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Air Force Institute of Technology

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Articles 1561 - 1590 of 5699

Full-Text Articles in Engineering

Relating Film Cooling Performance Between Ambient And Near Engine Temperatures, Christopher J. Vorgert Mar 2017

Relating Film Cooling Performance Between Ambient And Near Engine Temperatures, Christopher J. Vorgert

Theses and Dissertations

This thesis explores multiple topics, including the relative importance of nondimensional parameters that relate film cooling performance within different temperature regimes and the effects of internal coolant flow and coolant temperature on overall film cooling effectiveness. A Hastelloy model representative of a turbine blade was utilized for IR tests. Near engine temperatures were produced via premixed propane and air combustion in a Well-Stirred Reactor (WSR) with air supplied as the film coolant gas. Near ambient conditions used heated air for freestream flow and carbon dioxide, argon, or air as film coolant gases. It was found that even with multiple matched …

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Identifying Partnership Opportunities At Air Force Installations: A Geographic Information Systems Approach, Corey R. Degroot Mar 2017

Identifying Partnership Opportunities At Air Force Installations: A Geographic Information Systems Approach, Corey R. Degroot

Theses and Dissertations

The excess capacity found in the Department of Defense real property portfolio creates challenges for leaders to provide resilient installations. Combining this fact with current funding trends makes decisions on how to properly maintain infrastructure even more challenging. The Air Force Partnership Initiative provides tools for installations to leverage community capabilities and resources to achieve savings and improve quality on Air Force installations and can reduce the real property footprint. This research proposes a method for assessing the viability of a partnership between Air Force installations and their nearby communities.
This research effort created a tool capable of investigating off-base …

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Cost Versus Risk: The Policy Of Nuclear Weapon Maintenance Of Tritium Based Limited Life Components, Michael P. Mason Mar 2017

Cost Versus Risk: The Policy Of Nuclear Weapon Maintenance Of Tritium Based Limited Life Components, Michael P. Mason

Theses and Dissertations

This research develops a method to measure the cost to society of current maintenance policy for the exchange of tritium based limited life components within nuclear weapons. The incentives for the Department of Energy and Department of Defense which causes either a substantial cost or substantial risk to be accepted by either Department. A simulation model is created to measure the current policy and compare it to different policies in order to recommend a policy that would minimize the cost to society. The measurement of the cost to society will offer decision makers insight into the ramifications of their decisions.

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Analyzing The Critical Supply Chain For Unmanned Aircraft Systems, Megan L. Muniz Mar 2017

Analyzing The Critical Supply Chain For Unmanned Aircraft Systems, Megan L. Muniz

Theses and Dissertations

Unmanned aerial systems (UAS) play a vital role in present day operations due their asset capability and ability to reduce risk to pilots’ lives. A complex supply chain network capable of producing and integrating all raw materials, components, sub- systems, and systems supports the successful acquisition of a UAS. Such a complex network is supported by vital supply chain decisions. Two important decisions regarding supply chain design include supplier selection and optimal flow of material and product Whether a decision maker wishes to design or interdict a supply chain, the methodology developed in this thesis provides a suite of tailorable …

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United States Air Force Unaccompanied Housing Divestiture: An Economic Analysis, Dustin L. Gooden Mar 2017

United States Air Force Unaccompanied Housing Divestiture: An Economic Analysis, Dustin L. Gooden

Theses and Dissertations

The objective of this research is to determine potential cost savings associated with Air Force unaccompanied housing divestiture. This research uses Air Education and Training Command (AETC) installations as the data sample for the analysis, and will analyze the status quo, privatization, and identical FSRM options. With 16% of Air Force unaccompanied housing currently rated at various levels of inadequacy and the PRV for the inadequate housing at $2,315,773,149.00, the costs associated with renovating the inadequate unaccompanied housing is substantial. Moreover, the inadequacy of unaccompanied housing is part of the Air Force’s acceptance of risk in facilities and infrastructure to …

