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Theses and Dissertations

Theses/Dissertations

1996

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Articles 1 - 30 of 88

Full-Text Articles in Physical Sciences and Mathematics

On Unifying Time And Uncertainty: The Probabilistic Temporal Network, Joel D. Young Dec 1996

On Unifying Time And Uncertainty: The Probabilistic Temporal Network, Joel D. Young

Theses and Dissertations

Complex real-world systems consist of collections of interacting processes/events. These processes change over time in response to both internal and external stimuli as well as to the passage of time. Many domains such as real-time systems diagnosis, (mechanized) story understanding, planning and scheduling, and financial forecasting require the capability to model complex systems under a unified framework to deal with both time and uncertainty. Existing uncertainty representations and existing temporal models already provide rich languages for capturing uncertainty and temporal information, respectively. Unfortunately, these partial solutions have made it extremely difficult to unify time and uncertainty in a way that …

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Modeling And Simulation Of Optical Characteristics Of Microelectromechanical Mirror Arrays, Peter C. Roberts Dec 1996

Modeling And Simulation Of Optical Characteristics Of Microelectromechanical Mirror Arrays, Peter C. Roberts

Theses and Dissertations

MEMS (Micro-Electro-Mechanical Systems) micromirror devices can be used to control the phase of a propagating light wavefront, and in particular to correct aberrations that may be present in the wavefront, due to either atmospheric turbulence or any other type of fixed or time and space varying aberrations. In order to shorten the design cycle of MEMS micromirror devices, computer software is developed to create, from MEMS micromirror device design data, a numerical model of the MEMS device. The model is then used to compute the far field diffraction pattern of a wavefront reflected from the device, and to predict the …

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Student Modeling In An Intelligent Tutoring System, Jeremy E. Thompson Dec 1996

Student Modeling In An Intelligent Tutoring System, Jeremy E. Thompson

Theses and Dissertations

This thesis explores a new approach to modeling the student in an intelligent tutoring system (ITS), by providing a student model which learns new solutions from the student. A prototype of the new approach to ITS is demonstrated in the Euclidean geometry domain. Complete C++, CLIPS, and Tcl/Tk code listings are included in the appendices for reference. Adaptable multiple software agents were targeted for implementation, based on current literature. However, the student model is found to be maintainable without multiple software agents, while still allowing for tracking several possible solution paths when monitoring student solutions. This capability contradicts previous research …

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Analysis And Design Of Standard Telerobotic Control Software, Matthew L. June Dec 1996

Analysis And Design Of Standard Telerobotic Control Software, Matthew L. June

Theses and Dissertations

The Robotics and Automation Center for Excellence (RACE) has defined an open telerobotics control architecture. This architecture, called the Unified Telerobotic Architecture Project (UTAP), is a proposed standard for all Air Force telerobotic systems. Implementation of UTAP will reduce the cost of robotic applications by increasing software modularity, portability, and reusability. This thesis continued the effort to prove the feasibility of UTAP. In December, 1995, 1st Lt Anchor implemented a portion of the UTAP specification on a PUMA robot. The UTAP-compliant controller exhibited some degradation in the system performance. However, the performance degradation was not fully measured. This thesis extended …

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Graphical Display Of A Missile Endgame Scenario, Joseph E. Moritz Dec 1996

Graphical Display Of A Missile Endgame Scenario, Joseph E. Moritz

Theses and Dissertations

Traditionally, computer programs to model and simulate air-to-air missile endgame engagements have focused on improving the underlying probability of kill models. This focus, however, understates the benefits of current computer graphics technology for visualization and direct manipulation of missile endgame parameters and building engagement understanding through real-time, three dimensional simulation of the endgame. Our research has been to develop a versatile simulation system to display the missile endgame parameters and allow graphical interaction with these parameters. This program also allows the user to view animated engagements of previously designed endgames. The current project scope is to provide user feedback of …

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Algebraic Algorithm Design And Local Search, Robert P. Graham Jr. Dec 1996

Algebraic Algorithm Design And Local Search, Robert P. Graham Jr.

