냉매와 습공기가 교차하는 2중관에서 전열계수 예측을 위한 연구

조권희 한국마린엔지니어링학회 1999 한국마린엔지니어링학회지 Vol.23 No.5

This study was conducted to develop new drying process for automatic control and marine engi-neering system. Air-water tests were carried out to investigate dryer performance. The dispersed flow in he dryer test apparatuses was also simulated by using a numerical code which solves the Dittus-Boelter equation for continuous liquid phase and the Reynolds equation of droplet motion for continuous liquid phase and the Reynolds equation of droplet motion for dispersed phase to predict droplet removal efficiency. Proper conditions for dehumidification were optimized by response ambient conditions. When the selected indexes were constrained in the range of 85-98% moisture content above $15^{\circ}$ and more than mass flow rates of moist air 750kg/h. The numerical results were compared with the experimental data pertaining to the removal effi-ciency at chamber stage and overall pressure drop along concentric tubes Good agreement was obtained as for the efficiency while relatively poor agreement was obtained for the relative humidity. The results also showed that the efficiency depended strongly on the relative humidity at the inlet condition which indicated the importance of estimating the heat exchanger length. Effects of some design parameters in both removal efficiency and breakthrough onset condition are discussed.

외상성 안와 골막하혈종 후 상안정맥압박과 함께 나타난 이차적 망막 변화 1예

조권희,임경수,김경태,이성은,서의종 대한안과학회 2023 대한안과학회지 Vol.64 No.12

목적: 외상성 안와 골막하혈종 후 시력저하와 함께 망막에 나타난 비허혈성 중심망막정맥폐쇄 모양의 변화 및 조기 혈종제거술 후성공적으로 호전된 증례를 보고하고자 한다. 증례요약: 13세 남환아가 좌안 주변 둔상 후 발생한 좌안 안와 주위 부종, 복시, 시력저하를 주소로 내원하였다. 좌안 최대교정시력0.4, 안구운동검사상 심한 상전제한 (4-)이 관찰되었으며, 안저에서 시신경부종, 망막정맥확장 및 구불거림이, 형광안저촬영상 동정맥이행시간의 지연(26초) 및 시신경누출 소견이 관찰되었다. 안구초음파 및 안와 자기공명영상에서 좌측 안와상벽의 골막하혈종 및 이차적인 안구 압박 및 돌출, 상안정맥 압박 및 폐쇄 소견이 관찰되었으며, 이에 응급 좌측 안와 골막하혈종제거술을 시행하였다. 수술1달 후 경과 관찰에서 좌안 최대교정시력은 1.0으로 호전되었고, 안구운동 제한은 소실되었다. 술 전 관찰되던 상안정맥압박이 전산화단층촬영에서 사라진 것을 확인하였고, 안저 관찰 및 형광안저촬영에서 나타났던 이상 소견도 정상화 및 호전되었다. 결론: 외상성 안와 골막하혈종에서 상안정맥압박으로 인한 망막 변화가 나타날 수 있으며, 빠른 혈종제거술이 좋은 시력 예후에 도움이 되었다. Purpose: We describe a case with retinal alterations similar to those of nonischemic central retinal vein occlusion, but also with superior ophthalmic vein compression attributable to a traumatic, subperiosteal orbital hematoma. Case summary: A 13-year-old male presented with left periorbital edema, a decrease in vision, and diplopia after blunt periorbital trauma. In ophthalmological evaluations, the best-corrected visual acuity (BCVA) was 0.4 (20/50) and a severe supraduction limitation was apparent (grade -4). Fundus examination revealed optic disc swelling, retinal vein dilation/tortuosity, and an arteriovenous transit time delay of 26s. Fluorescein angiography evidenced optic disc leakage. Ocular sonography and orbital magnetic resonance imaging revealed a superior subperiosteal hematoma in the left orbit accompanied by superior ophthalmic vein compression. We scheduled emergency hematoma evacuation. One month later, the BCVA had increased to 1.0 (20/20) and ocular movement was no longer limited. Orbital computed tomography showed that the superior ophthalmic vein compression had resolved and that the abnormalities observed in the initial fundus examination and fluorescein angiography had improved. Conclusions: Retinal changes that resemble nonischemic central retinal vein occlusion including retinal venous dilation and tortuosity may develop after a traumatic, orbital subperiosteal hematoma. Compressive obstruction of the superior ophthalmic vein may then be in play. Early surgical intervention featuring hematoma evacuation may prevent irreversible visual deterioration.