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On Proportionate And Truthful International Alliance Contributions: An Analysis Of Incentive Compatible Cost Sharing Mechanisms To Burden Sharing, William N. Caballero Mar 2017

On Proportionate And Truthful International Alliance Contributions: An Analysis Of Incentive Compatible Cost Sharing Mechanisms To Burden Sharing, William N. Caballero

Theses and Dissertations

Burden sharing within an international alliance is a contentious topic, especially in the current geopolitical environment, that in practice is generally imposed by a central authority's perception of its members' abilities to contribute. Instead, we propose a cost sharing mechanism such that burden shares are allocated to nations based on their honest declarations of the alliance's worth. Specifically, we develop a set of multiobjective nonlinear optimization problem formulations that respectively impose Bayesian Incentive Compatible (BIC), Strategyproof (SP), and Group Strategyproof (GSP) mechanisms based on probabilistic inspection efforts and deception penalties that are budget balanced and in the core. Any feasible …

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Using Markov Decision Processes With Heterogeneous Queueing Systems To Examine Military Medevac Dispatching Policies, Phillip R. Jenkins Mar 2017

Using Markov Decision Processes With Heterogeneous Queueing Systems To Examine Military Medevac Dispatching Policies, Phillip R. Jenkins

Theses and Dissertations

major focus of the Military Health System is to provide efficient and timely medical evacuation (MEDEVAC) to battlefield casualties. Medical planners are responsible for developing dispatching policies that dictate how aerial military MEDEVAC units are utilized during major combat operations. The objective of this research is to determine how to optimally dispatch MEDEVAC units in response to 9-line MEDEVAC requests to maximize MEDEVAC system performance. A discounted, infinite horizon Markov decision process (MDP) model is developed to examine the MEDEVAC dispatching problem. The MDP model allows the dispatching authority to accept, reject, or queue incoming requests based on the request's …

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Refugees In Urban Environments: Social, Economic, And Infrastructure Impacts, Garrett L. Jameson Mar 2017

Refugees In Urban Environments: Social, Economic, And Infrastructure Impacts, Garrett L. Jameson

Theses and Dissertations

The United Nations High Commissioner for Refugees has estimated that in 2015 there were 21.3 million refugees worldwide; it is estimated that 1.8 million of these persons were newly displaced during 2015. As refugees leave their country to seek the protection of another nation's government, they generally flow into urban areas. The impact of this flow on cities and on the refugees, themselves, is not fully understood. This study is focused on the impact of government policy decisions on the social, legal, and economic integration of refugees within an urban environment. Investigation into this topic resulted in the development of …

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Simulation Modeling And Analysis Of Deployed F-16 Operations And Logistics Support, Gregory D. Potts Ii Mar 2017

Simulation Modeling And Analysis Of Deployed F-16 Operations And Logistics Support, Gregory D. Potts Ii

Theses and Dissertations

The purpose of this thesis is to reinforce and build upon past efforts identifying and demonstrating the need to better represent logistic capabilities and constraints within the realm of wargaming, war planning, and other analyses requiring the modeling of Air Force combat operations. We develop a framework for the porting of relevant logistic information and requirements from a reliable data source (LCOM- ATK) into a discrete event simulation environment (SIMIO), providing a simulation model for enhanced and robust analyses. The simulation we create explicitly reflects (for a selected subset of Work Unit Codes) the maintenance manpower, resources, and parts required …

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An Approximate Dynamic Programming Approach For Comparing Firing Solutions In A Networked Air Defense Environment, Daniel S. Summers Mar 2017

An Approximate Dynamic Programming Approach For Comparing Firing Solutions In A Networked Air Defense Environment, Daniel S. Summers

Theses and Dissertations

The United States Army currently employs a shoot-shoot-look firing policy for air defense. As the Army moves to a networked defense-in-depth strategy, this policy will not provide optimal results for managing interceptor inventories in a conflict to minimize the damage to defended assets. The objective for air and missile defense is to identify the firing policy for interceptor allocation that minimizes expected total cost of damage to defended assets. This dynamic weapon target assignment problem is formulated first as a Markov decision process (MDP) and then approximate dynamic programming (ADP) is used to solve problem instances based on a representative …

