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Articles 1 - 30 of 52
Full-Text Articles in Engineering
Latency And Distortion Compensation In Augmented Environments Using Electromagnetic Trackers, Henry Himberg
Latency And Distortion Compensation In Augmented Environments Using Electromagnetic Trackers, Henry Himberg
Theses and Dissertations
Augmented reality (AR) systems are often used to superimpose virtual objects or information on a scene to improve situational awareness. Delays in the display system or inaccurate registration of objects destroy the sense of immersion a user experiences when using AR systems. AC electromagnetic trackers are ideally for these applications when combined with head orientation prediction to compensate for display system delays. Unfortunately, these trackers do not perform well in environments that contain conductive or ferrous materials due to magnetic field distortion without expensive calibration techniques. In our work we focus on both the prediction and distortion compensation aspects of …
Development Of A Rigid Body Computational Model For Investigation Of Wrist Biomechanics, Benjamin Majors
Development Of A Rigid Body Computational Model For Investigation Of Wrist Biomechanics, Benjamin Majors
Theses and Dissertations
The wrist is one of the most complex joints in the human body. As such, the wrist joint is difficult to model due to the number of bones involved and its intricate soft tissue interactions. Many studies have attempted modeling the wrist previously; however, the majority of these studies simplify the joint into two-dimensions or idealized mechanical joints to reduce the complexity of the simulation. While these approaches still yield valuable information, the omission of a third-dimension or geometry defined movements limits the models’ usefulness in predicting joint function under non-idealized conditions. Therefore, the goal of this study was to …
4-D Modeling Of Displacement Vector Fields For Improved Radiation Therapy, Elizabeth Zachariah
4-D Modeling Of Displacement Vector Fields For Improved Radiation Therapy, Elizabeth Zachariah
Theses and Dissertations
In radiation therapy, it is imperative to deliver high doses of radiation to the tumor while reducing radiation to the healthy tissue. Respiratory motion is the most significant source of errors during treatment. Therefore, it is essential to accurately model respiratory motion for precise and effective radiation delivery. Many approaches exist to account for respiratory motion, such as controlled breath hold and respiratory gating, and they have been relatively successful. They still present many drawbacks. Thus, research has been expanded to tumor tracking. This paper presents a spatio-temporal model for four dimensional CT reconstruction. The method begins with a set …
Synthesis And Characterization Of Electrospun Gelatin/Dendrimer Scaffold Encapsulated With A Silver As A Potential Antimicrobial Wound Dressing, Alpana Dongargaonkar
Synthesis And Characterization Of Electrospun Gelatin/Dendrimer Scaffold Encapsulated With A Silver As A Potential Antimicrobial Wound Dressing, Alpana Dongargaonkar
Theses and Dissertations
A novel nanofiber scaffold was fabricated and characterized as a potential antimicrobial wound dressing. Half generation polyamidoamine (PAMAM) dendrimer G3.5 was covalently conjugated to gelatin. Gelatin alone or with gelatin-dendrimer conjugates was electrospun into nanofiber scaffolds. Gelatin is a derivative of natural collagen, and it is biocompatible, non-toxic and inexpensive, making it a desirable component in a wound dressing. Dendrimers are synthetic polymers comprising of a central core, internal branches and reactive surface groups. They provide a structurally controlled architecture for drug release. Silver was incorporated into the scaffold in situ due to its broad spectrum of antimicrobial properties. The …
Development Of A Flexible Fpga-Based Platform For Flight Control System Research, Robert Demott
Development Of A Flexible Fpga-Based Platform For Flight Control System Research, Robert Demott
Theses and Dissertations
This work is part of ongoing research conducted at Virginia Commonwealth University relating to unmanned aerial vehicles. The primary objective of this thesis was to develop a flexible, high-performance autopilot platform in order to facilitate research on advanced flight control algorithms. A dual FPGA-based system architecture utilizing a stacked, multi-board design was created to meet this goal. Processing tasks were split between the two FPGA devices, allowing for improved system timing and increased throughput. A combination of analog and digital filtering techniques were employed in the new system, resulting in enhanced sensor accuracy and precision compared to the previous generation …
