Analysis of Requirements for New Aids-to-Navigation Service: Focusing on Ship Operator

Sangwon Park(Sangwon Park),Min-Ji Jeong(Min-Ji Jeong),Yunja Yoo(Yunja Yoo) 한국항해항만학회 2022 한국항해항만학회지 Vol.46 No.5

With digitalization accelerated by the 4th industrial revolution, the marine traffic environment is also expected to change rapidly. The purpose of this study was to derive a new service for Aids to Navigation (AtoN) to respond to a new marine traffic environment and suggest service requirements from the perspective of the ship’s operator. For this purpose, a survey of ship operators was conducted and IPA analysis was performed. Marine traffic intelligence and information services and Image-based ocean environment information services were deduced as high-priority services from the perspective of ship operators. Thus, the derived results can serve as basic data for developing new AtoN services and determining policy directions.

셀프 프리스트레싱 스터럽으로 보강된 철근콘크리트 보의 전단거동 예측

지상원 ( Ji Sangwon ),연영모 ( Yeon Yeongmo ),홍기남 ( Hong Kinam ),한민철 ( Han Mincheol ),정병은 ( Jung Byungeun ) 한국복합신소재구조학회 2022 복합신소재구조학회논문집 Vol.13 No.5

본 논문은 철계형상기억합금(Fe-SMA) stirrup으로 전단보강된 철근콘크리트 보의 전단거동을 예측하기 위한 해석적 연구이다. 전단거동 예측을 위해 변형률 적합조건 및 하중 평형조건을 만족하는 휨해석이 수행되었으며, 이후 수정압축장이론(MCFT)에 기반한 전단해석이 수행되었다. 부재의 처짐을 계산하기 위해 휨 및 전단에 의해 발생된 처짐이 모두 고려되었다. 제안된 해석모델의 검증은 Ji et al.(2022)의 실험결과를 비교하여 수행되었다. 비교결과 제안된 해석모델과 실험결과의 극한하중, 극한하중 시 처짐의 오차는 평균 4.77%, 6.62%로 Fe-SMA Stirrup으로 전단보강된 철근콘크리트 보의 전단 거동을 비교적 정확하게 예측하는 것으로 나타났다. An analytical study is conducted to predict the shear behavior of reinforced concrete beams strengthened with Fe-based shape memory alloy (Fe-SMA) stirrup. To predict the shear behavior, flexural analysis that satisfies the strain distribution condition and force equilibrium condition was performed, followed by shear analysis based on the modified compression field theory. To calculate the deflection of the member, both the flexural and shear deflection were considered. The proposed analysis model was verified by comparing the experimental results of Ji et al. (2022). As a result of the comparison, the errors of deflection under ultimate load and ultimate load of the proposed analytical model and experimental results were on average 4.77% and 6.62%, respectively, indicating that the shear behavior of reinforced concrete beams strengthened with Fe-SMA stirrup was predicted relatively accurately.

The Error Analysis of Leak Measurement for Pneumatic Cylinder using Isothermal Chamber

Sangwon JI,Jiseong JANG,Toshiharu KAGAWA 유공압건설기계학회 2007 유공압건설기계학회 학술대회논문집 Vol.2007 No.11

CFRP 그리드의 정착 길이에 따른 콘크리트 보의 휨거동

지상원 ( Ji Sangwon ),주봉철 ( Joo Bongchul ),홍기남 ( Hong Kinam ) 한국복합신소재구조학회 2024 복합신소재구조학회논문집 Vol.15 No.1

