Digital Commons Network^™

Assembly Of Uniaxially Aligned Rare-Earth-Free Nanomagnets, Balamurugan Balamurugan, Bhaskar Das, Shah R. Valloppilly, Ralph Skomski, Xingzhong Li, David J. Sellmyer

David Sellmyer Publications

We report HfCo₇ nanoparticles with appreciable permanent-magnet properties (magnetocrystalline anisotropy K₁≈10 Mergs/cm³, coercivity H_c ≈ 4.4 kOe, and magnetic polarization J_s≈10.9 kG at 300 K) deposited by a single-step cluster-deposition method. The direct crystalline-ordering of nanoparticles during the gas-aggregation process, without the requirement of a high-temperature thermal annealing, provides an unique opportunity to align their easy axes uniaxially by applying a magnetic field of about 5 kOe prior to deposition, and subsequently to fabricate exchange-coupled nanocomposites having J_s as high as 16.6 kG by co-depositing soft magnetic Fe-Co. This study suggests …

Writing For The Web: Twitter As A Starting Point For Breaking News, Sue Burzynski Bullard, Michelle Carr Hassler

College of Journalism and Mass Communications: Faculty Publications

Students enrolled in a multimedia reporting course use Twitter to cover breaking news events as they unfold, capitalizing on the immediacy of the social media network and the Web. Using cellphones or laptops, they learn to tell stories 140 characters at a time. The second half of this assignment requires students to build on their Twitter stories by posting follow-up stories and photographs to a class website. The follow- ups, written within six hours of events, must include additional reporting. The assignment marries traditional writing and reporting skills with digital tools increasingly being used in the real world.

Thermal Quench Effects On Ferroelectric Domain Walls, P. Paruch, A. B. Kolton, X. Hong, C. H. Ahn, T. Giamarchi

Xia Hong Publications

Using piezoresponse force microscopy on epitaxial ferroelectric thin films, we have measured the evolution of domain wall roughening as a result of heat-quench cycles up to 735 ◦C, with the effective roughness exponent ζ changing from 0.25 to 0.5. We discuss two possible mechanisms for the observed ζ increase: a quench from a thermal one-dimensional configuration and from a locally equilibrated pinned configuration with a crossover from a two- to one-dimensional regime. We find that the postquench spatial structure of the metastable states, qualitatively consistent with the existence of a growing dynamical length scale whose ultraslow evolution is primarily controlled …

Electric Modulation Of Magnetization At The Batio3/La0.67sr0.33mno3 Interfaces, H. Lu, Thomas A. George, Yong Wang, Ihor Ketsman, John D. Burton, C.-W. Bark, Sangjin Ryu, Dong Jik Kim, J. Wang, Christian Binek, Peter A. Dowben, Andrei Sokolov, C. B. Eom, Evgeny Y. Tsymbal, Alexei Gruverman

Alexei Gruverman Publications

We report large (>10%) magnetization modulation by ferroelectric polarization reversal in the ferroelectric-ferromagnetic BaTiO₃/La_0.67Sr_0.33MnO₃ (BTO/LSMO) heterostructures. We find that the electrically induced change in magnetization is limited to the BTO/LSMO interface but extends about 3 nm deep into the LSMO layer—far beyond the expected screening length of metallic LSMO. It is suggested that this effect is due to a metal-insulator transition occurring at the BTO/LSMO interface as a result of electrostatic doping.

Tunnel Electroresistance In Junctions With Ultrathin Ferroelectric Pb(Zr0.2ti0.8)O3 Barriers, Daniel Pantel, Haidong Lu, Silvana Goetze, Peter Werner, Dong Jik Kim, Alexei Gruverman, Dietrich Hesse, Marin Alexe

Alexei Gruverman Publications

In ferroelectric tunnel junctions, the ferroelectric polarization state of the barrier influences the quantum-mechanical tunneling through the junction, resulting in tunnel electroresistance (TER). Here, we investigate tunnel electroresistance in Co/PbZr_0.2Ti_0.8O₃/La_0.7Sr_0.3MnO₃ tunnel junctions. The ferroelectric polarization in tunnel junctions with 1.2-1.6 nm (three to four unit cells) PbZr_0.2Ti_0.8O₃ thickness and an area of 0.04 μm² can be switched by about 1 V yielding a resistive ON/OFF-ratio of about 300 at 0.4 V. Combined piezoresponse force microscopy and electronic transport investigations of these junctions reveal …