봉합사를 이용한 인공수정체 공막고정술과 플랜지형 인공수정체 공막내고정술의 수술 결과 비교

조권희(Gwon Hui Jo),서의종(Eoi Jong Seo),정문선(Moon Sun Jung),김경태(Kyung Tae Kim) 대한안과학회 2023 대한안과학회지 Vol.64 No.5

목적: 봉합사를 이용한 고전적인 인공수정체 공막고정술과 무봉합 플랜지형 인공수정체 공막내고정술의 수술 결과와 합병증을 비교하고자 하였다. 대상과 방법: 이전에 인공수정체의 공막 고정을 위해 봉합사를 이용한 고전적인 인공수정체 공막고정술 또는 무봉합 플랜지형 인공수정체 공막내고정술을 받고 6달 이상 경과 관찰하였던 환자를 대상으로 후향적 의무기록을 분석하였다. 수술 전, 수술 후 1달, 3달, 6달째의 시력, 안압, 구면대응치, 난시값을 조사하였고, 수술 시간과 합병증 양상을 비교하였다. 결과: 고전적인 인공수정체 공막고정술을 받은 39안, 무봉합 플랜지형 인공수정체 공막내고정술을 받은 30안, 총 69안을 대상으로하였다. 수술 시간은 무봉합 플랜지형 인공수정체 공막내고정술 그룹에서 유의하게 짧았다(56.3 ± 11.8 vs. 77.7 ± 17.9, p<0.001). 두 그룹 모두에서 수술 전에 비해 수술 후 모든 시기에서 유의한 시력 호전을 보였으며(p<0.05), 두 그룹 간에 평균 최대교정시력, 구면대응치, 난시값, 합병증 빈도에서 차이를 보이지 않았다. 결론: 고전적인 인공수정체 공막고정술과 비교하여 무봉합 플랜지형 인공수정체 공막내고정술은 더 적은 수술 시간으로 효과적인시력 개선 효과를 보여주었다. 따라서 무봉합 플랜지형 인공수정체 공막내고정술은 고전적인 인공수정체 공막고정술의 효과적인 대안이 될 것으로 생각한다. Purpose: We compared the surgical outcomes and complications of conventional, sutured scleral fixation and flanged intrascleral intraocular lens (IOL) fixation. Methods: We retrospectively analyzed the medical records of patients who underwent conventional, sutured scleral fixation or flanged intrascleral IOL fixation and who were then observed for more than 6 months. The best-corrected visual acuity (BCVA), operation time, spherical equivalent (SEQ), astigmatism, and postoperative complications were recorded up to 6 months after surgery. Results: Of sixty-nine enrolled eyes, 39 underwent conventional, sutured scleral fixation (“sutured” group) and 30 flanged intrascleral IOL fixation (“sutureless” group). The operation time was significantly shorter in the sutureless group than in the sutured group (56.3 ± 11.8 vs. 77.7 ± 17.9 minutes, p < 0.001). In both groups, the BCVA and SEQ improved significantly at all visits after surgery compared to the baseline values p < 0.05). There was no between-group difference in BCVA, SEQ, astigmatism, or complications. Conclusions: Compared to conventional, sutured scleral fixation, flanged intrascleral IOL fixation afforded equivalent improvements in visual acuity but with a shorter surgical duration. Therefore, flanged intrascleral IOL fixation is a useful alternative to conventional, sutured scleral fixation.

