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2017

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Articles 1 - 30 of 10260

Full-Text Articles in Physical Sciences and Mathematics

Kodysynth, Ryan Kody Dec 2017

Kodysynth, Ryan Kody

Honors Research Projects

KodySynth is a VST digital synthesizer that can be loaded into any digital audio workstation such as FL Studio, Ableton, or Garageband. The program was made using the JUCE library which helped with streamlining the process and making it easier to create clean and intuitive looking graphics. The project also needs the Maximilian Library of sounds to create the sound waves that listeners will hear when playing the synthesizer. Users will also be able to plug in a MIDI keyboard to play KodySynth. The functionalities include a choice of 5 oscillator wave types, as well as an attack, decay, sustain ...


Low Rank Perturbations Of Quaternion Matrices, Christian Mehl, Andre C.M. Ran Dec 2017

Low Rank Perturbations Of Quaternion Matrices, Christian Mehl, Andre C.M. Ran

Electronic Journal of Linear Algebra

Low rank perturbations of right eigenvalues of quaternion matrices are considered. For real and complex matrices it is well known that under a generic rank-$k$ perturbation the $k$ largest Jordan blocks of a given eigenvalue will disappear while additional smaller Jordan blocks will remain. In this paper, it is shown that the same is true for real eigenvalues of quaternion matrices, but for complex nonreal eigenvalues the situation is different: not only the largest $k$, but the largest $2k$ Jordan blocks of a given eigenvalue will disappear under generic quaternion perturbations of rank $k$. Special emphasis is also given ...


From Convergence In Measure To Convergence Of Matrix-Sequences Through Concave Functions And Singular Values, Giovanni Barbarino, Carlo Garoni Dec 2017

From Convergence In Measure To Convergence Of Matrix-Sequences Through Concave Functions And Singular Values, Giovanni Barbarino, Carlo Garoni

Electronic Journal of Linear Algebra

Sequences of matrices with increasing size naturally arise in several areas of science, such as, for example, the numerical discretization of differential and integral equations. An approximation theory for sequences of this kind has recently been developed, with the aim of providing tools for computing their asymptotic singular value and eigenvalue distributions. The cornerstone of this theory is the notion of approximating classes of sequences (a.c.s.), which is also fundamental to the theory of generalized locally Toeplitz (GLT) sequences, and hence to the spectral analysis of PDE discretization matrices. Drawing inspiration from measure theory, here it is introduced ...


The General $\Phi$-Hermitian Solution To Mixed Pairs Of Quaternion Matrix Sylvester Equations, Zhuo-Heng He, Jianzhen Liu, Tin-Yau Tam Dec 2017

The General $\Phi$-Hermitian Solution To Mixed Pairs Of Quaternion Matrix Sylvester Equations, Zhuo-Heng He, Jianzhen Liu, Tin-Yau Tam

Electronic Journal of Linear Algebra

Let $\mathbb{H}^{m\times n}$ be the space of $m\times n$ matrices over $\mathbb{H}$, where $\mathbb{H}$ is the real quaternion algebra. Let $A_{\phi}$ be the $n\times m$ matrix obtained by applying $\phi$ entrywise to the transposed matrix $A^{T}$, where $A\in\mathbb{H}^{m\times n}$ and $\phi$ is a nonstandard involution of $\mathbb{H}$. In this paper, some properties of the Moore-Penrose inverse of the quaternion matrix $A_{\phi}$ are given. Two systems of mixed pairs of quaternion matrix Sylvester equations $A_{1}X-YB_{1}=C_{1},~A_{2}Z-YB_{2}=C_ ...