Development Of Electroencephalography Based Brain Controlled Switch And Nerve Conduction Study Simulator Software, Kai Qian
Theses and Dissertations
This thesis investigated the development of an EEG-based brain controlled switch and the design of a software for nerve conduction study. For EEG-based brain controlled switch, we proposed a novel paradigm for an online brain-controlled switch based on Event-Related Synchronizations (ERDs) following external sync signals. Furthermore, the ERD feature was enhanced by 3 event-related moving averages and the performance was tested online. Subjects were instructed to perform an intended motor task following an external sync signal in order to turn on a virtual switch. Meanwhile, the beta-band (16-20Hz) relative ERD power (ERD in reverse value order) of a single EEG …
Numerical Simulation Of Underground Solar Thermal Energy Storage, Marshall Sweet
Numerical Simulation Of Underground Solar Thermal Energy Storage, Marshall Sweet
Theses and Dissertations
The United States Department of Energy indicates that 97% of all homes in the US use fossil fuels either directly or indirectly for space heating. In 2005, space heating in residential homes was responsible for releasing approximately 502 million metric tons of carbon dioxide into the atmosphere. Meanwhile, the Sun provides the Earth with 1000 watts per square meter of power everyday. This document discusses the research of modeling a system that will capture and store solar energy during the summer for use during the following winter. Specifically, flat plate solar thermal collectors attached to the roof of a single …
Digital Implementation Of A True Random Number Generator, Sam Mitchum
Digital Implementation Of A True Random Number Generator, Sam Mitchum
Theses and Dissertations
Random numbers are important for gaming, simulation and cryptography. Random numbers have been generated using analog circuitry. Two problems exist with using analog circuits in a digital design: (1) analog components require an analog circuit designer to insure proper structure and functionality and (2) analog components are not easily transmigrated into a different fabrication technology. This paper proposes a class of random number generators that are constructed using only digital components and typical digital design methodology. The proposed classification is called divergent path since the path of generated numbers through the range of possible values diverges at every sampling. One …
Dual-Scale Modeling Of Two-Phase Fluid Transport In Fibrous Porous Media, Alireza Ashari
Dual-Scale Modeling Of Two-Phase Fluid Transport In Fibrous Porous Media, Alireza Ashari
Theses and Dissertations
The primary objective of this research is to develop a mathematical framework that could be used to model or predict the rate of fluid absorption and release in fibrous sheets made up of solid or porous fibers. In the first step, a two-scale two-phase modeling methodology is developed for studying fluid release from saturated/unsaturated thin fibrous media made up of solid fibers when brought in contact with a moving solid surface. Our macroscale model is based on the Richards’ equation for two-phase fluid transport in porous media. The required constitutive relationships, capillary pressure and relative permeability as functions of the …
High-Pressure And High-Temperature Density Measurements Of N-Pentane, N-Octane, 2,2,4-Trimethylpentane, Cyclooctane, N-Decane, And Toluene, Yue Wu
Theses and Dissertations
Information on the density of hydrocarbons at high pressures and temperatures is of great importance in many fields, such as the study of ultra-deep reservoirs up to ~240 MPa and 250°C. However, density data at such high pressures and temperatures are often not available in the literature. In this study, experimental densities are reported for n-pentane, n-octane, 2,2,4-trimethylpentane, cyclooctane, n-decane, and toluene to ~280 MPa and ~250°C. These experimental densities are in good agreement with available literature data, although the literature data for many of these fluids do not extend to the pressures and temperatures utilized in this study.
