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Nanoscale ripples on polymers created by a focused ion beam
Moon, Myoung-Woon,Han, Jun Hyun,Vaziri, Ashkan,Her, Eun Kyu,Oh, Kyu Hwan,Lee, Kwang-Ryeol,Hutchinson, John W IOP Pub 2009 Nanotechnology Vol.20 No.11
<P>We show that focused ion beam irradiation results in the creation of peculiar one- and two-dimensional nanoscale features on the surface of polyimide—a common polymer in electronics, large scale structures, and the automobile industry, as well as in biomedical applications. The role of ion beam incident angle, acceleration voltage, and fluence on the morphology of the structural features is systematically investigated, and insights into the mechanisms of formation of these nanoscale features are provided. Moreover, by using the maskless patterning method of the focused ion beam system, we have developed a robust technique for controlled modification of the polymeric surface. The technique, which is analogous to using a gray glass with varying darkness to control the radiation from the sun, but at a much smaller scale, enables the ion intensity and angle to be controlled at each surface point of the polymer, giving rise to structural surface features with desired shape and morphology. </P>
Moon, Myoung-Woon,Cha, Tae-Gon,Lee, Kwang-Ryeol,Vaziri, Ashkan,Kim, Ho-Young Royal Society of Chemistry 2010 Soft matter Vol.6 No.16
<P>Asymmetric adhesion is used by many insects and gecko lizards, allowing them to move on nearly any surface – horizontal, tilted or vertical. The feet of many of these creatures is covered with intricate fibrillar structures that are responsible for their superb manoeuvring ability. Among these creatures, gecko lizards have one of the most efficient and interesting adhesion devices consisting of finely angled arrays of branched fibers (setae). Here, we developed a method to create tilted Janus (two-face) micropillars on the surface of an elastomeric polymer to mimic the geometry of a gecko's footpad. The method combines soft lithography to create straight micropillars and ion beam irradiation to tilt the straight micropillars in a controlled fashion. A set of experiments were performed to measure the adhesion and friction characteristics of the fabricated tilted micropillars. Our experiments showed that the friction force along the tilting direction is approximately three times higher than the friction force associated with the sliding against the tilting direction of tilted micropillars due to the difference in the contact area during sliding of a glass ball.</P> <P>Graphic Abstract</P><P>A simple technique for the fabrication of tilted polymer micropillars that mimics geckos’ footpad structure was demonstrated by exposing straight micropillars to an Ar ion beam. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0sm00126k'> </P>
문명운(Myoung-Woon Moon),차태곤(Tae-Gon Cha),이광렬(Kwang-Ryeol Lee),Ashkan Vaziri,김호영(Ho-Young Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Inspired by the gecko's footpad structure, we developed a method to create tilted micropillars on the surface of an elastomeric polymer mimicking the geometry of gecko's setae. The method combines son lithography to create straight micropillars and ion beam irradiation to tilt the straight micropillars in a controlled fashion. We experimentally quantify the asymmetric adhesion and friction characteristics of the fabricated tilted micropillars as a function of the tilting angles. The tilting angle of the pillars was varied by changing the incident angle and duration of the ion beam irradiation. Potential applications of the developed pattern include non-wetting painting and switchable adhesion essential in wall-climbing robots.
Primary Cutaneous CD4+ Small/Medium-sized Pleomorphic T-cell Lymphoma
정운경 ( Woon Kyong Chung ),김명신 ( Myoung Shin Kim ),강성민 ( Seong Min Kang ),장성은 ( Sung Eun Chang ),이미우 ( Mi Woo Lee ),최지호 ( Jee Ho Choi ),문기찬 ( Kee Chan Moon ) 대한피부과학회 2009 대한피부과학회지 Vol.47 No.3
Primary cutaneous CD4+ small/medium-sized pleomorphic T-cell lymphoma (CSMTCL) is a rare disease constituting 2% of all cutaneous T-cell lymphomas. In most cases, CSMTCL occurs as a solitary lesion and has an indolent course. Here we present a 42-year-old woman with multiple, localized, recurrent, erythematous papules and macules that developed after combination chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisolone (CHOP). (Korean J Dermatol 2009;47(3):338∼342)
하천에 설치된 횡구조물의 영향 및 섬진강 수계의 어류 풍부도 예측
문운기(Woon Ki Moon),노다혜(Da Hye Noh),유재상(Jae Sang Yoo),임오영(O Young Lim),김명철(Myoung Chul Kim),김지혜(Ji Hye Kim),이정민(Jeong Min Lee),김재구(Jai Ku Kim) 응용생태공학회 2022 Ecology and resilient infrastructure Vol.9 No.2
섬진강 수계 210개 지방하천을 대상으로 하천연장과 보 밀도 대비 어류 출현종 현황을 분석하였다. 하천연장에 따른 어류 출현종수는 비선형지수함수 (Nonlinear exponential relationship) 관계를 보였다. 모델에 따른 계수값 (b)은 0.03이며, 결정계수(R²)은 약 59.0%인 것으로 나타났다. 모델식에 따른 예측기대종수는 실제 출현종수와 차이를 보였으며, 대상하천 가운데 약 110개 하천 (약 52.4%)에서 실제 출현종수는 예측기대종수보다 낮게 나타났다. 한편 섬진강 수계 하천에서 나타난 평균 보 밀도는 약 2.7개/㎞였으며, 이는 타 수계 하천과 비교시 월등히 높은 수치였다. 보 밀도 지표 (Index of Weir’s Density, IWD)에 따른 어류출현종수간의 2-DKS 분석 결과 어류 다양성에 영향을 주는 보 밀도 역치값 (Threshold value)은 약 2.5개/㎞인 것으로 나타났다 (Dmax=0.048, p<0.05). 실제 보 밀도 지표가 역치값 이상인 경우 어류 출현종수 대비 기대 종수비율은 70% 미만으로 낮아졌다. 따라서, 향후 수생태계 연속성 확보를 위한 보 밀도는 역치값 이하로 관리하는 것이 필요하다. The relationships between river length and weir density versus fish species observed were analyzed for 210 local rivers in the Seomjin River system (SJR). A nonlinear exponential relationship between river length and number of fish species were observed. Model coefficient was 0.03 and coefficient of determinant (R²) was 0.59, meaning that about 59.0% of total variance was explained by river length variable. Predicted value by model and observed number of species showed a difference. About 110 local rivers (about 52.4%) showed lower value than predictive value. The average index of weir’s density (IWD) in the SJR was about 2.7/㎞, which was significantly higher than that of other river basins. As a result of nonparametric 2-Kimensional Kolmogorov-Smirnov (2-DKS) analysis based on the IWD, the threshold value affecting fish diversity was about 2.5/㎞ (Dmax=0.048, p<0.05). Above the threshold value, it means that the number of fish species would be decreased. In fact, the ratio of the expected species to the observed species was lowered to less than 70%, when the IWD is higher than the threshold value. To maintain aquatic ecological connectivity in future, it is necessary to manage IWD below the threshold value.