The finite difference time domain (FDTD) method was used to model anti-reflective properties of a variety of sub-wavelength structures for 300 to 1300 nm input light. Light hitting non-tapered nanostructures exhibited interference patterns similar to thin film anti-reflective coatings (ARCs), increasing the anti-reflective effect at several wavelengths. The lowest reflectance...
Finite-difference time-domain simulations are performed on a 900 MHz band antenna inside and outside the carbon fiber body of a solar-powered electric vehicle. Data are analyzed to determine the optimal antenna placement for transmission to a receiving antenna located toward the rear of the solar vehicle. Modeling data are compared...
The behavior of small atomics cluster largely depends on their geometry,
due to the high ratio of surface atoms to interior atoms. One interesting aspect
to study clusters centers around characterizing the transition behavior between
nite and bulk materials, where the ratio of surface atoms to interior atoms is
very...
This thesis presents a study of applications and techniques for molecular dynamics simulations. Three studies are presented that are intended to improve our ability to simulate larger systems more realistically. A comparison study of two- and three-body potential models for liquid and amorphous Si0₂ is presented. The structural, vibrational, and...
This dissertation concerns several problems in the fields of light interaction with nanostructured media, metamaterials, and plasmonics. We present a technique capable of extending operational bandwidth of hyperbolic metamaterials based on interleaved highly-doped InGaAs and undoped AlInAs multilayer stacks. The experimental results confirm theoretical predictions, exhibiting broadband negative refraction response...
The widespread adoption of wavelength division multiplexing to increase the bandwidth of optical fiber communication systems has provided a major impetus for research on low cost, single-mode, wavelength stable tunable diode lasers for use in optical telecommunications due to the large volume of lasers required. Other applications, such as demodulation...
Many biological processes are regulated by the presence and movement of cellular Ca²⁺ ions. The concentration of Ca²⁺ in a cellular environment is regulated by IP₃ sensitive channels that lie on the surface of a cell’s endoplasmic reticulum. Little is known about the macroscopic effects of intracellular Ca²⁺ activity, so...
This data contains results from direct numerical simulations of three-dimensional, premixed, hydrogen/air flames, using the mixture-averaged diffusion model. We performed the simulations using the finite-difference code NGA; simulation details are described completely in the associated article.
This dissertation has two objectives. The first objective is to determine where best to situate the study of mentoring (i.e. the 'making of scientists') on the landscape of the history of science and science studies. This task is accomplished by establishing mentoring studies as a link between the robust body...
This data contains results from direct numerical simulations of three-dimensional, premixed, hydrogen/air flames, using the multicomponent diffusion model. We performed the simulations using the finite-difference code NGA; simulation details are described completely in the associated article.
In this paper, I used a linguistic lens of translanguaging and semiotics to examine how K-12 mathematics teacher candidates (TCs) create meaning around computer science (CS) and mathematics concepts in a computational thinking (CT) setting. I defined the term “disciplinary repertoire” as a mirror to the concept of a linguistic...
It is desirable for complex engineered systems to perform missions efficiently and economically, even when these missions' complex, variable, long-term operational profiles make it likely for hazards to arise. It is thus important to design these systems to be resilient so that they will actively prevent and recover from hazards...
The current model for gamma ray bursts (GRBs) assumes that internal shocks are responsible for the emission of gamma-rays. Internal shocks occur when the fast expanding shell collides with the slowly expanding shells. The light curve of a GRB depends on the initial state and the expanding speed of the...
The Introductory Physics 20X series has developed an advanced, metacognitive curriculum which requires a high degree of active learning in order for students to succeed in the class. Recently, the series has been transferred to the online campus, Ecampus, and is now available for distance learners. My work is focused...
NuScale Power has designed a small modular reactor using natural circulation cooling dependent systems for both steady-state and transient operations. The NuScale Integral Test System (NIST-1) facility was built to supply test data to NuScale Power to verify and validate computer codes for the NuScale Power Mod- ule (NPM) with...
ThermoSolver is an educational thermodynamics software program designed to be both
easy to use and useful in that it permits the user to make nontrivial chemical engineering
thermodynamic calculations. The software program accompanies the textbook
Engineering and Chemical Thermodynamics by Milo Koretsky, and is available for free
download from the...
