Large Electrical Resistance Variation at Low Temperature in Transition Metal-Doped Ge Single Crystals

Choi, Jiyoun,Choi, Jeongyong,Choi, Sungyoul,Kim, Jongphil,Cho, Sunglae Japan Institute of Metals 2015 MATERIALS TRANSACTIONS Vol.56 No.9

<P> We have grown un-doped and transition metal (V, Cr, Mn, Fe, Co, Ni, Cu)-doped Ge bulk single crystals using the vertical gradient solidification method. The electrical resistivities of V, Ni, Co, and Fe-doped Ge crystals significantly increased, 10<SUP>4</SUP>∼10<SUP>5</SUP> times, between 5 and 100 K, which were 100 times larger than that of the commercial Ge resistance temperature device (RTD). The large variation of electrical resistance at low temperature arises from decreased carrier density and mobility at low temperature. The mobility reduction at low temperature might be caused by ionized impurity scattering. </P>

Magnetoresistances and Hall effects of Ge₁-xVx and Ge₁-xCox

Jiyoun Choi,Sungyoul Choi,Jeongyong Choi,Soon Cheol Hong,Sunglae Cho,Yongsup Park,Hyun-Min Park 한국자기학회 2003 한국자기학회 학술연구발표회 논문개요집 Vol.13 No.2

Magnetoresistance and Hall coefficient in VxGe₁-x single crystal

Jiyoun Choi,Sungyoul Choi,Jeongyong Choi,Soon Cheol Hong,Sunglae Cho,Yongsup Park,Gu-Won Lee,Hyun-Min Park,Y. C. Kim 한국자기학회 2003 한국자기학회 학술연구발표회 논문개요집 Vol.13 No.1

Growth and magnetic properties of MnBi thin films

Jiyoun Choi,Sungyoul Choi,Jeongyong Choi,Soon Cheol Hong,Sunglae Cho,Yongsup Park,Kyu-Won Lee,Hyun-Min Park 한국자기학회 2004 한국자기학회 학술연구발표회 논문개요집 Vol.14 No.1

대학생의 디지털 글쓰기 인식 조사 분석

최지연(Jiyoun Choi Jiyoun) 학습자중심교과교육학회 2023 학습자중심교과교육연구 Vol.23 No.2

목적 본 연구는 최근 디지털 시대 변화에 따른 대학생의 디지털 글쓰기 인식을 성별, 전공 계열별로 분석해보고 디지털 쓰기수행에 영향을 미치는 요인을 분석하여 디지털 쓰기 교육의 계획 및 실천에 시사점을 제공하고자 하였다. 방법 이를 위하여 부산 소재 대학교 재학생 1학년 379명을 대상으로 디지털 글쓰기 인식 설문조사(9개 하위 구성요소, 20문항)를 실시하였으며 SPSS 25.0 버전을 이용해 통계적으로 분석하였다. 성별과 계열 간 차이를 알아보기 위해서 각각 독립표본 t검정, 일원배치 분산분석(one-way Anova)을 실시하였으며, 디지털 쓰기수행에 미치는 요인을 알아보기 위해 상관분석, 다중 회귀분석(multiple regression analysis)을 실시하였다. 결과 본 연구 결과는 다음과 같다. 첫째, 기술통계에서는 디지털 쓰기가치와 쓰기불안의 평균 점수가 가장 높았다. 둘째, 디지털 글쓰기 인식에 대한 성별 차이는 디지털 쓰기불안만이 통계적으로 유의하였으며, 남학생보다 여학생의 평균 점수가 높았다. 셋째, 디지털 글쓰기 인식에 대한 계열 차이를 문항별로 분석한 결과 디지털 쓰기수행과 디지털 쓰기인정이 통계적으로 유의한 결과를 보였으며 자연·공학계열보다 인문·사회계열의 평균 점수가 더 높았다. 마지막으로 디지털 쓰기수행에 영향을 미치는 요인을 분석한 결과 디지털 쓰기효능감, 독자고려, 디지털 쓰기가치, 디지털 쓰기윤리 순으로 나타났다. 결론 디지털 기기와 기술의 영향으로 문식환경이 변함에 따라 전통적 글쓰기와 차이가 발생함을 고려하여 디지털 글쓰기의 특성, 인식 등의 분석을 통해 디지털 글쓰기 교육의 시사점을 논의하였다. 본 연구 결과를 통해 대학생을 대상으로 한 디지털 쓰기윤리 교육의 필요성, 이공계열 대학생의 쓰기 수행 및 쓰기인식 강화 방안이 필요함을 알 수 있었으며 디지털 쓰기수행에 가장 큰 영향을 미치는 것은 디지털 쓰기효능감으로 그간의 선행연구 결과와 일치하였다. Objectives The purpose of this study was to analyze university students' perception of digital writing by gender and major, and also to analyze the factors that influence these differences on digital writing performance. Methods A digital writing recognition survey (9 sub-components, 20 questions) was conducted for 379 first-year students at a university in Busan. Independent sample t-test, one-way ANOVA, correlation analysis, simple linear regression, and multiple regression analysis using SPSS 25.0 version was performed. Results First, in descriptive statistics, the average score of digital writing value and writing anxiety was the highest. Second, as for the gender difference in digital writing recognition, only digital writing anxiety was statistically significant, and the average score of female students was higher than male students. Third, when analyzing the difference in the series of digital writing recognition by item, digital writing performance and digital writing recognition showed statistically significant results, and the average score of humanities and social sciences was higher than that of natural sciences and engineering. Finally, as a result of analyzing the factors affecting digital writing performance, it was found in the order of digital writing efficacy, reader consideration, digital writing value, and digital writing ethics. Conclusions In this study, it was emphasized that it should be considered that there is a difference from traditional writing as the literacy environment changes due to the influence of digital devices and technology. The implications of digital writing education were presented through the analysis of characteristics and perceptions of digital writing. Through the results of this study, it was confirmed that digital writing ethics education for university students is necessary and that it is necessary to strengthen writing performance and writing awareness among science and engineering college students. The biggest influence on digital writing performance was digital writing efficacy, which was consistent with the results of previous studies.

