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Articles 1 - 10 of 10
Full-Text Articles in Physical Sciences and Mathematics
Developing A Uhf/Vhf Phased-Array Satellite Ground Station, Brent K. Cole
Developing A Uhf/Vhf Phased-Array Satellite Ground Station, Brent K. Cole
Theses and Dissertations
Earth-satellite communications and tracking of spacecraft are accomplished using ground stations. Traditionally, this has been achieved by using a large parabolic antenna or pair of antennas that point at a source of interest and mechanically steer the antenna(s) as the source moves throughout the sky. Phased arrays, which have often been used in radio astronomy, can provide multiple benefits when used as a ground station including fast scanning speeds across the sky, tracking and communication of multiple sources simultaneously, and significant improvements to overall gain, signal-to-noise ratio (SNR), and data bandwidth. This thesis presents a preliminary analysis of a 20-element …
Methods For Multi-Source Resolution In Pulsar Timing Array Based Gravitational Wave Detection, Yiqian Qian
Methods For Multi-Source Resolution In Pulsar Timing Array Based Gravitational Wave Detection, Yiqian Qian
Theses and Dissertations
With next-generation radio telescopes, namely the Five-hundred-meter Aperture Spherical Telescope(FAST) and Square Kilometer Array(SKA), scheduled to come online during this decade, hundreds of well-timed millisecond pulsars (MSPs) will be added to the Pulsar Timing Arrays (PTAs) being used currently for Gravitational Wave (GW) searches. This will greatly increase the distances to which GW sources in the very low frequency band can be detected. Among these sources will be super massive black hole binaries (SMBHBs) formed out of gigantic black holes weighing in at million to billion times the mass of our Sun. Although the large number of MSPs will improve …
Searching For Low Frequency Fast Radio Bursts With Vlite, Suryarao Bethapudi
Searching For Low Frequency Fast Radio Bursts With Vlite, Suryarao Bethapudi
Theses and Dissertations
The VLITE (VLA Low Band Ionosphere and Transient Experiment; http://vlite.nrao.edu) program performs commensal observations using 16 antennas of the Very Large Array radio telescope from 320-384 MHz. The VLITE-Fast program searches for short time-scale (<100ms) transients, such as Fast Radio Bursts (FRBs), in real time and triggers recording of baseband voltages for offline imaging. Searches are made possible by a 12 node cluster, each housing GPUs for digital signal processing. A real-time Message Passing Interface (MPI)-based co-adder incoherently sums the data streams from all the antennas to boost the signal-to-noise. To undo the dispersion effects of signal propagation through the ionized interstellar medium, the co-added stream is de-dispersed and matched-filtered to search for transients. This operation is completely performed on GPUs by the software package Heimdall . A selection logic is applied to the candidates and interesting candidates with their corresponding data are processed and packaged in a binary file along with a diagnostic plot. Furthermore, a Machine Learning classification is applied on the reduced data product and, based on its decision, baseband voltages are recorded. Reduced data products collected over 126 days of on-sky operation form the VLITE-Fast Pathfinder Survey (VFPS). This pipeline has triggered on single pulses from 7 known radio pulsars. Lastly, the pipeline capabilities are tested against pure random noise and simulated injected signals.
