구내 표준 방사선사진을 이용한 구내방사선촬영기의 선질 평가

이상섭,권혁락,심우현,오승현,이지연,전국진,김기덕,박창서 대한구강악안면방사선학회 2000 Imaging Science in Dentistry Vol.30 No.3

Purpose : This study was to evaluate the beam quality of intraoral X-ray equipments used at Yonsei University Dental Hospital (YUDH) using the half value layer (HVL) and the characteristic curve of intraoral standard X-ray film. Materials and Methods : The study was done using the intraoral X-ray equipments used at each clinical department at YUDH. Aluminum filter was used to determine the HVL. Intraoral standard film was used to get the characteristic curve of each intraoral X-ray equipment. Results : Most of the HVLs of intraoral X-ray equipments were higher than the least recommended thickness, but the REX 601 model used at the operative dentistry department and the X-707 model used at the pediatric dentistry department had HVLs lower than the recommended thickness. The slopes of the characteristic curves of films taken using the PANPAS 601 model and REX 601 model at operative dentistry department, the X-705 model of prosthodontic dentistry department, and the REX601 model at the student clinic were relatively low. Conclusion : HVL and the characteristic curve of X-ray film can be used to evaluate the beam quality of intraoral X-ray equipment. In order to get the best X-ray films with the least radiation exposure to patients and best diagnostic information in clinical dentistry, X-ray equipment should be managed in the planned and organized fashion. (Korean J Oral Maxillofac Radiol 2000; 30: 183-188)

낙설증후군의 임상양상

장우혁(Woo Hyok Chang),차순철(Soon Cheol Cha) 대한안과학회 2000 대한안과학회지 Vol.41 No.8

황반부를 침범한 열공망막박리 수술 후의 시력예후

장우혁(Woo Hyok Chang),박영훈(Young Hoon Park) 대한안과학회 2000 대한안과학회지 Vol.41 No.2

상안검 및 하안검 견축의 수술효과

장우혁(Woo Hyok Chang),정화선(Wha Sun Chung) 대한안과학회 2001 대한안과학회지 Vol.42 No.1

한반도 동남부 제3기 어일분지 및 와읍분지의 지구조 운동

장태우 ( Tae Woo Chang ),정재혁 ( Jae Hyok Jeong ),장천중 ( Chun Joong Chang ) 대한지질공학회 2007 지질공학 Vol.17 No.1

한반도 동남부의 제3기 어일분지와 와읍분지를 대상으로 층서를 검토하고, 단층 이동자료 분석을 통하여 분지의 생성 및 진화와 연관이 있는 지구조사건의 과정을 살펴보고자 하였다. 어일분지와 와읍분지는 거의 동시에 각각 별개로 형성되어 제3기 지층들로 충전된 것으로 판단된다. 어일분지와 와읍분지를 충전하고 있는 제3기 지층의 지층단위 분류와 상호관계가 부분적으로 기존 층서와 달라 새롭게 지층명을 첨삭하였다. 어일분지의 장기층군을 하부로부터 감포역암, 홍덕현무암, 노동리역암, 연당현무암으로 분류하였으며, 와읍분지의 범곡리층군을 와읍리응회암, 안동리역암, 용동리응회암, 호암리화산각력암으로 분류하였다. 기반암과 제3기 지층의 11개 지점에서 단층면상 미끄럼선이 발달하는 소단층들의 자료를 수집하여 고응력장을 해석하고, 순서별로 (I) 북서-남동 횡인장, (II) 북서-남동 횡압축 (III) 북동-남서 순수 인장, (IV)남-북 내지 북북동-남남서 횡압축, (V)동-서 내지 동북동-서남서 순수 압축이 작용한 지구조 사건들로 구분하고, 제3기분지 진화와 연관하여 해석하였다. 지구조사건 I은 올리고세 후기 내지 마이오세 초기의 동해 생성과 관련하여 제3기분지의 형성과 발달을 주도하였고, 지구조사건 II, III, IV는 필리핀해판의 섭입경사 및 방향 변화와 관련된 사건으로 본 연구지역에서는 분지 발달의 종료 및 지각 융기를 야기시켰으며, 지구조사건 V는 태평양판의 강한 섭입으로 인한 압축응력이 동해안을 융기시키며 현재까지 지속되고 있는 것으로 해석된다. Stratigraphy has been renewedly set up and the evolution of tectonic events related to basin formation has been examined on the basis of fault-slip data analysis in the Tertiary Eoil and Waeup basins of the southeastern part of Korea. First of all, field mapping was carried out in detail for Tertiary formations and then paleostress analysis were peformed with more than 400 fault slip data collected from 11 sites in the Tertiary formations and the Yucheon Group. It is judged that both the Eoil and Waeup basins filled up with Tertiary deposits might be simultaneously formed in separate locations. The Janggi Group in the Eoil basin is divided into following stratigraphic units in ascending order: Gampo Conglomerte, Hongdeok Basalt, Nodongri Conglomerate and Yeondang Basalt, and the Bomkori Group in the Waeup basin: Waeupri Tuff, Andongri Conglomerate, Yongdongri Tuff and Hoamri Volcanic Breccia. Paleostress analysis by using striated faults reveals five sequential tectonic events: (1) NW-SE transtension (event I), (2) NW-SE transpression (event II), (3) NE-SW pure extension (event III), (4) N-S transpression (event IV) and (5) E-W pure cmpression (event V). Therefore, five sequential tectonic movements are closely associated with the formation and evolution of the Tertiary basins in the study area: tectonic event I of NW-SE extension is related to formation of the Tertiary basins during the late Oligocene to the Early Miocene, tectonic events II, III and IV caused the termination of the Tertiary basin opening and the crustal uplift in the study area, and tectonic event V upheaved the east coast of Korean Peninsula with compressive stress due to intense subduction of the Pacific plate into Asian continent since the Early Pliocene.

