액체로켓엔진 시스템 정현파 진동 구조해석

정용현,이은석,박순영,양창환,정진택,Chung, Yong-hyun,Lee, Eun-seok,Park, Soon-young,Yang, Chang-hwan,Jung, Jin-taeg 항공우주시스템공학회 2009 항공우주시스템공학회지 Vol.3 No.2

The structural analysis of liquid rocket engine was performed in the case of sinusoidal vibration load to verify structural safety. The finite element model is composed with main liquid rocket engine components, combustion chamber, turbopump, gas-generator, pyro-starter, main pipes, main valve, heat-exchanger, gimbal-mount and brackets. Natural vibration mode analysis and structural analysis for sinusoidal vibration load were performed. The natural mode frequency of liquid rocket engine is twice than that of launch vehicle. In the case of stress result of sinusoidal vibration load, the part of maximum stress has 1.4 margin, so the engine structure is safe for sinusoidal vibration load.

액체로켓엔진 시스템 Lay-out 설계 개념 연구

정용현,이은석,Chung, Yong-hyun,Lee, Eun-Seok 항공우주시스템공학회 2007 항공우주시스템공학회지 Vol.1 No.4

The process of Lay-out design and assembly for liquid rocket engine was presented and the Lay-out design for main components of liquid Rocket engine system was studied. Vertical direction is recommended in the case of turbopump's arrangement. If the length of pipe between gas-generator with turbopump's turbine is shorter, gas-generator is stable. The arrangements of main valves are recommended as near disposition to combustion chamber, because shut-down process time is shorter. Interference with launch vehicle and structural strength considering gimbal actuator's force and control performance is considered in the case of gimbal actuator's supporter design.

배열형 섬광결정을 이용한 소형 감마카메라의 평행구멍형 조준기 최적화 연구

정용현,백철하,이승재,박진형,Chung, Yong-Hyun,Beak, Cheol-Ha,Lee, Seung-Jae,Park, Jin-Hyung 한국의학물리학회 2008 의학물리 Vol.19 No.4

이 연구의 목적은 몬테칼로 모사방법을 이용하여 배열형 CsI 섬광결정을 가진 소형 감마카메라의 평행구멍형 조준기를 최적화하고 조준기 부착시 발생할 수 있는 결합오차가 영상의 질에 미치는 영향을 평가하는 것이다. GATE 코드를 이용하여 육각형과 사각형 평행구멍형 조준기의 구멍크기에 따른 Tc-99m 점선원 영상의 민감도 및 공간분해능을 측정하고 최적화된 조준기를 바탕으로 조준기와 섬광체 사이에 2 mm 이내의 미세한 틈이 있을 경우에 대한 평판선원의 영상 균일도를 측정하였다. 동일 구멍크기에 대해 사각구멍형 조준기가 육각구멍형 조준기에 비해 민감도가 우수한 결과를 보였으며, 섬광결정과 사각구멍조준기의 크기를 1 대 4로 일치시켰을 때, 선원의 거리에 따른 공간분해능의 변화가 가장 적은 것을 알 수 있었다. 조준기와 검출기의 결합면 평행오차는 영상의 균일도와 민감도 모두를 선형적으로 감소시키는 경향을 보였다. 이 연구 결과는 배열형 섬광결정과 단일 섬광결정에 대해 조준기의 성능차이를 보이고, 영상의 균일도 및 민감도 저하의 원인이 조준기의 결합오차에서 기인할 수 있음을 증명함으로써, 핵의학 영상 화질 개선을 위한 새로운 접근법을 제시한다. The purpose of this study is to optimize a parallel-hole collimator for small gamma camera having the pixellated crystal array and evaluate the effect of crystal-collimator misalignment on the image quality using a simulation tool GATE (Geant4 Application for Tomographic Emission). The spatial resolution and sensitivity were measured for the various size of hexagonal-hole and matched square-hole collimators with a Tc-99m point source and the uniformity of flood image was estimated as a function of the angle between crystal array and collimator by misalignment. The results showed that the spatial resolution and sensitivity were greatly improved by using the matched collimator and the uniformity was reduced by crystal-collimator misalignment.

