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...
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 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...
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 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 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 mixture-averaged 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...
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.
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...
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...
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...
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...
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...
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...
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...
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...
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...
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,...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...