본 논문은 CFRP 그리드의 정착길이에 따른 콘크리트 보의 휨거동을 평가한 실험적 연구를 보고한다. 실험을 위해 폭 250 mm, 높이 125 mm, 길이 2000 mm의 실험체가 제작되었다. 실험변수로 CFRP 그리드의 정착길이(1000 mm, 800 mm, 700 mm, 600 mm, 500 mm, 400 mm, 300 mm, 200 mm)가 고려되었다. 실험체 제작 후 3점 휨실험이 수행되었다. 실험결과 모든 실험체의 강성은 정착길이에 영향을 받지 않고 유사한 것으로 나타났다. 초기 균열하중은 모든 실험체에서 유사하게 나타났으나, 정착길이가 감소됨에 따라 최대하중, 최대하중 시의 처짐 및 변형률은 감소하는 경향을 나타냈다. 특히 부재 길이에 80% 이상이 정착된 경우 부재 길이와 동일한 정착길이를 가진 콘크리트 보의 약 90% 이상의 구조성능을 확보할 수 있는 것으로 확인되었다. 제안된 수치해석 모델은 CFRP 그리드의 정착길이가 감소됨에 따른 극한하중의 저하를 유사하게 예측하였으며, 극한하중의 오차는 평균 13.1%로 CFRP 그리드의 정착길이에 따른 콘크리트 보의 휨성능을 비교적 정확하게 예측하는 것으로 나타났다. This paper presents an experimental study on the flexural behavior of concrete beams based on the development length of the Carbon Fiber Reinforced Polymer (CFRP) grid. For experiments, we fabricated specimens with width, height, and length of 250, 125, and 2000 mm, respectively. The development lengths of the CFRP grid (1000, 800, 700, 600, 500, 400, 300, and 200 mm) were considered as experimental variables. Three-point bending tests were conducted after fabricating the specimens. Results showed that the stiffness of all specimens remained the same and was unaffected by the development length. The initial crack load was similar in all specimens, but the maximum load, deflection, and strain tended to decrease as the development length decreased. In particular, it was confirmed that when >80% of the member length was anchored, the structural performance of ~90% or more of a concrete member with a development length equal to the member length can be achieved. The proposed numerical model accurately predicted the ultimate load reduction due to the decrease in the development length of the CFRP grid, with an average error of 13.1% in the ultimate load. Thus, the proposed model can reasonably accurately predict the flexural performance of concrete members with respect to the development length of the CFRP grid.

철계-형상기억합금 나선철근으로 횡구속된 콘크리트의 압축거동

지상원 ( Ji Sangwon ),연영모 ( Yeon Yeongmo ),홍기남 ( Hong Kinam ) 한국복합신소재구조학회 2020 복합신소재구조학회논문집 Vol.11 No.6

본 논문은 철계형상기억합금(Fe-SMA) 나선철근을 이용한 기둥의 횡구속 효과를 평가한 실험적 연구를 보고한다. 실험을 위해 사전변형 4%의 5mm × 5mm의 Fe-SMA 나선철근으로 구속된 150mm × 150mm ×300mm의 원형 실험체가 제작되었다. 실험변수는 Fe-SMA 나선철근의 피치(0mm, 80mm, 60mm, 40mm), Fe-SMA 나선철근의 활성화 유무(활성화, 비활성화)를 고려하였다. Fe-SMA 나선철근 활성화를 위해 소성로를 사용하여 목표온도 140℃까지 가열하였다. 실험체의 온도가 상온에 도달한 후 만능재료시험기를 이용하여 1축 압축실험을 실시하였다. 실험결과를 통해 Fe-SMA 나선철근을 활성화하여 능동적 횡구속압이 작용된 실험체의 최대응력과 최대응력 발현 시의 변형률은 활성화하지 않은 실험체에 비해 크게 증가하는 것으로 나타났다. 또한, 나선철근 피치의 감소로 인해 능동적 구속압이 증가함에 따라 최대응력과 연성지수가 크게 증가하는 것으로 나타났다. 특히 보강 간격이 40mm인 활성화된 나선철근으로 구속된 실험체는 최대하중 도달 후 하중이 유지 및 증가하는 변형경화가 발생하는 것으로 나타났다. This study evaluates the lateral confinement effect of a column using Fe-based shape memory alloy (Fe-SMA) spiral reinforcement. For the experiment, 150 × 150 × 300-mm cylinder specimens confined by Fe-SMA spiral reinforcement of a 4% pre-deformed 5 × 5-mm section were fabricated. Two experimental variables were considered: the pitch (0, 80, 60, and 40mm) and activation/non-activation of the Fe-SMA spiral reinforcement. To activate the Fe-SMA spiral reinforcement, the specimen was heated to the target temperature of 140° using a kiln. After the specimen was cooled to room temperature, a uniaxial compression test was performed using a universal testing machine. The experimental results confirm that the maximum stress and corresponding strain of the specimen with Fe-SMA spiral reinforcement activation were significantly increased compared with that of the specimen without activation. Additionally, it was found that, due to the decreased pitch of the spiral reinforcement, the maximum stress and ductility index increased significantly as the active lateral confinement pressure increased. In particular, it was found that the specimens confined by activated 40-mm-pitch spiral reinforcement exhibited strain hardening, which maintained and increased the load after the maximum load was reached.

