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NPS Outstanding Theses and Dissertations

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Degree-Earning Works
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Publication Search Results

Now showing 1 - 10 of 1370
  • Publication
    THREE-DIMENSIONAL DISCRETE ELEMENT MODELING OF FIRST-YEAR SEA ICE RIDGES
    (Monterey, CA; Naval Postgraduate School, 2019-06) Davis, Travis J.; Radko, Timour; Roberts, Andrew F.; Oceanography; Turner, Adrian, Los Alamos National Laboratory
    A three-dimensional discrete element model has been developed to investigate the evolution of particular aspects of pressure ridges in thin, first-year, sea ice. The primary goal of this work is to test one facet of recent theoretical advances in the representation of sea ice thickness in Earth System Models that advocates for the introduction of macro-porosity, R, to the state space of basin-scale sea ice models. Macro-porosity is caused by cavities between fractured sea ice blocks created during the formation of ridges during convergence of ice floes in the Southern and Arctic Oceans. Previously, sea ice thickness in basin-scale sea ice models has been represented by a real thickness distribution, g(h), but new mathematical derivations suggest that this should be replaced in predictive models with a bivariate distribution, g(h, R). In this thesis, a discrete element model of sea ice is described and then used to investigate the evolution of R in three-dimensional ridges. Changes in R over time are extremely difficult to measure in the Arctic, and therefore this research bridges observational constraints and theoretical assumptions. The final results suggest that, within the constraints of the given discrete element model, a more sudden change in macro-porosity occurs at the initial creation of a ridge than current theory suggests, but thereafter evolution of macro-porosity follows a path similar to what a Coulombic friction model predicts.
  • Publication
    The cold gas-dynamic spray and characterization of microcrystalline and nanocrystalline copper alloys
    (Monterey, California. Naval Postgraduate School, 2012-12) Marple, William J.; Brewer, Luke N.; Mechanical and Aerospace Engineering (MAE); Osswald, Sebastian
    This thesis presents research on the cold gas-dynamic spray processa relatively new technology that may be utilized to create metal coatings in the solid state. While the thermodynamics and fluid mechanics of the cold gas-dynamic spray process are well understood, the effects of feedstock powder microstructure and composition on the deposition process remain largely unknown. In particular, this thesis aims to shed light on these effects as they pertain to common face-centered cubic metals and their alloysnotably copper and brass. Deposition efficiency, coating thickness per pass, hardness, porosity and compositional variance were all characterized as functions of spraying pressure, spraying temperature and feedstock particle composition in each of the materials. This thesis presents evidence that while brass can be deposited using cold gas-dynamic spray, the resulting material does not possess a dense, uniform microstructure. In fact, deposits made with Cu-90/10 wt.% Zn brass have more than 400% more porosity than standard copper coatings, possess extensive microstructural cracking and wide compositional variance from grain to grain.
  • Publication
    SPEND ANALYSIS ON ACQUISITION FOR STUDIES AND ANALYSIS IN THE U.S. NAVY
    (Monterey, CA; Naval Postgraduate School, 2019-12) Brill, Thad R., Jr.; Surarujiroj, Puriphat; Rendon, Rene G.; Muir, William A.; Department of Defense Management (DDM); Graduate School of Defense Management (GSDM); Graduate School of Defense Management (GSDM)
    The purpose of this research is to analyze the U.S. Navy’s procurement of studies and analysis to identify contracting offices, contractors, service categories, and contracting characteristics. Studies and analysis are services that influence Navy decision-makers and defense capabilities; therefore, it is vital to know how the Navy acquires study and analysis services. Knowledge from this analyzed spending data provides opportunities for decision-makers to see spending characteristics, efficiencies, and relationships between contracting offices, contractors, and study and analysis service categories. The results from this research also provide a foundation for strategic sourcing strategies to improve support of national defense strategies. This research reaches two recommendations concerning the limitation of the current taxonomy in place and the strategies that may be most beneficial to the various categories of services. The research also serves as a lead for further study on the adoption of new categorization tools, better understanding of what drives contracting officers to use category descriptions such as “Defense” or “Other,” and the effectiveness of the distribution of study and analysis services.
