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Park, Taehoon,Lee, Kang-Hyun,Yun, Gun Jin Techno-Press 2021 Advances in aircraft and spacecraft science Vol.8 No.3
This study presents an efficient computational methodology to perform ablative thermal response analysis of carbon/phenolic composites by introducing a novel dual-domain technique for heat transfer and gas diffusion physics. Phenomena such as in-depth heat transfer, material decomposition (i.e. pyrolysis), in-depth gas diffusion, and surface recession required for ablation analysis of carbon/phenolic composites are simulated. The proposed method is verified with reference simulation test data from Ablation Workshop for a one-dimensional model under four different combinations with surface heat flux, temperature, pressure boundary conditions, and surface recession conditions verified. A two-dimensional ablation problem was also solved, showing its scalability. Temperatures, recession depth, depth of boundaries between layers, the mass flux of char, and pyrolysis gas are obtained and compared with the reference for all cases.
Computation of Hypersonic Inviscid Flow of low dendsity
Park, Taehoon,Kim, Pok-Son 국민대학교 2003 기초과학연구소 논문집 Vol.22 No.-
We consider two dimensional steady state inviscid flow of air around flying objects including chemical reactions. We present the result of numerical computations of nonequilibrium hypersonic inviscid flow of low density. The model problem is based on the Euler equations and a chemical reaction model accounting for the finite rate reactions. We obtained detailed detailed description of flow properties near the shock and body.
Intracranial Metaplastic Meningioma : Clinical and Radiological Characteristics of 11 Cases
Taehoon Kim,Jin Wook Kim,So Young Ji,Ho Kang,Kyung-Min Kim,Yong Hwy Kim,Chul-Kee Park,Seung Hong Choi,Sung-Hye Park 대한신경외과학회 2020 Journal of Korean neurosurgical society Vol.63 No.5
Objective : Metaplastic meningioma is an extremely rare subtype of World Health Organization (WHO) grade I meningioma. It has distinctive histological subtypes according to its own mesenchymal components. Owing to its scarcity, clinical or radiological features of a metaplastic meningioma are poorly described. Methods : Between 2004 and 2018, we analyzed total 1814 cases surgically proven meningioma for 15 years. Among them, metaplastic meningioma was diagnosed in 11 cases. Magnetic resonance images were taken for all patients, and computed tomography scan was taken for 10 patients. Results : WHO grade I meningiomas were 1376 cases (75.9%), 354 cases (19.5%) in WHO grade II, and 84 cases (4.6%) in WHO grade III meningiomas. Metaplastic meningioma was 11 cases as 0.8% of WHO grade I meningioma and 0.6% of entire meningiomas for 15 years. Among the entire 11 metaplastic meningiomas, five tumors (45%) were diagnosed as a lipomatous subtype with rich fat components, four (36%) as an osseous subtype with extensive bone formation and two (18%) as a xanthomatous subtype. There was no cartilaginous subtype metaplastic meningioma in our study. Lipomatous and osseous metaplastic meningioma have peculiar radiological characteristics according to mesenchymal components. Conclusion : We investigated a rare metaplastic meningioma subtype based on our 15-year surgical experience with meningiomas. Further investigation will be necessary for the clear clarification of tumor nature of this rare tumor.
PARK, TAEHOON,LEE, CHAE Y. 한국경영과학회 1994 韓國經營科學會誌 Vol.19 No.3
A fixed k-coloring problem is introduce and dealt with by efficient heuristic algorithms. It is shown that the problem can be transformed into the graph partitioning problem. Initial coloring and improving methods are proposed for problems with and without the size restriction. Algorithms Move, Lee and OEE are developed by modifying the Kernighan-Lin's two way uniform partitioning procedure. The use of global information in the selection of the node and the color set made the proposed algorithms superior to the existing method. The computational result also shows that the superiority does not sacrifice the time demand of the proposed algorithms.
Nonequilibrium Hypersonic Inviscid Flow of High Density around Flying Bodies
Park, Taehoon,Kim, Pok-Son 국민대학교 2002 기초과학연구소 논문집 Vol.21 No.-
We consider two dimensional steady state inviscid flow of air around bodies including chemical reactions. We present numerical results of nonequilibrium hypersonic inviscid flow of high density. The model problem is based on the Euler equations and a chemical reaction model accounting for the finite rate reactions. We obtained detailed detailed description of flow properties near the shock and body.