Orientation Of Doubly Excited States In N2, John E. Furst, Timothy J. Gay, Joshua Machacek, David Kilkoyne, Kenneth W. Mclaughlin

Timothy J. Gay Publications

We have measured the total fluorescent intensity and circular polarization of light emitted in 3p ⁴P^o → 3s⁴P transitions of excited neutral nitrogen atoms created by the photofragmentation of the N₂ molecule with circularly polarized light having energies between 21 and 26 eV. The intensity measurements show the effect of predissociation of the N₂ Rydberg series R(C) ¹Σ⁺_u states by non-Rydberg doubly excited resonances (NRDERs), while nonzero values of circular polarization allow us to unambiguously identify the presence of a directly excited NRDER with ¹Π …

A Novel Fixed-Target Task To Determine Articulatory Speed Constraints In Persons With Amyotrophic Lateral Sclerosis, Antje Mefferd, Jordan R. Green, Gary L. Pattee

Department of Special Education and Communication Disorders: Faculty Publications

Purpose: The goal of this study was to determine if talkers with ALS are limited in their ability to increase lower lip and jaw speed at an early stage of the disease when their speaking rate and intelligibility are only minimally or not affected.

Method: A novel metronome paced fixed-target task was used to assess movement speed capacities during lower lip and jaw oscillations in seven talkers with ALS and seven age and gender matched controls.

Results: Lower lip peak speeds were significantly lower in talkers with mild ALS than in healthy talkers suggesting a lower lip speed constraint in …

Modification Of Perioral Stiffness In Patients With Repaired Cleft Lip And Palate, Steven M. Barlow, Carroll-Ann Trotman, Shin-Ying Chu, Jaehoon Lee

Department of Special Education and Communication Disorders: Faculty Publications

Objective—To measure and compare the perioral stiffness among three groups of pediatric subjects: a group of patients with a repaired cleft lip (and palate) who had a secondary lip revision surgery (revision), another group of patients with repaired cleft lip (and palate) who did not have secondary surgery (nonrevision), and a group of noncleft “normal” patients (noncleft).

Design—A parallel, three-group, nonrandomized clinical trial.

Participants—A total of 16 patients with repaired cleft lip/palate who did not have lip revision, 13 patients with repaired cleft lip/palate who had lip revision surgery and were tested at 18 to 24 months postsurgery, and 27 …

Imbalance Fault Detection Of Direct-Drive Wind Turbines Using Generator Current Signals, Xiang Gong, Wei Qiao

Department of Electrical and Computer Engineering: Faculty Publications

Imbalance faults constitute a significant portion of all faults in wind turbine generators (WTGs). WTG imbalance fault detection using generator current measurements has advantages over traditional vibration-based methods in terms of cost, implementation, and system reliability. However, there are challenges in using current signals for imbalance fault detection due to low signal-to-noise ratio of the useful information in current signals and non-stationary characteristic frequencies of imbalance faults. This paper proposes a method of using generator stator currents for imbalance fault detection of direct-drive WTGs. In the proposed method, the variable shaft rotating frequency of a WTG is estimated from one …

Power Semiconductor Devices, Jerry Hudgins, Rik W. De Doncker

Department of Electrical and Computer Engineering: Faculty Publications

Historically, Power Semiconductor devices have been divided into three broad categories: diodes, transistors, and thyristors. Although modern devices can be classified in this way, there is an increasing overlap in device design and function. Also semiconductors, such as silicon carbide (SiC), gallium nitride (GaN), and other materials, as well as novel device designs have increased the suitability and broadened the applications of semiconductor switches in megawatt (MW) power conversion circuits and systems.

