SHAREOK Repository
Not a member yet
49261 research outputs found
Sort by
Fast Adaptive Digital Beamforming With Machine Learning
Get PDFDigital polarimetric Phased Array Radar (PAR) has the potential to achieve high temporal and spatial resolution needed for next-generation weather observations. It offers flexibility in scanning strategies, including the use of electronic steering, coupled with traditional "pencil" beams, spoiled beams, and/or multiple beams. Digital beamforming (DBF) is one of the unique capabilities of PAR used to simultaneously form multiple beams digitally, a critical capability needed to improve temporal resolution. DBF can be done with non-adaptive or adaptive methods. The Fourier method pre-computes the beamforming weights based on the configuration of the antenna elements, which results in fixed sidelobe levels and angular resolution. In contrast, the Capon method computes the beamforming weights adaptively from receive signals. The Capon method can provide enhanced angular resolution over the Fourier method by lowering antenna sidelobe levels in directions with strong contaminating returns. However, it is challenging to implement the Capon method in real-time as the number of antenna elements grows due to the high computational cost.
This work proposes a computationally efficient Deep Learning Adaptive digital beam Forming (DLAF) method using a neural network trained with time-series IQ signals as input and the Capon beamforming weights as output. The network is built with a combination of convolution, activation, normalization, and dense layers. The novelty of the proposed network is that it implements an AI-based adaptive beamforming method preserving signal phase information, which improves the efficiency and accuracy of the learning. The proposed DLAF model is evaluated using a simulated point target, an actual point target, and simulated weather signals for a planar digital array architecture. Specifically the performance of DLAF is evaluated and compared to both the Capon and Fourier methods. Two qualitative metrics used for the evaluation are the quality of the generated beam pattern, such as the half-power beamwidth, artifacts from sidelobes, and the capability of placing nulls at locations with strong interference signals. Four quantitative metrics used for the evaluation are computation time, the performance of DLAF as a function of SNR, mean squared error of beamforming weight values, and normalized cross-correlation of generated beam patterns. Preliminary results show that DLAF was trained successfully to perform adaptive DBF and mimic the behavior of the Capon method for point and distributed targets. Furthermore, DLAF can significantly reduce the computational time which allows real-time implementation of adaptive DBF
Sex education, sex communication, and long-term sexual health outcomes: a longitudinal moderation analysis
Get PDFBackground: Unintended pregnancy and STIs are recognized by national organizations as a critical public health concern. A strategy to decrease risk of unintended pregnancy and STIs includes consistent use of condoms. School-based sex education is intended to inform and provide sexual risk reduction strategies targeted at young populations. Parents can also be a critical influence on adolescent risky sexual behaviors. This dissertation project explored longitudinal associations between school-based sex education and young adult unintended pregnancy, STI risk, and condom use behaviors. Additionally, this dissertation explored the moderating influence of parent-adolescent sex communication.
Methods: Measures of school-based pregnancy and HIV sex education reported by a nationally representative sample of adolescents were extracted from the National Longitudinal Study of Adolescent and Add Health’s (Add Health) Wave I In-Home survey. Waves II-V In-Home surveys provided outcome variables: the intention of first reported pregnancy, diagnosis of an STI, and condom use at recent sex. Two logistic regressions were employed using Stata 17 to explore longitudinal associations. Parent-adolescent sex communication variables from the Parent Interview were added to the models to explore the moderating effects between school-based sex education and young adulthood sexual health outcomes and behaviors.
Results: Study I: Of the 2,324 participants (53.6% female; 64.9% non-Hispanic White) that had school-based sex education, 46% reported their first pregnancy as intended, while 36.1% were unintended. Longitudinal results indicated that school-based sex education was not associated with long-term unintended pregnancy. Furthermore, parent-adolescent sex communication did not have a significant moderating influence on school-based sex education and unintended pregnancy. Study II: Of the 2,761 participants (47.3% female; 69.4% non-Hispanic White) that had school-based sex education, 15.3% were diagnosed with an STI between late adolescence to young adulthood. Longitudinal results indicated that school-based sex education was not associated with long-term STI risk. Parent-adolescent sex communication significantly interacted with participant biological sex, race, and parent educational attainment. Study III: Of the 1,899 participants (47.9% female; 69.4% non-Hispanic White) that had school-based sex education, 84.8% did not use a condom the last time they engaged in sexual intercourse. Longitudinal results indicated that school-based sex education was not associated with condom use at recent sex. Parent-adolescent sex communication significantly interacted with participant biological sex, race, and urbanicity.
