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Articles 20791 - 20820 of 198032

Full-Text Articles in Engineering

Rapid Passive Safety Determination Using Backward Reachability For Spacecraft Rendezvous And Proximity Operations, Kealy A. Murphy Mar 2024

Rapid Passive Safety Determination Using Backward Reachability For Spacecraft Rendezvous And Proximity Operations, Kealy A. Murphy

Theses and Dissertations

As the prevalence of autonomous space systems rise, there is an urgent demand for robust and precise safety analysis. The future of RPO necessitates coordination of satellites in a dynamic and congested space environment while avoiding collisions. Passive safety in RPO refers to the implementation of strategies that minimize the collision risk in the event of orbital or control deviations. This multifaceted problem includes maintaining KOZ, utilizing predictive modeling to anticipate collision scenarios, and designing spacecraft with robust GNC systems allowing for timely course corrections. The current literature’s focus has been on the separation distance between spacecraft as a primary …

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Statistical Reliability Estimation Of Space Launch Vehicles, Brooke N. Wagenblast Mar 2024

Statistical Reliability Estimation Of Space Launch Vehicles, Brooke N. Wagenblast

Theses and Dissertations

Space launch vehicle reliability is imperative to understand since launch vehicles are crucial in getting payloads into space for a hopefully successful mission. This thesis examines the reliability of commercial, civil, and military space launch vehicles through trend analysis and a variety of statistical methods. Data sets obtained from the Seradata database are analyzed for trends by looking at data subsets including launch date, launch country, final mission orbit, section (commercial, civil or military), launch vehicle family and failed subsystem. First-level Bayesian analysis and mean success rates are performed, primarily split up by launch vehicle family and total launches, and …

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Evaluating Butterfly Orbits In The Earth-Moon Corridor For Ssa, Lunar Surface Surveillance, And Cislunar Disposal, Contessa G. Norris Mar 2024

Evaluating Butterfly Orbits In The Earth-Moon Corridor For Ssa, Lunar Surface Surveillance, And Cislunar Disposal, Contessa G. Norris

Theses and Dissertations

The increased space activity in the region of cislunar space has created a high demand to identify, track, and monitor Resident Space Objects (RSOs) and provide cislunar disposal routes for RSOs. This research investigates the practicality of various satellite maneuvers between orbits chosen from the butterfly and dragonfly orbit families. Several simulated trajectories are compared to show the feasibility of performing a maneuver in cislunar and lunar space between the L1 and L2 Lagrange points. Additionally, lunar surface space situational awareness (SSA) capabilities of northern and southern butterfly (BN/BS) orbits were evaluated and compared to provide the most favorable dynamic …

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A Nonlinear Least Squarees Approach To Orbit Determination In Near-Earth Orbits, Ryan M. Vorst Mar 2024

A Nonlinear Least Squarees Approach To Orbit Determination In Near-Earth Orbits, Ryan M. Vorst

Theses and Dissertations

This work explores relevant scenarios to implement a Frequency on Arrival method using nonlinear least squares to determine a transmitting satellite’s orbit based only on measurements of the received radio frequency. Multiple relevant collection geometries, such as a target in prograde low earth orbit, in retrograde low earth orbit, in sun synchronous orbit, in near-perigee highly elliptical orbit, in near-apogee highly elliptical orbit, and in geosynchronous orbit, are simulated to collect theoretical received frequency data. Once data collection has been simulated, the theoretical apparent frequencies recorded are used in a nonlinear least squares method with differential correction to find a …

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The Effects Of A Non-Uniform Magnetic Field On Solar Cell Efficiency, Jason A. Burdette Mar 2024

The Effects Of A Non-Uniform Magnetic Field On Solar Cell Efficiency, Jason A. Burdette

Theses and Dissertations

Commercial-grade silicon-based solar cells have an efficiency in the 20-30% range. The addition of a non-uniform magnetic field manipulates the movement of charge carriers within the silicon of a solar cell. With this manipulation, one hypothesis is that the magnetic field increases the current produced by the solar cell which helps to increase the power and efficiency of the solar cell. Measuring a solar cell’s output current and voltage both with and without the presence of a non-uniform magnetic field tests this theory. Voltage multiplied by current gives output power, and to be calculated, efficiency needs maximum output power. The …