3-MCPD의 생식˙발생독성에 관한 연구

곽승준(Seung Jun Kwack),김순선(Soon Sun Kim),최요우(Yo Woo Choi),이규식(Gyu Seek Rhee),손경희(Kyung Hee Sohn),이이다(Rhee Da Lee),채수영(Soo Young Chae),정용현(Yong-Hyun Chung1),유일재(Il Je Yu1),박귀례(Kui Lea Park) 한국독성학회 2004 Toxicological Research Vol.20 No.2

3-Monochloro-1,2-propanediol(3-MCPD) is a toxic compound, often present in different foods containing acid hydrolyzed(AH) protein, like seasonings and savory food products. The purpose of the present study was to investigate the effects of 3-MCPD on male fertility, sperm and testosterone secretion. In vivo male fertility test was performed for observing the adverse effects of 3-MCPD on the function of male reproductive system and pregnancy outcome. 0.01, 0.05, 0.25, 1 and 5 mg/kg b.w. of 3-MCPD was given daily by gavage to groups of 15 adult male SD rats for 4 weeks. At the end of pre-treatment period, males were mated overnight with normal females. Following morning, males demonstrating successful induction of pregnancy were sacrificed on that day to assess sperm parameters and histopathology of reproductive organs. The resulting pregnant females were sacrificed on day 20 of gestation to evaluate pregnancy outcome. As a result, four-week paternal administration with 3-MCPD resulted in adverse effects on male fertility and pregnancy outcome without remarkable histopathological changes in testes and epididymides; sperm motility, copulation index and fertility index were markedly decreased in the treated group and numbers of live fetuses showed steep dose-response curves. Also, spermatogenesis was investigated in this experiment. However, no<br/> effect was observed on production of sperm in testes treated with 3-MCPD for 4 weeks. Hormone assay was performed for observing the effects of 3-MCPD on testosterone and luteinizing hormone (LH) in blood and testes of male SD rats and cultured primary Leydig cell. In result, significant changes of related hormones did not observed by treatment of 3-MCPD. These results indicated that paternal treatment with 3-MCPD induced spermatotoxic effect, which caused an antifertility on male.

랫드에 주입된 세피오라이트에 의한 호흡기독성 연구

정용현(Yong Hyun Chung),한정희(Jeong Hee Han),성재혁(Jae Hyuck Sung),유일재(Il Je Yu) 한국독성학회 2006 Toxicological Research Vol.22 No.3

Two kinds of sepiolite, a 500℃ heat-treated sepiolite, and a 700℃ heat-treated sepiolite were analyzed for their physicochemical properties. After these sepiolites were instilled into rat lungs, the effects of the substances on lung pathological changes were evaluated. The lungs instilled with sepiolite increased their weight compared with the unexposed control. The pathological examination further showed increased legions of granuloma with early fibrosis. The heat treated sepiolites, however, did not show any toxicological differences from the untreated sepiolites. Thus chronic experiments are needed to evaluate the durability of mineral fibers, which is an essential experiment for evaluating biopersistence of fibers in lungs.

액체로켓엔진 연소기 챔버 구조 설계

정용현(Yong-Hyun Chung),류철성(Chul-Sung Ryu) 한국추진공학회 2004 한국추진공학회지 Vol.8 No.4

목재와 도자 소재의 융합적 접근에 의한 오브제 기능의 가구 연구

정용현(Chung, Yong Hyun),최경란(Choi, Kyung Ran) 한국전시산업융합연구원 2015 한국과학예술융합학회 Vol.19 No.-