Application Of An Inverse-Hysteresis Iterative Control Algorithm For Afm Fabrication, Seth Ashley
Application Of An Inverse-Hysteresis Iterative Control Algorithm For Afm Fabrication, Seth Ashley
Theses and Dissertations
An iterative control algorithm (ICA) which uses an approximate inverse-hysteresis model is implemented to compensate for hysteresis to precisely fabricate features on a soft polymer substrate using an atomic force microscope (AFM). The AFM is an important instrument in micro/nanotechnology because of its ability to interrogate, manipulate, and fabricate objects at the micro/nanoscale. The AFM uses a piezoelectric actuator to position an AFM-probe tip relative to the sample surface in three dimensions. In particular, precision lateral control of the AFM-probe tip relative to the sample surface is needed to ensure high-performance operation of the AFM. However, precision lateral positioning of …
Handling External Events Efficiently In Gillespie's Stochastic Simulation Algorithm, Brad Geltz
Handling External Events Efficiently In Gillespie's Stochastic Simulation Algorithm, Brad Geltz
Theses and Dissertations
Gillespie's Stochastic Simulation Algorithm (SSA) provides an elegant simulation approach for simulating models composed of coupled chemical reactions. Although this approach can be used to describe a wide variety biological, chemical, and ecological systems, often systems have external behaviors that are difficult or impossible to characterize using chemical reactions alone. This work extends the applicability of the SSA by adding mechanisms for the inclusion of external events and external triggers. We define events as changes that occur in the system at a specified time while triggers are defined as changes that occur to the system when a particular condition is …
In Vitro Evaluation Of Mechanical Heart Valve Performance Using A Novel Test Chamber In An Automated Mock Circulatory Loop, Antonio Walker
In Vitro Evaluation Of Mechanical Heart Valve Performance Using A Novel Test Chamber In An Automated Mock Circulatory Loop, Antonio Walker
Theses and Dissertations
Valvular heart disease (VHD) continues to have significant effects on many people’s lives, with numbers expected to grow tremendously over the next few years. Individuals suffering from severe valvular heart disease usually require a heart valve transplant in order to restore the native valve’s vital unidirectional flow regulation. Therefore, artificial heart valve (AHV) research is of very high importance. Previous research studies have provided substantial input in the realm of AHV design relative to durability, thrombotic and hemolytic potential, and overall functionality. However, modifications continue to be warranted due to limitations in the accuracy and time efficiency of the in …
Confining An Organic Molecule In A Nanocavity: Effect On Rotational/Vibrational Motion And Its Consequence For Spin Dephasing., Lopamudra Das
Confining An Organic Molecule In A Nanocavity: Effect On Rotational/Vibrational Motion And Its Consequence For Spin Dephasing., Lopamudra Das
Theses and Dissertations
Recently, it was found that the strongly temperature-dependent spin dephasing time of bound electrons in the organic molecule tris(8-hydroxyquinoline aluminum), or Alq3, increases when a few of these molecules are confined within 1-2 nm sized nanocavities in porous alumina. What causes this increase is not well understood, but one possibility is that the rotational/vibrational modes of the molecule are altered inside a nanocavity, leading to suppression of spin coupling with these modes and a concomitant increase in the spin dephasing time. To test this possibility, we have carried out mid-infrared spectroscopy of few molecule clusters confined within 1-2 nm sized …
Development Of A Low Cost Autopilot System For Unmanned Aerial Vehicles, Jose Ortiz
Development Of A Low Cost Autopilot System For Unmanned Aerial Vehicles, Jose Ortiz
Theses and Dissertations
The purpose of this thesis was to develop a low cost autonomous flight control system for small unmanned aerial vehicles with the aim to support collaborative systems. A low cost hardware solution was achieved by careful selection of sensors, integration of hardware subsystems, and the use of new microcontroller technologies. Flight control algorithms to guide a vehicle though waypoint based flight paths and loiter about a point were implemented using direction fields. A hardware in the loop simulator was developed to ensure proper operation of all hardware and software components prior to flight testing. The resulting flight control system achieved …
