CFD를 이용한 FCEV용 Turbo Blower의 Impeller 최적 설계 연구

정우열(Wooyoul Jung),임차유(Chayou Lim),조경석(Kyungseok Cho),박창호(Changho Park),이창하(Changha Lee) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5

FCEV needs to cathode air to generate electricity through the fuel cell stack. To supply air to the feul cell stack is required high pressure ratio and the turbo blower of centrifugal compressor type is used. The performance of centrifugal compressor is most affected on impeller design. Thus this study shows the method of optimizing impeller shape for several design parameters using CFD and Taguchi method. Using CFD gives advantages to reduce cost and time making proto sample and to help understand flow mechanism over the impeller and turbo blower.

Fresnelet 변환 기반의 디지털 홀로그램 압축 기법

김우열(Kim, Wooyoul),이윤혁(Lee, Yoonhyuk),서영호(Seo, Youngho),김동욱(Kim, Dongwook) 한국방송·미디어공학회 2013 한국방송공학회 학술발표대회 논문집 Vol.2013 No.6

Case Report : Nontuberculous Mycobacterial Lung Disease Caused by Mycobacterium chelonae: A Case Report

( Yousang Ko ),( Wooyoul Kim ),( Beom Su Shin ),( Hongseok Yoo ),( Jung Seop Eom ),( Ji Hyun Lee ),( Byung Woo Jhun ),( Su Young Kim ),( Go Eun Choi ),( Sung Jae Shin ),( Won Jung Koh ) 대한결핵 및 호흡기학회 2013 Tuberculosis and Respiratory Diseases Vol.74 No.4

Mycobacterium chelonae lung disease is very rare. We report a case of lung disease caused by M. chelonae in a previously healthy woman. A 69-year-old woman was referred to our hospital because of hemoptysis. A computed tomography (CT) scan of the chest revealed bronchiolitis associated with bronchiectasis in the lingular division of the left upper lobe. Nontuberculous mycobacteria were isolated three times from sputum specimens. All isolates were identified as M. chelonae by various molecular methods that characterized rpoB and hsp65 gene sequences. Although some new lesions including bronchiolitis in the superior segment of the left lower lobe developed on the chest CT scan 35 months after diagnosis, she has been followed up without antibiotic therapy because of her mild symptoms. To the best of our knowledge, this is the first case of M. chelonae lung disease in Korea in which the etiologic organisms were confirmed using molecular techniques.

An efficient pulse compression method of chirp-coded excitation in medical ultrasound imaging

Changhan Yoon,Wooyoul Lee,Jin Chang,Tai-kyong Song,Yangmo Yoo IEEE 2013 and Frequency Control Vol.60 No.10

<P>Coded excitation can improve the SNR in medical ultrasound imaging. In coded excitation, pulse compression is applied to compress the elongated coded signals into a short pulse, which typically requires high computational complexity, i.e., a compression filter with a few hundred coefficients. In this paper, we propose an efficient pulse compression method of chirp-coded excitation, in which the pulse compression is conducted with complex baseband data after downsampling, to lower the computational complexity. In the proposed method, although compression is conducted with the complex data, the L-fold downsampling is applied for reducing both data rates and the number of compression filter coefficients; thus, total computational complexity is reduced to the order of 1/L<SUP>2</SUP>. The proposed method was evaluated with simulation and phantom experiments. From the simulation and experiment results, the proposed pulse compression method produced similar axial resolution compared with the conventional pulse compression method with negligible errors, i.e., >36 dB in signal-to-error ratio (SER). These results indicate that the proposed method can maintain the performance of pulse compression of chirp-coded excitation while substantially reducing computational complexity.</P>

초.중학교 시기 학업탄력성의 종단적 변화 양상 및 영향 요인 탐색

이지용(Jiyong Lee),나우열(Wooyoul Na),이현숙(Hyun Sook Yi) 학습자중심교과교육학회 2021 학습자중심교과교육연구 Vol.21 No.20