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Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 900°C In Air And In Silicic Acid-Saturated Steam, Ronald K. Mitchell Mar 2017

Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 900°C In Air And In Silicic Acid-Saturated Steam, Ronald K. Mitchell

Theses and Dissertations

Advanced SiC/SiC ceramic matrix composites (CMCs) are being considered for demanding aerospace applications such as aircraft engine hot-section components. In these applications the composites will be subjected to cyclic and sustained loadings at elevated temperature in aggressive combustion environments. Current aircraft engines employ Nickel-based superalloys in applications such turbine blades, where the metallic alloys must perform at or near their operating temperature limits in highly corrosive environments. The SiC/SiC composites, which offer low density, high strength and fracture toughness at elevated temperatures could potentially replace Nickel-based superalloy in aircraft engine applications. However, before the SiC/SiC composites can be safely used …

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Resource Evaluation Of Quantum Linear Systems Algorithm For Application To Electromagnetic Scattering Problems, Casey J.R. Riggs Mar 2017

Resource Evaluation Of Quantum Linear Systems Algorithm For Application To Electromagnetic Scattering Problems, Casey J.R. Riggs

Theses and Dissertations

Current limitations in quantum computing technology does not allow for very large applications of quantum algorithms, and it is the nature of quantum algorithms not only to be able to solve problems of interest much more quickly than classical means but also to do so with less resources which makes them so promising! One such problem of interest is the application of the Quantum Linear Systems Algorithm, along with a few other subroutines, to the calculation of an electromagnetic scattering cross-section via finite element methods. This work composes a resource analysis of the algorithm as well as required subroutines and …

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Combined Stereo Vision And Inertial Navigation For Automated Aerial Refueling, Daniel T. Johnson Mar 2017

Combined Stereo Vision And Inertial Navigation For Automated Aerial Refueling, Daniel T. Johnson

Theses and Dissertations

This paper describes the design of an EKF to obtain the precise relative position of two aircraft in a refueling maneuver while operating in GPS denied environments. The EKF uses the INS already present in both aircraft as well as the stereo camera system organic to new tanker systems. The aircraft trajectories are generated according to authentic refueling profiles with flight dynamics software and executed in a 3D virtual environment to enable deterministic simulation of the stereo camera system and to demonstrate the effectiveness of the combined system in a refueling scenario. Results show the system can achieve sufficient accuracy …

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Stressed Oxidation Of Hafnium Diboride In Air At 1500°C, Thomas A. Bowen Mar 2017

Stressed Oxidation Of Hafnium Diboride In Air At 1500°C, Thomas A. Bowen

Theses and Dissertations

Hypersonic vehicles with narrow airfoils produce thin boundary layers and shock temperatures in excess of 2000°C, exceeding the operating limits of traditional aerospace materials. The use of ultra-high temperature ceramics (UHTCs) allows for operating temperatures far exceeding those of metallic alloys. One such UHTC is hafnium diboride (HfB2). Transition metal diborides generally experience significant oxidation degradation at elevated temperatures. The use of additives, such as silicon carbide (SiC) has been shown to reduce the oxidation of transition metal diborides. This research focused on the compressive creep of HfB2 with varying amounts of SiC in air at 1500°C. …

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Investigating Analytical And Numerical Methods To Predict Satellite Orbits Using Two-Line Element Sets, Adam T. Rich Mar 2017

Investigating Analytical And Numerical Methods To Predict Satellite Orbits Using Two-Line Element Sets, Adam T. Rich

Theses and Dissertations

As Low Earth Orbit (LEO) contains an ever-increasing number of objects, the prediction of future object positions must be precise in order to avoid collisions. Object positions are distributed in two-line element (TLE) sets and are generated using the analytical propagator known as Simplified General Perturbations 4 (SGP4). However, a numerical integrator called Special Perturbations (SP) provides an alternative approach to TLE generation and propagation. In this thesis, TLE accuracy was determined with both models, and the length of time that a single element set can provide valid information was also established. With two-line element sets as data, comparisons were …

