Physical Sciences and Mathematics Commons^™

Mapview And Cross Section Animations, Jason Luke

Faculty Publications

Movie 1: A series of time slices animated through the amplitude volume. Movie 2: A series of time slices animated through the semblance volume. Movie 3: Cross section animation from SW-NE through the amplitude volume. Movie 4: Cross section animation from SW-NE through the semblance volume.

Ground-State Characterizations Of Systems Predicted To Exhibit L11 Or L13 Crystal Structures, Lance J. Nelson, Gus L. W. Hart, Stefano Curtarolo

Faculty Publications

Despite their geometric simplicity, the crystal structures L11 (CuPt) and L13 (CdPt3) do not appear as ground states experimentally, except in Cu-Pt. We investigate the possibility that these phases are ground states in other binary intermetallic systems, but overlooked experimentally. Via the synergy between high-throughput and cluster-expansion computational methods, we conduct a thorough search for systems that may exhibit these phases and calculate order-disorder transition temperatures when they are predicted. High-throughput calculations predict L11 ground states in the systems Ag-Pd, Ag-Pt, Cu-Pt, Pd-Pt, Li-Pd, Li-Pt and L13 ground states in the systems Cd-Pt, Cu-Pt, Pd-Pt, Li-Pd, Li-Pt. Cluster expansions confirm …

Stable Ordered Structures Of Binary Technetium Alloys From First Principles, Gus L. W. Hart, Ohad Levy, Junkai Xue, Shidong Wang, Stefano Curtarolo

Faculty Publications

Technetium, element 43, is the only radioactive transition metal. It occurs naturally on earth in only trace amounts. Experimental investigation of its possible compounds is thus inherently difficult and limited. Half of the Tc-transition-metal systems (14 out of 28) are reported to be phase separating or lack experimental data. Using high-throughput first-principles calculations, we present a comprehensive investigation of the binary alloys of technetium with the transition metals. The calculations predict stable, ordered structures in nine of these 14 binary systems. They also predict additional compounds in all nine known compound-forming systems and in two of the five systems reported …

Computer Aided Geometric Design, Thomas W. Sederberg

Faculty Publications

This semester is the twenty-fourth time I have taught a course at Brigham Young University titled, "Computer Aided Geometric Design." When I first taught such a course in 1983, the field was young enough that no textbook covered everything that I wanted to teach, and so these notes evolved. The field now has matured to the point that several semesters worth of valuable material could be compiled. These notes, admittedly biased towards my own interests, reflect my personal preferences as to which of that material is most beneficial to students in an introductory course. I welcome anyone who has an …

Variable Object Research: Methods And Processes, Dan Broadbent

Faculty Publications

Some objects in the sky vary over time in terms of how much of their energy reaches the earth. Studying how the energy varies, and identifying any periodicities, will give clues as to what is actually happening at the source.

The purpose of this paper is to document the current methods involved in gathering and processing data, specifically on the variable object Markarian 501. The intent is that this will provide a foundation for later work to automate the process.

"Ultracold" Neutral Plasmas At Room Temperature, N. Heilmann, J. B. Peatross, Scott D. Bergeson

Faculty Publications

We report a measurement of the electron temperature in a plasma generated by a high-intensity laser focused into a jet of neon. The 15 eV electron temperature is determined using an analytic solution of the plasma equations assuming local thermodynamic equilibrium, initially developed for ultracold neutral plasmas. We show that this analysis method accurately reproduces more sophisticated plasma simulations in our temperature and density range. While our plasma temperatures are far outside the typical "ultracold" regime, the ion temperature is determined by the plasma density through disorder-induced heating just as in ultracold neutral plasma experiments. Based on our results, we …

A Synthetic Document Image Dataset For Developing And Evaluating Historical Document Processing Methods, Daniel Walker, William Lund, Eric Ringger

Faculty Publications

Document images accompanied by OCR output text and ground truth transcriptions are useful for developing and evaluating document recognition and processing methods, especially for historical document images. Additionally, research into improving the performance of such methods often requires further annotation of training and test data (e.g., topical document labels). However, transcribing and labeling historical documents is expensive. As a result, existing real-world document image datasets with such accompanying resources are rare and often relatively small. We introduce synthetic document image datasets of varying levels of noise that have been created from standard (English) text corpora using an existing document degradation …

