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Articles 391 - 420 of 3445

Full-Text Articles in Engineering

Ab Initio Modeling Of An Electron Transport Layer Interface In Hybrid Perovskite Solar Cells, Krantikumar Subhash Pawar Jan 2020

Ab Initio Modeling Of An Electron Transport Layer Interface In Hybrid Perovskite Solar Cells, Krantikumar Subhash Pawar

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Hybrid organic-inorganic perovskite solar cell is an emerging technology which has shown the fastest advancement in power conversion efficiency within a few years since introduction, thus making it one of the clean energy breakthroughs. These cells are based on thin-film technology which makes them suitable to manufacture using low-cost solution processing methods. As these types of cells are easily tunable with the selection of different materials, interfacial engineering is an important approach to increasing their efficiency. One of the main hurdles in this regard is the loss caused by the recombination of separated charges. An approach to tackle these issues …

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Extracting Information From Subroutines Using Static Analysis Semantics, Luke A. Burnett Jan 2020

Extracting Information From Subroutines Using Static Analysis Semantics, Luke A. Burnett

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Understanding how a system component can interact with other services can take an immeasurable amount of time. Reverse engineering embedded and large systems can rely on understanding how components interact with one another. This process is time consuming and can sometimes be generalized through certain behavior.We will be explaining two such complicated systems and highlighting similarities between them. We will show that through static analysis you can capture compiler behavior and apply it to the understanding of a function, reducing the total time required to understand a component of whichever system you are learning.

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Predicting Subjective Sleep Quality Using Objective Measurements In Older Adults, Reza Sadeghi Jan 2020

Predicting Subjective Sleep Quality Using Objective Measurements In Older Adults, Reza Sadeghi

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Humans spend almost a third of their lives asleep. Sleep has a pivotal effect on job performance, memory, fatigue recovery, and both mental and physical health. Sleep quality (SQ) is a subjective experience and reported via patients’ self-reports. Predicting subjective SQ based on objective measurements can enhance diagnosis and treatment of SQ defects, especially in older adults who are subject to poor SQ. In this dissertation, we assessed enhancement of subjective SQ prediction using an easy-to-use E4 wearable device, machine learning techniques and identifying disease-specific risk factors of abnormal SQ in older adults. First, we designed a clinical decision support …

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Identifying Knowledge Gaps Using A Graph-Based Knowledge Representation, Daniel P. Schmidt Jan 2020

Identifying Knowledge Gaps Using A Graph-Based Knowledge Representation, Daniel P. Schmidt

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Knowledge integration and knowledge bases are becoming more and more prevalent in the systems we use every day. When developing these knowledge bases, it is important to ensure the correctness of the information upon entry, as well as allow queries of all sorts; for this, understanding where the gaps in knowledge can arise is critical. This thesis proposes a descriptive taxonomy of knowledge gaps, along with a framework for automated detection and resolution of some of those gaps. Additionally, the effectiveness of this framework is evaluated in terms of successful responses to queries on a knowledge base constructed from a …

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Eye-Tracking To Evaluate Trust In Human-Atr Interaction, Samuel Francis Adelman Jan 2020

Eye-Tracking To Evaluate Trust In Human-Atr Interaction, Samuel Francis Adelman

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Human collaboration with targeting aids have allowed analysts to achieve a greater level of coordination and productivity in a variety of fields. This project investigates the impact that an Assisted Target Recognition (ATR) algorithm’s false alarm rate and the task Target of Interest (TOI) level has on user-system trust and use in a targeting decision task. Previous studies suggest that an increased number of false alarms in an ATR task negatively impacts analyst trust in the system. This study will further contribute to this research, aiming to provide a better framework for appropriate tolerance levels within ATR algorithms, utilizing pre-truthed …

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Single-Pixel Camera Based Spatial Frequency Domain Imaging For Non-Contact Tissue Characterization, Alec M. Petrack Jan 2020

