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Articles 1 - 13 of 13
Full-Text Articles in Physical Sciences and Mathematics
A Study Of The Lhires Iii Spectrograph On The Hard Labor Creek Observatory 20 Inch Telescope, Benjamin G. Jenkins
A Study Of The Lhires Iii Spectrograph On The Hard Labor Creek Observatory 20 Inch Telescope, Benjamin G. Jenkins
Physics and Astronomy Theses
I present a study done to determine the characteristics of the LHIRES III spectrograph on the 20 inch RC Optics telescope at Hard Labor Creek Observatory. I describe the settings of three different diffraction gratings, collimation and focus issues, and practical aspects of use. The spectrograph was used with a SBIG ST-8XME camera for all studies. Data collection was accomplished with the Maxim DL software package and analysis was completed with IRAF. Solutions for the dispersion relation with all three diffraction gratings were found. Several projects are underway with this instrument. I present time series spectra of α Vir to …
Factors That Impact International Students? Learning Of Introductory Physics At Georgia State University, Eric Kweku Appiah
Factors That Impact International Students? Learning Of Introductory Physics At Georgia State University, Eric Kweku Appiah
Physics and Astronomy Theses
This study uses a combination of quantitative and qualitative enquiry to focus on determining the most salient factors that affect international students’ learning of introductory physics in Georgia State University. For purposes of the study, “international students” were defined as those who attended high school in a country other than the US. These students comprise a significant portion of the physics courses at Georgia State, and this study was motivated by the desire to support their success. The study involved a collaboration with the newly emerging Physics and Astronomy Education Research Group who has recently begun the routine collection of …
Microvariability Of The Blazar 3c279, Hannah M. Clemmons
Microvariability Of The Blazar 3c279, Hannah M. Clemmons
Physics and Astronomy Theses
Active Galactic Nuclei (AGN) are some of the most extreme objects in the universe. They output copious amounts of energy spanning the entire electromagnetic spectrum. There are many different subclasses of AGN depending on your viewing angle. Blazars, viewing down the relativistic jet, are the most variable class of AGN known. They exhibit extreme variability in all wavelengths on timescales as short as minutes. In this thesis I will consider the extreme faintness of 3C279 with respect to the long-term light curve as well as recent observations of microvariability. I am able to confirm small amplitude events using simultaneous observations …
Optical Properties Of In1-Xgaxn Epilayers Grown By Hpcvd, Jielei Wang Ms
Optical Properties Of In1-Xgaxn Epilayers Grown By Hpcvd, Jielei Wang Ms
Physics and Astronomy Theses
Optical absorption spectroscopy has been applied to study properties such as the fundamental absorption edge and defect absorption centers of group III-nitride compound semiconductor epilayers. The investigation in this thesis focused on analyzing the band gap of indium-rich In1-xGaxN epilayers, which where grown by the high-pressure chemical vapor deposition (HPCVD) technique. Our results - together with literature data for gallium-rich In1-xGaxN alloys indicate that the shift of the fundamental band gap of In1-xGaxN with composition x can be described with a bowing parameter of b = 2.2eV. Temperature dependent transmission measurements show that the band gap variation with temperature follows …
Assessing The Effectiveness Of Studio Physics At Georgia State University, Brianna M. Upton
Assessing The Effectiveness Of Studio Physics At Georgia State University, Brianna M. Upton
Physics and Astronomy Theses
Previous studies have shown that many students have misconceptions about basic concepts in physics which persist after instruction. It has been concluded that one of the challenges lies in the teaching methodology. To address this, Georgia State University (GSU) has begun teaching studio algebra-based physics. Although many institutions have implemented studio physics, most have done so in calculus-based sequences. Additionally, the unique environment of GSU’s population as a diverse, urban research institution is considered. The effectiveness of the studio approach for this demographic in an algebra-based introductory physics course was assessed. This five-semester pilot study presents demographic survey results and …
Measuring The Effective Wavelength Of Chara Classic, Emily Collins Bowsher
Measuring The Effective Wavelength Of Chara Classic, Emily Collins Bowsher
Physics and Astronomy Theses
This thesis presents an engineering project measuring the effective wavelength of the CHARA Classic beam combiner on the CHARA Array. Knowing the actual effective wavelength of light observed is very important because that value is necessary for determining astrophysical parameters of stars. Currently, the value used for CHARA Classic data comes from a model of the system and is based on numbers published by the manufacturer of the filter; it is not derived from measurements done on the system directly. We use two data collection methods to observe standard stars of different spectral types and calculate the wavelength of light …
Analysis Of Gan/Alxga1?Xn Heterojunction Dual-Band Photodetectors Using Capacitance Profiling Techniques, Laura E. Byrum
Analysis Of Gan/Alxga1?Xn Heterojunction Dual-Band Photodetectors Using Capacitance Profiling Techniques, Laura E. Byrum
Physics and Astronomy Theses