Theses and Dissertations

Formal, mathematically-based techniques promise to play an expanding role in the development and maintenance of the software on which our technological society depends. Algebraic techniques have been applied successfully to algorithm synthesis by the use of algorithm theories and design tactics, an approach pioneered in the Kestrel Interactive Development System (KIDS). An algorithm theory formally characterizes the essential components of a family of algorithms. A design tactic is a specialized procedure for recognizing in a problem specification the structures identified in an algorithm theory and then synthesizing a program. Design tactics are hard to write, however, and much of the …

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Laser-Induced Breakdown Spectroscopy On Solution Samples Using Surface Excitation, Leonard M. Berman Dec 1996

Laser-Induced Breakdown Spectroscopy On Solution Samples Using Surface Excitation, Leonard M. Berman

Theses and Dissertations

Laser-induced breakdown spectroscopy (LIBS) is a spectroscopic technique where output from a pulsed laser is focused onto a target in order to create an intense plasma. The optical emission is characteristic of the elements in the focal volume and can be used for elemental analysis. Research on the detection of nickel in solution in addition to solvent detection of CCl4, CHCl3, C2Cl4, and C2HCl3 has been performed. Breakdown was formed at the sample surface via a Q-switched Nd:YAG laser. Initially, operation of the laser was at 1064 nm/repetition rate of 5 Hz. Experiments …

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Evaluation Of Segmentation For Bone Structures In 3d Rendering Of Ultrasound Residual Limb Images, Min C. Baker Dec 1996

Evaluation Of Segmentation For Bone Structures In 3d Rendering Of Ultrasound Residual Limb Images, Min C. Baker

Theses and Dissertations

Prosthetists today widely practice manual socket fitting, which produces subjective, inconsistent results. To address this problem, the Computerized Anthropometry Research and Design (CARD) Laboratory is developing a computer-aided socket design system that acquires ultrasound datasets of an amputee's residual limb, creates a 3D model, and helps identify load- bearing and pressure-relief areas. This research project focuses on providing 3D visualization of a residual limb to support the CARD Laboratory's efforts. Creating the 3D model of the skin and two bone contours requires two major steps: segmentation to identify the objects of interest and a surface tracking algorithm to generate the …

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Requirements, Design, And Development Of A Rapidly Reconfigurable, Photo-Realistic, Virtual Cockpit Prototype, Terry A. Adams Dec 1996

Requirements, Design, And Development Of A Rapidly Reconfigurable, Photo-Realistic, Virtual Cockpit Prototype, Terry A. Adams

Theses and Dissertations

The United States Air Force uses aircraft flight simulators for pilot training and mission rehearsal. They use a variety of simulators for this task ranging with prices ranging from $400,000 to $30,000,000. These simulators have specialized hardware that restricts reuse of their components and increases maintenance costs. Air Education and Training Command wants to reduce simulators cost and improve availability to the operational commands by supporting research in virtual reality flight simulators. This thesis looks at the development of a reconfigurable virtual cockpit in a distributed virtual environment that can be used for different aircraft as well as training scenarios. …

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Simulation Based Performance Evaluation Of Resource Allocation Algorithms For Implementation In The Shf-Dama Satellite Network, Eric P. Hobson Dec 1996

Simulation Based Performance Evaluation Of Resource Allocation Algorithms For Implementation In The Shf-Dama Satellite Network, Eric P. Hobson

Theses and Dissertations

Sponsored by DISA, the SHF-DAMA Standard addresses the warfighter's requirements for flexible, reliable, and efficient (technically and fiscally) satellite communications. The Standard proposes a system supporting both packet data transfer and single-channel-per-carrier voice and data circuits assigned on a demand basis. The Standard does not address management of the DSCS 3 transponder's bandwidth and power resources among priority classes of users. This effort characterizes the SHF-DAMA system's performance over each combination of the following resource management algorithm features: (1) preemption enabled and disabled; (2) using the Standard-specified collision resolution technique and a binary exponential backoff; (3) using complete partitioning, complete …

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Integrating The Capability Maturity Model For Software And The Quality Air Force Criteria, Marshall B. Messamore Dec 1996

Integrating The Capability Maturity Model For Software And The Quality Air Force Criteria, Marshall B. Messamore

