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Articles 1 - 30 of 341
Full-Text Articles in Physics
Networks Identify Productive Forum Discussions, Adrienne L. Traxler, A. Gavrin, Rebecca Lindell
Networks Identify Productive Forum Discussions, Adrienne L. Traxler, A. Gavrin, Rebecca Lindell
Physics Faculty Publications
Discussion forums provide a channel for students to engage with peers and course material outside of class, accessible even to commuter and nontraditional populations. Forums can build classroom community and aid learning, but students do not always take up these tools. We use network analysis to compare three semesters of forum logs from an introductory calculus-based physics course. The networks show dense structures of collaboration that differ significantly between semesters, even though aggregate participation statistics remain steady. After characterizing network structure for each semester, we correlate students’ centrality—a numeric measure of network position—with final course grade. Finally, we use a …
Item-Level Gender Fairness In The Force And Motion Conceptual Evaluation And The Conceptual Survey Of Electricity And Magnetism, Rachel Henderson, Paul Miller, John Stewart, Adrienne L. Traxler, Rebecca Lindell
Item-Level Gender Fairness In The Force And Motion Conceptual Evaluation And The Conceptual Survey Of Electricity And Magnetism, Rachel Henderson, Paul Miller, John Stewart, Adrienne L. Traxler, Rebecca Lindell
Physics Faculty Publications
Gender gaps on the most widely used conceptual inventories created by physics education researchers have been extensively studied. Most of the research exploring the consistent gender gaps has been performed at the student level using the total evaluation score; less research has been performed examining these assessments at the item level and this research has been predominately restricted to the Force Concept Inventory (FCI). Many studies have identified subsets of FCI items as unfair to either men or women. An item is fair if men and women of equal ability in conceptual physics score equally on the item. This study …
Gender Fairness Within The Force Concept Inventory, Adrienne L. Traxler, Rachel Henderson, John Stewart, Gay Stewart, Alexis Papak, Rebecca Lindell
Gender Fairness Within The Force Concept Inventory, Adrienne L. Traxler, Rachel Henderson, John Stewart, Gay Stewart, Alexis Papak, Rebecca Lindell
Physics Faculty Publications
Research on the test structure of the Force Concept Inventory (FCI) has largely ignored gender, and research on FCI gender effects (often reported as “gender gaps”) has seldom interrogated the structure of the test. These rarely crossed streams of research leave open the possibility that the FCI may not be structurally valid across genders, particularly since many reported results come from calculus-based courses where 75% or more of the students are men. We examine the FCI considering both psychometrics and gender disaggregation (while acknowledging this as a binary simplification), and find several problematic questions whose removal decreases the apparent gender …
Exploring The Gender Gap In The Conceptual Survey Of Electricity And Magnetism, Rachel Henderson, Gay Stewart, John Stewart, Lynnette Michaluk, Adrienne L. Traxler
Exploring The Gender Gap In The Conceptual Survey Of Electricity And Magnetism, Rachel Henderson, Gay Stewart, John Stewart, Lynnette Michaluk, Adrienne L. Traxler
Physics Faculty Publications
The “gender gap” on various physics conceptual evaluations has been extensively studied. Men’s average pretest scores on the Force Concept Inventory and Force and Motion Conceptual Evaluation are 13% higher than women’s, and post-test scores are on average 12% higher than women’s. This study analyzed the gender differences within the Conceptual Survey of Electricity and Magnetism (CSEM) in which the gender gap has been less well studied and is less consistent. In the current study, data collected from 1407 students (77% men, 23% women) in a calculus-based physics course over ten semesters showed that male students outperformed female students on …
Coursenetworking And Community: Linking Online Discussion Networks And Course Success, Adrienne L. Traxler, Andrew Gavrin, Rebecca Lindell