A time-dependent, spectral, barotropic model and a similar
two-layer primitive equation model are developed to investigate the
planetary-scale wave responses to various types of large-scale
forcing: vorticity and heat sources, and sea surface temperature (SST)
anomalies. Both models are linearized about the zonal mean states of
January climatology.
The characteristics...
The long-term evolution of Gaussian eddies is studied in an equivalent barotropic model using both linear and nonlinear quasi-geostrophic theory in an attempt to understand westward propagating satellite altimetry tracked mesoscale eddies. By examining both individual eddies and a large basin seeded with eddies, it is shown that long term...
John Archibald Wheeler (09 July 1911- ) is a familiar name to physicists and historians of physics alike. Among his many contributions to the corpus of knowledge, in 1939 John Wheeler and Niels Bohr co-authored the first paper on the generalized mechanism of nuclear fission. Beyond that seminal work, Wheeler...
In a Modular High Temperature Gas Reactor (MHTGR), the Depressurized Conduction Cooldown (DCC) event can be separated into three distinct stages: 1) depressurization, 2) air ingress and, 3) natural circulation. During normal operations, the HTGR utilizes forced convection to move the helium coolant through the reactor core. Thus, during normal...
Metal organic Frameworks (MOFs) that experience stimuli induced structural transformation could enable a whole new class of materials with remarkable properties. Photoactuating moieties in the structure could effect changes in the pore space or macroscale shape change enabling light driven gas separation and actuators. Here, we present a novel approach...
The U.S. Pacific Northwest is home to one of the most extreme wave climates in the world with waves of 10 m in height arriving to the coast approximately each year. With an average water temperature of 12℃, the beaches in the region are too cold to go on a...
Photonic sintering of nanoparticles is a relatively new process for sintering of nanoparticles, deposited on a substrate, into functional solid structures. The working principle of this process is the incidence of large-area broad-spectrum light onto deposited nanoparticles, which results in heat generation in the nanoparticles and their subsequent densification. Key...
Four years ago, we noted that, although there was a widespread belief that the key to many ocean processes must be the communication of energy by internal waves, there had been little progress in definitely relating small‐scale processes to internal waves (Caldwell, 1983a). For example, although it seemed plausible that...
Physics sensemaking is a growing topic of study within the physics education community. Many lenses have been used to study sensemaking but few have considered how time and instruction can impact student sensemaking practices and ideas. In this dissertation, I present four studies that address four major questions: What sensemaking...
The determination of the optimal location of transceivers is a critical design factor when deploying a wireless local area network (WLAN). The performance of the WLAN will improve in a variety of aspects when the transceivers' locations are adequately determined, including the overall cell coverage to the battery life of...
Crystals are solid materials with periodic and symmetric molecular patterns. The structure of a crystalline solid determines its properties, making it essential to study its structures. From the principle of minimum energy, a crystal will choose a structure with the lowest free energy F = U – TS. At low...
Optical potential for antikaon-nucleus strong interactions are constructed using
elementary antikaon-nucleus potentials determined previously. The optical potentials
are used to determine the existence of a kaon hypernucleus. Modern three
dimensional visualization techniques are used to study model dependences, new
methods for speeding the calculation of the optical potential are developed,...
An investigation was made to determine teacher facilitation techniques in large lecture physics classrooms that foster small group discussion. Video recordings of an introductory calculus-based physics class were taken for the 2008-2009 academic year at Oregon State University. These videos were analyzed to determine student participation in small group discussion...
This dissertation focuses on indoor free-space optical communications systems for use in short range wireless networks. We propose that current radio frequency wireless links be augmented or replaced with optical frequency links due to overcrowding in the radio frequency spectrum. Optical frequencies contain hundreds of terahertz of unregulated bandwidth and...
A sequence of direct simulations is used to study mechanisms for the growth of secondary
circulations and turbulence in stratified shear flows. Five cases are examined, of which four deliver
Holmboe waves as the primary instability and the fifth generates Kelvin-Helmholtz billows.
Secondary circulations range in strength from weak, laminar...
Turbulence resulting from Kelvin–Helmholtz instability in layers of localized stratification and shear is studied by means of direct numerical simulation. Our objective is to present a comprehensive description of the turbulence evolution in terms of simple, conceptual pictures of shear–buoyancy interaction that have been developed previously based on assumptions of...
