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Articles 1201 - 1230 of 3797

Full-Text Articles in Physical Sciences and Mathematics

Using The Real-Time Instructor Observing Tool (Riot) For Reflection On Teaching Practice, Cassandra Paul, Emily West Feb 2018

Using The Real-Time Instructor Observing Tool (Riot) For Reflection On Teaching Practice, Cassandra Paul, Emily West

Faculty Publications

As physics educators, we are constantly looking for ways to improve our practice. There are many different kinds of professional development opportunities that have been shown to help us with this endeavor. We can seek assistance from professionals, like mentor teachers or centers for faculty development, we can attend workshops to learn new curricula or pedagogical skills, and we can engage in learning communities to develop shared visions and become more reflective educators.1However, when these activities end, what can we do on our own to continue to improve? How can we track our improvement? And perhaps even most …

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May The Forces Be With You!, Christopher Sirola Feb 2018

May The Forces Be With You!, Christopher Sirola

Faculty Publications

In everyday life, we usually directly note two basic forces: gravity and electromagnetism. Gravity—as in the acceleration due to Earth’s gravity—tends to be a background force of sorts, something that is always present and always the same. We don’t always see electricity and/or magnetism as such, but their subsidiaries are all around us—friction, normal force, tension, springs, and the like.

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Improved Kansa Rbf Method For The Solution Of Nonlinear Boundary Value Problems, Malgorzata A. Jankowska, Andreas Karageorghis, Ching-Shyang Chen Feb 2018

Improved Kansa Rbf Method For The Solution Of Nonlinear Boundary Value Problems, Malgorzata A. Jankowska, Andreas Karageorghis, Ching-Shyang Chen

Faculty Publications

We apply the Kansa–radial basis function (RBF) collocation method to two-dimensional nonlinear boundary value problems. In it, the solution is approximated by a linear combination of RBFs and the governing equation and boundary conditions are satisfied in a collocation sense at interior and boundary points, respectively. The nonlinear system of equations resulting from the Kansa–RBF discretization for the unknown coefficients in the RBF approximation is solved by directly applying a standard nonlinear solver. In a natural way, the value of the shape parameter in the RBFs employed in the approximation may be included in the unknowns to be determined. The …

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Adsorption Of Tnt, Dnan, Nto, Fox7, And Nq Onto Cellulose, Chitin, And Cellulose Triacetate. Insights From Density Functional Theory Calculations, Guido Todde, Sanjiv K. Jha, Gopinath Subramanian, Manoj K. Shula Feb 2018

Adsorption Of Tnt, Dnan, Nto, Fox7, And Nq Onto Cellulose, Chitin, And Cellulose Triacetate. Insights From Density Functional Theory Calculations, Guido Todde, Sanjiv K. Jha, Gopinath Subramanian, Manoj K. Shula

Faculty Publications

Insensitive munitions (IM) compounds such as DNAN (2,4-dinitroanisole), NTO (3-nitro-1,2,4-triazol-5-one), NQ (nitroguanidine), and FOX7 (1,1-diamino-2,2-dinitroethene) reduce the risk of accidental explosions due to shock and high temperature exposure. These compounds are being used as replacements for sensitive munition compounds such as TNT (2,4,6-trinitromethylbenzene) and RDX (1,3,5-hexahydro-1,3,5-trinitro-1,3,5-triazine). NTO and NQ in IM compounds are more soluble than TNT or RDX, hence they can easily spread in the environment and get dissolved if exposed to precipitation. DNAN solubility is comparable to TNT solubility. Cellulosic biomass, due to its abundance in the environment and its chemical structure, has a high probability of adsorbing …

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Copper-Doped Lithium Triborate (Lib3o5) Crystals: A Photoluminescence, Thermoluminescence, And Electron Paramagnetic Resonance Study, Brant E. Kananen, John W. Mcclory, Nancy C. Giles, Larry E. Halliburton Feb 2018