Coursenetworking And Community: Linking Online Discussion Networks And Course Success, Adrienne L. Traxler, Andrew Gavrin, Rebecca Lindell
Physics Faculty Publications
Large introductory science courses are isolating for many students, and reducing this isolation is an important factor for student retention in college. Active learning courses often build community among students as an explicit goal, but many commuter or non-traditional students have limited on-campus time. Online discussion forums provide one tool for engaging students with each other outside of class time. This study uses social network analysis with forum data from an introductory physics course to examine students' positions in the class discussion network and link it to their final course grades. We find that, contrary to expectations, there is no …
Non-Traditional Students' Conceptual Scores And Network Centrality In Scale-Up Classrooms, Emily N. Sandt, Adrienne L. Traxler
Non-Traditional Students' Conceptual Scores And Network Centrality In Scale-Up Classrooms, Emily N. Sandt, Adrienne L. Traxler
Physics Faculty Publications
As classrooms transition from traditional to cooperative learning environments, questions about the details of these environments effectiveness are posed. Does this model equally benefit all students? How do nontraditional (NT) students' gains in conceptual knowledge compare to those of traditional (Trad) students in these classrooms? Do NT students' social differences (i.e. age, employment status, family life, etc.) affect the amount of learning they do in the course or their tendency to form collaborative ties with other students? In three sections of SCALE-UP introductory calculus-based physics, we collected social network survey data about student connections and used the Force Concept Inventory …
Photoexcited Carrier Trapping And Recombination At Fe Centers In Gan, T. K. Uždavinys, S. Marcinkevičius, J. H. Leach, K. R. Evans, David C. Look
Photoexcited Carrier Trapping And Recombination At Fe Centers In Gan, T. K. Uždavinys, S. Marcinkevičius, J. H. Leach, K. R. Evans, David C. Look
Physics Faculty Publications
Fe doped GaN was studied by time- resolved photoluminescence (PL) spectroscopy. The shape of PLtransients at different temperatures and excitation powers allowed discrimination between electron and hole capture to Fe3+ and Fe2+ centers, respectively. Analysis of the internal structure of Fe ions and intra-ion relaxation rates suggests that for high repetition rates of photoexciting laser pulses the electron and hole trapping takes place in the excited state rather than the ground state of Fe ions. Hence, the estimated electron and hole capture coefficients of 5.5 × 10−8 cm3/s and 1.8 × 10−8 cm3/s should be attributed to excited Fe3+ and …
Ultrafast Saturation Of Electronic-Resonance-Enhanced Coherent Anti-Stokes Raman Scattering And Comparison For Pulse Durations In The Nanosecond To Femtosecond Regime, Anil K. Patnaik, Sukesh Roy, James R. Gord
Ultrafast Saturation Of Electronic-Resonance-Enhanced Coherent Anti-Stokes Raman Scattering And Comparison For Pulse Durations In The Nanosecond To Femtosecond Regime, Anil K. Patnaik, Sukesh Roy, James R. Gord
Physics Faculty Publications
The saturation threshold of a probe pulse in an ultrafast electronic-resonance-enhanced (ERE) coherent anti-Stokes Raman spectroscopy (CARS) configuration is calculated. We demonstrate that while the underdamping condition is a sufficient condition for saturation of ERE-CARS with the long-pulse excitations, a transient gain must be achieved to saturate the ERE-CARS signal for the ultrafast probe regime. We identify that the area under the probe pulse can be used as a definitive parameter to determine the criterion for a saturation threshold for ultrafast ERE-CARS. From a simplified analytical solution and a detailed numerical calculation based on density-matrix equations, the saturation threshold of …
Improved Sensitivity Mems Cantilever Sensor For Terahertz Photoacoustic Spectroscopy, Ronald A. Coutu Jr., Ivan Medvedev, Douglas T. Petkie
Improved Sensitivity Mems Cantilever Sensor For Terahertz Photoacoustic Spectroscopy, Ronald A. Coutu Jr., Ivan Medvedev, Douglas T. Petkie
Physics Faculty Publications