The application of information theory and digital signal processing techniques to digital
communication has resulted in robust methods for reliable high speed data transmission
over noisy channels environments. Among these methods, multicarrier systems have
become a viable solution for exploiting maximum spectral efficiency over both wideband
highly dispersive static and...
Modern scientific and engineering problems often require simulations with a level of resolution difficult to achieve in reasonable amounts of time—even in effectively parallelized programs. Therefore, applications that exploit high performance computing (HPC) systems have become invaluable in academia and industry over the past two decades. Addressing the questions that...
The authors analyze electromagnetic modes in multilayered nanocomposites and demonstrate that the response of a majority of realistic layered structures is strongly affected by the nonlocal effects originating from strong field oscillations across the system, and is not described by conventional effective-medium theories. They develop the analytical description of the...
The subject of fluid-structure interactions (FSI) are a matter concerning the design of any element immersed in a fluid. One of the most critical phenomena embedded within the scope of FSI is the creation of vortex-induced vibrations (VIV). These type of vibrations originate in a given body as a result...
A two-dimensional numerical mesoscale model, which ic1udes
radiative and turbulent transfers, has been constructed to study the
formation, development and dissipation of coastal stratus cloud
under an inversion. In the model, the delta-Eddington and emissivity
approximations are used for the solar and thermal radiative
transfers, respectively. K-theory parameterization is adopted...
Physicists solve problems and communicate their work using many external representations, such as equations, words, diagrams, graphs, sketches, pictures, and more. To learn physics, then, students must learn to use external representations. In this dissertation, I present three manuscripts. Each manuscript discusses how upper-division Paradigms in Physics students use multiple...
We discuss Einstein’s field equations in the presence of signature change using variational methods, obtaining a generalization of the Lanczos equation relating the distributional term in the stress tensor to the discontinuity of the extrinsic curvature. In particular, there is no distributional term in the stress tensor, and hence no...
Quantum physics in the Copenhagen interpretation places an unsatisfying divide between the quantum and classical worlds. Decoherence -- the destruction of superposition states of the system -- helps us understand how the quantum transitions to the classical. Quantum Darwinism builds on decoherence to understand how information about the system is...
Learning about periodic and oscillatory systems is a huge step in an undergraduate's
comprehensive understanding of physics and complex systems such as solids. However,
understanding how specific changes to such a system affect aspects of the entire system can
be difficult. The goal of this study is to create a...
The computation of Lagrangian coherent structures typically involves post-processing of experimentally or
numerically obtained fluid velocity fields to obtain the largest finite-time Lyapunov exponent (FTLE) field.
However, this procedure can be tedious for large-scale complex flows of general interest. In this work, an
alternative approach involving computation of the FTLE...
Direct numerical simulations of turbulence resulting from Kelvin–Helmholtz instability in stably
stratified shear flow are used to study sources of anisotropy in various spectral ranges. The set of
simulations includes various values of the initial Richardson and Reynolds numbers, as well as
Prandtl numbers ranging from 1 to 7. We...
We present a model that describes nanosecond (ns) time-scale photocurrent dynamics in functionalized anthradithiophene (ADT) films and ADT-based donor-acceptor (D/A) composites. By fitting numerically simulated photocurrents to experimental data, we quantify contributions of multiple pathways of charge carrier photogeneration to the photocurrent, as well as extract parameters that characterize charge...
This study aimed to investigate students' models of probability in a modern physics context. The study was divided into three phases. The first phase explored student pre-knowledge about probability before modem physics instruction. The second phase investigated student understanding of concepts related to probability such as wave-particle behavior, the uncertainty...
Mathematical sophistication increases rapidly as students transition from lower- to upper-division physics courses. Complex algebra is one of the mathematical tools that is not introduced or used in lower-division physics courses but is pervasive throughout upper-division courses. In this dissertation, I study middle-division physics students' developing fluency with complex number...
Power transient boiling has been studied for decades, however, the mechanistic understanding of phenomena which occur during such an event remains incomplete. Due to a dearth of systematic researches, the information of studied phenomenon, detailed physics and applicable hypothesis are very limited. Transient critical heat flux (CHF) is paramount in...
