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2019

University of Colorado, Boulder

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Articles 1 - 30 of 69

Full-Text Articles in Engineering

Optical Properties And Mechanical Modeling Of Acetylated Transparent Wood Composite Laminates, Kyle E. O. Foster, Kristen Hess, Garret M. Miyake Phd, Wil V. Srubar Phd Jul 2019

Optical Properties And Mechanical Modeling Of Acetylated Transparent Wood Composite Laminates, Kyle E. O. Foster, Kristen Hess, Garret M. Miyake Phd, Wil V. Srubar Phd

University Libraries Open Access Fund Supported Publications

Transparent wood composites (TWCs) are a new class of light-transmitting wood-based materials composed of a delignified wood template that is infiltrated with a refractive- index-matched polymer resin. Recent research has focused primarily on the fabrication and characterization of single-ply TWCs. However, multi-ply composite laminates are of interest due to the mechanical advantages they impart compared to the single ply. In this work, 1- and 2-ply [0 ◦ /90 ◦ ] TWC laminates were fabricated using a delignified wood template (C) and an acetylated delignified wood template (AC). The optical and mechanical properties of resultant C and AC TWC laminates were determined using ultraviolet-visible ...


Toward Environmentally Sustainable Digital Preservation, Keith L. Pendergrass, William Sampson, Tim Walsh, Laura Alagna Jun 2019

Toward Environmentally Sustainable Digital Preservation, Keith L. Pendergrass, William Sampson, Tim Walsh, Laura Alagna

University Libraries Faculty & Staff Contributions

Digital preservation relies on technological infrastructure (information and communication technology, ICT) that has considerable negative environmental impacts, which in turn threaten the very organizations tasked with preserving digital content. While altering technology use can reduce the impact of digital preservation practices, this alone is not a strategy for sustainable practice. Moving toward environmentally sustainable digital preservation requires critically examining the motivations and assumptions that shape current practice. Building on Goldman's challenge to current practices for digital authenticity and using Ehrenfeld's sustainability framework, we propose explicitly integrating environmental sustainability into digital preservation practice by shifting cultural heritage professionals' paradigm ...


Design, Development, And Prelaunch Calibration Of A Low Cost 118.75 Ghz Temperature Sounding Radiometer For Cubesat Missions, Lavanya Periasamy May 2019

Design, Development, And Prelaunch Calibration Of A Low Cost 118.75 Ghz Temperature Sounding Radiometer For Cubesat Missions, Lavanya Periasamy

Electrical Engineering Graduate Theses & Dissertations

The 118.75 GHz eight-channel, double-side-band scanning temperature sounding radiometer “MiniRad” for CubeSat missions is intended to serve as a demonstrator for a constellation of low cost, quick turn-around millimeter wave and higher frequency passive sounders and imagers for weather forecasting at high spatial and temporal resolution. This radiometer payload, built at the Center for Environmental Technology in partnership with the Colorado Space Grant Consortium and the National Snow and Ice Data Center at the University of Colorado at Boulder, can provide a 3D temperature map from the earth's surface to an altitude of 18~km. For precise prelaunch ...


Social And Environmental Neighborhood Typologies And Lung Function In A Low-Income, Urban Population, Shelly L. Miller Mar 2019

Social And Environmental Neighborhood Typologies And Lung Function In A Low-Income, Urban Population, Shelly L. Miller

Mechanical Engineering Faculty Contributions

Abstract: Consensus is growing on the need to investigate the joint impact of neighborhood-level social factors and environmental hazards on respiratory health. This study used latent profile analysis (LPA) to empirically identify distinct neighborhood subtypes according to a clustering of social factors and environmental hazards, and to examine whether those subtypes are associated with lung function. The study included 182 low-income participants who were enrolled in the Colorado Home Energy Efficiency and Respiratory Health (CHEER) study during the years 2015–2017. Distinct neighborhood typologies were identified based on analyses of 632 census tracts in the Denver-Metro and Front Range area ...