Single-Pixel Camera Based Spatial Frequency Domain Imaging For Non-Contact Tissue Characterization, Alec M. Petrack

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Optical imaging has demonstrated potential as a medical imaging modality for measuring tissue functionality. Recently, interest in fluorescence guided surgery has emerged from improvements in optical imaging that have allowed real-time feedback. Of the optical imaging modalities, spatial frequency domain imaging (SFDI) has gained a lot of interest. Unlike spectroscopic techniques, such as functional near infrared spectroscopy (fNIRS) and frequency domain spectroscopy that measure bulk tissue properties, SFDI quantifies tissue functionality locally and wide field making it practical for clinical applications. Unfortunately, traditional SFDI systems use multi-pixel detectors, which may not exhibit ideal spectral characteristics, have limited sensitivity, be expensive, …

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An Approach To Cluster And Benchmark Regional Emergency Medical Service Agencies, Swetha Kondapalli Jan 2020

An Approach To Cluster And Benchmark Regional Emergency Medical Service Agencies, Swetha Kondapalli

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Emergency Medical Service (EMS) providers are the first responders for an injured patient on the field. Their assessment of patient injuries and determination of an appropriate hospital play a critical role in patient outcomes. A majority of states in the US have established a state-level governing body (e.g., EMS Division) that is responsible for developing and maintaining a robust EMS system throughout the state. Such divisions develop standards, accredit EMS agencies, oversee the trauma system, and support new initiatives through grants and training. But to do so, these divisions require data to enable them to first understand the similarities between …

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Metal Coupon Testing In An Axial Rotating Detonation Engine For Wear Characterization, Gary S. North Jan 2020

Metal Coupon Testing In An Axial Rotating Detonation Engine For Wear Characterization, Gary S. North

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Rotating Detonation Engines (RDE) are being explored as a possible way to get better fuel efficiency for turbine engines than is otherwise possible. The walls of the RDE are subjected to cyclic thermal and mechanical shock loading at rates of approximately 3 KHz, with gas temperatures as high as 2976 K. This project performed testing with Inconel 625 and 304 stainless steel coupons in an RDE outer body to attempt to measure material ablation rates. Significant microstructural changes were observed to include grain growth in both alloys, carbide formation and grain boundary melting in Inconel, and formation of delta ferrite …

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Primary Processing Parameters And Their Influence On Porosity And Fatigue Life Of Additively Manufactured Alloy 718, Luke C. Sheridan Jan 2020

Primary Processing Parameters And Their Influence On Porosity And Fatigue Life Of Additively Manufactured Alloy 718, Luke C. Sheridan

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In many structural applications void-like defects cause significant performance debits which call for component redesign or post-processing to account for or remove the defects. For laser powder bed fusion (LPBF) processes, it has been shown that many of these features and their size and shape characteristics are controllable through LPBF process parameter manipulation. For design efforts, however, it is necessary to understand the direct influences of processing on the formation of porosity and the role that individual pores and porosity distributions have on the properties and performance of AM components. Additionally, design criteria must be established to facilitate implementation of …

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Defect Modeling And Vibration-Based Bending Fatigue Of Additively Manufactured Inconel 718, Wesley Earl Eldt Jan 2020

Defect Modeling And Vibration-Based Bending Fatigue Of Additively Manufactured Inconel 718, Wesley Earl Eldt

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Additive manufacturing (AM) is convenient for building components with complex features. However, the long-term integrity of these components is uncertain, since AM parts have defects such as pores and rough surfaces. In this work, an analytical model was developed to determine the impact of defects, and a novel bending fatigue test was used to determine the fatigue life of channeled specimens. The analytical model, based off the theory of critical distances, investigates coupled pores and predicts their potential for fatigue failure. This resulted in a maximum allowable pore size and spacing recommendation for coupled defects. Additionally, specimens with through channels …

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Hierarchical Hybrid Materials From Flexible Fabric Substrates, Wenhu Wang Jan 2020

