopes (1)
- Thermodynamics (1)
- Web application (1)
Articles 1 - 8 of 8
Full-Text Articles in Entire DC Network
Direct Measurement Of The 114cd(N, Gamma)115cd Cross Section In The 1 Ev To 300 Kev Energy Range, Kofi Tutu Addo Assumin-Gyimah
Direct Measurement Of The 114cd(N, Gamma)115cd Cross Section In The 1 Ev To 300 Kev Energy Range, Kofi Tutu Addo Assumin-Gyimah
Theses and Dissertations
The large thermal cross section of cadmium makes it ideal for many practical applications where screening of thermal neutrons is desired. For example, in non-destructive assay techniques, or for astrophysical studies of the s-process. All such applications require precise knowledge of the neutron-capture cross section on cadmium. Although there are some data on neutron-capture cross sections particularly at thermal energies and at energies relevant for astrophysics, there is very little data at most other energies. Further, the evaluated cross sections from the ENDF and JENDL databases disagree at high energies. Therefore, there is a critical need for precise knowledge of …
Radio Pulsar Searching And Timing Follow-Up, Alexander Eli Mcewen
Radio Pulsar Searching And Timing Follow-Up, Alexander Eli Mcewen
Theses and Dissertations
Pulsars provide some of the richest laboratories for studying the behavior of ultra-dense matter. As such, they have been utilized for decades to place stringent limits on gravitation and as probes of the material that fills our Galaxy. These tests benefit greatly from a catalog of pulsars that is as complete as possible, which in turn requires thorough searches of the Galaxy and precise timing of discoveries. These searches are informed by the continued characterization of the pulsar population, and so searching techniques develop in tandem with the analysis of their discoveries. Large scale pulsar surveys find pulsars; small scale …
Optimizing Convolutional Neural Networks For Transient Detection In Optical Astronomy With Augmented Datasets, Wendy Mendoza
Optimizing Convolutional Neural Networks For Transient Detection In Optical Astronomy With Augmented Datasets, Wendy Mendoza
Theses and Dissertations
We present a technique for optical transient detection using artificial neural networks, particularly a Convolutional Neural Network (CNN), a deep learning algorithm. This method analyzes images of the same area of the sky captured by several telescopes, with one image serving as a reference for a probable transient’s epoch and the other as an image from a previous epoch. We train the CNN on simulated sources and test it on actual image data samples using data from the Dr. Cristina V. Torres Memorial Astronomical Observatory and Sloan Digital Sky Survey. This autonomous detection method replaces the standard procedure, which involves …
Dyonic Taub-Nut-Ads Space Phase Structure, Mohamed Tharwat
Dyonic Taub-Nut-Ads Space Phase Structure, Mohamed Tharwat
Theses and Dissertations
The Taub-NUT spacetime remains to hold many mysteries more than half a century after its discovery. The metric's controversy owes largely to the nut charge and the existence of Misner strings. Traditionally the metric is treated in the euclidean signature, this treatment hides the Misner strings. We treat the Taub-NUT spacetime with the Misner strings visible, not enforcing the time periodicity condition. We examine the phase structure belonging to three different horizon geometries. We deal with the hyperbolic, flat and spherical cases. We consider the stable phases, the phase transitions that exist between them, and find the preferable phases in …
Numerical Simulations Of Tidal Disruption Events, Alexandra Elise Spaulding
Numerical Simulations Of Tidal Disruption Events, Alexandra Elise Spaulding
Theses and Dissertations
The detection of supermassive black holes (SMBH) in our universe has proven to be a challenge. One way to find an SMBH in a quiescent, inactive galaxy is through a tidal disruption event, or a TDE. A TDE occurs when a star is slightly perturbed and is subsequently disrupted by the SMBH. When this happens, part of the debris from the disrupted star remains bound to the SMBH while the rest is unbound. The SMBH accretes the bound matter and reveals their presence by a temporary X-ray flare, lasting a few months. Using conservation of energy, the fallback rate of …
Cosmology, Lensing, And Modified Gravity With Gravitational Waves, Ignacio Magana Hernandez
Cosmology, Lensing, And Modified Gravity With Gravitational Waves, Ignacio Magana Hernandez
Theses and Dissertations
Since the first detection of gravitational waves (GWs) from the merger of two stellar-mass black holes in 2015, the LIGO-Virgo-KAGRA (LVK) Collaboration has accumulated over 90 observations of mergers involving neutron stars and black holes. With the upcoming observing runs for the LVK network of GW detectors, many more binary mergers are expected to be detected. The increasing size of gravitational wave catalogs has enabled the study of their population, its cosmic expansion history, signatures of gravitational wave lensing, and how well these observations agree with general relativity. In this dissertation, I will discuss my contributions to gravitational wave cosmology. …
Evaluation Of Black Holes In An Evolving Universe, John P. Naan
Evaluation Of Black Holes In An Evolving Universe, John P. Naan
Theses and Dissertations
There are various solutions to the Einstein field equations that represent different physical assumptions, but how to represent multiple black holes within an expanding universe remains an area of open interest. The first step to resolving this question involves evaluating spacetime models that contain a single black hole in an expanding universe. Here, we are primarily interested in understanding the energy distribution of black hole models by solving Einstein's equations using the associated spacetime metric and comparing the propagation of waves within the model against other known spacetime models. Specifically, we will evaluate the combined Schwarschild-de Sitter solution under a …
A Comparison Of Automated Bolide Detection Methods, Maxine Thembi Khumalo
A Comparison Of Automated Bolide Detection Methods, Maxine Thembi Khumalo
Theses and Dissertations
Bolide recording and analysis are crucial so meteoroid fragments can be found, a lightcurve analyzed, and its trajectory calculated. The Spalding Allsky Camera Network (SACN) generates videos and composite images of the night sky that are potential meteors based on changes in brightness. The best way to ensure quick identification is to automate the detection of bolides (and all meteors) using computational techniques. This project tested three algorithms to sort events between those with and without meteors - a Traditional Hough Detection Method, Convolutional Neural Network (CNN), and YOLOv5 against the previous technique from 2018 by Elena Botella. All the …