Understanding Female-Focused Hackathon Participants’ Collaboration Styles And Event Goals, Brittany Ann Kos Mar 2019

Understanding Female-Focused Hackathon Participants’ Collaboration Styles And Event Goals, Brittany Ann Kos

ATLAS Institute Graduate Contributions

Collegiate hackathons are informal learning environments where students build new projects in a limited amount of time and often compete for prizes. Previous hackathon research has shown that students go to these events to learn new technical skills, work on projects with friends, or network with the technical community; however, little is known about the different ways in which students collaborate with other participants and how students’ event goals affect their trajectory at the hackathon. In the literature, students are typically described as working in competitive teams that build one project to be entered into a competition. However, there are ...


Ice-Binding Protein From Shewanella Frigidimarinas Inhibits Ice Crystal Growth In Highly Alkaline Solutions, Elizabeth Delesky, Shane D. Frazier, Jaqueline D. Wallat, Kendra L. Bannister, Chelsea Marie Heveran, Wil V. Srubar Iii Feb 2019

Ice-Binding Protein From Shewanella Frigidimarinas Inhibits Ice Crystal Growth In Highly Alkaline Solutions, Elizabeth Delesky, Shane D. Frazier, Jaqueline D. Wallat, Kendra L. Bannister, Chelsea Marie Heveran, Wil V. Srubar Iii

University Libraries Open Access Fund Supported Publications

The ability of a natural ice-binding protein from Shewanella frigidimarina (SfIBP) to inhibit ice crystal growth in highly alkaline solutions with increasing pH and ionic strength was investigated in this work. The purity of isolated SfIBP was first confirmed via sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and size-exclusion chromatography with an ultraviolet detector (SEC-UV). Protein stability was evaluated in the alkaline solutions using circular dichroism spectroscopy, SEC-UV, and SDS-PAGE. SfIBP ice recrystallization inhibition (IRI) activity, a measure of ice crystal growth inhibition, was assessed using a modified splat assay. Statistical analysis of results substantiated that, despite partial denaturation and ...


Coaxial Pcl/Peg-Thiol-Ene Microfiber With Tunable Physico- Chemical Properties For Regenerative Scaffolds, Monica Cristina Iglesias Echevarria Jan 2019

Coaxial Pcl/Peg-Thiol-Ene Microfiber With Tunable Physico- Chemical Properties For Regenerative Scaffolds, Monica Cristina Iglesias Echevarria

Mechanical Engineering Graduate Theses & Dissertations

Tissue regeneration requires scaffolds that exhibit mechanical properties similar to the tissues to be replaced while allowing cell infiltration and extracellular matrix production. Ideally, the scaffolds’ porous architecture and physico-chemical properties can be precisely defined to address regenerative needs. We thus developed techniques to produce hybrid fibers coaxially structured with a polycaprolactone core and a 4-arm, polyethylene glycol thiol-norbornene sheath. We assessed the respective effects of crosslink density and sheath polymer size on the scaffold architecture, physical and mechanical properties, as well as cell-scaffold interactions in vitro and in vivo. All scaffolds displayed high elasticity, swelling and strength, mimicking soft ...


Blebbing Of Hydrogel During Volume-Phase Transition, Jian Kan Jan 2019

Blebbing Of Hydrogel During Volume-Phase Transition, Jian Kan

Mechanical Engineering Graduate Theses & Dissertations

Hydrogels are networks of polymer chains that are capable of absorbing solvent to become gel-like elastomeric materials. One common observation is the formation of patterns on the stimuli-sensitive gel during the phase transition from swollen to shrunk phase. Our research investigates the mechanics behind gel blebbing; when a temperature-sensitive hydrogel encounters a sudden temperature change, multiple ballon-like bubbles can be seen forming on the gel surface during its shrinking phase. The previous researches established that the surface patterns are the result of an impermeable membrane forming on the surface, creating a surface layer which traps the solvent inside and causing ...