Capacitance-voltage-frequency measurements on n+-GaN/AlxGa1−xN UV/IR dual-band detectors are reported. The presence of shallow Si-donor, deep Si-donor, and C-donor/N-vacancy defect states were found to significantly alter the electrical characteristics of the detectors. The barrier Al fraction was found to change the position of the interface defect states relative to the Fermi level. The sample with Al fraction of 0.1 shows a distinct capacitance-step and hysteresis, which is attributed to C-donor/N-vacancy electron trap states located above the Fermi level (200 meV) at the heterointerface; whereas, the sample with Al fraction of 0.026 shows negative capacitance and dispersion, indicating C-donor/N-vacancy and deep Si-donor …
Duty Cycle Maintenance In An Artificial Neuron, William Halbert Barnett
Duty Cycle Maintenance In An Artificial Neuron, William Halbert Barnett
Physics and Astronomy Theses
Neuroprosthetics is at the intersection of neuroscience, biomedical engineering, and physics. A biocompatible neuroprosthesis contains artificial neurons exhibiting biophysically plausible dynamics. Hybrid systems analysis could be used to prototype such artificial neurons. Biohybrid systems are composed of artificial and living neurons coupled via real-time computing and dynamic clamp. Model neurons must be thoroughly tested before coupled with a living cell. We use bifurcation theory to identify hazardous regimes of activity that may compromise biocompatibility and to identify control strategies for regimes of activity desirable for functional behavior. We construct real-time artificial neurons for the analysis of hybrid systems and demonstrate …
Short-Wave Infrared Diffuse Reflectance Of Textile Materials, Terence Haran
Short-Wave Infrared Diffuse Reflectance Of Textile Materials, Terence Haran
Physics and Astronomy Theses
This thesis analyzes the reflectance behavior of textiles in the short-wave infrared (SWIR) band (1 – 2 microns) in order to identify/design potential diagnostic tools that allow the remote detection of human presence in a scene. Analyzing the spectral response of fabrics in the SWIR band has gained significant interest in the remote sensing community since it provides a potential path to discriminate camouflaged clothing from backgrounds that appear similar to the object of interest in the visible band. Existing research, originating primarily from the textiles community, has thoroughly documented the behavior of clothing fabrics in the visible band. Other …
Slowmo: A Search For Nearby Stars, Misty Adana Brown
Slowmo: A Search For Nearby Stars, Misty Adana Brown
Physics and Astronomy Theses
I report on suspected nearby stars with proper motions 1.0 arcsec > μ ≥ 0.5 arcsec/yr in the southern sky (DEC = −90° to 00°). This sample of slow-motion (SLOWMO) stars complements the work of Jao (2004), who reported on faster moving stars with μ ≥ 1.0 arcsec/yr in the entire sky for his doctoral dissertation, and the work of Finch (2007), who uncovered stars moving slower than 0.5 arcsec/yr between declinations −90° and −47°. Characterizations of SLOWMO systems include trigonometric parallaxes, optical and infrared photometry. For stars without trigonometric parallaxes, colors and apparent magnitudes are used to calculate photometric distance …
A Mechanism Of Co-Existence Of Bursting And Silent Regimes Of Activities Of A Neuron, Tatiana Igorevna Malashchenko
A Mechanism Of Co-Existence Of Bursting And Silent Regimes Of Activities Of A Neuron, Tatiana Igorevna Malashchenko
Physics and Astronomy Theses
The co-existence of bursting activity and silence is a common property of various neuronal models. We describe a novel mechanism explaining the co-existence of and the transition between these two regimes. It is based on the specific homoclinic and Andronov-Hopf bifurcations of the hyper- and depolarized steady states that determine the co-existence domain in the parameter space of the leech heart interneuron models: canonical and simplified. We found that a sub-critical Andronov-Hopf bifurcation of the hyperpolarized steady state gives rise to small amplitude sub-threshold oscillations terminating through the secondary homoclinic bifurcation. Near the corresponding boundary the system can exhibit long …
Minimo: A Search For Mini Proper Motion Stars In The Southern Sky, Charlie Thomas Finch
Minimo: A Search For Mini Proper Motion Stars In The Southern Sky, Charlie Thomas Finch
Physics and Astronomy Theses
I report 1684 new proper motion systems in the southern sky (declinations -90 degrees to -47 degrees) with 0.50 arcsec/yr > mu >= 0.18 arcsec/yr. This effort is a continuation of the SuperCOSMOS-RECONS (SCR) proper motion search to lower proper motions than reported in Hambly et al. (2004); Henry et al. (2004); Subasavage et al. (2005a,b). Distance estimates are presented for the new systems, assuming that all stars are on the main sequence. I find that 34 systems are within 25 pc, including three systems --- SCR 0838-5855, SCR 1826-6542, and SCR 0630-7643AB --- anticipated to be within 10 pc. These …
New Correlation Effects In Nonrelativistic Atomic Photoionization In The High Energy Limit, Chieh Jen Yang
New Correlation Effects In Nonrelativistic Atomic Photoionization In The High Energy Limit, Chieh Jen Yang
Physics and Astronomy Theses
The effect of initial state correlation on high-energy dipole photoionization is considered and it is shown that for almost all atomic electron the asymptotic high-energy dependence is E-7/2, and the dominant transition is an ionization plus excitation satellite transition. This is demonstrated in numerical calculations of the photoionization of Ge4p2 1S and Sn 5p2 1S.