국외 원전 고장사례 분석을 통한 국내 비상디젤엔진계통 신뢰도개선 연구

조권희(Kwon-Hae Cho),최재성(Jae-Sung Choi),안수길(Soo-Kil Ahn),성게용(Key-Yong Sung),정연기(Yeon-Ki Chung) 한국마린엔지니어링학회 2004 한국마린엔지니어링학회 학술대회 논문집 Vol.2004 No.-

The reliability of Emergency Diesel Generator(EDG) System is considered one of the most important item linked directly with safety and reliability of nuclear power plants (NPPs). EDGs in NPPs adopt large medium-speed diesel engines, which were designed on the basis of marine's, and are in standby during normal plant operation. However, the failure rate of the EDGs in NPPs is not so much lower than that in the marine engines due to the peculiar operation condition such as fast start, frequent starting test, fast loading, high running load, etc. In this paper, the suggestion for reliability improvement of domestic EDGs were provided through the analysis of the failure cases in U.S.A

도로의 차량 밀도 등급을 기반으로 한 VANET 라우팅 프로토콜

조권희 ( Kwonhee Cho ),안상현 ( Sanghyun Ahn ) 한국정보처리학회 2010 한국정보처리학회 학술대회논문집 Vol.17 No.2

VANET 은 ITS 구축에 필수적인 기술로 주변 교통 시스템 환경을 고려한 라우팅 프로토콜이 요구된다. 본 논문에서는 도시 기반의 VANET 환경에서 차량 간의 안정적이고 빠른 통신을 위하여 차량 밀도를 이용한 라우팅 기법을 제안한다. 제안하는 라우팅 기법에서는 하나의 도로를 여러 개의 cell 들로 나누고 차량들은 비콘 메시지와 cell 정보를 이용하여 차량 밀도를 계산한다. 이 차량 밀도를 이용하여 도로를 여러 개의 등급으로 나누고 이 등급을 기반으로 하여 가장 안정적인 경로를 설정한다.

DSA 전극에 의한 선박오폐수의 전해처리(I)-회분식 전해처리-

김인수,조권희,남청도 해양환경안전학회 1997 해양환경안전학회지 Vol.3 No.2

Each factor for the most effective electrolytic reaction in treating shipboard sewage was enhanced by means of batch electrolyitc reactor using DSA electrode. The effective clearance was 6mm and pH was 5-6. In such case, more than 20% of sea water concentration was needed to attain 90% of COD removal rate. The suspended solids was effectively removed by electro-floatation in proportion as charged current density. The nitrogen and posporous were effectively removed in the electrolytic device when mixed seawater.

Proxy Mobile IPv6 기반 차량통신망에서 Local Mobility Anchor간 핸드오버 기법

임유진,안상현,조권희,Lim, Yu-Jin,Ahn, Sang-Hyun,Cho, Kwon-Hee 한국정보처리학회 2010 정보처리학회논문지 C : 정보통신,정보보안 Vol.17 No.3

지능형 교통 시스템(ITS) 구축을 위한 기반 기술 중 하나인 차량통신망은 다수의 차량들이 무선 통신을 기반으로 자율적으로 네트워킹을 형성하는 차세대 네트워킹 기술이다. 현재 차량통신망과 관련된 많은 연구들이 활발히 진행되고 있으며 이 중에서도 특히 차량의 높은 이동성을 지원하기 위한 기법들이 많은 관심을 받고 있다. 기존의 호스트 기반 IP 이동성 관리 기법의 경우 이동성 관리에 따른 부하가 이동 단말에서 야기되는 문제가 있다. 따라서 이와 같은 문제를 해결하기 위해 망 기반 이동성 관리 기법인 PMIPv6(Proxy Mobile IPv6)가 제안되었다. PMIPv6는 단말의 이동성 관리 부하를 줄이고 이동성 관리 지연 시간을 줄임으로써 차세대 이동성 관리 기법으로 많은 주목을 받고 있다. 본 논문에서는 고속의 이동성과 원거리 이동 범위를 가지는 차량통신망에서 PMIPv6 구현을 위한 시나리오를 도출하고 이를 가능하게 하는데 필수적으로 요구되는 LMA(Local Mobility Anchor)간 핸드오버 기법을 제안한다. 또한 ns-2를 이용한 제안 기법의 구현을 통하여 제안 기법의 동작성을 증명하였다. Vehicular communication networking is one of the most important building blocks of Intelligent Transportation System (ITS). The vehicular communication network is a wireless communication system enabling vehicles to communicate with each other as well as with roadside base stations. Mobility management of vehicles which move at high speeds and occasionally make a long journey is an interesting research area of vehicular communication networks. Recently, The Proxy Mobile IPv6 (PMIPv6) protocol is proposed for network-based mobility management to reduce the overhead of mobile nodes. PMIPv6 shifts the burden of the mobility management from mobile nodes to network agents to decrease the overhead and latency for the mobility management. In this paper, we derive the scenario of deploying PMIPv6 in vehicular communication networks and propose a new LMA handover mechanism for realizing the scenario. By carrying out the ns-2 based simulations, we verify the operability of the proposed mechanism.