Copper-Doped Lithium Triborate (Lib3o5) Crystals: A Photoluminescence, Thermoluminescence, And Electron Paramagnetic Resonance Study, Brant E. Kananen, John W. Mcclory, Nancy C. Giles, Larry E. Halliburton

Faculty Publications

When doped with copper ions, lithium borate materials are candidates for use in radiation dosimeters. Copper-doped lithium tetraborate (Li2B4O7) crystals have been widely studied, but little is known thus far about copper ions in lithium triborate (LiB3O5) crystals. In the present investigation, Cu+ ions (3d10) were diffused into an undoped LiB3O5 crystal at high temperature. These ions occupy both Li+ and interstitial positions in the crystal. A photoluminescence (PL) band peaking near 387 nm and a photoluminescence excitation (PLE) band peaking near 273 nm verify that a portion of these Cu+ ions are located at regular Li+ sites. After an …

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Does The Test Work? Evaluating A Web-Based Language Placement Test, Avizia Long, Sun-Young Shin, Kimberly Geeslin, Erik Willis Feb 2018

Does The Test Work? Evaluating A Web-Based Language Placement Test, Avizia Long, Sun-Young Shin, Kimberly Geeslin, Erik Willis

Faculty Publications

In response to the need for examples of test validation from which everyday language programs can benefit, this paper reports on a study that used Bachman’s (2005) assessment use argument (AUA) framework to examine evidence to support claims made about the intended interpretations and uses of scores based on a new web-based Spanish language placement test. The test, which consisted of 100 items distributed across five item types (sound discrimination, grammar, listening comprehension, reading comprehension, and vocabulary), was tested with 2,201 incoming first-year and transfer students at a large, Midwestern public university. Analyses of internal consistency and validity revealed the …

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The Ecosystem Baseline For Particle Flux In The Northern Gulf Of Mexico, S.L.C. Giering, Beizhan Yan, Vernon Asper, Arne-R. Diercks, Jeff Chanton, Masha Pitiranggon, U. Passow Jan 2018

The Ecosystem Baseline For Particle Flux In The Northern Gulf Of Mexico, S.L.C. Giering, Beizhan Yan, Vernon Asper, Arne-R. Diercks, Jeff Chanton, Masha Pitiranggon, U. Passow

Faculty Publications

Response management and damage assessment during and after environmental disasters such as the Deepwater Horizon (DWH) oil spill require an ecological baseline and a solid understanding of the main drivers of the ecosystem. During the DWH event, a large fraction of the spilled oil was transported to depth via sinking marine snow, a routing of spilled oil unexpected to emergency response planners. Because baseline knowledge of particle export in the Northern Gulf of Mexico and how it varies spatially and temporally was limited, we conducted a detailed assessment of the potential drivers of deep (~1400 m depth) particle fluxes during …

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Statistical Photocalibration Of Photodetectors For Radiometry Without Calibrated Light Sources, Nicholas J. Yielding, Stephen C. Cain, Michael D. Seal Jan 2018

Statistical Photocalibration Of Photodetectors For Radiometry Without Calibrated Light Sources, Nicholas J. Yielding, Stephen C. Cain, Michael D. Seal

Faculty Publications

Calibration of CCD arrays for identifying bad pixels and achieving nonuniformity correction is commonly accomplished using dark frames. This kind of calibration technique does not achieve radiometric calibration of the array since only the relative response of the detectors is computed. For this, a second calibration is sometimes utilized by looking at sources with known radiances. This process can be used to calibrate photodetectors as long as a calibration source is available and is well-characterized. A previous attempt at creating a procedure for calibrating a photodetector using the underlying Poisson nature of the photodetection required calculations of the skewness of …

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Metastable Ar(1s5) Density Dependence On Pressure And Argon-Helium Mixture In A High Pressure Radio Frequency Dielectric Barrier Discharge, Daniel J. Emmons, David E. Weeks, Ben Eshel, Glen P. Perram Jan 2018

Metastable Ar(1s5) Density Dependence On Pressure And Argon-Helium Mixture In A High Pressure Radio Frequency Dielectric Barrier Discharge, Daniel J. Emmons, David E. Weeks, Ben Eshel, Glen P. Perram

