Engineering Commons^™

Comparison Of Conventional And Adaptive Acoustic Beamforming Algorithms Using A Tetrahedral Microphone Array In Noisy Environments, Megan Brittany Ewers

Dissertations and Theses

In situ acoustic measurements are often plagued by interfering sound sources that occur within the measurement environment. Both adaptive and conventional beamforming algorithms, when applied to the outputs of a microphone array arranged in a tetrahedral geometry, are able to capture sound sources in desired directions and reject sound from unwanted directions. Adaptive algorithms may be able to measure a desired sound source with greater spatial precision, but require more calculations and, therefore, computational power. A conventional frequency-domain phase-shift algorithm and a modified adaptive frequency-domain Minimum Variance Distortionless Response (MVDR) algorithm were applied to simulated and recorded signals from a …

Real-Time Length Sensing Of Braided Pneumatic Actuator Using Ir Time-Of-Flight Sensor, Luon B. Chung

Dissertations and Theses

Braided Pneumatic Actuators (BPAs) are used widely in robotics as artificial muscles because of their similar characteristics to biological muscles. When a BPA is pressurized, it expands in the radial direction and contracts in the longitudinal direction. The contraction generates a pulling force that is dependent on the input pressure and BPA length. Biological muscle also behaves in the same way where a pulling force is generated on a contraction. To control BPAs on a robot, the real-time pressure and length measurements are necessary. In this dissertation, I present a new method to measure length of BPAs in real-time using …

Developing And Testing Low-Cost Air Cleaners For Safer Spaces During Wildfires, Brett William Stinson

Dissertations and Theses

Air cleaning reduces indoor exposure to fine particulate matter (PM_2.5) during wildfire events. However, resource and cost restraints may limit access to air cleaning during such an event, as both commercial devices and the high-rated MERV filters that homemade assemblies typically rely upon tend to be expensive and in short supply. With these barriers in mind, we sought to develop and evaluate the potential for air cleaners that use common household fabrics as filtration media. Evaluated designs use a box fan to move air across fabric filters; box fans are inexpensive and readily available to many households. Ultimately, …

Surface Roughness Prediction In End Milling Processes Considering The Vibration Of The Cutting Tool, Yubin Lee

Dissertations and Theses

Purpose: Machining is a manufacturing process for making the desired design with dimensional tolerance and surface roughness. Despite the development of engineering technology, predicting machined surface roughness is still challenging since there are various factors, such as material properties, tool material properties, the rigidity of the machine tool, and the use of coolant. In particular, tool vibration is the most critical factor since it makes it challenging to obtain the desired quality of the machined product by unintentionally making a tool move. Therefore, surface finish was explored in this study, considering cutting tool vibration under various axial depth-of-cuts and feed …

Comparing The Performance Of Different Machine Learning Models In The Evaluation Of Solder Joint Fatigue Life Under Thermal Cycling, Jason Scott Ross

Dissertations and Theses

Predicting the reliability of board-level solder joints is a challenging process for the designer because the fatigue life of solder is influenced by a large variety of design parameters and many nonlinear, coupled phenomena. Machine learning has shown promise as a way of predicting the fatigue life of board-level solder joints. In the present work, the performance of various machine learning models to predict the fatigue life of board-level solder joints is discussed. Experimental data from many different solder joint thermal fatigue tests are used to train the different machine learning models. A web-based database for storing, sharing, and uploading …

Effectiveness Of Air Pollution Mitigation Systems: Transport, Transformation, And Control Of Ozone In The Indoor Environment, Pradeep Ramasubramanian

Dissertations and Theses

Buildings are critical environments governing our collective exposure to air pollution and energy consumption. While there exist concerns regarding increases in building energy consumption due to indoor air interventions, improvements to the quality of air indoors can improve health, comfort, and productivity. Air cleaning technologies that can improve indoor air quality with minimal energy consumption have become ever more important. These technologies are utilized at various scales; from passive removal of pollutants in the air entering the indoor environment to active cleaning of air within the breathing zone. To better understand the effectiveness of active and passive ozone mitigation technologies …