In this paper, a microelectromechanical system (MEMS) cantilever sensor was designed, modeled and fabricated to measure the terahertz (THz) radiation induced photoacoustic (PA) response of gases under low vacuum conditions. This work vastly improves cantilever sensitivity over previous efforts, by reducing internal beam stresses, minimizing out of plane beam curvature and optimizing beam damping. In addition, fabrication yield was improved by approximately 50% by filleting the cantilever’s anchor and free end to help reduce high stress areas that occurred during device fabrication and processing. All of the cantilever sensors were fabricated using silicon-on-insulator (SOI) wafers and tested in a custom …
How Does The Connectivity Of Open-Framework Conglomerates Within Multi-Scale Hierarchical Fluvial Architecture Affect Oil-Sweep Efficiency In Waterflooding?, Naum I. Gershenzon, Mohamad Reza Soltanian, Robert W. Ritzi, David F. Dominic, Don Keefer, Eric Shaffer, Brynne Storsved
How Does The Connectivity Of Open-Framework Conglomerates Within Multi-Scale Hierarchical Fluvial Architecture Affect Oil-Sweep Efficiency In Waterflooding?, Naum I. Gershenzon, Mohamad Reza Soltanian, Robert W. Ritzi, David F. Dominic, Don Keefer, Eric Shaffer, Brynne Storsved
Physics Faculty Publications
Understanding multi-phase fluid flow and transport processes within aquifers, candidate reservoirs for CO2 sequestration, and petroleum reservoirs requires understanding a diverse set of geologic properties of the aquifer or reservoir, over a wide range of spatial and temporal scales. We focus on multiphase flow dynamics with wetting (e.g., water) and non-wetting (e.g., gas or oil) fluids, with one invading another.
Community Structure In Introductory Physics Course Networks, Adrienne L. Traxler
Community Structure In Introductory Physics Course Networks, Adrienne L. Traxler
Physics Faculty Publications
Student-to-student interactions are foundational to many active learning environments, but are most often studied using qualitative methods. Quantitative network analysis tools complement this picture, allowing researchers to describe the social interactions of whole classrooms as systems. Past results in introductory physics have suggested a sharp division in the formation of social structure between large lecture sections and small studio classroom environments. Extending those results, this study focuses on calculus-based introductory physics courses at a large public university with a heavily commuter and nontraditional student population. Community detection network methods are used to characterize pre- and post-course collaborative structure in several …
Enriching Gender In Per: A Binary Past And A Complex Future, Adrienne L. Traxler, Ximena C. Cid, Jennifer Blue, Ramón Barthelemy
Enriching Gender In Per: A Binary Past And A Complex Future, Adrienne L. Traxler, Ximena C. Cid, Jennifer Blue, Ramón Barthelemy
Physics Faculty Publications
In this article, we draw on previous reports from physics, science education, and women's studies to propose a more nuanced treatment of gender in physics education research (PER). A growing body of PER examines gender differences in participation, performance, and attitudes toward physics. We have three critiques of this work: (1) it does not question whether the achievements of men are the most appropriate standard, (2) individual experiences and student identities are undervalued, and (3) the binary model of gender is not questioned. Driven by these critiques, we propose a conception of gender that is more up-to-date with other fields …
How Does Dissipation Affect The Transition From Static To Dynamic Macroscopic Friction?, Naum I. Gershenzon, Gust Bambakidis, Thomas E. Skinner
How Does Dissipation Affect The Transition From Static To Dynamic Macroscopic Friction?, Naum I. Gershenzon, Gust Bambakidis, Thomas E. Skinner
Physics Faculty Publications
Description of the transitional process from a static to a dynamic frictional regime is a fundamental problem of modern physics. Previously, we developed a model based on the well-known Frenkel-Kontorova model to describe dry macroscopic friction. Here, this model has been modified to include the effect of dissipation in derived relations between the kinematic and dynamic parameters of a transition process. The main (somewhat counterintuitive) result is a demonstration that the rupture (i.e., detachment front) velocity of the slip pulse which arises during the transition does not depend on friction. The only parameter (besides the elastic and plastic …