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Satellite Communications In The V And W Band: Natural And Artificial Scintillation Effects, David A. Smith Mar 2017

Satellite Communications In The V And W Band: Natural And Artificial Scintillation Effects, David A. Smith

Theses and Dissertations

In a natural atmospheric environment the troposphere will be the primary source of loss with the ionosphere loss being negligible. If the ionosphere was disturbed from a high altitude nuclear explosion (HANE) more than three times the amount of electrons would be present in the ionosphere and could represent a source of significant loss. In order to determine the amount of electrons distributed from a HANE, GSCENARIO, developed by Defense Threat Reduction Agency was used. The two sources of loss that were examined was signal absorption and amplitude scintillation. Signal loss was determined using GSCENARIO and amplitude scintillation loss was …

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Analysis Of Human And Agent Characteristics On Human-Agent Team Performance And Trust, Anthony J. Hillesheim Mar 2017

Analysis Of Human And Agent Characteristics On Human-Agent Team Performance And Trust, Anthony J. Hillesheim

Theses and Dissertations

The human-agent team represents a new construct in how the United States Department of Defense is orchestrating mission planning and mission accomplishment. In order for mission planning and accomplishment to be successful, several requirements must be met: a firm understanding of human trust in automated agents, how human and automated agent characteristics influence human-agent team performance, and how humans behave. This thesis applies a combination of modeling techniques and human experimentation to understand the concepts aforementioned. The modeling techniques used include static modeling in SysML activity diagrams and dynamic modeling of both human and agent behavior in IMPRINT. Additionally, this …

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Alternate Stimuli For The Elicitation Of Event-Related Potentials, Bryan V. Jackson Mar 2017

Alternate Stimuli For The Elicitation Of Event-Related Potentials, Bryan V. Jackson

Theses and Dissertations

Brain-Computer Interfaces (BCIs) are systems that leverage user-brain activity to identify and perform specific functions. In applications requiring overt visual attention, focusing on visual stimuli with known temporal variation can elicit measurable changes in brain activity. However, elements of BCI applications can be intrusive. This research was designed to determine if Event-Related Potentials (ERPs), to include Steady-State Visually-Evoked Potentials (SSVEPs), could be elicited and interpreted from less obtrusive stimuli. Specifically, this research explores the use of variable frequency and long-wavelength (infrared) stimuli for SSVEP interpretation to explore the application of less obtrusive stimuli for application in BCIs. It was determined …

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Sound Based Positioning, David L. Weathers Mar 2017

Sound Based Positioning, David L. Weathers

Theses and Dissertations

With a growing interest in non-GPS positioning, navigation, and timing (PNT), sound based positioning provides a precise way to locate both sound sources and microphones through audible signals of opportunity (SoOPs). Exploiting SoOPs allows for passive location estimation. But, attributing each signal to a specific source location when signals are simultaneously emitting proves problematic. Using an array of microphones, unique SoOPs are identified and located through steered response beamforming. Sound source signals are then isolated through time-frequency masking to provide clear reference stations by which to estimate the location of a separate microphone through time difference of arrival measurements. Results …

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Recommended Selective Maintenance And Rehabilitation Treatment Approach For Air Force Primary Rigid Runway Pavement Systems, Christopher M. Twigg Mar 2017

Recommended Selective Maintenance And Rehabilitation Treatment Approach For Air Force Primary Rigid Runway Pavement Systems, Christopher M. Twigg

Theses and Dissertations

The Air Force is facing the challenge to preserve the current inventory of 154 million square yards of paved airfield assets while at the same time reducing the budget by $36.2 billion between fiscal years 2015-2019. This research sought to determine a selective maintenance and rehabilitation treatment approach that allocates resources efficiently to preserve the degrading pavement assets in the financially constrained environment. Air Force pavement inspection reports from the past five years provided 4289 observed pavement distress data points for this research. The data was inputted into the pavement management software, PAVER, to calculate the Pavement Condition Index (PCI) …