  • Publication
    Residual network data structures in Android devices
    (Monterey, California. Naval Postgraduate School, 2011-09) Cardwell, Gregory S.; Beverly, Robert; Garfinkel, Simson; Naval Postgraduate School (U.S.); Computer Science
    The emergence and recent ubiquity of Smartphones present new opportunities and challenges to forensic examiners. Smartphones enable new mobile application and use paradigms by being constantly attached to the Internet via one of several physical communication media, e.g. cellular radio, WiFi, or Bluetooth. The Smartphone's storage medium represents a potential source of current and historical network metadata and records of prior data transfers. By using known ground truth data exchanges in a controlled experimental environment, this thesis identifies network metadata stored by the Android operating system that can be readily retrieved from the device's internal non-volatile storage. The identified network metadata can ascertain the identity of prior network access points to which the device associated. An important by-product of this research is a well-labeled Android Smartphone image corpus, allowing the mobile forensic community to perform repeatable, scientific experiments, and to test mobile forensic tools.
  • Publication
    The role of efficient XML interchange (EXI) in Navy wide-area network (WAN) optimization
    (Monterey, California: Naval Postgraduate School, 2015-03) Debich, Steven J.; Brutzman, Donald P.; Miller, Scot A.; Information Sciences (IS); McGregor, Don
    Navy afloat units become disadvantaged users, once disconnected from the pier, due in part to the high latency associated with SATCOM. Unfortunately recent gains in SATCOM capacity alone do not overcome throughput limitations that result from latency’s effect on connection-oriented protocols. To mitigate the effect of latency and other performance inhibiting factors, the Navy is improving its current WAN optimization capabilities by implementing Riverbed Steelhead WOCs. At-sea testing has shown Steelhead increases effective SATCOM capacity by 50%. Laboratory testing demonstrates that by encoding structured and semi-structured data as EXI rather than XML, compression ratios can be further improved, up to 19 times greater than Steelhead’s compression capability alone. Combining EXI with Steelhead will further improve the efficient use of existing SATCOM capacity and enable greater operational capabilities, when operating in a communications constrained environment. Not only does EXI improve compactness of traffic traveling over relatively high capacity SATCOM channels, it also expands net-centric capabilities to devices operating at the edge of the network that are restricted to lower capacity transmission methods. In order to achieve these substantial improvements the Navy must incorporate the already mandated DISR standard, EXI, as the single standard for all systems transferring structured and semi-structured data.
  • Publication
    THE EFFECTS OF PARENTAL LEAVE POLICY CHANGES WITHIN THE UNIFORMED MILITARY SERVICES
    (Monterey, CA; Naval Postgraduate School, 2019-03) Laurita, Laura; Molloy, Matthew; Bacolod, Marigee; Heissel, Jennifer A.; Department of Defense Management (DDM); Business and Public Policy (GSBPP); Business and Public Policy (GSBPP)
    The United States has no federal mandates for paid family leave (PFL), an unusual standing among the world’s developed countries. Recent Department of Defense (DoD) policy initiatives have expanded paid maternity and family leave to offer more support to new mothers and other caregivers. The DoD’s increase in maternity leave is a unique policy change for a large and diverse organization. Family leave policies are established as an incentive for attracting and retaining talent. Military leadership emphasized the need to retain the talent and value of female service members as motivation for recent paid maternity leave expansion. Few papers have examined how large-scale programs such as PFL affect parental behavior across demographics in the United States. With a better understanding of the effects from PFL policy changes, the military can employ policy aimed at retaining service members. Our paper examines recent changes to DoD parental leave policy for active duty service members. In 2015, the Department of the Navy tripled paid maternity leave from 6 to 18 weeks. In 2016, the DoD standardized paid maternity leave, reducing Navy and Marine Corps policy from 18 to 12 weeks of maternity leave and expanding Army and Air Force policy from 6 to 12 weeks of maternity leave. Our study uses difference-in-difference and regression discontinuity design methods to examine the impact of these policy changes on retention, birth and pregnancy outcomes, and parental leave taken.
  • Publication
    Automated detection of a crossing contact based on its Doppler shift
    (Monterey, California. Naval Postgraduate School, 2009-03) How, Whye Keong; Kapolka, Daphne; Rice, Joseph; Naval Postgraduate School (U.S.)
