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Full-Text Articles in Engineering
A First Principles Study Of Pipe Diffusion In Nickel, Luke J. Wirth
A First Principles Study Of Pipe Diffusion In Nickel, Luke J. Wirth
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Vacancy-mediated diffusion along dislocations, often referred to as pipe diffusion, can contribute to creep deformation of metals in many engineering applications. This process is studied along an a/2⟨1 -1 0⟩ screw dislocation in fcc Ni using a density functional theory approach. An accurate geometrical configuration of the screw dislocation core, dissociated into Shockley partial dislocations and separated by a stacking fault, was previously derived using a lattice Green's function technique. Activation energies and frequencies are calculated for atom-vacancy exchanges that contribute to diffusion around and along one of the partial cores. This analysis reveals the significant role of the sites …
Developing Equivalent Solid Model For Lattice Cell Structure Using Numerical Approaches, Tahseen Abdulridha Ali Al-Wattar
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 …
Hierarchical Hybrid Materials From Flexible Fabric Substrates, Wenhu Wang
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 …
Primary Processing Parameters And Their Influence On Porosity And Fatigue Life Of Additively Manufactured Alloy 718, Luke C. Sheridan
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 …
Additive Manufacturing Techniques To Enhance The Performance Of Electronics Created On Flexible And Rigid Substrates, Aamir Hamed Hamad
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 …
Processing And Properties Of Multifunctional Two Dimensional Nanocomposites Based On Graphene Nano-Flakes, Mohammed K. Mohammed
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 …
Designing New Generations Of Bcc Lattice Structures And Developing Scaling Laws To Predict Compressive Mechanical Characteristics And Geometrical Parameters, Hasanain Abdulhadi
Designing New Generations Of Bcc Lattice Structures And Developing Scaling Laws To Predict Compressive Mechanical Characteristics And Geometrical Parameters, Hasanain Abdulhadi
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Lattice structures (LSs) have been exploited for wide range applications including mechanical, thermal, and biomedical structures because of their unique attributes combining the light weight and relatively high mechanical properties. The first goal of this research is to investigate the effect of strut orientation and length on the compressive mechanical characteristics of body centered cubic (BCC) LS subjected to a quasi-static axial compressive loading using finite element analyses (FEA). In this study, two lattice generations were built and analyzed in commercial finite element (FE) software, ABAQUS/CAE 2016 using “smart procedure”, a meshing technique which was developed for this research to …
As-Manufactured Modeling Of A Mistuned Turbine Engine Compressor Evaluated Against Experimental Approaches, Daniel L. Gillaugh
As-Manufactured Modeling Of A Mistuned Turbine Engine Compressor Evaluated Against Experimental Approaches, Daniel L. Gillaugh
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As-manufactured rotors behave quite differently than nominal, as-designed rotors due to small geometric and material property deviations in the rotor, referred to as mistuning. Traditional integrally bladed rotor (IBR) modeling approaches assume each blade is identical. State-of-the-art IBR dynamic response predictions can be accomplished using asmanufactured models (AMM) generated via optical topography measurements and mesh morphing. As-manufactured models account for geometric deviations occurring through the machining process, material deviations and field wear, allowing each blade to respond differently. Rotor designs are intended to avoid resonance crossings throughout an engine’s operating range, but total avoidance is challenging. This has led to …
Non-Deterministic Metamodeling For Multidisciplinary Design Optimization Of Aircraft Systems Under Uncertainty, Daniel L. Clark Jr.
Non-Deterministic Metamodeling For Multidisciplinary Design Optimization Of Aircraft Systems Under Uncertainty, Daniel L. Clark Jr.
