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108 results on '"Jeong, Ho-Jung"'

9. Discrimination of Explosive Residues by Standoff Sensing Using Anodic Aluminum Oxide Microcantilever Laser Absorption Spectroscopy with Kernel-Based Machine Learning.

Author

Jeong, Ho-Jung, Park, Chang-Ju, Kim, Kihyun, and Park, Yangkyu

Subjects
*MACHINE learning, *FOURIER transform infrared spectroscopy, *LASER spectroscopy, *PENTAERYTHRITOL tetranitrate, *ALUMINUM oxide
Abstract

Standoff laser absorption spectroscopy (LAS) has attracted considerable interest across many applications for environmental safety. Herein, we propose an anodic aluminum oxide (AAO) microcantilever LAS combined with machine learning (ML) for sensitive and selective standoff discrimination of explosive residues. A nanoporous AAO microcantilever with a thickness of <1 μm was fabricated using a micromachining process; its spring constant (18.95 mN/m) was approximately one-third of that of a typical Si microcantilever (53.41 mN/m) with the same dimensions. The standoff infrared (IR) spectra of pentaerythritol tetranitrate, cyclotrimethylene trinitramine, and trinitrotoluene were measured using our AAO microcantilever LAS over a wide range of wavelengths, and they closely matched the spectra obtained using standard Fourier transform infrared spectroscopy. The standoff IR spectra were fed into ML models, such as kernel extreme learning machines (KELMs), support vector machines (SVMs), random forest (RF), and backpropagation neural networks (BPNNs). Among these four ML models, the kernel-based ML models (KELM and SVM) were found to be efficient learning models able to satisfy both a high prediction accuracy (KELM: 94.4%, SVM: 95.8%) and short hyperparameter optimization time (KELM: 5.9 s, SVM: 7.6 s). Thus, the AAO microcantilever LAS with kernel-based learners could emerge as an efficient sensing method for safety monitoring. [ABSTRACT FROM AUTHOR]

Published
2024
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24. Preparation of high-quality YAG:Ce3+ ceramic phosphor by high-frequency induction heated press sintering methods.

Author

Kwon, Seok Bin, Yoo, Jung Hyeon, Choi, Seung Hee, Na, MinYoung, Kim, Bo Young, Lee, Seon Young, Jeong, Ho-Jung, Kim, Wan Ho, Park, Seoung Hyok, Yoon, Ho Shin, Kang, Bong Kyun, Song, Young Hyun, and Yoon, Dae Ho

Subjects
SINTERING, PHOSPHORS, CERAMICS, OPTICAL properties, TRANSPARENT ceramics, YTTRIUM aluminum garnet, INDUCTION heating
Abstract

This study investigates the characteristics of a ceramic phosphor (CP) for the converter of a high-power laser diode-based automobile headlamp synthesized by high-frequency induction heated press (HFP) sintering. The CP prepared by an HFP method exhibits remarkable optical properties that are comparable to spark plasma sintering. The effects of post-treatment process for controlling residual pores, as well as sintering temperature, sintering pressure and heating rate for optimization of the HFP sintering method, were studied. The HFP sintering process can be widely used in ceramics and lighting fields because it is designed relatively low cost compared to other techniques and exhibits excellent productivity. [ABSTRACT FROM AUTHOR]

Published
2022
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40. Perceptual Evaluation of Noise Sources in a Chamber for Residential and Working Environment

Author

Jong-Kwan Ryu, Jeong-Ho Jung, Kyong-Ho Kim, Jin-Yong Jeon, and Moon-Jae Cho

Subjects
Engineering, Noise, Grey noise, Noise measurement, business.industry, Acoustics, Limit (music), Annoyance, Psychoacoustics, business, Set (psychology), Loudness
Abstract

This paper is to provide the basic way of a acoustical evaluation and efficient control noise by investigating the limits of perceptual loudness of living environment and by finding out any correlation between Physical characteristics of noise and psychoacoustic parameters. The limits of perceptual loudness were selected by the subjects in a chamber for residential and working environment. And the noise sources were analyzed to find out whether there is any correlation with Zwicker parameters and ACF factors. In this study especially, to set up the domestic evaluation grade about floor impact noise. we`d like to suggest the loudness Perception research result as fundamental resource for setting up the evaluation grade through the result that is based on annoyance. In the result of this research, upper limit of heavy-weight impact noise was L-60, and lower limit of it was L-50. On the other hand, upper limit of light-weight impact noise was L-70, and lower limit of it was L-55. It seemed that the loudness of noise from vacuum cleaner noise does not affect its perceived noisiness. Noises implicated In human such as floor walking noise and talking sound, are the most irritating noise in office environment.