Theses and Dissertations

As defense budgets decrease and it is required to do more with less, the Air Force has chosen to use the Malcolm Baldrige National Quality Award (MBNQA) as the basis for implementing quality principles. The Air Force program is known as Quality Air Force (QAF), and the criteria are referred to as the QAF criteria DEPA95b. At about the same time the Department of the Air Force implemented QAF, the software leaders in the Air Force adopted the Capability Maturity Model for Software (CMM) as the internal standard for Air Force software organizations MOSE9l. Software organizations strapped with both sets …

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The Development Of A Scenario Translator For Distributed Simulations, Heon-Gyu Park Dec 1996

The Development Of A Scenario Translator For Distributed Simulations, Heon-Gyu Park

Theses and Dissertations

There exists a variety of simulation generation and analysis products which have differing purposes and functions designed to simulate a real military battlefield. Due to the particular purpose of each simulation it is impractical to use one scenario of a simulation directly with another simulation without a translator since there is no standard scenario format. In the current environment interoperability between simulations is becoming more important in large scale simulations and distributed exercises. The Scenario File Translator (SFT) provides an easy and accurate way to create a scenario from a heterogeneous simulation. The SFT can load and save the three …

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Utilizing Data And Knowledge Mining For Probabilistic Knowledge Bases, Daniel J. Stein Iii Dec 1996

Utilizing Data And Knowledge Mining For Probabilistic Knowledge Bases, Daniel J. Stein Iii

Theses and Dissertations

Problems can arise whenever inferencing is attempted on a knowledge base that is incomplete. Our work shows that data mining techniques can be applied to fill in incomplete areas in Bayesian Knowledge Bases (BKBs), as well as in other knowledge-based systems utilizing probabilistic representations. The problem of inconsistency in BKBs has been addressed in previous work, where reinforcement learning techniques from neural networks were applied. However, the issue of automatically solving incompleteness in BKBs has yet to be addressed. Presently, incompleteness in BKBs is repaired through the application of traditional knowledge acquisition techniques. We show how association rules can be …

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Solar System Modeler: A Distributed, Virtual Environment For Space Visualization And Gps Navigation, Gary E. Williams Dec 1996

Solar System Modeler: A Distributed, Virtual Environment For Space Visualization And Gps Navigation, Gary E. Williams

Theses and Dissertations

The Solar System Modeler (SM) extends the Space Modeler developed in 1994. It provides a virtual environment enabling an explorer to dynamically investigate near Earth satellites, deep space probes, planets, moons, and other celestial phenomena. The explorer navigates the virtual environment via mouse selected options from menu panels while wearing a tracked, head mounted display (HMD). Alternatively, a monitor may replace the HMD and keyboard controls replace head tracking. The SM's functionality is extended by the ability to broadcast simulated GPS satellite transmissions in compliance with Distributed Interactive Simulation (DIS) protocol standards. The transmissions include information found in true GPS …

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Modeling Marine Exposure To Polychlorinated Biphenyls From Sunken Ships, Charles N. Wendt Dec 1996

Modeling Marine Exposure To Polychlorinated Biphenyls From Sunken Ships, Charles N. Wendt

Theses and Dissertations

In the past, the U.S. Navy has routinely conducted SINKing EXercises (SINKEX) for training, weapon effectiveness tests, and economic disposal of aging assets. Recent concern over polychlorinated biphenyl (PCB) chemicals aboard such target vessels has resulted in a suspension of SINKEX. The U.S. Navy has approximately 200 vessels currently requiring such disposal. Environmental legislation and health concerns preclude selling such vessels to foreign governments or scrapping. This work attempted to model the fate and transport of these PCBs by examining their transport to coastal water and their accumulation in the marine food chain. The model includes biodegradation, upwelling, partitioning of …

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Analysis Of Multimode Low-Probability-Of-Intercept (Lpi) Communications With Atmospheric Effects, Ala Ghordlo Dec 1996

Analysis Of Multimode Low-Probability-Of-Intercept (Lpi) Communications With Atmospheric Effects, Ala Ghordlo