Faculty Publications

Simulations of an α-mode radio frequency dielectric barrier discharge are performed for varying mixtures of argon and helium at pressures ranging from 200 to 500 Torr using both zero and one-dimensional models. Metastable densities are analyzed as a function of argon-helium mixture and pressure to determine the optimal conditions, maximizing metastable density for use in an optically pumped rare gas laser. Argon fractions corresponding to the peak metastable densities are found to be pressure dependent, shifting from approximately 15% Ar in He at 200 Torr to 10% at 500 Torr. A decrease in metastable density is observed as pressure …

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Transfer Entropy And Cumulant Based Cost As Measures Of Nonlinear Causal Relationships In Space Plasmas: Applications To D St., Jay R. Johnson, Simon Wing, Enrico Camporeale Jan 2018

Transfer Entropy And Cumulant Based Cost As Measures Of Nonlinear Causal Relationships In Space Plasmas: Applications To D St., Jay R. Johnson, Simon Wing, Enrico Camporeale

Faculty Publications

It is well known that the magnetospheric response to the solar wind is nonlinear. Information theoretical tools such as mutual information, transfer entropy, and cumulant based analysis are able to characterize the nonlinearities in the system. Using cumulant based cost, we show that nonlinear significance of D st peaks at 3–12 hours lags that can be attributed to VBs which also exhibit similar behavior. However, the nonlinear significance that peaks at lags 25, 50, and 90 hours can be attributed to internal dynamics, which may be related to the relaxation of the ring current. These peaks are absent in the …

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A Hierarchical Feature Extraction Model For Multi-Label Mechanical Patent Classification, Jie Hu, Shaobo Li, Jianjun Hu, Guanci Yang Jan 2018

A Hierarchical Feature Extraction Model For Multi-Label Mechanical Patent Classification, Jie Hu, Shaobo Li, Jianjun Hu, Guanci Yang

Faculty Publications

Various studies have focused on feature extraction methods for automatic patent classification in recent years. However, most of these approaches are based on the knowledge from experts in related domains. Here we propose a hierarchical feature extraction model (HFEM) for multi-label mechanical patent classification, which is able to capture both local features of phrases as well as global and temporal semantics. First, a n-gram feature extractor based on convolutional neural networks (CNNs) is designed to extract salient local lexical-level features. Next, a long dependency feature extraction model based on the bidirectional long–short-term memory (BiLSTM) neural network model is proposed to …

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Deeply-Sourced Formate Fuels Sulfate Reducers But Not Methanogens At Lost City Hydrothermal Field, Susan Q. Lang, Gretchen L. Früh-Green, Stefano M. Bernasconi, William J. Brazelton, Matthew O. Schrenk, Julia M. Mcgonigle Jan 2018

Deeply-Sourced Formate Fuels Sulfate Reducers But Not Methanogens At Lost City Hydrothermal Field, Susan Q. Lang, Gretchen L. Früh-Green, Stefano M. Bernasconi, William J. Brazelton, Matthew O. Schrenk, Julia M. Mcgonigle

Faculty Publications

Hydrogen produced during water-rock serpentinization reactions can drive the synthesis of organic compounds both biotically and abiotically. We investigated abiotic carbon production and microbial metabolic pathways at the high energy but low diversity serpentinite-hosted Lost City hydrothermal field. Compound-specific 14C data demonstrates that formate is mantle-derived and abiotic in some locations and has an additional, seawater-derived component in others. Lipids produced by the dominant member of the archaeal community, the Lost City Methanosarcinales, largely lack 14C, but metagenomic evidence suggests they cannot use formate for methanogenesis. Instead, sulfate-reducing bacteria may be the primary consumers of formate in Lost City chimneys. …

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On The Formation Mechanisms Of Compact Elliptical Galaxies, Anna Ferré-Mateu, Duncan Forbes, Aaron Romanowsky, Joachim Janz, Christopher Dixon Jan 2018

