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      • KCI등재

        주조용 Al합금의 내식성에 관한 전기화학적 평가

        윤대현,이명훈,김기준,문경만,Youn Dae-Hyun,Lee Myung-Hoon,Kim Ki-Joon,Moon Kyung-Man 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.5

        Al is a active metal that owes its resistance to a thin, protective, barrier oxide surface layer, which is stable in air and neutral aqueous solution. Thus Al alloys are widely used in architectural trim. cold & hot-water storage vessels and piping. However Al and most of its alloy may corrode with some forms such as pitting corrosion, intergranular corrosion and galvanic corrosion in the case of exposure to various industrial and marine atmosphere. Therefore a correct evaluation of corrosion resistance for their Al and Al alloys may be more important in a economical point of view. In this study. a relative evaluation of corrosion resistance for three kinds of Al alloys such as ALDC2, ALDC3, and ALDC8 series was carried out with electrochemical method. There is a tendency that corrosion potential is shifted to positive or negative direction by alloying components regardless of corrosion resistance. Moreover the data of corrosion properties obtained from cathodic Polarization curve, cyclic voltammogram and AC. DC impedance respectively showed a good correspondence each other against the corrosion resistance but variation of corrosion potential. passivity current density of anodic polarization curve and corrosion current density by Tafel extrapolation and Stern-Geary method didn't correspond with not only each other but also considerably the data of corrosion properties discussed above. Therefore it is suggested that an optimum electrochemical evaluation for corrosion resistance of Al alloy is to calculate the diffusion limiting current density of cathodic polarization curve, impedance of AC or DC and polarization resistance of cyclic voltammogram.

      • KCI등재

        국가중요시설의 물리적 보안 조직에 대한 보안수준 평가지표 개발

        윤대현,변서희,서우종,정창훈 한국산업보안연구학회 2021 한국산업보안연구 Vol.11 No.1

        If important national facilities are being attacked by external threats, the negative impact on the national security and people’s life will be very serious. Therefore, strengthening the capabilities of security organizations responsible for the security of national critical facilities is a very important task for the safety of the facility and community. Nevertheless, recent incidents such as smuggling, poor gun management, and illegal use of passes have been steadily occurring due to inappropriate performance of physical security organizations of important national facilities. Accordingly, in order to help the security organization in charge of physical security of important national facilities, and to improve their work capabilities, this study presents an evaluation index that can properly assess the security work level ofthe physical security organizations. At First, based on the literature review, We derived the evaluation index factors that can evaluate the work level of a physical security organizations. Then, we confirmed the evaluation indices after a verification process through a survey by physical security experts. In order to utilize the determined evaluation index finely, an AHP analysis was performed to derive the priorities and weights for each evaluation index. We found that The security level evaluation index of the physical security organizations developed in this study is useful in establishing and improving the physical securityorganization’s competent management and performance system of security guards in all organizations that require physical security. 국가중요시설이 외부의 불순 세력으로부터 공격을 받았을 때 국가안보와 국민생활에 미치는 부정적 영향은 매우 심각할 수 있다. 따라서, 이러한 시설의 보안을 책임지는 보안 조직의 역량 강화는 해당 시설과 사회의 안전을 위해 매우 중요한 과제이다. 그럼에도 불구하고, 최근 국가중요시설 물리적 보안 조직의 부실한 역할 수행으로 인해 밀입국, 총기 관리 부실, 출입증 부정 사용 등 관련된 사건들이 꾸준히 발생하고 있는 실정이다. 이에 따라, 본 연구는 국가중요시설의 물리적 보안을 담당하는 보안 조직의 역량을 높이는 데 도움을 주기 위한 목적으로, 물리적 보안 조직의 보안업무 수준을 평가할 수 있는 평가지표를 제시하였다. 이를 위해, 본 연구에서는 우선 문헌분석을 통해 물리적 보안 조직의 업무 수준을 평가할 수 있는 지표들을 도출하였고, 전문가들의 설문조사를 통한 검증 과정을 거쳐 지표를 확정하였다. 확정된 지표를 보다 정교하게 활용할 수 있도록, AHP 분석을 수행하여 각 지표에 대한 우선순위와 가중치를 도출하였다. 본 연구에서 제시한 물리적 보안 조직의 보안업무 수준 평가지표는 국가중요시설뿐만 아니라 물리적 보안을 필요로 하는 모든 기관에서 물리적 보안 조직 역량관리 및 보안요원들의 성과관리 체계를 구축하거나 개선하는 데 유용하게 활용될 수 있을 것으로 기대된다.