Understanding The Impact Of Open-Framework Conglomerates On Water-Oil Displacements: Victor Interval Of The Ivishak Reservoir, Prudhoe Bay Field, Alaska, Naum I. Gershenzon, Mohamadreza Soltanian, Robert W. Ritzi, David F. Dominic
Understanding The Impact Of Open-Framework Conglomerates On Water-Oil Displacements: Victor Interval Of The Ivishak Reservoir, Prudhoe Bay Field, Alaska, Naum I. Gershenzon, Mohamadreza Soltanian, Robert W. Ritzi, David F. Dominic
Physics Faculty Publications
The Victor Unit of the Ivishak Formation in the Prudhoe Bay Oilfield is characterized by high net-to-gross fluvial sandstones and conglomerates. The highest permeability is found within sets of cross-strata of open-framework conglomerate (OFC). These cross-strata are preserved within unit-bar deposits and assemblages of unit-bar deposits within compound (braid)-bar deposits, and may form thief zones limiting enhanced oil recovery. We incorporate recent research that has quantified important attributes of preserved sedimentary architecture into high-resolution models. Waterflooding experiments using these models demonstrate the control that such architecture has on oil production rate, water breakthrough time, and spatial and temporal distribution of …
Large Scale Laser Crystallization Of Solution-Based Alumina-Doped Zinc Oxide (Azo) Nanoinks For Highly Transparent Conductive Electrode, Qiong Nian, Michael J. Callahan, Mojib Saei, David C. Look, Harry Efstathiadis, John Bailey, Gary J. Cheng
Large Scale Laser Crystallization Of Solution-Based Alumina-Doped Zinc Oxide (Azo) Nanoinks For Highly Transparent Conductive Electrode, Qiong Nian, Michael J. Callahan, Mojib Saei, David C. Look, Harry Efstathiadis, John Bailey, Gary J. Cheng
Physics Faculty Publications
A new method combining aqueous solution printing with UV Laser crystallization (UVLC) and post annealing is developed to deposit highly transparent and conductive Aluminum doped Zinc Oxide (AZO) films. This technique is able to rapidly produce large area AZO films with better structural and optoelectronic properties than most high vacuum deposition, suggesting a potential large-scale manufacturing technique. The optoelectronic performance improvement attributes to UVLC and forming gas annealing (FMG) induced grain boundary density decrease and electron traps passivation at grain boundaries. The physical model and computational simulation developed in this work could be applied to thermal treatment of many other …
Scaling Of Geochemical Reaction Rates Via Advective Solute Transport, Allen Hunt, B. Ghanbarian-Alavijeh, Thomas E. Skinner, R. P. Ewing
Scaling Of Geochemical Reaction Rates Via Advective Solute Transport, Allen Hunt, B. Ghanbarian-Alavijeh, Thomas E. Skinner, R. P. Ewing
Physics Faculty Publications
Transport in porous media is quite complex, and still yields occasional surprises. In geological porous media, the rate at which chemical reactions (e.g., weathering and dissolution) occur is found to diminish by orders of magnitude with increasing time or distance. The temporal rates of laboratory experiments and field observations differ, and extrapolating from laboratory experiments (in months) to field rates (in millions of years) can lead to order-of-magnitude errors. The reactions are transport-limited, but characterizing them using standard solute transport expressions can yield results in agreement with experiment only if spurious assumptions and parameters are introduced. We previously developed a …
Highly Transparent Conductive Electrode With Ultra-Low Haze By Grain Boundary Modification Of Aqueous Solution Fabricated Alumina-Doped Zinc Oxide Nanocrystals, Qiong Nian, Michael J. Callahan, David C. Look, Harry Efstathiadis, John Bailey, Gary J. Cheng
Highly Transparent Conductive Electrode With Ultra-Low Haze By Grain Boundary Modification Of Aqueous Solution Fabricated Alumina-Doped Zinc Oxide Nanocrystals, Qiong Nian, Michael J. Callahan, David C. Look, Harry Efstathiadis, John Bailey, Gary J. Cheng
Physics Faculty Publications