The Evaluation Of Performance Of Spindle Connector And Its Finite Element Analysis, Suhyun Lee

Dissertations and Theses

The rapid development of machining technology and reliable high-speed machining systems has led to a fast operation of machines. However, machining machines cannot still meet modern requirements in terms of the quality of parts, the machine components, and the life of the tools. The major components of the machining system are machine tools, the spindle interfaces (the contact between the spindle and the tool holder), and tools. The choice of the spindle connector is the main decision, as this defines the limitation of the metal cutting efficiency and considerably influences the deformation of the machine tool. Therefore, it is very …

The Effect Of Viscosity On The Puddle Dynamics In Low Gravity Environment, Taif Hamed Saleh Al Juboori

Dissertations and Theses

Enormous liquid puddles are observed to jump spontaneously from non-wetting substrates when exposed to the nearly step-reduction in body force common to drop tower test facilities. The phenomenon is similar to the second half of terrestrial drop bounce experiments except that (1) the initial static equilibrium configuration satisfies the static contact angle condition, (2) the initial height of the puddle is limited to the capillary height, and (3), for drop tower test durations on the order of seconds, puddle volumes can be over 10⁴ times larger in mass (volume). The passive puddle jump mechanism provides a no-moving-parts deployment method …

Building A Biomechanical Model Of A Rat Forelimb, Joshua Nathaniel Eric Mak

Dissertations and Theses

This paper presents a biomechanical model of the rat forelimb to test theories of determining viscoelastic muscle parameters. Several biomechanical models of rat hindlimbs have been developed and have explored the effects of multi-muscle control during locomotion. The forelimb model uses two ball-and-socket joints to model clavicle and scapula movement. A third ball-and-socket joint is used at the shoulder and two hinge joints are used at the elbow and wrist. Scapula motion is further constrained by muscle and spring elements. Each forelimb has 11 degrees of freedom, and 23 Hill-type muscles. The model has been created in Animatlab, which includes …

Fixed Bottom Wind Turbine Wave-Wake Interaction, Ondrej Fercak

Dissertations and Theses

The interest and benefits of offshore wind energy has also brought along legitimate design challenges for engineers. Most notably, the complex interaction between wind and turbine is further complicated by the addition of dynamic ocean waves. This dynamic coupling between wind, wave, and turbine is not fully understood. Even small improvements in wind turbine performance are welcome, so characterizing a fundamental dynamic in offshore energy is necessary to optimize design. Experimentation and simulation have been used to characterize inflow and turbine wakes and separately, wind-wave interactions. But only simulations have just begun to look at the wind, wave, and turbine …

Entrainment Processes For A Jet In Cross-Flow: The Quantification Of Turbulent Contributions And Their Importance On Accurate Modeling, Graham Asher Freedland

Dissertations and Theses

A jet in cross flow (JICF) is examined experimentally by injecting a stream of air into crossing fluid with an aim into quantifying entrainment process and downstream evolution. The behavior of JICF is important to fields ranging from turbine-blade cooling to smokestack pollution and volcanic eruption dynamics. Existing simplified volcanic plume models are tested; most importantly, the near-field contributions of complex interconnected vortex systems, which present significant uncertainties because they assume negligible turbulence. While jets in irrotational cross-flow have been investigated, this analysis has focused on the interaction between a turbulent jet in low and highly turbulent cross-flow created by …

Indoor Air Quality Impacts Of A Woodstove Exchange Program In Washington County, Oregon, Matthew Forrest Survilo

Dissertations and Theses

More than six million people in the United States use wood stoves as their primary heat source. Wood stoves emit air pollutants that may impact health, e.g., wood combustion products are associated with premature death and aggravation of pulmonary and cardiovascular conditions. There are few studies investigating the efficacy of wood stove exchange programs (WSEPs) as a method to improve indoor air quality (IAQ). In partnership with Washington County Department of Health and Human Services we conducted an air quality study to measure the impact of a WSEP on indoor and neighborhood levels of wood combustion products. Twenty households engaged …

