Physical Sciences and Mathematics Commons^™

The First Open-Source General Relativistic Force-Free Electrodynamics Code, Maria Babiuc-Hamilton, Zach Etienne, Mew-Bing Wan

Maria C. Babiuc-Hamilton

We are writing the first open-source, general relativistic force-free electrodynamics code: GiRaFFE. The goal is to numerically simulate neutron star and black hole magnetospheres. The GiRaFFE is alive! It has passed a number of 1D code validation tests, and 3D tests are underway. We plan to release the code and test suite initial data routines open-source to the community.

Towards A Standardized Characteristic Extraction Tool, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Knowing the precise details of the gravitational wave signature obtained from numerical simulations of binary black hole mergers is a key requirement for meaningful detection and scientific interpretation of the data. However, the waveforms are not easy to be accurately computed. The importance of this problem to the future of gravitational wave astronomy is well recognized. Cauchy-Characteristic Extraction (CCE) is the most precise and refined extraction method available. The CCE technique connects the strong-field Cauchy evolution of the spacetime near the merger to the characteristic evolution to future null infinity where the waveform is extracted in an unambiguous way. Recently, …

Simulating Magnetospheres With Numerical Relativity: The Giraffe Code, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Numerical Relativity is successful in the simulation of black holes and gravitational waves. In recent years, teams have tackled the problem of the interaction of gravitational and electromagnetic waves. We developed a new code for the numerical simulation of neutron and black hole magnetospheres, using the FFE formalism. We tested the performance of the new code named GiRaFFE, in 1D and 3D test suits. We will study magnetospheres, focusing on jets by the Blandford -Znajek mechanism.

Cauchy-Characteristic Patching With Improved Accuracy, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Cauchy-characteristic extractions (CCE) avoids the errors due to extraction at finite worldtube. The Cauchy and the characteristic approaches have complementary strengths and weaknesses. Unification of the two methods is a promising way of combining the strengths of both formalisms.

Towards A Fully Nonlinear Cauchy Characteristic Extraction, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

The artificial finite outer boundary present in Cauchy codes introduce two sources of error: The outer boundary condition and waveform extraction at an inner worldtube. The problem of proper boundary condition for a radiating system can be solved only by extension to Ι+ (conformal compactification). Cauchy Characteristic Extraction (CCE) offers a means to avoid these errors.

Towards Improved Accuracy Of Gravitational Waves Extraction, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Results in developing two new methods to improve the accuracy of waveform extraction using characteristic evolution. Numerical method: circular boundaries, with angular dissipation in the characteristic code. Geometric method: computation of Weyl tensor component Y4 at null infinity, in a conformally compactified treatment. Comparison and calibration in tests problems based upon linearized waves.

Gravitational & Electromagnetic Waves On The Null Cone, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Bondi (1962) proved mathematically the existence of gravitational waves at null infinity. He found an exact solution of Einstein equations. Within this metric, he calculated the loss of mass due to the emission of gravitational waves. The mas of a system is constant if and only if there is no news. If there is news, the mass decreases as long as there are news.

Testing A Model For The Well-Posedness Of The Cauchy-Characteristic Problem In Bondi Coordinates, Maria Babiuc-Hamilton, Jeff Winicour

Maria C. Babiuc-Hamilton

Gravity waves reveal colliding black holes, galaxies, the birth of a black hole in a supernova and the growth pains of our universe. Gravitational waves are unambiguous measured only at future null infinity.

Nitrogen Fertilizer Rate Effects On Soil Organic Carbon In Iowa Continuous Corn And Corn-Soybean Systems, Hanna J. Poffenbarger, Daniel W. Barker, Matthew J. Helmers, Fernando E. Miguez, John E. Sawyer, Johan Six, Michael J. Castellano

John E. Sawyer

Nitrogen fertilizer rate is a key factor affecting soil organic C (SOC) in corn-based cropping systems. The objective of this study was to determine the change in SOC in response to long-term N rates for continuous corn and corn-soybean cropping systems at two sites in Iowa. Soil samples were collected to a depth of 15 cm in 1999 and again in 2014 after 15 years of corn N rate treatments ranging from 0 to 269 kg ha^-1. The soil samples were analyzed for total C and N concentrations. For continuous corn at both sites, the average annual change …

Steps Towards A Nonlinear Cauchy-Characteristic Code Patching, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Cauchy-characteristic extractions (CCE) avoids the errors due to extraction at finite worldtube. The Cauchy and the characteristic approaches have complementary strengths and weaknesses. Unification of the two methods is a promising way of combining the strengths of both formalisms.