Gaze-Contingent Displays For Interactive Text Enhancement, Divya Bajaj Dec 2017

Gaze-Contingent Displays For Interactive Text Enhancement, Divya Bajaj

Graduate Masters Theses

Eye trackers are used for measuring a person’s eye movements, for example, while reading text on a screen. This information can be used by scientists to study the human visual system during object recognition or text comprehension. Moreover, engineers can build gaze-controlled interfaces that trigger a variety of actions when the user looks at pre-specified icons on a screen. In my research, I studied how gaze-contingent displays can be used to enhance the information that is provided by texts. First, I implemented a simple scripting language that allows even users without programming experience to set up gaze-contingent text displays ...


Looping Predictive Method To Improve Accuracy Of A Machine Learning Model, Subramanyam Reddy Pogili Dec 2017

Looping Predictive Method To Improve Accuracy Of A Machine Learning Model, Subramanyam Reddy Pogili

Theses

The topic of this project is an analysis of drug-related tweets. The goal is to build a Machine Learning Model that can distinguish between tweets that indicate drug abuse and other tweets that also contain the name of a drug but do not descri


Electrical Properties Of Metal Semiconductor Contacts - Metals On Mos2: A Case Study, Xiao Chang Dec 2017

Electrical Properties Of Metal Semiconductor Contacts - Metals On Mos2: A Case Study, Xiao Chang

Theses

Properties of monolayer semiconductor, MoS2, are presented in the research. Schottky barrier height and Schottky-Mott rules are discussed. The current-voltage measurement and capacitance-voltage measurement are analyzed considering the role of the work


Characteristics Of Different Deep Neural Networks And Application Of Pre-Trained Model Without Transfer Learning, Zhiqi Peng Dec 2017

Characteristics Of Different Deep Neural Networks And Application Of Pre-Trained Model Without Transfer Learning, Zhiqi Peng

Theses

Deep neural networks have been successful in many areas, some of them even surpass human performances. The goal of this thesis is using data simulations to present different characteristics of three deep neural networks: fully connected deep neural net


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Semantic Hierarchies For Extracting, Modeling, And Connecting Compliance Requirements In Information Security Control Standards, Matthew L. Hale, Rose F. Gamble Dec 2017

Semantic Hierarchies For Extracting, Modeling, And Connecting Compliance Requirements In Information Security Control Standards, Matthew L. Hale, Rose F. Gamble

Interdisciplinary Informatics Faculty Publications

Companies and government organizations are increasingly compelled, if not required by law, to ensure that their information systems will comply with various federal and industry regulatory standards, such as the NIST Special Publication on Security Controls for Federal Information Systems (NIST SP-800-53), or the Common Criteria (ISO 15408-2). Such organizations operate business or mission critical systems where a lack of or lapse in security protections translates to serious confidentiality, integrity, and availability risks that, if exploited, could result in information disclosure, loss of money, or, at worst, loss of life. To mitigate these risks and ensure that their information systems ...


Simulations For Designing And Interpreting Intervention Trials In Infectious Diseases., M Elizabeth Halloran, Kari Auranen, Sarah Baird, Nicole E Basta, Steven E Bellan, +Several Additional Authors Dec 2017

Simulations For Designing And Interpreting Intervention Trials In Infectious Diseases., M Elizabeth Halloran, Kari Auranen, Sarah Baird, Nicole E Basta, Steven E Bellan, +Several Additional Authors

Global Health Faculty Publications

BACKGROUND: Interventions in infectious diseases can have both direct effects on individuals who receive the intervention as well as indirect effects in the population. In addition, intervention combinations can have complex interactions at the population level, which are often difficult to adequately assess with standard study designs and analytical methods.

DISCUSSION: Herein, we urge the adoption of a new paradigm for the design and interpretation of intervention trials in infectious diseases, particularly with regard to emerging infectious diseases, one that more accurately reflects the dynamics of the transmission process. In an increasingly complex world, simulations can explicitly represent transmission dynamics ...