선박디젤기관용 De-NOx System의 운전성능분석

최재성(J.S.Choi),조권희(K.H.Cho),전효중(H.J.Jeong),진해광(H.K.Jin),임영식(Y.S.Lim) 한국해양대학교 해사산업연구소 1998 海事産業硏究所論文集 Vol.7 No.-

In this paper, the operation performance of De-NOx System for reduction of NOx emission from marine diesel engines, was investigated. The measured data for analysing were obtained from a ship with a emission monitor at sea, which carried hot coil from Pohang in Korea to Pittsburg in U.S.A.. As the results, it seemed that the system performance was good for reducing NOx emission on steady condition. But on transient condition like as during in or out port, it was clear that more improvement should be required for rapid heating method of SCR and transient control system.

상선 기관 손상사고 분석에 관한 연구

최선미(Seon-Mi Choe),조권희(Kwon-Hae Oh),배종옥(Jong-Uk Bae),최재성(Jae-Sung Choi),김정렬(Jung-Ryul Kim) 한국마린엔지니어링학회 2004 한국마린엔지니어링학회 학술대회 논문집 Vol.2004 No.-

Korea is among the world ten sea powers. However, when it comes to maritime safety still remains underdeveloped with 800 marine accidents each year. Marine accidents, in a broad perspective, include all accidents with respect to ships on the sea and ground. There are various causes of marine accidents such as collision, contact, grounding, fire and explosion, sinking, machinery damage, distress, death and injury. In this study, the patterns and causes of marine accidents over the last five years were investigated and the 310 accidents related to engine damage were sorted out and analyzed by engine system, vessel type, vessel age, tonnage group, engine power, engine revolution. The correlation of accidents was studied using the multi-correlation analysis method.

박용디젤기관용 SCR 시스템의 NOx 정화율에 관한 연구

최재성(J.S.Choi),조권희(K.H.Cho),이재현(J.H.Lee),이진욱(J.W.Lee),장성환(S.H.Jang),김정곤(J.G.Kim),양희성(H.S.Yang),고준호(J.H.Ko),박준영(K.Y.Park) 한국마린엔지니어링학회 2003 한국마린엔지니어링학회 학술대회 논문집 Vol.2003 No.-

A diesel engine is utilized widely for industry and shipping because of its efficiency. However, diesel engine emits relatively high concentrated air pollution matters, which will become a competitive factor in the shipping as well as industry. In fact, the regulation has been already implemented from the year 2000. Nitrogen oxides (NOx) in particular is the main part of the regulation. IMO NOx levels are generally possible to meet by means of primary on-engine measures so called IMO tuning. But further significant follow-on reductions are likely to require a secondary after-treatment technique.<br/> SCR technology is used almost exclusively for NOx removal in stationary combustion systems. SCR system is currently the only available technology proven at full scale to meet the 90% NOx reduction levels. Accordingly, the use of an SCR system on board ship maybe provides the solution to minimize this primary pollutant without increasing fuel consumption.<br/> In order to develop a practical SCR system for marine application on board ship, a primary SCR system using urea was made. The SCR system was set up on the ship, HANNARA as a test vessel, employed a two-stroke cycle diesel engine as main propulsion, which is a training ship in KMU (Korea Maritime Univ.). The purpose of this paper is to report the results about the basic effects of the above system parameters which is investigated from practical application through its trial use. The preliminary results are presented that the degree of NOx removal depends on some parameters. such as the amount of urea solution added, space velocity, reaction gas temperature and activity of catalyst.<br/>