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이상현,이상준,문경일,조성의 한국IT서비스학회 2009 한국IT서비스학회지 Vol.8 No.4
Objectifying claims filed during the warranty period, analyzing the current circumstances and improving on the problem in question is an activity worth doing that could reduce the likelihood of claims to occur, cut down on the costs, and enhance the corporate image of the manufacturer. Existing analyses of claims are confronted with two problems. First, you can’t precisely assess the risks of claims involved by means of the value of claims per 100 products alone. Second, even in a normal state, the existing approach fails to capture the probabilistic conflicts that escape the upper control limit of claims, thus leading to wrong control activities. 1 이상현·이상준·문경일·조성의 To solve the first problem, this paper proposed that a time series detection concept where the claim rate is monitored based on the date when problems are processed and a hazard function for expression of the claim rate be utilized. For the second problem, this paper designed a model whereby to define a normal state by making use of PID (Proportion, Integral, Differential) and infer by way of a fuzzy concept. This paper confirmed the validity and applicability of the proposed approach by applying methods suggested in the actual past data of warranty claims of a large-scaled automotive firm, unlike hypothetical simulation data, in order to apply them directly in industrial job sites, as well as making theoretical suggestions for analysis of claims.
콘크리트 표면마감재의 탄산화 억제성능 평가를 위한 FEM 해석연구
이상현,박원준,이한승,경제운,변영모 대한건축학회 2007 大韓建築學會論文集 : 構造系 Vol.23 No.9
Recently, Reinforced Concrete(from now on RC) has been used in most of the buildings because RC has strong points not only on engineering side such as compressive and tensile force but also economic side. But in the air concrete grow acid and acid, as a result an iron bar in the concrete occurs corrosion and it shortens the endurance life of RC structure. Therefore, to lengthen endurance life of RC structure, we use some kinds of surface-finishes. These surface-finishes have abilities such as restraint for penetration and diffusion of CO2. In this study, we wanted to know whether we can evaluate the restrain effect for carbonation according to surface-finishes with using FEM analysis. After study, we found that it is possible and we can also evaluate the restrain effect for carbonation on other surface-finishes with this process.
PVdF-HFP/TiO2 나노복합체 보호층을 통한 리튬금속전지 음극의 전기화학적 성능 향상
이상현,최상석,김동언,현준혁,박용욱,유진성,전소윤,박중원,신원호,손희상 한국막학회 2021 멤브레인 Vol.31 No.6
고용량 배터리에 대한 요구가 증가에 따라 기존 음극재보다 높은 용량(3,860 mAh/g)과 낮은 전기화학적 전위(– 3.040 V)를 갖는 리튬 금속 기반 음극재에 대한 연구가 활발하게 이루어지고 있다. 본 연구에서는 수열 합성을 통해 제작된 아나타제(anatase) 타입의 TiO2 나노 입자 기반한 PVdF-HFP/TiO2 복합체를 리튬 금속 음극의 계면 보호층으로 적용하였다. 결정구조 및 형상 분석을 통해 유/무기-리튬 나노복합체 박막의 형성을 확인하였다. 또한, 전지화학 테스트(사이클 테스트 및 전압 프로파일)를 통해 리튬 금속 음극의 전기화학 성능은 복합체 보호막이 TiO2 10 wt%, 코팅 두께 1.1 μm의 조건에서 가장 개선된 전기화학적 성능(콜롱 효율 유지: 77 사이클 동안 90% 이상) 발현을 확인하였다. 이를 통해, 처리하지 않은 리튬 전극 대비 본 보호층에 의한 리튬 금속 음극의 성능 안정화/개선 효과가 검증되었다. As the demand for high-capacity batteries increases, there has been growing researches on the lithium metal anode with a capacity (3,860 mAh/g) of higher than that of conventional one and a low electrochemical potential (–3.040 V). In this study, using the anatase phased TiO2 nanoparticles synthesized by hydrothermal synthesis, a PVdF-HFP/TiO2 organic/inorganic composite material was designed and used as an interfacial protective layer for a Li metal anode. As-formed organic/inorganic-lithium composite thin film was confirmed through the crystalline structure and morphological analyses. In addition, the electrochemical test (cycle stability and voltage profile) confirmed that the protective layer of PVdF-HFP/TiO2 composite (10 wt% TiO2 and 1.1 μm film thickness) contributed to the enhanced electrochemical performance of the lithium metal anode (Colombic efficiency retention: 90% for 77 cycles). Based on comparative test with the untreated lithium electrode, it was confirmed that our protective layer plays an important role to stabilize/improve the EC performance of the lithium metal negative electrode.