Ordered Phases In Ruthenium Binary Alloys From High-Throughput First-Principles Calculations, Gus L. W. Hart, Lance J. Nelson, Michal Jahnátek, Ohad Levy, Roman V. Chepulskii, J. Xue, Stephano Curtarolo

Faculty Publications

Despite the increasing importance of ruthenium in numerous technological applications, e.g., catalysis and electronic devices, experimental and computational data on its binary alloys are sparse. In particular, data are scant on those binary systems believed to be phase-separating. We performed a comprehensive study of ruthenium binary systems with the 28 transition metals, using high-throughput first-principles calculations. These computations predict novel unsuspected compounds in 7 of the 16 binary systems previously believed to be phase-separating and in two of the three systems reported with only a high-temperature σ phase. They also predict a few unreported compounds in five additional systems and …

A Speculative Approach To Parallelization In Particle Swarm Optimization, Matthew Gardner, Andrew Mcnabb, Kevin Seppi

Faculty Publications

Particle swarm optimization (PSO) has previously been parallelized primarily by distributing the computation corresponding to particles across multiple processors. In these approaches, the only benefit of additional processors is an increased swarm size. However, in many cases this is not efficient when scaled to very large swarm sizes (on very large clusters). Current methods cannot answer well the question: “How can 1000 processors be fully utilized when 50 or 100 particles is the most efficient swarm size?” In this paper we attempt to answer that question with a speculative approach to the parallelization of PSO that we refer to as …

Guiding The Experimental Discovery Of Magnesium Alloys, Richard H. Taylor, Gus L. W. Hart, Stefano Curtarolo

Faculty Publications

Magnesium alloys are among the lightest structural materials known and are of considerable technological interest. To develop superior magnesium alloys, experimentalists must have a thorough understanding of the concentration-dependent precipitates that form in a given system, and hence, the thermodynamic stability of crystal phases must be determined. This information is often lacking but can be supplied by first-principles methods. Within the high-throughput framework, AFLOW, T = 0 K ground-state predictions are made by scanning a large set of known candidate structures for thermodynamic (formation energy) minima. The following 34 systems are investigated: AlMg, AuMg, CaMg, CdMg, CuMg, FeMg , GeMg, …

Polymer Molded Templates For Nanostructured Amorphous Silicon Photovoltaics, Lei Pei, Amy Balls, Cary Tippets, Jonathan Abbott, Matthew R. Linford, David D. Allred, Richard R. Vanfleet, Robert C. Davis, Jian Hu, Arun Madan

Faculty Publications

Here, the authors report the fabrication of transparent polymer templates for nanostructured amorphous silicon photovoltaics using low-cost nanoimprint lithography of polydimethylsiloxane. The template contains a square two-dimensional array of high-aspect-ratio nanoholes (300 nm diameter by 1 µm deep holes) on a 500X500 nm^2 pitch. A 100 nm thick layer of a-Si:H was deposited on the template surface resulting in a periodically nanostructured film. The optical characterization of the nanopatterned film showed lower light transmission at 600-850 nm wavelengths and lower light reflection at 400-650 nm wavelengths, resulting in 20% higher optical absorbance at AM 1.5 spectral irradiance versus a nonpatterned …

Density And Temperature Scaling Of Disorder-Induced Heating In Ultracold Plasmas, Scott D. Bergeson, A. Denning, M. Lyon, F. Robicheaux

Faculty Publications

We report measurements and simulations of disorder-induced heating in ultracold neutral plasmas. Fluorescence from plasma ions is excited using a detuned probe laser beam while the plasma relaxes from its initially disordered nonequilibrium state. This method probes the wings of the ion velocity distribution. The simulations yield information on time-evolving plasma parameters that are difficult to measure directly and make it possible to connect the fluorescence signal to the rms velocity distribution. The disorder-induced heating signal can be used to estimate the electron and ion temperatures ~100 ns after the plasma is created. This is particularly interesting for plasmas in …