Searching For Pulsars Using The Long Wavelength Array Telescope, Keeisi A. Caballero Valdez
Searching For Pulsars Using The Long Wavelength Array Telescope, Keeisi A. Caballero Valdez
Theses and Dissertations
Radio pulsars are fascinating celestial objects known to display both periodic and transient behavior. Pulsars are characterized by narrow electromagnetic radiation beams which restrict the number of pulsars visible from Earth due to the necessary alignment of the radiation beam across an observer’s line of sight. Pulsars are useful tools for a broad range of applications and provide important information about the process of stellar evolution, tests for relativistic theories of gravity and the search for low-frequency gravitational waves. Over 2,500 pulsars have been observed since their initial discovery in 1967 but the search for these objects is continuously warranted. …
Topography Estimation Using Particle Swarm Optimization, Yelbir Kazhykarim
Topography Estimation Using Particle Swarm Optimization, Yelbir Kazhykarim
Theses and Dissertations
The Earth’s Vertical Gravity Gradient (VGG) can be used to map seafloor topography but presents a challenging inverse problem. A promising approach is forward modeling, in which one searches over a set of candidate topographies and selects the one whose predicted VGG best fits the observed one. The main bottleneck here is solving the associated high-dimensional and non-linear optimization problem. Yang et al (2018) demonstrated a method in which the topography is parametrized by heights of mass elements on a rectangular grid and the ≈ 104 dimensional optimization problem is tackled with simulated annealing (SA). We propose a computationally much …
Exploring Mechanical Properties And Configurational Energetics Of Toxbox Using Molecular Dynamics Simulation, Shams Mehdi
Exploring Mechanical Properties And Configurational Energetics Of Toxbox Using Molecular Dynamics Simulation, Shams Mehdi
Theses and Dissertations
All-atom Molecular Dynamics Simulations (MDS) have been performed to obtain 5 ns trajectory of the solvated, neutralized, and equilibrated toxbox system in NPT ensemble at 300 K. This trajectory data has been used to calculate the configurational entropy of toxbox by employing a quantum mechanical approach. The method is based on evaluating determinant of the covariance matrix, built from generalized coordinates of all atoms for each frame. The upper limit to the configurational entropy of toxbox has been calculated to be 30,030 J/mol-K. A preliminary investigation has been conducted to study the effects of sequence-dependent DNA conformation (DNA Crookedness) on …
Magnesium Diboride Embedded Multi-Walled Carbon Nanotube Yarns, Ujjal Lamichhane
Magnesium Diboride Embedded Multi-Walled Carbon Nanotube Yarns, Ujjal Lamichhane
Theses and Dissertations
The discovery of superconductivity in a simple hexagonal binary compound of MgB2 at a relatively high critical temperature ~39 K renewed the interest in the field of superconductivity. Twisted laminar superconducting composite structures based on coiled multi-walled carbon nanotube (MWCNT) yarns were crafted by integrating magnesium and boron homogeneous mixture into the carbon nanotube sheets. After the ignition of the Mg/B/MWCNT system, under the controlled argon environment and uniform heating rate, the high exothermic reaction between magnesium (Mg) and boron (B) with stoichiometric ratio produced the MgB2/MWCNT superconducting composite yarns. The XRD analysis confirmed that the heated sample consists of …
Effects Of Incubation Temperature On Nanomechanical Properties Of Β-Lactoglobulin Amyloid Fibers, Santosh Khatri
Effects Of Incubation Temperature On Nanomechanical Properties Of Β-Lactoglobulin Amyloid Fibers, Santosh Khatri
Theses and Dissertations
Amyloid fibrils constitute a class of highly ordered nanomaterials formed by aggregates of the protein. Although The irreversible fibril formation of various proteins is related to the disorders like Alzheimer’s diseases, Creutzfeldt-Jacob and many more, amyloid fibrils have also been noticed in many physiologically beneficial roles such as in adhesive and hormone storage. Here, we compare the stiffness and structural properties of the amyloid fibers examined by the statistical approaches of single molecule atomic force microscopy images of heat-denatured β-lactoglobulin fibrils at different incubation time period (24, 48, and 72 hours). We demonstrate the gradual decrease in stiffness of the …
Multi Wall Carbon Nanotube (Mwcnt) Laminar Composite Structures Reinforced With Titanium Carbide (Tic), Rakibul Alam Shohan
Multi Wall Carbon Nanotube (Mwcnt) Laminar Composite Structures Reinforced With Titanium Carbide (Tic), Rakibul Alam Shohan
Theses and Dissertations
Laminated composites have been widely used in weight critical structures, such as aircraft, spacecraft, bullet-proof vests, radiation protection suits, spacesuits etc., owing to their high stiffness, strength, and thermal stability. Multi Wall Carbon Nanotube (MWCNT) laminar composite have attracted a good attention for these laminar composites due to its outstanding physical and mechanical properties as well as extraordinary electrical, optical, and thermal properties. Laminar composite structures based on twisted MWCNT yarn were crafted by integrating titanium and graphene mixture at (80:20) wt. %, respectively into multi wall carbon nanotube sheets. Titanium and Graphene mixture addition has been used to improve …
Searching For Optical Counterparts To Gravitational Waves, Richard Camuccio
Searching For Optical Counterparts To Gravitational Waves, Richard Camuccio
Theses and Dissertations
The era of multi-messenger astronomy has begun. The coordinated activities of multiple, distinct observatories play a critical role in both responding to astrophysical transients and building a more comprehensive interpretation otherwise inaccessible to individual observations. The Transient Robotic Observatory of the South (TOROS) Collaboration has a global network of instruments capable of responding to several transient targets of opportunity. The purpose of this thesis is to demonstrate how optical observatories with small fields of view (degree) can follow up and observe astrophysical transients. TOROS facilities responded to three unique gravitational wave events during the second and third observational campaigns of …