금형주조한 Al-10%Si 합금의 응고조직과 기계적 성질에 미치는 금형의 냉각효과에 관한 연구

이동윤,천병욱,최창옥 ( Dong Youn Lee,Byung Wook Cheon,Chang Ock Choi ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.2

N/A This study has been focused on the influence of the metallic mold cooling effects on the solidification structures and the mechanical properties for Al-10%Si alloy castings by the variation of pouring temperatures, metallic mold temperatures and Cooling part of metallic mold. The dendrite arm spacing of Al-10%Si alloy was decreased with increasing cooling rate. In case of bottom cooling of metallic mold, DAS was appeared to be 20-22㎛ and in the middle cooling, it was increased to 36-40㎛. The DAS decreased proportionally with(cooling rate)^(-3/2) at pouring temperatures 680℃ and (cooling rate)^(-½) at pouring temperature 760℃, but it was proportionally increased to(local solidification time)^(½-⅓) at pouring temperature 680℃ and 760℃. The maximum tensile strength of Al-10%Si alloy casting was obtained in case of bottom cooling of mold at pouring temperature 680℃ and metallic mold temperature 320℃.

Landsat TM 위성영상 픽셀 기반의 녹지 연계망 평가

이동윤,엄정섭,Lee, Dong-Youn,Um, Jung-Sup 한국공간정보학회 2010 한국공간정보학회지 Vol.18 No.2

현재 녹지 연결성 조사는 대부분 현지조사에 의존하고 있어, 특정시기의 특정지점에서 조사된 결과에 주안점을 두고 있다. 그리하여 조사지점의 대표성에 한계가 있고 많은 시간이 소요되고, 조사 대상물 위치의 부정확, 경제적 비효용 등이 문제점으로 지적되어왔다. 본 연구는 이러한 문제에 대한 대안을 제시하기 위해 Landsat TM (Thematic Mapper) 영상의 픽셀에 의거한 녹지 연계망을 평가하고자 출발하였다. 그리하여 원격탐사 기법이 녹지 연계망을 평가할 수 있는 도구로서의 가능성을 지니고 있는 지를 평가하고자 특정 사례 연구지역에 대해 실증적인 연구가 수행되었다. 조사지점에만 국한된 현지조사 방식과 달리 픽셀 기반의 평가는 광역적인 녹지 연계망의 분포실태를 단시간에 제시하였다. 녹지 연계망 훼손 추세 평가는 다양한 시기의 녹지 변화 실태를 정량적으로 제시하고 있기 때문에 그 결과가 녹지 연계망 보전과정에서 설득력을 지닌 근거자료로 활용될 수 있을 것으로 판단된다. 본 연구가 녹지 연계망 감시에서 객관적인 데이터에 의거한 정책결정이 아닌 직관에 의존하여 왔던 관행을 개선될 수 있는 계기가 되어 향후 녹지 연계망 보전관련 중요한 참고자료가 될 수 있을 것으로 사료된다. At present, monitoring programmes for green network have been mainly based on field sampling, which relies on attributes of an area at one point in time, reflecting an emphasis on the small number of in-situ data. One of the major disadvantages of traditional field monitoring is that it is costly, laborious and time consuming due to the large number of samples required. The aim of this research was to evaluate green network based on pixel of Landsat TM satellite image. An empirical study for a case study site was conducted to demonstrate how a standard remote sensing technology can be used to assist in monitoring the green network based on pixel. The pixel-based analysis made it possible to identify area-wide patterns of green network subject to many different type of artificial structures, which cannot be acquired by traditional field sampling. It was demonstrated that the degradation trends of green network could be used effectively as an indicator to restrict further development of the sites since the quantitative data generated from remote sensing can present area-wide visual evidences by permanent record. It is anticipated that this research output could be used as a valuable reference to support more scientific and objective decision-making in monitoring green network.