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Characterization Of An Omega Type Bi-Anisotropic Material, Moriel Gindi Mar 2024

Characterization Of An Omega Type Bi-Anisotropic Material, Moriel Gindi

Theses and Dissertations

A theory is presented for the extraction of the complete set of material parameters for a bi-anisotropic sample consisting of conductive omega-type particles governed by the mm21′ point-group symmetry. A rectangular-to-square wave-guide can be used to obtain the required measurements by allowing three distinct orientations of the material. The focus of this work is to develop the appropriate theory detailing the derivation of how the material parameters are extracted from the measurements in an analytical methodology that is similar in manner to the well-known Nicolson-Ross-Weir (NRW) algorithm.

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A Machine Learning Approach For Multipath Characterization And Mitigation Using Chipshape Observations, Sean A. L. Quiterio Mar 2024

A Machine Learning Approach For Multipath Characterization And Mitigation Using Chipshape Observations, Sean A. L. Quiterio

Theses and Dissertations

Multipath continues to be a significant error source in satellite navigation. Recent solutions with Neural Networks (NN) model the effects of multipath on the autocorrelation function to predict errors in the Delay Lock Loop (DLL). Chipshape correlation provides a detailed look into the spreading code transitions in the time domain. It is useful in applications such as Signal Quality Monitoring (SQM) and is much more sensitive to multipath than autocorrelation. This research proposes NN models that each predict pseudorange or carrier range errors due to multipath by monitoring the chipshape correlation output. For a simulation with 50 MHz precorrelation bandwidth …

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Performance Analysis Of Intel Total Memory Encryption - Multi-Key, Charles W. Rockett Mar 2024

Performance Analysis Of Intel Total Memory Encryption - Multi-Key, Charles W. Rockett

Theses and Dissertations

Secure cloud computing is an evolution in data management and security. As cloud-based services, ranging from storage solutions accessible from mobile devices to complex applications, become integral to daily operations, securing data throughout the life cycle of its use is essential. In response, hardware companies are advancing encryption and security technologies to protect data in use to thwart unauthorized access while mitigating the performance impacts of security and encryption features. This thesis addresses TME-MK performance when enabled and disabled on a server using all host threads and with three virtualized environments assigned separate unique threads each. The primary aim is …

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Improving Rogue Radio Emitter Detection Using Siamese Networks, Mason Wright Mar 2024

Improving Rogue Radio Emitter Detection Using Siamese Networks, Mason Wright

Theses and Dissertations

Radio Frequency Fingerprinting (RFF) is the process of creating discerning signatures of emitted radio signals, most often with the goal of identifying specific devices again in the future. The security benefits of this task are intended to build upon current software-based authentication by making use of multi-factor authentication (MFA), but the related task of being able to reject unwanted emitters is limited. This paper presents a Siamese network trained on two different extracted fingerprints of raw Wi-Fi signals, along with a verifier to perform classification and rogue device detection. It was found that fingerprints using the Distortion Reconstruction (DR) technique …

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Gamma Protection Factor For A Surrogate Armored Vehicle Exposed To The Us Army Fast Burst Reactor, Ian J. Poropat Mar 2024

Gamma Protection Factor For A Surrogate Armored Vehicle Exposed To The Us Army Fast Burst Reactor, Ian J. Poropat

Theses and Dissertations

This work measures the Gamma Protection Factor (GPF) of a steel cube, which is meant to serve as a surrogate for armored vehicles. The GPF is measured at the White Sands Missile Range Fast Burst Reactor (FBR) and is modeled using MCNP® v6.2 transport simulation software. When exposed to the FBR, the GPF is found to depend roughly linearly on the distance between the reactor core and steel cube. The GPF is determined to be 1.176 ± 0.00067 at 9.21 m, 1.098 ± 0.0011 at 26.16 m, and 1.033 ± 0.00082 at 42.92 m. MCNP® estimates the GPF for the …