Measuring T1 contrast in ex-vivo prostate tissue at the Earth’s magnetic field

Sangwon Oh,한재호,Ji Eun Kwon,심정현,이성주,황성민,Ingo Hilschenz,김기웅 한국자기공명학회 2019 Journal of the Korean Magnetic Resonance Society Vol.23 No.1

A former study has shown that the spin-lattice relaxation time (T1) in cancerous prostate tissue had enhanced contrast at an ultra-low magnetic field, 132 uT. To study the field dependence and the origin of the contrast we measured T1 in pairs of ex-vivo prostate tissues at the Earth’s magnetic field. A portable and coil-based nuclear magnetic resonance (NMR) system was adopted for T1 measurements at 40 uT. The T1 contrast, delta = 1 - T1 (more cancer)/T1(less cancer), was calculated from each pair. Additionally, we performed pathological examinations such as Gleason’s score, cell proliferation index, and micro-vessel density (MVD), to quantify correlations between the pathological parameters and T1 of the cancerous prostate tissues.

Estimating the number of severe COVID-19 cases and COVID-19-related deaths averted by a nationwide vaccination campaign in Republic of Korea

Ji Hae Hwang,Ju Hee Lee,Eun Jung Jang,Ryu Kyung Kim,Kil Hun Lee,Seon Kyeong Park,Sang Eun Lee,Chungman Chae,Sangwon Lee,Young Joon Park 질병관리본부 2023 Osong Public Health and Research Persptectives Vol.14 No.3

Objectives: The Korea Disease Control and Prevention Agency promotes vaccination by regularly providing information on its benefits for reducing the severity of coronavirus disease 2019 (COVID-19). This study aimed to analyze the number of averted severe COVID-19 cases and COVID-19-related deaths by age group and quantify the impact of Republic of Korea’s nationwide vaccination campaign.Methods: We analyzed an integrated database from the beginning of the vaccination campaign on February 26, 2021 to October 15, 2022. We estimated the cumulative number of severe cases and COVID-19-related deaths over time by comparing observed and estimated cases among unvaccinated and vaccinated groups using statistical modeling. We compared daily age-adjusted rates of severe cases and deaths in the unvaccinated group to those in the vaccinated group and calculated the susceptible population and proportion of vaccinated people by age.Results: There were 23,793 severe cases and 25,441 deaths related to COVID-19. We estimated that 119,579 (95% confidence interval [CI], 118,901–120,257) severe COVID-19 cases and 137,636 (95% CI, 136,909–138,363) COVID-19-related deaths would have occurred if vaccination had not been performed. Therefore, 95,786 (95% CI, 94,659–96,913) severe cases and 112,195 (95% CI, 110,870–113,520) deaths were prevented as a result of the vaccination campaign.Conclusion: We found that, if the nationwide COVID-19 vaccination campaign had not been implemented, the number of severe cases and deaths would have been at least 4 times higher. These findings suggest that Republic of Korea’s nationwide vaccination campaign reduced the number of severe cases and COVID-19 deaths.

New Approach for developing soft magnetic materials and Industrial Needs (In terms of Power Electronics)

Sangwon Lee,Eunyoung Jang,Suhwan Ryu,Ji-Yeol Yoon,Minae Ouk,Jongsun Jeong,Jaihoon Yeom,Soyeon Park,Minwook Choi,Gunwoo Noh 한국자기학회 2023 한국자기학회 학술연구발표회 논문개요집 Vol.33 No.1

Machine Learning-based Low-loss Ferrite Development for High-frequency Power Converter

Ji-Yeol Yoon,Jaihoon Yeom,Suhwan Ryu,Eunyoung Jang,HyunJi Lee,Jongsun Jeong,Joonwook Han,Soyeon Park,Minwook Choi,Gunwoo Noh,Sangwon Lee 한국자기학회 2023 한국자기학회 학술연구발표회 논문개요집 Vol.33 No.2

The Error Analysis of Leak Measurement for Pneumatic Cylinder Using Isothermal Chamber

장지성,Sangwon Ji,Toshiharu Kagawa 사단법인 유공압건설기계학회 2008 드라이브·컨트롤 Vol.5 No.1

ISO pneumatic cylinder reliability test requires air leakage measurement. Air cylinder has many parts and the leakage shall be measured before, during and after endurance test, and, the leakage should smaller than the specified value. The existing measurement method needs complex operation and the calibration of leak detector, and, has to separate the testing cylinder from endurance test device, which causes the change of contact condition of seal in the cylinder. Therefore, it is hard to evaluate the air leakage during endurance test, and guarantee the reliability of the conventional measurement method. In this paper, a new method for air leakage measurement using isothermal chamber, which does not requires calibration or temperature compensation, and, can measure air leakage accurately with quite simple operations, is proposed. As a result, reliability of air leakage measurement can be improved because the proposed method does not have to separate the testing cylinder from the endurance test device for air leakage measurement. The effectiveness of the proposed method is proved by error analysis of leak measurement from experimental result.