      • SCOPUSKCI등재

        X-선 회절을 이용한 비정질 SiO$_2$ Gel 의 구조 해석에 관한 연구

        윤대현,김기선,정현채,Yoon dai Hyun,Kim Ki Sun,Jung Hyun Chai 대한화학회 1990 대한화학회지 Vol.34 No.5

        Sol-gel법을 통하여 만들어진 비정질 SiO$_2$ gel들의 구조가 열처리 온도, 80$^{\circ}C$, 250$^{\circ}C$, 450$^{\circ}C$ 그리고 1000$^{\circ}C$에 따라 변화하는 과정을 X-선 회절 강도 측정으로부터 구한 동경분포곡선을 이용하여 알아보았다. 그리고 이를 6개의 결정들과 비교하여 예상되는 구조를 밝혔다. 각 시편들은 용융법으로 구한 SiO$_2$의 구조와 O-O결합쌍을 제외하고는 가장 유사한 구조를 가지며 cubic형으로 나타났다. The structural variation process of amorphous SiO$_2$ gel upon heat-treatment conditions of 80, 250, 450 and 1000$^{\circ}C$ has been studied by using the radial distribution functions (RDF$_{obs}$) estimated from the X-ray diffraction intensities. The expected gel structure was determined by comparing the RDF$_{obs}$ with those for the other six standard samples selected appropriately. The structure of specimens prepared by sol-gel method is well consistent with that of fused SiO$_2$ (${\beta}$-cristobalite with cubic symmetry) except a slight difference in O-O band distance.

      • 효소로 변성시킨 관절연골의 정량적 자기공명영상

        윤대현,이영준,김옥화 인제대학교 2003 仁濟醫學 Vol.24 No.1

        Objectives : The purpose of this study was to evaluate the findings of quantitative MR imaging and Gd(DTPA)^(2-) -enhanced MR imaging of articular cartilage degraded by collagenase type Ⅶ and chondroitinase ABC. Methods and Materials : Twenty-one cartilage-bone blocks obtained from 10 pig patellae were cultured with collagenase and chondroitinase. The enzymatic degradation was conducted with different concentrations and with differents durations of culture, 0. 20, 40. 80 hours respectively. The change of signal intensity and relaxation times of the articular cartilage, which was caused by the depletion of the collagen and proteoglycan, was studied with an MRI using the two different techniques mentioned above. This data was also compared with that acquired from the normal cartilage. Four different histologic stains were performed to identify a loss of collagen and proteoglycan in cartilage. Results : The depletion of the collagen and proteoglycan induced by enzymes was identified in histologic studies. Both the signal and contrast to noise ratio decreased in the groups of 40 and 80 hours enzymatic culture, as compared with the groups of 0 and 20 hours culture. A statistically significant Gd(DTPA)^(2-) -enhancement was noted in the cartilage treated with chondroitinase, resulting from depletion of the proteoglycan, but the degree of enhancement did not correlate to the duration of the culture. There was no correlation between the concentration of the enzymes or duration of culture and T1, rho, and T2 relaxation times of the cartilage. The T1 relaxation time of the cartilage after Gd(DTPA) ^(2-) -enhancement decreased in the following order : group B, group C, group A, and group D. Conclusion : The results indicate that Gd(DTPA) ^(2-) -enhancement rather than signal change or T1, rho,T2 relaxation parameters are sensitive to depict the proteoglycan depletion. Gd(DTPA) ^(2-) -enhanced MR imaging have the potential as a mean of imaging modality for early detection of biochemical degradation of the articular cartilage at 1.5 T MRI.

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