Physical Sciences and Mathematics Commons^™

Test Cases Selection Based On Source Code Features Extraction, I. Alazzam, Izzat M. Alsmadi, M. Akour

Computer Science Faculty Publications (Archived)

Extracting valuable information from source code automatically was the subject of many research papers. Such information can be used for document traceability, concept or feature extraction, etc. In this paper, we used an Information Retrieval (IR) technique: Latent Semantic Indexing (LSI) for the automatic extraction of source code concepts for the purpose of test cases' reduction. We used and updated the open source FLAT Eclipse add on to try several code stemming approaches. The goal is to check the best approach to extract code concepts that can improve the process of test cases' selection or reduction.

Large Scale Anisotropy Of Cosmic Rays And Directional Neutrino Signals From Galactic Sources, Luis A. Anchordoqui, Haim Goldberg, Angela V. Olinto, Thomas C. Paul, Brian J. Vlcek, Thomas J. Weiler

Publications and Research

We investigate the neutrino cosmic ray connection for sources in the Galaxy in terms of two observables: the shape of the energy spectrum and the distribution of arrival directions. We also study the associated gamma ray emission from these sources.

Research Needs In The Colorado River Basin: A Summary Of Policy-Related Topics To Explore Further In Support Of Solution-Oriented Decision-Making, Colorado River Governance Initiative, University Of Colorado Boulder. Getches-Wilkinson Center For Natural Resources, Energy, And The Environment Western Water Policy Program

Books, Reports, and Studies

14 p. ; 28 cm

Restoring Sacred Waters: A Guide To Protecting Tribal Non-Consumptive Water Uses In The Colorado River Basin, Julie Nania, Julia Guarino, University Of Colorado Boulder. Getches-Wilkinson Center For Natural Resources, Energy, And The Environment

Books, Reports, and Studies

105 p. : color illustrations ; 28 cm

Introduction -- Gathering information and starting the process -- Indian federal reserved water rights -- Using Indian federal reserved water rights for instream flows -- Negotiating for non-consumptive uses in settlement agreements -- Protecting non-consumptive uses in tribal water codes -- Other legal tools -- Irrigating for instream flows and traditional plants -- Summary and key points

Measurement Of The Target-Normal Single-Spin Asymmetry In Deep-Inelastic Scattering From The Reaction ³He↑(E,E')X, J. Katich, X. Qian, X. Y. Zhao, M. Canan, L. El Fassi, S. Golge

Physics Faculty Publications

We report the first measurement of the target-normal single-spin asymmetry in deep-inelastic scattering from the inclusive reaction ³He↑(e, e')X on a polarized ³He gas target. Assuming time-reversal invariance, this asymmetry is strictly zero in the Born approximation but can be nonzero if two-photon-exchange contributions are included. The experiment, conducted at Jefferson Lab using a 5.89 GeV electron beam, covers a range of 1.7 < W < 2.9 GeV, 1.0 < Q² < 4.0 GeV² and 0.16 < x < 0.65. Neutron asymmetries were extracted using the effective nucleon polarization and measured proton-to-³He cross-section ratios. The measured neutron asymmetries are negative with an average value of (-1.09 ± 0.38) x 10^-2for invariant mass W > 2 GeV, which is nonzero at …

Improving The Performance Of Skeletal Mesh Animations In The Blender Game Engine, Mitchell Stokes

EWU Masters Thesis Collection

No abstract provided.

Split Strongly Abelian P-Chief Factors And First Degree Restricted Cohomology, Jorg Feldvoss, Salvatore Siciliano, Thomas Weigel

University Faculty and Staff Publications

In this paper we investigate the relation between the multiplicities of split strongly abelian p-chief factors of finite-dimensional restricted Lie algebras and first degree restricted cohomology. As an application we obtain a characterization of solvable restricted Lie algebras in terms of the multiplicities of split strongly abelian p-chief factors. Moreover, we derive some results in the representation theory of restricted Lie algebras related to the principal block and the projective cover of the trivial irreducible module of a finite-dimensional restricted Lie algebra. In particular, we obtain a characterization of finite-dimensional solvable restricted Lie algebras in terms of the second Loewy …

Three-Dimensional Periodic Graphene Nanostructures, Peter M. Wilson, Gilbert N. Mbah, Thomas G. Smith, Daniel Schmidt, Rebecca Y. Lai, Tino Hofmann, Alexander Sinitskii