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To make coupled multi-physics-informed design decisions, multidisciplinary analysis, design optimization and uncertainty quantification must be present to accurately represent the full system under investigation. Unfortunately, all of these processes are computationally demanding, requiring a large number of system evaluations with identified uncertain variables, and iterative system evaluations with respect to the design variables of interest. Surrogate or metamodels are used to alleviate the computational burden in both these design exploration activities by trading accuracy with efficiency. The primary objective of this dissertation is to develop a flexible surrogate modeling technique capable of quantifying the uncertainty of multidisciplinary systems in an …
Immersive Rehearsal In A Simulated Environment (Irise), Cassandra Clouse
Immersive Rehearsal In A Simulated Environment (Irise), Cassandra Clouse
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Recent advancements in virtual environment (VE) technology and the growth of VE use in treating and training individuals are opening up new possibilities for rehearsal in safe and rich environments. Research has shown that VEs can be used to treat those with Post Traumatic Stress Disorder (PTSD), but very little research has been done to suggest good guidelines for creating an effective environment. This research was conducted to help inform the design of systems that let veterans rehearse potentially stressful experiences in a safe environment before having to physically step into that environment. We investigated responses to specific design components …
Processing And Properties Of Multifunctional Two-Dimensional Nanocomposite Based On Single Wall Carbon Nanotubes, Ali M. Al Mafarage
Processing And Properties Of Multifunctional Two-Dimensional Nanocomposite Based On Single Wall Carbon Nanotubes, Ali M. Al Mafarage
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Truly single layer (monolayer) films of unmodified zigzag single-walled carbon nanotubes by using the Langmuir-Blodgett (LB) technique have been processed successfully. Measurements of their mechanical and optoelectric properties were achieved. Different theoretical equations were used based on the results obtained from the experimental part to study the properties and structures of the produced material and their composite. The produced films were highly oriented as determined by polarized Raman spectroscopy and as shown by scanning tunneling microscopy (STM). The films have a significant amount of flexibility which makes their behavior similar to rubbery materials. They can also be deposited on different …
Strategic Decision Facilitation: An Exploration Of Alternative Anchoring And Scale Distortion Optimization In Multi-Attribute Group Decision Making, Joseph Patrick Kristbaum
Strategic Decision Facilitation: An Exploration Of Alternative Anchoring And Scale Distortion Optimization In Multi-Attribute Group Decision Making, Joseph Patrick Kristbaum
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Choosing between alternatives, regardless of the decision context in an organizational group setting is a difficult task. The integrity of the decision is under constant scrutiny and rarely are we ever able to characterize the magnitude of that with which we are consciously or subconsciously concerned: personal bias. This leads to long, drawn out timelines and loosely trusted decisions. This dissertation research focuses on using a traditionally, negatively viewed anchoring bias strategically in a series of experiments with a hypothesis that it can be used to positively reduce personal biases such as preference bias and judgement rooted in ambiguous or …
True-Average Current-Mode Control Of Dc-Dc Power Converters: Analysis, Design, And Characterization, Dalvir K. Saini
True-Average Current-Mode Control Of Dc-Dc Power Converters: Analysis, Design, And Characterization, Dalvir K. Saini
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Energy efficient, wide-bandwidth, and well-regulated dc-dc power converters are in great demand in today's emerging technologies in areas such as medical, communication, aerospace, and automotive industries. In addition to design and selection of the converter components, a robust closed-loop modeling is very essential for reliable power-electronic systems. Two closed-loop control techniques for power converters exist: voltage-mode control and current-mode control. The principles of voltage-mode control have been explored in great depths by researchers over the last two decades. However, the dynamic modeling of current-mode controlled dc-dc power converters has many uncharted areas that needs careful attention. Two main methods exist …
Multiscale Modeling Of Hemodynamics In Human Vessel Network And Its Applications In Cerebral Aneurysms, Hongtao Yu
Multiscale Modeling Of Hemodynamics In Human Vessel Network And Its Applications In Cerebral Aneurysms, Hongtao Yu