망막하증식띠가 동반된 열공망막박리에서 공막돌륭술의 수술성적

박찬수 ( Chan Soo Park ) , 장우혁 ( Woo Hyok Chang ) , 차순철 ( Soon Cheol Cha ) , 박영훈 ( Young Hoon Park ) 대한안과학회 2004 대한안과학회지 Vol.45 No.7

Microstructure and CTOD (crack tip opening displacement) of Deposit Weld Metal in 30 mm Thick Plate

Lee Hae-Woo,Kim Hyok-Ju,Park Jeong-Ung,Kang Chang-Yong,Sung Jang-Hyun Materials Research Society of Korea 2004 한국재료학회지 Vol.14 No.9

The microstructure and crack tip opening displacement (CTOD) of deposit weld metal were investigated for a 30 mm- thick plate welded with flux cored arc welding (FCAW) and submerged arc welding (SAW) processes. The CTOD test was carried out both as welded condition and as stress-relieved specimen by local compression. The crack growth rates in FCAW were faster than those in a SAW, and the acicular ferrite content by the SAW process was increased relatively more than that by the FCAW process. The fatigue crack growth rate in a welded specimen was faster than that in locally compressed specimen. The CTOD value of locally compressed specimens was lower than that of as welded specimen. Furthermore, the CTOD value tested with the SAW process was higher than that tested with the FCAW process.

간헐 압축응력완하 시헙법을 이용한 아크릴로니트릴 고무 오링의 수명 예측 연구

이진혁(Jin Hyok Lee),배종우(Jong Woo Bae),김재일(Zaeill Kim),최창선(Chang Sum Choi),조남주(Nam-ju Jo) 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.11

Intermittent CSR 측정법을 이용하여 NBR 오링의 노화 거동과 수명 예측에 관하여 연구하였다. Intermittent CSR jig는 오링의 실제 사용 환경을 고려하여 설계 제작하였다. 오링의 노화 거동은 80~100℃에서의 가속 노화 연구를 통하여 관찰하였다. 오링은 선형 노화 거동을 나타내었으며, Arrhenius relationship을 만족시켰다. 이때의 활성화 에너지는 66.8 kJ/mol로 나타났다. Arrhenius plot으로 부터, 오링의 예측 수명은 고장 조건 10%에 대하여 21.0 년으로 나타났다. Intermittent CSR testing was used to investigate the degradation of a NBR O-ring, and also the prediction of its life-time. An intermittent CSR jig was designed taking into consideration the O-ring’s environment under use. Degradation of O-rings by thermal aging was observed between 80 and 100 ℃. O-rings showed linear degradation behavior and satisfied the Arrhenius relationship. The activation energy was about 66.8 kJ/mol. From Arrhenius plots, predicted life-times were 21.0 years for 10% failure conditions, respectively.

선천 백내장 수술 후 발생한 망막박리

김재우,장우혁.Jae-Woo Kim. M.D.. Woo-Hyok Chang. M.D. 대한안과학회 2005 대한안과학회지 Vol.46 No.11

Purpose: To analyze the preoperative clinical characteristics, surgical methods, outcomes and visual prognosis of retinal detachment following congenital cataract surgery. Methods: We retrospectively analyzed the medical records of 16 patients (16 eyes) who had undergone an operation for retinal detachment following congenital cataract surgery. Anatomical success was considered to have occurred if the retina was well attached in fundus exam at postoperative 6 months. Results: There were more male (81.3%) patients than female patients. The average age of cataract surgery was 19.3 years, and the mean interval between cataract surgery and retinal detachment was 7.7 years. The most common type of the retinal break was a round hole and the most common location of retinal break was the inferotemporal quadrant. Total retinal detachment was 56.2% and the macula was detached in 87.5% of patients. The anatomical success rate of the primary operation was 43.8% and the final success rate was 87.5%. Postoperative visual acuity increased in 43.8% of patients. Conclusions: Retinal detachment following congenital cataract surgery had a poor success rate compared to that of other retinal detachments due to difficulties in finding the retinal break (37.5%) and frequent total retinal detachment. Early diagnosis, prompt surgery, vitrectomy and intraocular tamponade for primary operation would increase the success rate and improve postoperative visual prognosis.

A Case of Valsalva Retinopathy Associated with Straining at Stool

( Tae Yoon Lee ),( Woo Hyok Chang ) 영남대학교 기초/임상의학연구소 2006 Yeungnam University Journal of Medicine Vol.23 No.2

The Valsalva maneuver is described as an expiratory effort against a closed glottis or airway. It leads to elevation of retinal venous pressure and may result in retinal hemorrhage. A fifty two- year-old man presented with an acute reduction of central visual acuity in his right eye which occurred after considerable straining at stool. Detailed past medical history revealed that he suffered from chronic constipation and hypertension. There were one disc sized subhyaloid hemorrhage and three small intraretinal hemorrhages around the fovea at the dilated fundus examination. After three months of follow-up without any treatment, the retinal hemorrhages resolved without any sequelae. Here we report a patient with sudden visual loss and retinal hemorrhage.