Theses and Dissertations

This research expanded Low Probability of Intercept (LPI) communications analysis in two areas. First, multimode communication was included to account for ground to ground and air to ground links in addition to the standard air to air links traditionally used in LPI analysis. The propagation equations for the three modes of interest were derived and included in LPI analytic models in the form of a mode quality factor to account for multimode LPI scenarios. This new quality factor was used in studying several communication and interception link combinations. Variations due to differences between the communication and interception modes were presented …

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Analysis And Simulation Of A New Code Tracking Loop For Gps Multipath Mitigation, Mark C. Laxton Dec 1996

Analysis And Simulation Of A New Code Tracking Loop For Gps Multipath Mitigation, Mark C. Laxton

Theses and Dissertations

This thesis proposes a new direct sequence spread spectrum (DS/SS) code phase tracking loop which mitigates the effects of multipath interference on code phase tracking error; such errors can translate to significant range measurement errors in DS/SS ranging systems such as Global Positioning System (GPS). The new code tracking loop, called the modified RAKE delay lock loop (MRDLL), uses maximum likelihood (ML) signal parameter estimation to determine the amplitude, carrier phase, and relative propagation delay of both a direct path and a reflected signal; a multiple correlator code phase tracking loop then exploits these ML signal estimates to remove the …

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Performance Analysis Of A Hartman Wavefront Sensor Used For Sensing Atmospheric Turbulence Statistics, Toby D. Reeves Dec 1996

Performance Analysis Of A Hartman Wavefront Sensor Used For Sensing Atmospheric Turbulence Statistics, Toby D. Reeves

Theses and Dissertations

Atmospheric turbulence parameters, such as Fried's coherence diameter, the outer scale of turbulence, and the turbulence power law, are related to the wavefront slope structure function (SSF). The SSF is defined as the second moment of the wavefront slope difference as a function of both time and position. Knowledge of the SSF allows turbulence parameters to be estimated. Hartmann wavefront sensor (H-WFS) slope measurements composed of both signal and noise, allow the SSF to be estimated by computing a mean square difference of H-WFS slope measurements. The quality of the SSF estimate is quantified by the signal-to-noise ratio (SNR) of …

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Deconvolution From Wavefront Sensing Using Optimal Wavefront Estimators, Scott R. Maethner Dec 1996

Deconvolution From Wavefront Sensing Using Optimal Wavefront Estimators, Scott R. Maethner

Theses and Dissertations

A cost effective method to improve the space surveillance mission performance of United States Air Force (USAF) ground-based telescopes is investigated and improved. A minimum variance wavefront estimation technique is used to improve Deconvolution from Wavefront Sensing (DWFS), a method to mitigate the effects of atmospheric turbulence on imaging systems that does not require expensive adaptive optics. Both least-squares and minimum variance wavefront phase estimation techniques are investigated, using both Gaussian and Zernike polynomial elementary functions. Imaging simulations and established performance metrics are used to evaluate these wavefront estimation techniques for a one-meter optical telescope. Performance metrics include the average …

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Analysis Of Linkage-Friendly Genetic Algorithms, Laurence D. Merkle Dec 1996

Analysis Of Linkage-Friendly Genetic Algorithms, Laurence D. Merkle

Theses and Dissertations

Evolutionary algorithms (EAs) are stochastic population-based algorithms inspired by the natural processes of selection, mutation, and recombination. EAs are often employed as optimum seeking techniques. A formal framework for EAs is proposed, in which evolutionary operators are viewed as mappings from parameter spaces to spaces of random functions. Formal definitions within this framework capture the distinguishing characteristics of the classes of recombination, mutation, and selection operators. EAs which use strictly invariant selection operators and order invariant representation schemes comprise the class of linkage-friendly genetic algorithms (lfGAs). Fast messy genetic algorithms (fmGAs) are lfGAs which use binary tournament selection (BTS) with …

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Electrical Characterization Of Intrinsic And Induced Deep Level Defects In Hexagonal Sic, James D. Scofield Dec 1996

Electrical Characterization Of Intrinsic And Induced Deep Level Defects In Hexagonal Sic, James D. Scofield