Highly Reliable Amorphous In-Ga-Zn-O Thin-Film Transistors Through the Addition of Nitrogen Doping
Park, Kyung,Kim, Jong Heon,Sung, Taehoon,Park, Hyun-Woo,Baeck, Ju-Heyuck,Bae, Jonguk,Park, Kwon-Shik,Yoon, Sooyoung,Kang, Inbyeong,Chung, Kwun-Bum,Kim, Hyun-Suk,Kwon, Jang-Yeon Institute of Electrical and Electronics Engineers 2019 IEEE transactions on electron devices Vol.66 No.1
<P>The electrical properties and the device reliability under positive/negative bias stress with/without illumination regarding amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) are evaluated as a function of the nitrogen partial pressure in the sputter deposition. Interestingly, it is easy to control the carrier concentration through the incorporation of nitrogen into IGZO, whereby the device performance is changed. In addition, when nitrogen is introduced during the conventional IGZO deposition, the device reliability of N-doped IGZO TFTs is considerably improved compared to that of undoped-IGZO TFTs due to the reduced amount of defects. It is also interesting that such an improvement of the device reliability regarding IGZO is easily obtainable through the simple addition of nitrogen to the conventional deposition process. It is, therefore, strongly believed that this simple nitrogen-doping process for IGZO is very effective regarding the achievement of highly durable devices, and it can be immediately applied to the current mass production of the high-performance displays for which the oxide semiconductor is used.</P>
Park, Taehoon,Oh, Ju-Hee,Lee, Joo Hyun,Park, Sang,Jang, Young,Lee, Young-Joo Georg Thieme Verlag KG 2017 Planta medica Vol.83 No.17
<B>Abstract</B><P>(S)-Allyl-l-cysteine is the major bioactive compound in garlic. (S)-Allyl-l-cysteine is metabolized to (S)-allyl-l-cysteine sulfoxide, N-acetyl-(S)-allyl-l-cysteine, and N-acetyl-(S)-allyl-l-cysteine sulfoxide after oral administration. An accurate LC-MS/MS method was developed and validated for the simultaneous quantification of (S)-allyl-l-cysteine and its metabolites in rat plasma, and the feasibility of using it in pharmacokinetic studies was tested. The analytes were quantified by multiple reaction monitoring using an atmospheric pressure ionization mass spectrometer. Because significant quantitative interference was observed between (S)-allyl-l-cysteine and N-acetyl-(S)-allyl-l-cysteine as a result of the decomposition of N-acetyl-(S)-allyl-l-cysteine at the detector source, chromatographic separation was required to discriminate (S)-allyl-l-cysteine and its metabolites on a reversed-phase C18 analytical column with a gradient mobile phase consisting of 0.1% formic acid and acetonitrile. The calibration curves of (S)-allyl-l-cysteine, (S)-allyl-l-cysteine sulfoxide, N-acetyl-(S)-allyl-l-cysteine, and N-acetyl-(S)-allyl-l-cysteine sulfoxide were linear over each concentration range, and the lower limits of quantification were 0.1 µg/mL [(S)-allyl-l-cysteine and N-acetyl-(S)-allyl-l-cysteine] and 0.25 µg/mL [(S)-allyl-l-cysteine sulfoxide and N-acetyl-(S)-allyl-l-cysteine sulfoxide]. Acceptable intraday and inter-day precisions and accuracies were obtained at three concentration levels. The method satisfied the regulatory requirements for matrix effects, recovery, and stability. The validated LC-MS/MS method was successfully used to determine the concentration of (S)-allyl-l-cysteine and its metabolites in rat plasma samples after the administration of (S)-allyl-l-cysteine or aged garlic extract.</P>
Park, Soowon,Kim, Taehoon,Shin, Seong A,Kim, Yu Kyeong,Sohn, Bo Kyung,Park, Hyeon-Ju,Youn, Jung-Hae,Lee, Jun-Young Frontiers Media S.A. 2017 FRONTIERS IN AGING NEUROSCIENCE Vol.9 No.-
<P><B>Background:</B> Facial emotion recognition (FER) is impaired in individuals with frontotemporal dementia (FTD) and Alzheimer’s disease (AD) when compared to healthy older adults. Since deficits in emotion recognition are closely related to caregiver burden or social interactions, researchers have fundamental interest in FER performance in patients with dementia.</P><P><B>Purpose:</B> The purpose of this study was to identify the performance profiles of six facial emotions (i.e., fear, anger, disgust, sadness, surprise, and happiness) and neutral faces measured among Korean healthy control (HCs), and those with mild cognitive impairment (MCI), AD, and FTD. Additionally, the neuroanatomical correlates of facial emotions were investigated.</P><P><B>Methods:</B> A total of 110 (33 HC, 32 MCI, 32 AD, 13 FTD) older adult participants were recruited from two different medical centers in metropolitan areas of South Korea. These individuals underwent an FER test that was used to assess the recognition of emotions or absence of emotion (neutral) in 35 facial stimuli. Repeated measures two-way analyses of variance were used to examine the distinct profiles of emotional recognition among the four groups. We also performed brain imaging and voxel-based morphometry (VBM) on the participants to examine the associations between FER scores and gray matter volume.</P><P><B>Results:</B> The mean score of negative emotion recognition (i.e., fear, anger, disgust, and sadness) clearly discriminated FTD participants from individuals with MCI and AD and HC [<I>F</I>(3,106) = 10.829, <I>p</I> < 0.001, η<SUP>2</SUP> = 0.235], whereas the mean score of positive emotion recognition (i.e., surprise and happiness) did not. A VBM analysis showed negative emotions were correlated with gray matter volume of anterior temporal regions, whereas positive emotions were related to gray matter volume of fronto-parietal regions.</P><P><B>Conclusion:</B> Impairment of negative FER in patients with FTD is cross-cultural. The discrete neural correlates of FER indicate that emotional recognition processing is a multi-modal system in the brain. Focusing on the negative emotion recognition is a more effective way to discriminate healthy aging, MCI, and AD from FTD in older Korean adults.</P>