Diagnosis of subungual melanoma

이동윤 ( Dong Youn Lee ) 대한피부과학회 2013 대한피부과학회 학술발표대회집 Vol.65 No.2

Subungual melanoma (SUM) is a rare variant of melanoma. However, in Korea the proportion of SUM is relatively high. It is difficult to differentiate it histopathologically from benign melanonychia, especially in the early stage. Due to its delayed diagnosis, SUM showed a poor prognosis. SUM was generally treated with amputation of the affected digits. Recently, there have been several reports about non-amputative conservative treatment when SUM was in situ or the depth of dermal invasion in SUM was low. SUM usually originates from the nail matrix. As the SUM progresses, a pigmentation of the nail fold and/or the hyponychium (Hutchinson`s sign) and nail dystrophyoccur. SUM may be suspected clinically when there is a wide (>3mm) changing pigment band in a single nail. Dermoscopic examination may reveal more details showing pigmented lines of varying color, width and spacing. These lines tend to lose their tendency to run parallel to each other along the length of the nail. The diagnosis of SUM is confirmed by punch biopsy, longitudinal biopsy or matrix shave biopsy.

Segmental vitiligo treatment: past, present, and future

이동윤 ( Dong-youn Lee ) 대한피부과학회 2016 대한피부과학회 학술발표대회집 Vol.68 No.2

Compared with non-segmental vitiligo (NSV) segmental vitiligo (SV) is a distinct type of vitiligo in terms of its clinical features, natural course, and response to treatment. In SV, white macules are usually localized to one segment on only one side of the body, however, in NSV white macules can occur at any body location and disease activity tends to persist throughout the life of the patient. Thus, the course of SV seems to be predictable while that of NSV is unpredictable. Treatment guidelines of SV may be easier to determine than those of NSV. The treatment modalities for vitiligo largely consist of medical and surgical treatments. Medical management includes topical corticosteroids and immunomodulators, and phototherapy such as narrow-band UVB (NB-UVB) and excimer laser. If medical treatment is unsatisfactory, surgical treatments such as autologous epidermal grafting can be considered. Based on previous reports and our experiences, we proposed a set of treatment guidelines in SV. Treatments such as topical corticosteroids and topical calcineurin inhibitors, as well as phototherapy, including NB-UVB and excimer laser are helpful for SV. Combination of topical treatment and phototherapy seems to be more efficacious in SV. In addition, disease duration in SV is important to predict the response to medical treatment. Thus, as first-line therapy, we recommend the combination of topical treatment and phototherapy to be initiated as early as possible. If medical treatment is not effective any more, surgical treatment needs to be considered. In addition, our experience suggests that phototherapy is not helpful in SV patients with the majority of hairs in lesional skin being white. In these cases, surgery can be considered in order to avoid delay as well as unnecessary and inefficacious treatment.

Updates in Dermatology (UD 2) : Melanonychia: Dx and DDX

이동윤 ( Dong Youn Lee ) 대한피부과학회 2015 대한피부과학회 학술발표대회집 Vol.67 No.1

Melanonychia is defined as a brown or black pigmentation on a fingernail or toenail. It may be due to exogenous pigments, including fungi, bacteria such as Pseudomonas aeruginosa, and blood. In these cases, the clinical feature is variable according to its cause. A thorough history, dermoscopy of nail plate, direct examination of nail scales, and cultures for fungi and bacteria may be helpful in the diagnosis. Melanonychia, which is caused by melanin produced by the nail matrix, is seen as a longitudinal band. It is called longitudinal melanonychia. Longitudinal melanonychia is caused by nevi of the nail matrix, nail matrix lentigo, and an activation of the nail matrix melanocytes. Most importantly, longitudinal melanonychia, especially in adults may indicate an early stage of subungual melanoma.

Symposium 5-3 (SYP 5-3) : Current status of nail unit melanoma diagnosis and management