Dynamic Effects Of Inertial Particles On The Wake Recovery Of A Model Wind Turbine, Sarah E. Smith

Dissertations and Theses

Impacting particles such as rain, dust, and other debris can have devastating structural effects on wind turbines, but little is known about the interaction of such debris within turbine wakes. This study aims to characterize behavior of inertial particles within the turbulent wake of a wind turbine and relative effects on wake recovery. Here a model wind turbine is subjected to varied two-phase inflow conditions, with wind as the carrier fluid (Re_λ = 49 - 88) and polydisperse water droplets (26 to 45µm in diameter) at varied concentrations (Φ_v=0.24 x 10^-5 - 1.3 …

Droplet Ejections During Wet Lab Operations Aboard Spacecraft, Caleb Cushman Turner

Dissertations and Theses

The breakup and rupture of liquid bridges, thin films, bubbles, droplets, rivulets, and jets can produce satellite droplets that are subsequently ejected into their surrounding environment. For example, when any solid object is withdrawn from a liquid bath, the formation of an ever-thinning columnar liquid bridge eventually ruptures along the axis of the bridge. When rupture occurs under typical pipetting conditions the dynamics governing the rupture almost always produce at a minimum a satellite droplet. When these droplets occur they are often too small and too fast to be observed by the human eye. In a terrestrial environment they are …

A Numerical Investigation Of Microgravity Evaporation, Daniel Peter Ringle

Dissertations and Theses

Evaporation is important to myriad engineering processes such as cooling, distillation, thin film deposition, and others. In fact, NASA has renewed interest in using cabin air pressure evaporation as a means to recycle waste water in space. As one example, NASA recently conducted experiments aboard the International Space Station (ISS) to measure evaporation rates in microgravity and to determine the impacts of porous structure on the process. It has long been assumed that differences in evaporation rates between 1-g₀ and microgravity are small. However, discrepancies by as much as 40% have been observed in practice. The assumption now …

Characterization Of Inertial Particles In The Turbulent Wake Of A Porous Disk, Kristin Nichole Travis

Dissertations and Theses

This study presents the findings of a wind tunnel experiment investigating the behaviour of micrometric inertial particles in the turbulent wake of a stationary porous disk. Various concentrations [Φ_v ∈ (2.95 x 10^-6 - 1.22 x 10^-5)] of polydisperse water droplets (diameter 13-41 µm) are compared to sub-inertial tracer particles. Hot-wire anemometry, phase Doppler interferometry and particle image velocimetry were implemented in the near and far wake regions to study the complex dynamics of the particles. Turbulence statistics and particle size distributions are presented and used to explore the particle wake interaction.

The Optimization Of Machining Parameters For Milling Operations By Using The Nelder Mead Simplex Method, Yubin Lee

Dissertations and Theses

Machining operations need to be optimized to maximize profit for computer numerical control (CNC) machines. Although minimum production time could mean high productivity, it can not guarantee maximum profit rate in CNC milling operations. The possible range of machining parameters is limited by several constraints, such as maximum machine power, surface finish requirements, and maximum cutting force for the stability of milling operations. Among CNC machining parameters, cutting speed and feed have the greatest effect on machining operations. Therefore, cutting speed and feed are considered as main process variables to maximize the profit rate of CNC milling operations.

A variety …

Passive Separation Of Binary Fluid Mixtures In Microchannels Using Lattice Boltzmann Method, Mohanad Kamil Radhi

Dissertations and Theses

Fluid mixtures in real life exist in two forms: miscible and immiscible. Separation of these mixtures using chemical agents or thermal energy has both environmental and economic disadvantages. The high cost and the environmental damage caused by the traditional separation techniques have stimulated both academia and industry to seek alternatives. The emergence of microfluidics offers robust solutions for a broad span of transport problems due to the high surface to volume ratio and reduced length scales. Particularly, the separation efficiency increases significantly due to the aforementioned feature. However, there is still a pressing need of passive separations for the sake …