"The Devil Is In The Details:" Inland Northwest Stakeholders’ Views On Three Forest-Based Bioenergy Scenarios, Soren Newman, Darin Saul, Robert Keefe, Ryan Jacobson, Tamara Laninga, Jillian Moroney Dec 2017

"The Devil Is In The Details:" Inland Northwest Stakeholders’ Views On Three Forest-Based Bioenergy Scenarios, Soren Newman, Darin Saul, Robert Keefe, Ryan Jacobson, Tamara Laninga, Jillian Moroney

University Author Recognition Bibliography: 2017

Public and private initiatives are actively exploring a range of forest-based bioenergy development options in the Inland Northwest of the United States. These efforts are motivated in part by the potential to generate renewable energy while creating a market for forest residues that would facilitate hazardous fuels reduction and provide economic opportunities. Understanding stakeholders’ perspectives is critical to the feasibility and long-term viability of bioenergy projects. This study presents stakeholder perspectives on forest-based bioenergy development strategies for communities in the forested areas of Idaho, western Montana, eastern Washington, and eastern Oregon. We developed three scenarios based on bioenergy initiatives currently ...


Measurement Of The Helicity Asymmetry E In ΩΠ+ΠΠ0 Photoproduction, Z. Akbar, P. Roy, S. Park, V. Crede, A. V. Anisovich, I. Denisenko, E. Klempt, V. A. Nikonov, A. V. Sarantsev, K. P. Adhikari, S. Adhikari, M. J. Amaryan, S. Anefalos Pereira, H. Avakian, J. Ball, M. Battaglieri, V. Batourine, I. Bedlinskiy, S. Boiarinov, W. J. Briscoe, J. Brock, W. K. Brooks, V. D. Burkert, F. T. Cao, C. Carlin, D. S. Carman, A. Celentano, G. Charles, T. Chetry, G. Ciullo, Wesley P. Gohn Dec 2017

Measurement Of The Helicity Asymmetry E In Ω → Π+Π−Π0 Photoproduction, Z. Akbar, P. Roy, S. Park, V. Crede, A. V. Anisovich, I. Denisenko, E. Klempt, V. A. Nikonov, A. V. Sarantsev, K. P. Adhikari, S. Adhikari, M. J. Amaryan, S. Anefalos Pereira, H. Avakian, J. Ball, M. Battaglieri, V. Batourine, I. Bedlinskiy, S. Boiarinov, W. J. Briscoe, J. Brock, W. K. Brooks, V. D. Burkert, F. T. Cao, C. Carlin, D. S. Carman, A. Celentano, G. Charles, T. Chetry, G. Ciullo, Wesley P. Gohn

Physics and Astronomy Faculty Publications

The double-polarization observable E was studied for the reaction γp using the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B at the Thomas Jefferson National Accelerator Facility and the longitudinally polarized frozen-spin target (FROST). The observable was measured from the charged decay mode of the meson, ωπ+ππ0, using a circularly polarized tagged-photon beam with energies ranging from the ω threshold at 1.1 to 2.3 GeV. A partial-wave analysis within the Bonn-Gatchina framework found dominant contributions from the 3/2+ partial wave near threshold, which is identified with the subthreshold N(1720)3/2 ...


Magnetocrystalline Anisotropy Of "-Fe2o3, Imran Ahamed, Rohilt Pathak, Arti Kashyap Dec 2017

Magnetocrystalline Anisotropy Of "-Fe2o3, Imran Ahamed, Rohilt Pathak, Arti Kashyap

Faculty Publications from Nebraska Center for Materials and Nanoscience

The epsilon Fe2O3 phase of iron oxide has been studied to understand the spin structure and the magnetocrystalline anisotropy in the bulk and in thin films of "-Fe2O3 and Co-doped "-Fe2O3. The preferential magnetization direction in the nanoparticles of "-Fe2O3 is along the a-axis [M. Gich et al., Chem. Mater. 18, 3889 (2006)]. Compared to the bulk band gap of 1.9 eV, the thin-film band gap is reduced to 1.3 eV in the Co-free films and to 0.7 eV in the film with partial ...