Modern Transistors

Transistors include the traditional power bipolar (nonsilicon materials being considered for the future), power metal-oxide-semiconductor field-effect transistors (MOSFETs), and hybrid devices that have some aspect of …

A Series-Connected Self-Reconfigurable Multicell Battery Capable Of Safe And Effective Charging/Discharging And Balancing Operations, Taesic Kim, Wei Qiao, Liyan Qu

Department of Electrical and Computer Engineering: Faculty Publications

Bidirectional DC/DC converters are commonly used for charging and discharging multicell batteries under various modes, such as Pulsed Current (PC), Constant Current (CC), and Constant Current Constant Voltage (CCCV). The charge and discharge are usually terminated by the converters when battery voltages reach some threshold values. However, cell state imbalance is commonly present in traditional multicell batteries, which reduces the available capacities of the batteries in certain charge/discharge cycles and shortens the life cycles of the batteries. To solve this problem, this paper proposes a series-connected, self-reconfigurable, multicell battery with a bidirectional DC/DC converter capable of safe and effective charging, …

Analysis Of Π-Phase-Shifted Fiber Bragg Gratings For Ultrasonic Detection, Tongqing Liu, Ming Han

Department of Electrical and Computer Engineering: Faculty Publications

Using numerical simulations, we investigated the responses of the π-phase-shifted fiber Bragg gratings (πFBGs) impinged by pressure ultrasonic waves. The effect of the grating length, grating refractive index modification depth, and ultrasonic frequency on the wavelength sensitivity and intensity sensitivity of the πFBG ultrasonic sensor for ultrasonic waves of different wavelengths was analyzed. The directivity of a πFBG sensor was also studied. Our analysis revealed several unique πFBG response characteristics and will be useful in the design and optimization of fiber-optic ultrasonic sensors that use a πFBG as the sensing element.

Real-Time Stereo Matching On Cuda Using An Iterative Refinement Method For Adaptive Support-Weight Correspondences, Jedrzej Kowalczuk, Eric T. Psota, Lance C. Pérez

Department of Electrical and Computer Engineering: Faculty Publications

High-quality real-time stereo matching has the potential to enable various computer vision applications including semi-automated robotic surgery, tele-immersion, and three-dimensional video surveillance. A novel real-time stereo matching method is presented that uses a two-pass approximation of adaptive support-weight aggregation, and a low-complexity iterative disparity refinement technique. Through an evaluation of computationally efficient approaches to adaptive support weight cost aggregation, it is shown that the two-pass method produces an accurate approximation of the support weights while greatly reducing the complexity of aggregation. The refinement technique, constructed using a probabilistic framework, incorporates an additive term into matching cost minimization and facilitates iterative …

Optical Properties Of Cobalt Slanted Columnar Thin Films Passivated By Atomic Layer Deposition, Daniel Schmidt, Eva Schubert, Mathias Schubert

Department of Electrical and Computer Engineering: Faculty Publications

Optical properties of passivated metal slanted columnar thin films from cobalt within the visible spectral region are reported. Glancing angle deposition is utilized to grow slanted nano-columns which have been conformally coated with Al₂O₃ by a subsequent atomic layer deposition process. A generalized anisotropic Bruggeman effective medium approximation has been employed to analyze spectroscopic generalized ellipsometry data. The modified homogenization approach allows for determination of biaxial (monoclinic) optical and structural properties as well as fractions of three film constituents. The conformal alumina passivation layer preserves the pristine metal character of the nano-structures and prevents oxidation and aging …

Position Extraction From A Discrete Sliding-Mode Observer For Sensorless Control Of Ipmsms, Yue Zhao, Wei Qiao, Long Wu

Department of Electrical and Computer Engineering: Faculty Publications

Sliding-mode observers (SMOs) offer a promising solution for sensorless control of interior permanent magnet synchronous machines (IPMSMs) due to their excellent robustness to system structure and parameter uncertainty. However, in practical applications, it is challenging for an SMO to achieve a perfect estimation for the back electromagnetic force (EMF) using a finite or relatively lower sampling frequency, especially for high-speed applications. Phase shift, magnitude variation, and heavy noise in the estimated back EMF will cause unexpected errors in rotor position extraction. Thus, advanced rotor position extraction methods are needed to obtain position information from the estimated back EMF. This paper …

Compensation Algorithms For Sliding Mode Observers In Sensorless Control Of Ipmsms, Yue Zhao, Wei Qiao, Long Wu

Department of Electrical and Computer Engineering: Faculty Publications

Electromechanical sensors are commonly used to obtain rotor position/speed for high-performance control of interior permanent magnet synchronous machines (IPMSMs) in vehicle systems. However, the use of these sensors increases the cost, size, weight, wiring complexity and reduces the mechanical robustness of IPMSM drive systems. These issues, together with some practical requirements, e.g., wide speed range, extreme environment temperature, and adverse loading conditions, make a sensorless control scheme desirable. This paper proposes an extended back electromotive force (EMF)-based sliding mode rotor position observer for sensorless vector control of IPMSMs. Based on filter characteristics, a robust compensation algorithm is developed to improve …