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Reconstruction Of Radar Range Profiles Using Dropped Channel Polarimetric Compressive Sensing, Nat Thomason Mar 2024

Reconstruction Of Radar Range Profiles Using Dropped Channel Polarimetric Compressive Sensing, Nat Thomason

Theses and Dissertations

This thesis documents the design, construction and testing of a bench-top level measurement system and verifies previously established Dropped Channel Polarimetric Synthetic Aperture Radar Compressive Sensing (DCPCS) simulation results. Compressive Sensing is a mathematical technique which can capture and represent compressible signals at sampling rates significantly below the Nyquist rate. DCPCS is a technique which enhances Compressive Sensing techniques using known physical antenna crosstalk values. The DCPCS technique enables reconstruction of fully polarimetric signals whilst only measuring part of the signal, reducing data capture requirements.

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Investigation Of High-Latitude Gnss Radio Occulation Sporadic-E And Auroral-E Measurements, Kyle D. Roberts Mar 2024

Investigation Of High-Latitude Gnss Radio Occulation Sporadic-E And Auroral-E Measurements, Kyle D. Roberts

Theses and Dissertations

Abnormal sporadic-E (Es) occurrences were found in the high latitude regions during a recent climatology study by (Hodos, 2022), that calculated sporadic-E occurrence rates derived from a data set of GPS radio occultation (GPS-RO) and ionosondes. In this study, sporadic-E GNSS-RO techniques are shown to falsely attribute sporadic-E events to auroral-E (Ea) events. A comparative study is conducted on GPS-RO measurement techniques to find false occurrence rates for various RO techniques using a single ionosonde site in Gakona, Alaska. Phase-based RO techniques were found to be more likely to falsely attribute sporadic-E as auroral-E, while amplitude …

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Neutron Spectrum Unfolding From Activation Foils Irradiated In Gamble Ii Using Deuterated Polyethylene Anodes, Christopher J. Smith Mar 2024

Neutron Spectrum Unfolding From Activation Foils Irradiated In Gamble Ii Using Deuterated Polyethylene Anodes, Christopher J. Smith

Theses and Dissertations

Neutrons can cause irreparable harm to electronics, and experiments are needed to understand their effects fully. This work explores using pulsed power, which is low-cost compared to other sources, to create a useful neutron-rich environment. Deuterated polyethylene was used as anode and catcher material to generate the neutrons from the Deuterium-Deuterium (DD) fusion reaction. A simple, effective, and repeatable method was employed to directly cast deuterated polyethylene onto polyethylene sheets to fabricate the anode and catcher. The DD reactions were made by an ion beam-driven pulsed power generator, Gamble II, with the catcher located in the cathode. Zinc, copper, aluminum, …

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Enhancing Port Efficiency And Lead Time Reduction Through Predictive Analysis: A Case Study Of Container Management At Khalifa Bin Salman Port, Abdulaziz A. Aljalahma Mar 2024

Enhancing Port Efficiency And Lead Time Reduction Through Predictive Analysis: A Case Study Of Container Management At Khalifa Bin Salman Port, Abdulaziz A. Aljalahma

Theses and Dissertations

Khalifa bin Salman Port (KBSP), a key pillar in Bahrain's maritime infrastructure, is the focal point of this study, highlighting the significant role of predictive analytics in optimizing port operations. This thesis analyzes container throughput data from 2017 to 2022, provided by Bahrain's Ministry of Transportation database. This data forms the basis for forecasting the 2023 throughput. The study thoroughly compares these predictions with the actual 2023 data, assessing the predictive model's accuracy. The findings underscore the importance of predictive analytics in strategic decision-making for port management, focusing on enhancing operational efficiency and reducing lead times. This research offers a …

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Optimizing Deployment Kit, Introducing Acceptance Threshold, Saleh A. Alshuhri Mar 2024

Optimizing Deployment Kit, Introducing Acceptance Threshold, Saleh A. Alshuhri

Theses and Dissertations

This article addresses the optimization of a specialized deployment kit crucial for air force operations, emphasizing the need for rapid and efficient aircraft deployment. Through a comprehensive analysis of historical data, the study aims to streamline the kit's contents without compromising effectiveness. The research suggests a potential reduction of 7.8%, with an impressive 60.5% decrease if a minimal 5% threshold is deemed acceptable. While the primary focus is on air force deployment, the broader implications extend to military entities, such as armies and navies, highlighting the applicability of the findings in enhancing deployment efficiency across various defense sectors.