Department of Chemistry: Faculty Publications

Graphene is a basic building block for many known and emerging carbon-based materials whose properties largely depend on the way how graphene is structured at the nanoscale. Synthesis of novel threedimensional (3D) nanostructures of graphene would be an important advance for fundamental research and various applications. In this paper, we discuss the possibility of fabricating complex 3D graphene nanostructures by growing graphene on pre-synthesized nanostructured metal templates by chemical vapor deposition (CVD) and then etching away the metal. In the proof-of-concept experiments, we study this idea using two types of metal nanostructures, inverse opals and slanted nanopillar arrays grown by …

Bulk Properties Of Solution-Synthesized Chevron-Like Graphene Nanoribbons, Timothy H. Vo, Mikhail Shekhirev, Alexey Lipatov, Rafal A. Korlacki, Alexander Sinitskii

Department of Chemistry: Faculty Publications

Graphene nanoribbons (GNRs) have received a great deal of attention due to their promise for electronic and optoelectronic applications. Several recent studies have focused on the synthesis of GNRs by the bottom-up approaches that could yield very narrow GNRs with atomically precise edges. One type of GNRs that has received a considerable attention is the chevron-like GNR with a very distinct periodic structure. Surface-assisted and solution-based synthetic approaches for the chevron-like GNRs have been developed, but their electronic properties have not been reported yet. In this work, we synthesized chevron-like GNRs in bulk by a solution-based method, characterized them by …

Highly Selective Gas Sensor Arrays Based On Thermally Reduced Graphene Oxide, Alexey Lipatov, Alexey Varezhnikov, Peter Wilson, Victor Sysoev, Andrei Kolmakov, Alexander Sinitskii

Department of Chemistry: Faculty Publications

The electrical properties of reduced graphene oxide (rGO) have been previously shown to be very sensitive to surface adsorbates, thus making rGO a very promising platform for highly sensitive gas sensors. However, poor selectivity of rGO-based gas sensors remains a major problem for their practical use. In this paper, we address the selectivity problem by employing an array of rGO-based integrated sensors instead of focusing on the performance of a single sensing element. Each rGO-based device in such an array has a unique sensor response due to the irregular structure of rGO films at different levels of organization, ranging from …

Active Control Of Magnetoresistance Of Organic Spin Valves Using Ferroelectricity, Dali Sun, Mei Fang, Xiaoshan Xu, Lu Jiang, Hangwen Guo, Yanmei Wang, Wenting Yang, Lifeng Yin, Paul C. Snijders, T. Z. Ward, Zheng Gai, X. -G. Zhang, Ho Nyung Lee, Jian Shen

Xiaoshan Xu Papers

Organic spintronic devices have been appealing because of the long spin lifetime of the charge carriers in the organic materials and their low cost, flexibility and chemical diversity. In previous studies, the control of resistance of organic spin valves is generally achieved by the alignment of the magnetization directions of the two ferromagnetic electrodes, generating magnetoresistance. Here we employ a new knob to tune the resistance of organic spin valves by adding a thin ferroelectric interfacial layer between the ferromagnetic electrode and the organic spacer: the magnetoresistance of the spin valve depends strongly on the history of the bias voltage, …

Adjusting Magnetic Nanostructures For High-Performance Magnetic Sensors, Xiaolu Yin, Ralph A. Skomski, David J. Sellmyer, Sy-Hwang Liou, Stephen E. Russek, Eric R. Evarts, John Moreland, A S. Edelstein, L Yuan, M L. Yan, J Shen

David Sellmyer Publications

The magnetic properties of the soft ferromagnetic layer in magnetic tunnel junctions are one of key factors to determine the performance of magnetoresistance sensors. We use a three-step orthogonal annealing procedure to modify the nanostructures of the free layer in the magnetic tunnel junction to control features such as magnetization reversal, coercivity, exchange field, and tunnel magnetoresistance ratio. We present a sensor with an improved sensitivity as high as 3944%/mT. This magnetic sensor only dissipates 200 lW of power while operating under an applied voltage of 1V.

