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Optimizing performance in elastic optical networks using advanced reconfigurable optical add-drop multiplexers: A novel design approach and comprehensive analysis
No full textNetwork operators diversify service offerings and enhance network efficiency by leveraging bandwidth-variable transceivers and colorless flexible-grid reconfigurable optical add-drop multiplexers (ROADMs). Nonetheless, the paradigm shift from rigid to elastic optical networks (EONs) has affected several key parameters, including bit rate, center frequency spacing, modulation format, and optical reach. This study investigated the transformative impact of emerging technologies on the design and structure of optical network architectures, including spectrally efficient multicarrier systems and bandwidth-variable wavelength-selective switches. A cost-effective ROADM architecture applying an order-based connecting approach was introduced, which presented a high connectivity level and a blockage probability of less than 10-4. When this architecture was implemented in the EON, the data transportation rate was 1 Tb/s. This outcome successfully accommodated a 20 % surge in traffic demand, while the optimized network architecture significantly improved fiber utilization by 3.4 %. Consequently, this study contributed a practical and efficient solution for implementing flexible optical networks, effectively addressing current concerns and propelling the optical communication system sector forward.Electrical and Computer Engineerin
Design, Synthesis, and Reactivity of New Square-Planar Metal Imido Complexes
Get PDFNitrogen-containing compounds play a crucial role in various fields of chemistry, including medicinal chemistry and materials science. Traditional methods for synthesizing these compounds, such as reductive amination, often lack efficiency in atom economy and require specific functional groups. In contrast, catalytic approaches, particularly C-H amination, provide a more efficient way to form nitrogen-carbon bonds without the need for pre-defined functionality. C-H amination relies on the generation of metallo-nitrene or imido complexes, which have been isolated in limited cases, with certain examples demonstrating the ability to facilitate amination. The approach to studying metal imido complexes in this dissertation makes use of supporting ligands termed pincers. Pincer ligands are advantageous due to their straightforward synthesis, ease of isolation, and tunability, enabling the study of reactive species and catalytic mechanisms.
Chapter 2 discusses the synthesis of a rare square-planar iron nitrene complex and exploration of its reactivity relevant to C-H amination. Through a reaction of [Fe(N2)(tBuPNP)] with various organic azides, an isolated nitrene containing a mesityl substituent was synthesized. Additionally, a reaction leading to formation of a tetrazido complex was also accomplished by exploring the reactivity of the sterically smaller phenyl azide. Chapter 3 examines novel cobalt imido and amido complexes and their reactivity pertaining to C-H amination. These new imido complexes were easily attained by utilizing [Co(N2)(tBuPNP)]. Although hydrogen atom transfer activity was observed, C-H amination was unsuccessful. A detailed studied of the electronic structure of these imido complexes was pursued in a collaborative fashion, leading to demonstration of a unique ferromagnetically coupled ground state featuring Co(II) and an imidyl radical. Lastly, Chapter 4 explores two different potential nickel compounds and their reactivity in nitrene formation. A RPNPNi(I) bridging mercury dimer (R = tBu or Cy) is first explored by examining its reactivity in the presence of organic azides. The second set of compounds that are examined are [Ni(H)(RPNP)] (R = tBu or Cy) complexes. Although square-planar nickel imido complexes were unattainable, reactivity indicative of nitrene formation was observed including a ?triple nitrene? insertion adduct that was shown to inhibit further reactivity. While these compounds were reactive in the presence of organic azides, HAT was not observedChemistr
Single-Projection Laser Absorption Tomography for Hexagonally-Symmetric Reacting Flows
No full textThis thesis presents a coupled computational and experimental investigation into the thermochemistry of non-uniform reacting flows characterized by non-circular geometries. The primary focus is on applying a single-projection tomographic reconstruction technique developed for hexagonal geometries in a laser absorption spectroscopy context, without the need for multiple different projection angles to obtain spatially-resolved absorptivity and species mole fraction of carbon dioxide. The industry-relevant context of the work is first discussed, followed by a discussion of the tomographic reconstruction technique, which is first tested in time averaged simulated reacting flow fields using advanced species transportation modeling in ANSYS to produce radially-resolved absorptivity profiles, analogous to those produced by laser absorption tomography performed on a time-averaged flow field. The reacting flow simulations comprised a central methane/oxygen jet flame surrounded by cold carbon dioxide. A generalized Abel transform was employed to reconstruct the tomographic image of the species’ concentration distribution from line-of-sight absorbance measurements. The laser scan path was included in the simulation to allow for an accurate comparison of results to those of the corresponding experiment in this study, which comprised a series of methane / oxygen jet flames surrounded by a hexagonal carbon dioxide co-flow, with absorbance measured through laser spectroscopy techniques. A detailed description of the physical reactor hardware design is then provided, detailing the experimental setup which aimed to reproduce the simulation study. The raw experimental data was processed to remove noise and align measurements with background signals, followed by the application of the Beer-Lambert law to calculate path-integrated absorbance. Wavenumber scaling was performed using etalon data to ensure precise spectral alignment. The aforementioned single projection reconstruction technique for hexagonal geometries is then employed on the experimental data to determine spatially-resolved absorptivity of carbon dioxide. The results demonstrate the correlation between experimental data and simulation outputs, validation of the reconstruction technique through the CFD models, and the implementation of this technique with the experimental data. This work contributes to the field of combustion diagnostics by providing a comprehensive methodology for combining experimental and computational approaches to analyze the absorption of a species as well as determine species concentration over a unique reacting flow geometry, without the need for multiple angles of optical access in industrially-relevant hexagonal reactors.Mechanical Engineerin
