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- 저자 : 황준(Joon Hwang) (검색결과 68 건)
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황준서(Joon Seo Hwang),유형곤(Hyeong Gon Yu) 대한검안학회 2012 Annals of optometry and contact lens Vol.11 No.1
목적: 한국인 망막색소변성 환자의 초진 시 시야장애를 평가하고자 한다. 대상과 방법: 망막색소변성 환자의 초진 시 시야, 시력장애의 분포와 유전양상에 따른 차이를 분석하였다. 결과: 총 400명의 환자의 유전양상은 상염색체우성 17.0%, 상염색체열성 11.0%, X-연관열성 3.5%, 단순형 68.0%였다. 잔존시야가 반경 50o 이상인 환자가 7.3%, 25∼50o가 10.8%, 10∼25o가 29.3%, 10o 미만(World Health Organization 분류: 심한 저시력)이 52.8%였다. 중심시력은 20/30 이상이 43.8%, 20/100∼20/30이 44.5%, 20/200∼20/100이 5.5%, 20/200 미만(심한 저시력)이 6.3%으로, 중심시력저하가 시야장애에 비해 경하였다. 유전양상에 따른 장애는 상염색체열성과 X-연관열성에서 심해, 반경 25o 이상의 잔존시야를 보이는 경우가 없었고, 20/30 이상인 시력을 가지는 비율도 낮았다(15.2%, 35.7%). 결론: 한국인 망막색소변성 환자는 초진 시 진행된 시야장애를 보이고, 시야장애가 중심시력저하보다 심하였다. 상염색체열성과 X-연관열성 환자에서 상염색체 우성과 단순형에 비해 더 진행된 시야장애를 나타내었다. Purpose: To evaluate visual field defect of Korean patients with retinitis pigmentosa (RP). Methods: A total of 400 patients with RP who were diagnosed within 3 years, 231 males and 169 females were included in this study. Data were collected including age, symptomatic disease duration, family history, visual acuity (VA), Goldmann visual field (VF) at the initial visit. Results: Determination of inheritance pattern revealed 17.0% autosomal dominant RP cases, 11.5% autosomal recessive (AR) RP, 3.5% X-linked recessive (XL) RP, and 68.0% simplex RP, indicating a relative small proportion of AR RP cases. The remaining visual filed was ≥50o (radius) in 7.3%, 25∼50o in 10.8%, 10∼25o in 29.3% and ≤10o in 52.8%. Visual acuity was ≥20/30 in 43.8%, 20/100∼20/30 in 44.5%, 20/200~20/100 in 5.5% and ≤20/200 in 6.3%. The functional acuity score of 83.3±17.2 was higher than the functional field score of 49.9±20.5. VA and VF defects were greater in AR RP and XL RP than in other types, the proportion of ≥20/30 VA was smaller and there was no patient who had VF greater than 25o. Conclusions: Korean RP patients had advanced visual field defect at the initial visit. VF defect was greater than VA loss and more severe in the patient with AR RP and XL RP.
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황준,Hwang, Joon 한국결정성장학회 2014 韓國結晶成長學會誌 Vol.24 No.6
가공정밀도 요구특성의 지속적인 향상에도 불구하고, 공작기계와 절삭공구를 이용한 절삭가공공정에서의 채터진동은 아직도 개선의 여지가 많이 남아있다. 특히, 더욱 고속화, 고정밀화 되고 있는 가공현장에서 채터진동의 효과적인 감소대책에 대한 다양한 연구가 필요하다. 본 연구에서는 이러한 문제점을 해결하기 위해 고정밀 공구동력계를 이용한 실시간 절삭력 측정과 유한요소해석 방법을 이용해 사용 빈도와 활용이 매우 큰 터닝센터(turning center)에서 폭넓게 적용되고 있는 3종의 절삭공구 툴링에서의 채터진동 특성을 평가하여, 공구형상 및 툴링 특성에 따른 채터진동과의 상관성을 연구하고, 향후 채터진동 저감형 공구개발을 위한 근간 기술자료로 활용코자 한다. Machining performance is often limited by chatter vibration at the tool-workpiece interface. Chatter vibration is a type of machining self-excited vibration which originated from the variation in cutting forces and the flexibility of the machine tool structure. Cutting tooling method is one of major factor to chatter vibration in turning process. Even though lots of cutting tooling methods are developed and used in machining process, precise analysis of cutting tooling effect in view of chatter vibration behavior. This study presents numerical and experimental approaches to verify and effects of various cutting tooling geometry and clamping method on the onset of chatter vibration. Acquired knowledge from this study will apply the optimal geometry design of cutting tooling and adjusting of machining process.
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황준서,한영근,권지원.Joon Seo Hwang. M.D.. Young Keun Han. M.D... Ji Won Kwon. M.D.. 대한안과학회 2007 대한안과학회지 Vol.48 No.7
Purpose: To report the successful application of a Keplerian telescope in a low vision patient whose visual acuity was counting fingers, which is typically a difficult range for LVA adaptation. Methods: We used telescopes, distance low vision devices, in a 36-year-old man whose visual acuity, because of congenital corneal opacity, was limited to hand movement in his left eye and to counting fingers in his right eye. The objective was to improve his ability to participate in outdoor activities. Results: Even though the patient`s visual acuity was seemingly beyond improvement, his visual acuity was improved to the level of 20/100 with a distance low vision device, a Keplerian telescope 8×30. Conclusions: In the case of patients whose visual acuity is worse than counting fingers, it is usually difficult to improve poor vision by using telescopes for distance. However, in spite of restricted adaptation, low vision telescopes can be used to produce good results in low vision patients.
