• Electrical & Electronic Materials
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• v.8 no.5
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• pp.611-618
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• 1995

The (Sr$_{1-x}$ .Ca$_{x}$)TiO$_{3}$+0.6[mol%]Nb$_{2}$O$_{5}$ (0.05.leq.x.leq.0.2) ceramics were fabricated to form semiconducting ceramics by sintering at about 1350[.deg. C] in a reducing atmosphere(N$_{2}$ gas). Metal oxides, CuO, was painted on the both surface of the specimens to diffuse to the grain boundary. They were annealed at 1100 [.deg. C] for 2 hours. The 2nd phase formed by thermal diffusing from the surface lead to a very high apparent dielectric constant. According to increase of the frequency as a functional of temperature, all specimens used in this study showed the dielectric relaxation, and the relaxation frequency was above 106 [Hz], it move to low frequency with increasing resistivity of grain. The specimens showed three kinds of conduction mechanisms in the temperature range 25-125 [.deg. C] as the current increased: the region I below 200 [V/cm] shows the ohmic conduction. The region rt between 200 [V/cm] and 2000 [V/cm] can be explained by the Poole-Frenkel emission theory, and the region III above 2000 [V/cm] is dominated by the tunneling effect.fect.

• Journal of radiological science and technology
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• v.26 no.4
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• pp.53-61
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• 2003

This system Will allow primary and secondary treatment institutions poorly equipped with medical equipment to use Internet and book their patients' medical checkups with tertiary hospitals equipped with remote medical information system. This research aims to make theoretical studies on the remote medical service information sharing system and discuss its utility and factors to be considered for spreading the system. To efficiently push ahead with the remote medical service information sharing system, we need to be open-minded in sharing medical service information, establish comprehensive pursuit system, introduce incentive aimed at activating the information system, have close coordination with the central government, flexibly respond to changing technologies, and offer publicity and education.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.3
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• pp.578-588
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• 1992

In order to predict the effect of swirl on the structure of concentric laminar jet diffusion flame, present study examined the effect of swirl on the flame characteristics by numerical numerical analysis through theoretical model. The theoretical model has been developed for the co-axial laminar jet flame such that the fuel and air are supplying with swirl through inner and outer co-axial tube respectively. For the parametric study, swirl number, Reynolds number of fuel and air and directions of swirl are chosen as important parametes. The results of study show that the flame with width and shorter length is formed by larger swirl number. The important factor of the flame shape is the recirculating zone formed around jet axis near the exit of nozzle. In case of weak swirl, the effect of directions of swirl is not appeared. However, for the strong swirl, the flame with shorter length are appeared in case of counter-swirl compared with the case of co-swirl.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.25-31
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• 2005

The theory developed in a preceding paper [1] for poroelastic composite material behavior under thermal and gas diffusion is applied to thermo-chemical decomposition of a carbon-phenolic composite rocket nozzle liner under typical operating conditions. Specifically, the structural component simulated is the cowl ring for which distributions of pressure in the material pores, temperature and across-ply stress are presented. The results for particular composite designs show that across-ply failure occurs due to tensile stress in the material which is indicative of plylift. This prediction corroborates observations of plylift in a nozzle cowl. Simulations suggest designs to avoid plylift in the cowl zone.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.103-108
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• 2011

The turbulent mixing of a kerosene/liquid oxygen coaxial swirl injector under supercritical pressures have been numerically investigated. Kerosene surrogate models are proposed for the kerosene thermodynamic properties. Turbulent numerical model is based on LES(Large Eddy Simulation) with real-fluid transport and thermodynamics over the entire pressure range; Soave modification of Redlich-Kwong equation of state, Chung's model for viscosity/conductivity, and Fuller's theorem for diffusivity to take account Takahashi's compressible effect. The effect of operating pressure on thermodynamic properties and mixing dynamics inside an injector and a combustion chamber are investigated. Power spectral densities of pressure fluctuations in the injector under various chamber pressure are analyzed.

