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5,861 results on '"Park HO"'

1. Binomial convolution sum of divisor functions associated with Dirichlet character modulo 8

Author

Jin Seokho and Park Ho

Subjects
divisor function, dirichlet character, convolution sum, arithmetic identity, eisenstein series, 11a25, 11e25, 11f11, 11f20, 11f30, Mathematics, QA1-939
Abstract

In this article, we compute binomial convolution sums of divisor functions associated with the Dirichlet character modulo 8, which is the remaining primitive Dirichlet character modulo powers of 2 yet to be considered. To do this, we provide an explicit expression of a general modular form of even weight for Γ0(32){\Gamma }_{0}\left(32) in terms of its basis, and use an identity of Huard, Ou, Spearman, and Williams. As an application, we also compute the number of representations by quadratic forms under parity conditions.

Published
2024
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2. The multinomial convolution sum of a generalized divisor function

Author

Park Ho

Subjects
divisor functions, convolution sums, 11a25, 11y70, Mathematics, QA1-939
Abstract

The main theorem of this article is to evaluate and express the multinomial convolution sum of the divisor function σr♯(n;N/4,N){\sigma }_{r}^{\sharp }\left(n;\hspace{0.33em}N\hspace{-0.08em}\text{/}\hspace{-0.08em}4,N) in as a simple form as possible, where N/4N\hspace{-0.08em}\text{/}\hspace{-0.08em}4 is an arbitrary odd positive integer. This generalizes previous result in combination with Cho and Kim, which is about the case N=4N=4. While obtaining our main theorem, we derive some generalizations of other identities to the case that we are dealing with.

Published
2022
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7. Four ESOL Graduate Students' Hybrid Learning through a Reflective Project: A Qualitative Case Study

Author

Park, Ho-Ryong

Abstract

This is a qualitative case study to investigate English for Speakers of Other Languages (ESOL) graduate students' learning experiences when completing a reflective project. Four graduate students in the United States participated in this study and completed the project to share their linguistic and cultural stories in a traditional paper-based essay format and in a multimedia format. The data consisted of a reflection paper, digital storytelling (DST), a project report, an oral presentation, and an interview, which were analysed through content analysis. The findings included participants' learning of (a) language and culture, (b) language teaching, (c) language teachers' responsibilities, and (d) technology. These showed that ESOL graduate students' dialogues with preceding, current, and future utterances indicated their hybrid learning experiences through traditional and technology-mediated reflective tasks. The author discussed the influences of dialogues within their hybrid learning. In addition, pedagogical implications of a combined project between a reflection paper and DST and the instructional elements of DST that teachers need to consider were suggested.

Published
2023

14. Machine Learning Assisted Design and Optimization of Transition Metal-Incorporated Carbon Quantum Dot Catalysts for Hydrogen Evolution Reaction

Author

Nguyen, Duong Nguyen, Kim, Min-Cheol, Baeck, Unbeom, Lim, Jaehyoung, Shin, Namsoo, Kim, Jaekook, Choi, Heechae, Park, Ho Seok, Sim, Uk, and Kim, Jung Kyu

Subjects
Physics - Chemical Physics, Condensed Matter - Other Condensed Matter
Abstract

Development of cost-effective hydrogen evolution reaction (HER) catalysts with outstanding catalytic activity, replacing cost-prohibitive noble metal-based catalysts, is critical for practical green hydrogen production. A popular strategy for promoting the catalytic performance of noble metal-free catalysts is to incorporate earth-abundant transition metal (TM) atoms into nanocarbon platforms such as carbon quantum dots (CQDs). Although data-driven catalyst design methods can significantly accelerate the rational design of TM element-doped CQD (M@CQD) catalysts, they suffer from either a simplified theoretical model or the prohibitive cost and complexity of experimental data generation. In this study, we propose an effective and facile HER catalyst design strategy based on machine learning (ML) and ML model verification using electrochemical methods accompanied with density functional theory (DFT) simulations. Based on a Bayesian genetic algorithm (BGA) ML model, the Ni@CQD catalyst on a three-dimensional reduced graphene oxide (3D rGO) conductor is proposed as the best HER catalyst under the optimal conditions of catalyst loading, electrode type, and temperature and pH of electrolyte. We validate the ML results with electrochemical experiments, where the Ni@CQD catalyst exhibited superior HER activity, requiring an overpotential of 189 mV to achieve 10 mA cm-2 with a Tafel slope of 52 mV dec-1 and impressive durability in acidic media. We expect that this methodology and the excellent performance of the Ni@CQD catalyst provide an effective route for the rational design of highly active electrocatalysts for commercial applications.