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황준,이원국,Hwang, Joon,Lee, Won-Kuk 한국결정성장학회 2016 한국결정성장학회지 Vol.26 No.1
엔드밀링 공정은 3차원 형상의 다양한 부품, 제품, 금형을 가공하는데 널리 사용되고 있는 핵심 가공 프로세스이다. 가공정밀도 요구수준과 가공형상 난이도 수준이 날로 높아짐에 따라 가공정밀도 요구특성의 지속적인 향상에도 불구하고, 공작기계와 절삭공구를 이용한 절삭가공공정에서의 채터 진동은 아직도 개선의 여지가 많이 남아있다. 특히, 더욱 고속화, 고정밀화 되고 있는 가공현장에서 채터진동의 효과적인 감소대책에 대한 다양한 연구가 필요하다. 본 연구에서는 이러한 문제점을 해결하기 위해 엔드밀링공정에서 발생하기 쉬운 채터진동의 안정성을 향상시키기 위해 절삭모델에 근거한 채터진동 안정성 시뮬레이션 방법론을 연구하고, 엔드밀링 절삭조건이 채터진동에 미치는 영향을 다양한 조건하에서 예측하고자 하였다. 본 연구결과를 더욱 발전시켜 채터진동과의 상관성을 연구하고, 향후 채터진동 저감형 가공시스템 개발을 위한 근간 기술자료로 활용코자 한다. End milling process is one of the broadly used manufacturing process for precision machined parts and products. Machining performance is often limited by chatter vibration at the tool-workpiece interface. Chatter vibration is a type of machining self-excited vibration which originated from the variation in cutting forces and the flexibility of the machine tool structure. Even though lots of cutting tooling methods are developed and used in machining process, precise analysis of cutting tooling effect in view of chatter vibration behavior. This study presents numerical and experimental approaches to verify and effects of various cutting parameters to affect to chatter vibration stability. Acquired knowledge from this study will apply the optimal cutting conditions to improve a machining process.
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부분결합간섭계와 초음파를 이용한 안축장 측정시 백내장 수술 후 굴절력 예측의 비교
황준서,이진학.Joon Seo Hwang. M.D... Jin Hak Lee. M.D.. 대한안과학회 2007 대한안과학회지 Vol.48 No.1
Purpose: To study the refractive outcome of cataract surgery employing partial coherence interferometry (PCI) and to compare this outcome with that of A-scan ultrasound in a prospective study of 96 eyes of 96 patients that underwent phacoemulsification with intraocular lens (IOL) implantation. Methods: The SRK-T formula was employed, using PCI (IOL Master?: the only commercially available model) and A-scan ultrasound data, to predict patients` implanted IOL power. Four to six weeks after cataract surgery, the refractive outcome was determined, and results from the two different biometry methods were compared. Results: Ninety-six patients (mean age: 67.64, SD: 9.91) underwent phacoemulsification with IOL implantation. The optical axial length obtained using the IOL Master? was significantly longer (p<0.001, Student??s t-test) than the axial length obtained via by A-scan ultrasound, 24.29 (SD 1.80) mm vs. 24.19 (1.75) mm. When using the IOL Master?, the mean prediction error (PE; planned target of refraction - postoperative refraction) was 0.30 (0.60) D, and the mean absolute prediction error (APE) was 0.51 (0.44) D. When using A-scan ultrasound, the mean PE was 0.01 (0.64) D, and the mean APE was 0.47 (0.43) D. The difference in mean APE between the two biometry methods was not statistically significant (p=0.236, Wilcoxon signed rank test). Among the eyes with an axial length greater than 25 mm, as determined by A-scan ultrasound, the difference in the mean APE was not statistically significant (0.48 (0.87) vs. 0.58 (0.61), p=0.094). Likewise, among the eyes for which with axial length measured by A-scan ultrasound longer than IOL Master?, the difference in the mean APE error was not statistically significant, (0.33 (0.30) vs. 0.46 (0.41), p=0.110). Conclusions: IOL power calculation using the PCI is as accurate as that using A-scan ultrasound for predicting the postoperative refractive state of patients who have undergone cataract surgery.
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황준서,김정훈,정호경,허장원,김성준,유영석.Joon Seo Hwang. M.D... Jeong Hun Kim. M.D... Ho Kyung Choung. M.D... Jang Won Heo. M.D... Seong-Joon Kim. M.D... Young Suk Yu. M.D.. 대한안과학회 2007 대한안과학회지 Vol.48 No.9
Purpose: To study the clinical characteristics and visual prognosis of Leber’s congenital amaurosis in Korea. Methods: Children who were diagnosed with Leber`s congenital amaurosis at Seoul Natioanl University Children`s Hospital between 1992 and 2004, were included in this study. The medical records pertaining to the clinical characteristics and visual outcomes of the patients were retrospectively reviewed. Results: The mean age of the patients at presentation and during the subsequent follow-up period was 15.5 and 62.7 months, respectively. The principal symptoms included lack of fixation (69.0%) and nystagmus (23.8%). At first observation, nystagmus was found in 40 patients, and the appearance of the fundi were variable, including `normal` (23.8%), pigmentary degeneration (54.8%), vascular attenuation (35.7%) and macular coloboma (19.0%). At the age of three to five years, 44.4% of patients had hyperopia greater than +5D. At the time of last follow-up, the visual acuities of the patients who were examined after the age of four were `hand motion` in 68.7%, ≥20/400 in 9.4%. No patient had visual acuity better than 20/200. Eight (25%) patients could read with glasses or low-vision aids. Conclusions: The visual prognosis of patients with Leber’s congenital amaurosis was poor in most cases, but a majority of our patients displayed a stable clinical course. Progression was rare, and one fourth of the patients were able to read with appropriate aides. In conclusion, regular follow-up care to assess visual function is necessary for optimal outcomes.
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