Theses and Dissertations

Deep level defects in hexagonal SiC were studied using digital deep level transient spectroscopy (DLTS) methods over the temperature range of 100 to 800 deg K. New centers were found in bulk and epitaxial 6H-SiC with ionization energies between 0.38 to 1.3 eV, and levels from 0.2 to 0.856 eV were identified in 4H-SiC epitaxy. Direct correlation between inequivalent lattice sites was identified for energetic pairs associated with both vanadium and ion implanted Mg impurities. Nonradioative carrier capture mechanisms were studied and deep level trapping was found to proceed via lattice relaxation multi-phonon emission, indicating efficient electronic lattice coupling in …

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Theoretical Modeling Of Linear Absorption Coefficients In Si/Si1-Xgex Multiple Quantum Well Photodetectors, Kevin D. Greene Dec 1996

Theoretical Modeling Of Linear Absorption Coefficients In Si/Si1-Xgex Multiple Quantum Well Photodetectors, Kevin D. Greene

Theses and Dissertations

Si/Si1-xGex MQW Infrared Photodetectors offer the promise of normal incidence photodetection tunable over the range of 3-12 micrometers wavelength range at temperatures above 40 K. This system is attractive because the Si1-xGex offers greater compatibility with existing Si based signal processing circuitry. Band structures, momentum matrix elements and linear absorption coefficients are computed using a Luftinger-Kohn k/p analysis for Si/Si1-xGex quantum wells grown in the 110 direction. The absorption coefficient as a function of energy and wavelength is calculated by two methods: a delta function fit to intersubband transitions, and a …

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Demonstrating Optical Aberration Correction With A Mems Micro-Mirror Device, Shaun R. Hick Dec 1996

Demonstrating Optical Aberration Correction With A Mems Micro-Mirror Device, Shaun R. Hick

Theses and Dissertations

This research conducted the first demonstrated use of a micro-electro-mechanical structure (MEMS) mirror array to correct a static optical aberration. A well-developed technique in adaptive optics imaging systems uses a deformable mirror to reflect the incident wave front to the imaging stage of the system. By matching the surface of the deformable mirror to the shape of the wave front phase distortion, the reflected wave front will be less aberrated before it is imaged. Typical adaptive optics systems use piezo-electric actuated deformable mirrors. This research used an electrostatically actuated, segmented mirror array, constructed by standard MEMS fabrication techniques, to investigate …

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Investigation Of Ba, Bao, Sr And Sro Pulsed Laser-Induced Vapor Plumes In N2, O2, Microwave Discharged O2, And Vacuum At Low Laser Fluence, David L. Byers Dec 1996

Investigation Of Ba, Bao, Sr And Sro Pulsed Laser-Induced Vapor Plumes In N2, O2, Microwave Discharged O2, And Vacuum At Low Laser Fluence, David L. Byers

Theses and Dissertations

Ba, BaO, Sr and SrO were ablated by 248 nm laser pulses at fluences ranging from 270 mJ-/sq cm to 575 mJ-/sq cm in vacuum and in 25 mtorr atmospheres of N2, O2 and microwave-discharged O2. The spectral emissions of these plumes were compared for indications of ionization due to Ba or Sr collisions with each gas. The addition of a background gas increased the ion and neutral signature across the spectrum. SrO band emission was observed at 16,600-16,900/cm and possible BaO band emissions were observed in the 18,250-18,400/cm, 19,000-19700/cm and 19,800-20,000/cm regions. A screened plate ion probe was use …

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Unfolding The High Energy Electron Flux From Crres Fluxmeter Measurements, Brian D. Mckellar Dec 1996

Unfolding The High Energy Electron Flux From Crres Fluxmeter Measurements, Brian D. Mckellar

Theses and Dissertations

The Combined Release and Radiation Effects Satellite (CRRES) was launched on 25 July 1990 to collect measurements in the earth's radiation belts. One instrument, the High Energy Electron Fluxmeter (HEEF), measured the flux of electrons in 10 channels with energies between 1 MeV and 10 MeV. The channel sensitivities, Ri(E), have been calibrated and partially re-calibrated. We explore the errors introduced in unfolding the electron flux spectrum from the channel measurements and the propagation and growth of calibration and measurement errors. Using numerical experimentation, we fold the responses with known spectra to obtain simulated measurements, add random measurement and calibration …