Image Processing Algorithms For Diagnostic Analysis Of Microcirculation, Sumeyra Ummuhan Demir
Image Processing Algorithms For Diagnostic Analysis Of Microcirculation, Sumeyra Ummuhan Demir
Theses and Dissertations
Microcirculation has become a key factor for the study and assessment of tissue perfusion and oxygenation. Detection and assessment of the microvasculature using videomicroscopy from the oral mucosa provides a metric on the density of blood vessels in each single frame. Information pertaining to the density of these microvessels within a field of view can be used to quantitatively monitor and assess the changes occurring in tissue oxygenation and perfusion over time. Automated analysis of this information can be used for real-time diagnostic and therapeutic planning of a number of clinical applications including resuscitation. The objective of this study is …
Arterial Waveform Measurement Using A Piezoelectric Sensor, Ruizhi Zhang
Arterial Waveform Measurement Using A Piezoelectric Sensor, Ruizhi Zhang
Theses and Dissertations
This study aims to develop a new method to monitor peripheral arterial pulse using a PVDF piezoelectric sensor. After comparing different locations of sensor placement, a specific sensor wrap for the finger was developed. Its composition, size, and location make it inexpensive and very convenient to use. In order to monitor the effectiveness of the sensor at producing a reliable pulse waveform, a monitoring system, including the PZT sensor, ECG, pulse-oximeter, respiratory sensor, and accelerometer was setup. Signal analysis from the system helped discover that the PZT waveform is relative to the 1st derivative of the artery pressure wave. Also, …
Growth And Characterization Of Non-Polar Gan Materials And Investigation Of Efficiency Droop In Ingan Light Emitting Diodes, Xianfeng Ni
Theses and Dissertations
General lighting with InGaN light emitting diodes (LEDs) as light sources is of particular interest in terms of energy savings and related environmental benefits due to high lighting efficiency, long lifetime, and Hg-free nature. Incandescent and fluorescent light sources are used for general lighting almost everywhere. But their lighting efficiency is very limited: only 20-30 lm/W for incandescent lighting bulb, approximately 100 lm/W for fluorescent lighting. State-of-the-art InGaN LEDs with a luminous efficacy of over 200 lm/W at room temperature have been reported. However, the goal of replacing the incandescent and fluorescent lights with InGaN LEDs is still elusive since …
Polyurethane-Based Polymer Surface Modifiers With Alkyl Ammonium Co-Polyoxetane Soft Blocks: Reaction Engineering, Surface Morphology And Antimicrobial Behavior, Kennard Brunson
Theses and Dissertations
Concentrating quaternary (positive) charge at polymer surfaces is important for applications including layer-by-layer polyelectrolyte deposition and antimicrobial coatings. Prior techniques to introduce quaternary charge to the surface involve grafting of quaternary ammonium moieties to a substrate or using polyurethanes with modified hard segments however there are impracticalities involved with these techniques. In the case of the materials discussed, the quaternary charge is introduced via polyurethane based polymer surface modifiers (PSMs) with quaternized soft segments. The particular advantage to this method is that it utilizes the intrinsic phase separation between the hard and soft segments of polyurethanes. This phase separation results …
Real Time 3-D Tracking Of The High Dose Rate Radiation Source Using A Flat Panel Detector, Aditya Bondal
Real Time 3-D Tracking Of The High Dose Rate Radiation Source Using A Flat Panel Detector, Aditya Bondal
Theses and Dissertations
A number of QA procedures have been developed for Breast Brachytherapy treatments, yet none guarantee accurate dose delivery or allow conformation of the actual source position leading to errors sometimes going unnoticed. The objective of this study is to track the exact path the HDR source would follow in real time. The exit radiation of the HDR source was used to image a well defined matrix of markers. The images were acquired using FPD and were processed to obtain projection coordinates while an x-ray calibration image was processed to obtain marker coordinates. Each marker along with its projection represents a …