Orthorhombic Zr2Co11 Phase Revisited, Xingzhong Li, Wenyong Zhang, David J. Sellmyer, X Zhao, M C. Nguyen, C Z. Wang, K M. Ho

David Sellmyer Publications

The structure of the orthorhombic Zr₂Co₁₁ phase was revisited in the present work. Selected-area electron diffraction (SAED) and high-resolution electron microscopy (HREM) techniques were used to investigate the structure. They show the orthorhombic Zr₂Co₁₁ phase has a 1-D incommensurate modulated structure. The structure can be approximately described as a B-centered orthorhombic lattice. The lattice parameters of the orthorhombic Zr₂Co₁₁ phase have been determined by a tilt series of SAED patterns. A hexagonal network with a modulation wave has been observed in the HREM image and the hexagonal motif is considered as …

Development And Intrinsic Properties Of Hexagonal Ferromagnetic (Zr,Ti)Fe2, Wenyong Zhang, Xingzhong Li, Shah R. Valloppilly, Ralph A. Skomski, Jeffrey E. Shield, David J. Sellmyer

David Sellmyer Publications

Nanocrystalline Ti_0.75Zr_0.25Fe_2+x (x=0-0.4) and Ti_0.75-yB_yZr_0.25Fe_2.4 (y=0-0.35) with high saturation magnetization have been fabricated by the melt-spinning technique. Nanocrystalline Ti_0.75Zr_0.25Fe_2+x consists of the hexagonal C14 Laves phase (Ti,Zr)Fe₂. Fe addition decreases the lattice parameter a and shrinks the cell volume. The antiferromagnetic Fe-Fe interactions may decrease with the increase of x, leading to a significant enhancement of saturation polarization (Js) and Curie temperature (Tc). The magnetocrystalline anisotropy constant K also increases with increasing x. Excessive Fe addition (x>0.25) may induce structural …

Effect Of Quench Rate On Nanostructure And Magnetic Properties Of Prco5, Wenyong Zhang, Ralph Skomski, Xingzhong Li, Shah R. Valloppilly, Jeffrey E. Shield, David J. Sellmyer

David Sellmyer Publications

The effect of quench rate on nanostructure and magnetic properties of PrCo₅ alloy has been investigated. The increase of quench rate through wheel speed in melt spinning suppresses the formation of the secondary Pr₂Co₁₇ and Pr₅Co₁₉ phases with low magnetocrystalline anisotropy field and refines the nanostructure. This significantly improves the coercivity, remanence, and energy product. For example, increasing the wheel speed from 30 m/s to 70 m/s increases the coercivity and energy product from 3.2 kOe and 4.0 MGOe to 10.3 kOe and 13.7 MGOe, respectively. The magnetic hardening mechanism appears to be …

Kondorski Reversal In Magnetic Nanowires, Ralph A. Skomski, Eva Schubert, Axel Enders, David J. Sellmyer

David Sellmyer Publications

Magnetization reversal in nanowire systems, such as alnico-type permanent magnets, slanted columns produced by glancing-angle deposition, and nanowires embedded in alumina templates, is investigated by model calculations. The angular dependence of the domain-wall propagation is Kondorski-like, reminiscent of Kondorski pinning in bulk materials but with a somewhat different physics and consistent with Kerr hysteresis-loop measurements. Criss-cross patterning of alnicos improves the coercivity but reduces the remanence, with virtually zero net effect on energy product. Finally, we briefly discuss the wire-radius dependence of the coercivity in the context of "shape anisotropy" and the occurrence of interaction domains in alnico.

Phase Composition And Nanostructure Of Zr2Co11-Based Alloys, Y.L. Jin, Wenyong Zhang, Ralph A. Skomski, Shah R. Valloppilly, Jeffrey E. Shield, David J. Sellmyer

David Sellmyer Publications

The effect of Mo addition on phase composition and nanostructure of nanocrystalline Zr₁₆Co_84-xMo_x (x=0–2.0) melt spun at 55 m/s has been investigated. All the ribbons consist mainly of a hard magnetic Zr₂Co₁₁ phase with rhombohedral crystal structure but also contain minor amounts of soft-magnetic phases. The increase in cell volume on alloying suggests that Mo mainly enters the rhombohedral Zr₂Co₁₁ structure and occupies the Co site. Mo addition promotes the formation of the hard magnetic phase and increases its volume fraction. The mean grain size of the hard magnetic …

Structural, Magnetic, And Electron Transport Properties Of Mn3-XPtXSn (X = 0, 0.5, 1) Nanomaterials, A Nelson, Yung Huh, Parashu Kharel, Shah R. Valloppilly, Ralph A. Skomski, David J. Sellmyer