Tracking Center Of Mass With Limited Inertial Measurement Units, Connor Nathaniel Morrow

Dissertations and Theses

Wearable motion tracking systems pose an opportunity to study and correct human balance and posture during movement. Currently, these observations are either being conducted in laboratories with the use of camera systems and markers placed on the body, or through the use of suits containing large numbers (15-20) of inertial measurement units. However, to aid with rehabilitation of individuals with impaired balance, there needs to be an option to collect these observations outside of clinics and without incurring much cost from the user. I have focused on three inertial measurement units, one placed on each shank and one placed on …

Non-Contact Distillation, Rawand Muzafar Rasheed

Dissertations and Theses

Leidenfrost phenomenon has been studied extensively for its role in applications ranging from nuclear reactor cooling, to metals manufacturing, combustion, and other fields. Herein, Leidenfrost phenomenon is pursued towards non-contact distillation processes with hopes of reducing or even eliminating contaminant fouling. In particular, the microgravity environment of a drop tower is exploited to demonstrate the facility with which droplets achieve and sustain the Leidenfrost state. Dynamic Leidenfrost impacts in microgravity are presented for impacts on hydrophilic and superhydrophobic planar substrates, macro-pillar arrays, confined passageways, and others. Nearly ideal elastic non-contact impacts and droplet oscillation modes are observed. Dynamic Leidenfrost impacts …

Design Of A Canine Inspired Quadruped Robot As A Platform For Synthetic Neural Network Control, Cody Warren Scharzenberger

Dissertations and Theses

Legged locomotion is a feat ubiquitous throughout the animal kingdom, but modern robots still fall far short of similar achievements. This paper presents the design of a canine-inspired quadruped robot named DoggyDeux as a platform for synthetic neural network (SNN) research that may be one avenue for robots to attain animal-like agility and adaptability. DoggyDeux features a fully 3D printed frame, 24 braided pneumatic actuators (BPAs) that drive four 3-DOF limbs in antagonistic extensor-flexor pairs, and an electrical system that allows it to respond to commands from a SNN comprised of central pattern generators (CPGs). Compared to the previous version …

Characterizing Tilt Effects On Wind Plants, Ryan Scott

Dissertations and Theses

Tilting the nacelle of a wind turbine modifies entrainment into the wind plant and impacts total efficiency. Extreme angles can produce flying and crashing wakes where the wake either disrupts entertainment from the undisturbed flow above or is decimated on the ground. The effect of tilt angle on downstream wake behavior was investigated in a series of wind tunnel experiments. Scale model turbines with a hub height and diameter of 12 cm were arranged in a Cartesian array comprised of four rows of three turbines each. Nacelle tilt was varied in the third row from -15° to 15° in chosen …

Infinite Photovoltaic Solar Arrays: Considering Flux Of Momentum And Heat Transfer, Andrew D. S. Glick

Dissertations and Theses

Large scale solar farms supply an increasing amount of the worlds electricity supply. However, in order to reach cost parity with fossil fuels, further reductions are necessary. Towards this end, photovoltaic (PV) panel cooling becomes increasingly important; high temperatures both decrease efficiency and panel lifetime. To better understand, characterize, and exploit the natural convective cooling of utility scale solar farms, a model solar farm was created. Using both thermal measurements and particle image velocimetry to characterize heat transfer and velocity fields, wind tunnel experiments were conducted using the model solar farm. Three parameters were examined for their effect on heat …

Fatigue Characteristics Of New Eco Series Aluminum 7175 Alloy, Chinh Q.L. Vu

Dissertations and Theses

In this dissertation, the fatigue characteristics of three newly developed experimental compositions for aluminum 7175, with improved mechanical strength, that uses magnesium-calcium alloy instead of pure magnesium are studied.

Specimens of each variant were fabricated and subjected to fatigue life testing, fatigue life data analysis, and observation of their fracture characteristics through optical microscopy and scanning electron microscopy (SEM), and metallography to study their grains and surface characteristics.