Hierarchical Hybrid Materials From Flexible Fabric Substrates, Wenhu Wang

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The goal of this project is to investigate fabrication approaches and structure-property relationships of porous and flexible hierarchical hybrid solids suitable for advanced surface-active devices. Multi-scale hierarchical carbon materials are being fabricated by strong covalent attachment of multiwall carbon nanotube(MWCNTs) arrays on flexible carbon fabric substrates in order to enhance the surface area per unit volume. This was done using chemical vapor deposition (CVD) after functionalizing the surface with a plasma-derived nano-oxide coating. Structural and chemical characterization is performed using scanning electron microscope(SEM), energy dispersive spectroscopy(EDS) and x-ray photoelectron spectroscopy(XPS). Surface area estimates have been made by building structural models …

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Stream Clustering And Visualization Of Geotagged Text Data For Crisis Management, Nathaniel C. Crossman Jan 2020

Stream Clustering And Visualization Of Geotagged Text Data For Crisis Management, Nathaniel C. Crossman

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In the last decade, the advent of social media and microblogging services have inevitably changed our world. These services produce vast amounts of streaming data, and one of the most important ways of analyzing and discovering interesting trends in the streaming data is through clustering. In clustering streaming data, it is desirable to perform a single pass over incoming data, such that we do not need to process old data again, and the clustering model should evolve over time not to lose any important feature statistics of the data. In this research, we have developed a new clustering system that …

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Optimization Study Of A Combined Wind-Solar Farm For A Specified Demand, Venkat Siddhartha Rama Jan 2020

Optimization Study Of A Combined Wind-Solar Farm For A Specified Demand, Venkat Siddhartha Rama

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At the present time, using wind and solar energy for producing electricity in the United States is becoming cost competitive. According to Lazard’s 2019 [36] levelized cost of energy (LCOE) analysis of a number of energy sources used for producing electricity in the United States, wind and solar are cheaper than natural gas and coal. While capital, maintenance, operation, and fuel costs are included in LCOE numbers, energy source intermittency is not. Intermittency is an important issue with wind and solar energy sources, but not with natural gas or coal energy sources. Combining wind and solar energy sources into one …

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Design And Simulation Of Boost Dc - Dc Pulse Width Modulator (Pwm) Feed-Forward Control Converter, Calenia L. Franklin Jan 2020

Design And Simulation Of Boost Dc - Dc Pulse Width Modulator (Pwm) Feed-Forward Control Converter, Calenia L. Franklin

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Military aircraft systems’ power losses are occurring during the loading operations; loading and unloading causes the aircraft systems to lose power. The primary aircraft power source is provided by a 400Hz Ground Power Units (GPU). This GPU provides power to interior lighting, the aircraft cargo compartment, and other electrical systems (i.e. bus). The issues are during loading and unloading on the aircraft, which causes dropout of aircraft power supplied by the external 400Hz GPU. The majority of the military aircraft require a high voltage and a high current with a 270V power output. This thesis analyzes using Feed-Forward PWM Boost …

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Visual Sampling With The Eeg Alpha Oscillation, Kevin Eugene Alexander Jan 2020

Visual Sampling With The Eeg Alpha Oscillation, Kevin Eugene Alexander

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The posterior alpha rhythm, seen in human electroencephalograms (EEG), is posited to originate from cycling inhibitory/excitatory states of visual relay cells in the thalamus, which could result in discrete sampling of visual information. Here, we tested this hypothesis by presenting light flashes at perceptual threshold intensity through closed eyelids to 20 participants during times of spontaneous alpha oscillations. Alpha phase and amplitude were calculated relative to each individual’s retina-to-V1 conduction delay, estimated by the individuals’ C1 visual-evoked potential latency. Our results show that an additional 20.96% of stimuli are observed when afferenting at V1 during an alpha wave trough (272.41°) …

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An Adversarial Framework For Deep 3d Target Template Generation, Walter E. Waldow Jan 2020

An Adversarial Framework For Deep 3d Target Template Generation, Walter E. Waldow

