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Articles 1 - 30 of 370
Full-Text Articles in Engineering
Terrain Referenced Navigation Using Sift Features In Lidar Range-Based Data, Matthew T. Leines
Terrain Referenced Navigation Using Sift Features In Lidar Range-Based Data, Matthew T. Leines
Theses and Dissertations
The use of GNSS in aiding navigation has become widespread in aircraft. The long term accuracy of INS are enhanced by frequent updates of the highly precise position estimations GNSS provide. Unfortunately, operational environments exist where constant signal or the requisite number of satellites are unavailable, significantly degraded, or intentionally denied. This thesis describes a novel algorithm that uses scanning LiDAR range data, computer vision features, and a reference database to generate aircraft position estimations to update drifting INS estimates. The algorithm uses a single calibrated scanning LiDAR to sample the range and angle to the ground as an aircraft …
Approximate Dynamic Programming For Military Resource Allocation, Carl R. Parson
Approximate Dynamic Programming For Military Resource Allocation, Carl R. Parson
Theses and Dissertations
This research considers the optimal allocation of weapons to a collection of targets with the objective of maximizing the value of destroyed targets. The weapon-target assignment (WTA) problem is a classic non-linear combinatorial optimization problem with an extensive history in operations research literature. The dynamic weapon target assignment (DWTA) problem aims to assign weapons optimally over time using the information gained to improve the outcome of their engagements. This research investigates various formulations of the DWTA problem and develops algorithms for their solution. Finally, an embedded optimization problem is introduced in which optimization of the multi-stage DWTA is used to …
Optimal Collision Avoidance Trajectories For Unmanned/Remotely Piloted Aircraft, Nathan E. Smith
Optimal Collision Avoidance Trajectories For Unmanned/Remotely Piloted Aircraft, Nathan E. Smith
Theses and Dissertations
The post-911 environment has punctuated the force-multiplying capabilities that Remotely Piloted Aircraft (RPA) provides combatant commanders at all echelons on the battlefield. Not only have unmanned aircraft systems made near-revolutionary impacts on the battlefield, their utility and proliferation in law enforcement, homeland security, humanitarian operations, and commercial applications have likewise increased at a rapid rate. As such, under the Federal Aviation Administration (FAA) Modernization and Reform Act of 2012, the United States Congress tasked the FAA to provide for the safe integration of civil unmanned aircraft systems into the national airspace system (NAS) as soon as practicable, but not later …
Multi-Objective Trajectory Optimization Of A Hypersonic Reconnaissance Vehicle With Temperature Constraints, Tadeusz J. Masternak
Multi-Objective Trajectory Optimization Of A Hypersonic Reconnaissance Vehicle With Temperature Constraints, Tadeusz J. Masternak
Theses and Dissertations
Temperature-constrained optimal trajectories for a scramjet-based hypersonic reconnaissance vehicle were generated by developing an optimal control formulation and solving it using a variable order Gauss-Radau quadrature collocation method. The vehicle was assumed to be an air-breathing reconnaissance aircraft that has specified takeoff/landing locations, airborne refueling constraints, specified no-fly zones, and specified targets for sensor data collections. The aircraft model included fight dynamics, aerodynamics, and thermal constraints. This model was incorporated into an optimal control formulation that includes constraints on both the vehicle as well as mission parameters, such as avoidance of no-fly zones and coverage of high-value targets. Optimal trajectories …
Improving Non-Linear Approaches To Anomaly Detection, Class Separation, And Visualization, Todd J. Paciencia
Improving Non-Linear Approaches To Anomaly Detection, Class Separation, And Visualization, Todd J. Paciencia
Theses and Dissertations
Linear approaches for multivariate data analysis are popular due to their lower complexity, reduced computational time, and easier interpretation. In many cases, linear approaches produce adequate results; however, non-linear methods may generate more robust transformations, features, and decision boundaries. Of course, these nonlinear methods present their own unique challenges that often inhibit their use. In this research, improvements to existing non-linear techniques are investigated for the purposes of providing better, timely class separation and improved anomaly detection on various multivariate datasets, culminating in application to anomaly detection in hyperspectral imagery. Primarily, kernel-based methods are investigated, with some consideration towards other …
