Search

Your search keyword '"Thompson, Gregory"' showing total 1,526 results
Start Over Author "Thompson, Gregory"

Refine your results

more »

more »

more »

more »

more »

more »
1,526 results on '"Thompson, Gregory"'

6. Chemical Partitioning at Crystalline Defects in PtAu as a Pathway to Stabilize Electrocatalysts

Author

Zhou, Xuyang, Kasian, Olga, Luo, Ting, Kim, Se-Ho, Zhang, Chenyu, Zhang, Siyuan, Lee, Subin, Thompson, Gregory B., Dehm, Gerhard, Gault, Baptiste, and Raabe, Dierk

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

Dissolution of electrocatalysts during long-term and dynamic operation is a challenging problem in energy conversion and storage devices such as fuel cells and electrolyzers. To develop stable electrocatalysts, we adopt the design concept of segregation engineering, which uses solute segregation prone to electrochemical dissolution at internal defects, i.e., grain boundaries and dislocations. We showcase the feasibility of this approach by stabilizing a model Pt catalyst with an addition of more noble Au (approximately 5 atomic percent). We characterized the defects' nanoscale structure and chemistry, and monitored the electrochemical dissolution of Pt and PtAu alloys by online inductively coupled plasma mass spectrometry. Once segregated to defects, Au atoms can stabilize and hence passivate the most vulnerable sites against electrochemical dissolution and improve the stability and longevity of the Pt electrocatalysts by more than an order of magnitude. This opens pathways to use solute segregation to defects for the development of more stable nanoscale electrocatalysts, a concept applicable for a wide range of catalytic systems.

Published
2022

8. Temporal Fluency and Floor/Ceiling Scoring of Intermediate and Advanced Speech on the ACTFL Spanish Oral Proficiency Interview--Computer

Author

Cox, Troy L., Brown, Alan V., and Thompson, Gregory L.

Abstract

The rating of proficiency tests that use the Inter-agency Roundtable (ILR) and American Council on the Teaching of Foreign Languages (ACTFL) guidelines claims that each major level is based on hierarchal linguistic functions that require mastery of multidimensional traits in such a way that each level subsumes the levels beneath it. These characteristics are part of what is commonly referred to as floor and ceiling scoring. In this binary approach to scoring that differentiates between sustained performance and linguistic breakdown, raters evaluate many features including vocabulary use, grammatical accuracy, pronunciation, and pragmatics, yet there has been very little empirical validation on the practice of floor/ceiling scoring. This study examined the relationship between temporal oral fluency, prompt type, and proficiency level based on a data set comprised of 147 Oral Proficiency Interview - computer (OPIc) exam responses whose ratings ranged from Intermediate Low to Advanced High [AH]. As speakers progressed in proficiency, they were more fluent. In terms of floor and ceiling scoring, the prompts that elicited speech a level above the sustained level generally resulted in speech that was slower and had more breakdown than the floor-level prompts, though the differences were slight and not significantly different. Thus, temporal fluency features alone are insufficient in floor/ceiling scoring but are likely a contributing feature.

Published
2023
Full Text
View/download PDF

9. Virtual Language Exchanges in Lower-Level Language Classes: Promise and Practice

Author

Martinsen, Rob A. and Thompson, Gregory L.

Abstract

Interacting with native speakers in various types of virtual exchanges is becoming increasingly accessible for language learners and teachers around the world. The present study examined the experiences of beginning and intermediate level learners of Spanish in the United States as they interacted weekly with native Spanish speakers over the course of three academic years. Students were assigned to face-to-face settings or one of a variety of virtual exchange platforms including both free and paid services. The unique opportunities created by the structure and features of each setting whether face-to-face or online did seem to have an effect on the students' experiences and were visible in the data analysis. Results indicate that students' gender and the context in which they interacted with native Spanish speakers were related to greater or lesser changes in students' motivation, willingness to communicate and perceived learning. Additionally, engaging with a paid interlocutor in a setting with few technological issues seemed to improve outcomes.

Published
2023
Full Text
View/download PDF

16. Revealing in-plane grain boundary composition features through machine learning from atom probe tomography data

Author

Zhou, Xuyang, Wei, Ye, Kühbach, Markus, Zhao, Huan, Vogel, Florian, Kamachali, Reza Darvishi, Thompson, Gregory B., Raabe, Dierk, and Gault, Baptiste

Subjects
Condensed Matter - Materials Science
Abstract

Grain boundaries (GBs) are planar lattice defects that govern the properties of many types of polycrystalline materials. Hence, their structures have been investigated in great detail. However, much less is known about their chemical features, owing to the experimental difficulties to probe these features at the atomic length scale inside bulk material specimens. Atom probe tomography (APT) is a tool capable of accomplishing this task, with an ability to quantify chemical characteristics at near-atomic scale. Using APT data sets, we present here a machine-learning-based approach for the automated quantification of chemical features of GBs. We trained a convolutional neural network (CNN) using twenty thousand synthesized images of grain interiors, GBs, or triple junctions. Such a trained CNN automatically detects the locations of GBs from APT data. Those GBs are then subjected to compositional mapping and analysis, including revealing their in-plane chemical decoration patterns. We applied this approach to experimentally obtained APT data sets pertaining to three case studies, namely, Ni-P, Pt-Au, and Al-Zn-Mg-Cu alloys. In the first case, we extracted GB-specific segregation features as a function of misorientation and coincidence site lattice character. Secondly, we revealed interfacial excesses and in-plane chemical features that could not have been found by standard compositional analyses. Lastly, we tracked the temporal evolution of chemical decoration from early-stage solute GB segregation in the dilute limit to interfacial phase separation, characterized by the evolution of complex composition patterns. This machine-learning-based approach provides quantitative, unbiased, and automated access to GB chemical analyses, serving as an enabling tool for new discoveries related to interface thermodynamics, kinetics, and the associated chemistry-structure-property relations.

Published
2021

49. Academic Language: Is This Really (Functionally) Necessary?

Author

Thompson, Gregory A. and Watkins, Kathryn

Abstract

In this article we critically evaluate the case made by proponents of academic language (AL) that AL is functionally necessary for schooling due to specific functional advantages of AL. We consider three examples of AL introduced by AL proponents in order to show (1) that AL proponents have been too quick to accept the ALH, (2) that functional advantages of AL can be accomplished with non-AL varieties and 3) that AL may, in fact, be dysfunctional within the domain of schooling. We briefly describe the language ideological processes by which AL has been naturalized as appropriate to the domain of education while the functional potential of non-AL forms in schooling is obviated (noted by Halliday 2004). We then consider the work of M. A. K. Halliday, the researcher most commonly cited as providing justification for the ALH (esp. Halliday 2004), elaborating his critique of AL while also showing how this critique has been ignored by AL proponents citing his work. In closing we point to some implications of these findings for creating more equitable educational practices regarding academic language.

Published
2021
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results