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항공기 구조용 Ti-6Al-4V의 수소화처리를 통한 초소성특성 향상
김광배,정성환 한국항공대학교 1995 論文集 Vol.33 No.-
The Alloys can be hydrogenated with large amount of hydrogen and dehydrogenated invaceume at elevated temperature. Because hydrogen is β-Ti stabilizer and produces hydride(TiH₂) into microstructure optimum phase ratio is maintained at readly low temperautre and hydrides introduce localized high densitydislocation which provides with nucheation site for rerystallization. after hydrogenation treatment was performed at 830℃ for 10 minutes Pre-Treatment was performed at 760℃ and 830℃ with Water Quenching and Air Cooling. Agter pre-treatment Aging Treatement was carried out at 500℃ for 6 hours and Dehydrogenation Treatment was carried out at 760℃ for 24 hours. Specimen exhibits fine equiaxed granins of about 2㎛.
정성환 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-
A membership function-based image retrieval system with a relevance feedback, is proposed. First, 24-dimentional Gabor features are extracted from the images. Next, the extracted features are reduced to 12-dimentional feature vectors by using KL transform. Then, we use them to generate membership values for the image retrieval. Finally, we apply a relevance feedback to the initial retrieved images from the image retrieval system. In the experiment using the image database of 16 class about 2,400 images, the proposed method shows the better retrieval performance than that of the conventional approach without the relevance feedback.
鄭性煥,兪昌道,金善政 大田産業大學校 2000 한밭대학교 논문집 Vol.17 No.1
A study has been conducted experimentally on natural convection heat transfer characteristics of a heating flat plate with heat diffusion fins in air. The effects of heat diffusion fin lengths, heating plate temperature, air velocity, and Rayleigh numbers are mainly investigated. The mean heat transfer coefficient decreases as a dimensionless fin length increases and heating place temperature 60℃ is the best at constant heat flux. The mean Nusselt number increases with increasing Rayleigh number and Reynolds number and H/S = 1.0 in the dimensionless fin length is found to be the optimun size in a tested length, 1.0≤H/S≤4.0
CDMA망에서 시스템 용량과 트래픽 부하의 변화를 반영한 핸드오프 영역 비율에 대한 성능분석
정성환,홍정완,이상천,이창훈 대한산업공학회 2007 산업공학 Vol.20 No.2
In code-division multiple-access (CDMA) systems with soft handoff, mobile station (MS) within soft handoff region can use multiple radio channels and receive their signals from multiple base stations (BSs) simultaneously. In this paper, the effects of soft handoff region ratio (SHRR) on reverse link of a CDMA cellular system are analytically investigated. In order to analyze the network performance and quality of service (QoS) perceived by users more realistically, both the soft capacity increasing factor and the traffic load variation affected by SHRR are jointly considered and a two-dimensional continuous time Markov chain (CTMC) model is built. In the numerical example, it is observed that the optimal guard channel exists according the variations of the traffic load and propagation conditions when the proper value of SHRR is determined.
정성환,김자영,강병전,박종오,김창세 제어로봇시스템학회 2021 제어로봇시스템학회 국내학술대회 논문집 Vol.2021 No.6
This paper suggests magnetic steerable guiding device for a leadless pacemaker. In the case of a general leadless pacemaker, a pacemaker guidance device is used for implantation. The pacemaker guidance device safely moves the pacemaker to the implant position of the heart and provides the force and torque needed for the pacemaker implantation.