Diagnostics And Selective Nano-Therapeutics To Combat Multidrug-Resistant Bacteria, Partha Pratim Chowdhury Jan 2019

Diagnostics And Selective Nano-Therapeutics To Combat Multidrug-Resistant Bacteria, Partha Pratim Chowdhury

Chemical & Biological Engineering Graduate Theses & Dissertations

Due to extensive use of antibiotics various strains multidrug resistant bacteria are emerging rapidly. In USA alone according to CDC report 2013 more than 2 million is affected by these strains of multidrug resistant bacteria causing several deaths. Hence an effective way of diagnostics and therapeutics need to be designed which can successfully combat the menace of

multidrug drug resistant bacteria.

In the present thesis, we discuss about novel strategies for both diagnostics and therapeutics for multidrug resistant bacteria. In the 1st chapter we discuss a novel DNA sequencing technique utilizing purely optical spectroscopy techniques like surface enhanced Raman and ...


Computational Protein Design For Peptide-Directed Bioconjugation, Joseph Gabriel Plaks Jan 2019

Computational Protein Design For Peptide-Directed Bioconjugation, Joseph Gabriel Plaks

Chemical & Biological Engineering Graduate Theses & Dissertations

Proteins enable living organisms to perform many of their critical functions, having been applied over evolutionary time to solve problems of overwhelming diversity and complexity. Protein engineering seeks to deploy these versatile molecules in addressing problems of human concern and would benefit from innovations that improve protein utilization in unnatural environments as well as from increased predictive capability in protein design.

Bioconjugation facilitates the use of proteins in unnatural environments by permitting the attachment of molecules, such as polymers, that can modulate protein stability, solubility, and activity and by mediating protein immobilization. We initially explored this propensity of bioconjugation by ...


Atomic Layer Deposition For Fabrication Of Advanced Polymer Electrolyte Membrane Fuel Cell Catalysts, William Wilson Mcneary Jan 2019

Atomic Layer Deposition For Fabrication Of Advanced Polymer Electrolyte Membrane Fuel Cell Catalysts, William Wilson Mcneary

Chemical & Biological Engineering Graduate Theses & Dissertations

Polymer electrolyte membrane fuel cells (PEMFCs) are highly-efficient devices that convert the chemical energy stored in hydrogen and oxygen into electricity. The commercialization of this technology is hindered by the use of platinum metal to catalyze the oxygen reduction reaction (ORR) on the cathode. In this work, atomic layer deposition (ALD) was applied to the fabrication of PEMFC catalysts in order to improve the utilization of Pt in the ORR as well as the stability of the catalytic Pt nanoparticles over voltage cycling.

Nanostructures of TiO2 were added via ALD to carbon-supported Pt catalysts (Pt/C) in order to ...


Decision Making Protocol In Autonomous Vehicles For Optimal Routing And Safe Control, Lakhan Shiva Kamireddy Jan 2019

Decision Making Protocol In Autonomous Vehicles For Optimal Routing And Safe Control, Lakhan Shiva Kamireddy

Electrical Engineering Graduate Theses & Dissertations

We analyze two significant decision-making problems namely planning and control in an autonomous driving scenario with an objective of not only improving the safety of drives but also enhancing the vehicle’s capability to make better decisions. We model the decision-making problem of routing in autonomous vehicles and solve for an optimal route when a vehicle approaches an intersection. The proposed solution attempts to balance the congestion in the traffic network, considering the selfish nature of the vehicles. We also analyze decision-making at the level of control and communications. The choices of the framework we use, to model the communication ...