Dutch Listeners’ Perception of Korean Stop Consonants

Choi, Jiyoun(최지연) 한국음성학회 2015 말소리와 음성과학 Vol.7 No.1

We explored Dutch listeners’ perception of Korean three-way contrast of fortis, lenis, and aspirated stops. The three Korean stops are all voiceless word-initially, whereas Dutch distinguishes between voiced and voiceless stops, so Korean voiceless stops were expected to be difficult for the Dutch listeners. Among the three Korean stops, fortis stops are phonetically most similar to Dutch voiceless stops, thus they were expected to be the easiest to distinguish for the Dutch listeners. Dutch and Korean listeners carried out a discrimination task using three crucial comparisons, i.e., fortis-lenis, fortis-aspirated, and lenis-aspirated stops. Results showed that discrimination between lenis and aspirated stops was the most difficult among the three comparisons for both Dutch and Korean listeners. As expected, Dutch listeners discriminated fortis from the other stops relatively accurately. It seems likely that Dutch listeners relied heavily on VOT but less on F0 when discriminating between the three Korean stops.

How does focus-induced prominence modulate phonetic realizations for Korean word-medial stops?

Jiyoun Choi 한국음성학회 2020 말소리와 음성과학 Vol.12 No.4

Previous research has indicated that the patterns of phonetic modulations induced by prominence are not consistent across languages but are conditioned by sound systems specific to a given language. Most studies examining the prominence effects in Korean have been restricted to segments in word-initial and phrase-initial positions. The present study, thus, set out to explore the prominence effects for Korean stop consonants in word-medial intervocalic positions. A total of 16 speakers of Seoul Korean (8 males, 8 females) produced word-medial intervocalic lenis and aspirated stops with and without prominence. The prominence was induced by contrast focus on the phonation-type contrast, that is, lenis vs. aspirated stops. Our results showed that F0 of vowels following both lenis and aspirated stops became higher when the target stops received focus than when they did not, whereas voice onset time (VOT) and voicing during stop closure for both lenis and aspirated stops did not differ between the focus and no-focus conditions. The findings add to our understanding of diverse patterns of prominence-induced strengthening on the acoustic realizations of segments.

Early phonology revealed by international adoptees' birth language retention

Choi, Jiyoun,Broersma, Mirjam,Cutler, Anne National Academy of Sciences 2017 Proceedings of the National Academy of Sciences Vol.114 No.28