We develop a classical density functional for water which combines the White Bear fundamental-measure theory (FMT) functional for the hard sphere fluid with attractive interactions based on the statistical associating fluid theory variable range (SAFT-VR). This functional reproduces the properties of water at both long and short length scales over...
Three aspects of glow discharges have been studied: glow discharge oscillations,
sputtering, and coupling between cathode and anode regions the two most important
regions in a glow discharge. Cathode and anode processes are tightly coupled by electron
and ion coupling effects. Both electron and ion coupling effects were observed by...
The binding energies of n < 100 carbon clusters are calculated using the ab initio density functional theory code
Quantum Espresso. Carbon cluster geometries are determined using several levels of classical techniques and further
refined using density functional theory. The resulting energies are used to compute the work of cluster...
We exhibit long-lived resonances in scattering from two-dimensional soft cage potentials comprised of three and four Gaussian peaks. Specific low-energy resonances with very narrow width are shown to correspond to classical multiple-reflection events. These states have much larger probability densities inside the cage than outside and mimic bound states in...
Impulse-radio ultra-wide-band (IR-UWB) signaling is a promising technique
for high-speed, short-range relay communications networks. Depending on how
the relay node retransmits the signal, there are two main relay schemes: conventional
one-directional (one-way) relay model, and bi-directional (two-way) relay
model. In bi-directional relay communications, wireless network coding (WNC),
also called physical-layer...
Vacuum ultraviolet reflectivity measurements of three thin-film electroluminescent phosphors, zinc sulfide (ZnS), strontium sulfide (SrS), and strontium-calcium thiogallate (Sr₀.₄₅Ca₀.₅₅Ga₂S₄), are reported using thin-film samples. Measured ZnS reflectivity peak positions are in agreement with values previously reported in the literature. SrS room temperature reflectivity measurements are found to be consistent with...
This study addresses the relationship between thermal microfronts and coherent vortex structures in homogeneous turbulence. The turbulence is created by mean shear in a weakly stratified flow. The data set is generated by direct numerical simulation providing highly resolved instantaneous three‐dimensional fields of fluctuating velocity and temperature (1603 data points...
Coastal hazards are the result of numerous physical processes cumulatively causing water levels to flood and erode the land. The waves, storm surges, tides, and run-off contributing to elevated water levels are each the product of chaotic and random weather patterns. These stochastic weather patterns dissipate energy in Earth's climate...
A parametric manifold can be viewed as the manifold of orbits of a (regular) foliation of a manifold by means of a family of curves. If the foliation is hypersurface orthogonal, the parametric manifold is equivalent to the one‐parameter family of hypersurfaces orthogonal to the curves, each of which inherits...
In this dissertation, the process of computational modeling of amorphous oxide materials is studied. Amorphous oxides have random atomic arrangements with no long-range structural order which makes it difficult to study structure-property relationships. Despite the difficulties, amorphous oxides have great uses as semiconductors and dielectrics in thin-film transistors. The ability...
This thesis presents a decentralized communication planning algorithm for cooperative terrain-based navigation (dec-TBN) with autonomous underwater vehicles. The proposed algorithm uses forward simulation to approximate the value of communicating at each time step. The simulations are used to build a directed acyclic graph that can be searched to provide a...
We will describe two known strategies for static processor
allocation in an n-cube multiprocessor, namely the buddy system
strategy and the gray code strategy, and then propose a new strategy
that outperforms the first by (n-k+1) and the second by (n-k+1)/2 in
cube recognition. Furthermore, our strategy is suitable for...
Artificial collectives are useful for accomplishing tasks that require teamwork from multiple simple robots. Multiple robot and collective testbeds have been developed, yet none stay committed to leverage the local interactions, group size, and imperfect information assumptions that strengthen biological collectives. A review of the collective and multiple robot literature,...
Inertial microfluidics refers to the manipulation of the location and velocity of particles suspended in microscale fluid flow without the introduction of outside forces. It has promising applications in flow cytometry and other biomedical technologies because of the potential for lowering cost and complexity relative to current particle focusing methods....
Amphibians are experiencing global population declines and are one of the most threatened groups of vertebrates. This can be attributed to multiple environmental stressors such as habitat loss, disease, invasive species, and climate change. For vocal amphibian species, loss of acoustic habitat due to anthropogenic noise may be yet another...