Simultaneous Transmit And Receive (Star) Antennas For Geo-Satellites And Shared-Antenna Platforms, Elie Germain Tianang Jan 2019

Simultaneous Transmit And Receive (Star) Antennas For Geo-Satellites And Shared-Antenna Platforms, Elie Germain Tianang

Electrical Engineering Graduate Theses & Dissertations

This thesis presents the analysis, design, and experimental characterization of antenna systems considered for shipborne, airborne, and space platforms. These antennas are innovated to enable Simultaneous Transmit and Receive (STAR) at same time and polarization, either at the same, or duplex frequencies. In airborne and shipborne platforms, developed antenna architectures may enhance the capabilities of modern electronic warfare systems by enabling concurrent electronic attack and electronic support operations. In space, and more precisely at geostationary orbit, designed antennas aim to decrease the complexity of conventional phased array systems, thereby increasing their capabilities and attractiveness. All antennas researched are first designed ...


Design And Analysis Of A Sic Based Fixed Ratio Dc-Dc Transformer, Shankari B. Ramnath Jan 2019

Design And Analysis Of A Sic Based Fixed Ratio Dc-Dc Transformer, Shankari B. Ramnath

Electrical Engineering Graduate Theses & Dissertations

Dual active bridge (DAB) converters can achieve high efficiencies due to their ability to operate with soft switching. The efficiency of DAB is the highest when its conversion ratio is close to the transformer turns ratio as the inductor current is trapezoidal at this operating point and hence the magnitude of rms currents in the circuit are lower which reduces the losses. Hence, with proper design the dual active bridge can operate with trapezoidal inductor current waveform and zero voltage switching (ZVS) of all its switching devices which will lead to high efficiencies of the DAB. The objective of this ...


Vestibular Perceptual Thresholds In Pitch Tilt, Kadambari Suri Jan 2019

Vestibular Perceptual Thresholds In Pitch Tilt, Kadambari Suri

Aerospace Engineering Sciences Graduate Theses & Dissertations

Vestibular perceptual thresholds quantify how small of a self-motion a human is able to perceive as one direction versus the other reliably. A sensitive measure of vestibular function, thresholds have direct functional relevance.

While thresholds in translation and rotation have been extensively characterized and variation in thresholds between different axes (e.g., up/down vs. left/right) established there had been limited investigation of tilt thresholds in different axes using modern psychophysical techniques. Therefore, in phase 1 of this study, we quantify pitch tilt thresholds and compare to those in roll tilt in the same group of subjects, across a ...


The Effect Of Ocean Waves On Airborne Lidar Bathymetry, Bryce Howell Garby Jan 2019

The Effect Of Ocean Waves On Airborne Lidar Bathymetry, Bryce Howell Garby

Aerospace Engineering Sciences Graduate Theses & Dissertations

Airborne lidar bathymetry, or ALB, is an active remote sensing technique capable of filling the need for topographical maps of coastal regions and other regions of shallow water. Modern ALB systems can quickly generate expansive, accurate, and high-resolution bathymetric point clouds. One of the main remaining factors limiting these systems is the effect of waves on the water surface.

This thesis focuses on the development of a comprehensive model to describe interaction between the ocean surface and a bathymetric lidar. The model is able to simulate received lidar signals for varying surface conditions and angles of incidence. From this, uncertainties ...


Standard And Inception-Based Encoder-Decoder Neural Networks For Predicting The Solution Convergence Of Design Optimization Algorithms, Nathanial James O'Neill Jan 2019

Standard And Inception-Based Encoder-Decoder Neural Networks For Predicting The Solution Convergence Of Design Optimization Algorithms, Nathanial James O'Neill

Aerospace Engineering Sciences Graduate Theses & Dissertations

The goal of this work is to investigate the ways in which the capabilities of machine learning algorithms, specifically those of neural networks, can be leveraged to enhance the performance of design optimization algorithms -- specifically those of topology optimization.

A recent boom of interest in design optimization has occurred, coinciding with the arrival and development of advanced manufacturing techniques (such as 3D printing and additive manufacturing) which are compatible with the designs generated by these algorithms. Neural networks have seen an even larger boom in interest and development for their ability to act as ``universal function generators;" in other words ...