First Narrow-Band Search For Continuous Gravitational Waves From Known Pulsars In Advanced Detector Data, B. P. Abbott, K. Aultoneal, S. Gaudio, K. Gill, E. M. Gretarsson, B. Hughey, M. Muratore, J. W. W. Pratt, S. G. Schwalbe, K. Staats, M. J. Szczepańczyk, M. Zanolin, Et Al. Dec 2017

First Narrow-Band Search For Continuous Gravitational Waves From Known Pulsars In Advanced Detector Data, B. P. Abbott, K. Aultoneal, S. Gaudio, K. Gill, E. M. Gretarsson, B. Hughey, M. Muratore, J. W. W. Pratt, S. G. Schwalbe, K. Staats, M. J. Szczepańczyk, M. Zanolin, Et Al.

Publications

Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signal-to-noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars ...


Black Hole Hyperaccretion Inflow-Outflow Model. I. Long And Ultra-Long Gamma-Ray Bursts, Tong Liu, Cui-Ying Song, Bing Zhang, Wei-Min Gu, Alexander Heger Dec 2017

Black Hole Hyperaccretion Inflow-Outflow Model. I. Long And Ultra-Long Gamma-Ray Bursts, Tong Liu, Cui-Ying Song, Bing Zhang, Wei-Min Gu, Alexander Heger

Physics & Astronomy Faculty Publications

Long-duration gamma-ray bursts (LGRBs) and ultra-LGRBs (ULGRBs) originate from collapsars, in the center of which a newborn rotating stellar-mass black hole (BH) surrounded by a massive accretion disk may form. In the scenario of the BH hyperaccretion inflow-outflow model and Blandford-Znajek (BZ) mechanism to trigger gamma-ray bursts (GRBs), the real accretion rate to power a BZ jet is far lower than the mass supply rate from the progenitor star. The characteristics of the progenitor stars can be constrained by GRB luminosity observations, and the results exceed usual expectations. LGRBs lasting from several seconds to tens of seconds in the rest ...


Lights Out! On Cartesian Products, Travis Peters, John Goldwasser, Michael Young Dec 2017

Lights Out! On Cartesian Products, Travis Peters, John Goldwasser, Michael Young

Electronic Journal of Linear Algebra

The game LIGHTS OUT! is played on a 5 by 5 square grid of buttons; each button may be on or off. Pressing a button changes the on/o state of the light of the button pressed and of all its vertical and horizontal neighbors. Given an initial configuration of buttons that are on, the object of the game is to turn all the lights out. The game can be generalized to arbitrary graphs. In this paper, Cartesian Product graphs (that is, graphs of the form G\box H, where G and H are arbitrary finite, simple graphs) are investigated ...


Learning About Modeling In Teacher Preparation Programs, Hyunyi Jung, Eryn Stehr, Jia He, Sharon L. Senk Dec 2017

Learning About Modeling In Teacher Preparation Programs, Hyunyi Jung, Eryn Stehr, Jia He, Sharon L. Senk

Hyunyi Jung

This study explores opportunities that secondary mathematics teacher preparation programs provide to learn about modeling in algebra. Forty-eight course instructors and ten focus groups at five universities were interviewed to answer questions related to modeling. With the analysis of the interview transcripts and related course materials, we found few opportunities for PSTs to engage with the full modeling cycle. Examples of opportunities to learn about algebraic modeling and the participants’ perspectives on the opportunities can contribute to the study of modeling and algebra in teacher education.


Supporting Preservice Teachers’ Use Of Connections And Technology In Algebra Teaching And Learning, Eryn Stehr, Hyunyi Jung, Jill Newton, Sharon L. Senk Dec 2017

Supporting Preservice Teachers’ Use Of Connections And Technology In Algebra Teaching And Learning, Eryn Stehr, Hyunyi Jung, Jill Newton, Sharon L. Senk

Hyunyi Jung

Secondary mathematics teacher education programs across the United States opportunities for preservice teachers to make connections and encounter technology to varying degrees, despite recommendations from the Conference Board of the Mathematical Sciences. We explore the research question: What opportunities do secondary mathematics teacher preparation programs provide for preservice teachers to learn about connections and to encounter technologies in learning algebra and learning to teach algebra? We present patterns and examples of a wide range of opportunities that instructors provided related to algebraic connections and use of technology, based on data collected from five teacher education programs across the U.S.


