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현동훈,전정환,이창훈,정현철,김성현 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.8
Organic-inorganic composite membranes were prepared with sulfonated poly(ether ether ketone) (SPEEK) and different amounts of silica to improve chemical stability and vanadium hindrance for a vanadium redox flow battery. The durability of the prepared composite membrane was verified using a self-made dummy cell system and fully charged vanadium cathode half-cell electrolyte, which contained oxidative vanadium ions (VO2 +). The prepared composite membranes, with covalent crosslinking between the organic polymer and inorganic particles, resulted in reduced vanadium permeability and enhanced chemical stability. Ion exchange capacity, water uptake, proton conductivity, and vanadium permeability decreased with increasing silica content. Selectivity was defined to consider both permeability and proton conductivity and resulted in a membrane that exhibited both high proton conductivity and low ion permeability simultaneously. The prepared 1 wt% silica composite membrane showed 133-fold higher selectivity compared with that of a Nafion112 membrane. After the stability test, the composite membrane showed little change compared to the membrane before the stability test, which confirmed the commercial prospect of SPEEK/SiO2 composite membrane for a vanadium redox flow battery
금형 가공의 합리화를 위한 최적 절삭조건 선정 시스템에 관한 연구
현동훈,이용성 한국산업안전학회 1993 한국안전학회지 Vol.8 No.4
In recent years, mould industry in machining requires to increase machining productivity and to reduce costs, To adapt this trend it is necessary to optimize machine condition, Even though many researches in this area introduced various way to set the optimal condition, still there are not enough. Therefore this research was done to select the optimal cutting condition for industry, and to develop the computer program to select the optimal cutting condition automatically. The result of this research will contribute to increase machining productivity of various mould companies with the automatic selection of optimal cutting condition.
Note on the decomposition of states
현동훈,김재광 대한수학회 2018 대한수학회보 Vol.55 No.4
We derive a sharp decomposition formula for the state polytope of the Hilbert point and the Hilbert-Mumford index of reducible varieties by using the decomposition of characters and basic convex geometry. This proof captures the essence of the decomposition of the state polytopes in general, and considerably simplifies an earlier proof by the authors which uses a careful analysis of initial ideals of reducible varieties.
현동훈,이용성 대한기계학회 1993 대한기계학회논문집 Vol.17 No.9
The study presents the development of a cost-effective CAD/CAM system for metal moulds by use of personal computer. In the personal CAD/CAM system named DKSYS, metal moulds are defined by the operations of basic elements such as prism, pyramid and sphere, plane, rotational body, and surface elements including curved surface. The internal expression of shape elements in the computer is based on the wire model, which is a set of cross-sectional curves of the shape elements. With the addition of OMS system to CAD/CAM system the optimum cutting condition can be selected automatically. After programming NC information with the form definition and the optimum cutting condition, the metallic mould can be formed by transferring cutting information to CNC machine through DNC system. Using a computer for the above process, it is possible to increase the productivity and reduce the cost.
플라스틱 비구면 픽업 렌즈의 사출조건에 대한 수차변화 연구
현동훈,이승준,이승수 한국공작기계학회 2004 한국공작기계학회 춘계학술대회논문집 Vol.2004 No.-
In this study, the pattern of lens aberration was studied at different injection molding conditions such as injection speed, holding pressure, holding pressure time, mold temperature and cylinder temperature and, then, the results were analyzed with a laser interferometer. It was demonstrated that optimal condition of lens aberration could be achieved by adjustment of injection molding conditions.