Characteristics Of Gravitational And Electromagnetic Radiation, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Gravitational waves from the early universe are detectable, but detection is difficult. The strain is extremely small of magnitude 10-3 the width of a proton. There are detection and computational challenges.

An Analysis Of The Gravitational Waves Null Memory, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Gravitational wave astronomy sees (hears) gravitational waves by observing the phenomena of gravitational and electromagnetic memory, and the formation of trapped surfaces and horizons.

Tools For Gravitational Wave Astronomy, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Gravitational waves have been confirmed. Tools are available for their study, including the Einstein Toolkit, SimulationTools and the SXS Gravitational Waveform Database.

Gravity & Electromagnetism On The Null Cone, Maria Babiuc-Hamilton

Maria C. Babiuc-Hamilton

Gravitational and electromagnetic radiation travel along light rays, which are principal null directions in space-time. They are characteristic surfaces of Einstein and Maxwell equations. In characteristic coordinates, the field is described by ordinary differential equations.

A New Algorithm For The Numerical Computation Of Gravitational Waves, Maria Babiuc-Hamilton, Jeff Winicour

Maria C. Babiuc-Hamilton

With gravitational waves, Gravitational Wave Astronomy can “see” colliding back holes and galaxies, the birth of a black hole in a supernova, the growth pains of our universe and the structure of spacetime.

A Hyperbolic Solver For Black Hole Initial Data In Numerical Relativity, Maria Babiuc-Hamilton, Jeff Winicour, I. Racz

Maria C. Babiuc-Hamilton

Initial data in numerical relativity. The constraints are formulated as elliptic equations, parabolic equations and strongly hyperbolic equations. This presentation is about a different approach to initial data for black holes, the strongly hyperbolic method.

New Genera And Species Of Fossil Marine Amioid Fishes (Actinopterygii, Holostei) From The Late Cretaceous Agoult Locality In Southeastern Morocco, Mark V. H. Wilson, Alison M. Murray, Terry C. Grande

Terry Grande

No abstract provided.

Basics Behind Answer Sets, Yuliya Lierler

Yuliya Lierler

No abstract provided.

Methods For Scalar-On-Function Regression, Philip T. Reiss, Jeff Goldsmith, Han Lin Shang, R. Todd Ogden

Philip T. Reiss

Jessicahlawrencemastersportfolio.Pdf, Jessicah Lawrence

Jessicah Lawrence

No abstract provided.

Impulse-Momentum Diagrams, David Rosengrant

David Rosengrant

Multiple representations are a valuable tool to help students learn and understand physics concepts. Furthermore, representations help students learn how to think and act like real scientists. These representations include: pictures, free‐body diagrams, energy bar charts, electrical circuits, and, more recently, computer simulations and animations. However, instructors have limited choices when they want to help their students understand impulse and momentum. One of the only available options is the impulse‐momentum bar chart. The bar charts can effectively show the magnitude of the momentum as well as help students understand conservation of momentum, but they do not easily show the actual …

Following Student Gaze Patterns In Physical Science Lectures, David Rosengrant, Doug Hearrington, Kerriann Alvarado, Danielle Keeble

David Rosengrant

This study investigates the gaze patterns of undergraduate college students attending a lecture-based physical science class to better understand the relationships between gaze and focus patterns and student attention during class. The investigators used a new eye-tracking product; Tobii Glasses. The glasses eliminate the need for subjects to focus on a computer screen or carry around a backpack-sized recording device, thus giving an investigator the ability to study a broader range of research questions. This investigation includes what students focus on in the classroom (i.e. demonstrations, instructor, notes, board work, and presentations) during a normal lecture, what diverts attention away …

Comparing Experts And Novices In Solving Electrical Circuit Problems With The Help Of Eye-Tracking, David Rosengrant, Colin Thomson, Taha Mzoughi

David Rosengrant

In order to help introductory physics students understand and learn to solve problems with circuits, we must first understand how they differ from experts. This preliminary study focuses on problem-solving dealing with electrical circuits. We investigate difficulties novices have with circuits and compare their work with those of experts. We incorporate the use of an eye-tracker to investigate any possible differences or similarities on how experts and novices solve electrical circuit problems. Our results show similarities in gaze patterns among all subjects on the components of the circuit. We further found that experts would look back at the circuit while …

