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Wireless LAN(IEEE 802.11)에서 인증시간 단축을 위한 보안 메커니즘에 관한 연구
홍경식,서종수,고광용,정준하,이철기,Hong, Kyung-Sik,Seo, Jong-Soo,Ko, Kwang-Yong,Jung, Jun-Ha,Lee, Choul-Ki 한국ITS학회 2009 한국ITS학회논문지 Vol.8 No.6
무선랜을 ITS에 적용하기 위해서는 무선 구간 보안성 향상과 이동성 지원을 위한 빠른 접속이 요구된다. 그러나 IEEE 802.11i 보안 표준을 적용하는 경우 보안 강화를 위한 IEEE 802.1X 사용자 인증 및 4-Way handshake 과정을 수행함으로써 접속 지연이 발생하여 ITS에 그대로 적용하기에는 무리가 있다. 본 논문에서는 이러한 문제를 해결하기 위해 Key Table을 이용한 Password 인증 및 데이터 암호화 메커니즘을 제안하고, 성능 분석을 통해 검증하였다. Both security enhancement in wireless and fast access for mobility are required to employ wireless LAN in ITS (Intelligent Transportation Systems). However, for the case of employing IEEE 802.11i security standard, it is known that the user authentication procedure of IEEE 802.1x and 4-way handshake procedure for stronger security enforcement may not be suitable for ITS due to its large delay. In this paper, we propose fast authentication method to resolve the above authentication delay problem, and verify its performance via simulation analysis.
법랑질 표면의 탈회 및 재광화 후 EPMA (electron probe micro-analysis)를 이용한 칼슘, 인, 불소 변화의 정량적 분석
홍경식,허복,이찬영,금기연,Hong, Kyoung-Sik,Hur, Bock,Lee, Chan-Young,Keum, Ki-Yeon 대한치과보존학회 2001 Restorative Dentistry & Endodontics Vol.26 No.5
The aim of this in vitro study was to analyze the composition of human tooth enamel in terms of three components, Ca, P, and F after demineralization and remineralization in acid buffer solution. A total of 8 human premolars without any defects and cracks were selected and buccal and lingual sides of the teeth were cleaned with an ultrasonic device and pumice without fluoride 5$\times$5mm windows were opened, and other areas were completely covered with 3-coats of nail varnish to prevent from being in contact with demineralized and remineralized solutions. After demineralization process, each tooth was sectioned into two slices, highly polished one of them with$\gamma$-alumina, and then analyzed the composition of the demineralized tooth with EPMA(electron probe micro-analyzer). The other slices were put into the remineralized solution for 10 days, polished, and analyzed in the same manner. These data were statistically analyzed with one sample t-test(p<0.05). The results were as follows. 1. Normal tooth enamel consists of 49.76% Ca, 39.80% P, and 0.28% F. 2. After demineralization, percentage of Ca and P ratio were decreased by about 5.57 and 5.07% respectively. Percentage of F ratio was also decreased by about 0.01%, which was not statistically significant. 3. After remineralization, percentage of Ca, P increased about by 4.47 and 4.35% respectively Percentage of F decreased by about 0.01%, which was not statistically significant. In conclusion, remineralized solution used in our study has the potential to induce the uptake the Ca and P into the pore sites of the demineralized enamel. But, in the oral cavity. there were rapid temperature change, organic matrix that inhibits the movement of the ions, and limitation of continuous contact with this remineralized solution. Therefore, further in vivo study is necessary.