Feasibility And Analysis Of A Hybrid Spacesuit Architecture For Planetary Surface Exploration, Roger Huerta I Lluch Jan 2019

Feasibility And Analysis Of A Hybrid Spacesuit Architecture For Planetary Surface Exploration, Roger Huerta I Lluch

Aerospace Engineering Sciences Graduate Theses & Dissertations

This Thesis presents a novel hybrid spacesuit architecture concept to enable planetary exploration by combining mechanical counterpressure (MCP) with gas-pressurization (GP). This conceptual design has the potential to offer a quantifiable increase in mobility, increases in safety through pressure layer redundancy, and decreased pre-breathe time to improve operational efficiency.

The Thesis performs an engineering study on the concept. First, to assess the feasibility and benefit of implementing two separate pressure layers in the spacesuit, a trade analysis of the design space was performed by numerically modelling different spacesuit-related parameters. The analysis is done considering the combined system performance across different ...


Advanced Load Modulated Power Amplifier Architectures, Prathamesh Hirachandra Pednekar Jan 2019

Advanced Load Modulated Power Amplifier Architectures, Prathamesh Hirachandra Pednekar

Electrical, Computer & Energy Engineering Graduate Theses & Dissertations

Power amplifier (PA) applications increasingly require wideband linear operation, such as in carrier aggregation, high-data rate communications as well as several other RF systems including radar, RFID, RF sensing, imaging etc. Additionally, the high peak to average power ratio (PAPR) signals of modern communications systems require operation over a wide dynamic range. Both bandwidth and linearity requirements are at odds with efficiency in conventional amplifier design. As a result, PA design with a simultaneous wideband operation, linearity, and energy efficiency has been a longstanding challenge.

This thesis presents several advanced Load Modulated Balanced Amplifier (LMBA) architectures with a common goal ...


Design, Development, And Prelaunch Calibration Of A Low Cost 118.75 Ghz Temperature Sounding Radiometer For Cubesat Missions, Lavanya Periasamy Jan 2019

Design, Development, And Prelaunch Calibration Of A Low Cost 118.75 Ghz Temperature Sounding Radiometer For Cubesat Missions, Lavanya Periasamy

Electrical, Computer & Energy Engineering Graduate Theses & Dissertations

The 118.75 GHz eight-channel, double-side-band scanning temperature sounding radiometer “MiniRad” for CubeSat missions is intended to serve as a demonstrator for a constellation of low cost, quick turn-around millimeter wave and higher frequency passive sounders and imagers for weather forecasting at high spatial and temporal resolution. This radiometer payload, built at the Center for Environmental Technology in partnership with the Colorado Space Grant Consortium and the National Snow and Ice Data Center at the University of Colorado at Boulder, can provide a 3D temperature map from the earth's surface to an altitude of 18~km. For precise prelaunch ...


Combination Of Geodetic Data Over The Antarctic Ice Sheet For Monthly Mass Variation Solutions, Ryan A. Hardy Jan 2019

Combination Of Geodetic Data Over The Antarctic Ice Sheet For Monthly Mass Variation Solutions, Ryan A. Hardy

Aerospace Engineering Sciences Graduate Theses & Dissertations

This work presents methods for combining time-variable gravimetry, altimetry, and GNSS bedrock motion data to distinguish sources of mass change in Antarctica with enhanced spatial resolution. GRACE gravimetry provided direct measurements of mass variation of the Antarctic Ice Sheet at monthly timescales between 2002 and 2017, but was limited to a spatial resolution of ~300 km. Laser altimetry from ICESat (2003-2009) provided elevation change measurements at fine spatial resolution, better resolving the spatially concentrated sources of Antarctic mass loss, but with sparse temporal sampling. The processes of glacial isostatic adjustment (GIA), ice dynamics, surface mass balance, and firn compaction affect ...


