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윤지현,오준협,김홍규,윤존도,Yun, Jihyeon,Oh, Junhyeob,Kim, Hongkyu,Yun, Jondo 한국재료학회 2016 한국재료학회지 Vol.26 No.5
Appropriate thermo-mechanical properties of nickel-based superalloys are achieved by heat treatment, which induces precipitation and solid solution hardening; thus, information on the temperature ranges of precipitation and dissolution of the precipitates is essential for the determination of the heat treatment condition. In this study, thermal analyses of nickel-based superalloys were performed by differential scanning calorimetry method under conditions of various heating rates of 5, 10, 20, or 40K/min in a temperature range of 298~1573K. Precipitation and dissolution temperatures were determined by measuring peak temperatures, constructing trend lines, and extrapolating those lines to the zero heating rate to find the exact temperature under isothermal condition. Determined temperatures for the precipitation reactions were 813, 952, and 1062K. Determined onset, peak, and offset temperatures of the first dissolution reaction were 1302, 1388, and 1406K, respectively, and those values of the second dissolution reaction were 1405, 1414, and 1462K. Determined solvus temperature was 1462K. The study showed that it was possible to use a simple method to obtain accurate phase transition temperatures under isothermal condition.
18~19세기 대형 불화에 사용된 회청(Smalt) 안료에 관한 연구
윤지현,김소진,김규호,YUN, Jihyeon,KIM, Sojin,KIM, Gyuho 국립문화재연구원 2022 헤리티지:역사와 과학 Vol.55 No.3
The purpose of this study is to analyze the chemical composition of smalt pigments used in 10 large Buddhist paintings in the Joseon Dynasty using energy dispersive X-ray spectroscopy, and to clarify the material and characteristics by observing morphological characteristics using polarized light microscopy and a scanning electron microscope. Through chemical composition analysis, the smalt of all 10 large Buddhist paintings is judged to be potash glass using SiO<sub>2</sub> as a former and K<sub>2</sub>O as a flux. In addition to the components related to cobalt ore used as a colorant, the paintings were found to contain high levels of As<sub>2</sub>O<sub>3</sub>, BaO, and PbO. The smalt particles did not have specific forms, and were blue in color, with various chromaticity. In some particles, conchoidal fracture, spherical bubbles, and impurities were observed. Through backscattered electron images, it was found that the smalt from paintings produced in the early 18th century AD had a high level of As, but the smalt from paintings produced from the mid-18th century AD onwards exhibited various contrast differences from particle to particle, and there was smalt with high levels of As, Ba, and Pb. Through the above results, the large Buddhist paintings in the Joseon Dynasty are divided into three smalt types. Type A is a type with high As<sub>2</sub>O<sub>3</sub>, type B is a type with high BaO, and type C is a type with high PbO. Looking at the three types of smalt pigments by the period of production, although some in-between periods were not detected, type A was confirmed to have been used from 1705 to 1808, while type B and type C were shown to have appeared in 1750 and used until 1808. This reveals that only one type of smalt was used until the early 18th century AD, and from the middle of the 18th century AD, several types of smalt were mixed and used in one large Buddhist painting. Studies such as this research are expected to provide insights into the characteristics of the smalt pigments used to produce large Buddhist paintings at the time.
