Remote Aerial Mapping Spectrometer

According to the EPA, harmful algal blooms may occur more frequently in coastal areas like the Chesapeake Bay due to warming waters and increased nutrient pollution. Algal blooms cause aquatic dead zones which damage the ecosystem and can produce toxins which are dangerous to animals and humans. Continual environmental monitoring is required to research algal blooms and to prevent harm to residents and industries. We researched technologies to locate harmful algal blooms and found spectroscopic remote surveying an effective approach. A material’s wavelength-dependent reflectance reveals its material composition. Unfortunately, existing methods which can map spectral characteristics are lacking. Field researchers with handheld spectrometers may analyze nearby vegetation’s identity and health but surveying a large area is time-consuming. Alternatively, hyperspectral cameras mounted to aircraft and satellites can gather data from a wide region but are cost prohibitive for local studies and provide limited spatial resolution. We designed a spectral mapping sensor payload for mounting on unmanned aerial vehicles. The Remote Aerial Mapping Spectrometer (RAMS) adapts to any aircraft able to carry its low weight because it is self-powered and includes all necessary sensors. It scans its surroundings with a laser rangefinder and spectrometer with a long-focus lens. RAMS monitors the orientation of its sensor package and computes a three-dimensional map of nearby material signatures. This graphical representation of localized spectra will assist in charting harmful algal blooms but also monitor forests threatened by invasive species and provide pinpoint agricultural analytics. RAMS makes environmental data richer and more cost-effective than current techniques.https://scholarscompass.vcu.edu/capstone/1191/thumbnail.jp

Numerical Modeling of Dynamic Loss in HTS-Coated Conductors Under Perpendicular Magnetic Fields

© 2017 IEEE. High-Tc superconducting (HTS)-coated conductors are a promising option for the next-generation power devices. However, their thin-film geometry incurs dynamic loss when exposed to a perpendicular external ac magnetic field, which is difficult to predicate and estimate. In this paper, we propose and verify a numerical simulation model to predict the dynamic loss in HTS-thin-coated conductors by taking into account their Jc-B dependence and I-V characteristics. The model has been tested on a SuperPower YBCO-coated conductor, and we observed a linear increase of dynamic loss along the increasing field amplitude after the threshold field. Our simulation results agree closely with experimental measurements as well as an analytical model. Furthermore, the model can predict the nonlinear increase of dynamic loss at high current, while the analytical model deviates from the measurement results and still shows a linear correlation between the dynamic loss and the external magnetic field. In addition, we have used this model to simulate the distributions of magnetic field and current density when dynamic loss occurs. Results clearly show the flux traversing the coated conductor, which causes dynamic loss. These distributions have also been used to analyze the change of dynamic loss when either the transport current or the magnetic field increase individually, while the other factor remains constant. The simulation analysis on dynamic loss is done for the first time in this paper, and our results clearly demonstrate how dynamic loss changes as well as its dependence on transport current and magnetic field. © 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

Dynamic resistance measurement in a four-tape YBCO stack with various applied field orientation

The dynamic resistance which occurs when a superconductor carrying DC current is exposed to alternating magnetic field plays an important role in HTS applications such as flux pumps and rotating machines. We report experimental results on dynamic resistance in a four-tape coated conductor stack when exposed to AC magnetic fields with different magnetic field angles (the angles between the magnetic field and normal vector component of the tape surface, θ) at 77 K. The conductors for the stack are 4-mm-wide SuperPower SC4050 wires. The field angle was varied from 0° to 120° at a resolution of 15° to study the field angle dependence of dynamic resistance on field angle as well as wire Ic (B, θ). We also varied the field frequency, the magnetic field amplitude, and the DC current level to study the dependence of dynamic resistance on these parameters. Finally, we compared the measured dynamic resistance results at perpendicular magnetic field with the analytical models for single wires. Our results show that the dynamic resistance of the stack was mainly, but not solely, determined by the perpendicular magnetic component. Ic (B, θ) influences dynamic resistance in the stack due to tilting of the crystal lattice of the superconductor layer with regard to buffer layers. © 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

A new method applied for explaining the landing patterns:interpretability analysis of machine learning

As one of many fundamental sports techniques, the landing maneuver is also frequently used in clinical injury screening and diagnosis. However, the landing patterns are different under different constraints, which will cause great difficulties for clinical experts in clinical diagnosis. Machine learning (ML) have been very successful in solving a variety of clinical diagnosis tasks, but they all have the disadvantage of being black boxes and rarely provide and explain useful information about the reasons for making a particular decision. The current work validates the feasibility of applying an explainable ML (XML) model constructed by Layer-wise Relevance Propagation (LRP) for landing pattern recognition in clinical biomechanics. This study collected 560 groups landing data. By incorporating these landing data into the XML model as input signals, the prediction results were interpreted based on the relevance score (RS) derived from LRP. The interpretation obtained from XML was evaluated comprehensively from the statistical perspective based on Statistical Parametric Mapping (SPM) and Effect Size. The RS has excellent statistical characteristics in the interpretation of landing patterns between classes, and also conforms to the clinical characteristics of landing pattern recognition. The current work highlights the applicability of XML methods that can not only satisfy the traditional decision problem between classes, but also largely solve the lack of transparency in landing pattern recognition. We provide a feasible framework for realizing interpretability of ML decision results in landing analysis, providing a methodological reference and solid foundation for future clinical diagnosis and biomechanical analysis

The dynamic resistance of YBCO coated conductor wire: Effect of DC current magnitude and applied field orientation

