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김경준(KyungJoon Kim),백재종(JaeJong Baek),송주석(JooSeok Song) 한국정보보호학회 2014 정보보호학회논문지 Vol.24 No.1
본 연구에서는 프록시 모바일 IPv6 환경에서의 인증 지연시간을 최소화하기 위하여 계층적인 인증 기법을 제시한다. AAA 서버의 인증 기능을 LMA와 MAG에 분산하여 해당 LMA 또는 MAG가 모바일 노드에 관한 정보를 가지고 있는 경우 AAA 서버를 거치지 않고 빠르게 인증을 하여 인증 지연 시간을 줄일 수 있는 기법을 제시한다. AAA 서버는 인증을 위한 모든 것을 담당하고 있기 때문에 AAA 서버에 서비스 거부 공격 등으로 인한 단일 고장점 문제가 발생할 경우 모바일 노드는 더 이상 프록시 모바일 IPv6 네트워크에 접속할 수 없는 문제가 발생한다. LMA와 MAG에 인증 기능을 분산함으로써 이러한 단일 고장점 문제에 대응하고 보다 가까운 네트워크 장비에서 보다 가벼운 인증을 수행함으로써 인증 지연시간을 줄일 수 있다. In this paper, a hierarchical authentication protocol is proposed to minimize authentication delay in proxy mobile IPv6 networks. The authentication function of the AAA server is distributed to the LMAs and the MAGs. If the LMAs or the MAGs have authentication information of the MNs, they authenticate the MN on behalf of the AAA servers. Therefore, the authentication delay is reduced. The AAA server is vulnerable to denial-of-service attack. If the AAA server is down, MNs cannot access the proxy mobile IPv6 network until they are authenticated. The proposed scheme reduces the load on the AAA server by distributing the authentication function to the LMAs and the MAGs.
Preparation, structure and photoluminescence properties of SiO<sub>2</sub>–coated ZnS nanowires
Jin, Changhyun,Lee, Jungkeun,Baek, Kyungjoon,Lee, Chongmu WILEY-VCH Verlag 2010 Crystal research and technology Vol.45 No.10
<P>It is essential to passivate one-dimensional (1D) nanostructures with insulating materials to avoid crosstalking as well as to protect them from contamination and oxidation. The structure and influence of thermal annealing on the photoluminescence properties of ZnS-core/SiO<SUB>2</SUB>-shell nanowires synthesized by the thermal evaporation of ZnS powders followed by the sputter deposition of SiO<SUB>2</SUB> were investigated. Transmission electron microscopy and X-ray diffraction analyses revealed that the cores and shells of the core-shell nanowires were single crystal zinc blende-type ZnO and amorphous SiO<SUB>2</SUB>, respectively. Photoluminescence (PL) measurement showed that the core-shell nanowires had a green emission band centered at around 525 nm with a shoulder at around 385 nm. The PL emission of the core-shell nanowires was enhanced in intensity by annealing in an oxidative atmosphere and further enhanced by subsequently annealing in a reducing atmosphere. Also the origin of the enhancement of the green emission by annealing is discussed based on the energy-dispersive X-ray spectroscopy analysis results. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
SYNTHESIS AND PHOTOLUMINESCENCE PROPERTIES OF ZnSe-CORE/SnO2-SHELL NANORODS
진창현,HYUNSOO KIM,KYUNGJOON BAEK,CHONGMU LEE 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2010 NANO Vol.5 No.5
ZnSe-core/SnO2-shell nanorods have been prepared by using a two-step process comprising the thermal evaporation of ZnSe powders and the atomic layer deposition of SnO2. ZnSe nanorods have been grown by the thermal evaporation of ZnSe powders on gold-coated Al2O3 (0001) substrates. The ZnSe-core/SnO2-shell nanorods were 0.1–0.2 μm in diameter and up to a few tens of micrometers in length. Transmission electron microscopy and X-ray diffraction analysis results indicate that the cores and shells are single crystal zinc blende-type ZnSe and polycrystalline simple orthorhombic-type SnO2, respectively. Photoluminescence measurements show that the ZnSe-core/SnO2-shell nanorods have a strong orange emission band centered at around 650 nm. The orange emission of the ZnSe nanorods is enhanced in intensity by coating them with SnO2 and further enhanced by annealing them. A reducing atmosphere is more efficient in enhancing the orange emission than an oxidative atmosphere. The highest emission intensity is obtained for the shell layer thickness corresponding to 1500 ALD cycles. The orange emission enhancement by annealing is mainly attributed to the formation of Sn interstitials in the ZnSe cores during the annealing process.
Jin, Changhyun,Kim, Hyunsoo,Baek, Kyungjoon,Kim, Hyoun Woo,Lee, Chongmu WILEY-VCH Verlag 2010 Crystal research and technology Vol.45 No.2
<P>Ga<SUB>2</SUB>O<SUB>3</SUB>/SnO<SUB>2</SUB> coaxial nanowires were synthesized by thermal evaporation of GaN powders and then atomic layer deposition of SnO<SUB>2</SUB>. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis results indicate that the Ga<SUB>2</SUB>O<SUB>3</SUB> cores and the SnO<SUB>2</SUB> shells of the coaxial nanowires after thermal annealing are single crystals with monoclinic and simple orthorhombic structures, respectively, although the SnO<SUB>2</SUB> shells are amorphous before annealing. Our results also show that photoluminescence (PL) emission can be enhanced by thermal annealing in an H<SUB>2</SUB>/N<SUB>2</SUB> atmosphere. EDX concentration profile suggests that the enhancement in the bluish green emission is due to the increase in the concentration of the Ga vacancies in the cores during the H<SUB>2</SUB>/N<SUB>2</SUB> annealing. On the other hand, a red emission is newly formed while the bluish green emission is degraded by annealing in an oxygen or nitrogen atmosphere (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Analog Synapse Device With 5-b MLC and Improved Data Retention for Neuromorphic System
Moon, Kibong,Cha, Euijun,Park, Jaesung,Gi, Sanggyun,Chu, Myonglae,Baek, Kyungjoon,Lee, Byunggeun,Oh, Sang Ho,Hwang, Hyunsang IEEE 2016 IEEE electron device letters Vol.37 No.8
<P>This letter presents an investigation of analog synapse characteristics of a PCMO-based interface switching device with varying electrode materials. In comparison with the filamentary switching device having only 1-b storage and variability issues, the interface switching devices exhibit excellent electrical properties, such as 5-b (32-level) multi-level cell characteristics, wafer-scale switching uniformity, and scalability of the switching energy with device area. To improve data retention of the interface switching device, we propose a Mo electrode to increase the oxidation barrier height (similar to 0.4 eV) that, in turn, significantly improves the retention time and pattern classification accuracy of neural networks.</P>