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Three-dimensional (3D) simulation of patient-specific morphological models has been widely used to provide the hemodynamic information of individual patients, such as wall shear stress (WSS), oscillatory shear index (OSI), and flow patterns, etc. Since patient-specific morphological segment was only restricted locally, boundary conditions (BCs) are required to implement the CFD simulation. Direct measurements of the flow and pressure waveforms were often required as input BCs for 3D CFD simulations of patient-specific models. However, as the morphology develops, the feedback from this topological deformation may lead to BCs being altered, and hence without this feedback, the flow characteristics of the morphology …
Wideband Doa And Parameter Estimation Of Chirp Sources Using Dcft And Compressive Sensing, Luay A. Al Irkhis
Wideband Doa And Parameter Estimation Of Chirp Sources Using Dcft And Compressive Sensing, Luay A. Al Irkhis
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Direction of Arrival (DoA) estimation of chirp sources has many applications in radar, sonar and medical imaging. This work considers DoA and parameter estimation of wide- band chirp sources by the use of Discrete Chirp Fourier Transform (DCFT), its Compres- sive Sensing formulation (CS-DCFT) and Distributed CS. DCFT is similar to traditional Discrete Fourier Transform (DFT) but with chirp ba- sis and two-dimensional search over chirp rate and chirp frequency. For chirp parame- ters estimation, the proposed Compressive Sensing (CS) formulation uses the parametric DCFT basis to achieve superior estimator performance in polynomial time using Orthog- onal Matching Pursuit (OMP) …
Hardware Security And Vlsi Design Optimization, Hao Xue
Hardware Security And Vlsi Design Optimization, Hao Xue
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Microelectronic circuit is ubiquitous component of modern electrical devices. The increasing complexity and professionality of phases in microelectronic supply chain bring more global cooperation to integrated circuit (IC) production. Therefore, providing a secure environment for microelectronic circuit design does not ensure the integrity of the hardware since any participator of IC fabrication has the opportunity to implant a malicious alteration in original IC design. Especially overseas chip-fabrication is a vital potential threat for national defense products. In theory, anyone who has access to fabrication process can tamper with the original design, with the potential to change function, modify parametric properties …
Thz Sources Based On Er-Doped Gaas Driven At Telecom-Fiber Wavelengths, Andrea Mingardi
Thz Sources Based On Er-Doped Gaas Driven At Telecom-Fiber Wavelengths, Andrea Mingardi
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This dissertation entails the investigation of ultrafast photoconductive (PC) THz sources driven by fiber and semiconductor lasers around λ= 1550-nm to utilize commercial fiber-optic telecom technology. The preferred approach is to use GaAs with a high concentration of erbium, which has performed well when driven with laser sources at both 800 nm wavelength, through intrinsic photoconductivity, and 1550 nm, through extrinsic photoconductivity. Studies in the early 1990s showed that the Er doping level has a solubility limit of ~ 7 × 1017 cm−3 at 580 °C, above which erbium is incorporated into GaAs as ErAs nanoparticles which promote resonant absorption …
Resonant Gate-Drive Circuits For High-Frequency Power Converters, Hur Jedi
Resonant Gate-Drive Circuits For High-Frequency Power Converters, Hur Jedi
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The development trend of power converters motivates the pursuit with high density, high efficiency, and low cost. Increasing the frequency can improve the power density and lead to small passive elements and a fast dynamic response. Each one of these power converters must be driven by a gate-drive circuit to operate efficiently. Conventional gate-drivers are used up to frequencies of about 5 MHz and suffer from switching losses. Therefore, the development of switch-mode power supplies (SMPS) operating at high frequencies requires high-speed gate drivers. The presented research in this dissertation focuses on analysis, design, and development of new types of …
3d Visualization And Interactive Image Manipulation For Surgical Planning In Robot-Assisted Surgery, Mohammadreza Maddah
3d Visualization And Interactive Image Manipulation For Surgical Planning In Robot-Assisted Surgery, Mohammadreza Maddah
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Robot-assisted surgery, or "robotic" surgery, has been developed to address the difficulties with the traditional laparoscopic surgery. The da Vinci (Intuitive Surgical, CA and USA) is one of the FDA-approved surgical robotic system which is widely used in the case of abdominal surgeries like hysterectomy and cholecystectomy. The technology includes a system of master and slave tele-manipulators that enhances manipulation precision. However, inadequate guidelines and lack of a human-machine interface system for planning the ports on the abdomen surface are some of the main issues with robotic surgery. Unreachable target and mid-surgery collisions between robotic arms are the major problems …
Analyzing A Shopper’S Visual Experience In A Retail Store And The Impact On Impulse Profit, Bradley Robert Guthrie