The nuclear industry has shown a large interest in natural circulation driven passive cooling systems following the Fukushima nuclear accident. Despite this interest, there is no widely used heat transfer correlation or friction factor correlation developed for natural circulation driven flow. A CFD analysis including grid convergence testing using Fluent...
In this dissertation, the spectroscopic properties and thermodynamic stability of a class of materials known as metal oxo and hydroxo clusters are studied. In aqueous solutions, many metals can aggregate into discrete clusters of metals bridged by oxo or hydroxo ligands. These clusters are of particular interest to us for...
Offshore renewable energy (ORE) has the potential to be a significant source of future global electricity production, reduce carbon emissions, decrease dependence on energy importation, and stimulate economic growth in coastal and remote areas. The availability and abundance of ORE, paired with growing coastal population centers, position offshore wind, wave,...
In this report, three studies are presented that utilize computations to predict transformations, identities, and properties of environmental organic molecules. Each study shows how computations can lead to models of chemical behavior. The importance of this research is rooted in the need for understanding how human behavior and health intersect...
All-optical switching has myriad applications in optoelectronics, optical communications, and
quantum information technology. To achieve ultrafast optical switching in a compact yet versatile
setup, we demonstrate distinct sets of two-dimensional (2D) broadband up-converted multicolor
arrays (BUMAs) in a thin type-I β-barium-borate crystal with two noncollinear near-IR
femtosecond pulses at various...
The progress made in accelerating simulations of fluid flow using GPUs, and the challenges that remain, are surveyed. The review first provides an introduction to GPU computing and programming, and discusses various considerations for improved performance. Case studies comparing the performance of CPU- and GPUbased solvers for the Laplace and...
Since High Temperature Gas-cooled Reactors are being considered as most promising design of upcoming IV Gen reactors, thus key research areas were identified to address safety aspects of this design. Number of simulations and experiments need to be conducted in this field. In this study thermal-hydraulics aspects of coolant flow...
Downward flow opposing mixed convection conditions have been studied using the FLUENT CFD code. This work was comprised of two primary objectives. The first was to study core channel flow reversal susceptibility in the Gas Reactor Test Section (GRTS) at low flow conditions. The second objective was the development of...
The researcher explored interpersonal trust (a construct from the fields of psychology
and sociometry) in the context of engineering work groups. The study explored the potential
antecedents of trust and the relationships among trust, creativity, communication, emotional
empathy and positive affect. The study attempts to argue that 1) trust is...
A model is developed to describe the reversible nature of gecko dry adhesion. The central aspect of this model is that the seta can be easily peeled away from the contacting surface by a small moment at the contact tip. It is shown that this contact condition is very sensitive,...
Ideal for personal-growth study groups, for staff in business or agency human-resource departments, and for organizations that work on diversity issues. A gentle yet challenging look at ways to change the world by changing one's own intercultural relationships. Discusses differences in communication styles, sense of time and space, and power...
Multiple-input multiple-output wireless systems promise significant capacity gain
and/or diversity gain over single antenna systems. If channel state information (CSI)
is available at both the transmitter and the receiver, the performance can be further
improved. In this thesis, first, we study binary index feedback problem in beamforming
systems when the...
Dynamic DC offset is one of the biggest problems preventing the implementation of single chip receivers. This thesis presents a 2.4GHz downconversion mixer designed to work with adaptive DC offset cancellation for a fully integrated direct conversion receiver. Offset can be removed by dynamically changing the PFET load bias in...
The frame of reference for understanding the
rhetorical significance of cultural acts lies in the
identification and explication of the diversity of theories
which encompass sociological and anthropological
definitions of culture. The paradigms presented in this
thesis range from unilinear evolution, biological and
environmental determinism, materialism, historical
ethnology and reductionism...
Sodium cooled nuclear reactors are being considered for the next generation of nuclear power plants to provide clean electricity to the world. To prove the safety of these reactors, the fuel must be shown to safely handle large neutron fluxes that cause a spike in the thermal output of the...
In recent years, the elliptic curve cryptosystems (ECC) have received attention
due to their increased security with smaller key size which brings the advantage of less
storage area and less bandwidth. Elliptic curve cryptography provides a methodology
for obtaining high-speed, efficient, and scalable implementations of network security
protocols. In addition...