On The Formation Mechanisms Of Compact Elliptical Galaxies, Anna Ferré-Mateu, Duncan Forbes, Aaron Romanowsky, Joachim Janz, Christopher Dixon

Faculty Publications

In order to investigate the formation mechanisms of the rare compact elliptical (cE) galaxies, we have compiled a sample of 25 cEs with good SDSS spectra, covering a range of stellar masses, sizes and environments. They have been visually classified according to the interaction with their host, representing different evolutionary stages. We have included clearly disrupted galaxies, galaxies that despite not showing signs of interaction are located close to a massive neighbour (thus are good candidates for a stripping process), and cEs with no host nearby. For the latter, tidal stripping is less likely to have happened and instead they …

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Effects Of Edge Inclination Angles On Whispering-Gallery Modes In Printable Wedge Microdisk Lasers, Cong Chen, Lei Wan, Hengky Chandrahalim Jan 2018

Effects Of Edge Inclination Angles On Whispering-Gallery Modes In Printable Wedge Microdisk Lasers, Cong Chen, Lei Wan, Hengky Chandrahalim

Faculty Publications

The ink-jet technique was developed to print the wedge polymer microdisk lasers. The characterization of these lasers was implemented using a free-space optics measurement setup. It was found that disks of larger edge inclination angles have a larger free spectral range (FSR) and a lower resonance wavelength difference between the fundamental transverse electric (TE) and transverse magnetic (TM) whispering-gallery modes (WGMs). This behavior was also confirmed with simulations based on the modified Oxborrow’s model with perfectly matched layers (PMLs), which was adopted to accurately calculate the eigenfrequencies, electric field distributions, and quality parameters of modes in the axisymmetric microdisk resonators. …

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Hydrothermal Stamp On The Oceans, Susan Q. Lang Jan 2018

Hydrothermal Stamp On The Oceans, Susan Q. Lang

Faculty Publications

The composition of the oceans is altered by hydrothermal circulation. These chemical factories sustain microbial life, which in turn alters the chemistry of the fuids that enter the ocean. A decade of research details this complex interchange.

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Modeling The Disappearance Of The Neanderthals Using Concepts Of Population Dynamics And Ecology, Michael F. Roberts, Stephen E. Bricher Jan 2018

Modeling The Disappearance Of The Neanderthals Using Concepts Of Population Dynamics And Ecology, Michael F. Roberts, Stephen E. Bricher

Faculty Publications

Current hypotheses regarding the disappearance of Neanderthals (NEA) in Europe fall into two main categories: climate change, and competition. Here we review current research and existing mathematical models that deal with this question, and we propose an approach that incorporates and permits the investigation of the current hypotheses. We have developed a set of differential equations that model population dynamics of anatomically modern humans (AMH) and NEA, their ecological relations to prey species, and their mutual interactions. The model allows investigators to explore each of the two main categories or combinations of both, as well as various forms of competition …

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Unconfined Hypogene Evaporite Karst: West Texas And Southeastern New Mexico, Usa, Kevin W. Stafford, Jon T. Ehrhart, Adam F. Majzoub, Jessica M. Shields, Wesley A. Brown Jan 2018

Unconfined Hypogene Evaporite Karst: West Texas And Southeastern New Mexico, Usa, Kevin W. Stafford, Jon T. Ehrhart, Adam F. Majzoub, Jessica M. Shields, Wesley A. Brown

Faculty Publications

Diverse karst phenomena occur throughout the Gypsum Plain where the Castile Formation crops out over ~1800 km2 in West Texas and southeastern New Mexico. Hypergene karst is extensive and widespread, while traditional hypogene karst manifestations (both caves and intrastratal dissolution) occur in high frequency in the western outcrop region where surface denudation has been the greatest so as to induce surficial breaching. Unconfined hypogene karst occurrences have been recently identified, including two general variations: 1) artesian-like discharge features; and 2) venting structures. Artesian-like discharge features arise at surficially-breached hypogene caves and through high permeability regions on the margins of …

