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기능성 표면 제작을 위한 전기방사 섬유의 최적 구조 연구
양상혁(Sanghyeok Yang),김승현(Seunghyun Kim),김형진(HyeongJin Kim),성석원(Sukwon Sung),이민성(Minsung Lee),이진기(Jinkee Lee) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
Electrospinning is widely used technology which generates nano sized fibers using polymer or ceramic solutions. We used electrospinning to coat the surface with hydrophilic(PVA, TiO₂) or hydrophobic(PVDF) nano fibers. In order to find spinning condition, we observed shapes of the dispensing taylor cone and compared the morphologies of obtained surfaces using SEM to evaluate characteristics of nano-sized fibers, which is changed by voltage and solute concentration. In case of polymer electrospinning using PVA and PVDF, we added crosslinker for generating insoluble fiber. Finally we compare the contact angle on spinning surface and calculate surface energy depending on fiber’s properties.
캐패시터 부정합 보정 기능을 가진 8비트 스위치-캐패시터 사이클릭 D/A 변환기 설계
양상혁(Sang-Hyeok Yang),송지섭(Ji-Seop Song),김석기(Suki Kim),이계신(Kye-Shin Lee),이용민(Yong-Min Lee) 대한전기학회 2011 전기학회논문지 Vol.60 No.2
A switched-capacitor cyclic DAC scheme with mismatch compensation of capacitors is designed. In cyclic DAC, a little error between two capacitors is accumulated every cycle. As a result, the accumulated error influences the final analog output which is wrong data. Therefore, a mismatch compensation technique was proposed and the error can be effectively reduced, which alleviates the matching requirement. In order to verify the operation of the proposed DAC, an 8-bit switched-capacitor cyclic DAC is designed through HSPICE simulation and implemented through magna 0.18um standard CMOS process.
이새봄,이민기,양상혁,김승현,김형진,성석원,이민성,이진기 한국가시화정보학회 2018 한국가시화정보학회지 Vol.16 No.3
The surface structure of the electrospun polymer fibers depends on the polymer concentration, the type of solvent used, applied voltage and so on. To make a desired surface, it is important to understand the effects of the physicochemical properties to form a stable Taylor cone and jet dispensation. We observed the formation of Taylor cone and a consequent structure of fiber by controlling the parameters of applied voltage, solution concentration, solvent and collector effectively. Once the surfaces were fabricated, the structures were analyzed using optical imaging technologies. As the solution concentration was increased, the smooth fibers were formed. In addition, different solvent ratios determined the viscosity and the surface tension of solutions. As a result, with decreased viscosity and increased surface tension, thin fibers were obtained by electrospinning. Furthermore the aligned nanofiber was successfully created by using drum collector.