Fatigue life testing shows all three variants have a fatigue strength that is approaching approximately 200 MPa. ECO7175v3 is shown to have the highest fatigue strength of approximately 220 MPa at 5x10 …

A Study Of Thermal Energy Storage Of Phase Change Materials: Thermophysical Properties And Numerical Simulations, Kyung-Eun Min

Dissertations and Theses

A Thermal Energy Storage (TES) system is meant for holding thermal energy in the form of hot or cold materials for later utilization. A TES system is an important technological system in providing energy savings as well as efficient and optimum energy use. The main types of a TES system are sensible heat and latent heat. A latent heat storage is a very efficient method for storing or releasing thermal energy due to its high energy storage density at constant temperatures, and a latent heat storage material can store 5-14 times more heat per unit volume than a sensible heat …

Thermally (Un-) Stratified Wind Plants: Stochastic And Data-Driven Reduced Order Descriptions/Modeling, Naseem Kamil Ali

Dissertations and Theses

Wind energy is one of the significant sources of renewable energy, yet a number of challenges preclude optimal operation of wind plants. Research is warranted in order to minimize the power losses and improve the productivity of wind plants. Here, a framework combining turbulence theory and data mining techniques is built to elucidate physics and mechanisms driving the energy extraction of the wind plants under a number of atmospheric/operating conditions. The performance of wind turbines is subjected to adverse effects caused by wake interactions. Therefore, it is crucial to understand wake-to-wake interactions as well as wake-to-atmospheric boundary layer interactions. Experimental …

Ozone-Surface Exchange And Transport And Transformation Near Ventilation Air Supply, Pradeep Ramasubramanian

Dissertations and Theses

Ozone in indoor environments can pose a health risk to human occupants; around half of exposure to this pollutant occurs inside buildings. One approach to reducing indoor O₃ levels is to mitigate O₃ as it enters a building via outdoor air ventilation supply. Often, mechanical systems that introduce outdoor air into buildings are placed on building rooftops. At the urban scale, greenery has been shown to reduce levels of some harmful pollutants, including ozone and cities like Portland, OR, are mandating green roofs be built on large commercial buildings to increase urban green surfaces. We investigate if rooftop …

Chemo-Thermo Cure Of Viscoelastic Materials For Semiconductor Packaging Applications, Anjali Pradeep Kumar

Dissertations and Theses

Viscoelastic polymer materials are being actively considered as a novel material for semiconductor packaging applications as a result of their ability to develop strong adhesive bonds at lower temperatures. Viscoelastic thermoset materials are impacted by the stresses generated during the curing process, which is also accompanied by a dissipation of thermal energy. There is a need to develop a generic modeling formulation that is applicable to any material of interest in order to enable the study of different bonding materials and develop optimized curing cycles. This study reports a numerical formulation to evaluate the stress generated and energy dissipated during …

Reliability Of Solder Joints In Embedded Packages Using Finite Element Methods, Valeri Aisha Yunusa

Dissertations and Theses

Solder joints serve as both mechanical and electrical connections between elements in a package. They are subjected to shear strains generated as a result of the different behaviors of the elements in the package (tension and compression) due to the differences in coefficients of thermal expansion during service conditions.

Some of the causes of solder joint failures are due to the following:

Vibration: small rapid displacements of parts of the assembly. This is not necessarily an issue with electronic components but larger parts like automobiles.

Humidity: the package being exposed to water or ionic species can undergo corrosion if an …

Emulating Balance Control Observed In Human Test Subjects With A Neural Network, Wade William Hilts

Dissertations and Theses

Human balance control is a complex feedback system that must be adaptable and robust in an infinitely varying external environment. It is probable that there are many concurrent control loops occurring in the central nervous system that achieve stability for a variety of postural perturbations. Though many engineering models of human balance control have been tested, no models of how these controllers might operate within the nervous system have yet been developed. We have focused on building a model of a proprioceptive feedback loop with simulated neurons. The proprioceptive referenced portion of human balance control has been successfully modeled by …