Commercial production of transparent conducting oxide (TCO) polycrystalline films requires high electrical conductivity with minimal degradation in optical transparency. Aqueous solution deposited TCO films would reduce production costs of TCO films but suffer from low electrical mobility, which severely degrades both electrical conductivity and optical transparency in the visible spectrum. Here, we demonstrated that grain boundary modification by ultra-violet laser crystallization (UVLC) of solution deposited aluminium-doped zinc oxide (AZO) nanocrystals results in high Hall mobility, with a corresponding dramatic improvement in AZO electrical conductance. The AZO films after laser irradiation exhibit electrical mobility up to 18.1 cm2 V−1 …
Investigation Of Plasmon Resonance Tunneling Through Subwavelength Hole Arrays In Highly Doped Conductive Zno Films, Nima Nader, Shivashankar Vangala, Joseph R. Hendrickson, Kevin D. Leedy, David C. Look, Junpeng Guo, Justin W. Cleary
Investigation Of Plasmon Resonance Tunneling Through Subwavelength Hole Arrays In Highly Doped Conductive Zno Films, Nima Nader, Shivashankar Vangala, Joseph R. Hendrickson, Kevin D. Leedy, David C. Look, Junpeng Guo, Justin W. Cleary
Physics Faculty Publications
Experimental results pertaining to plasmon resonance tunneling through a highly conductive zinc oxide (ZnO) layer with subwavelength hole-arrays is investigated in the mid-infrared regime. Gallium-doped ZnO layers are pulsed-laser deposited on a silicon wafer. The ZnO has metallic optical properties with a bulk plasma frequency of 214 THz, which is equivalent to a free space wavelength of 1.4 μm. Hole arrays with different periods and hole shapes are fabricated via a standard photolithography process. Resonant mode tunneling characteristics are experimentally studied for different incident angles and compared with surface plasmontheoretical calculations and finite-difference time-domain simulations. Transmission peaks, higher than the …
Equity Investigation Of Attitudinal Shifts In Introductory Physics, Adrienne L. Traxler, Eric Brewe
Equity Investigation Of Attitudinal Shifts In Introductory Physics, Adrienne L. Traxler, Eric Brewe
Physics Faculty Publications
We report on seven years of attitudinal data using the Colorado Learning Attitudes about Science Survey from University Modeling Instruction (UMI) sections of introductory physics at Florida International University. University Modeling Instruction is a curricular and pedagogical transformation of introductory university physics that engages students in building and testing conceptual models in an integrated lab and lecture learning environment. This work expands upon previous studies that reported consistently positive attitude shifts in UMI courses; here, we disaggregate the data by gender and ethnicity to look for any disparities in the pattern of favorable shifts. We find that women and students …
Multiple Representations And Epistemic Games In Introductory Physics Exam Solutions, Adrienne L. Traxler, Jonathan V. Mahadeo, Daryl Mcpadden, Eric Brewe
Multiple Representations And Epistemic Games In Introductory Physics Exam Solutions, Adrienne L. Traxler, Jonathan V. Mahadeo, Daryl Mcpadden, Eric Brewe
Physics Faculty Publications
Previous analysis of common exam questions in introductory physics at Florida International University has revealed differences in the number and type of epistemic games played by students in their solutions. Separated by course format (lecture/lab, lecture/lab/recitation, or inquiry-based), student work also shows varying use of multiple representational tools. Here we examine representation use in more detail to establish a descriptive picture of representation use across multiple instructors and course formats. We then compare these profiles with the epistemic games played by students, asking whether the same epistemic game shows the same pattern of representational tools across course types. We find …
The Look-Locker Method In Magnetic Resonance Imaging: A Brief, Personal History, David C. Look
The Look-Locker Method In Magnetic Resonance Imaging: A Brief, Personal History, David C. Look
Physics Faculty Publications
The “Look-Locker” method of measuring nuclear spin-lattice relaxation times in a single sweep was invented by David C. Look and Donald R. Locker in 1970 and in the last twenty years has become widely used in magnetic resonance imaging. This article is a brief history of the invention from the remembrances of David Look.