David Sellmyer Publications

The structural, magnetic, and electron-transport properties of Mn_3-xPt_xSn (x=0, 0.5, 1) nanomaterials prepared by arc-melting, melt-spinning, and annealing were investigated. It was found that the hexagonal structure is the most stable structure for Mn³Sn and the samples show an antiferromagnetic spin order at room temperature. The Pt-containing samples are mainly tetragonal but contain a small amount of other impurity phases, including hexagonal Mn³Sn and Mn₂Sn. At room temperature, the Pt-containing samples show ferri- or ferromagnetic spin order with a Curie temperature of about 370 K. The measured high-field magnetization and …

Exploring The Structural Complexity Of Intermetallic Compounds By An Adaptive Genetic Algorithm, X Zhao, M C. Nguyen, Wenyong Zhang, C Z. Wang, Matthew J. Kramer, David J. Sellmyer, Xingzhong Li, F Zhang, Liqin Ke, Vladimir P. Antropov, K M. Ho

David Sellmyer Publications

Solving the crystal structures of novel phases with nanoscale dimensions resulting from rapid quenching is difficult due to disorder and competing polymorphic phases. Advances in computer speed and algorithm sophistication have now made it feasible to predict the crystal structure of an unknown phase without any assumptions on the Bravais lattice type, atom basis, or unit cell dimensions, providing a novel approach to aid experiments in exploring complex materials with nanoscale grains. This approach is demonstrated by solving a long-standing puzzle in the complex crystal structures of the orthorhombic, rhombohedral, and hexagonal polymorphs close to the Zr₂Co_{11 …}

Magnetic Nanostructuring And Overcoming Brown’S Paradox To Realize Extraordinary High-Temperature Energy Products, Balamurugan Balasubramanian, Pinaki Mukherjee, Ralph A. Skomski, Priyanka Manchanda, Bhaskar Das, David J. Sellmyer

David Sellmyer Publications

Nanoscience has been one of the outstanding driving forces in technology recently, arguably more so in magnetism than in any other branch of science and technology. Due to nanoscale bit size, a single computer hard disk is now able to store the text of 3,000,000 average-size books, and today’s high-performance permanent magnets—found in hybrid cars, wind turbines, and disk drives—are nanostructured to a large degree. The nanostructures ideally are designed from Co- and Fe-rich building blocks without critical rare-earth elements, and often are required to exhibit high coercivity and magnetization at elevated temperatures of typically up to 180 °C for …

Size-Induced Chemical And Magnetic Ordering In Individual Fe–Au Nanoparticles, Pinaki Mukherjee, Priyanka Manchanda, Pankaj Kumar, Lin Zhou, Matthew J. Kramer, Arti Kashyap, Ralph Skomski, David J. Sellmyer, Jeffrey E. Shield

David Sellmyer Publications

Formation of chemically ordered compounds of Fe and Au is inhibited in bulk materials due to their limited mutual solubility. However, here we report the formation of chemically ordered L12-type Fe₃Au and FeAu₃ compounds in Fe–Au sub-10 nm nanoparticles, suggesting that they are equilib-rium structures in size-constrained systems. The stability of these L12-ordered Fe₃Au and FeAu₃ com-pounds along with a previously discovered L10-ordered FeAu has been explained by a size-dependent equilibrium thermodynamic model. Furthermore, the spin ordering of these three com-pounds has been computed using ab initio first-principle calculations. All ordered compounds exhibit a …

Direct Chemical Synthesis Of L10-Feptau Nanoparticles With High Coercivity, Yongsheng Yu, Pinaki Mukherjee, Yuan Tian, Xingzhong Li, David J. Sellmyer

David Sellmyer Publications

We report a facile synthesis of hard magnetic L1₀-FePtAu nanoparticles by coreduction of Fe(acac)₃, Pt(acac)₂ (acac = acetylacetonate), and gold acetate in oleylamine. In the current reaction condition, NP sizes are controlled to be 5.5 to 11.0 nm by changing the amount of Au doping. When the Au composition in the NPs is higher than 14%, the hard magnetic NPs are directly obtained without any annealing. The highest coercivity of 12.15 kOe at room temperature could be achieved for the NPs with 32% Au doping, which is much higher than the coercivities reported by the …

Positive Exchange Bias In Epitaxial Permalloy/Mgo Integrated With Si (100), S. S. Rao, J. T. Prater, Fan Wu, S. Nori, D. Kumar, Lanping Yue, Sy_Hwang Liou, Jagdish Narayan