Dynamic resistance, which occurs when a HTS coated conductor carries a DC current under an AC magnetic field, can have critical implications for the design of HTS machines. Here, we report measurements of dynamic resistance in a commercially available SuperPower 4 mm-wide YBCO coated conductor, carrying a DC current under an applied AC magnetic field of arbitrary orientation. The reduced DC current, I t/I c0, ranged from 0.01 to 0.9, where I t is the DC current level and I c0 is the self-field critical current of the conductor. The field angle (the angle between the magnetic field and the normal vector of the conductor wide-face) was varied between 0° and 90° at intervals of 10°. We show that the effective width of the conductor under study is ∼12% less than the physical wire width, and we attribute this difference to edge damage of the wire during or after manufacture. We then examine the measured dynamic resistance of this wire under perpendicular applied fields at very low DC current levels. In this regime we find that the threshold field, B th, of the conductor is well described by the nonlinear equation of Mikitik and Brandt. However, this model consistently underestimates the threshold field at higher current levels. As such, the dynamic resistance in a coated conductor under perpendicular magnetic fields is best described using two different equations for each of the low and high DC current regimes, respectively. At low DC currents where I t/I c0 ≤ 0.1, the nonlinear relationship of Mikitik and Brandt provides the closest agreement with experimental data. However, in the higher current regime where I t/I c0 ≥ 0.2, closer agreement is obtained using a simple linear expression which assumes a current-independent penetration field. We further show that for the conductor studied here, the measured dynamic resistance at different field angles is dominated by the perpendicular magnetic field component, with negligible contribution from the parallel component. Our findings now enable the dynamic resistance of a single conductor to be analytically determined for a very wide range of DC currents and at all applied field angles. This is the Accepted Manuscript version of an article accepted for publication in 'Superconductor Science and Technology'. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6668/aaa49e

Dynamic Resistance Measurement of a Four-tape YBCO Stack in a Perpendicular Magnetic Field

Dynamic resistance occurs when HTS (high-temperature superconductor) coated conductors carry dc current under ac magnetic field. This dissipative effect can play a critical role in many HTS applications. Here, we report on dynamic resistance measurements of a four-tape YBCO stack comprising 4-mm-wide coated conductors, which experience an applied ac perpendicular magnetic field with an amplitude of up to 100 mT. Each tape within the stack carries the same dc current. The magnetic field amplitude, the frequency of the magnetic field, and the dc current magnitude are varied to investigate the influence of these parameters on the dynamic resistance. We find that the threshold field of the stack is significantly larger than that of a single tape when dc current is small, which we attribute to coherent shielding effects from circulating currents present in each wire in the stack. © 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

SHCal13 Southern Hemisphere calibration, 0–50,000 years cal BP

The Southern Hemisphere SHCal04 radiocarbon calibration curve has been updated with the addition of new data sets extending measurements to 2145 cal BP and including the ANSTO Younger Dryas Huon pine data set. Outside the range of measured data, the curve is based upon the Northern Hemisphere data sets as presented in IntCal13, with an interhemispheric offset averaging 43 ± 23 yr modeled by an autoregressive process to represent the short-term correlations in the offset

Scholarly insight Winter 2019: a Data wrangler perspective

Henry Ford famously said that “Any customer can have a car painted any colour that he wants so long as it is black.” Similarly, our Prime Minister Theresa May indicated in 2016 to aim for a “red, white and blue Brexit”. While the Open University (OU) has been open for 50 years to all learners, we are aware that our students have unique and different learning needs, experiences, and expertise. The OU recognises that we need to carefully listen to our students, and focus on their needs. Nonetheless, in some of our narratives we tend to simplify and generalise these multiple, complex student voices into one common voice. As highlighted in all three chapters in this fifth Scholarly Insight report, working intensively together with the Faculties our Data wranglers have found strong empirical evidence that our students indeed have very unique and distinct voices, which influence their engagement, behaviour, and study success. In Chapter 1 we worked closely together with the four Faculties to further unpack the qualitative feedback and students’ comments of the Student experience on a module (SEAM) survey (e.g., do Open degree students have different narratives when providing feedback; do high performing students “talk” differently from low performing students). Indeed our text analytics toolkit has highlighted that Open degree students speak differently from others (e.g., needing enough study time). Furthermore, higher achieving students report on different topics (e.g., content, feedback, group) than lower achievers (e.g., help, problem, experience). The OU needs to carefully balance these different voices, as addressing one concern from a high achieving student might not necessarily benefit other students, and vice-versa. In Chapter 2 describes three approaches of students selecting different module pathways towards qualification completion. For one Open Degree programme in Creative Writing we find that 268 unique paths are taken by students, whereby some paths are more successful than others. Follow-up analyses in QUAL2F3 indicate substantial differences in pass rates and success depending on the respective route, specialism, and pathways students are taking. Sign-posting these “successful” paths to OU staff and students may help students to make more informed decisions of what to study next. Finally in Chapter 3 we explore how students make timing decisions when to study for a module, and how so-called study break and assessment preparation weeks could help to provide more flexibility for our students. Study breaks are weeks during which no learning activities are planned or take place, and students are not expected to study for a module. Our big data analyses with 123,916 students and 205 OU modules indicate that the way OU designs study weeks has a substantial impact in how students study over time. Study break weeks substantially increase the chances of students to pass a module, while assessment preparation weeks are not related to pass rates We hope that our Scholarly insights can help to inform our staff, but also spark some ideas how to further improve our understanding of the different student voices and qualification pathways