    The trade-off between false alarm and detection probability is a fundamental challenge in the automated detection of contacts in passive sonar systems. A common approach is the application of highgain processing followed by successive classification criteria. Most classification schemes (e.g., matching of signature) are complex and tailored to specific target types. By contrast, the Doppler effect is readily observed in all contacts with discrete tonals and relative velocity to the receiver. This thesis demonstrates that the Doppler effect can be exploited to improve the detection process by filtering out contacts that do not exhibit these characteristics. Cross-correlation (matched filtering) of contact LOFARgrams with templates generated in situ with Doppler compression/dilation is used to achieve this. Velocity information and the range of the Closest Point of Approach (CPA) are estimated in the process. A detection algorithm is developed in MATLAB, and the radiated acoustic signatures of overflying airplanes are recorded at a ground station. In the analysis of six propeller and four jet airplanes, the program successfully identifies the passage of all six propeller airplanes with four incidences of false alarm, due in one case to a jet airplane. Velocity and range estimates are also within expected values.
  • Publication
    BATTERY USAGE IN THE FUTURE FLEET
    (Monterey, CA; Naval Postgraduate School, 2022-09) Auld, Sean G.; Camp, Daniel V.; Kylander, Paul; Vey, Nathan; Willis, Jerald J.; Eldred, Ross A.; Van Bossuyt, Douglas L.; Systems Engineering (SE); Systems Engineering (SE); Systems Engineering (SE); Systems Engineering (SE); Systems Engineering (SE); Lussier, Jonathan
    This research effort examined the current advanced battery requirement (baseline) and projects anticipated battery requirements for the operating force in 2035 and 2045. The research is conducted using a mission engineering perspective to determine the battery requirements. The analysis includes battery chemistry, energy density, charge/discharge rate, safety concerns, and the like, of the battery. In this research the following questions are answered: What is the current advanced battery requirement (baseline)? What is the projection for batteries required by the operating force by 2035? What is the projection for batteries required by the operating force by 2045? Upon completion of the research, the team was able to definitively determine that there will be a role for Li-ion batteries within the fleet of Navy vessels. That role will, however, be limited to running specific subsystems or equipment and will not replace the ship generators. This will remain true until the energy density of battery technology even begins to approach that of petrochemicals, which we believe is many years away if possible.
  • Publication
    Viability of Cross-Flow Fan for Vertical Take-Off and Landing Aircraft
    (Monterey, California. Naval Postgraduate School, 2012-06) Delagrange, Christopher T.; Hobson, Garth V.; Naval Postgraduate School (U.S.); Mechanical Engineering; Gannon, Anthony J.
    The present study is focused on determining a housing design that, when paired with an off-the-shelf cross-flow fan rotor, will generate a trust-to-weight ratio significant enough to allow for vertical take-off. The commercial computational fluid dynamics software, ANSYS CFX, was used to perform a computational analysis of various housing designs until a suitable design was identified to construct for experimentation. Following the analytical phase, the conceptual housing was fabricated and paired with an appropriate rotor to validate the predicted performance. The experimental model was operated at speeds from 4,000 to 8,000 rpm and the actual and projected thrust calculations were found to agree with a maximum difference of less than 7percent.
  • Publication
    COST-BENEFIT ANALYSIS OF CONVERTING WASP CLASS LANDING HELICOPTER DOCK (LHD) STEAM PROPULSION PLANTS TO HYBRID PROPULSION
    (Monterey, CA; Naval Postgraduate School, 2019-12) Jablonski, Joseph G.; Rodriguez, Richard; Bacolod, Marigee; Graduate School of Defense Management (GSDM); Graduate School of Defense Management (GSDM); Menichini, Amilcar A.
    The purpose of this thesis is to conduct a cost-benefit analysis of converting steam-powered propulsion plants on-board Wasp-Class Landing Helicopter Dock (LHD) hulls 1 through 7 to hybrid propulsion. The objective of this research was to evaluate the net present value of conversion by weighing the cost-savings benefits of fuel savings, in-port utility consumption, and manpower against the cost of conversion. The results of the analysis conclude that LHDs 5 and 7 have a positive net present value; therefore, their conversion is recommended. LHD 6 can have a positive net present value with recommended complex overhaul schedule changes. Recommendations are made to maximize benefits to the Navy, considering potential changes in force structure and follow-on studies.