Experiences in Delivering Online CS Teacher Professional Development
No full textThis work was later presented as a poster at UTSA's Graduate Student Appreciation Week (GSAW) Research Symposium on April 2, 2024. The poster is available at https://hdl.handle.net/20.500.12588/6390.This paper describes our team's experience in designing and delivering the online teacher professional development (PD) program, Computer Science for San Antonio (CS4SA), aimed at empowering educators with computer science (CS) knowledge to increase Latinx participation in CS and STEM education within a large, urban predominantly Latinx school district in South Texas. This paper highlights the successes, challenges, and lessons learned while facilitating two cohorts of the CS PD through online platforms during the COVID-19 pandemic. As a result of this program, participants recognized the importance of integrating CS into their classroom and becoming advocates for the discipline at the high school level. Additionally, teachers, investigators, and other personnel learned important lessons for enhancing the program's impact through collaboration with district administrators and refinement of the online learning experience.This material is based upon work supported by the National Science
Foundation under Grant No. 1923269.Computer ScienceMathematicsElectrical and Computer EngineeringIntegrative BiologyInterdisciplinary Learning and Teachin
Production, Flavor Transformation and Predicting Final States of Entangled Neutrinos
Get PDFAs the nuclear energy in a star is depleted, the internal pressure from the centrally directed gravitational force causes the star to collapse inward until outward nuclear pressure restores equilibrium. The star's layers begin to fold inward, and the outward pressure continues to build. This causes the outer layers of the star to expand outward, and in some cases sending the star into supernova. During the collapse of the star, protons and electrons make up the star's magnetosphere. As the pressure continues to build, the protons and electrons are compressed to form proton-proton chains. These chains, including a decay from a short-lived electron, produce neutrinos. This neutrino production is sped up relatively quickly due to the magnetosphere of the star itself. As a neutrino travels from creation to detection, it can oscillate and change flavors, or types. The primary focus of this dissertation is to provide theoretical foundation for the emittance and detection of neutrinos from supernovae with comparisons to solar neutrinos and the higher-energy cosmic rays. This is done by calculating an approximate cross section for higher energy sources such as cosmic rays. Our first goal with this research is to determine an emission rate for neutrinos due to particle accelerations within the magnetosphere of a collapsing star. Using this rate, we are then able to examine a theoretical mean free path which would allow a ``complete'' flavor transition from electron to tau and to determine what, if any, affect the Fermi acceleration may have on overall neutrino oscillations and flux. We look at Bell's theorem of quantum non-locality and use it to determine the probability of neutrino entanglement in an effort to predict neutrino states for further research into possible higher-order flavor transitions. Finally, we are able to use our predictions comprising fraction density charts in an effort to compare predicted flavor values with those recently detected.Physics and Astronom
Characterization of Excited-State Electronic Structure in Diblock π-Conjugated Oligomers with Adjustable Linker Electronic Coupling
Get PDFDiblock conjugated oligomers are &pi;-conjugated molecules that contain two segments having distinct frontier orbital energies and HOMO-LUMO gap offsets. These oligomers are of fundamental interest to understand how the distinct &pi;-conjugated segments interact and modify their excited state properties. The current paper reports a study of two series of diblock oligomers that contain oligothiophene (T<sub>n</sub>) and 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole (TBT) segments that are coupled by either ethynyl (-C&equiv;C-) or <i>trans</i>-(-C&equiv;C-)<sub>2</sub>Pt(II)(PBu<sub>3</sub>)<sub>2</sub> acetylide linkers. In these structures, the T<sub>n</sub> segment is electron rich (donor), and the TBT is electron poor (acceptor). The diblock oligomers are characterized by steady-state and time-resolved spectroscopy, including UV-visible absorption, fluorescence, fluorescence lifetimes, and ultrafast transient absorption spectroscopy. Studies are compared in several solvents of different polarity and with different excitation wavelengths. The results reveal that the (-C&equiv;C-) linked oligomers feature a delocalized excited state that takes on a charge transfer (CT) character in more polar media. In the (-C&equiv;C-)<sub>2</sub>Pt(II)(PBu<sub>3</sub>)<sub>2</sub>-linked oligomers, there is weak coupling between the T<sub>n</sub> and TBT segments. Consequently, short wavelength excitation selectively excites the T<sub>n</sub> segment, which then undergoes ultrafast energy transfer (~1 ps) to afford a TBT-localized excited state.Chemistr
ZRG: A Dataset for Multimodal 3D Residential Rooftop Understanding
No full textRooftop Understanding:
[Figure]
The anatomy of a residential roof is complex. The understanding of rooftop geometry and structure has important real world applications including:
● Roof Damage Inspection & Detection
● Residential Solar Rooftop Potential
● 3D Modeling and Digital Twins Cities
Dataset Acquisition:
[Figure]
● Data acquired from over 20k residential roof inspections from across the United States using DJI drones
● Diverse: includes single and multi family homes (e.g. apartment complexes) from rural and urban locations
● Overhead and oblique imagery acquired for analyzing inspecting rooftops as well as performing multiview reconstruction to estimate rooftop structure and heightElectrical and Computer Engineerin
The Enduring Legacy of Texas Freedom Colonies on Black Homeownership: A Mixed-Methods Approach
Get PDFThis research project examines the historical roots of Black homeownership and its contemporary implications. Historically, systemic discrimination has impeded Black wealth accumulation, perpetuating racial disparities in homeownership rates. The unique Texan landscape, characterized by urban and rural areas, reinforces the significance of understanding Black homeownership within this state, particularly in reference to Texas Freedom Colonies. While the populations of most communities have faded over time, their legacy persists, influencing property ownership patterns in nearby cities. This project employs a combination of quantitative and qualitative methods to provide a comprehensive understanding of Black homeownership in historical context.