Models And Modeling, Corey Brady, Hyunyi Jung, Cheryl Eames Dec 2017

Models And Modeling, Corey Brady, Hyunyi Jung, Cheryl Eames

Hyunyi Jung

Modeling has recently received much attention as the Common Core State Standards have included it as one of eight core mathematical practices. The Models and Modeling Working Group builds on a long history of collaboration among researchers studying models and modeling. This year’s session will focus on building capacity within the broad community of researchers who are interested in theoretical and practical perspectives related to models and modeling. We will begin by engaging with a modeling activity and some closely related materials. This experience will serve to ground our discussions and provide a concrete common reference for participants. We ...


Mathematical Knowledge For Teachers: Opportunities To Learn To Teach Algebra In Teacher Education Programs, Eryn Stehr, Jeffrey Craig, Hyunyi Jung, Leonardo Medel, Alexia Mintos, Jill Newton Dec 2017

Mathematical Knowledge For Teachers: Opportunities To Learn To Teach Algebra In Teacher Education Programs, Eryn Stehr, Jeffrey Craig, Hyunyi Jung, Leonardo Medel, Alexia Mintos, Jill Newton

Hyunyi Jung

Preparing to Teach Algebra (PTA) Project gathered data about opportunities to learn to teach algebra provided by secondary teacher education programs. In sharing our findings, we use structures from the Mathematical Knowledge for Teaching (MKT) framework (Ball & Bass, 2003). The MKT framework is one way of situating the ways in which teacher education programs support preservice mathematics teachers in developing necessary knowledge types for teaching algebra. Using the MKT framework as an analytical framework is not straightforward, however. The framework must be interpreted and individualized to the study of algebra and to the opportunities to learn to teach algebra that ...


Mathematical Modeling Problems: What Affects Teaching Assistants’ Ability To Provide Feedback?, Hyunyi Jung, Alena Moon, Kelsey Joy Rodgers, Farshid Marbouti, Heidi A. Diefes-Dux Dec 2017

Mathematical Modeling Problems: What Affects Teaching Assistants’ Ability To Provide Feedback?, Hyunyi Jung, Alena Moon, Kelsey Joy Rodgers, Farshid Marbouti, Heidi A. Diefes-Dux

Hyunyi Jung

This paper describes opportunities and challenges teaching assistants (TAs) experience when they provide feedback on mathematical modeling problems. Eight TAs were interviewed regarding issues they experience while working for engineering courses in which about 2000 undergraduates create mathematical models to solve realistic problems and communicate their solutions. The opportunities and challenges are associated with the following factors: the process of providing feedback; TAs’ perspectives of modeling problems; and professional training to learn how to provide effective feedback on students’ solutions to mathematical modeling problems. The specific factors that influence TA’s abilities to provide formative feedback are discussed and the ...


Pedagogical Knowledge For Algebra On The Runway: Turning Research From The Icme-12 Into Practice, Hyunyi Jung Dec 2017

Pedagogical Knowledge For Algebra On The Runway: Turning Research From The Icme-12 Into Practice, Hyunyi Jung

Hyunyi Jung

This study addresses comparable concerns regarding pedagogical content knowledge (PCK) from different countries, experiences of teachers around the world regarding knowledge for teaching algebra, and the use of such experiences for teaching pre-service teachers. Proceedings from the most recent International Congress on Mathematical Education were analyzed focusing on the importance of PCK and specialized knowledge for teaching algebra. Analysis of multiple international studies provided a holistic approach to bridge research into practice. In this paper, I present the findings of this analysis which were subsequently used to develop contents for teaching algebra in a methods course for pre-service secondary mathematics ...