Analyzing A Shopper’S Visual Experience In A Retail Store And The Impact On Impulse Profit, Bradley Robert Guthrie
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The retail industry in the U.S. contributed 1.14 trillion in value added (or 5.9%) to the GDP in 2017, an increase of 3.7% from the previous year. While store closures have dominated the news in the recent past (e.g., Toys-R-Us, Sears, and Bon-Ton) due to ineffective supply chain practices, inadequate in-store experiences, and competition from e-tailers, other retailers such as Ross, T. J. Maxx, Burlington Coat Factory, and Kroger have been expanding their footprint. Brick-and-mortar stores are unique as they allow shoppers the ability to see, touch, and try products, in addition to exploring new products. Kohl’s CEO has even …
An Autonomous Intelligent Robotic Wheelchair To Assist People In Need: Standing-Up, Turning-Around And Sitting-Down, Iosif Papadakis Ktistakis
An Autonomous Intelligent Robotic Wheelchair To Assist People In Need: Standing-Up, Turning-Around And Sitting-Down, Iosif Papadakis Ktistakis
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The world’s ageing population has significantly increased over the last decades, which will result in one of the most significant transformations of the twenty-first century. As people age, they become more vulnerable to diseases and their health may need constant monitoring. At the same time, the number of people who have some kind of disability is also increasing. These people with disabilities may need daily assistance and monitoring of their health condition that is provided by specialists (health providers) at a high cost. A possible solution to the aforementioned problem comes from the assistive and intelligent robotics research area. The …
Distributed Adaptive Fault-Tolerant Control Of Nonlinear Uncertain Multi-Agent Systems, Mohsen Khalili
Distributed Adaptive Fault-Tolerant Control Of Nonlinear Uncertain Multi-Agent Systems, Mohsen Khalili
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The research on distributed multi-agent systems has received increasing attention due to its broad applications in numerous areas, such as unmanned ground and aerial vehicles, smart grid, sensor networks, etc. Since such distributed multi-agent systems need to operate reliably at all time, despite the possible occurrence of faulty behaviors in some agents, the development of fault-tolerant control schemes is a crucial step in achieving reliable and safe operations. The objective of this research is to develop a distributed adaptive fault-tolerant control (FTC) scheme for nonlinear uncertain multi-agent systems under intercommunication graphs with asymmetric weights. Under suitable assumptions, the closed-loop system's …
Estimating Channel Identification Quality In Passive Radar Using Lms Algorithms, Michael J. Callahan
Estimating Channel Identification Quality In Passive Radar Using Lms Algorithms, Michael J. Callahan
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Passive bistatic radar can be an attractive choice relative to monostatic radar because it provides the ability to operate covertly; immunity to jamming and interference; the ability to operate outside of traditional radar bands; and reduced cost. The benefits of noise waveforms versus classic radar waveforms such as linear frequency modulation (LFM) are discussed in the literature. Noise waveforms, with their thumbtack ambiguity functions, are ideal for use in non-cooperative passive radar. Since many digital waveforms are randomized to make their spectra approximately white, noise-like waveforms may be readily available for opportunistic use by non-cooperative passive radar receivers. For instance, …
Computational Simulations Of Biomechanical Kinematics In Wsu Total Ankle Replacement Systems, Dinesh Gundapaneni
Computational Simulations Of Biomechanical Kinematics In Wsu Total Ankle Replacement Systems, Dinesh Gundapaneni
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Ankle arthritis constitutes about 10% of all joint arthritis cases, however, the revision rate of ankle replacement devices is three times higher than comparable hip and knee devices. With complicated bone morphology and surrounding ligament structures, the physiological and gait characteristics of the ankle joint presents a challenge to biomechanicians. As a result, there is a lack of fundamental understanding how the ligaments and articular surfaces interact. The objective of this doctoral research is to address the pattern of contact at the joint articulation, the fundamental role of ligaments in joint mobility, and biomechanics of total ankle replacement (TAR) devices. …
On The Thermal And Contact Fatigue Behavior Of Gear Contacts Under Tribo-Dynamic Condition, Anusha Anisetti
On The Thermal And Contact Fatigue Behavior Of Gear Contacts Under Tribo-Dynamic Condition, Anusha Anisetti
