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최지아(Ji Ah Choi),지상원(Sang Won Ji),장지성(Ji Seong Jang) 유공압건설기계학회 2021 드라이브·컨트롤 Vol.18 No.3
Hydrogen energy is the clean energy source of the future. Ultra-high-pressure hydrogen is used in hydrogen stations, with its parts being developed. On the other hand, ultra-high-pressure ball valve, which is one of its parts, depends on overseas, with the level of domestic research on this being only about 10% of advanced technology research on this abroad. In this study, the shape of an ultra-high-pressure ball valve for a hydrogen station was designed to improve its structural strength. The valve body was designed according to distance between both processed body holes along inlet and outlet ports. The designed vale body was then analyzed using ANSYS to check whether points with stress were concentrated. In addition, the valve with improved body was analyzed to confirm that the valve satisfied the design condition.
CO₂의 상변화를 고려한 압력 제어 밸브 모델링 및 검증
최지아(Ji Ah Choi),장지성(Ji Seong Jang) 대한기계학회 2020 大韓機械學會論文集B Vol.44 No.9
최근 천연 냉매를 이용한 냉동·공조 시스템 연구가 활발히 진행되고 있다. 이 중 이산화탄소는 작동 압력이 상대적으로 높기 때문에 기존 냉동 · 공조 시스템에 비해 압력비가 작다. 또한, 지구 온난화 지수가 낮기 때문에 친환경적이다. CO₂ 냉매를 이용하는 압력 제어 밸브는 냉동·공조 사이클에서 유체가 기체, 액체, 이상 유동 상태인 모든 부분에 사용된다. 그러므로 본 연구에서는 상변화를 고려한 CO₂ 냉매용 압력제어 밸브의 분석 모델을 개발하고, 실험 결과와 비교를 통하여 검증하였다. Recently, industrial systems using natural refrigerants have been researched. Among these natural refrigerants, carbon dioxide, owing to its relatively high operating pressure, has a smaller pressure ratio compared with those of existing refrigeration systems. Furthermore, it is eco-friendly because it exhibits low global warming potential. The pressure control valve using CO₂ refrigerant is used for all parts where the fluid is gas, liquid and two-phase states in refrigeration and air-conditioning cycle. Therefore, in this study, an analysis model of pressure control valves using a CO₂ refrigerant was developed considering phase change; this model was verified by comparing them with experimental results.
배지원(Ji-Won BAE),최지아(Ji-Ah CHOI),장지성(Ji-Seong JANG) 한국수산해양교육학회 2018 水産海洋敎育硏究 Vol.30 No.4
A flow control valve is a valve that controls the flow rate by regulating the flow path inside the valve. And the degree of opening and closing of the valves changes the cross section of the flow path nonlinearly. In order to increase reliability of the control valve, the valve shall be easily controlled by a simple controller so that the degree of opening and closing of the valve and the cross section of the flow path are linearly related. In this study, in order to achieve a linear relationship between the degree of opening and closing of the valves and the flow path, we has designed a flow control vale consisting of a cone type flow path control elements, body that surrounds the cone by forming a linear flow path and a gear and motor that controls cross section of the flow path according to the travel distance of the cone. And the linearity of the designed valve has been confirmed through simulation and experiment.
박주연(Ju-Yeon Park),장지성(Ji-Seong Jang),지상원(Sang-Won Ji),김학수(Hak-Su Kim),배지원(Ji-Won Bae),최지아(Ji-Ah Choi) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
As vessel pollutant emission regulations are tightened, LNG propulsion vessels with fewer pollutant emissions than existing fuels are increasing. As a result, the LNG ESD system, which is a safety device to block the flow of fluid in an emergency situation generated during LNG bunkering, becomes more important. In this study, a simulation model of LNG bunkering ESD valve was constructed and the dynamic characteristics of the valve were analysised using AMESim, a commercial hydraulic analysis program.
대구경북지역의 제조업과 서비스업간 연계성 분석: 지역 산업네트워크 구조를 중심으로
박문수(Park, Moon Soo),이동희(Lee, Dong Hee),최지아(Choi, Ji Ah) 한국지역개발학회 2017 韓國地域開發學會誌 Vol.29 No.1
From the viewpoint of linkages between manufacturing and service industry, this study analyzed the industrial structure of Daegu and Gyeongbuk region by using network analysis. As a result, we showed that the industrial structure of the regions has been highly concentrated in the primary metal products (steel) industry in Gyeongbuk and the industrial growth is unbalanced. In Daegu and Gyeongbuk area, services with high utilization as intermediate inputs is limited to low value-added labor services such as transport, business support services, wholesale and retail services. In addition, the service industries of Daegu in the network is clearly separated from the manufacturing sector and remains in the periphery, making it difficult to contribute to the advancement of the manufacturing industry. Therefore, there is a need for a policy to preferentially develop a service industry that has high connectivity or linkage in an industrial network.
한승훈(Seung Hun Han),정우영(Woo Young Chung),김보현(Bo Hyun Kim),최지아(Ji Ah Choi),배지원(Ji Won Bae),장지성(Ji Seong Jang) 유공압건설기계학회 2017 유공압건설기계학회 학술대회논문집 Vol.2017 No.11
Semi-submersible drilling rigs are offshore plants that perform function such as ocean exploration for oil and gas acquisition, drilling and production, storage and unloading of crude oil and gas. Semi-submersible drilling rigs use watertight dampers as emergency buoyancy holders. Since the watertight damper is an emergency shutoff device, it is mainly driven by a pneumatic driving system that can operate without power supply. Pneumatic driving system has highly non-linear characteristics due to compressibility of air and external disturbance such as static and coulomb friction. In this paper, a new control algorithm is proposed for the watertight damper driving system based on the sliding mode control. To evaluate control performance and robust stability of the designed controller, the control results were compared with the results using the state feedback controller.