Exploring Individual Differences In Workload Assessment, Danielle K. Boeke
Exploring Individual Differences In Workload Assessment, Danielle K. Boeke
Theses and Dissertations
Air Force missions continue to increase in complexity often imposing higher levels of task load from cognitive tasks on the operators. This increased task load manifests itself in increased cognitive workload and potentially derogated performance. While cognitive workload has been studied for decades, recent advances in objective workload models and physiology monitoring have the potential to provide a more robust understanding of workload, potentially allowing systems to adaptively employ automation to maintain operator peak performance. The current research sought to provide insight into the relationship between subjective workload, task performance, objective workload, and select physiology measures. Analysis of an existing …
A Decision Analysis Framework For Evaluation Of Helmet Mounted Display Alternatives For Fighter Aircraft, Matthew R. Dansereau
A Decision Analysis Framework For Evaluation Of Helmet Mounted Display Alternatives For Fighter Aircraft, Matthew R. Dansereau
Theses and Dissertations
The promise of providing an intuitive and efficient information interface, while allowing the warfighter to perform other critical tasks such as targeting or aircraft control, has led to the growing popularity of Helmet Mounted Displays (HMDs) across the military landscape, especially combat aircraft. Though design and selection of competing systems is critical to optimized performance and safety, structured methods for the evaluation of HMDs are not often used in the acquisition community, leaving selection among alternative designs to the judgment of subject matter experts. However, technical decision-making has been shown to be flawed without the use of a structured decision …
Characterizing And Managing Intrusion Detection System (Ids) Alerts With Multi-Server/Multi-Priority Queuing Theory, Christopher C. Olsen
Characterizing And Managing Intrusion Detection System (Ids) Alerts With Multi-Server/Multi-Priority Queuing Theory, Christopher C. Olsen
Theses and Dissertations
The DoD sets forth an objective to employ an active cyber defense capability to prevent intrusions onto DoD networks and systems. Intrusion Detection Systems (IDS) are a critical part of network defense architectures, but their alerts can be difficult to manage. This research applies Queuing Theory to the management of IDS alerts, seeking to answer how analysts and priority schemes effect alert processing performance. To characterize the effect of these two variables on queue wait times, a MATLAB simulation was developed to allow parametric analysis under two scenarios. The first varies the number of analysts and the second varies the …
Hot Streak Characterization In Serpentine Exhaust Nozzles, Darrell S. Crowe
Hot Streak Characterization In Serpentine Exhaust Nozzles, Darrell S. Crowe
Theses and Dissertations
Modern aircraft of the United States Air Force face increasingly demanding cost, weight, and survivability requirements. Serpentine exhaust nozzles within an embedded engine allow a weapon system to fulfill mission survivability requirements by providing denial of direct line-of-sight into the high-temperature components of the engine. Recently, aircraft have experienced material degradation and failure along the aft deck due to extreme thermal loading. Failure has occurred in specific regions along the aft deck where concentrations of hot gas have come in contact with the surface causing hot streaks. The prevention of these failures will be aided by the accurate prediction of …
Cloud-Induced Uncertainty For Visual Navigation, Alyssa N. Gutierrez
Cloud-Induced Uncertainty For Visual Navigation, Alyssa N. Gutierrez
Theses and Dissertations
This research addresses the numerical distortion of features due to the presence of clouds in an image. The research aims to quantify the probability of a mismatch between two features in a single image, which will describe the likelihood that a visual navigation system incorrectly tracks a feature throughout an image sequence, leading to position miscalculations. First, an algorithm is developed for calculating transparency of clouds in images at the pixel level. The algorithm determines transparency based on the distance between each pixel color and the average pixel color of the clouds. The algorithm is used to create a dataset …