목적 본 연구는 학업탄력성의 종단적인 변화 양상을 파악하고 이에 영향을 미치는 요인을 탐색하는 것을 목적으로 한다. 방법 이를 위해 한국교육종단연구(KELS) 2013의 초등학교 6학년부터 중학교 3학년까지 4시점의 데이터를 활용하여 전체 학생들의 각 시점별 학업탄력성에 따른 집단의 규모와 학업성취도를 파악하고, 학업탄력성의 변화를 살펴보았다. 또한 취약계층 학생들의 학업탄력성 변화 양상에 따라 유형을 세분화하고 학업탄력성의 변화에 영향을 미치는 요인을 탐색하기 위해 다층 다항 로지스틱 회귀모형 분석을 실시하였다. 결과 본 연구의 주요 결과는 다음과 같다. 첫째, 시간이 지날수록 비취약계층-우수 집단과 비학업탄력적 집단의 규모는 증가하는 한편, 학업탄력적 집단의 규모는 감소하는 경향을 보였다. 둘째, 초기에 학업탄력적 집단이었으나 시간이 지나 비학업탄력적 집단으로 이동하는 학생들의 규모는 그 반대의 경우에 비해 더 큰 것으로 나타났다. 셋째, 학업탄력성이 하락하는 유형이 비교적 높은 비율을 차지하였으며, 이러한 학생들은 초⋅중학교의 전환기 시점에서 학업성취도의 감소폭이 비교적 큰 것으로 나타났다. 넷째, 수업이해도, 학업과 관련된 여가 시간 활용, 교사의 학생 특성 파악 정도 등의 변인은 학업탄력적 유지 유형에 대해 정적인 영향을 미치는 것으로 나타났다. 결론 본 연구는 기술통계와 시각화 기법을 중심으로 전국의 초등학교 6학년부터 중학교 3학년까지의 4년간 전체 학생들의 학업탄력성에 따른 집단 변화 양상을 포괄적으로 탐색하였다는 의의가 존재한다. Objectives The purpose of this study was to explore longitudinal trends in academic resilience and characteristics associated with patterns of these trends. Methods Achievement data and survey data annually measured for the students from the 6th to 9th grades in the Korea Educational Longitudinal Study (KELS) 2013 were used for the analyses. Students at each time point were classified into one of the four groups defined by the status of academic resilience and relative proportion of students in each sub-group and their academic achievement were explored. In addition, multilevel-multinomial logistic regression model was employed to identify characteristics that predict the patterns of longitudinal trends of academic resilience for socio-economically disadvantaged class. Results The major results of this study are as follows. First, while the proportion of students who have shown excellent academic performance among socio-economically non-disadvantaged class and the proportion of students who have shown poor academic performance among socio-economically disadvantaged class have been increased over time, the proportion of academic resilient students who have shown excellent academic performance among socio-economically disadvantaged class has been decreased. Second, the proportion of students who have transitioned from academic resilient group to academic non-resilient group was larger than that of their counterparts, and the extent to which their academic achievement declined was highest during the time of transition from elementary school to middle school. Third, it was found that characteristics such as comprehension of class materials, the out-of-school study time, and teacher s understanding of student characteristics showed positive effect in predicting academic resilience. Fourth, There was a positive effect of the introjected regulation for students who have transitioned from academic resilient group to academic non-resilient group compared with students who have preserved academic non-resilient group. Conclusions This study showed implication in that it was comprehensively explored the longitudinal group change trends according to academic resilience from 6th grade to 9th grade using descriptive analysis and visualization.

Mechanical Properties and Biodegradation Study on Blends of PLA and Chemically Modified Hasticized Starch

조규순,( Booyoung Shin ),( Sangil Lee ),( Sangil Cho ),( Sanghee Jang ),( Baekhee Cho ),( Kiheon Hong ),( Bongshick Kim ),( Wooyoul Jang ),( Kyoungsu Kang ) 한국공업화학회 2006 한국공업화학회 연구논문 초록집 Vol.2006 No.1

순환신경망(RNN)을 활용한 개별 학생 학업성취도의 종단적 예측

이창묵(Chang-mook Lee),이현숙(Hyun Sook Yi),나우열(Wooyoul Na) 한국교육평가학회 2020 교육평가연구 Vol.33 No.1

학생들이 학교교육을 통해 기초학력을 갖추도록 돕는 것은 공교육이 담당해야 할 중요한 책무이다. 기초학력에 도달하지 못한 상태에서 다음 학년에 진입하게 되면 기초학력 미달이 장기화할 수 있고 결과적으로 학업적 실패로 이어질 수 있기 때문이다. 따라서 학생의 미래 성취 수준을 조기에 예측하고 적시에 개입하는 것은 매우 중요하다. 이에 본 연구에서는 개별 학생의 학업성취 수준을 예측하기 위한 방법으로서, 최근 다양한 분야에서 활용되고 있는 순환신경망(RNN)을 국가수준 학업성취도평가 자료에 적용함으로써, 교육 종단 자료를 바탕으로 미래의 학업 성취를 예측할 수 있는 방안을 탐색하였다. 본 연구에서는 2011년 초등 6학년부터 2016년 고등 2학년까지 세 시점의 국가수준 학업성취도평가 자료를 사용하였으며, RNN을 적용하여 미래 시점의 기초 이하 여부를 예측한 결과를 HGLM 모형 적용 결과와 비교하였다. 두 모형은 대체로 유사한 예측 성능을 보였으며, HGLM으로는 결과 산출이 어려운 구조에서도 RNN을 적용하여 기초 이하 여부를 예측할 수 있었다. 본 연구 결과를 토대로 학업성취의 조기예측과 관련한 순환신경망의 장점과 제한점에 대해 제안하였다. Helping students to meet the national standards of academic performance is very important in that failure to meeting the standards can have a detrimental effect on learning and can lead to long-term learning deficits. It is important to understand the state of individual student s academic achievement and identify students with potential academic failure, so that timely intervention can be made to prevent student failure. In this study, an artificial neural network (ANN) was applied to the National Assessment of Educational Achievement data to predict performance of a student in his/her 11th grade based on various information related to academic performance collected in the 6th and 9th grades. The recurrent neural network (RNN) was employed as a promising model for longitudinal prediction, and the performance of the RNN was compared with a traditional approach, the hierarchical general linear model (HGLM). The results showed that both RNN and HGLM models showed similar performances in the data collection designs to which both models can be applied. In addition, the RNN had advantages over the HGLM in that it can be also applied to situations where application of the HGLM is not feasible. Based on the results of this study, the advantages and disadvantages of the RNN in longitudinal prediction of educational data was discussed.

