윤세영 교수

Abstract Clay–starch composites with different aggregate sizes and starch to clay ratios were prepared by a simple precipitation method. The aggregates of the composites were used as fillers to improve the paper properties. The experimental results showed that the paper strengths increased more than 100% for starch‐modified clay compared to untreated clay at 20–30% clay loading. The increase in paper strengths of clay–starch composite‐filled handsheets was mainly due to two reasons, i.e., the re

Abstract A stable aqueous solution of reduced graphene is prepared by chemical reduction of GO in the presence of PNIPAM in water through the hydrophobic interaction between graphene plates and PNIPAM backbones. Thermosensitive solubility switching of the graphene/PNIPAM assembly was successfully demonstrated below or above the LCST, which is higher (up to 42 °C) than the LCST of pure PNIPAM (36 °C) because interacting PNIPAM chains on graphene plates are less mobile than free PNIPAM chains. The

In order to improve filler-fiber bonding in paper, starch-filler composites were prepared by a starch-fatty acid complex formation method. These composites were used as a papermaking filler to improve the physical properties of the paper, filler retention, and the sizing effect. The solubility of the starch-fatty acid complex in water at different temperatures was measured. The results indicated that the starch-fatty acid complexes have very low solubility in water below 70℃, which can be easily

Abstract Solubilization of reduced graphene is simply attempted through in situ reduction of graphene oxide (GO) solution in the presence of poly(propylene imine) dendrimers G4 or G5 with terminal amine groups through noncovalent interaction. Interestingly, porous graphene film was formed by filtration of these dendrimer-stabilized reduced graphene solutions.

To increase the filler content in paper without sacrificing paper properties, clay−starch composites, made from a simple precipitation method, were used in papermaking. Compared to untreated clay, the clay−starch composite filled paper improved paper tensile strength up to 100−200%. Contrary to untreated clays that usually reduce the ZDT ( z -directional tensile strength) of papers, the clay−starch composite actually increases the ZDT. The significant improvements in the paper strengths are attr

Abstract Patterning of reduced graphene is successfully demonstrated through ink-jet printing of graphene oxide (GO) ink and subsequent reduction with hydrazine vapor in submillimeter scale. GO plate size is the most critical parameter for the success of facile ink-jet printing of GO ink. Prepared graphene lines show conductivity of 1.1 S m−1, which is a fifth of typical conductivity of graphene film, which might result from decreased percolation of graphene plates in ink-jet printing.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We develop a detailed dynamical model of a flexible robotic positioner which consists of two articulated permanent magnets and a suspended C-arm curved beam carrying them under gravitational and electromagnetic loads. The model is used to design a controller for positioning the magnets for medical navigation applications. An accurate nonlinear model of the structure is obtained as a combination of th

The paper industry utilizes fillers either to reduce the cost or to provide desired functional or end-use properties of paper products. However, there are disadvantages associated with higher filler loadings beyond a certain level, which reduces paper strength. The present study focused on improving the physical property of filled papers. Three methods of structuring fillers were designed; precipitation with starch, complexation with starch and fatty acid, and regeneration with cellulose. Becaus

Since there are three hydroxyl groups on each anhydroglucose ring of the cellulose, the renewable resources, we can get various functional papers by the chemical modification of cellulose. The reaction involving the introduction of the -cyanoethyl (-CN) group into organic substances containing reactive hydrogen atoms is known as cyanoethylation. Cellulose reacts with acrylonitrile in the presence of strong alkalis in a typical manner of primary and secondary alcohols to form cyanoethyl ethers. I

ABSTRACT Micro organic light‐emitting diodes (microOLEDs) are gaining attention for next‐generation augmented reality (AR) and virtual reality (VR) applications due to their compact form factors and high pixel density. However, traditional multilayer thin‐film simulations—based on the assumption of dipole emitters embedded in infinite planar layers—fail to capture the three‐dimensional optical effects of microOLEDs. This is primarily due to their micrometer‐scale pixel size, which becomes compar

Zinc deficiency is characterized by acrodermatitis enteropathica like eruption such as periorificial dermatitis, diarrhea and mental irritability. This syndrome occurs due to decreased supplementation, increased consumption or decreased bowel absorption of zinc. We report here on a case of acquired zinc deficiency in a patient who was receiving total parenteral nutrition due to ischemic colitis. She showed denuded patches on the perinasal, perioral and perineal area and tense bullae on both hand

미세먼지로 인한 대기오염이 날로 심각해짐에 따라 디젤자동차의 배출가스 규제는 지속적으로 강화되어오고 있다. 이와 같이 강화되는 배출가스 규제 만족을 위해 매연저감장치(DPF), 선택적 환원 촉매(SCR) 장치 등이 디젤자동차에 탑재되어 출시되고 있다. Euro 4, 5 규제 민족 디젤자동차의 경우 질소산화물(NOx)을 줄이기 위해 흡입 공기의 최대 40%까지 배기가스를 흡기관으로 재순환시키는 EGR 방식을 사용하고 있으며 이 경우 배기가스 중에 포함된 다량의 매연 성분들이 흡기계에 축적되어 엔진의 성능저하, 연비 저하, 유해 배출가스를 증가시키는 문제를 발생시키게 된다. 이번 연구에서는 9만km 이상 주행한 디젤 차량의 인젝터, 흡기다기관, 스로틀 플랩, EGR cooler 등을 세척하여 세척 전과 세척 후의 배출가스 및 연비를 측정하여 그 결과를 비교하였다. 시험은 Euro 5 디젤 차량을 대상으로 차대동력계상에서 디젤 운행차 시험모드인 KD-147 모드로 실험하였고, 배출가스 분