Nitrophenylene Polymers: Photodegradable Backbones via Ring-opening Metathesis Polymerization

Cheoljae Kim(김철재) 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2

A nitrophenylene polymer via ring-opening metathesis polymerization (ROMP) for the photo-mediated degradation has been developed. General degradable polymers contain hydrolysable functionalities such as esters, acetals, and vinyl ethers in their backbones, and their degradation requires an additional chemical step in presence of acid or base catalyst. Newly designed macrocyclic monomers bearing orthonitrobenzyl groups were successfully polymerized with Grubbs catalysts, and the resulting polymers were cleaved in presence of UV light without any chemical additive. Further studies are focused on the reversible polymerization and depolymerization of macrocyclic monomers in the manner of entropically-driven ROMP.

Metathesis Polymerizations for Degradable Polymers and Beyond

Cheoljae Kim(김철재 ) 한국고분자학회 2023 한국고분자학회 학술대회 연구논문 초록집 Vol.48 No.2

Gold(I)-catalyzed Cycloisomerization of the Mixed N,S-acetals Generated from Homopropargylic Amines; Mechanistic Implication for the Formal Alkyne Prins Reaction

Cheoljae Kim,Wontaeck Lim,Young Ho Rhee 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.6

Formal Alkyne Aza-Prins Cyclization: Gold(I)-Catalyzed Cycloisomerization of Mixed N,O-Acetals Generated from Homopropargylic Amines to Highly Substituted Piperidines

Kim, Cheoljae,Bae, Hyo Jin,Lee, Ji Hyung,Jeong, Wook,Kim, Haejin,Sampath, Vasu,Rhee, Young Ho American Chemical Society 2009 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.131 No.41

<P>A new gold(I)-catalyzed cycloisomerization to access highly substituted piperidines has been developed. By combining a conceptually new way of generating iminium ions using cationic gold(I) complexes and an efficient cyclization reaction that can minimize a potentially competing aza-Cope rearrangement, the proposed reaction successfully circumvents a long-standing problem in the classical aza-Prins reaction. Synthetic utility of the catalytic reaction was demonstrated by a synthesis of optically active 2-alkyl-piperidin-4-one.</P>

Synthesis of the Tricyclic Core in Stemonamine Alkaloids via One-Pot Gold(I)-Catalyzed Cyclization and Schmidt Rearrangement: Formal Synthesis of (±)-Stemonamine

Kim, Cheoljae,Kang, Soyeong,Rhee, Young Ho American Chemical Society 2014 Journal of organic chemistry Vol.79 No.22

<P>An efficient synthesis of the tricyclic cyclopenta[1,2-<I>b</I>]pyrrolo[1,2-<I>a</I>]azepine nucleus of stemonamine alkaloids is reported. The key reaction utilizes a one-pot gold(I)-catalyzed cyclization and SnCl<SUB>4</SUB>-mediated Schmidt rearrangement. Notably, the phosphine ligand had a crucial effect on the gold(I)-catalyzed cyclization. As an application of this new methodology, the formal synthesis of (±)-stemonamine has been accomplished.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/joceah/2014/joceah.2014.79.issue-22/jo502103p/production/images/medium/jo-2014-02103p_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jo502103p'>ACS Electronic Supporting Info</A></P>

소형 2륜 자동차의 머플러 내부 유동에 관한 수치해석

이철재(Cheoljae Lee),이중섭(Chungseub Yi),배태열(Taeyeol Bae),심규진(Kyujin Shim),정효민(Hyomin Jeong),정한식(Hanshik Chung) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

This study represents numerical study on the thermal and fluid flow characteristics of exhaust gas in a motorcycle muffler. The reference engine was used 124㏄ small displacement. Numerical analysis with computational fluid dynamics(CFD) was carried out to investigate the exhaust gas that flow into a motorcycle muffler. The STAR-CD S/W used to three dimensional steady state and transient CFD analysis in a muffler. The Navier-Stokes Equation is Solved with SAMPLE and PISO method in a gener cartesian coordinates system. Numerical result shows that baffle of chamber which is inflow of exhaust gas can serious problem having thermal stress cause by high temperature exhaust gas. And accumulation of pressure estimate inevitable. So, accumulation of pressure has to remove how make a hole or grooves in the baffle connect with different chamber.

