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송경환(Kyounghwan Song),정정열(Jung-Yeul Jung),남영석(Youngsuk Nam) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Aluminum is a popular material for various energy and environmental applications including heat exchangers, pipes, space crafts and plant modules. We investigated surface modification techniques for aluminum surfaces in order to improve corrosion resistance of surfaces. We applied various chemical oxidation and vapor deposition schemes to control both the morphological and chemical characteristics of aluminum surfaces. The effects of such modifications on the surface properties were investigated by FE-SEM, EDS and dynamic contact angles were characterized by highprecision goniometer. The corrosion resistance was characterized by measuring the corrosion potential and breakdown potential. Using the anodic scan measurements, we quantified the effects of surface oxidation itself and air-gap induced by inducing superhydrophobicity on corrosion resistance separately to help develop scalable aluminum nano-surfaces with high corrosion resistance.
나노 구조물 형성을 통한 NiTi 형상기억합금 표면 개질 기법 개발
송경환(Kyounghwan Song),민태기(Taegee Min),남영석(Youngsuk Nam) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
NiTi is a popular shape memory alloy for vascular devices including guide wires, stents, and valves. In this work, we investigated surface nanostructuring techniques for NiTi to reduce the slip resistance and to improve anti-corrosion and anti-thrombosis resistance of surfaces. We applied new chemical oxidation schemes that enable us to control the characteristics of NiTi surfaces with a simple and quick wet-chemical processes. The effects of such modifications on the surface morphology and chemistry were investigated by SEM, EDS techniques and the resulting dynamic contact angles were characterized by high-precision goniometer.The anti-corrosion resistance was compared by measuring the breakdown voltage and the anti-thrombosis resistance was estimated by platelet rich plasma (PRP) adhesion tests. The suggested oxidation scheme creates a stable titanium oxide layer within 5 min that provides 960 mV and 94.4% reduction of PRP adhesion for 60 min.
초발수 표면의 기체층의 주기적 회복을 통한 장기 방오성능 향상
송경환(Kyounghwan Song),정정열(Jung-Yeul Jung),이충엽(Choongyeop Lee),남영석(Youngsuk Nam) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
Superhydrophobic (SHPo) surface have anti-fouling by low adhesion force and surface energy because their surface structures can hold a slippery gas layer between the solid surface and the liquid. However, the gas layer of SHPo surfaces cannot infinitely maintain under liquid circumstance because of liquid pressure or degradation of hydrophobicity. In this paper, to retain the semi-permanent anti-fouling surface, we fabricated a gas generation surface using photolithography and lamination technique. To evaluate the working of the gas generation surface, a relative reflectivity test was investigated and a degraded air layer recovered to ~90% of initial state by gas restoration. The attachment of Pseudomonas aeruginosa (P. aeruginosa) was investigated for 24 hours under static condition using fluorescence imaging of attached bacterial cell. The results show that the restored SHPo surface by gas generation had little bacteria fouling and it exhibits the superior anti-biofouling performance by continuous gas layer for 24 hours.
송경환(Kyounghwan Song),심재환(Jaehwan Shim),정정열(Jung-Yeul Jung),이충엽(Choongyeop Lee),남영석(Youngsuk Nam) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
In this work, we investigated the anti-fouling behaviors of titanium surface by varying the wetting morphology. We nanostructured titanium/stainless steel surfaces by applying hot alkali solution and HCl, which turned the surfaces into superhydrophilic. Then a silane was vapor-deposition on the surface to induce superhydrophobicity. Using the fluorescence image analysis, anti-fouling performance were extracted from the samples with different wetting morphologies, and their anti-fouling performance was quantitatively compared with that of untreated sample. The results show that investigated superhydrphilic surface can improve the anti-fouling performance in initial time (Ti~12h, SUS~24h). When the superhydrophobicity was induced after the silane treatment, the sample showed that increase in the anti-fouling performance of 48~72h. When the oil was infused on superhydrophobic surface, the sample showed increase in the anti-fouling performance in 8~72h. Our work provides the strategies to increase anti-fouling and will help develop titanium/stainless steel surfaces operating at various environment.
항공조사 이미지와 딥러닝 기반 분할모델을 통한 연안쓰레기 현존량의 모니터링 자동화
송경환(Kyounghwan Song),박상현(Sanghyun Park),양윤정(Yoonjung Yang),정정열(Jung-Yeul Jung),이승현(Seung Hyun Lee) 한국해양환경·에너지학회 2021 한국해양환경·에너지학회 학술대회논문집 Vol.2021 No.10
전통적 해양쓰레기 모니터링 방법은 전체 해안의 쓰레기 현존량을 통계적으로 추정함으로써 부정확하고 높은 비용과 함께 비효율적인 문제를 가진다. 본 연구에서 우리는 드론을 사용한 항공조사를 통해 고해상도 이미지를 획득하고 딥러닝 기술을 결합하여 연안 전체에 분포한 쓰레기의 밀도와 면적를 정량적으로 평가하였다. 항공조사에 의해 수집된 이미지들이 중복 없이 정합되었고 연안쓰레기의 밀도가 히트맵으로 가시화되었다. 연안에 분포한 해양쓰레기의 총수는 1,295개였고 평균 밀도는 13.2±6.7 counts·100 m<SUP>-2</SUP>이었다. 연안에 분포한 해양쓰레기들이 딥러닝 기반 네트워크 모델에 의해 6개의 항목으로 분류되었고 그들의 정사면적이 계산되었다. 연안쓰레기가 차지하는 총 정사면적은 약 1,120.77 ㎡이었고, 그들 중 스티로폼이 약 50%로 가장 많았다. 우리의 연구는 성상별 쓰레기의 밀도와 오염면적의 합리적인 추정을 제공했고 연안 오염 평가를 위한 중요한 정보를 제공했다. The conventional marine debris monitoring method has been inefficient with inaccurate and high costs by statistically estimating the debris standing-stock of the whole coast. This study obtained high-resolution images with an aerial survey using drones and combined deep learning technology to quantitatively evaluate the density and area of debris items distributed on the coast. Images collected by the aerial survey were matched without overlap, and the number density of coastal debris was visualized as a heat map. The total number of marine debris distributed along the coast was 1,295, and the average density was 13.2±6.7 counts·100 m<SUP>-2</SUP>. Debris items were classified into six categories by a deep learning-based network model, and their areas were calculated. The total covered area by coastal debris was about 1,120.77 ㎡, and Styrofoam accounted for about 50% of them. Our study provided reliable estimates of the densities and contaminated areas debris with classes and crucial information for coastal pollution assessments.
송경환(Kyounghwan Song),심재환(Jaehwan Shim),정정열(Jung-Yeul Jung),이충엽(Choongyeop Lee),남영석(Youngsuk Nam) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
In this work, we investigated the anti-fouling behaviors of titanium surface by varying the wetting morphology. We nanostructured titanium surfaces by applying hot alkali solution, which turned the surfaces into superhydrophilic. Then a silane was vapor-deposition on the surface to induce superhydrophobicity. Using the fluorescence image analysis, anti-fouling performance were extracted from the samples with different wetting morphologies, and their anti-fouling performance was quantitatively compared with that of untreated titanium sample. The results show that investigated superhydrphilic surface can improve the anti-fouling performance by approximately 90% in 12h. When the superhydrophobicity was induced after the silane treatment, the sample showed that approximately 80% increase in the anti-fouling performance of 48h. When the oil was infused on superhydrophobic surface, the sample showed over 80% increase in the anti-fouling performance in 8~72h. Our work provides the strategies to increase anti-fouling and will help develop titanium surfaces operating at various environment.