이동윤 ( Dong Youn Lee ) 대한피부과학회 2015 대한피부과학회 학술발표대회집 Vol.67 No.1

Nail unit melanoma (NUM) is frequently misdiagnosed clinically and histopathologically in its early stage. The diagnostic delay often results in invasive melanoma that might lead to poor prognosis, usually requiring amputation of the affected digit. The reasons for delayed diagnosis of NUM include lack of early recognition of this entity clinically, difficulties in performing satisfactory biopsies of subungual lesions, and histopathologic misinterpretation of biopsies in early lesions of NUM. The therapeutic consequences of misdiagnosis may be disastrous and have medico-legal problems. Subungual melanoma (SUM) usually originates from the nail matrix and spreads to the surrounding nail bed, hyponychium, and proximal nail fold. Pigmentation of the nail fold and/or the hyponychium is called Hutchinson’s sign, which may be an important clinical clue for SUM. To make an early diagnosis of SUM in situ the identification of the early histopathological findings of SUM in the nail matrix is necessary. However, the histopathological diagnosis of SUM in situ is very difficult in its early stage because the changes may be quite subtle. Also, small biopsy sample from the nail tissue is another important factor for the diagnostic difficulties. Thus, SUM is often misdiagnosed as other subungual melanocytic lesions such as subungual lentigo and nevus. Previously, amputation at the distal phalangeal joint was generally regarded as the surgical treatment of choice for SUM. Recently, however, some authors have suggested a non-amputative conservative treatment of SUM to preserve the phalangeal bone for in situ or thin lesions of SUM. Our recent data about the late tendency of dermal invasion in the nail matrix area support for non-amputative conservative surgery in early SUM.

Nail lesion in a 62-year-old women

이동윤 ( Dong-youn Lee ) 대한피부과학회 2017 대한피부과학회 학술발표대회집 Vol.69 No.1

She presented with a nail dystrophy on the right thumb for 10 years. Previously, triamcinolone intralesional injection was not effective. Nail examination showed an asymptomatic longitudinal yellow band and thickened, transverse overcurved nail plate on her right 1st fingernail. After nail avulsion, biopsy was performed.

Evaluation of nail plate for the diagnosis of nail disorders

이동윤 ( Dong-youn Lee ) 대한피부과학회 2017 대한피부과학회 학술발표대회집 Vol.69 No.1

Nail clipping is a simple, minimally invasive method for the diagnosis of several nail diseases. Histological examination with periodic acid-Schiff staining (PAS) of nail clippings is very useful in the diagnosis of onychomycosis. Detection of fungal elements (hyphae) is possible in most of onychomycosis cases. This test is most sensitive single test for the diagnosis of onychomycosis compared with fungus culture and direct microscopy. Histologic analysis of nail plate is helpful for the evaluation of melanonychia. In some cases of subungual melanoma, nail clippings or extracted nail shows the presence of melanoma cells within the nail plate. Nail clipping is also very useful method for the diagnosis of onychomatricoma. On nail clippings, onychomatricoma shows a thickened nail plate having lacunae of different sizes and shapes filled with serous fluid.

Leukotrichia in vitiligo: treatment implication

이동윤 ( Dong-youn Lee ) 대한피부과학회 2017 대한피부과학회 학술발표대회집 Vol.69 No.2

Symposium 8-4 (SYP 8-4) : How to manage segmental vitiligo effectively to obtain better outcome?

이동윤 ( Dong Youn Lee ) 대한피부과학회 2014 대한피부과학회 학술발표대회집 Vol.66 No.2

Segmental vitiligo (SV) is a distinct type of vitiligo in terms of its clinical features, natural course, and response to treatment, that make it distinguishable from non-segmental vitiligo (NSV). In SV, white macules are usually localized to one segment on only one side of the body, however, in NSV white macules can occur at any body location and disease activity tends to persist throughout the lifeof the patient. Thus, the course of SV is predictable while that of NSV is unpredictable. Treatment guidelines of SV may be easier to determine than those of NSV. The treatment modalities for vitiligo largely consist of medical and surgical therapies. Medical management includes topical corticosteroids and immunomodulators, and phototherapy such as narrow-band UVB (NB-UVB) and excimer laser. If medical treatment is unsatisfactory, surgical treatments such as autologous epidermal grafting may be considered. Based on previous reports and our experiences, we recently proposed a set of treatment guidelines inSV. Treatments such as topical corticosteroids and topical calcineurin inhibitors, as well as phototherapy, including NB-UVB and excimer laser are helpful for SV. Combination of topical treatment and phototherapy seems to be more efficacious in SV. In addition, disease duration in SV is very important to consider to gauge response to medical treatment. Thus, as first-line therapy, we recommend the combination of topical treatment and phototherapy to be initiated as early as possible. However, our experience suggests that phototherapy is not helpful in SV patients with the majority of hairs in lesional skin being white. Therefore, in these cases, surgery can be considered in order to avoid delay as well as unnecessary and inefficacious treatment.