Model Of Deep Nonvolcanic Tremor Part I: Ambient And Triggered Tremor, Naum I. Gershenzon, Gust Bambakidis
Model Of Deep Nonvolcanic Tremor Part I: Ambient And Triggered Tremor, Naum I. Gershenzon, Gust Bambakidis
Physics Faculty Publications
There is evidence of triggering of tremor by seismic waves emanating from distant large earthquakes. The frequency content of triggered and ambient tremor are largely identical, suggesting that tremor does not depend directly on the nature of the source. We show here that the model of plate dynamics developed earlier by us is an appropriate tool for describing the onset of tremor. In the framework of this model, tremor is an internal response of a fault to failure triggered by external disturbances. The model predicts generation of radiation in a frequency range defined by the fault parameters. Other specific features …
Influence Of Small Scale Heterogeneity On Co2 Trapping Processes In Deep Saline Aquifers, Naum I. Gershenzon, Mohamadreza Soltanian, Robert W. Ritzi, David F. Dominic
Influence Of Small Scale Heterogeneity On Co2 Trapping Processes In Deep Saline Aquifers, Naum I. Gershenzon, Mohamadreza Soltanian, Robert W. Ritzi, David F. Dominic
Physics Faculty Publications
The physical mechanism of CO2 trapping in porous media by capillary trapping (pore scale) incorporates a number of related processes, i.e. residual trapping, trapping due to hysteresis of the relative permeability, and trapping due to hysteresis of the capillary pressure. Additionally CO2 may be trapped in heterogeneous media due to difference in capillary pressure entry points for different materials (facies scale). The amount of CO2 trapped by these processes depends upon a complex system of non-linear and hysteretic relationships including how relative permeability and capillary pressure vary with brine and CO2 saturation, and upon the spatial …
Epistemic Games Analysis Of Common Exam Questions Across Course Formats, Jonathan V. Mahadeo, Adrienne L. Traxler, Eric Brewe
Epistemic Games Analysis Of Common Exam Questions Across Course Formats, Jonathan V. Mahadeo, Adrienne L. Traxler, Eric Brewe
Physics Faculty Publications
This study investigates differences in problem-solving performance between three different introductory physics course formats at Florida International University. The course formats--lecture+laboratory (LL), inquiry-based (IQB), and lecture+laboratory+recitation (LLR)--all incorporated two Advanced Placement (AP) questions into their final exams. Students' written responses were evaluated via an AP scoring rubric, and during this scoring, we observed marked differences in solution behavior between the three course formats. To further investigate these differences, we used the framework of epistemic games to analyze student responses. To apply this framework to written work, an epistemic game rubric was created. Application of this rubric yielded game profiles for …
Extending Positive Class Results Across Multiple Instructors And Multiple Classes Of Modeling Instruction, Eric Brewe, Adrienne L. Traxler, Jorge De La Garza, Laird H. Kramer
Extending Positive Class Results Across Multiple Instructors And Multiple Classes Of Modeling Instruction, Eric Brewe, Adrienne L. Traxler, Jorge De La Garza, Laird H. Kramer
Physics Faculty Publications
We report on a multiyear study of student attitudes measured with the Colorado Learning Attitudes about Science Survey in calculus-based introductory physics taught with the Modeling Instruction curriculum. We find that five of six instructors and eight of nine sections using Modeling Instruction showed significantly improved attitudes from pre- to postcourse. Cohen’s d effect sizes range from 0.08 to 0.95 for individual instructors. The average effect was d = 0.45, with a 95% confidence interval of (0.26–0.64). These results build on previously published results showing positive shifts in attitudes from Modeling Instruction classes. We interpret these data in light …
Compensation In Al-Doped Zno By Al-Related Acceptor Complexes: Synchrotron X-Ray Absorption Spectroscopy And Theory, Jiraroj T-Thienprasert, S. Rujirawat, W. Klysubun, J. N. Duenow, T. J. Coutts, S. B. Zhang, David C. Look, Sukit Limpijumnong
Compensation In Al-Doped Zno By Al-Related Acceptor Complexes: Synchrotron X-Ray Absorption Spectroscopy And Theory, Jiraroj T-Thienprasert, S. Rujirawat, W. Klysubun, J. N. Duenow, T. J. Coutts, S. B. Zhang, David C. Look, Sukit Limpijumnong