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Site Factors Influence On Herbaceous Understory Diversity In East Texas Pinus Palustris Savannas, Brooke Mccalip, Brian Oswald, Kathryn R. Kidd, Yuhi Weng, Kenneth Farrish Phd Jan 2018

Site Factors Influence On Herbaceous Understory Diversity In East Texas Pinus Palustris Savannas, Brooke Mccalip, Brian Oswald, Kathryn R. Kidd, Yuhi Weng, Kenneth Farrish Phd

Faculty Publications

Longleaf pine (Pinus palustris) savannas were once dominant across the southeastern U.S., including East Texas and parts of western and central Louisiana. The diverse understory associated with these historical savannas may occasionally be seen today, but not often in longleaf pine ecosystems. This project aimed to define east Texas site characteristics that are necessary to support these ecosystems with a dense and diverse herbaceous understory with little to no midstory cover. Fifty-nine plots across three study sites were established to evaluate the influence of overstory cover, basal area, aspect, elevation, and slope on the number of plant genera present. Forest …

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Accuracy Of Unmanned Aerial System (Drone) Height Measurements, Daniel Unger, I-Kuai Hung, David Kulhavy, Yanli Zhang, Kai Busch-Peterson Jan 2018

Accuracy Of Unmanned Aerial System (Drone) Height Measurements, Daniel Unger, I-Kuai Hung, David Kulhavy, Yanli Zhang, Kai Busch-Peterson

Faculty Publications

Vertical height estimates of earth surface features using an Unmanned Aerial System (UAS) are important in natural resource management quantitative assessments. An important research question concerns both the accuracy and precision of vertical height estimates acquired with a UAS and to determine if it is necessary to land a UAS between individual height measurements or if GPS derived height versus barometric pressure derived height while using a DJI Phantom 3 would affect height accuracy and precision. To examine this question, height along a telescopic height pole on the campus of Stephen F. Austin State University (SFASU) were estimated at 2, …

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Recommender Systems For Large-Scale Social Networks: A Review Of Challenges And Solutions, Magdalini Eirinaki, Jerry Gao, Iraklis Varlamis, Konstantinos Tserpes Jan 2018

Recommender Systems For Large-Scale Social Networks: A Review Of Challenges And Solutions, Magdalini Eirinaki, Jerry Gao, Iraklis Varlamis, Konstantinos Tserpes

Faculty Publications

Social networks have become very important for networking, communications, and content sharing. Social networking applications generate a huge amount of data on a daily basis and social networks constitute a growing field of research, because of the heterogeneity of data and structures formed in them, and their size and dynamics. When this wealth of data is leveraged by recommender systems, the resulting coupling can help address interesting problems related to social engagement, member recruitment, and friend recommendations.In this work we review the various facets of large-scale social recommender systems, summarizing the challenges and interesting problems and discussing some of the …

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Shelf Cross-Shore Flows Under Storm-Driven Conditions: Role Of Stratification, Shoreline Orientation, And Bathymetry., Xiaodong Wu, Nirnimesh Kumar, George Voulgaris Jan 2018

Shelf Cross-Shore Flows Under Storm-Driven Conditions: Role Of Stratification, Shoreline Orientation, And Bathymetry., Xiaodong Wu, Nirnimesh Kumar, George Voulgaris

Faculty Publications

Numerical simulations are used to study the response of Long Bay, SC (USA), a typical coastal embayment with curved coastline located on the South Atlantic Bight, to realistic, climatologically defined, synoptic storm forcing. Synoptic storms, consisting of cold and warm 25 fronts as well as tropical storms, are used as forcing under both mixed and stratified initial conditions. The analysis focuses on the development of cross-shore shelf circulation and the relative contributions of regionally defined cross-shore winds and alongshore bathymetric variation. The simulation results show that, under stratified conditions, the regionally defined offshore directed wind component promotes upwelling during the …

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In Praise Of The Catenary, Fred Behroozi Jan 2018

In Praise Of The Catenary, Fred Behroozi

Faculty Publications

When a chain hangs loosely from its end points, it takes the familiar form known as the catenary. Power lines, clothes lines, and chain links are familiar examples of the catenary in everyday life. Nevertheless, the subject is conspicuously absent from current introductory physics and calculus courses.1 Even in upper-level physics and math courses, the catenary equation is usually introduced as an example of hyperbolic functions or discussed as an application of the calculus of variations. We present a new derivation of the catenary equation that is suitable for introductory physics and mathematics courses.