과소비성(Hyponasality) 집단의 음향 특성과 분류 변인

김난숙(Nansook Kim),성철재(Cheoljae Seong) 사단법인 한국언어학회 2017 언어학 Vol.0 No.78

68 children (4;4~9;11, 35 Adenotonsillar Hypertrophy vs. 33 Allergic Rhinitis) read ‘mommy’ sentence comprised of pure nasal sounds and vowels in order to find some appropriate acoustic correlates to discriminate two groups. Recordings were carried out by both Nasometer (KAY, USA) and Tascam DR05 (TEAC, USA). The data, evaluated by perception test using ExperimentMFC, were acoustically analysed and statistically tested by both SPSS and R, respectively in specific areas. Hyponasality seems to strongly have to do with Adenotonsillar Hypertrophy and Allergic Rhinitis. Traditionally the nasalance score achieved from Nasometer has been used for judging the degree of nasality concern. Despite Nasometer has been popularly used for the measurement of nasalance, there has been shortcomings in such a way that the apparatus has been quite expensive and given some discomfort of wearing headset. In this respect, this paper seeks to find whether the nasalance score is statistically meaningful in discriminating two groups, if not, go further to mine proper acoustic variables comparable to the nasalance score. Perception test using ExperimentMFC (Praat) showed significant intra- and inter-rater reliability. Nasalance score did not show significant difference between two groups (p=.51). When considered RNR (rhamonics to nois ratio), L/H ratio (low to high energy ratio), and two variables (PC1 and PC2) diminished from 18 normalized band energies by PCA (principal component analysis), two groups were significantly differentiated (p〈.05). When tested by the logistic regression model trained by 70% of the entire data, the 30% test data showed 81% classification accuracy. Together with perceptional judgment, these new set of acoustic variables could contribute to discern hyponasality of two groups.

컴퓨터 기반 음소인식 훈련을 통한 읽기장애 치료 프로그램 개발

최은아(Eunah Choi),성철재(Cheoljae Seong) 사단법인 한국언어학회 2020 언어학 Vol.0 No.88

This study aims to improve phoneme recognition rate and reading fluency by developing and applying a computer-based phoneme recognition program for children with Dyslexia. The newly developed program for Dyslexia treatment includes a sweep-tone listening training program which having stimuli of varied frequency and duration, and a speech listening training program providing meaningless syllables, words, and sentences. Therefore, it can be said that this could be a program that has reflected all the advantages of the existing computer-based treatment programs and the programs that train reading through pictures or reading materials. In order to verify the effectiveness, this newly developed program was applied to 10 children with Dyslexia who are in the first to third grades of elementary school, twice a week for 6 months, and 40 minutes in each session. We compared the difference between before and after the application of this program by conducting tests of word reading fluency, decoding (meaning words, meaningless words), phoneme recognition (deletion, compounding), and quick naming (numbers, letters) all of which are part of Korean reading test battery. Word reading fluency and decoding (meaning words, meaningless words), phoneme recognition (compounding) scores in all 10 patients, phoneme recognition (deletion) and quick naming (numbers, letters) scores in 8 out of 10 patients were improved before and after treatment, and the difference was statistically significant.