Surface Modification Of Nanoplatelets In Polymer Nanocomposites, Shailesh K. Shori
Surface Modification Of Nanoplatelets In Polymer Nanocomposites, Shailesh K. Shori
Theses and Dissertations
In polymer nanocomposites (PNCs), it is very important that the nanofiller (typically an inorganic) is well-dispersed in an organic polymer matrix. Optimal compatibility results in end-use products such as packaging materials with enhanced properties. In practice, however, this is challenging to achieve because “ideal” dispersions require the complete uniform separation, termed exfoliation, of the nanofiller within the matrix. As a result, different nanofillers including calcium niobate (CN) and montmorillonite (MMT) are first studied for their ability to exfoliate in aqueous suspensions by measuring the organic cation uptake. The cation exchange capacity, or CEC, determined that CN needs further work before …
Synthesis Of Au And Ag Catalysts With Controlled Sizes Of Metal Particles, Eleni A. Kyriakidou
Synthesis Of Au And Ag Catalysts With Controlled Sizes Of Metal Particles, Eleni A. Kyriakidou
Theses and Dissertations
The performance of supported metal catalysts largely depends on the structure and composition of the metal particles and the nature of the support. In order to achieve better control over these parameters, synthetic route based on the use of templating agents has been proposed. Among the different templating agents, poly(amidoamine) (PAMAM) dendrimers have attracted a lot of recent attention as nanoparticle stabilizers. In this thesis, Au/G4OH nanocomposites were synthesized in aqueous solutions and used as precursors for the preparation of SiO2-supported Au nanoparticles. Elemental analysis, UV-Vis, and STEM measurements were used to estimate the extent of the Au-dendrimer interactions and …
Application Of Various Adsorbents To Remove Micro-Pollutants In Aquatic System, Chanil Jung
Application Of Various Adsorbents To Remove Micro-Pollutants In Aquatic System, Chanil Jung
Theses and Dissertations
Untreated or insufficiently treated pharmaceuticals and endocrine disrupting compounds (EDCs) as well as heavy metals have influenced the ecosystem and their exposures in the water system have threatened human health; causing cancers and adverse health effect to immune system. While various water treatment techniques have been applied to solve this problem, adsorption has been considered as one of the most efficient and manageable water purification techniques. Advanced analysis methods for aqueous contaminants have improved comprehension, allowing proficiency about the fate of trace leveled emerging contaminants, thus allowed to reveal the adsorption mechanisms of each pollutant. This dissertation focuses on the …
Advanced Digital Signal Processing Based Redefined Power Quality Indices, And Their Applications To Wind Power, Md Moinul Islam
Advanced Digital Signal Processing Based Redefined Power Quality Indices, And Their Applications To Wind Power, Md Moinul Islam
Theses and Dissertations
This dissertation proposes a time-frequency distribution (TFD) based new method to redefine the power quality (PQ) indices for the assessment of PQ disturbances typically present in electric power systems. The redefined PQ indices are applied to various types of synthetic and real-world PQ disturbances in order to verify the efficacy and applicability of the proposed method. The case studies show that the proposed method provides actual results with respect to the existing TFD-based transient PQ indices, and provides much more accurate results than the traditional fast Fourier transform (FFT) based PQ indices under stationary and nonstationary PQ disturbances. In addition, …
Quantifying Individual Losses In A Direct Methanol Fuel Cell, Jennifer Rae Ruffing
Quantifying Individual Losses In A Direct Methanol Fuel Cell, Jennifer Rae Ruffing
Theses and Dissertations
The performance of a direct methanol fuel cell (DMFC) is complicated due to the complex interactions of kinetic and transport processes. As a result, changes in one aspect of the cell have consequences in other aspects, which are difficult to elucidate from the full-cell polarization (i.e. voltage vs. current) behavior that fuel cell researchers often use to characterize the performance of their systems. The objective of this work was to develop a strategy to use current and voltage relationships from anode half cells, cathode half-cells, and a hydrogen pump, coupled with methanol crossover data and a mathematical model, to quantify …