Physics Faculty Publications
The synchrotron x-ray absorption near edge structures (XANES) technique was used in conjunction with first-principles calculations to characterize Al-doped ZnO films. Standard characterizations revealed that the amount of carrier concentration and mobility depend on the growth conditions, i.e. H2 (or O2)/Ar gas ratio and Al concentration. First-principles calculations showed that Al energetically prefers to substitute on the Zn site, forming a donor AlZn, over being an interstitial (Ali). The measured Al K-edge XANES spectra are in good agreement with the simulated spectra of AlZn, indicating that the majority of Al atoms …
Saturation-Dependence Of Dispersion In Porous Media, B. Ghanbarian-Alavijeh, Thomas E. Skinner, Allen Hunt
Saturation-Dependence Of Dispersion In Porous Media, B. Ghanbarian-Alavijeh, Thomas E. Skinner, Allen Hunt
Physics Faculty Publications
In this study, we develop a saturation-dependent treatment of dispersion in porous media using concepts from critical path analysis, cluster statistics of percolation, and fractal scaling of percolation clusters. We calculate spatial solute distributions as a function of time and calculate arrival time distributions as a function of system size. Our previous results correctly predict the range of observed dispersivity values over ten orders of magnitude in experimental length scale, but that theory contains no explicit dependence on porosity or relative saturation. This omission complicates comparisons with experimental results for dispersion, which are often conducted at saturation less than 1. …
Extraordinary Optical Transmission And Extinction In A Terahertz Wire-Grid Polarizer, J. S. Cetnar, J. R. Middendorf, Elliott R. Brown
Extraordinary Optical Transmission And Extinction In A Terahertz Wire-Grid Polarizer, J. S. Cetnar, J. R. Middendorf, Elliott R. Brown
Physics Faculty Publications
A THz wire grid polarizer is simulated and demonstrated consisting of 40-μm periodic aluminum strips mounted on a polycarbonate substrate with a variable metal-to-gap ratio. Full-wave numerical simulations were performed from 100 GHz to 550 GHz predicting that the transmission in perpendicular (parallel) polarization is much higher (lower) than that predicted by geometric optics, leading to a very high extinction ratio of ∼60 dB between 100 and 550 GHz when the gaps become very small (<5 >μm). This behavior is confirmed qualitatively in experiments between 100 and 530 GHz where extinction ratios exceeding 40 dB are achieved. …
Stable Highly Conductive Zno Via Reduction Of Zn Vacancies, David C. Look, Timothy C. Droubay, Scott A. Chambers
Stable Highly Conductive Zno Via Reduction Of Zn Vacancies, David C. Look, Timothy C. Droubay, Scott A. Chambers
Physics Faculty Publications
Growth of Ga-doped ZnO by pulsed laser deposition at 200 °C in an ambient of Ar and H2produces a resistivity of 1.5 × 10−4 Ω-cm, stable to 500 °C. The resistivity can be further reduced to 1.2 × 10−4 Ω-cm by annealing on Zn foil, which reduces the compensating Zn-vacancy acceptor concentration NA to 5 × 1019 cm−3, only 3% of the Ga-donor concentration ND of 1.6 × 1021 cm−3, with ND and NA determined from a degenerate mobility theory. The plasmon-resonance wavelength is only 1060 …
A New Model For Mixing By Double-Diffusive Convection (Semi-Convection): I. The Conditions For Layer Formation, G. M. Mirouh, P. Garaud, S. Stellmach, Adrienne L. Traxler, T. S. Wood
A New Model For Mixing By Double-Diffusive Convection (Semi-Convection): I. The Conditions For Layer Formation, G. M. Mirouh, P. Garaud, S. Stellmach, Adrienne L. Traxler, T. S. Wood
Physics Faculty Publications
The process referred to as "semi-convection" in astrophysics and "double-diffusive convection in the diffusive regime" in Earth and planetary sciences occurs in stellar and planetary interiors in regions which are stable according to the Ledoux criterion but unstable according to the Schwarzschild criterion. In this series of papers, we analyze the results of an extensive suite of three-dimensional (3D) numerical simulations of the process, and ultimately propose a new 1D prescription for heat and compositional transport in this regime which can be used in stellar or planetary structure and evolution models. In a preliminary study of the phenomenon, Rosenblum et …