<P>Until at least 6 mo of age, infants show good discrimination for familiar phonetic contrasts (i.e., those heard in the environmental language) and contrasts that are unfamiliar. Adult-like discrimination (significantly worse for nonnative than for native contrasts) appears only later, by 9-10 mo. This has been interpreted as indicating that infants have no knowledge of phonology until vocabulary development begins, after 6 mo of age. Recently, however, word recognition has been observed before age 6 mo, apparently decoupling the vocabulary and phonology acquisition processes. Here we show that phonological acquisition is also in progress before 6 mo of age. The evidence comes from retention of birth-language knowledge in international adoptees. In the largest ever such study, we recruited 29 adult Dutch speakers who had been adopted from Korea when young and had no conscious knowledge of Korean language at all. Half were adopted at age 3-5 mo (before native-specific discrimination develops) and half at 17 mo or older (after word learning has begun). In a short intensive training program, we observe that adoptees (compared with 29 matched controls) more rapidly learn tripartite Korean consonant distinctions without counterparts in their later-acquired Dutch, suggesting that the adoptees retained phonological knowledge about the Korean distinction. The advantage is equivalent for the younger-adopted and the older-adopted groups, and both groups not only acquire the tripartite distinction for the trained consonants but also generalize it to untrained consonants. Although infants younger than 6 mo can still discriminate unfamiliar phonetic distinctions, this finding indicates that native-language phonological knowledge is nonetheless being acquired at that age.</P>

MBE Growth and Magnetic Properties of GaSb/MnSb Superlattices

Jiyoun Choi,최정용,Sungyoul Choi,홍순철,조성래,M. H. Sohn,박용섭,Kyu-Won Lee,박현민,송종현,J. B. Ketterson 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.3

We have grown a 37-period GaSb(25 )/MnSb(2 A) superlattice on GaAs(001) substrate with1000 A GaSb buer layer by solid-source molecular beam epitaxy. We have observed that the streaky RHEED patterns of GaSb and MnSb were maintained even when the growth was fnished in 37 periods, indicating 2-dimensional layer-by-layer growth of MnSb on GaSb or vice versa. Interestingly, a GaSb(25A)/MnSb(2A) superlattice showed ferromagnetic ordering up to above 400 K, with a coercive eld of 380 Oe at 10 K.

The Role of ¹⁸ F-FDG PET/CT in Assessing Therapy Response in Cervix Cancer after Concurrent Chemoradiation Therapy

Choi, Jiyoun,Kim, Hyun Jeong,Jeong, Yong Hyu,Lee, Jae-Hoon,Cho, Arthur,Yun, Mijin,Lee, Jong Doo,Kim, Yong Bae,Kim, Young Tae,Kang, Won Jun 大韓核醫學會 2014 핵의학 분자영상 Vol.48 No.2

<P><B>Purpose</B></P><P>To determine whether persisting cervical fluorodeoxyglucose (FDG) uptake after concurrent chemoradiotherapy (CCRT) for cervical cancer can reflect residual malignancy.</P><P><B>Methods</B></P><P>F-FDG PET/CT was performed before and after CCRT in 136 patients with cervical cancer. The maximum and mean standardized uptake values (SUVmax and SUVmean) were recorded from PET/CT scans performed pre- and post-treatment. SUVs were correlated with treatment response after CCRT. Final treatment response was determined by MRI and further follow-up PET/CT. One hundred four of 136 patients underwent pelvic MRI, and 32 of 136 patients underwent further follow-up PET/CT. Patients were classified into two categories: patients with residual tumor or patients without residual tumor (complete responder). Pre- and post-treatment serum squamous cell carcinoma antigen (SCC) levels were also recorded for comparison. The optimal cutoff value of SUVmax for predicting residual cervical tumor was determined using receiver-operating characteristic (ROC) analysis.</P><P><B>Results</B></P><P>Of 136 patients, 124 showed complete response on further follow-up studies and 12 were confirmed to have residual tumor. The post-treatment SUVmax and pre-/post-treatment SUVmean of complete responders were significantly lower than those of patients with residual tumor: 2.5 ± 0.8 and 7.2 ± 4.2/1.9 ± 0.7 for complete responders and 5.7 ± 2.6 and 12.8 ± 6.9/3.7 ± 0.7 for patients with residual tumor (<I>p</I> < 0.05). The pre-treatment SUVmax and pre-/post-treatment serum SCC levels of the complete responders tended to be lower than those of patients with residual tumor, but this did not have statistical significance. Using ROC analysis, an optimal cutoff SUVmax of 4.0 on the post-treatment PET/CT yielded a sensitivity, specificity, positive predictive value, and negative predictive value of 92 %, 94 %, 61 %, and 99 %, respectively (<I>p</I> < 0.001).</P><P><B>Conclusions</B></P><P>Persistent cervical FDG uptake in<SUP>18</SUP>F-FDG PET/CT after CCRT for cervical cancer may be caused by residual tumor or post-therapy inflammation. A higher cutoff SUVmax than conventional criteria for cervical cancer in post-CCRT PET/CT might help to detect residual tumor.</P>