Sy-Hwang Liou Publications

In magnetic random access memory (MRAM) devices, soft magnetic thin film elements such as permalloy (Py) are used as unit cells of information. The epitaxial integration of these elements with the technologically important substrate Si (100) and a thorough understanding of their magnetic properties are critical for CMOS-based magnetic devices. We report on the epitaxial growth of Ni_82.5Fe_17.5 (permalloy, Py) on Si (100) using a TiN/MgO buffer layer. Initial stages of growth are characterized by the formation of discrete islands that gradually merge into a continuous film as deposition times are extended. Interestingly, we find that the …

Systematic Government Access To Private-Sector Data Redux, Fred H. Cate, Christopher Kuner, Christopher Millard, Dan Jerker B. Svantesson

Articles by Maurer Faculty

No abstract provided.

Taking Stock After Four Years, Fred H. Cate, Christopher Kuner, Christopher Millard, Dan Jerker B. Svantesson

Articles by Maurer Faculty

No abstract provided.

Skyrmionic Spin Seebeck Effect Via Dissipative Thermomagnonic Torques, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

We derive thermomagnonic torque and its “β-type” dissipative correction from the stochastic Landau-Lifshitz-Gilbert equation. The β-type dissipative correction describes viscous coupling between magnetic dynamics and magnonic current and it stems from spin mistracking of the magnetic order. We show that thermomagnonic torque is important for describing temperature gradient induced motion of skyrmions in helical magnets while dissipative correction plays an essential role in generating transverse Magnus force. We propose to detect such skyrmionic motion by employing the transverse spin Seebeck effect geometry.

Parafermion Stabilizer Codes, Utkan Güngördü, Rabindra Nepal, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

We define and study parafermion stabilizer codes, which can be viewed as generalizations of Kitaev’s onedimensional (1D) model of unpaired Majorana fermions. Parafermion stabilizer codes can protect against lowweight errors acting on a small subset of parafermion modes in analogy to qudit stabilizer codes. Examples of several smallest parafermion stabilizer codes are given. A locality-preserving embedding of qudit operators into parafermion operators is established that allows one to map known qudit stabilizer codes to parafermion codes. We also present a local 2D parafermion construction that combines topological protection of Kitaev’s toric code with additional protection relying on parity conservation.

Demonstrating Entanglement By Testing Bell's Theorem In Majorana Wires, David E. Drummond, Alexey Kovalev, Chang-Yu Hou, Kirill Shtengel, Leonid P. Pryadko

Department of Physics and Astronomy: Faculty Publications

We propose an experiment that would establish the entanglement of Majorana zero modes in semiconductor nanowires by testing the Bell and Clauser-Horne-Shimony-Holt inequalities. Our proposal is viable with realistic system parameters, simple “keyboard” gating, and projective measurement. Theoretical models and simulation results indicate entanglement can be demonstrated with moderately accurate gate operations. In addition to providing further evidence for the existence of the Majorana bound states, our proposal could be used as an experimental stepping stone to more complicated braiding experiments.

Numerical Techniques For Finding The Distances Of Quantum Codes, Ilya Dumer, Alexey Kovalev, Leonid P. Pryadko

Department of Physics and Astronomy: Faculty Publications

We survey the existing techniques for calculating code distances of classical codes and apply these techniques to generic quantum codes. For classical and quantum LDPC codes, we also present a new linked-cluster technique. It reduces complexity exponent of all existing deterministic techniques designed for codes with small relative distances (which include all known families of quantum LDPC codes), and also surpasses the probabilistic technique for sufficiently high code rates.

Wavefront-Correction For Nearly Diffraction Limited Focusing Of Dual-Color Laser Beams To High Intensities, Baozhen Zhao, Jun Zhang, Shouyuan Chen, Cheng Liu, Grigory V. Golovin, Sudeep Banerjee, Kevin J. Brown, Jared Mills, Chad Petersen, Donald Umstadter

Donald Umstadter Publications

We demonstrate wavefront correction of terawatt-peak-power laser beams at two distinct and well-separated wavelengths. Simultaneous near diffraction-limited focusability is achieved for both the fundamental (800 nm) and second harmonic (400 nm) of Ti:sapphire-amplified laser light. By comparing the relative effectiveness of various correction loops, the optimal ones are found. Simultaneous correction of both beams of different color relies on the linear proportionality between their wavefront aberrations. This method can enable two-color experiments at relativistic intensities.