On The Development Of High Strain Rate Experiments For The Characterization Of Engineering Materials, Silas P. Mallon
On The Development Of High Strain Rate Experiments For The Characterization Of Engineering Materials, Silas P. Mallon
Theses and Dissertations
In order to predict the damage accumulation and failure processes associated with highly dynamic events such as blast loading, shock wave loading, and ballistic impact loading, a commensurate understanding of the fundamental constitutive and fracture behavior of materials subjected to such high rate loading conditions is necessary. In this effort, high strain rate experimental facilities consisting of a shock tube apparatus and a torsional split Hopkinson bar apparatus have been designed, constructed, and subsequently used to investigate the mechanical properties of an array of engineering materials subjected to a variety of dynamic loading conditions. Designs for the experimental equipment utilized …
High-Performance Meta-Genomic Gene Identification, Ibrahim Savran
High-Performance Meta-Genomic Gene Identification, Ibrahim Savran
Theses and Dissertations
Computational Genomics, or Computational Genetics, refers to the use of computational and statistical analysis for understanding the structure and the function of genetic material in organisms. The primary focus of research in computational genomics in the past three decades has been the understanding of genomes and their functional elements by analyzing biological sequence data. The high demand for low-cost sequencing has driven the development of highthroughput sequencing technologies, next-generation sequencing (NGS), that parallelize the sequencing process, producing thousands or millions of sequences concurrently. Moore’s Law is the observation that the number of transistors on integrated circuits doubles approximately every two …
Low Reynolds Number Turbulence: Mechanisms And Applications, Wei Zhao
Low Reynolds Number Turbulence: Mechanisms And Applications, Wei Zhao
Theses and Dissertations
Turbulence, as one of "the most important unsolved classical problem in physics" (R. Feynman, 1932), has been investigated for more than 130 years. Conventionally, turbulence is believed to be a phenomenon of high Reynolds numbers (Re). However, we find that turbulence can also be achieved at low Re by proper external forcing, either in macroflows or in microflows. In macroflows, the characteristics of high Re turbulence can be achieved in confined flows, when the bulk flow Re is around 400, by external forcing at its optimal frequency (Wang 2003; Wang 2006). Interestingly, the optimal narrow band of frequency is fixed …
Quantitative Comparison Of Time-Frequency Decomposed Gait Emg Signals, L. Patrick Mitchell
Quantitative Comparison Of Time-Frequency Decomposed Gait Emg Signals, L. Patrick Mitchell
Theses and Dissertations
Falls in the senior population represent an immediate threat to both current and future generations’ quality of life. The results of falls can be disastrous, create a long road to recovery, and in many cases result in death. Hypertension represents a difficult-to-quantify condition which is known to contribute to gait and balance dysfunction. Accurate assessment of conditions such as these represents an area of primary investigative need. In order to meet this need, a new experimental setup is developed which combines time-frequency analysis with surface electromyography (sEMG) signals obtained during ambulation. 3-bit pressure data is acquired using a pressure-sensitive mat, …
An Engineering Approach For The Design Of Archaeological Reburial Systems, Angel Ari Perez Mejia
An Engineering Approach For The Design Of Archaeological Reburial Systems, Angel Ari Perez Mejia
Theses and Dissertations
Archaeological sites are a non-renewable resource which is often our only link to the past. However, sites are under constant threat of destruction due to construction activities. Civil engineers and archaeologists must the work together to ensure both the continued survival of archaeological sites while allowing for development to continue. Reburial systems, when properly designed and constructed, allow for the protection of archaeological sites while allowing the continued use of the land. However, because reburial as an intentional conservation technique is relatively modern, practice is fragmented and there are no universally accepted guidelines. Current reburial system design relies on prescriptive …
Cost Avoidance Analysis Of Military Aircraft Components Utilizing Condition-Based Maintenance Practices, Erin Ballentine
Cost Avoidance Analysis Of Military Aircraft Components Utilizing Condition-Based Maintenance Practices, Erin Ballentine
