Theses
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Publication INVESTIGATION OF CYCLOTRON RADIATION FROM GRAPHENE-BASED DEVICES(Monterey, CA; Naval Postgraduate School, 2023-09) Planillo, Jordan; Alves, Fabio Durante Pereira; Physics (PH)Current solutions to address the terahertz gap—the range of frequencies from 0.3 THz to 3.0 THz in the electromagnetic spectrum—fall into two broad categories: microwave solutions and photonic solutions. The most promising solutions—high electron mobility transistors and quantum cascade lasers—while capable of producing the desired THz frequencies, are limited from widespread use due to cost and operating environment requirements. Graphene’s remarkable material properties have been extensively explored for applications as a replacement forsilicon in integrated circuits to novel biological sensors. Of particular interest is graphene’s exceptionally high carrier mobility and saturation velocity. These properties make it an excellent candidate for a solid state implementation of a cyclotron radiation source. With the appropriate design, a cyclotron style device that emits THz radiation is possible. This work details the modeling, design, simulation, fabrication, and characterization of graphene-based cyclotrons. Simulated finite element graphene arcs indicate that emissions of 1 THz or greater requires an arc radius of 67 nm or less. Fabricated micron scale model on commercial graphene wafers have demonstrated cyclotron radiation emissions at microwave frequencies (3 GHz–4 GHz), which is independent of the applied stimulus frequencies of 1.73 GHz and 10.16 GHz. Fabrication of nanoscale arc arrays exceeding 1 million per square millimeter was also demonstrated.Publication THEORY AND DESIGN OF MEDIUM VOLTAGE PULSED CURRENT SUPPLIES USING WIDE BANDGAP SOLID STATE DEVICES(Monterey, CA; Naval Postgraduate School, 2015-12) Martino, Christopher A.; Julian, Alexander; Electrical and Computer Engineering (ECE)Applications such as superconductor testing, fuse testing, pulsed lasers, and electromagnetic railguns require high-voltage, pulsed-current, power supplies that are energy efficient, compact, and reliable. This dissertation utilizes experimental analysis of scaled circuits and simulation to investigate solid state devices that enable more efficient, scaled-down, and controllable current pulse circuits. It is true that discrete solid state devices exist that are capable of withstanding large voltages, conducting large currents, and switching rapidly. This dissertation improves these devices with a unique wide bandgap vertical superjunction drift region edge termination enabling low resistance, high off voltage, and more energy efficient semiconductor devices. To improve the magnitude control and rise/fall time of the current pulse, an original positive buck boost current pulse–forming circuit control method is also demonstrated that meets the unique demands of a linearly rising output voltage and a quadratically falling input voltage.Publication A SYSTEMS APPROACH TO MODELING RESISTANCE ORGANIZATIONS AND GUERRILLA FORCE CARRYING CAPACITY(Monterey, CA; Naval Postgraduate School, 2024-06) Wallace, Sean M.; McCormick, Gordon H.; Defense Analysis (DA); Porter, WayneMilitary defeat or occupation are not necessarily the end to a conflict. Resistance movements can prevail long after military defeat and may offer states facing a superior foe a strategic path to regain national sovereignty. This research aims to quantify a population's capacity for armed resistance (resistance potential) to inform planning for employment and support of special operations forces (SOF). Using system dynamics modeling, this research simulates resistance based on the Resistance Operating Concept (ROC) framework and the Cyprus Emergency case study. It leverages ecological concepts of epidemiology’s susceptible-infected-recovered (SIR) model and Lotka-Volterra predator-prey relationships to model interactions between guerrilla forces and the supporting resistance population. The model successfully identifies a resistance population's carrying capacity, influenced by public sentiment and recruitment rate. It further suggests a resistance can sustain guerrilla forces of up to 5% of its total size by optimizing a resistance’s organizational structure. These findings offer insights for SOF employment. A resistance’s carrying capacity can guide the number and type of SOF advisors allocated to a region. The model also suggests that optimizing resistance structure and timing is more critical than building large-scale public sentiment. Misallocation of SOF resources exceeding the system's carrying capacity can hinder long-term resistance growth.Publication FROM WORDS TO ACTIONS: LEADERS' INTENTIONAL DEIA ENGAGEMENTS AND THEIR IMPACT ON UPSTANDERS, MENTAL HEALTH, PERFORMANCE, AND RETENTION/RECRUITMENT(Monterey, CA; Naval Postgraduate School, 2024-06) Johnson, Danica R.; Helzer, Erik; Department of Defense Management (DDM); Cunha, JesseThe U.S. Navy has articulated a commitment to diversity, equity, inclusion, and accessibility (DEIA) to support a just and equitable culture. This research serves to examine the overarching question: Do leaders’ intentional engagements with DEIA promote “upstanders” (i.e., individuals who take action against injustices) and contribute to an inclusive environment resulting in improved mental health, increased performance, and retention/recruitment? To examine this further, I subdivided it into several specific questions and conducted a literature review concentrating on researchers who have collected data and insights into DEIA and cultural change among other relevant topics. The results of this literature review highlight the centrality of leaders for driving inclusivity and transforming organizations. By empowering upstanders, leaders contribute to the cultivation of an environment where people feel valued and compelled to actively participate. Individuals who perceive themselves as valued are inclined to exhibit enhanced performance and express a desire to remain with the organization, thus contributing to a form of internal marketing. Drawing upon existing literature to provide context, the DEIA Navigator was developed as a guide offering clear guidance to Navy leaders. It details strategies aimed at enhancing DEIA within the Navy’s organizational culture.Publication INITIAL CONCEPTUAL DESIGN OF A SURFACE COMBAT SHIP IN SUPPORT OF THE NATIONAL CONTINUOUS SHIPBUILDING PLAN OF THE CHILEAN NAVY(Monterey, CA; Naval Postgraduate School, 2024-06) Jofre Parra, Leonardo Ulises Sr.; Stevens, Mark; Systems Engineering (SE); Van Bossuyt, Douglas L.The Chilean Navy lacks a conceptual design for a future surface combat ship with the capabilities to fulfill its mission and promote the National Continuous Shipbuilding Plan. This thesis proposes an initial conceptual design with a focus on combat systems to serve as a starting point for developing this shipbuilding plan. A systems engineering approach is employed, supported by scenario methodology, modeling and simulation, and the design of experiments to optimize anti-missile defense capabilities. Finally, an initial system architecture is presented with the chosen combat systems and their location on a Type 26 frigate, the platform chosen as the basis of the design. According to the proposed crisis/war scenario, the results indicate that the optimal combination to meet the survival measure of effectiveness defined for the ships in the task group is to have a frigate missile magazine of 24, with each missile having a kill probability of at least 0.9. Future research recommendations include examining performance in the other war areas and continuing trade-off studies for the rest of the combat systems to support decision-making in their choice, working on the design of their integration, and including cost estimates that support future planning.
