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Multi-Physical Study Of Mems Resonators And Oscillators, Xiaobo Guo

Electronic Theses and Dissertations

First, this research presents experimental and theoretical investigation of the response of micro scale dual-plate thermal-piezoresistive resonators (TPR) and self-sustained oscillators (TPO) to different gases and pressures. It is demonstrated that the resonant frequency of such devices follows particular trends in response to the changes in the surrounding gas and its pressure. A mathematical model has been derived to explain the damping dependent frequency shift characteristic of TPO. The solution of the model indicates that the stiffness of the actuator beam decreases as the value of damping coefficient drops at lower gas density caused by the change in the gas …

Evaluation Of Novel High-Density Emg Feedback Parameters On The Spatial Distribution Of Trapezius Muscle Activity, Brecca M. Gaffney

Electronic Theses and Dissertations

Each year, 17.9% of adults working in a computer-dominated work environment develop an episode of chronic neck and shoulder pain. An effective treatment method for chronic pain is postural correction through therapist. The understanding of the relation between cervicoscapular posture and trapezius muscle activity is not fully understood because the anatomy of the scapula is not accessible for direct observation. Until recently, the spatial distribution of trapezius muscle activity could not be measured due to the limitation in size of detection zone in traditional bipolar electrodes. The primary goal of postural correction when treating cases of chronic neck and shoulder …

An Efficient Navigation-Control System For Small Unmanned Aircraft, Jonathan Alejandro Girwar-Nath

Electronic Theses and Dissertations

Unmanned Aerial Vehicles have been research in the past decade for a broad range of tasks and application domains such as search and rescue, reconnaissance, traffic control, pipe line inspections, surveillance, border patrol, and communication bridging.

This work describes the design and implementation of a lightweight Commercial-Off-The-Shelf (COTS) semi-autonomous Fixed-Wing Unmanned Aerial Vehicle (UAV). Presented here is a methodology for System Identification utilizing the Box-Jenkins model estimator on recorded flight data to characterize the system and develop a mathematical model of the aircraft. Additionally, a novel microprocessor, the XMOS, is utilized to navigate and maneuver the aircraft utilizing a PD …

Galvanic Corrosion Of High-Temperature Low-Sag (Htls) High Voltage Conductors: New Materials—New Challenges, Eva Håkansson

Electronic Theses and Dissertations

High-Temperature Low-Sag (HTLS) high voltage overhead conductors offer higher operating temperatures, reduced resistance and less sag than conventional designs. With up to twice the current capacity for the same diameter conductor, they may help ease the power shortage in the constantly increasing electricity demand, but there might be some concerns about their corrosion resistance.

These new conductors use materials relatively new to the power industry, such as advanced carbon fiber polymer matrix composites and unique metal matrix composites/nano-composites predominantly used in aerospace industries. This study has made an initial assessment of potential galvanic corrosion problems in three very different HTLS …

Representing Intersubject Variability With A Statistical Shape And Alignment Model Of The Knee, Chandreshwar Rao

Electronic Theses and Dissertations

Prior statistical shape models have not considered multiple structures in the knee joint to characterize anatomic variation which are required to investigate joint mechanics further for the successful knee replacement. Accordingly, the study's objective was to develop statistical shape and alignment model (SSAM) to capture intersubject variability and demonstrate the ability to generate realistic instances for use in finite element analysis (FEA). SSAM described the variability in the training set of 20 subjects with a series of modes of variation obtained by performing principal component analysis (PCA). PCA produced modes of variation with the first 3 modes representing 70% and …

Cavitation In Pharmaceutical Manufacturing And Shipping, Donn Sederstrom

Electronic Theses and Dissertations

Therapeutic proteins are used to successfully treat hemophilia, Crohn's Disease, diabetes, and cancer. Recent product recalls have occurred because of sub-visible particle formation resulting from the inherent instability of proteins. It has been suggested that particle formation is associated with late stage processing steps of filling, shipping, and delivery. Previous work at the University of Denver demonstrated that fluid cavitation can generate a large number of sub-visible protein particles in ultra clean formulations, but that mitigation can be achieved with fluid property manipulation. The goal of this research was to (1) assess the risk of cavitation under common pharmaceutical manufacturing …

Generalizable Methods For Modeling Lumbar Spine Kinematics, Craig Joseph Simons

Electronic Theses and Dissertations

A more complete understanding of lumbar spine kinematics could improve diagnoses and treatment of low back pathologies and may advance the development of biomechanical models. Kinematics describes motion of the five lumbar vertebrae without consideration for the forces that cause the motion. Despite considerable attention from researchers and clinicians, lumbar spine kinematics are not fully understood because the anatomy is not accessible for direct observation and the complex governing biomechanics produce small magnitude, coupled intervertebral movements.