Adaptation Of Reduction Indices To North American Assemblages: Developing A Methodology For The Investigation Of The Quarry Creek Assemblages, Ft. Leavenworth, Kansas, Eric Skov

Nebraska Anthropologist

Reduction measures, especially those measures which compute a scaled index, have been profitably employed in archaeological research on many Old World assemblages. Utilization of these techniques is still a burgeoning subject in North American archaeology, however, and North American assemblages present unique challenges to the analyst. Chief among these difficulties are the greater prevalence of hafted bifaces and other formal tools, especially when contrasted to the Mousterian toolkits that have been the traditional targets for reduction analyses. Other researchers have developed new methods for analyzing projectile points or end scrapers, though these methods are not without weaknesses and I am …

Developing An Electronic Repository For Undergraduate Theses, Foster Levy, Rebecca Pyles, Celia Szarejko, Linda Wyatt

Honors in Practice Online Archive

Undergraduate honors theses represent an intellectual asset that a university should recognize and manage as such. However, when theses were submitted exclusively in print copies, the work often faded into obscurity, forgotten by all but the student and mentor. While theses for advanced degrees have been accessible for many years via interlibrary loan or abstract services, similar access options have been unavailable for undergraduate theses because these works are most often associated with and maintained by the institutional honors program without involvement or support from the institution’s library system. At best, an index of undergraduate theses might be available to …

Experimental Testing And Finite-Element Modeling To Evaluate The Effects Of Aggregate Angularity On Bituminous Mixture Performance, Leonardo T. Souza, Yong-Rak Kim, Flavio V. Souza, Leandro S. Castro

Department of Engineering Mechanics: Faculty Publications

This study evaluates the effects of aggregate angularity in bituminous mixtures. Previous studies have predominantly focused on the effects of aggregate angularity on the resistance to permanent deformation, while little work has investigated the role of aggregate angularity related to mixture volumetrics and fatigue fracture performance. To investigate the effect of aggregate angularity on mixture performance and characteristics, five mixes with different combinations of coarse and fine aggregate angularity are evaluated by performing the uniaxial static creep test and the indirect tensile fracture energy test. The asphalt pavement analyzer test is also performed with five-year field project mixtures. Fracture energy …

A Low-Cost, Reliable, High-Throughput System For Rodent Behavioral Phenotyping In A Home Cage Environment, Steven A. Parkison, Jay D. Carlson, Tammy R. Chaudoin, Traci A. Hoke, A. Katrin Schenk, Evan H. Goulding, Lance C. Pérez, Stephen J. Bonasera

Department of Electrical and Computer Engineering: Faculty Publications

Inexpensive, high-throughput, low maintenance systems for precise temporal and spatial measurement of mouse home cage behavior (including movement, feeding, and drinking) are required to evaluate products from large scale pharmaceutical design and genetic lesion programs. These measurements are also required to interpret results from more focused behavioral assays. We describe the design and validation of a highly-scalable, reliable mouse home cage behavioral monitoring system modeled on a previously described, one-ofa- kind system [1]. Mouse position was determined by solving static equilibrium equations describing the force and torques acting on the system strain gauges; feeding events were detected by a photobeam …

Nonlinear Plasmonic Cloaks To Realize Giant All-Optical Scattering Switching, Christos Argyropoulos, Pai-Yen Chen, Francesco Monticone, Giuseppe D'Aguanno, Andrea Alu

Department of Electrical and Computer Engineering: Faculty Publications

Here we extend the reach of Fano resonant coupling by combining this concept with cloaking and plasmonic resonances in a single nonlinear nanoparticle, in order to realize giant all-optical scattering nanoswitches controlled by moderate pumping intensities. We show that a core-shell nonlinear plasmonic particle may be designed to abruptly switch from being completely cloaked to being strongly resonant, with up to a 40 dB cross-sectional difference. Self-tunable optical cloaks and resonant scatterers are envisioned for use as efficient all-optical switches and nanomemories.