Analysis Of Gnss-R Observations For Altimetry And Characterization Of Earth Surfaces, Jake Robert Mashburn Jan 2019

Analysis Of Gnss-R Observations For Altimetry And Characterization Of Earth Surfaces, Jake Robert Mashburn

Aerospace Engineering Sciences Graduate Theses & Dissertations

Global Navigation Satellite Systems (GNSS) provide abundant, opportunistic signals that can be used to probe the Earth’s environment and surface. Utilizing reflected GNSS signals for remote sensing is called GNSS Reflectometry (GNSS-R). Sensing of the ocean, land, and ice, with potentially dense measurement coverage and rapid revisit times, is possible due to the distributed geometry of GNSS constellations. GNSS-R can provide some advantages over other Earth observation systems, like traditional radar altimeters or microwave radiometers. GNSS signals are well characterized and encoded with precise ranging and timing information. There are multiple transmitters in view at any time, and GNSS ...


Level-Set-Xfem-Density Topology Optimization Of Active Structures: Methods And Applications, Markus Josef Geiss Jan 2019

Level-Set-Xfem-Density Topology Optimization Of Active Structures: Methods And Applications, Markus Josef Geiss

Aerospace Engineering Sciences Graduate Theses & Dissertations

To unlock the potential of advanced manufacturing technologies like additive manufacturing, an inherent need for sophisticated design tools exists. In this thesis, a systematic approach for designing printed active structures using a combined level-set (LS) extended finite element (XFEM) density topology optimization (TO) scheme is developed. This combined scheme alleviates the downsides of both LS and density based TO approaches while building upon the advantages of either method. Thus, a superior design optimization approach is created, which, when coupled with the XFEM, yields a highly accurate physical modeling method. The unique capabilities of this combined approach include hole nucleation and ...


Capacity Approximations Of Mimo Interference Channels: Beyond Degrees Of Freedom, Yimin Pang Jan 2019

Capacity Approximations Of Mimo Interference Channels: Beyond Degrees Of Freedom, Yimin Pang

Electrical Engineering Graduate Theses & Dissertations

Spectrum sharing allows the coexistence of heterogeneous wireless networks on the same frequency band. Managing the interference between such networks is critically important to ensure high spectrum efficiency, thus motivating the study of multiple-input-multiple-output (MIMO) interference channels (IC) in information theory. This dissertation studies three classes of such interference channels, namely, the MIMO one-to-three IC, the MIMO IC-ZIC, and the MIMO MAC-IC-MAC.

The MIMO one-to-three IC is a partially connected three-user IC with multiple antenna terminals, where one transmitter that causes interference is heard at all three receivers, whereas the other two transmitters are heard only by their intended receivers ...


Wideband Dual-Polarized Digital Direction Of Arrival Sensors, Riley Nelson Pack Jan 2019

Wideband Dual-Polarized Digital Direction Of Arrival Sensors, Riley Nelson Pack

Electrical Engineering Graduate Theses & Dissertations

This thesis presents the design of wideband, dual-polarized direction of arrival (DOA) antennas intended for use with digital processing backends. It is shown that using a digital receiver for DOA allows for wider bandwidth and improvement of the size, weight, and complexity of the antenna system at the cost of traditional design metrics. All antennas are designed using full-wave finite element simulations and are validated with measurements.

Four-arm modulated arm width (MAW) spiral antennas are analyzed for use as digital DOA sensors for linearly-polarized signals. Counter to traditional design procedures, tightly-wound MAW spirals with a small modulation ratio perform significantly ...