Published
2022

23. Zn-Ion Transporting, In Situ Formed Robust Solid Electrolyte Interphase for Stable Zinc Metal Anodes over a Wide Temperature Range

Author

Xiong, Peixun, Kang, Yingbo, Yao, Nan, Chen, Xiang, Mao, Haiyan, Jang, Woo-Sung, Halat, David M, Fu, Zhong-Heng, Jung, Min-Hyoung, Jeong, Hu Young, Kim, Young-Min, Reimer, Jeffrey A, Zhang, Qiang, and Park, Ho Seok

Subjects
Engineering, Materials Engineering, Chemical Sciences, Physical Chemistry, Affordable and Clean Energy, Chemical sciences
Abstract

Hydrogen evolution, corrosion, and dendrite formation in the Zn anodes limit their practical applications in aqueous Zn metal batteries. Herein, we propose an interfacial chemistry regulation strategy that uses hybrid electrolytes of water and a polar aprotic N,N-dimethylformamide to modify the Zn2+-solvation structure and in situ form a robust and Zn2+-conducting Zn5(CO3)2(OH)6 solid electrolyte interphase (SEI) on the Zn surface to achieve stable and dendrite-free Zn plating/stripping over a wide temperature range. As confirmed by 67Zn nuclear magnetic resonance relaxometry, electrochemical characterizations, and molecular dynamics simulation, the electrochemically and thermally stable Zn5(OH)6(CO3)2-contained SEI achieved a high ionic conductivity of 0.04 to 1.27 mS cm-1 from −30 to 70 °C and a thermally activated fast Zn2+ migration through the [010] plane. Consequently, extremely stable Zn-ion hybrid capacitors in hybrid electrolytes are demonstrated with high capacity retentions and Coulombic efficiencies over 14,000, 10,000, and 600 cycles at 25, −20, and 70 °C, respectively.

Published
2023

24. The Potential of Fluralaner as a Bait Toxicant to Control Pest Yellowjackets in California

Author

Rust, Michael K, Lee, Chow-Yang, Park, Ho Eun, Campbell, Kathleen, Choe, Dong-Hwan, Sorensen, Mary, Sutherland, Andrew, Hubble, Casey, Nobua-Behrmann, Beatriz, Kabashima, John, Tseng, Shu-Ping, and Post, Linda

Subjects
Zoology, Biological Sciences, Vespula pensylvanica, isoxazoline, fluralaner, hydrogel baits
Abstract

The western yellowjacket, Vespula pensylvanica (Saussure), is an important seasonal pest of recreational and outdoor venues in the western United States. Its propensity to scavenge food increases the likelihood of stinging incidences. Control measures are limited to intensive trapping and treating subterranean nests. The only toxicant registered for baiting in the US is esfenvalerate, which is ineffective. The objective of this study was to determine the potential of the isoxazoline fluralaner as a bait toxicant. With microsatellite genotyping, a minimum of 27 different colonies were shown to forage at a single monitoring site. Some colonies disappeared after baiting, and new colonies were detected. The implications for baiting and monitoring are discussed. Minced chicken and hydrogel baits containing 0.022% and 0.045% fluralaner significantly reduced foraging yellowjackets. Several bait applications covering large areas will be necessary to provide long-term control.

Published
2023

40. Performance Characteristics of Compact Mobile LIFS (Laser-Induced Fluorescence Spectrum) Lidar

Author

Tomida Takayuki, Nishizawa Naoto, Sakurai Kosuke, Suganumata Hikaru, Tsukada Shodai, Song Sung-Moo, Park Ho-Dong, and Saito Yasunori

Subjects
Physics, QC1-999
Abstract

We developed a compact but versatile laser-induced fluorescence spectrum (LIFS) lidar that has potential use for material or aerosol identification outside experimental rooms. The compactness and mobility of the LIFS lidar means observations can be more freely conducted at any place and any time. Its performance characteristics were validated by threedimensional fluorescence imaging of targets and remote detection of quasi bio/organic aerosols.

Published
2016
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