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221 results on '"Cho, Jungho"'

1. A Geodetic and Astrometric VLBI Experiment at 22/43/88/132 GHz

Author

Xu, Shuangjing, Jung, Taehyun, Zhang, Bo, Xu, Ming Hui, Byun, Do-Young, He, Xuan, Sakai, Nobuyuki, Titov, Oleg, Shu, Fengchun, Kim, Hyo-Ryoung, Cho, Jungho, Yoo, Sung-Moon, Choi, Byung-Kyu, Lee, Woo Kyoung, Sun, Yan, Mai, Xiaofeng, and Wang, Guangli

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

Extending geodetic and astrometric Very Long Baseline Interferometry (VLBI) observations from traditional centimeter wavebands to millimeter wavebands offers numerous scientific potentials and benefits. However, it was considered quite challenging due to various factors, including the increased effects of atmospheric opacity and turbulence at millimeter wavelengths. Here, we present the results of the first geodetic-mode VLBI experiment, simultaneously observing 82 sources at 22/43/88/132 GHz (K/Q/W/D bands) using the Korean VLBI Network (KVN). We introduced the frequency phase transfer (FPT) method to geodetic VLBI analysis, an approach for calibrating atmospheric phase fluctuations at higher frequencies by transferring phase solutions from lower frequencies. With a 2-minute scan, FPT improved the signal-to-noise ratio (SNR) of most fringes, some by over 100%, thereby enhancing the detection rate of weak sources at millimeter wavebands. Additionally, FPT reduced systematic errors in group delay and delay rate, with the weighted root-mean-squares (WRMS) of the post-fitting residuals decreasing from 25.0 ps to 20.5 ps at the W band and from 39.3 ps to 27.6 ps at the D band. There were no notable differences observed in calibrating atmospheric phase fluctuations at the K band (WRMS = 12.4 ps) and Q band (WRMS = 11.8 ps) with the KVN baselines. This experiment demonstrated that the millimeter waveband can be used for geodetic and astrometric applications with high precision., Comment: 17 pages, 6 figures, accepted by The Astronomical Journal. Your feedback to improve the manuscript would be greatly appreciated

Published
2024

6. Measurement-based Close-in Path Loss Modeling with Diffraction for Rural Long-distance Communications

Author

Park, Jaedon, Jeon, Hong-Bae, Cho, Jungho, and Chae, Chan-Byoung

Subjects
Electrical Engineering and Systems Science - Signal Processing, Computer Science - Information Theory
Abstract

In this letter, we investigate rural large-scale path loss models based on the measurements in a central area of South Korea (rural area) in spring. In particular, we develop new close-in (CI) path loss models incorporating a diffraction component. The transmitter used in the measurement system is located on a hill and utilizes omnidirectional antennas operating at 1400 and 2250 MHz frequencies. The receiver is also equipped with omnidirectional antennas and measures at positions totaling 3,858 (1,262 positions for LOS and 2,596 positions for NLOS) and 4,957 (1,427 positions for LOS and 3,530 positions for NLOS) for 1400 and 2250 MHz, respectively. This research demonstrates that the newly developed CI path loss models incorporating a diffraction component significantly reduce standard deviations (STD) and are independent of frequency, especially for LOS beyond the first meter of propagation, making them suitable for use with frequencies up to a millimeter-wave., Comment: 5 pages, 5 figures

Published
2023

28. Tritium research activities in Korea

Author

Jung, Ki Jung, Yun, Sei-Hun, Chang, Min Ho, Kang, Hyun-Goo, Chung, Dongyou, Cho, Seungyon, Lee, Hyeon Gon, Chung, Hongsuk, Choi, Woo-Seok, Song, Kyu-Min, Moon, Chang-Bae, Lee, Euy Soo, Cho, Jungho, Kim, Dong-Sun, Moon, Hung-Man, Noh, Seung Jeong, Ju, Hyunchul, and Hong, Tae-Whan

Published
2016
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39. Oxygen deficient yolk–shell structured Co3O4 microspheres as an oxygen evolution reaction electrocatalyst for anion exchange membrane water electrolyzers.

Author

Kim, In Tae, Kim, Sang-Hyun, Ha, Jun Seok, Kim, Tae Ha, Cho, Jungho, Park, Gi Dae, and Park, Yoo Sei

Abstract

Anion exchange membrane water electrolyzers (AEMWEs) are a promising next-generation technology for producing clean hydrogen using cost-effective, non-platinum group metal (non-PGM) based electrocatalysts. Despite their potential advantages, their low energy conversion efficiency presents a significant obstacle to their commercialization. Herein, we developed an oxygen deficient yolk–shell structured Co3O4 as the oxygen evolution reaction electrocatalyst for AEMWEs. The yolk–shell structure provided a large surface area, and the introduction of oxygen vacancies to the yolk–shell structured Co3O4 modulated the electronic structure and enhanced the OER activity. The abundant voids in the yolk–shell structure facilitated mass transport and effectively reduced mass transport loss in the AEMWE, resulting in excellent performance at high current density. This work suggests that the yolk–shell structured electrocatalysts can effectively improve the performance of AEMWEs, thereby addressing the major obstacle that is currently delaying their commercialization. [ABSTRACT FROM AUTHOR]

Published
2023
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46. Impact of minimum wage legislation on gender differentials in sticky wages: evidence from Korea.

Author

Cho, Jungho and Yang, Daecheon

Subjects
WAGE differentials, MINIMUM wage, GENDER wage gap, INCOME inequality, ECONOMIC change
Abstract

This study adds to a growing body of studies on gender inequality, centred on the role of the minimum wage. The unprecedented increases of the minimum wage in Korea during the 2010s allow us to directly observe the social and economic impacts of these changes. This study explores the minimum wage role in mitigating the gender gap in sticky wages where firm performance worsened. Using a sample of 7,514 firm-year observations between 2010 and 2020 in the Korean KOSPI and KOSDAQ markets, we find that men's wage stickiness in times of poor performance was greater than that of women, and the minimum wage reduces the gap in sticky wages between genders, alleviating gender inequality problems in wage determination. [ABSTRACT FROM AUTHOR]

Published
2023
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