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Time-Dependent Validation Of Finite Element Strain Distribution Of A Plastically-Deformed Plate Via Digital Image Correlation, Kevin R. Knapp Mar 2017

Time-Dependent Validation Of Finite Element Strain Distribution Of A Plastically-Deformed Plate Via Digital Image Correlation, Kevin R. Knapp

Theses and Dissertations

Generation of residual stress is an essential step in the generation of Goodman data via Air Force Research Laboratory's vibration-based fatigue test. Conventional Goodman data is constructed through uniaxial fatigue testing at a rate of 40 Hz, while the vibration-based testing excites stresses at 1,600 Hz in a stress state that is similar to those seen in gas turbine engine airfoils. A pre-strain procedure is conducted to form residual tensile stress, which serves as a steady stress when the specimen is subjected to fully-reversed vibration-based fatigue loads. This steady tensile stress is desired at the fatigue zone of the test …

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Evaluating The Autonomous Flying Qualities Of A Simulated Variable Stability Aircraft, Ali M. Hamidani Mar 2017

Evaluating The Autonomous Flying Qualities Of A Simulated Variable Stability Aircraft, Ali M. Hamidani

Theses and Dissertations

Delivering communications from high altitudes, at airspeeds of just 30 knots, gathering data from active volcanoes and forming hurricanes, and collecting ISR over hostile territories, UAVs are at the ready to perform those missions that are too dull, dirty, or dangerous for manned aircraft. However, the proliferation of this new technology has its fair share of challenges. Over 460 DoD UAV mishaps have occurred since 2001, with almost half resulting in damages of $2M or more. One incident almost ended in fatalities, when a UAV, suffering from loss of control, collided with a C-130. That loss of control is what …

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Predicting Solar Performance In A Contingency Environment To Meet Net-Zero Facility Power, Anthony D. Williams Mar 2017

Predicting Solar Performance In A Contingency Environment To Meet Net-Zero Facility Power, Anthony D. Williams

Theses and Dissertations

The U.S. government is involved in contingency operations all over the world and these operations require operational support and sustainment in these locations; this includes the reliable delivery of power to base infrastructure. The traditional means of delivering this support requirement in austere environments has been the use of diesel-power generation that has an extensive logistical and economic tail. The research sought out contingency solar applications that may be implemented and operated to offset the facility demand loads in the location to achieve net-zero power. This research explores the technical feasibility of a deployable photovoltaic microgrid to deliver power to …

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Hall Effect Thruster Characterization Through Potential, Magnetic, And Optical Measurements, Nicholas L. Hyatt Mar 2017

Hall Effect Thruster Characterization Through Potential, Magnetic, And Optical Measurements, Nicholas L. Hyatt

Theses and Dissertations

Electric propulsion is a promising method for providing ΔV to spacecraft on orbit. In general, much higher ISPS are obtained compared to their chemical counterparts. Hall thrusters are a subset of electric propulsion with moderately high specific impulse and thrust when compared to other forms of electric propulsion. Even though Hall thrusters have an extensive flight legacy around the world, there are still many unknowns associated with their operation. Experimental research was conducted in AFIT’s Space Propulsion Application Simulation System (SPASS) laboratory, to measure Hall current, plasma potential and visible emission from the 600W Hall thruster in a …

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The Fresnel Zone Light Field Spectral Imager, Francis D. Hallada Mar 2017

The Fresnel Zone Light Field Spectral Imager, Francis D. Hallada

Theses and Dissertations

This thesis provides a computational model and the first experimental demonstration of a Fresnel zone light field spectral imaging (FZLFSI) system. This type of system couples an axial dispersion binary diffractive optic with light field (plenoptic) camera designs providing a snapshot spectral imaging capability. A computational model of the system was developed based on wave optics methods using Fresnel propagation. It was validated experimentally and provides excellent demonstration of system capabilities. The experimentally demonstrated system was able to synthetically refocus monochromatic images across greater than a 100nm bandwidth. Furthermore, the demonstrated system was modeled to have a full range of …