The overall goal of this project was to develop a descriptive model of intervertebral lumbar spine kinematics that is applicable to a generalizable subject …

Finite Element Analysis Of Thermomechanical Processes In Disk Clutch Systems, Zhuo Chen

Electronic Theses and Dissertations

The engagement of clutch system is a typical dynamic coupled temperature-displacement process which contains two or more sliding surfaces involved in frictional contact. This process influences evidently the thermal fatigue, noise and vibration of the clutch system. This effect can be more remarkable if the temperature distribution over the clutch disk is not uniform.

This thesis is organized into five chapters:

The first chapter is an introduction which reviews the background and previous work of thermoelastic instability and finite element analysis of clutch system and disk brake.

A parametric analysis of TEI (thermoelastic instability) is elaborated in the second chapter. …

Towards A Fluid Solid Interaction Model Of A Dynamic Lung, Justin C. Jacobs

Electronic Theses and Dissertations

Because the pulmonary system is a site for both environmental particulate contamination, as well as drug delivery into the body, numerous research groups have focused on precisely understanding its inner-workings. Past research has demonstrated the need to realistically model the lung walls in order to accurately capture the complex airflow profile throughout all of the branches. Since this is paramount to properly replicating particulate transport in the lung, computational fluid dynamics simulations on their own are inadequate, as they cannot account for lung wall dilation. Only by coupling the fluid and solid domains can natural lung behavior can be effectively …

Computationally Efficient Finite Element Models Of The Lumbar Spine For The Evaluation Of Spine Mechanics And Device Performance, Sean D. Smith

Electronic Theses and Dissertations

Finite Element models of the lumbar spine are commonly used for the study of spine mechanics and device performance, but have limited usefulness in some applications such as clinical and design phase assessments due to long analysis times. In this study a computationally efficient L4-L5 FSU model and a L1-Sacrum multi-segment model were developed and validated. The FSU is a functional spine unit consisting of two adjacent vertebral bodies, in this case L4 and L5. The multi-segment model consists of all lumbar vertebrae and the sacrum. The models are able to accurately predict spine kinematics with significantly reduced analysis times, …

Explicit Finite Element Modeling Of The Human Lumbar Spine, Milind Rao

Electronic Theses and Dissertations

Validated finite element (FE) models of the functional spinal unit (FSU) and lumbar spine are essential in design-phase device development and in assessing the mechanics associated with normal spine function and degenerative disc disease (DDD), as well as the impact of fusion and total disc replacement (TDR). Although experimental data from fully intact specimens can be used for model calibration and validation, the contributions from the individual structures (disc, facets, and ligaments) may be inappropriately distributed. Hence, creation of decompression conditions or device implantations that require structure removal may not have the proper resulting mechanics. An explicit FE formulation may …

Feature-Based Neuro-Symbolic Networks For Global Diagnostics, Tracy Lynn Schantz

Electronic Theses and Dissertations

Engineered system diagnostics have been researched over the years with many successful results. From transportation systems to office technologies, many have been equipped with self-diagnostic capabilities and are called Smart Machines. In spite of these advances, current diagnostic systems are driven by direct sensory information without much concern for patterns of the system behavior or features associated with them. For large-scale systems with complex dynamics, global as well as local diagnostics become of great importance, where sensory information is used as input for the local diagnostics, and patterns of behavior or features are utilized for global diagnostics.

The main objective …

Micro Channel Cooler Performance Improvement By Insonation, Peter Webb Higgins

Electronic Theses and Dissertations

The motivation for this work is the need to remove waste heat from laser diodes and high speed transistors in processes which are exponentially increasing past 1 kW/cm2 as anticipated by Moore's Law. The hypothesis guiding the work is that ultrasonic insonation of micro coolers employed to dissipate these heat loads can improve heat removal. It is thought that the mechanism promoting the benefit is enhancement of the ability of the coolant to remove latent heat in two-phase operation by managing entrained bubble size near the cooler's exit so as to forestall flow reduction or blockage caused by large bubbles, …

Fatigue Testing And Computational Analysis Of A Spinal Implant, Timothy Helton

Electronic Theses and Dissertations

The following study investigates the fatigue behavior of a spinal implant developed by Synthes, Inc. to provide stability and off load pressure from the discs in the lumbar region. The installation process for the StenoFix design utilizes plastic deformations to customize the device to each individual patient, but also has potential to degrade fatigue behavior. Physical testing of two titanium alloys, Ti-6Al-7Nb and Ti-15Mo, was conducted on hydraulic test frames and compared to computational simulations which were carried out for the following scenarios: cyclic excitation following plastic deformation; variation of material property definition; variation of loading location; and three modifications …

An Integrated Platform To Increase The Range/Endurance Of Unmanned Helicopters, Roy Godzdanker

Electronic Theses and Dissertations

Class I (kg) autonomous helicopters are becoming increasingly popular for a wide range of non-military applications such as, surveillance, reconnaissance, traffic monitoring, emergency response, agricultural spraying, and many other "eye in the sky" missions. However, an efficient landing/takeoff platform with refueling/recharging capabilities has not yet been developed to increase the endurance and decrease the cost for Class I helicopters.