Stern-Gerlach Dynamics With Quantum Propagators, Bailey C. Hsu, Manuel Berrondo, Jean F. Van Huele

Faculty Publications

We study the quantum dynamics of a nonrelativistic neutral particle with spin in inhomogeneous external magnetic fields. We first consider fields with one-dimensional inhomogeneities, both unphysical and physical, and construct the corresponding analytic propagators. We then consider fields with two-dimensional inhomogeneities and develop an appropriate numerical propagation method. We propagate initial states exhibiting different degrees of space localization and various initial spin configurations, including both pure and mixed spin states. We study the evolution of their spin densities and identify characteristic features of spin density dynamics, such as the spatial separation of spin components, and spin localization or accumulation. We …

Understanding Streaming In Dictyostelium Discoideum: Theory Versus Experiments, J. C. Dallon, Brittany Dalton, Chelsea Malani

Faculty Publications

Recent experimental work involving Dictyostelium discoideum seems to contradict several theoretical models. Experiments suggest that localization of the release of the chemoattractant cyclic adenosine monophosphate to the uropod of the cell is important for stream formation during aggregation. Yet several mathematical models are able to reproduce streaming as the cells aggregate without taking into account localization of the chemoattractant. A careful analysis of the experiments and the theory suggests the two major features of the system which are important to stream formation are random cell motion and chemotaxis to regions of higher cell density. Random cell motion acts to reduce …

Detailed Requirements For Robots In Autism Therapy, Alan Atherton, Bonnie Brinton, Mark Colton, Nicole Giullian, Michael A. Goodrich, Daniel Ricks

Faculty Publications

Robot-based autism therapy is a rapidly developing area of research, with a wide variety of robots being developed for use in clinical settings. Specific, detailed requirements for robots and user interfaces are needed to provide guidelines for the creation of robots that more effectively assist therapists in autism therapy. This paper enumerates a set of requirements for a clinical humanoid robot and the associated human interface. The design of two humanoid robots and an intuitive and flexible user interface for use by therapists in the treatment of children with autism are described.

Beyond Robot Fan-Out: Towards Multi-Operator Supervisory Control, Michael A. Goodrich, Yisong Guo, Jonathan M. Whetten

Faculty Publications

This paper explores multi-operator supervisory control (MOSC) of multiple independent robots using two complementary approaches: a human factors experiment and an agent-based simulation. The experiment identifies two task and environment limitations on MOSC: task saturation and task diffusion. It also identifies the correlation between task specialization and performance, and the possible existence of untapped spare capacity that emerges when multiple operators coordinate. The presence of untapped spare capacity is explored using agent-based simulation, resulting in evidence which suggests that operators may be more effective when they operate at less than maximum capacity.

Supporting Wilderness Search And Rescue With Integrated Intelligence: Autonomy And Information At The Right Time And The Right Place, Michael A. Goodrich, Lanny Lin, Bryan S. Morse, Michael Roscheck

Faculty Publications

Current practice in Wilderness Search and Rescue (WiSAR) is analogous to an intelligent system designed to gather and analyze information to find missing persons in remote areas. The system consists of multiple parts — various tools for information management (maps, GPS, etc) distributed across personnel with different skills and responsibilities. Introducing a camera-equipped mini-UAV into this task requires autonomy and information technology that itself is an integrated intelligent system to be used by a sub-team that must be integrated into the overall intelligent system. In this paper, we identify key elements of the integration challenges along two dimensions: (a) attributes …

Diode Properties Of Nanotube Networks, David D. Allred, Bryan Hicks, Stephanie Getty

Faculty Publications

Single-walled carbon nanotubes (SWCNT) were prepared using iron catalysts deposited by indirect evaporation on silicon substrate covered with 500 nm-thick thermal oxide. Diode SWCNT devices have been fabricated using Au and Al, as the asymmetric metal contacts, and a random network of metallic and semiconducting nanotubes as the device channel. No effort was made to align the SWCNTs or to eliminate metallic nanotubes in our devices. Asymmetric voltage-current behavior was seen. Current rectification was observed in the source-drain bias range of -3 V to +3 V. Rectification was somewhat surprising since, although metallic tubes are in the minority (~ 1/3), …