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Common Support Equipment And Its Impact On Aircraft Availability, Jason M. Leighton Mar 2017

Common Support Equipment And Its Impact On Aircraft Availability, Jason M. Leighton

Theses and Dissertations

The ability of military aircraft maintenance personnel to prepare aircraft for flight depends not only on the technical ability and availability of replacement parts, but also on access to serviceable support equipment. While the general relationship between support equipment failures and aircraft availability is understood, the struggle to quantify that relationship makes targeted support equipment replacement or quantity authorization increases difficult. Tight budgets and aging equipment further complicate the task of keeping serviceable support equipment assets in the hands of maintainers. We identify key pieces of support equipment which may affect aircraft availability and other metrics and investigate the associated …

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Defect-Related Optical Absorption Bands In Cdsip2 Crystals, Elizabeth M. Scherrer, Brant T. Kananen, Eric M. Golden, F. Kenneth Hopkins, Kevin T. Zawilski, Peter G. Schunemann, Larry E. Halliburton, Nancy C. Giles Mar 2017

Defect-Related Optical Absorption Bands In Cdsip2 Crystals, Elizabeth M. Scherrer, Brant T. Kananen, Eric M. Golden, F. Kenneth Hopkins, Kevin T. Zawilski, Peter G. Schunemann, Larry E. Halliburton, Nancy C. Giles

Faculty Publications

When used as optical parametric oscillators, CdSiP2 crystals generate tunable output in the mid-infrared. Their performance, however, is often limited by unwanted optical absorption bands that overlap the pump wavelengths. A broad defect-related optical absorption band peaking near 800 nm, with a shoulder near 1 µm, can be photoinduced at room temperature in many CdSiP2 crystals. This absorption band is efficiently produced with 633 nm laser light and decays with a lifetime of ∼0.5 s after removal of the excitation light. The 800 nm band is accompanied by a less intense absorption band peaking near 1.90 µm. Data …

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Method And Apparatus For Singularity Avoidance For Control Moment Gyroscope (Cmg) Systems Without Using Null Motion, Brij N. Agrawal, Jae Jun Kim, Timothy Andrew Sands Feb 2017

Method And Apparatus For Singularity Avoidance For Control Moment Gyroscope (Cmg) Systems Without Using Null Motion, Brij N. Agrawal, Jae Jun Kim, Timothy Andrew Sands

AFIT Patents

A method is described for avoiding gyroscopic singularities during attitude correction to a system, such as a spacecraft having a CMG array. The method receives a corrective torque vector μ and gimbal angle values δ for each of at least three gimbals within the CMG array. The method generates a Jacobian matrix A as a function of gimbal angle values δ. The method calculates a determinant D of Jacobian matrix A. If the determinant is not equal to zero, it is not singular, and the method calculates a gimbal rate {dot over (δ)} using a pseudo-inverse steering law equation. If …

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Climate-Based Policies May Increase Life-Cycle Social Costs Of Vehicle Fleet Operation, Isaac Emery, Eric G.. Mbonimpa, Alfred E. Thal Jr. Feb 2017

Climate-Based Policies May Increase Life-Cycle Social Costs Of Vehicle Fleet Operation, Isaac Emery, Eric G.. Mbonimpa, Alfred E. Thal Jr.

Faculty Publications

No abstract provided.

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Graduate School Of Engineering And Management Catalog 2017-2018, Graduate School Of Engineering And Management, Air Force Institute Of Technology Jan 2017

Graduate School Of Engineering And Management Catalog 2017-2018, Graduate School Of Engineering And Management, Air Force Institute Of Technology

AFIT Documents

The Graduate Catalog represents the offerings, programs, and requirements in effect at the time of publication.

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