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Electric Vehicle Support Equipment Deployment At Military Installations: A Mixed-Integer Linear Programming Approach, Katelyn M. Barton Mar 2024

Electric Vehicle Support Equipment Deployment At Military Installations: A Mixed-Integer Linear Programming Approach, Katelyn M. Barton

Theses and Dissertations

This research provides insights into a mixed integer linear programming model that finds the ideal number and type of Electric Vehicle Support Equipment (EVSE) required to meet U.S. military installations’ electric energy demands. Executive Order No. 14057 (2021) requires federal agencies to transition to electric non-tactical vehicles by 2035. This research determines minimum cost solutions to implement the transition incorporating real-world constraints, including the weekly vehicle mileage demand, EVSE cost, charging time, and EVSE capacity. This study contributes to the broader effort of the U.S. military to combat climate change and enhances the understanding of efficient EVSE deployment strategies in …

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Federated Medical Scoring Systems, Jacob F. Bryant Mar 2024

Federated Medical Scoring Systems, Jacob F. Bryant

Theses and Dissertations

Federated Learning (FL) is a recent framework of machine learning implementation that trains models on a distributed network of clients as opposed to housing and analyzing this data centrally. This has data communication and practical data privacy advantages, the latter of which is particularly attractive to the medical community where patient privacy is closely safeguarded. We apply FL to a family of sparse linear integer models called Medical Scoring Systems (MSSs). We create a novel methodology for creating these MSSs in a simulated federated environment that involves an lo constrained Logistic Regression (LR), loss-surface examination, and rounding procedure. We tested …

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Systematic Review Of Supply Chain Control Tower Critical Success Factors And Resilience Effects, Clay H. Chaffin Mar 2024

Systematic Review Of Supply Chain Control Tower Critical Success Factors And Resilience Effects, Clay H. Chaffin

Theses and Dissertations

Supply chain control towers (SCCTs) are emerging as a vital component of modern supply chain management (SCM); however, research on SCCTs is limited and disjointed. This paper aims to uncover the critical success factors (CSFs) necessary for high-performing SCCTs, their relationship to the enablers and phases of supply chain resilience (SCRES), and the underlying theoretical framework of this relationship.

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Examining The Effect Of Contractor Logistics Support On The Reliability Of Military Aircraft, Rodrigo S. Campos De Moura Mar 2024

Examining The Effect Of Contractor Logistics Support On The Reliability Of Military Aircraft, Rodrigo S. Campos De Moura

Theses and Dissertations

This study utilizes survival analysis for examining the effect of Contractor Logistics Support (CLS) on the reliability of military aircraft before and after implementing CLS. The provider of CLS in this study is the original equipment manufacturer that designed and produced the target aircraft of this study, the Embraer A-29 Super Tucano.

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2033 Digital Modernization At Usmepcom: A Strategic Analysis Of Future Military Applicant Processing, William A. Clay Mar 2024

2033 Digital Modernization At Usmepcom: A Strategic Analysis Of Future Military Applicant Processing, William A. Clay

Theses and Dissertations

This research examines the projected 2033 applicant processing scenario considering the digital modernization efforts of the United States Military Entrance Processing Command (USMEPCOM). The study evaluates the necessary modifications to current processes, with a particular focus on the influence of two key information technology systems, the MEPCOM Integrated Resource System (MIRS) 1.1 and the Military Health System (MHS) Genesis, on manpower at a Military Entrance Processing Station (MEPS). In doing so, the study establishes baseline processing metrics for assessing these impacts. By utilizing discrete event simulation modeling and leveraging current literature, the study proposes strategies for incorporating technological advancements into …