On The Use Of Cartographic Projections In Visualizing Phylogenetic Treespace, Mark J. Clement, Quinn O. Snell, Kenneth Sundberg

Faculty Publications

Phylogenetic analysis is becoming an increasingly important tool for biological research. Applications include epidemiological studies, drug development, and evolutionary analysis. Phylogenetic search is a known NP-Hard problem. The size of the data sets which can be analyzed is limited by the exponential growth in the number of trees that must be considered as the problem size increases. A better understanding of the problem space could lead to better methods, which in turn could lead to the feasible analysis of more data sets. We present a definition of phylogenetic tree space and a visualization of this space that shows significant exploitable …

Parallel Active Learning: Eliminating Wait Time With Minimal Staleness, Paul Felt, Robbie Haertel, Eric K. Ringger, Kevin Seppi

Faculty Publications

A practical concern for Active Learning (AL) is the amount of time human experts must wait for the next instance to label. We propose a method for eliminating this wait time independent of specific learning and scoring algorithms by making scores always available for all instances, using old (stale) scores when necessary. The time during which the expert is annotating is used to train models and score instances–in parallel–to maximize the recency of the scores. Our method can be seen as a parameterless, dynamic batch AL algorithm. We analyze the amount of staleness introduced by various AL schemes and then …

Simultaneous Foreground, Background, And Alpha Estimation For Image Matting, Bryan S. Morse, Brian L. Price, Scott Cohen

Faculty Publications

Image matting is the process of extracting a soft segmentation of an object in an image as defined by the matting equation. Most current techniques focus largely on computing the alpha values of unknown pixels and treat computation of the foreground and background colors as an afterthought, if at all. However, for many applications, such as compositing an object into a new scene or deleting an object from the scene, the foreground and background colors are vital for an acceptable answer. We propose a method of solving for the foreground, background, and alpha of an unknown region in an image …

Geodesic Graph Cut For Interactive Image Segmentation, Bryan S. Morse, Brian L. Price, Scott Cohen

Faculty Publications

Interactive segmentation is useful for selecting objects of interest in images and continues to be a topic of much study. Methods that grow regions from foreground/background seeds, such as the recent geodesic segmentation approach, avoid the boundary-length bias of graph-cut methods but have their own bias towards minimizing paths to the seeds, resulting in increased sensitivity to seed placement. The lack of edge modeling in geodesic or similar approaches limits their ability to precisely localize object boundaries, something at which graph-cut methods generally excel. This paper presents a method for combining geodesicdistance information with edge information in a graphcut optimization …

Structure Maps For Hcp Metals From First-Principles Calculations, Gus L. W. Hart, Ohad Levy, Stefano Curtarolo

Faculty Publications

The ability to predict the existence and crystal type of ordered structures of materials from their components is a major challenge of current materials research. Empirical methods use experimental data to construct structure maps and make predictions based on clustering of simple physical parameters. Their usefulness depends on the availability of reliable data over the entire parameter space. Recent development of high-throughput methods opens the possibility to enhance these empirical structure maps by ab initio calculations in regions of the parameter space where the experimental evidence is lacking or not well characterized. In this paper we construct enhanced maps for …

Structure-Property Maps And Optimal Inversion In Configurational Thermodynamics, Gus L. W. Hart, Björn Arnold, Alejandro Díaz Ortiz, Helmut Dosch

Faculty Publications

Cluster expansions of first-principles density-functional databases in multicomponent systems are now used as a routine tool for the prediction of zero- and finite-temperature physical properties. The ability of producing large databases of various degrees of accuracy, i.e., high-throughput calculations, makes pertinent the analysis of error propagation during the inversion process. This is a very demanding task as both data and numerical noise have to be treated on equal footing. We have addressed this problem by using an analysis that combines the variational and evolutionary approaches to cluster expansions. Simulated databases were constructed ex professo to sample the configurational space in …

Characterization Of Optical Constants For Uranium From 10 To 47 Nm, Nicole Brimhall, Nicholas Herrick, David D. Allred, R. Steven Turley, Michael Ware, Justin Peatross