• Journal of the Korea Society of Computer and Information
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• v.6 no.3
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• pp.91-101
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• 2001

In this paper, we examined the concept and introduction effect of internet E-commerce. We analysed some factors are influenced to the B2B internet E-commerce. According to the result Environment factors divided into uncertainty and industrial competition factors, organization factors divided into scale, concentration of decision making, standardization of work. And information system take in IS/IT infra structure, integration of information technology Throughout this study, Enterprises which was introduced to the B2B internet E-commerce enable to be provided for introduction Judgment, guide of decision making, successfully adaptation, furthermore enlarged e-commerce trade.

• The Journal of Society for e-Business Studies
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• v.23 no.3
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• pp.173-187
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• 2018

After Satoshi Nakamoto published 'Bitcoin: A peer-to-peer electronic cash system' in 2008, Blockchain has been GPT (General Purpose Technologies) that affect the whole cycle of the $4^{th}$ Industrial Revolution. This study attempted to identify the innovativeness of Blockchain. Because of Blockchain's ambidextrous characteristics, Blockchain has two kinds of innovativeness, technological innovation by physical technology and social innovation by social technology. Thus, this study will be useful to increase understanding and establishing strategy for Blockchain.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.6
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• pp.1035-1043
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• 2022

With the spread of the Internet of Things (IoT), cloud computing, and big data, the need for high-speed encryption for applications is emerging. GPU optimization can be used to validate cryptographic analysis results or reduced versions theoretically obtained by the GPU in a reasonable time. In this paper, PIPO lightweight encryption implemented in various environments was implemented on GPU. Optimally implemented considering the brute force attack on PIPO. In particular, the optimization implementation applying the bit slicing technique and the GPU elements were used as much as possible. As a result, the implementation of the proposed method showed a throughput of about 19.5 billion per second in the RTX 3060 environment, achieving a throughput of about 122 times higher than that of the previous study.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.261-261
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• 2023

전 세계적으로 핵실험은 약 2,056회 실시되었으며, 이 중에서 대기권에서 실험한 횟수는 528회로 알려져 있다. 다량의 핵무기가 폭발하게 되면 핵폭발시 강한 복사열에 의해서 생성된 분진과 화재로 발생된 가스가 대기 중으로 확산되어 수 개월간 태양광을 차단함으로써 급격한 지구의 온도하강을 야기시켜 많은 사람들이 죽게 될 것이라는 핵겨울(nuclear winter) 이론이 1983년에 발표된 바 있지만, 핵실험 전·후 실제 기상자료룰 분석한 연구는 드문 편이다. 최근 학계에서 1950~1960년대 핵실험 전·후 실험장소로부터 480km 떨어진 곳의 영국 기상청 자료를 분석한 결과, 지상 핵실험 실시 직후 강수량이 24% 증가했다는 연구결과가 보고된 바 있다. 핵무기가 투하된 지점 중에 한국과 가장 가까운 곳은 1945년 8월 6일 08시 15분, 서울에서 604 km 떨어져 있는 히로시마와, 8월 9일 11시 2분 서울에서 594km 떨어져 있는 나가사키가 있다. 본 연구의 목적은 지상 핵실험이 강수량에 미치는 영향을 분석하기 위한 것으로, 한국과 일본의 기상자료를 그 대상으로 하였다. 본 연구는 히로시마와 나가사키 원자폭탄 폭발 전·후에 강수량 변화를 중점으로 하였으며, 이를 위하여 1940~1950년 기간의 국내 주요 관측 지점의 기상자료와 확보 가능한 히로시마와 나가사키의 기상자료를 수집하여 연구에 활용하였다. 연구결과 핵무기가 폭발하게 되면, 투하지점뿐만 아니라 인근 지역의 수문기상에 영향을 줄 수 있음을 알 수 있었다.

• Journal of the Korea Society of Computer and Information
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• v.14 no.6
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• pp.165-171
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• 2009

From the late 20th century, rapidly progressing information communication technology and spreading Internet all over the world cause many reverse functions when there is a conversion into the new information society. One of them is cyber terrorism as cyber crime. Cyber terrorism gradually has had a serious problem in the national security as well as the domestic aspects. Therefore, this study looked into the present condition of cyber terrorism, discussed its prospect, and sought the efficient national countermeasure methods against cyber terrorism by comparing other countries' countermeasure systems currently.