과학적 창의성 관점에서 살펴본 영재교육종합 데이터베이스(GED)의 초등 과학영재교육 프로그램 특징 분석
윤지현 ( Yun Jihyeon ),강훈식 ( Kang Hunsik ) 한국초등과학교육학회 2021 초등과학교육 Vol.40 No.2
이 연구에서는 영재교육종합 데이터베이스(GED)에서 제공하는 초등 과학영재교육 프로그램 수상작을 과학적 창의성 관점에서 분석하였다. 이를 위해 해당 분석 기준을 개발한 뒤 우수 프로그램 55개에 포함된 840개의 탐구활동을 분석하였다. 연구 결과, 과학적 창의성 요소 5가지 중, ‘과학적 탐구기능’, ‘과학 지식 내용’, ‘창의적 사고’가 많이 포함되었다. 하지만 ‘문제해결력’과 ‘공통 요소’는 비교적 적게 포함되어 있었다. 통합의 측면에서는 2가지 요소의 통합과 3가지 요소의 통합이 자주 나타났으며, 통합이 없는 유형도 자주 나타났다. 4가지 요소의 통합이나 5가지 요소의 통합은 적게 나타났다. ‘과학 지식내용’, ‘과학적 탐구기능’, ‘창의적 사고’ 등이 다른 요소들과 함께 통합되는 빈도가 높았다. 그러나 ‘공통 요소’ 또는 ‘문제해결력’이 다른 요소와 통합되는 경우는 적게 나타났다. 이에 대한 교육적 시사점을 논하였다. This study analyzes the characteristic of elementary science-gifted education winner programs in Gifted Education Database (GED) focusing on scientific creativity. For this purpose, an analysis framework to analyze the programs was developed and a total of 840 inquiry activities from 55 winner programs were analyzed according to the analysis framework. The analysis of the results reveal that ‘scientific inquiry skill’ of the five scientific creativity components was most frequently included in the activities. ‘Scientific knowledge content’ and ‘creative thinking’ were also frequently included. However, ‘problem solving ability’ and ‘common factor’ were a little included. In the aspects of integration, the integrations between two or three components with five or eight types were frequently found. No integrations were also frequently included although less than the previous categories. The integrations among four with four types or five components were also slightly found. ‘Scientific knowledge content’, ‘scientific inquiry skills’, and ‘creative thinking’ with other components were more frequently found. However, the integrations of ‘common factor’ or ‘problem solving ability’ with the other components were less frequently found. Educational implications of these findings are discussed.
/오/-/우/ 합성모음 연속체에 대한 중국인 한국어 학습자의 청지각적 경계
윤지현(Yun, Jihyeon),김은경(Kim, EunKyung),성철재(Seong, Cheoljae) 한국음성학회 2015 말소리와 음성과학 Vol.7 No.4
The present study examines the auditory boundary between Korean /o/ and /u/ on a synthesized vowel continuum by Chinese learners of Korean language. Preceding researches reported that the Chinese learners have difficulty pronouncing Korean monophthongs /o/ and /u/. In this experiment, a nine-step continuum was resynthesized using Praat from a vowel token from a recording of a male announcer who produced it in isolated form. F1 and F2 were synchronously shifted in equal steps in qtone (quarter tone), while F3 and F4 values were held constant for the entire stimuli. A forced choice identification task was performed by the advanced learners who speak Mandarin Chinese as their native language. Their experiment data were compared to a Korean native group. ROC (Receiver Operating Characteristic) analysis and logistic regression were performed to estimate the perceptual boundary. The result indicated the learner group has a different auditory criterion on the continuum from the Korean native group. This suggests that more importance should be placed on hearing and listening training in order to acquire the phoneme categories of the two vowels.
F1/F2의 변화가 한국어 /오/, /우/ 모음의 지각판별에 미치는 영향
윤지현(Yun, Jihyeon),성철재(Seong, Cheoljae) 한국음성학회 2013 말소리와 음성과학 Vol.5 No.3
This study examined the perception of two Korean vowels using F1/F2 manipulated synthetic vowels. Previous studies indicated that there is an overlap between the acoustic spaces of Korean /o/ and /u/ in terms of the first two formants. A continuum of eleven synthetic vowels were used as stimuli. The experiment consisted of three tasks: an /o/ identification task (Yes-no), an /u/ identification task (Yes-no), and a forced choice identification task (/o/-/u/). ROC(Receiver Operating Characteristic) analysis and logistic regression were performed to calculate the boundary criterion of the two vowels along the stimulus continuum, and to predict the perceptual judgment on F1 and F2. The result indicated that the location between stimulus no.5 (F1 = 342Hz, F2 = 691Hz) and no.6 (F1 = 336Hz, F2 = 700Hz) was estimated as a perceptual boundary region between /o/ and /u/, while stimulus no.0 (F1=405Hz, F2=666Hz) and no.10 (F1=321Hz, F2=743Hz) were at opposite ends of the continuum. The influence of F2 was predominant over F1 on the perception of the vowel categories.