Eye Movements In Elite Athletes - An Index For Performance., Harshad Hegde
Eye Movements In Elite Athletes - An Index For Performance., Harshad Hegde
Theses and Dissertations
Introduction: In gymnastics, athletes perform twisting and flipping skills at high angular velocities. These athletes rely heavily on sensory information from the visual, proprioceptive, and vestibular systems. The vestibulo-ocular reflex (VOR) is responsible for stabilizing the visual field on the retina during head movement. To accomplish this, the eyes are reflexively moved in a direction opposite the head. In a twisting gymnast, this actually reduces the ability of gymnasts to see the landing during airborne skills. Hence it becomes necessary for the gymnasts to cancel or suppress their VOR in order to view the landing. Objective: The purpose of this …
Effect Of Mechanical Stimulation On Mesenchymal Stem Cell Seeded Cartilage Constructs, Karin Wartella
Effect Of Mechanical Stimulation On Mesenchymal Stem Cell Seeded Cartilage Constructs, Karin Wartella
Theses and Dissertations
Cartilage tissue engineered constructs using mesenchymal stem cells were stimulated with 3 different stimulation algorithms to achieve characteristics mimicking the superficial tangential zone of articular cartilage. The stimulation algorithm of both compression and tension without an offset had the best properties out of all the evaluated groups.
Embedded Processor Selection/Performance Estimation Using Fpga-Based Profiling, Fadi Obeidat
Embedded Processor Selection/Performance Estimation Using Fpga-Based Profiling, Fadi Obeidat
Theses and Dissertations
In embedded systems, modeling the performance of the candidate processor architectures is very important to enable the designer to estimate the capability of each architecture against the target application. Considering the large number of available embedded processors, the need has increased for building an infrastructure by which it is possible to estimate the performance of a given application on a given processor with a minimum of time and resources. This dissertation presents a framework that employs the softcore MicroBlaze processor as a reference architecture where FPGA-based profiling is implemented to extract the functional statistics that characterize the target application. Linear …
Synthesis And Characterization Of A Novel Amphiphilic Core-Corona Hyperbranched Polymer, Composed Of Ehmo And Ehmopeg, For Drug Delivery., Khushboo Sharma
Synthesis And Characterization Of A Novel Amphiphilic Core-Corona Hyperbranched Polymer, Composed Of Ehmo And Ehmopeg, For Drug Delivery., Khushboo Sharma
Theses and Dissertations
A novel amphiphilic core-corona hyperbranched polymer, composed of 3-ethyl-3-(hydroxylmethyl) oxetane (EHMO) and PEGylated EHMO (EHMOPEG), was synthesized through cationic ring opening polymerization. Nuclear Magnetic Resonance spectroscopy (NMR), Dynamic Light Scattering (DLS), and Fourier Transform Infrared spectroscopy (FTIR) were used to characterize the polymer structure and degree of branching. It was found that the degree of branching (DOB) of the polymer was affected by the weight % ratios of EHMO/EHMOPEG used in polymerization. As the weight % ratio of EHMO/ EHMOPEG decreased, the DOB was observed to increase. Polymeric particles based on the synthesized polymer were prepared using the O/W (Oil …
Optical Characterization Of Wide Bandgap Detector-Grade Semiconductors, Ezzat Elshazly
Optical Characterization Of Wide Bandgap Detector-Grade Semiconductors, Ezzat Elshazly
Theses and Dissertations
Wide bandgap semiconductors are being widely investigated because they have the potential to satisfy the stringent material requirements of high resolution, room temperature gamma-ray spectrometers. In particular, Cadmium Zinc Telluride (Cd1-xZnxTe, x~0.1) and Thallium Bromide (TlBr), due to their combination of high resistivity, high atomic number and good electron mobility, have became very promising candidates for use in X- and gamma-ray detectors operating at room temperature. In this study, carrier trapping times were measured in CZT and TlBr as a function of temperature and material quality. Carrier lifetimes and tellurium inclusion densities were measured in detector-grade Cadmium Zinc Telluride (CZT) …
Optical Measurement Of Environmental Uranium Using Porous Silica Materials, Chien-Cheng Chen
Optical Measurement Of Environmental Uranium Using Porous Silica Materials, Chien-Cheng Chen