Using a mixed-methods approach, which combined statistical analyses of census data with narratives of lived experiences, enabled an inclusive understanding of Freedom Colonies' impact on homeownership among the Black population. This research contributes to the existing literature on wealth disparities. The inclusion of personal narratives enriched the study, providing insights beyond what data alone could offer. The collective findings highlight both the empowering aspects of collective self-determination within the Black community, including the protective effects of intentional independence, as well as the adverse effects of segregation. By contextualizing these findings historically, the research offers valuable insights for policymakers, informing recommendations aimed at addressing racial disparities in homeownership and wealth, and gives meaningful direction to future research.Applied Demograph
Tyche: An Efficient and General Prefetcher for Indirect Memory Accesses
No full textIndirect memory accesses (IMAs, i.e., A[f(B[i])]) are typical memory access patterns in applications such as graph analysis, machine learning, and database. IMAs are composed of producer-consumer pairs, where the consumers’ memory addresses are derived from the producers’ memory data. Due to the built-in value-dependent feature, IMAs exhibit poor locality, making prefetching ineffective. Hindered by the challenges of recording the potentially complex graphs of instruction dependencies among IMA producers and consumers, current state-of-the-art hardware prefetchers either (a) exhibit inadequate IMA identification abilities or (b) rely on the run-ahead mechanism to prefetch IMAs intermittently and insufficiently.
To solve this problem, we propose Tyche,1 an efficient and general hardware prefetcher to enhance IMA performance. Tyche adopts a bilateral propagation mechanism to precisely excavate the instruction dependencies in simple chains with moderate length (rather than complex graphs). Based on the exact instruction dependencies, Tyche can accurately identify various IMA patterns, including nonlinear ones, and generate accurate prefetching requests continuously. Evaluated on broad benchmarks, Tyche achieves an average performance speedup of 16.2% over the state-of-the-art spatial prefetcher Berti. More importantly, Tyche outperforms the state-of-the-art IMA prefetchers IMP, Gretch, and Vector Runahead, by 15.9%, 12.8%, and 10.7%, respectively, with a lower storage overhead of only 0.57 KB.Computer Scienc
Guarding the Senses: Unveiling Cybersecurity Solutions through the Exploration of Image and Sound Sensor Design Limitations
No full textThe proliferation of Internet of Things (IoT) devices in modern society has seen an increasing dependence on sensors, particularly cameras and microphones, to enhance functionality and user experience. However, this advancement is not without its pitfalls. This dissertation explores the potential security vulnerabilities that these sensors introduce. Previous work has shown that by targeting microphone sensors, they can subvert voice-controllable systems. Similarly, by manipulating camera sensors, attackers can compromise the safety of autonomous vehicles. Through rigorous research, we have discovered novel attacks tailored to these sensors: a remote and inaudible assault on microphones and a subtle, unnoticeable compromise of cameras. Recognizing the implications of these vulnerabilities, we have also designed and proposed effective defenses against these sophisticated attacks, aiming to bolster the security of IoT devices in our interconnected world. Our research can be divided into three parts: (i) Inaudible attack against voice-controllable system (VCS) via compromising microphone. This part includes three of our works: one published work named Near-Ultrasound Inaudible Trojan (Nuit): Exploiting Your Speaker to Attack Your Microphone, and one submitted work Surface Obstacles as Speakers (SOS): Waging Inaudible Attacks against Voice Control Systems Behind Surface Obstacles; (ii) Invisible attack against Autonomous driving AI model via compromising camera. In this part includes our submitted work Moiré Injection Attack (MIA): Compromising Autonomous Vehicle Safety via Exploiting Camera's Color Filter Array (CFA) to Inject Hidden Traffic Sign. (iii) In this part we also include Alpha Channel Attack (ACA), Ignoring is Attacking: The Universal Targeted No-box Attack on Computer Vision Models through Alpha Channel Oversight.Electrical and Computer Engineerin