Published
2002
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41. Effects of long-term bronchodilators in bronchiectasis patients with airflow limitation based on bronchodilator response at baseline

Author

Jeong,Ho Jung, Lee,Hyun, Carriere,Keumhee C, Kim,Jung Hoon, Han,Jin-Hyung, Shin,Beomsu, Jeong,Byeong-Ho, Koh,Won-Jung, Kwon,O Jung, Park,Hye Yun, Jeong,Ho Jung, Lee,Hyun, Carriere,Keumhee C, Kim,Jung Hoon, Han,Jin-Hyung, Shin,Beomsu, Jeong,Byeong-Ho, Koh,Won-Jung, Kwon,O Jung, and Park,Hye Yun

Abstract

Ho Jung Jeong,1,* Hyun Lee,1,* Keumhee C Carriere,2,3 Jung Hoon Kim,1 Jin-Hyung Han,1 Beomsu Shin,1 Byeong-Ho Jeong,1 Won-Jung Koh,1 O Jung Kwon,1 Hye Yun Park1 1Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University of Medicine, Seoul, South Korea; 2Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, AB, Canada; 3Biostatistics and Clinical Epidemiology Center, Samsung Medical Center, Seoul, South Korea *These authors contributed equally to this work Purpose: The association between positive bronchodilator response (BDR) at baseline and the effect of long-term bronchodilator therapy has not been well elucidated in patients with bronchiectasis. The aims of our study were to explore the association between positive BDR at baseline and lung-function improvement following long-term (3–12 months) bronchodilator therapy in bronchiectasis patients with airflow limitation. Materials and methods: The medical records of 166 patients with clinically stable bronchiectasis who underwent baseline pre- and postbronchodilator spirometry and repeated spirometry after 3–12 months of bronchodilator therapy were retrospectively reviewed. For analysis, patients were divided into two groups, responders and poor responders, based on achievement of at least 12% and 200 mL in forced expiratory volume in 1 second (FEV1) following bronchodilator therapy from baseline FEV1. Results: A total of 57 patients (34.3%) were responders. These patients were more likely to have positive BDR at baseline than poor responders (38.6% [22 of 57] vs 18.3% [20 of 109], P=0.004). This association persisted after adjustment for other confounding factors (adjusted odds ratio 2.298, P=0.034). However, we found FEV1 improved significantly following long-term bronchodilator therapy, even in patients without positive BDR at baseline (change in FEV1 130 mL, interquartile range -10 to 250 m

Published
2016

46. Mycobacterium abscessusLung Disease in a Patient with Kartagener Syndrome

Author

Kim, Jung Hoon, primary, Song, Won Jun, additional, Jun, Ji Eun, additional, Ryu, Duck Hyun, additional, Lee, Ji Eun, additional, Jeong, Ho Jung, additional, Jeong, Suk Hyeon, additional, Kang, Hyung Koo, additional, Kim, Jung Soo, additional, Lee, Hyun, additional, Chon, Hae Ri, additional, Jeon, Kyeongman, additional, Kim, Dohun, additional, Kim, Jhingook, additional, and Koh, Won-Jung, additional

Published
2014
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49. Effect of Na-doped Mo layer as a controllable sodium reservoir and diffusion barrier for flexible Cu(In,Ga)Se2solar cells

Author

Kim, Sung-Tae, Jeong, Ho-Jung, Kim, Ye-Chan, Bhatt, Vishwa, Kimar, Manjeet, Yun, Ju-Hyung, and Jang, Jae-Hyung

Abstract

To overcome the absence of sodium (Na) and to prevent undesired impurity diffusion from stainless steel (STS) substrates, a bi-layer molybdenum (Mo) structure consisting of a 1-μm-thick Mo and Na-doped Mo (Mo:Na) with variable thickness was utilized as the back contact layer in copper-indium-gallium-selenide (CIGS) solar cells. Na ions were supplied to the CIGS absorber layer from the Mo:Na layer, and the amount of Na ions was controlled by changing the thickness of Mo:Na layer. The Na doping to the CIGS layer is verified by the X-ray photoelectron spectroscopy (XPS) and the dynamic secondary ion mass spectroscopy (D-SIMS). The recombination process in the bulk CIGS and the CdS/CIGS junction has been analyzed by temperature dependent current density-voltage (J-V-T) measurement. The D-SIMS showed that the amount of Na ions in the CIGS layer grown on Mo/Mo:Na/STS is comparable with that in the conventional CIGS film deposited on Mo coated soda-lime glass. Moreover, the bi-layer Mo also acts as a diffusion barrier layer against the Fe atoms, which deteriorate the quality of CIGS. The higher content of Na ions and the lower content of Fe ions in the CIGS layer lowered the recombination activation energy, series resistance and ideality factor, leading to improved junction quality. As a result, the short circuit current density and power conversion efficiency of the CIGS on the Mo and 600-nm-thick Mo:Na were improved by 8.1 and 69.4%, respectively, compared with those of CIGS solar cells fabricated without a Mo:Na layer.

Published
2021
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50. Fabrication of LuAG:Ce 3+ Ceramic Phosphors Prepared with Nanophosphors Synthesized by a Sol-Gel-Combustion Method.

Author

Kwon SB, Choi SH, Yoo JH, Lee SY, Kim BY, Jeong HJ, Kim WH, Kim JP, Kang BK, Yoon DH, and Song YH

Abstract

The aim of this study was to investigate properties of ceramic phosphors fabricated using nano Lu 3 Al 5 O 12 :Ce 3+ phosphors produced with a sol-gel-combustion method. These nano Lu 3 Al 5 O 12 :Ce 3+ phosphors had a size of about 200 nm, leading to high density when fabricated as a ceramic phosphor. We manufactured ceramic phosphors through vacuum sintering. Alumina powder was added to improve properties. We mounted the manufactured ceramic phosphor in a high-power laser beam projector and drove it to determine its optical performance. Ceramic phosphor manufactured according to our route will have a significant impact on the laser-driven lighting industry.

Published
2022
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