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This paper presents a framework for the generation of 3D models. This is an important problem for many reasons. For example, 3D models are important for systems that are involved in target recognition. These systems use 3D models to train up accuracy on identifying real world object. Traditional means of gathering 3D models have limitations that the generation of 3D models can help overcome. The framework uses a novel generative adversarial network (GAN) that learns latent representations of two dimensional views of a model to bootstrap the network’s ability to learn to generate three dimensional objects. The novel architecture is …

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Additive Manufacturing Techniques To Enhance The Performance Of Electronics Created On Flexible And Rigid Substrates, Aamir Hamed Hamad Jan 2020

Additive Manufacturing Techniques To Enhance The Performance Of Electronics Created On Flexible And Rigid Substrates, Aamir Hamed Hamad

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Different additive manufacturing (AM) methods including fused deposition modeling (FDM) and piezoelectrical drop on demand (DOD) inkjet printing have been used in printed electronics for easy production, easy integration, better performance, and low cost. These methods have been used in producing everyday smart printed electronics such as conformal antennas (planner and non-planar antennas), sensors, actuators, and solar cells created on flexible and rigid substrates. The performance of printed electronics strongly depends on printing techniques and printing resolution that enhance their electrical and mechanical properties. In this dissertation, 3D and surface printing techniques were used to enhance the performance of printed …

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Adaptive Multi-Fidelity Modeling For Efficient Design Exploration Under Uncertainty, Atticus J. Beachy Jan 2020

Adaptive Multi-Fidelity Modeling For Efficient Design Exploration Under Uncertainty, Atticus J. Beachy

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This thesis work introduces a novel multi-fidelity modeling framework, which is designed to address the practical challenges encountered in Aerospace vehicle design when 1) multiple low-fidelity models exist, 2) each low-fidelity model may only be correlated with the high-fidelity model in part of the design domain, and 3) models may contain noise or uncertainty. The proposed approach approximates a high-fidelity model by consolidating multiple low-fidelity models using the localized Galerkin formulation. Also, two adaptive sampling methods are developed to efficiently construct an accurate model. The first acquisition formulation, expected effectiveness, searches for the global optimum and is useful for modeling …

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Correlating In-Situ Monitoring Data With Internal Defects In Laser Powder Bed Fusion Additive Manufacturing, Andrew J. Harvey Jan 2020

Correlating In-Situ Monitoring Data With Internal Defects In Laser Powder Bed Fusion Additive Manufacturing, Andrew J. Harvey

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The presence of defects within laser powder bed fusion (LPBF) parts can lead to reduced mechanical properties and life of components. Because of this, the ability to detect these defects within the parts is critical before the part is subject to its intended loading. Normally the parts are subjected to a quality analysis once they are completed however, this process is typically expensive and time consuming. A solution for these problems is to sense the creation of defects and pores in the parts in-situ, while the part is being fabricated. One proposed method of in-situ monitoring is visible spectroscopy to …

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Analytical Approach To Multi-Objective Joint Inference Control For Fixed Wing Unmanned Aerial Vehicles, Julian L. Casey Jan 2020

Analytical Approach To Multi-Objective Joint Inference Control For Fixed Wing Unmanned Aerial Vehicles, Julian L. Casey

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Fixed-wing Unmanned Aerial Vehicles (UAVs) have been found highly useful in various environments, including military and law enforcement. With the increased use of fixed-wing UAVs, there becomes an increased need to optimize the resources available. One approach to resource management is to create multi-objective flights. This thesis presents the design, analysis, and experimental implementation of multi-objective resource management for the resource of Range, distance available to the UAV, from the viewpoint of Intelligence Surveillance and Reconnaissance (ISR). First, a Simulation Environment is created capable of tracking multiple fixed-wing UAVs and to allow for the UAVs’ being controlled by an externally …

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Processing And Properties Of Multifunctional Two Dimensional Nanocomposites Based On Graphene Nano-Flakes, Mohammed K. Mohammed Jan 2020