This dissertation presents a three-prong approach for increasing the range and endurance of Class I autonomous helicopters, which will then spur demand by non-military organizations wanting to take advantage of such capabilities and, therefore, drop their price. The proposed Intelligent Self-Leveling …

High Frequency Thermally Actuated Single Crystalline Silicon Micromechanical Resonators With Piezoresistive Readout, Amir Rahafrooz

Electronic Theses and Dissertations

Over the past decades there has been a great deal of research on developing high frequency micromechanical resonators. As the two most common and conventional MEMS resonators, piezoelectric and electrostatic resonators have been at the center of attention despite having some drawbacks. Piezoelectric resonators provide low impedances that make them compatible with other low impedance electronic components, however they have low quality factors and complicated fabrication processes. In case of electrostatic resonators, they have higher quality factors but the need for smaller transductions gaps complicates their fabrication process and causes squeezed film damping in Air. In addition, the operation of …

Label-Free Biochemical Recognition Using Mems Resonators For Microarray Technology, Babak Tousifar

Electronic Theses and Dissertations

Highly sensitive biosensors capable of detecting and characterizing smallest quantities of cellular and molecular targets are needed in pharmaceutical and medical diagnostics industries. In this work, the importance of biological target recognition specifically proteins through microarray technologies has been discussed and the most successful tools and techniques have been studied. Moreover, a thermally actuated Micro Electro-Mechanical Systems (MEMS) resonator has been demonstrated and fabricated in this work as an accurate, reliable and low cost biotechnology tool. As a proof of concept, amine to epoxide coupling of octadecylamine to functionalized silicon dioxide surface have been shown through resonator frequency monitoring. The …

Computational Fluid Dynamic Optimization And Design For The Airborne Laser System, Matthew James Opgenorth

Electronic Theses and Dissertations

The Airborne Laser (ABL) was designed to destroy any ballistic missile shortly after launch that could be a threat to the United States and its allies. The ABL uses several lasers to accomplish the destruction of the ballistic missile, most notably the high powered Chemical Oxygen Iodine Laser (COIL). The COIL is a complex device that could be improved upon in several areas that will result in overall weight reduction, refinement of beam quality, and increased magazine capacity.

This dissertation presents novel design and optimization techniques coupled with fluid dynamics to improve the performance of the COIL system. The focus …

Fuzzy Optimal Swarm Of Autonomous Aircrafts For Target Determination And Convergence Control System, Zach D. Richards

Electronic Theses and Dissertations

The thesis project proposes analytical and theoretical algorithms for a networked swarm of autonomous vehicles, such as those used in planet exploration, and to be used in target location determination and convergence, an algorithm of this type could be used in an Autonomous Stratospheric Aircraft (ASA), thus having the possibility of being used for the exploration of a planet as well as many other applications. Upon locating an unknown location of a specified target, the algorithm would then swarm and eventually converge upon the location. There are two similar, but fundamentally different algorithms proposed in this project. These algorithms are …

Heterogeneous Drive Mechanisms For Novel Locomotion In Rough Terrain, Roy Godzdanker

Electronic Theses and Dissertations

The smaller the robot the easier it is for it to access voids in a collapsed structure, however small size brings a host of other problems related to constrained resources. One of the primary constraints on small robots is limited motive power to surmount obstacles and navigate rough terrain. This thesis examines the addition of bulk motive force actuators to existing locomotion platforms and the impact of these heterogeneous actuators on conventional steering methods. The steering methods examined are those associated with skid steered vehicles and differential drive vehicles. In developing the Crabinator, a robot composed of a limbed crawler …

Explicit Finite Element Modeling Of Knee Mechanics During Simulated Dynamic Activities, Mark A. Baldwin

Electronic Theses and Dissertations

The natural knee is one of the most commonly injured joints in the body due to relatively high loads and motions that can lead to debilitating degenerative diseases such as osteoarthritis. Total knee arthroplasty is a clinically successful method for eliminating pain in the osteoarthritic knee, but is subject to complications that can affect patient satisfaction and long-term implant performance. The work presented in this dissertation is a demonstration of how anatomic three-dimensional (3D) computational knee models can be an effective alternative for investigating knee mechanics when compared to the cost and time prohibitive nature of in-vivo and in-vitro methods. …

Computational Studies On The Effective Properties Of Two-Phase Heterogeneous Media, Elyas El Arbi Tawerghi

Electronic Theses and Dissertations

The effective elastic modulus and conductivity of a two phase material system are investigated computationally using a Monte Carlo scheme. The continuum contains circular, spherical or ellipsoidal inclusions that are either uniformly or randomly embedded in the matrix. The computed results are compared to the applicable effective medium theories. It is found that the random distribution, permeability and particle aspect ratio have non-negligible effects on the effective material properties. For spherical inclusions, the effective medium approximations agree well with the simulation results in general, but the analytical predictions on void or non-spherical inclusions are much less reliable. It is found …