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Evaluation Of Vtol-Capable Cargo Uavs For Dispersible Airfield Logistics In The Usindopacom Aor, Maria C. Chedzoy Mar 2024

Evaluation Of Vtol-Capable Cargo Uavs For Dispersible Airfield Logistics In The Usindopacom Aor, Maria C. Chedzoy

Theses and Dissertations

This research models and analyzes the ability of commercial cargo UAVs to rapidly evacuate logistics from an airfield to proximal, outlying destinations, particularly in the USINDOPACOM AOR. This is a tenet of Agile Combat Employment by the USAF, which seeks to mitigate the effect of kinetic threats by near-peer adversaries. The analysis sets forth a binary linear program to minimize the total time to evacuate a fixed amount of logistics from an airfield. Parameters include the cargo UAV with its performance specifications, number of cargo loading points at the airfield, number of destinations for cargo evacuation, and subset of destinations …

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On Intrinsic Dimensionality Of Data Sets And Neural Networks, Ori Chachmo Mar 2024

On Intrinsic Dimensionality Of Data Sets And Neural Networks, Ori Chachmo

Theses and Dissertations

The concept of Intrinsic Dimensionality (ID) is of special interest in the field of Neural Networks (NNs) since it promotes both (a) a deeper understanding of the underlying mechanisms, and (b) embraces parsimonious modeling (that is, building the right-sized model for the task) with associated benefits to processing speed and storage requirements. This thesis explores the concept of ID via two separate, but related, questions. First, we study the potential of NN ID prediction by exploiting easily obtained quantities measured on the data. We then explore NN ID as an independent concept by comparing the results of different methods for …

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Reinforcement Learning For Team Based Air Combat Maneuvering Decisions With Directed Energy Weaponry, Joshua D. Combs Mar 2024

Reinforcement Learning For Team Based Air Combat Maneuvering Decisions With Directed Energy Weaponry, Joshua D. Combs

Theses and Dissertations

Leveraging the Advanced Framework for Simulation, Integration, and Modeling (AFSIM) we investigate the use of reinforcement learning (RL) techniques for imbuing AUCAV agents with high-quality behaviors for the within-visual-range air combat maneuvering problem (ACMP). We formulate the 2v2 WVR ACMP as a Markov decision process wherein friendly AUCAVs are equipped with DEW capabilities and operate with 6 degrees of freedom. We utilize the Double Deep Q-Network RL algorithm, which centrally trains two friendly AUCAVs and employ a phased learning approach, initially exposing the AUCAVs to a dense reward environment for early training, followed by a sparse reward environment to encourage …

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Advanced Intermediate Manufacturing (Aim) Supply Chain Concepts Leading To Reduced Lead Times And Improved Responsiveness, Eric S. Draudt Mar 2024

Advanced Intermediate Manufacturing (Aim) Supply Chain Concepts Leading To Reduced Lead Times And Improved Responsiveness, Eric S. Draudt

Theses and Dissertations

This thesis investigates the optimization of the supply chain for key aircraft components, focusing on the implementation of Advanced Intermediate Manufacturing (AIM) production facilities. Utilizing anyLogistix, the study compares the current supply chain model based on Supply Chain Operations Wing (SCOW) data with various AIM production facility configurations: single, dual, quadruple, and three utilization-driven models (high, medium, and low). The findings demonstrate that integrating AIM production facilities significantly reduces lead times, with even a single facility dramatically cutting down the lead time from over 800 days to approximately 104 days. The utilization models further provide insights into operational flexibility under …

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An Integer Programming Model To Optimize Us Army Deployment Cycle And Maximize Unit Availability, Grant R. Engel Mar 2024

An Integer Programming Model To Optimize Us Army Deployment Cycle And Maximize Unit Availability, Grant R. Engel

Theses and Dissertations

The goal of this paper is to determine an optimal cycle length, in months, that minimizes costs and maximizes availability for deploying units in the United States (US) Army. The US Army must be cost efficient while maintaining the flexibility required to adapt to dynamic mission demand. The current practice is to deploy units for a length between the range of 6 to 12 months; however, this varies from unit to unit and the best policy is not clear. We address these issues by forming a mathematical programming model with unique characteristics that distinguish it from others of similar design. …