Faculty Publications

We use a laser high-harmonics-based extreme-ultraviolet (EUV) polarimeter to determine the optical constants of elemental uranium in the wavelength range from 10 to 47 nm. The constants are extracted from the measure ratio of p-polarized to s-polarized reflectance from a thin uranium film deposited in situ. The film thickness is inferred from a spectroscopic ellipsometry measurement of the sample after complete oxidation in room air. Uranium has been used as a high-reflectance material in the EUV. However, difficulties with oxidation prevented its careful characterization previous to this study. We find that measured optical constants for uranium vary significantly from previous …

Uav Video Coverage Quality Maps And Prioritized Indexing For Wilderness Search And Rescue, Cameron Engh, Michael A. Goodrich, Bryan S. Morse

Faculty Publications

Video-equipped mini unmanned aerial vehicles (mini-UAVs) are becoming increasingly popular for surveillance, remote sensing, law enforcement, and search and rescue operations, all of which rely on thorough coverage of a target observation area. However, coverage is not simply a matter of seeing the area (visibility) but of seeing it well enough to allow detection of targets of interest, a quality we here call “see-ability”. Video flashlights, mosaics, or other geospatial compositions of the video may help place the video in context and convey that an area was observed, but not necessarily how well or how often. This paper presents a …

Ordered Magnesium-Lithium Alloys: First-Principles Predictions, Richard H. Taylor, Gus L. W. Hart, Stefano Curtarolo

Faculty Publications

Magnesium-lithium (Mg-Li) alloys are among the lightest structural materials. Although considerable work has been done on the Mg-Li system, little is known regarding potential ordered phases. A first and rapid analysis of the system with the high-throughput method reveals an unexpected wealth of potentially stable low-temperature phases. Subsequent cluster expansions constructed for bcc and hcp superstructures extend the analysis and verify our high-throughput results. Of particular interest are those structures with greater than 13 at. % lithium, as they exhibit either partial or complete formation as a cubic structure. Order-disorder transition temperatures are predicted by Monte Carlo simulations to be …

Evaluating Models Of Latent Document Semantics In The Presence Of Ocr Errors, Daniel D. Walker, William B. Lund, Eric K. Ringger

Faculty Publications

Models of latent document semantics such as the mixture of multinomials model and Latent Dirichlet Allocation have received substantial attention for their ability to discover topical semantics in large collections of text. In an effort to apply such models to noisy optical character recognition (OCR) text output, we endeavor to understand the effect that character-level noise can have on unsupervised topic modeling. We show the effects both with document-level topic analysis (document clustering) and with word-level topic analysis (LDA) on both synthetic and real-world OCR data. As expected, experimental results show that performance declines as word error rates increase. Common …

Differences In The Mechanism Of Collagen Lattice Contraction By Myofibroblasts And Smooth Muscle Cells, J. C. Dallon, H P. Ehrlich

Faculty Publications

Both rat derived vascular smooth muscle cells (SMC) and human myofibroblasts contain $\alpha$ smooth muscle actin (SMA), but they utilize different mechanisms to contract populated collagen lattices (PCLs). The difference is in how the cells generate the force that contracts the lattices. Human dermal fibroblasts transform into myofibroblasts, expressing $\alpha$-SMA within stress fibers, when cultured in lattices that remain attached to the surface of a tissue culture dish. When attached lattices are populated with rat derived vascular SMC, the cells retain their vascular SMC phenotype. Comparing the contraction of attached PCLs when they are released from the culture dish on …

Multiscale Modeling Of Cellular Systems In Biology, J. C. Dallon

Faculty Publications

Here we review eight different multiscale modeling efforts dealing with cellular systems in biology. The first two models focus on collagen based tissue, one dealing with the biomechanical properties of the tissue and the other focusing on how the dermis is remodeled in scar tissue formation. The next two models deal with first avascular tumor growth and then the role of the vasculature in tumor growth. We then consider two models which use the Immersed Boundary method to model tissue properties and cell-cell adhesion. Finally we conclude with two models with treatments of the Cellular Potts Model. The first models …