Conclusion: School-based sex education may not influence long-term sexual risk behaviors. However, parent-adolescent sex communication can provide a foundation for positive sexual behaviors to be carried into young adulthood. Interventions focused on reducing adolescent sexual risk behavior should include parent participation. Parent-adolescent sex communication can be targeted in interventions to improve long term risk of unintended pregnancy, STI, and condom use.
Keywords: Unintended pregnancy, STI, condom use, school-based sex education, parent-adolescent sex communicatio
Exploring collaboration and its influence on artistic creativity through an investigation of literature, personal interviews, and the creation of a non-hierarchical collaborative process in dance, music, and painting
Get PDFThis thesis explores collaboration and its influence on artistic creativity through an investigation of literature, personal interviews, and an autoethnographic case study of a non-hierarchical collaboration that began in August 2021 and culminated with a fully staged performance piece in January 2022. The purpose of the case study was to investigate how the collaborative process informed and inspired the creativity of each participating artist toward the goal of developing a fully staged presentation. The non-hierarchical component was defined as collaboration whereby each artist contributed, reacted, and participated without dictating concept or design. The primary team of collaborators consisted of a choreographer, a composer, and a visual artist. Each had been classically trained in their respective fields and were inherently interested in collaboration. Documentation of the collaborative process is presented through a chronological narrative from inspiration, concept design, and various experiments that led to a presentation of music, dance, and visual art. The final result was a ballet in eight movements that traveled between a reality space and a memory space and was supported by eight original music scores and six original projected paintings.
This thesis offers insight into the collaborative process and its influence on each collaborator, participating dancers, projection artist, and lighting designer. It discusses the characteristics and elements that are integral for successful collaboration and sheds light on the creative potential and possibilities that collaboration can provide in the educational and professional studio setting.
Analysis of the case study and of the information gleaned from interviews as well as the review of literature support the premise that collaboration influences creative output. This thesis is intended to strengthen the reader’s understanding of successful collaborative creativity while aiming to inspire and enhance future research
Metal-ligand covalency in uranium, thorium, and cerium coordination chemistry: elucidating the nature of chemical bonding in f-element complexes using phosphorus ligands
Get PDFHerein the syntheses and characterization of model actinide and lanthanide complexes bearing phosphorus-based ligands are reported. High-symmetry molecular models featuring phosphorus-based ligands are very advantageous for experimental metal-ligand covalency studies because phosphorus-31 nuclear magnetic resonance spectroscopy and phosphorus-Kβ X-ray emission spectrometry can be used to study the electronic structure and orbital interactions of metal-phosphorus bonds. Furthermore, high-symmetry models simplify spectral interpretation, and reduce the complexity of computational studies of the actinides. The quantum chemistry of the actinides is very complex because relativistic effects and spin-orbit coupling are very important influences on the electronic structures of these elements. Low-symmetry and high coordination numbers are very common in actinide coordination chemistry, which further complicates actinide computational chemistry. The creation of molecular models with high-symmetry and low coordination numbers greatly reduces the complexity of empirical electronic structure studies. Using a combination of advanced spectroscopy and advanced computational methods, details about the metal-ligand orbital interactions in actinide and lanthanide complexes can be obtained. Herein reactions of advanced f-element amide complexes with phosphorus-based compounds are reported, with the intention of creating high-symmetry, low-coordinate f-metal complexes for empirical electronic structure investigations
Hailstone Trajectory and Surface Hailfall Analysis in the 29-30 May 2012 Kingfisher, OK Supercell
Get PDFDuring the Deep Convective Clouds and Chemistry Experiment (DC3), a wealth of data was collected on a hail-producing tornadic supercell near Kingfisher, OK on 29-30 May 2012. Three mobile radars collected radial velocity, reflectivity, and polarimetric data over a ~70- minute period during the storm’s mature phase. Additionally, far-environmental and in-storm soundings were taken following the storm's track while hail samples were collected in the town of Kingfisher, OK by the Insurance Institute for Business and Home Safety (IBHS). The 4-D storm fields of airflow and reflectivity from multi-Doppler radar analyses are combined with 4-D Diabatic Lagrangian Analysis (DLA) retrievals of temperature and water substance and WRF- HAILCAST physics to compute densely spaced Lagrangian hail growth trajectories for the present study. Hail embryos are initialized in the hail growth module every three minutes of the radar analysis period (2251-0000 UTC) to produce over 2.7 million hail trajectories. Using a new, unique dataset we validate previous hail growth trajectory theories and introduce new hypotheses.