기식성 음성 장애 환자들의 음향학적 특성과 분류 변인—결절, 용종환자를 중심으로—

이인애(Inae Lee),성철재(Cheoljae Seong) 사단법인 한국언어학회 2020 언어학 Vol.0 No.88

Incomplete phonation of vocal cords seems to cause breathy voice. Vocal nodules and vocal polyps are typical functional voice disorders. This study aimed to find the acoustic parameters useful for discriminating these two groups. In this study, 56 subjects diagnosed with speech disorders (27 vocal nodules, 29 vocal polyps) were recruited, and the MDVP (Multidimensional Voice Program) played within CSL (Computerized Speech Lab. Kay Elemetrics Co., Model No. 4300) was used for recording sustained vowel /a/. Praat (ver. 6.0.48) was used for acoustic analysis. Mann-Whitney U test showed that the MDVP parameters (excluding frequency-relevant variables) had no effect on discriminating two groups (vocal nodules vs. vocal polyps). However, when it comes to the cepstral parameters measured by Praat, there was statistically significant differences between groups: RNR (p<.o5), cepsPeak (p<.o5), quefrency (p<.o5), and CPP(p) <.o5) and cepslntercept (p<.o5). With respect to the relative rank of variable importance, quefrency has the highest rank, and rnr and CPP followed in order. As a result of classification by the logistic regression model using these three variables, the overall classification accuracy for the training data was 81.4%, 94.4% for the vocal nodule group, and 68.4% for the vocal polyp group. In test data, nodules were 100% and vocal fold polyps were 30%. Although the overall classification accuracy was 65%, the classification accuracy of the polyps was too low, making it difficult to trust the model. In the case of the svm (support vector machine) model, the overall classification ratio of the training data was 94.6% (nodules (17/18)=94.4%, polyps (18/19)=94.7%). The overall classification accuracy of the test data was found to be 68.4% (nodule (6/9) = 66.7%. Polyp (7/10) = 70%). It was found that, therefore, the performance of the svm was higher and more stable.

읽기장애아동과 일반아동의 통사적 다양성에 따른 운율 특성 비교

박성숙(Sungsook Park),성철재(Cheoljae Seong) 한국음성학회 2021 말소리와 음성과학 Vol.13 No.4

읽기와 관련된 운율은 내용의 전체적인 맥락에 연결되어 독자가 전달하고자 하는 의미를 자연스럽게 표현할 수 있도록 음도, 강도, 발화속도 등의 변화로 나타난다. 읽기장애아동은 자연스러운 운율을 사용한 읽기에 어려움이 있어 표현력 있게 정보를 전달하지 못하는 경향이 있다. 이와 관련하여 본 연구는 문장 유형에 따른 읽기 과제를 통하여 읽기장애아동 집단과 일반아동 집단 간의 운율 특성 차이를 규명하였다. 초등학교 3-6학년 읽기장애아동 15명, 일반아동 15명을 대상으로 통사적으로 다양한 문장 유형(단문, 의도, 가정/조건, 관형절 내포문)에 따른 읽기 과제를 실시하였다. 읽기장애아동은 일반아동에 비해 음도 범위가 넓었으며 읽기 속도와 조음 속도가 느렸다. 또한 휴지 빈도가 높았으며 전체 휴지 지속시간도 길었다. 읽기장애아동은 문미 억양구와 문장 내 어절 단위 음도 기울기에서 일반아동에 비해 기울기 값이 컸으며 이상의 내용은 모두 통계적으로 유의하였다. 결과적으로 문장 유형에 따른 읽기 과제에서 읽기장애아동은 일반아동에 비해 자연스럽고 표현력 있는 읽기에 어려움을 보였다. 본 연구를 통해 읽기장애아동의 운율 특성을 파악하였고, 효과적인 중재를 위한 접근 방법의 필요성을 제시했다. Proper prosody in reading allows the reader to naturally convey the meaning, which manifests as changes in pitch, loudness, and speech rate. Children with reading disability face difficulty in delivering information due to poor prosody. This study identified the difference in prosodic features between children with reading disabilities and nondisabled children through means of reading tasks. Reading tasks, according to sentence types (short sentences, assumptions/conditions, intentions, relative-clause), were recorded by 15 children studying in the 3rd to 6th grade in elementary school. Children with reading disability had a statistically significant wider range of pitch, slower speech rate, more frequent usage of pauses, longer total pause duration, and steeper pitch slope than nondisabled one in sentence-final and -medial words. Children with reading disability, therefore, exhibited a less natural and expressive reading than nondisabled children. Through this study, the characteristics of prosody observed in children with reading disability were identified and the need for an approach for effective intervention was also suggested.