Nontuberculous Mycobacterial Lung Disease Caused by Mycobacterium chelonae: A Case Report

Ko, Yousang,Kim, Wooyoul,Shin, Beom Su,Yoo, Hongseok,Eom, Jung Seop,Lee, Ji Hyun,Jhun, Byung Woo,Kim, Su-Young,Choi, Go-Eun,Shin, Sung Jae,Koh, Won-Jung The Korean Academy of Tuberculosis and Respiratory 2013 Tuberculosis and Respiratory Diseases Vol.74 No.4

Mycobacterium chelonae lung disease is very rare. We report a case of lung disease caused by M. chelonae in a previously healthy woman. A 69-year-old woman was referred to our hospital because of hemoptysis. A computed tomography (CT) scan of the chest revealed bronchiolitis associated with bronchiectasis in the lingular division of the left upper lobe. Nontuberculous mycobacteria were isolated three times from sputum specimens. All isolates were identified as M. chelonae by various molecular methods that characterized rpoB and hsp65 gene sequences. Although some new lesions including bronchiolitis in the superior segment of the left lower lobe developed on the chest CT scan 35 months after diagnosis, she has been followed up without antibiotic therapy because of her mild symptoms. To the best of our knowledge, this is the first case of M. chelonae lung disease in Korea in which the etiologic organisms were confirmed using molecular techniques.

A New Dynamic Complex Baseband Pulse Compression Method for Chirp-Coded Excitation in Medical Ultrasound Imaging

Jinbum Kang,Yeajin Kim,Wooyoul Lee,Yangmo Yoo IEEE 2017 and Frequency Control Vol.64 No.11

<P>Chirp-coded excitation can increase the signal-to-noise ratio (SNR) without degrading the axial resolution. Effective pulse compression (PC) is important to maintain the axial resolution and can be achieved with radio frequency (RF) and complex baseband (CBB) data (i.e., PCRF and PCCBB, respectively). PCCBB can further reduce the computational complexity compared to PCRF; however, PCCBB suffers from a degraded SNR due to tissue attenuation. In this paper, we propose a new dynamic CBB PC method (PCCBB-Dynamic) that can improve the SNR while compensating for tissue attenuation. The compression filter coefficients in the PCCBB-Dynamic method are generated by dynamically changing the demodulation frequencies along with the depth. For PC, the obtained PCCBB-Dynamic coefficients are independently applied to the in-phase and quadrature components of the CBB data. To evaluate the performance of the proposed method, simulation, phantom, and in vivo studies were conducted, and all three studies showed improved SNR, i.e., maximally 3.87, 7.41, and 5.75 dB, respectively. In addition, the measured peak range sidelobe level of the proposed method yielded lower values than the PCRF and PCCBB, and it also derived a suitable target location, i.e., a <0.07-mm target location error, while maintaining the axial resolution. In an in vivo abdominal experiment, the PCCBB-Dynamic method depicted brighter and clearer features in the hyperechoic region because highly correlated signals were produced by compensating for tissue attenuation. These results demonstrated that the proposed method can improve the SNR of chirp-coded excitation while preserving the axial resolution and the target location and reducing the computational complexity.</P>

Normalization of Elevated CA 19-9 Level after Treatment in a Patient with the Nodular Bronchiectatic Form of Mycobacterium abscessus Lung Disease

Chang, Boksoon,Han, Seo Goo,Kim, Wooyoul,Ko, Yousang,Song, Junwhi,Hong, Goohyeon,Eom, Jung Seop,Lee, Ji Hyun,Jhun, Byung Woo,Koh, Won-Jung The Korean Academy of Tuberculosis and Respiratory 2013 Tuberculosis and Respiratory Diseases Vol.75 No.1

Carbohydrate antigen 19-9 (CA 19-9) is a widely-used tumor marker in patients with pancreatic cancer. However, some patients with respiratory disease also exhibit elevated serum CA 19-9 levels. We report a case of normalization of elevated serum CA 19-9 levels after treatment of the nodular bronchiectatic form of Mycobacterium abscessus lung disease. A 40-year-old man visited our hospital because of chronic cough and sputum. A computed tomography scan revealed severe bronchiectasis in the right upper and right middle lobes. Nontuberculous mycobacteria were repeatedly isolated and identified as M. abscessus. The serum CA 19-9 level was elevated to 142.35 U/mL (normal range, <37 U/mL). Surgical resection was performed because of failure of sputum conversion after antibiotic treatment. The serum CA 19-9 level returned to the normal range after surgery. This case suggested that serum CA 19-9 levels could be elevated in patients with the nodular bronchiectatic form of M. abscessus lung disease.