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Gears are vital power transmitting mechanical components, in both automotive and aerospace applications, and commonly operate within relatively high rotational speed ranges. Therefore, the dynamic behavior of gears is inevitable and can be quite significant under certain circumstances. The gear dynamics introduces not only noises and vibrations, but also large tooth force amplitudes, and consequently large amplitudes of bending stresses and contact stresses, and high surface temperatures, promoting the failures of tooth bending fatigue, contact fatigue, and scuffing. This study focuses on the mechanism by which the gear dynamic responses affect the flash temperature rise and contact fatigue life using …
Efficacy Of Real-Time Functional Magnetic Resonance Imaging Neurofeedback Training (Fmri-Nft) In The Treatment Of Tinnitus, Matthew S. Sherwood
Efficacy Of Real-Time Functional Magnetic Resonance Imaging Neurofeedback Training (Fmri-Nft) In The Treatment Of Tinnitus, Matthew S. Sherwood
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There is a growing interest in the application of real-time (fMRI) with neurofeedback training (NFT) to the treatment of disorders associated with abnormal brain function. Chronic tinnitus is one such disorder that is often characterized by hyperactivity of the primary auditory cortex (A1) and decreased activity of the ventromedial prefrontal cortex (vmPFC). In this work, we investigated the use of fMRI-NFT to teach self-regulation of A1 using directed attention strategies. The overall objective of the proposed study is to determine the efficacy of fMRI-NFT for potential treatment of tinnitus. Healthy participants were separated into two groups: the experimental group received …
Engineering Inpatient Discharges: Disposition Prediction And Day-Of-Discharge Planning, Nicholas A. Ballester
Engineering Inpatient Discharges: Disposition Prediction And Day-Of-Discharge Planning, Nicholas A. Ballester
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Inpatient discharge planning is a critical decision point in patient care, with implications for the efficiency of the inpatient unit as well as other units of the acute care hospital. Inefficient discharge planning can cause patient boarding (waiting for beds) in the upstream units. While this is a poignant and well-known problem in healthcare, very little quantitative research exists that proposes approaches to alleviate it. To address this issue, we apply Systems Engineering methods with focus on three key challenges in inpatient discharge planning. First, to aid inpatient care providers in predicting discharge disposition (home vs. non-home) within 24-hours of …
Rapidly Solving Physics-Based Models For Uncertainty Propagation In Nondestructive Evaluation, Matthew Ryan Cherry
Rapidly Solving Physics-Based Models For Uncertainty Propagation In Nondestructive Evaluation, Matthew Ryan Cherry
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Recent research in extending nondestructive evaluation (NDE) methods toward damage and materials characterization has led to an emphasis on the development of physics-based forward models in NDE. Furthermore, a desire to quantify levels of uncertainty in NDE inspections, particularly in Air Force applications, has driven the need for quick solving surrogate models for the traditional forward models, which have largely focused on accurately capturing many aspects of the problem with little emphasis on computational effort. In the past 5 years, many different techniques for creating lower-fidelity, quickly solving models to be used in place of the expensive high fidelity simulations …
Decision Support For Literal And Non-Literal Imaging Sensors, Holly K. Zelnio
Decision Support For Literal And Non-Literal Imaging Sensors, Holly K. Zelnio
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The key contribution of this research was to characterize decision support system (DSS) performance as a function of sensor types ranging from a very literal electrooptical (EO) sensor to a very non-literal synthetic aperture radar (SAR) sensor. The specific DSS used in this research was developed based on the Applied Cognitive Task Analysis (ACTA), human performance modeling process, and a comprehensive literature search. The subject and DSS combined performance was characterized by objective interpretation accuracy and decision time and, in addition, the subject's trust, confidence, heuristics, and possible cognitive biases were elicited and analyzed. The measures of accuracy, time, and …
Abi And Beyond: Exploration Of The Precursors To Trust In The Human-Automation Domain, Christopher Stephen Calhoun
Abi And Beyond: Exploration Of The Precursors To Trust In The Human-Automation Domain, Christopher Stephen Calhoun
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This study investigated the extent to which the well-known precursors of interpersonal trust (ability, benevolence, integrity, or ABI) could be exploited, redefined, or added to when considering and developing models of trust between humans and technology. The ABI model explains only about half of the variation in interpersonal trust (Colquitt, Scott, & LePine, 2007), so two additional precursors to trust from the interpersonal and automation trust domains - transparency and humanness - were identified and studied. The experimental task involved users interacting with an automated aid (image processing and recommender system) through a simulated unmanned ground vehicle (UGV) interface to …