Theses and Dissertations
The focus of this research is on the optical measurement of uranyl in a solid matrix using fluorescence spectroscopy. Nanoporous silica-based materials were used to extract uranyl from contaminated soil and to enhance the fluorescence intensity and lifetime. The fluorescence lifetime and intensity of uranyl ions adsorbed on porous silica-based materials of varying pore size was measured as a function of pH and in the presence of fluoride. The feasibility of uranyl fluorescence detection on the top of soil by silica gel is carried out by four types of natural soil. The results show that the uranyl fluorescence intensity can …
A Comparative Analysis Of Methods For Baseline Drift Removal In Preterm Infant Respiration Signals, Pallavi Ramnarain
A Comparative Analysis Of Methods For Baseline Drift Removal In Preterm Infant Respiration Signals, Pallavi Ramnarain
Theses and Dissertations
Breathing is a vital function intrinsic to the survival of any human being. In preterm infants it is an important indicator of maturation and feeding competency, which is a hallmark for hospital release. The recommended method of measurement of infant respiration is the use of thermistors. Accurate event detection within thermistor generated signals relies heavily upon effective noise reduction, specifically baseline drift removal. Baseline drift originates from several sensor-based factors, including thermistor placement within the sensor and in relation to the infant nares. This work compares four methods for baseline drift removal using the same event detection algorithm. The methods …
Flight Control System For Small High-Performance Uavs, Jefferson Mcbride
Flight Control System For Small High-Performance Uavs, Jefferson Mcbride
Theses and Dissertations
This thesis documents a research project in which an autonomous flight control system (FCS) was designed to control and navigate small, high-speed, unmanned, jet-turbine powered fixed-wing aircraft. The FCS was designed to allow the aircraft to maintain controlled flight, and return to a home location, without any operator intervention. The flight control computer was built with an FPGA, using a Microblaze soft-core microprocessor running the uClinux operating system. The configurable FPGA computing platform allowed flexibility for interfacing quickly with a wide range of sensors and control modules. A commercial inertial measurement unit was used for aircraft state estimation, and the …
The Design And Validation Of A Novel Computational Simulation Of The Leg For The Investigation Of Injury, Disease, And Surgical Treatment, Joseph Iaquinto
The Design And Validation Of A Novel Computational Simulation Of The Leg For The Investigation Of Injury, Disease, And Surgical Treatment, Joseph Iaquinto
Theses and Dissertations
Computational modeling of joints and their function, a developing field, is becoming a significant health and wellness tool of our modern age. Due to familiarity of prior research focused on the lower extremity, a foot and ankle 3D computational model was created to explore the potential for these computational methods. The method of isolating CT scanned tissue and rendering a patient specific anatomy in the digital domain was accomplished by the use of MIMICS™ , SolidWorks™, and COSMOSMotion™ – all available in the commercial domain. The kinematics of the joints are driven solely by anatomically modeled soft tissue applied to …
An Efficient Implementation Of An Exponential Random Number Generator In A Field Programmable Gate Array (Fpga), Smitha Gautham
An Efficient Implementation Of An Exponential Random Number Generator In A Field Programmable Gate Array (Fpga), Smitha Gautham
Theses and Dissertations
Many physical, biological, ecological and behavioral events occur at times and rates that are exponentially distributed. Modeling these systems requires simulators that can accurately generate a large quantity of exponentially distributed random numbers, which is a computationally intensive task. To improve the performance of these simulators, one approach is to move portions of the computationally inefficient simulation tasks from software to custom hardware implemented in Field Programmable Gate Arrays (FPGAs). In this work, we study efficient FPGA implementations of exponentially distributed random number generators to improve simulator performance. Our approach is to generate uniformly distributed random numbers using standard techniques …