Fast 3d Inhomogeneous Radiative Transfer Model Incorporating Aspherical Frozen Hydrometeors With Application To Precipitation Locking, Kun Zhang Jan 2019

Fast 3d Inhomogeneous Radiative Transfer Model Incorporating Aspherical Frozen Hydrometeors With Application To Precipitation Locking, Kun Zhang

Electrical Engineering Graduate Theses & Dissertations

A horizontally inhomogeneous unified microwave radiative transfer (HI-UMRT) model incorporating aspherical frozen hydrometeors based on the NASA/GSFC OpenSSP database is presented to study 3-dimensional (3D) effects of horizontal inhomogeneous clouds on computed microwave radiances and facilitate satellite radiance assimilation over horizontally inhomogeneous weather conditions. HI-UMRT provides a coupled two-Stokes parameter numerical radiance solution of the 3D radiative transfer equation by embedding the existing 1D UMRT algorithm into an iterative perturbation scheme. The horizontal derivatives in radiances of lower perturbation order are treated as the source functions of the azimuthal harmonic perturbation radiative transfer equations that are readily solved by ...


The Economics Of Orbit Use: Theory, Policy, And Measurement, Akhil Rao Jan 2019

The Economics Of Orbit Use: Theory, Policy, And Measurement, Akhil Rao

Economics Graduate Theses & Dissertations

Earth's orbits are a congestible resource with novel dynamic externalities. In this dissertation my coauthors and I examine the nature of orbit use externalities, study the policy choice space to classify existing policies and identify a class of optimal policies, consider the extent to which technological advancements can mitigate these externalities, and calculate the magnitude and time path of both an optimal satellite tax and the welfare gains from implementing it. Three key results emerge. First, open access to Earth's orbits drive the problems of excess collision risk and debris production. Left to their own devices, profit-maximizing firms ...


Indoor Black And Brown Carbon From Cooking Activities And Outdoor Penetration: Insights From The Homechem Study, Sumit Sankhyan Jan 2019

Indoor Black And Brown Carbon From Cooking Activities And Outdoor Penetration: Insights From The Homechem Study, Sumit Sankhyan

Mechanical Engineering Graduate Theses & Dissertations

Particulate matter emissions from cooking activities are a major contributor to indoor air pollution in households. A major part of these emissions consists of light absorbing aerosols known as black carbon (BC) and brown carbon (BrC). The goal of this work was to characterize the contributions of indoor and outdoor sources of BC and BrC to the indoor environment by measuring real-time concentrations of these components indoors and outdoors concurrently during the month-long HOMEChem field study in June 2018. We quantified the penetration of BC and BrC into the house from outdoor sources and characterized the impacts of cooking activities ...


Direct Numerical Simulations Of The Compressible Low Atwood Rayleigh-Taylor Instability, Scott A. Wieland Jan 2019

Direct Numerical Simulations Of The Compressible Low Atwood Rayleigh-Taylor Instability, Scott A. Wieland

Mechanical Engineering Graduate Theses & Dissertations

Two fluids are considered Rayleigh-Taylor unstable when the more dense fluid is suspended above the less dense fluid in the presence of a gravitational like accelerative force. When a pertur- bation is applied to the interface between the two, they begin mixing as the light fluid rises and the heavy fluid drops. The extension of this to the compressible regime leads to the densities of the fluids to not be constant, but instead the molar mass is used to define the weights. At the interface, a density jump still occurs, but away from the interface the densities can vary in ...


Thermal Conductivity Of Complex Crystals, High Temperature Materials And Two Dimensional Layered Materials, Xin Qian Jan 2019

Thermal Conductivity Of Complex Crystals, High Temperature Materials And Two Dimensional Layered Materials, Xin Qian

Mechanical Engineering Graduate Theses & Dissertations

Thermal conductivity is a critical property for designing novel functional materials for engineering applications. For applications demanding efficient thermal management like power electronics and batteries, thermal conductivity is a key parameter affecting thermal designs, stability and performances of the devices. Thermal conductivity is also the critical material metrics for applications like thermal barrier coatings (TBCs) in gas turbines and thermoelectrics (TE). Therefore, thermal conductivities of various functional materials have been investigated in the past decade, but most of the materials are simple and isotropic crystals at low temperature. This is because the first-principles calculation is limited to simple crystals at ...