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A Multi-Objective Approach To Optimal Deployment Policies For Wireless Sensor Networks Using Drop Points, Noah E. Fox Mar 2024

A Multi-Objective Approach To Optimal Deployment Policies For Wireless Sensor Networks Using Drop Points, Noah E. Fox

Theses and Dissertations

This research addresses the development of deployment policies for aerially dropped sensors in a wireless sensor network (WSN). Multi-objective genetic algorithm (GA) and simulated annealing meta-heuristic techniques, along with Monte Carlo simulation are used to identify policies with the aim of maximizing coverage and minimizing the number of sensors deployed. The policies developed from these techniques are then compared against uniform sensor distribution, as well as initial deployment policies that focus sensors in the center and edge of the region, as well as evenly deployed over the region. A total of 29 non-dominated policies were identified from the GA and …

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Techniques For Addressing Extreme Class Imbalance For Artificial Neural Networks Training, Colin W. Foley Mar 2024

Techniques For Addressing Extreme Class Imbalance For Artificial Neural Networks Training, Colin W. Foley

Theses and Dissertations

This research examined the class imbalance problem while training convolutional neural networks (CNN) by applying different techniques to combat this common issue. This research used a modified CIFAR-10 dataset along with a curated aerial image dataset. Methods covered included undersampling, oversampling, synthetic minority oversampling technique, Edited Nearest Neighbors and combinations of the aforementioned methods. This research found that undersampling methods tended to outperform oversampling methods. While undersampling methods showed a decrease in overall accuracy, the increase in minority class prediction performance was promising enough to warrant further investigation.

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An Analysis Of China’S Perceived Geographic Locations Of Interest By Use Of Value Informed Facility Location Models, Layton C. Hedge Mar 2024

An Analysis Of China’S Perceived Geographic Locations Of Interest By Use Of Value Informed Facility Location Models, Layton C. Hedge

Theses and Dissertations

This research examines China and derives insights specific to it and the First Island Chain and the Second Island Chain. In doing so, this research demonstrates a methodology to examine other competitors and their geostrategic interests. In the first phase of analysis, it develops a value hierarchy to depict objectives within subregions of the area of interest and considers four alternative weightings of the value hierarchy. In the second phase of analysis, it applies four location-covering models to assess how the competitor would emplace a range of limited resources to deter and/or control points of interest. Results indicate that land-based …

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Analysis And Visualization Of Military Convoy And Supply Utilization In Support Of State-Specific Freight Plans, Madison E. Hofmann Mar 2024

Analysis And Visualization Of Military Convoy And Supply Utilization In Support Of State-Specific Freight Plans, Madison E. Hofmann

Theses and Dissertations

Researching the United States military’s use of highways and interstates is necessary for the allocation of federal infrastructure spending. As of today, there is no established method, tool, or process routinely utilized by the Surface Deployment and Distribution Command to effectively show a system-wide view of military convoy and supply route usage across CONUS. This research advances this endeavor by providing a by-state characterization of interstates and major highways in 2022, categorized by the volume of military freight they support. Some notable methodologies used to conduct the analyses are the shortest path problem, map matching algorithms, and Global Positioning System …

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Usmepcom Prescreens: A Value-Focused Thinking Approach, Phillip M. Koenig Mar 2024

Usmepcom Prescreens: A Value-Focused Thinking Approach, Phillip M. Koenig

Theses and Dissertations

As the recruiting crisis continues to impact the United States Armed Forces, the United States Military Entrance Processing Command (USMEPCOM) continues to search for ways to increase its capability to efficiently determine which applicants are suited for military service. Unfortunately, USMEPCOM does not have a way to evaluate newly suggested alternatives. By leveraging Value-Focused Thinking (VFT), this research describes 28 fundamental objectives that can be applied to a variety of current and future decision problems. Further, this research applies these fundamental objectives to analyze a current decision problem: reengineering the prescreen process to decrease the time from prescreen submission to …

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