Developing Frameworks For Preparation Of Algebra Teachers: Challenges And Opportunities, Sharon L. Senk, Jill Newton, Jia He, Hyunyi Jung, Eryn Stehr, Alexia Mintos Dec 2017

Developing Frameworks For Preparation Of Algebra Teachers: Challenges And Opportunities, Sharon L. Senk, Jill Newton, Jia He, Hyunyi Jung, Eryn Stehr, Alexia Mintos

Hyunyi Jung

Algebra has long been considered the foundation for higher-level mathematics and a gatekeeper for postsecondary opportunities. In recent decades, increasing enrollments in algebra have placed additional demands on algebra teachers for reaching a more diverse population of students. With the 2010 release and adoption of the Common Core State Standards for Mathematics (CCSSM) by all but a few states, questions arise regarding preparing teachers to teach the standards and practices described in CCSSM. In this paper, we describe the processes used to develop frameworks to study opportunities provided by secondary teacher preparation programs to learn about algebra, algebra teaching, achieving ...


Factors That Help And Hinder Teaching Assistants’ Ability To Execute Their Responsibilities, Farshid Marbouti, Kelsey Joy Rodgers, Hyunyi Jung, Alena Moon, Heidi A. Diefes-Dux Dec 2017

Factors That Help And Hinder Teaching Assistants’ Ability To Execute Their Responsibilities, Farshid Marbouti, Kelsey Joy Rodgers, Hyunyi Jung, Alena Moon, Heidi A. Diefes-Dux

Hyunyi Jung

Graduate and undergraduate teaching assistants (TAs) are key players in large universities’ efforts to incorporate student-centered learning into science, technology, engineering, and mathematics (STEM) courses. This paper investigates, through interviews, the perspectives of eight TAs employed within a First-Year Engineering course with a significant focus on open-ended problem solving. The purpose of this study was to identify factors that helped and hindered teaching assistants’ execution of their responsibilities which included grading and helping students. Engaging TAs in the open-ended problems prior to implementing them in class, face-to-face discussions, and face-to-face lectures were helpful components of training, and training overall was ...


Characteristics Of Feedback That Influence Student Confidence And Performance During Mathematical Modeling, Hyunyi Jung, Heidi A. Diefes-Dux, Aladar K. Horvath, Kelsey Joy Rodgers, Monica E. Cardella Dec 2017

Characteristics Of Feedback That Influence Student Confidence And Performance During Mathematical Modeling, Hyunyi Jung, Heidi A. Diefes-Dux, Aladar K. Horvath, Kelsey Joy Rodgers, Monica E. Cardella

Hyunyi Jung

This study focuses on characteristics of written feedback that influence students’ performance and confidence in addressing the mathematical complexity embedded in a Model-Eliciting Activity (MEA). MEAs are authentic mathematical modeling problems that facilitate students’ iterative development of solutions in a realistic context. We analyzed 132 first-year engineering students’ confidence levels and mathematical model scores on aMEA(pre and post feedback), along with teaching assistant feedback given to the students. The findings show several examples of affective and cognitive feedback that students reported that they used to revise their models. Students’ performance and confidence in developing mathematical models can be increased ...


Evaluation Of The Community Multiscale Air Quality Model For Simulating Winter Ozone Formation In The Uinta Basin, Rebecca Matichuk, Gail Tonnesen, Deborah Luecken, Rob Gillam, Sergey L. Napelenok, Kirk R. Baker, Donna Schwede, Ben Murphy, Detlev Helmig, Seth N. Lyman, Shawn Roselle Dec 2017

Evaluation Of The Community Multiscale Air Quality Model For Simulating Winter Ozone Formation In The Uinta Basin, Rebecca Matichuk, Gail Tonnesen, Deborah Luecken, Rob Gillam, Sergey L. Napelenok, Kirk R. Baker, Donna Schwede, Ben Murphy, Detlev Helmig, Seth N. Lyman, Shawn Roselle