본 연구에서는 심미적 기능의 오브제로서의 공예와 공간에서 실용적 기능으로서의 소재를 융합한 가구디자인으로 공간에서의 새로운 역할을 부여하기 위한 시도에 그 목적이 있다. 따라서 가구디자인은 목재와 도자 소재의 융합적시도로서 그것이 가진 가치와 가능성을 보여준다. 연구의 범위와 방법은 도자인 예술 분야와 목공이라는 디자인 분야의 다른 재료 및 소재의 혼합과 연결되어 있다. 도자로 제작된 다리와 월넛 나무로 제작된 상판의 전혀 다른 소재가 어우러지도록 융합되어 제작한다. 직접 가구를 제작함에 있어 도자기가 쌓아진 형식을 차용한 도자 다리를 제작하여 시각적으로 제한된 기존 가구디자인과 차별된 디자인을 창출하고, 흙과 유약에서 보이는 색감과 질감으로 나무에서 얻을 수 없었던 색다른 느낌을 보여주어 가구와 그것이 놓인 공간의 신선한 어울림을 기대한다. 포스트모던 이후 디자인과 예술의 경계가 모호해지고 있다. 본 연구를 통해 가구 상판에 기능과 형상을 자유롭게 조화시킬 수 있는 개념의 현대의 다양성 그리고 가구와 오브제와의 역할에 대한 경향을 고려한 디자인을 제안하고자 한다. Postmodernism has blurred the line between design and art. We would like to suggest a design case that took diversity in the modern era that harmonizes functionality and shape of the top board of a furniture and trend of the role of furniture and objet into consideration. This study aims to project a new role into space via convergence of objet that has aesthetic function and furniture design that plays practical role in space. Thus, furniture design attempts to combine ceramic and carpentry and demonstrate the value and potential the combination possesses. By creating a distinct design from previous furniture that had visual limitations with ceramic bridge that adopted existing piling method in ceramic design, we expect a fresh blend of furniture and space that encompasses a different sensation from color and texture of soil and glaze, unable to attain from simple wood.

A Study on GHS Classification of Potassium nitrate by acute oral Toxicity

Yong Hyun Chung(정용현) 환경독성보건학회 2017 한국독성학회 심포지움 및 학술발표회 Vol.2017 No.5

A study on health hazard classification of Potassium nitrate by acute dermal toxicity test

Yong Hyun Chung(정용현) 환경독성보건학회 2018 한국독성학회 심포지움 및 학술발표회 Vol.2018 No.6

한국산 백석면이 랫드의 폐 기능에 미치는 영향 평가 연구

정용현 ( Yong Hyun Chung ),강민구 ( Min Gu Kang ),한정희 ( Jeong Hee Han ) 한국산업보건학회 2014 한국산업보건학회지 Vol.24 No.2

Objectives: To evaluate the pulmonary toxicity of Korean Chrysotile(KC), the lung function and the number of fibers in the bronchoalveolar lavage fluid of Sprague-Dawley rats instilled with KC were estimated. Materials: Rats were administered 1 ㎎ KC by a single intratracheal instillation. At each time point(5 days, 5 weeks, 10 weeks), the lung function of the rats was analyzed by pressure transducer and the amount of asbestos in the bronchoalveolar lavage fluid of the rats was calculated by transmission electron microscope equipped with energy dispersive X-ray spectrometer. Results: The lung function of the rats at 5 days after instillation of KC was confirmed to be degraded. However, after 5 weeks the test groups showed a tendency to recover lung function. Still, after 10 weeks the lung function of the test groups had not recovered completely. The number of fibers in the bronchoalveolar lavage fluid of the rats instilled with KC rapidly decreased. At 5 weeks the number of fibers had reduced to approximately 1/2 of that found at 5 days. Over time, at 10 weeks it had rapidly decreased to 1/100 that found at 5 days. Conclusions: Korean chrysotile fibers rapidly decreased in the lungs of rats, but the lung function of rats instilled KC does had not completely recovered by 10 weeks.