In this work, a multicomponent lattice Boltzmann model is developed for the simulation of multiphase mixing, reactions, and separations processes. This model is unique in that diffusive mass transfer of a component in the model is driven by gradients of chemical potential. This fundamentally correct description of diffusion accurately captures...
This paper is included in the Proceedings, Part 1, of the International Conference on Computational Science 2009 (ICCS 2009) held in Baton Rouge, LA, USA, May 25-27, 2009.
Microreactors offer high rates of heat transfer able to intensify highly endothermic biomass reforming reactions in supercritical water. In this study, two continuous flow microreactor configurations were used to gasify biomass constituents in supercritical water. The first reactor configuration was a micro diameter stainless steel or Hastelloy tube (508 µm...
A method was sought to predict the flight paths and collisions for closely spaced ink droplets of various sizes as a design aid for ink-jet printing development. Computational fluid dynamics models of two rigid aligned spheres, as a proxy for ink droplets, were initiated in atmospheric pressure air at constant...
We describe an upper-division experiment in thermal physics where students measure the tension
of a rubber band as a function of temperature and length, and use a Maxwell relation to find the
change in internal energy and entropy for an isothermal stretch. This allows students to experimentally check the predictions...
Floating offshore wind energy is anticipated to become a competitive source of renewable energy by the late 2020s, but the industry must reduce costs and uncertainties associated with the technology to do so. Identifying solutions to these problems frequently relies on computational modeling, which presents technical shortcomings limiting the versatility...
Smoldering combustion in wildland fires is a critical phenomenon that needs in-depth study because it can initiate with weaker ignition sources, can persist for long periods, is difficult to suppress, and can transit to flaming combustion. Cellulose, hemicellulose, and lignin are the major organic constituents within biomass, in varying proportions...
My work on computing complex catalyzed organic transformations reveals that only a few subtle chemical factors, e.g. non-classical hydrogen bonding, (hyper)conjugation and steric effects, common across different catalyst manifolds are critical for catalysis and selectivity. Rational manipulation and exploitation of these factors has led to improved catalyst designs, which has...
This thesis presents an analytical, experimental and numerical study of the initiation of flows in a siphon for rapid and gradual openings of a downstream valve. Three initial water levels in the upstream tank and four final positions for the downstream valve were investigated. Two opening times of the downstream...
Emergence of a terawatt scalable photovoltaic (PV) thin film technology is currently impeded by
the limited supply of relatively rare elements like In or Te, which has spurred active research in
recent years on earth-abundant PV materials. Instead of searching for alternative PV materials,
we approach the problem here by...
The goal of this project was to pave the way for more data-driven decision making when considering safety within Nuclear Engineering by proving the concept of new and innovative accident scenario modeling techniques for the analysis of the economics of nuclear safety margins. To do this, a simple, if extremely...
The US military is evaluating the capabilities of emerging technologies based on IEEE 802.16 standard as a potential commercial off-the-shelf solution to support the communication requirements of the future war.
In the last few years, development in military and telecommunication industries have focused on an intensive use of broadband systems,...
The OSU Extension Soil Sensitivity Database lists
nonirrigated and irrigated soil sensitivity ratings for every
map unit of every soil survey in Oregon. These ratings
were developed for the Oregon Water Quality Decision
Aid, a tool for evaluating groundwater vulnerability to
pesticide contamination.
Secure Computation is a powerful tool that enables a set of parties to jointly compute any function over their private inputs, without a trusted third party. Private Set Intersection is a specific case of two-party Secure Computation, where Alice (with private set X) and Bob (with private set Y) specifically...
This is a psycho-socio-linguistic study of language
as the primary tool of institutions such as education,
government, and religion. These institutions have goals
associated with identifying with, communicating with, and
influencing individuals in the general public who are not
Part of the group. A review of psycho-socio-linguistic
theory suggests that...
Accurate and efficient computational methods to evaluate the
quasi-TEM parameters of various planar structures such as microstrips,
coplanar lines and coplanar waveguides are developed. The characteristic
parameters of all these structures which are used extensively
in microwave integrated circuits for applications as transmission
lines and other circuit elements are computed...