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Tremain Equiangular Tight Frames, Matthew C. Fickus, John Jasper, Dustin G. Mixon, Jesse D. Peterson Jan 2018

Tremain Equiangular Tight Frames, Matthew C. Fickus, John Jasper, Dustin G. Mixon, Jesse D. Peterson

Faculty Publications

Equiangular tight frames provide optimal packings of lines through the origin. We combine Steiner triple systems with Hadamard matrices to produce a new infinite family of equiangular tight frames. This in turn leads to new constructions of strongly regular graphs and distance-regular antipodal covers of the complete graph.

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The Ecosystem Baseline For Particle Flux In The Northern Gulf Of Mexico, S. L.C. Giering, B. Yan, Julia Sweet, V. Asper, A. Diercks, J. P. Chanton, M. Pitiranggon, Uta Passow Jan 2018

The Ecosystem Baseline For Particle Flux In The Northern Gulf Of Mexico, S. L.C. Giering, B. Yan, Julia Sweet, V. Asper, A. Diercks, J. P. Chanton, M. Pitiranggon, Uta Passow

Faculty Publications

Response management and damage assessment during and after environmental disasters such as the Deepwater Horizon (DWH) oil spill require an ecological baseline and a solid understanding of the main drivers of the ecosystem. During the DWH event, a large fraction of the spilled oil was transported to depth via sinking marine snow, a routing of spilled oil unexpected to emergency response planners. Because baseline knowledge of particle export in the Northern Gulf of Mexico and how it varies spatially and temporally was limited, we conducted a detailed assessment of the potential drivers of deep (~1400 m depth) particle fluxes during …

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Understanding The Structure And Resilience Of Trophic Dynamics In The Northern Gulf Of Mexico Using Network Analysis, Megumi C. Oshima, Robert T. Leaf Jan 2018

Understanding The Structure And Resilience Of Trophic Dynamics In The Northern Gulf Of Mexico Using Network Analysis, Megumi C. Oshima, Robert T. Leaf

Faculty Publications

Network analysis is a framework that allows integration and evaluation of predator-prey interactions. In the present study, we synthesized diet composition information from 94 published studies (n = 12,335 unique predator-prey interactions) that reported food habits of teleost fishes in the northern Gulf of Mexico (nGOM). Using this information, we constructed 12 weighted trophic network models using three diet metrics and four levels of taxonomic resolution of predators and prey. We evaluated network resilience to simulated random and directed taxa loss by assessing changes in topological indices "complexity," "connectance," "efficiency," and "robustness" with respect to a priori minima. We found …

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Unsupervised Machine Learning Account Of Magnetic Transitions In The Hubbard Model, Kelvin Ch'ng, Nick Vazquez, Ehsan Khatami Jan 2018

Unsupervised Machine Learning Account Of Magnetic Transitions In The Hubbard Model, Kelvin Ch'ng, Nick Vazquez, Ehsan Khatami

Faculty Publications

We employ several unsupervised machine learning techniques, including autoencoders, random trees embedding, and t-distributed stochastic neighboring ensemble (t-SNE), to reduce the dimensionality of, and therefore classify, raw (auxiliary) spin configurations generated, through Monte Carlo simulations of small clusters, for the Ising and Fermi-Hubbard models at finite temperatures. Results from a convolutional autoencoder for the three-dimensional Ising model can be shown to produce the magnetization and the susceptibility as a function of temperature with a high degree of accuracy. Quantum fluctuations distort this picture and prevent us from making such connections between the output of the autoencoder and …

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Biochemical And Structural Controls On The Decomposition Dynamics Of Boreal Upland Forest Moss Tissues, Michael Philben, Sara Butler, Sharon A. Billings, Ronald Benner, Kate A. Edwards, Susan E. Ziegler Jan 2018