Theses and Dissertations
This research involves two major case studies. Both look at the current maintenance practices done by the United States Army and propose a solution for improvement utilizing condition-based maintenance (CBM) practices. Each study details a cost avoidance that can be earned by implementing the solutions and the resulting benefits that can be experienced. Case Study I is a return on investment (ROI) that analyzes the benefits of the implementation of elastomeric wedges as vibration control on the Apache (AH-64D) aircraft. Analysis of the material and operational costs shows that the use of self-adhering elastomeric trailing edge wedges on the Apache …
Slow Wave Structures Integrated With Ferro-Magnetic And Ferro-Electric Thin Films For Smart Rf Applications, B M Farid Rahman
Slow Wave Structures Integrated With Ferro-Magnetic And Ferro-Electric Thin Films For Smart Rf Applications, B M Farid Rahman
Theses and Dissertations
Modern communications systems are following a common trend to increase the operational frequency, level of integration and number of frequency bands. Although 90-95% components in a cell phone are passives which take 80% of the total board area. High performance RF passive components play limited role and are desired towards this technological advancement. Slow wave structure is one of the most promising candidates to design compact RF and mm-Wave passive components. Slow wave structures are the specially designed transmission line realized by placing the alternate narrow and wide signal conductors in order to reduce the physical size of the components. …
Functionalized Graphitic Nanoreinforcement For Cement Composites, Nima Zohhadi
Functionalized Graphitic Nanoreinforcement For Cement Composites, Nima Zohhadi
Theses and Dissertations
Physical and mechanical properties of graphitic nanomaterials, in particular multiwalled carbon nanotubes (MWCNTs) and graphene nano-platelets (GNPs) make them promising candidates for nanoreinforcement of cement composites. The two key challenges associated with the incorporation of MWCNTs and GNPs are to attain uniform dispersion and interfacial bonding within the composite matrix. The effects of three main-stream dispersion techniques (namely, ultrasonication, acid-etching, and surfactant-coating) on the mechanical properties and microstructure of MWCNT- and GNP-cement composites were experimentally studied. Compressive strength tests and different characterization techniques including dynamic light scattering, Raman spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission …
Finite Element Analysis Simulations Of Micro And Nano-Electromechanical Sensors For Design Optimization, Nicholas Frank Deroller
Finite Element Analysis Simulations Of Micro And Nano-Electromechanical Sensors For Design Optimization, Nicholas Frank Deroller
Theses and Dissertations
Micro and Nano-electromechanical sensors (MEMS and NEMS) provide a means of actively sensing minute changes in the surrounding environment. Small changes in temperature, momentum, and strain may be sensed in passive modes while greater sensing possibilities exist in active modes. Theoretical femto-gram resolution mass detection and heated element sensing methods may be used while volatile organic compound (VOC) sensing may be achieved when combined with a functionalization layer or device heating. These devices offer a great reduction in cost and offer increased mobility by allowing a "lab-on-chip" solution for the prospective user while also greatly reducing the amount of energy …
Influence Of Defects In Epitaxial Graphene Towards Material Growth And Device Performances, Shamaita Shithi Shetu
Influence Of Defects In Epitaxial Graphene Towards Material Growth And Device Performances, Shamaita Shithi Shetu
Theses and Dissertations
Since its invention in 2004, Graphene, a two dimensional array of SP2 bonded carbon atoms has received significant interest by the scientific community due to its unique electrical, optical and mechanical properties. A promising route to the synthesis of large-area graphene, is epitaxial graphene formed by sublimation of silicon atoms from Silicon carbide at elevated temperatures (>1200oC). Although the electronic and mechanical properties of graphene with perfect atomic lattice are outstanding, the structural defects, which may appear during graphene growth, can influence the growth mechanism and material properties. However, deviations from perfection, i.e. introducing dopants in semiconductors often considered …
High Level Control Implementation For A Residential Smart Grid Power System, Hang Xu