Hailstone positions within the storm and at the surface are analyzed for hailstones of varying sizes. It is found that severe hailstones spend a majority of their growth phase within the downshear stagnation zone where horizontal winds are have minimal impact on the hailstones. Simulated severe hail is favored over non-severe hail by significantly longer residence times in 30-50 m/s updrafts and supercooled cloud water contents exceeding 5 g/kg. As the storm strengthens, a new trajectory pathway from embryos sourced within the backsheard anvil emerges, which leads to an increase in overall hail production. Simulated hail swaths provide spatial and temporal understanding of hail diameters and concentrations at the surface. The largest hail falls to surface preferentially along the southern (storm-inflow) flank of the hail swath, though size-sorting effects differ along the hail swath.
In an effort to improve the hail growth physics, sensitivity tests are conducted on the heat transfer coefficient while hailstones are allowed to be oblate, the ice collection efficiency, and the shedding threshold. The ice collection efficiency showed no sensitives while the shedding threshold showed the greatest sensitivity for the smallest hailstones. Oblate hailstones with increased heat transfer showed the greatest sensitivity. Spherical and oblate hailstones are compared to observations and we conclude the oblate hailstones are more physically representative of what was observed and would occur in nature
Between a Rock and a Hard Place: The Challenges of Building Coptic Spaces in Contemporary Egypt
Get PDFThe Coptic community of Egypt operates daily under pressures from state, society, and the Coptic Orthodox Church, and yet are expected to be an invisible minority that places its national identity over its ethnoreligious one that it is often ostracized for. This thesis explores how Copts navigate the concept of space in Egypt, and more importantly, how, through a process of cooptation, creative subversion of, or opposition to the systems they operate under, build space for themselves outside of what they had been restricted to. This thesis explores ideas of visibility, panopticism, and hegemony as I discuss the historical and sociological intricacies of Copts in Egypt engaging in quiet practices and loud actions
Astro-nots Bezos, Branson, and Musk Compared to NASA and the ESA: Using Twitter to Assess Public Sentiment Differences Between Commercial and Government Space Programs
Get PDFIn recent years, the endeavors of commercial entities in space travel have increased dramatically outside of government contracts. What was traditionally a granted contract system with NASA, has now become the “New Age Space Race” or “Billionaire Space Race”. This has subverted previously held norms of how private entities participate in space exploration. Billionaires, i.e. Jeff Bezos, Richard Branson, and Elon Musk, have, and are, increasingly funding their own private programs and missions in space. As the polarization between traditional government space exploration and private entities’ engagement in space increases, there is a notable difference in public perceptions towards these two groups. My thesis uses an international scope to examine how sentiments expressed towards commercial entities engaged in space exploration differ in comparison to American and European space programs. Further, this study expands Jones and McBeth’s Narrative Policy Framework (NPF) by using text and sentiment analysis of Twitter data to build space policy narratives. In turn, these can be used to assess how policy outcomes influence policy narratives and public opinion. Finally, a discussion of future directions in space policy research and understanding narratives towards commercial and government space programs is presented.
KEYWORDS: space policy, Narrative Policy Framework, text analysis, sentiment analysis, Twitter, Elon Musk, NASA, Blue Origin, SpaceX, public opinio
Small molecule design strategies for probing structure-activity relationships: bacterial virulence modulation via CpxRA, the total synthesis of Picrasma alkaloids, and coronavirus main protease inhibitors
Get PDFThe overall aim of this work is to contribute to molecular design strategies for early lead development while probing structure-activity relationships via the design and synthesis of small molecules. This dissertation will tell three distinct stories: (1) exploitation of CpxRA as a target for virulence modulation in Gram-negative bacteria, (2) work towards the total synthesis of Picrasidine natural product family members, and (3) the rational design and synthesis of SARS-CoV-2 main protease inhibitors