Processing And Properties Of Multifunctional Two Dimensional Nanocomposites Based On Graphene Nano-Flakes, Mohammed K. Mohammed

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The unique properties of graphene have directed researchers to study and characterize this new material. Graphene production and graphene based materials have been widely explored and developed in the past decade. Most research has aimed at developing scalable, environmentally friendly, and cheap procedures to produce defect-free graphene that can be used in various applications such as mechanical properties enhancement and multifunctional material. The challenge is processing such material on a scale suitable for engineering applications such as advanced photonics and advanced electronics. In this study, we investigate a new processing technique based on Langmuir-Blodgett (LB) Technique. We managed to produce …

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Quantitative Susceptibility Mapping (Qsm) Reconstruction From Mri Phase Data, Sara Gharabaghi Jan 2020

Quantitative Susceptibility Mapping (Qsm) Reconstruction From Mri Phase Data, Sara Gharabaghi

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Quantitative susceptibility mapping (QSM) is a powerful technique that reveals changes in the underlying tissue susceptibility distribution. It can be used to measure the concentrations of iron and calcium in the brain both of which are linked with numerous neurodegenerative diseases. However, reconstructing the QSM image from the MRI phase data is an ill-posed inverse problem. Different methods have been proposed to overcome this difficulty. Still, the reconstructed QSM images suffer from streaking artifacts and underestimate the measured susceptibility of deep gray matter, veins, and other high susceptibility regions. This thesis proposes a structurally constrained Susceptibility Weighted Imaging and Mapping …

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Stabilization Of Β-Cristobalite In The Sio2-Alpo4-Bpo4 System, Kathryn Doyle Jan 2020

Stabilization Of Β-Cristobalite In The Sio2-Alpo4-Bpo4 System, Kathryn Doyle

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Fused silica (silica glass) is transparent in the optical and near-infrared and has a low dielectric constant, making it suitable as a window material for radio frequency radiation. However, at high temperatures (>1100C), fused silica will easily creep and lose dimensional stability. Crystallized silica is much more creep resistant than fused silica. Silica crystallizes to many different structures including quartz, tridymite, and α- and β cristobalite. The only cubic polymorph, which is suitable for both optical and radio frequency transmission in polycrystalline form, is β -cristobalite. Unfortunately, this polymorph transforms to α-cristobalite at ~300C, and the volume change during …

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Hierarchical Structure, Properties And Bone Mechanics At Macro, Micro, And Nano Levels, Farah Mohammed Ridha Abdulateef Hamandi Jan 2020

Hierarchical Structure, Properties And Bone Mechanics At Macro, Micro, And Nano Levels, Farah Mohammed Ridha Abdulateef Hamandi

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This research focuses on the hierarchical structure of bone and associated mechanical properties at different scales to assess damage accumulation leading to premature failure, with or without instrumentation. In this work, an attempt was made to develop a framework of macro, micro, and nano damage accumulation models and implementing them to derive mechanical behavior of the bone. At macrolevel, retrospective evaluation of 313 subjects was conducted, and the damage of bone tissue was investigated with respect to subject demography including age, gender, race, body mass index (BMI), height and weight, and their role in initiating fracture. Experimental data utilized 28 …

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Developing Equivalent Solid Model For Lattice Cell Structure Using Numerical Approaches, Tahseen Abdulridha Ali Al-Wattar Jan 2020

Developing Equivalent Solid Model For Lattice Cell Structure Using Numerical Approaches, Tahseen Abdulridha Ali Al-Wattar

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Lattice cell structures (LCS) are the engineered porous structures that are composed of periodic unit cells in three dimensions. Such structures have many scientific and engineering applications, such as in vessel gas technology, thermal systems, mechanical and aerospace structures, etc. for which lightweight, high strength, and energy absorption capabilities are essential properties. To have an optimized design, finite element analysis (FEA) based computational approach can be used for detailed analysis of such structures, sometime in full scale. However, developing a large-scale model for a lattice-based structure is computationally expensive. If an equivalent solid FE model can be developed using the …