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Pulse Coupled Neural Networks For The Segmentation Of Magnetic Resonance Brain Images, Shane L. Abrahamson Dec 1996

Pulse Coupled Neural Networks For The Segmentation Of Magnetic Resonance Brain Images, Shane L. Abrahamson

Theses and Dissertations

This research develops an automated method for segmenting Magnetic Resonance (MR) brain images based on Pulse Coupled Neural Networks (PCNN). MR brain image segmentation has proven difficult, primarily due to scanning artifacts such as interscan and intrascan intensity inhomogeneities. The method developed and presented here uses a PCNN to both filter and segment MR brain images. The technique begins by preprocessing images with a PCNN filter to reduce scanning artifacts. Images are then contrast enhanced via histogram equalization. Finally, a PCNN is used to segment the images to arrive at the final result. Modifications to the original PCNN model are …

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A Domain Independent Framework For Developing Knowledge Based Computer Generated Forces, James L. Benslay Jr. Dec 1996

A Domain Independent Framework For Developing Knowledge Based Computer Generated Forces, James L. Benslay Jr.

Theses and Dissertations

Computer Generated Forces (CGFs) are important players in Distributed Interactive Simulation (DIS) exercises. A problem with CGFs is that they do not exhibit sufficient human behaviors to make their use effective. The SOAR approach has yielded a human cognitive model that can be applied to CGFs, but this is extremely complex. The product of the research reported in this thesis is a much less complex behavioral framework for a CGF that is easy to validate, revise, and maintain. To support this, an existing, domain independent CGF architecture is discussed and applied to an experimental CGF. Techniques for modeling the knowledge …

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Inference Algorithm Performance And Selection Under Constrained Resources, Brett J. Borghetti Dec 1996

Inference Algorithm Performance And Selection Under Constrained Resources, Brett J. Borghetti

Theses and Dissertations

Knowing that reasoning over probabilistic networks is, in general, NP-hard, and that most reasoning environments have limited resources, we need to select algorithms that can solve a given problem as fast as possible. This thesis presents a method for predicting the relative performance of reasoning algorithms based on the domain characteristics of the target knowledge structure. Armed with this knowledge, the research shows how to choose the best algorithm to solve the problem. The effects of incompleteness of the knowledge base at the time of inference is explored, and requirements for reasoning over incompleteness are defined. Two algorithms for reasoning …

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Artificial Cochlea Design Using Micro-Electro-Mechanical Systems, George C. Dalton Ii Dec 1996

Artificial Cochlea Design Using Micro-Electro-Mechanical Systems, George C. Dalton Ii

Theses and Dissertations

The use of Micro-Electro-Mechanical Systems (MEMS) in the design of an artificial cochlea is investigated in depth. Interdigitated finger (comb), cantilever, bridge, and mirror resonators are presented as possible devices used to implement the artificial cochlea. These resonators are demonstrated to be extremely high Q devices, capable of being tuned with a simple DC bias. This suggests a possible change to existing cochlea models that claim highly complex AC feedback as being responsible for changes in the damping of the basilar membrane. The new cochlea model presented here, using MEMS to approximate the tuning of the basilar membrane, may be …

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Design And Prototype Of The Afit Virtual Emergency Room: A Distributed Virtual Environment For Emergency Medical Simulation, Brian W. Garcia Dec 1996

Design And Prototype Of The Afit Virtual Emergency Room: A Distributed Virtual Environment For Emergency Medical Simulation, Brian W. Garcia

Theses and Dissertations

Due to the increasing complexity of emergency medical care, medical staffs require increasingly sophisticated training systems. Virtual environments offer a low cost means to achieve a widely usable yet sophisticated training capability. The Defense Advanced Research Projects Agency (DARPA) has sponsored the Virtual Emergency Room (VER) project to develop a simulation system that enables emergency department personnel within level I and II emergency rooms to practice emergency medical procedures and protocols. The VER is a simulation facility that uses a distributed virtual environment architecture to enable real-time, multi-participant simulations. The potential advantages of this system include the ability to evaluate …

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