High Level Control Implementation For A Residential Smart Grid Power System, Hang Xu
Theses and Dissertations
With the environment protection and energy usage efficiency promotion issues concerned more and more by governments and industries these days, smart grid technologies have been in rapid development. On this new technology stage, residential site power management system has become a star. This paper introduces the concept, development of two high level control methods for “Smart Green Power Node” (SGPN), solutions of demand side energy management system. One control algorithm is optimal model method which uses the predictive data of a battery model with electrical parameters and pricing methods, to keep scheduling the optimal control input on the receding time …
Fabrication And Characterization Of Novel Electrodes For Solid Oxide Fuel Cell For Efficient Energy Conversion, Yu Chen
Theses and Dissertations
Solid oxide fuel cells (SOFCs) have been considered as one of the most promising technologies for future energy conversion since they can in principle be operated with fuels ranging from H2 to any hydrocarbon fuel. However, the system cost and coking (when using hydrocarbon as fuel) issues for the state-of-art electrode materials/designs often limit their further application. The objective of this Ph.D dissertation is aiming at overcoming these problems and accelerating SOFC commercialization. One approach to cost reduction is lowering the SOFC operating temperature to below 800 or even 600 oC, so that inexpensive materials can be used and quick …
Characterization Of Electrodeposited Copper Foil Surface Roughness For Accurate Conductor Power Loss Modeling, Michael B. Griesi
Characterization Of Electrodeposited Copper Foil Surface Roughness For Accurate Conductor Power Loss Modeling, Michael B. Griesi
Theses and Dissertations
As computer data rates have increased, designers observed that the standard models for estimating the impact of copper foil surface roughness on conductor loss are limited to a few GHz. The more recent snowball model (a “snowball” estimation of the Huray Model) has demonstrated improved conductor loss predictions up to 50 GHz by estimating the necessary parameters using reasonable assumptions about the geometric surface features of electrodeposited copper foil. Since then, the Huray Model has been incorporated into commercial electromagnetic field simulators. However, a standard method of characterizing the electrodeposited copper foil used in high-speed circuits to directly implement the …
Piezotransistive Iii-V Nitride Microcantilever Based Mems/Nems Sensor For Photoacoustic Spectroscopy Of Chemicals, Abdul Hafiz Ibne Talukdar
Piezotransistive Iii-V Nitride Microcantilever Based Mems/Nems Sensor For Photoacoustic Spectroscopy Of Chemicals, Abdul Hafiz Ibne Talukdar
Theses and Dissertations
Microcantilevers are highly attractive as transducers for detecting chemicals, explosives, and biological molecules due to their high sensitivity, micro-scale dimensions, and low power consumption. Though optical transduction of the mechanical movement of the microcantilevers into an electrical signal is widely practiced, there is a continuous thrust to develop alternative transduction methods that are more conducive to the development of compact miniaturized sensors. Piezoelectric and piezoresistive transduction methods are two of the most popular ones that have been utilized to develop miniaturized sensor systems. Piezoelectric cantilevers, which are commonly made of PZT film, have demonstrated very high sensitivity; however, they suffer …
Comprehensive Joint Time-Frequency Analysis Toward Condition Based Maintenance Regimes For Electrical And Mechanical Components, David Lee Coats
Comprehensive Joint Time-Frequency Analysis Toward Condition Based Maintenance Regimes For Electrical And Mechanical Components, David Lee Coats
Theses and Dissertations
Based upon a framework of time-frequency analysis, we outline condition based maintenance (CBM), or maintenance only upon evidence of need, for both electrical and mechanical systems. We apply novel time-frequency cross-correlation metrics to helicopter drivetrain systems and electrical cables as remaining useful life assessments by non-destructive and non-invasive tests. In both cases, these metrics for health assessment provide a basis for diagnostic and prognostic analysis of underlying systems and components by performing accelerated condition tests on actual mechanical and electrical systems. We present novel time-frequency domain vibration analysis of a gearbox failure in an AH-64 Apache drivetrain testbed and quantify …