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Online Clustering With Bayesian Nonparametrics, Matthew D. Scherreik Jan 2020

Online Clustering With Bayesian Nonparametrics, Matthew D. Scherreik

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Clustering algorithms, such as Gaussian mixture models and K-means, often require the number of clusters to be specified a priori. Bayesian nonparametric (BNP) methods avoid this problem by specifying a prior distribution over the cluster assignments that allows the number of clusters to be inferred from the data. This can be especially useful for online clustering tasks, where data arrives in a continuous stream and the number of clusters may dynamically change over time. Classical BNP priors often overestimate the number of clusters, however, leading researchers to develop new priors with more control over this tendency. To date, BNP algorithms …

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Development Of Real-Time Systems For Supporting Collaborations In Distributed Human And Machine Teams, Aishwarya Bositty Jan 2020

Development Of Real-Time Systems For Supporting Collaborations In Distributed Human And Machine Teams, Aishwarya Bositty

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Real-time distributed systems constitute computing nodes that are connected by a network and coordinate with one another to accomplish a cooperative task, combining the responsiveness, fault-tolerance and geographic independence to support time-constrained collaborative applications, including distributed Human-Machine Teaming. In this thesis research the viability of real-time distributed collaborative technologies is demonstrated through the design, development and validation of prototype systems that support two human-machine teaming scenarios namely, ACE-IMS (Affirmation Cue based Interruption Management Systems) and ReadMI (Real-time Assessment of Dialogue in Motivational Interview). ACE-IMS demonstrates how a combination of AI capabilities and the cloud and mobile computing infrastructure can be …

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Mitigating Atmospheric Phase Errors In Sal Data, Randy S. Depoy Jr. Jan 2020

Mitigating Atmospheric Phase Errors In Sal Data, Randy S. Depoy Jr.

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Synthetic aperture ladar (SAL) is an emerging remote sensing technology capable of providing high-resolution, interpretable, and timely imagery. SAL and synthetic aperture radar (SAR) are similar in that they provide high-resolution imagery suitable for a wide-variety of applications beyond the diffraction limit of the real aperture. Several advantages of SAL are; realistic imagery resulting from diffuse scattering of optically-rough objects, fine directionality of laser beam making the technology inherently low probability-of-detect, and shorter synthetic aperture collection times, all of which result from operating at optical as opposed to RF wavelengths. With the dramatic decrease in wavelength, SAL systems become more …

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Understanding Visual Representation Of Imputed Data For Aiding Human Decision-Making, Ryan M. Thompson Jan 2020

Understanding Visual Representation Of Imputed Data For Aiding Human Decision-Making, Ryan M. Thompson

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The effectiveness of representing higher dimensional data on a two-dimensional visualization was required to be studied in the development of a novel data imputation method, Continuous Imputation With Association Rules (CIWAR). When the CIWAR method is used to impute missing data, the method generates additional metadata that increases each imputed data point's dimensionality. Potential use cases for CIWAR include situations where imputed data would be analyzed by individuals with little or no data analytic experience or situations where imputed data would be used to aid high-stress time-critical human decision processes. A study was conducted to assess the effect of the …

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Turbine Passage Vortex Response To Upstream Periodic Disturbances, Mitchell Lee Scott Jan 2020

Turbine Passage Vortex Response To Upstream Periodic Disturbances, Mitchell Lee Scott

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Flow through the turbine section of gas turbine engines is inherently unsteady due to a variety of factors, such as the relative motion of rotors and stators. In low pressure turbines, periodic wake passing has been shown to impact boundary layer separation, blade surface pressure distribution, and loss generation. The effect of periodic disturbances on the endwall flow is less understood. Endwall flow in a low-pressure turbine occurs in the boundary layer region of the flow through the blade passage where the blade attaches to the hub in the turbine. The response of an endwall vortical structure, the passage vortex, …

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