Pre-Service Physics Teachers And Physics Education Research, David Rosengrant

David Rosengrant

Training pre-service teachers requires, among other things, content knowledge, pedagogical skills and pedagogical content knowledge. Teacher preparation programs have little, if any spare time to add more courses/activities to their program. However, I argue in this paper that we, as educators, must enhance the amount of physics education research in our pre-service physics teacher training programs. In this study, I analyze the results of two different types of exposure to physics education research (PER) from two different groups of pre-service physics teachers in our masters of arts and teaching program. The preliminary results show, for example that the PER helped …

Experiences With Scala Across The College-Level Curriculum, Konstantin Läufer, George K. Thiruvathukal, Mark C. Lewis

George K. Thiruvathukal

Various hybrid-functional languages, designed to balance compile-time error detection, conciseness, and performance, have emerged. Scala, e.g., is interoperable with Java and has become an early leader in adoption, especially in the start-up and open-source spaces. As educators, we have recognized Scala’s value as a teaching language across the CS curriculum. In CS1, the read-eval-print loop and simple, uniform syntax aid programming in the small. In CS2, higher-order methods allow concise, efficient manipulation of collections. In a programming languages course, advanced constructs facilitate the separation of concerns, program representation and interpretation, and concurrent programming. In advanced applied courses, language mechanisms and …

A Distributed Graph Approach For Pre-Processing Linked Rdf Data Using Supercomputers, Michael J. Lewis, George K. Thiruvathukal, Venkatram Vishwanath, Michael J. Papka, Andrew Johnson

George K. Thiruvathukal

Efficient RDF, graph based queries are becoming more pertinent based on the increased interest in data analytics and its intersection with large, unstructured but connected data. Many commercial systems have adopted distributed RDF graph systems in order to handle increasing dataset sizes and complex queries. This paper introduces a distribute graph approach to pre-processing linked data. Instead of traversing the memory graph, our system indexes pre-processed join elements that are organized in a graph structure. We analyze the Dbpedia data-set (derived from the Wikipedia corpus) and compare our access method to the graph traversal access approach which we also devise. …

Comparison Of Visual Datasets For Machine Learning, Kent Gauen, Ryan Dailey, John Laiman, Yuxiang Zi, Nirmal Asokan, Yung-Hsiang Lu, George K. Thiruvathukal, Mei-Ling Shyu, Shu-Ching Chen

George K. Thiruvathukal

One of the greatest technological improvements in recent years is the rapid progress using machine learning for processing visual data. Among all factors that contribute to this development, datasets with labels play crucial roles. Several datasets are widely reused for investigating and analyzing different solutions in machine learning. Many systems, such as autonomous vehicles, rely on components using machine learning for recognizing objects. This paper compares different visual datasets and frameworks for machine learning. The comparison is both qualitative and quantitative and investigates object detection labels with respect to size, location, and contextual information. This paper also presents a new …

Knowledge Extraction From Metacognitive Reading Strategies Data Using Induction Trees, Christopher Taylor, Arun D. Kulkarni, Kouider Mokhtari

Arun Kulkarni

The assessment of students’ metacognitive knowledge and skills about reading is critical in determining their ability to read academic texts and do so with comprehension. In this paper, we used induction trees to extract metacognitive knowledge about reading from a reading strategies dataset obtained from a group of 1636 undergraduate college students. Using a C4.5 algorithm, we constructed decision trees, which helped us classify participants into three groups based on their metacognitive strategy awareness levels consisting of global, problem-solving and support reading strategies. We extracted rules from these decision trees, and in order to evaluate accuracy of the extracted rules, …

Using Composition Techniques To Improve Classroom Instruction And Students’ Understanding Of Proof, Christopher D. Goff

Christopher Goff

This paper describes an effort to incorporate standard composition exercises into a sophomore-level discrete mathematics class. It provides an example of how peer review can be integrated with a mathematical curriculum through the writing of proofs.

Generalized Twisted Quantum Doubles And The Mckay Correspondence, Christopher D. Goff, Geoffrey Mason

Christopher Goff

We consider a class of quasiHopf algebras which we call generalized twisted quantum doubles. They are abelian extensions H=C[G¯]∗⋈C[G] (G is a finite group, G¯ a homomorphic image, and * denotes the dual algebra), possibly twisted by a 3-cocycle, and are a natural generalization of the twisted quantum double construction of Dijkgraaf, Pasquier and Roche. We show that if G is a subgroup of SU2(C) then H exhibits an orbifold McKay Correspondence: certain fusion rules of H define a graph with connected components indexed by conjugacy classes of G¯, each connected component being an extended affine Diagram of type ADE …