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2000년대 국내 항공기 사고·준사고 발생유형 사례연구
최영재,안재형,유경인,박정권,Choi, Young-Jae,Ahn, Jae-Hyung,You, Kyung-In,Park, Jung-Gown 한국항공운항학회 2013 한국항공운항학회지 Vol.21 No.4
Since year 2001 to the present time, the aircraft accidents and serious incidents in our country have surpassed 150 occurrences. The Boeing has published the statistical summary of commercial jet airplane accidents annually for the past 10 years on the basis of the occurrence categories defined by the CICTT(CAST/ICAO Common Taxonomy Team), and the number of occurrences is in order of loss of control(LOC-I), controlled flight into terrain(CFIT) and runway excursion (RE). Like the NTSB and the EASA, when fatal and non-fatal accidents are aggregated, though fatality rate is low, abnormal runway contact(ARC), system/component failure(SCF-PP/NP), ground handling(RAMP) rank high in the CICTT occurrence categories. With the less occurrence frequency, it is difficult to statistically analyze the aircraft accidents in our country, thus customarily the accidents and the serious incidents on aggregate are consolidated, and the statistical analysis is performed. This study categorizes the accidents and serious incidents to the domestic transportation aircraft in the past 10 years according to the CICTT occurrence categories, that is compared with foreign practices, and the implications have been discussed. From years 2001 through 2010, the accidents to the domestic transportation aircraft occurred in order of system failure(SCF-NP), ARC and power plant failure(SCF-PP), and when the accidents and the serious incidents are consolidated and analyzed, it is verified that a distribution appears similar to the European accident occurrence categories defined from 300 accident occurrence data.
비강내 누낭비강문합술시 시행한 양막충전술의 단기 임상 결과
최영재,황상준,이태수,Young Jae Choi,Sang Jun Hwang,Tae Soo Lee 대한안과학회 2008 대한안과학회지 Vol.49 No.3
`Purpose: To evaluate the short-term surgical results of Merocel? nasal packing wrapped with human amniotic membrane on the internal ostium during endonasal dacryocystorhinostomy (DCR). Methods: Sixty patients who underwent endonasal DCR to treat nasolacrimal duct obstruction from October 2005 to April 2006 were enrolled in this prospective study. The patients were divided into two groups: 30 patients treated with Merocel? packing wrapped with amniotic membrane were assigned to group 1, and the remaining 30 patients were assigned to group 2. During the follow-up period, the authors evaluated surgical wound healing, the incidence of granuloma, and the patency of the internal ostium. Results: Success rates at 6 months after surgery were higher in group 1 than in group 2, but these rates showed no statistically significant difference between the two groups (group 1: 93.3%, group 2: 86.7%, p=0.67). The time for mean wound healing in group 1 was significantly shorter than that in group 2 (group 1: 4.8±1.5 weeks, group 2: 7.3±1.5 weeks, p<0.001). The incidence of granuloma in group 1 was lower than that in group 2 at 2 months after surgery (group 1: 13% (4/30), group 2:33% (14/30), p=0.04). However, there was no difference of granuloma formation between the two groups at 6 months postoperatively (group 1: 33% (11/30), group 2: 46% (14/30)). Conclusions: The authors believe that the use of Merocel? packing wrapped with amniotic membrane after endonasal DCR might decrease postoperative inflammation, accelerate wound healing, and decrease granuloma formation in the early postoperative period.`
증식당뇨망막병증 환자에서 유리체절제술시 일상적인 내경계막제거술의 효과
최영재,김성우,오인경,오재령,허걸.Young Jae Choi. M.D.. Sung Woo Kim. M.D.. In Kyoung Oh. M.D.. Jaeryung Oh. M.D.. Kuhl Huh. M.D.. Ph.D. 대한안과학회 2008 대한안과학회지 Vol.49 No.4
Purpose: To evaluate the efficacy of internal limiting membrane (ILM) removal during vitrectomy in proliferative diabetic retinopathy (PDR) patients. Methods: Seventy-four eyes of 74 PDR patients who underwent vitrectomy were enrolled. All patients had been followed for at least one year. Thirty-three patients who underwent vitrectomy without ILM peeling from January 2004 to February 2005 were assigned to Group A and 41 patients who underwent vitrectomy with ILM peeling from March 2005 to October 2005 were assigned to Group B. Visual acuity (LogMAR), central macular thickness measured by optical coherent tomography (OCT), and presence or absence of macular edema were compared between the two groups at six months and one year after surgery. Results: Postoperative mean best corrective visual acuity (BCVA; LogMAR) were improved significantly in both groups at six months and one year after surgery. However, the overall amount of improvement in vision was not different between the two groups. The mean central forveal thickness in Group B was significantly thinner than in Group A at six months and one year after surgery. There was no difference between the two groups in macular edema incidence at that time. There were no serious complications in Group B by one year after surgery. Conclusions: There was no difference in visual acuity between the Group A and Group B However, the central forveal thickness measured by OCT was thinner in the ILM peeling group, and there were no serious complications in ILM peeling group. Routine ILM peeling during vitrectomy in PDR will help to maintain the structural stability of the macula postoperatively.
강구조 부재의 피로균열성장에 미치는 제인자에 관한 연구( II ) -표면잔류응력이 균열닫힘에 미치는 영향-
최영재,경갑수,Choi, Young Jae,Kyung, Kab Soo 한국강구조학회 1996 韓國鋼構造學會 論文集 Vol.8 No.3
To investigate the effect of fatigue crack growth due to the surface residual stress, it is measured the residual stress distribution by x-ray diffraction at the crack tip each constant crack growth in the notch specimens, and quantitively assessed the effect of crack closure caused to the distribution of compressive stress at the crack tip from evaluating crack openning stress using the finite element analysis. It is concluded that the degree of the residual stress distribution at the crack tip is decreased with increasing the crack length. From the fact that it is similar to the crack openning stress ratio, it is found that the compressive residual stress distribution and size is related to the crack closure effect and surface residual stress field with propagating crack in the notch specimens depends on the stress intensity factor range at the crack tip.
Tool Wear Monitoring System based on Real-Time Cutting Coefficient Identification
최영재(Young Jae Choi),송기형(Ki Hyeong Song),김재혁(Jae Hyeok Kim),강구선(and Gu Seon Kang) Korean Society for Precision Engineering 2022 한국정밀공학회지 Vol.39 No.12
Among the monitoring technologies in the metal-cutting process, tool wear is the most critical monitoring factor in real machining sites. Extensive studies have been conducted to monitor equipment breakdown in real-time. For example, tool wear prediction studies using cutting force signals and deducting force coefficient values from the cutting process. However, due to many limitations, those wearable monitoring technologies have not been directly adopted in the field. This paper proposes a novel tool wear predictor using the cutting force coefficient with various cutting tools, and its validity evaluates through cutting tests. Tool wear prediction from the cutting force coefficient should conduct in real-time for adoption in real machining sites. Therefore, a real-time calculation algorithm of the cutting force coefficient and a tool wear estimation method proposes, and they compare with actual tool wear in cutting experiments for validation. Validation cutting tests are conducted with carbon steel and titanium, the most commonly used materials in real cutting sites. In future work, validation will be conducted with different materials and cutting tools, considering the application in real machining sites.