Biochemical And Structural Controls On The Decomposition Dynamics Of Boreal Upland Forest Moss Tissues, Michael Philben, Sara Butler, Sharon A. Billings, Ronald Benner, Kate A. Edwards, Susan E. Ziegler

Faculty Publications

Mosses contribute an average of 20 % of boreal upland forest net primary productivity and are frequently observed to degrade slowly compared to vascular plants. If this is caused primarily by the chemical complexity of their tissues, moss decomposition could exhibit high temperature sensitivity (measured as Q10) due to high activation energy, which would imply that soil organic carbon (SOC) stocks derived from moss remains are especially vulnerable to decomposition with warming. Alternatively, the physical structure of the moss cell-wall biochemical matrix could inhibit decomposition, resulting in low decay rates and low temperature sensitivity. We tested these hypotheses by …

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Measuring Leak Rates From Abandoned Natural Gas Wells In Western Pennsylvania, John Bradshaw, Jeremy M. Slagley, Nicole Iannacchione, Matthew Lees Jan 2018

Measuring Leak Rates From Abandoned Natural Gas Wells In Western Pennsylvania, John Bradshaw, Jeremy M. Slagley, Nicole Iannacchione, Matthew Lees

Faculty Publications

The proliferation of unconventional natural gas drilling has brought considerable recent attention to the possible impacts that this new technology may have on greenhouse gas emissions. In Pennsylvania, estimates of these possible impacts are very difficult to accurately assess in large part due to the highly uncertain contribution from legacy abandoned and orphaned gas (AOG) wells. This paper outlines our work in establishing a methodology for measuring the methane leak rate from AOG wells in Western Pennsylvania. The theory and methodology of an enclosure method for measuring the methane mass leak rate from one AOG natural gas well is described. …

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Unmasking Cost Growth Behavior: A Longitudinal Study, Cory N. D'Amico, Edward D. White, Jonathan D. Ritschel, Scott R. Kozlak Jan 2018

Unmasking Cost Growth Behavior: A Longitudinal Study, Cory N. D'Amico, Edward D. White, Jonathan D. Ritschel, Scott R. Kozlak

Faculty Publications

This article examines how cost growth factors (CGF) change over a program’s acquisition life cycle for 36 Department of Defense aircraft programs. Starting from Milestone B, the authors examine CGFs at five gateways: Critical Design Review, First Flight (FF), the end of Developmental Test and Evaluation (DT&E), Initial Operational Capability, and Full Operational Capability. Each CGF is assigned a color rating based upon the program’s cost growth: Green (low), Amber (moderate), or Red (high). Significant findings include dependencies among similar CGF color ratings and cost growth occurring primarily between FF and the end of DT&E during a program’s life cycle.

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Semiconductor Color-Center Structure And Excitation Spectra: Equation-Of-Motion Coupled-Cluster Description Of Vacancy And Transition-Metal Defect Photoluminescence, Jesse J. Lutz, Xiaofeng F. Duan, Larry W. Burggraf Jan 2018

Semiconductor Color-Center Structure And Excitation Spectra: Equation-Of-Motion Coupled-Cluster Description Of Vacancy And Transition-Metal Defect Photoluminescence, Jesse J. Lutz, Xiaofeng F. Duan, Larry W. Burggraf

Faculty Publications

Valence excitation spectra are computed for deep-center silicon-vacancy defects in 3C, 4H, and 6H silicon carbide (SiC), and comparisons are made with literature photoluminescence measurements. Optimizations of nuclear geometries surrounding the defect centers are performed within a Gaussian basis-set framework using many-body perturbation theory or density functional theory (DFT) methods, with computational expenses minimized by a QM/MM technique called SIMOMM. Vertical excitation energies are subsequently obtained by applying excitation-energy, electron-attached, and ionized equation-of-motion coupled-cluster (EOMCC) methods, where appropriate, as well as time-dependent (TD) DFT, to small models including only a few atoms adjacent to the defect center. We consider the …

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