Boosting Optical Nonlinearities In E-Near-Zero Plasmonic Channels, Christos Argyropoulos, Pai-Yen Chen, Giuseppe D'Aguanno, Nadar Engheta, Andrea Alu

Department of Electrical and Computer Engineering: Faculty Publications

The anomalous transmission properties of zero-permittivity ultranarrow channels are used to boost Kerr nonlinearities and achieve switching and bistable response for moderate optical intensities. Strong field enhancement, uniform all along the channel, is a typical feature of ε-near-zero supercoupling and is shown to be particularly suited to enhance nonlinear effects. This is obtained by designing narrow apertures at cutoff in a plasmonic screen. We show that this nonlinear mechanism can significantly outperform nonlinearities in traditional Fabry-P´erot resonant gratings.

Laser Induced Breakdown Spectroscopy Having Enhanced Signal-To-Noise Ratio, Dennis R. Alexander, Troy Anderson, John C. Bruce Iii

Department of Electrical and Computer Engineering: Faculty Publications

A material can be analyzed using short pulses by applying a first pulse and a second pulse to the material in which the second pulse is delayed relative to the first pulse. The first and second pulses are directed toward a material along collinear paths, and the material is ablated using the first pulse to cause particles to be emitted from the surface of the material. The emitted particles are atomized and/or ionized using the second pulse, and the radiation from the atomized and/or ionized particles is analyzed.

The Gentle Art Of Mentoring In Higher Education, Nancy H. Barry

To Improve the Academy: A Journal of Educational Development

No abstract provided.

Time To Raise Questions About Student Ratings, Linda B. Nilson

To Improve the Academy: A Journal of Educational Development

No abstract provided.

Understanding Intersecting Processes, Kristen A. Renn

To Improve the Academy: A Journal of Educational Development

No abstract provided.

Empirical Correction For Spectroscopic Ellipsometric Measurements Of Rough Or Textured Surfaces, Craig M. Herzinger, Blaine D. Johs, Mathias M. Schubert, Tino Hofmann

Department of Electrical and Computer Engineering: Faculty Publications

A method of applying spectroscopic ellipsometry to arrive at accurate values of optical and physical properties for thin films on samples having rough or textured surfaces.

Modeling Broad-Scale Patterns Of Avian Species Richness Across The Midwestern United States With Measures Of Satellite Image Texture, Patrick D. Culbert, Volker C. Radeloff, Véronique St-Louis, Curtis H. Flather, Chadwick D. Rittenhouse, Thomas P. Albright, Anna M. Pidgeon

United States Department of Agriculture, Forest Service / University of Nebraska-Lincoln: Faculty Publications

Avian biodiversity is threatened, and in order to prioritize limited conservation resources and conduct effective conservation planning a better understanding of avian species richness patterns is needed. The use of image texture measures, as a proxy for the spatial structure of land cover and vegetation, has proven useful in explaining patterns of avian abundance and species richness. However, prior studies that modeled habitat with texture measures were conducted over small geographical extents and typically focused on a single habitat type. Our goal was to evaluate the performance of texture measures over broad spatial extents and across multiple habitat types with …

Investigating The Influence Of Lidar Ground Surface Errors On The Utility Of Derived Forest Inventories, Wade T. Tinkham, Alistair M.S. Smith, Chad Hoffman, Andrew T. Hudak, Michael J. Falkowski, Mark E. Swanson, Paul E. Gessler

United States Department of Agriculture, Forest Service / University of Nebraska-Lincoln: Faculty Publications

Light detection and ranging, or LiDAR, effectively produces products spatially characterizing both terrain and vegetation structure; however, development and use of those products has outpaced our understanding of the errors within them. LiDAR’s ability to capture three-dimensional structure has led to interest in conducting or augmenting forest inventories with LiDAR data. Prior to applying LiDAR in operational management, it is necessary to understand the errors in Li- DAR-derived estimates of forest inventory metrics (i.e., tree height). Most LiDAR-based forest inventory metrics require creation of digital elevation models (DEM), and because metrics are calculated relative to the DEM surface, errors within …

Identifying U.S. First Ladies Involved With Child And Youth Serving Organizations, Greta A. Johnson

Graduate Research Papers

The purpose of this study is to identify how U.S. First Ladies have significantly impacted child or youth programs and causes. This will cover six First Ladies from the 1900's to the present which include: 1) Lou Hoover; 2) Lady Bird Johnson; 4) Nancy Reagan; 3) Barbara Bush; 5) Laura Bush; and 6) Michelle Obama.