Bingham Energy Research Center

The Weather Research and Forecasting (WRF) and Community Multiscale Air Quality (CMAQ) models were used to simulate a 10 day high-ozone episode observed during the 2013 Uinta Basin Winter Ozone Study (UBWOS). The baseline model had a large negative bias when compared to ozone (O3) and volatile organic compound (VOC) measurements across the basin. Contrary to other wintertime Uinta Basin studies, predicted nitrogen oxides (NOx) were typically low compared to measurements. Increases to oil and gas VOC emissions resulted in O3 predictions closer to observations, and nighttime O3 improved when reducing the deposition velocity for all ...


Emergent Ising Degrees Of Freedom Above A Double-Stripe Magnetic Ground State, Guanghua Zhang, Rebecca Flint Dec 2017

Emergent Ising Degrees Of Freedom Above A Double-Stripe Magnetic Ground State, Guanghua Zhang, Rebecca Flint

Ames Laboratory Accepted Manuscripts

Double-stripe magnetism [ Q = ( π / 2 , π / 2 ) ] has been proposed as the magnetic ground state for both the iron-telluride and BaTi 2 Sb 2 O families of superconductors. Double-stripe order is captured within a J 1 − J 2 − J 3 Heisenberg model in the regime J 3 ≫ J 2 ≫ J 1 . Intriguingly, besides breaking spin-rotational symmetry, the ground-state manifold has three additional Ising degrees of freedom associated with bond ordering. Via their coupling to the lattice, they give rise to an orthorhombic distortion and to two nonuniform lattice distortions with wave vector ( π , π ) . Because the ground state is fourfold ...


Texture Development And Coercivity Enhancement In Cast Alnico 9 Magnets, Wenyong Zhang, Shah Valloppilly, Xingzhong Li, Lanping Yue, Ralph Skomski, Iver Anderson, Matthew Kramer, Wei Tang, Jeff Shield, David J. Sellmyer Dec 2017

Texture Development And Coercivity Enhancement In Cast Alnico 9 Magnets, Wenyong Zhang, Shah Valloppilly, Xingzhong Li, Lanping Yue, Ralph Skomski, Iver Anderson, Matthew Kramer, Wei Tang, Jeff Shield, David J. Sellmyer

Faculty Publications from Nebraska Center for Materials and Nanoscience

The effect of Y addition and magnetic field on texture and magnetic properties of arc-melted alnico 9 magnets has been investigated. Small additions of Y (1.5 wt.%) develop a (200) texture for the arc-melted alnico 9 magnet. Such a texture is hard to form in cast samples. To achieve this goal, we set up a high-field annealing system with a maximum operation temperature of 12500 C. This system enabled annealing in a field of 45 kOe with subsequent draw annealing for the solutionized buttons; we have been able to substantially increase remanence ratio and coercivity, from 0.70 ...


Influence Of Classical Anisotropy Fields On The Properties Of Heisenberg Antiferromagnets Within Unified Molecular Field Theory, David C. Johnston Dec 2017

Influence Of Classical Anisotropy Fields On The Properties Of Heisenberg Antiferromagnets Within Unified Molecular Field Theory, David C. Johnston

Ames Laboratory Accepted Manuscripts

A comprehensive study of the influence of classical anisotropy fields on the magnetic properties of Heisenberg antiferromagnets within unified molecular field theory versus temperature T , magnetic field H , and anisotropy field parameter h A 1 is presented for systems comprised of identical crystallographically-equivalent local moments. The anisotropy field for collinear z -axis antiferromagnetic (AFM) ordering is constructed so that it is aligned in the direction of each ordered and/or field-induced thermal-average moment with a magnitude proportional to the moment, whereas that for XY anisotropy is defined to be in the direction of the projection of the moment onto the ...