• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.79-82
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• 2004

In this paper, we analyze the performance of high-rate OFDM(Orthogonal Frequency Division Multiplexing) in the JTC(Joint Technical Committee) channel models using transmit diversity. In this thesis, each independent channel characteristic antennas in the transmitter are analyzed. Also, Equalization method through the channel estimation in the realistic fading channel environments is applied for BEE 802.11a WLAN system performance. From the simulation results, BER through transmit diversity of WLAN system is evaluated in AWGN channel and multipath channel environments.

• 한국정보보호학회:학술대회논문집
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• 한국정보보호학회 1997년도 종합학술발표회논문집
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• pp.53-67
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• 1997

본 고에서는 인터넷 방화벽 보안정책을 일반 정보 보안정책 수립 절차와 단계에 입각하여 분석하고, 위험처리 등급은 3 단계(낮음, 중간, 높음)로 구분하며, 보안정책 대상은 사용자, 관리자, 기술요원으로 나누어 각각의 방화벽 보안정책을 제시한다. 또한 네트워크 서비스를 방화벽에서 처리할 때 허용여부와 허용 시에 사용되어야 할 인증 등의 보안정책을 제시한다.

• 한국정보보호학회:학술대회논문집
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• 한국정보보호학회 1997년도 종합학술발표회논문집
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• pp.131-140
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• 1997

인터넷 등의 전산망을 통한 정보관련 서비스는 여러 가지 보안 취약점에 노출되어 해커들의 주요 공격 대상이 되고, 특히 WWW 관련 서비스는 불특정 다수를 대상으로 하기 때문에 접근 통제방식으로 어려움이 많고, 최근 많이 사용되는 방화벽이나 기타 보안도구를 이용하여 보안 수준을 높일 수가 없다. 그래서 본 논문에서는 해커들이 공격 가능한 취약점들을 분석하여 해커들의 공격을 사전 방지하고, 올바른 해킹방지 대책를 수립할 수 있는 전산망 취약점 원격 진단시스템 모델을 제시하고, 이에 대한 설계 및 구현내용을 설명한다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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• pp.125-130
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• 1992

If reinforced concrete beam exists crack, ultimate shear transfer strength and shear hardness of section with crack substantially decrease. In this study , five model beams were designed for the objective of clarfying contributions of three shear resistant elements : the compression zone of concrete, dowel action of tension reinforcement, aggregate interlock across cracks, The shear force carried by each resistant element was calculated from the detailed strain data on the contributions to the shear capacity of beams of the shear forces carried by the other three resistant element. The test result follows : 1) Compression zone of concrete (C)-56.2%, 2) Dowel action of tension reinforcement (D)-18.0%, 3)Aggregate Interlock(A)-25.8%.

• 산업경영시스템학회지
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• 제25권5호
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• pp.22-30
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• 2002

Our study emphasizes the importance of the review of the manufacturing industry in order help them make right decision and despite many previous methods for analyzing productivity, we were coming to analyze the efficiency of the industry with Date Envelopment Analysis(DEA). Conclusively, only 4 companies is found to manage their companies effectively among 20 top-ranking companies and there was no any correlation and through the result we could realize that the result analyzed by "DEA" don't exactly match financial rates which means that corporation's management is inefficient. We are quite sure that our study can be approved materials for Benchmarking and Management establishing strategic plan.egic plan.

• 한국세라믹학회지
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• 제21권4호
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• pp.327-332
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• 1984

Proper amount of $Al_2O_3$ must be added to increase the yield of mullite which is formed from free silica decomposed from kaolin. The previous study has suggested that Al powder may be a good $Al_2O_3$ supply source at 1400~150$0^{\circ}C$. In this study the application of Al powder is discussed about its mullitization behavior in the higher temperature range of 1500~175$0^{\circ}C$ the results of which compared with those obtained from the reactive $Al_2O_3$ and activated $Al_2O_3$. The oxdation and reaction stages of Al powder were analyzed by DTA crystal growth andmorphology of the mullite were observed by SEM and the yields of the mullite were compared according to their solubilities in HF solution.

• 한국세라믹학회지
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• 제29권7호
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• pp.533-538
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• 1992

Effect of Li2O.4B2O frit on the microstructural and thermal expansion behaviour of $\beta$-spodumene ceramics was investigated. With 4.0~8.0 wt.% frit addition, sintering temperature range was enlarged and densification was enhanced through liquid phase sintering. As the amount of frit addition was increased, thermal expansion coefficient was increased to 1.72$\times$10-6$^{\circ}C$-1 of its highest value, which indicated that the increment of thermal expansion coefficient due to the second phase was constrained.

• 한국세라믹학회지
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• 제16권3호
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• pp.178-183
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• 1979

The carborundum abrasive specimens bonded with a soda-borosilicate glass were prepared. Samples fired at specified temperatures with various mixing ratio and forming pressure were examined in terms of the structure, bonding strength, and microscopic observations. Increasing the forming pressure up to 400kg/$\cm^2$, the structure became denser in proportion to the forming pressure. The bonding strength was generally increased with increasing the mixing ratio (Vb/Vg), but the bloating phenomena were observed when samples were fired above 95$0^{\circ}C$ with mixing ratio above 20%, consequently, the bonding strength was decreased. Samples fired at the temperature range 900~95$0^{\circ}C$ with mixing ratio 15~30% had the dense structure with various grades.

• 한국세라믹학회지
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• 제29권4호
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• pp.265-272
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• 1992

Role of CaO in the sintering of 12Ce-TZP ceramics was studied. The addition of small amounts of CaO increase the densification rate of 12Ce-TZP by altering lattice defect structure and the diffusion coefficient of the rate controlling species, namely cerium and zirconium cations. CaO also inhibits grain growth during sintering and allows the sintering process to proceed to theoretical density by maintaining a high diffusion flux of vacancies from the pores to the grain boundaries. The inhibition of grain growth is accomplished by the segregation of solute at the grain boundaries, causing a decrease in the grain boundary mobility. The segregation of calcium was revealed by AES study.

• 한국세라믹학회지
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• 제32권3호
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• pp.331-340
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• 1995

Microwave (Hybrid) Heating (MHH) was used to oxidize and sinter Al-Al2O3 powder mixture. For 25 v/o Al specimen and 35 v/o Al specimen, the total processing to produce low-shrinkage reaction bonded alumina was carried out within 1 hour even though conventional furnace process took more than 10 hours. Compared with conventional fast firing process, MHH process increased more than 40% oxidation at the same temperature, and these high oxidation rates were thought to be caused by the surface ohmic current on Al particles.