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플라즈마 이온질화에 의한 Fe 나노분말소결체의 표면경화 가능성 연구
윤준철,이재성,Yun, Joon-Chul,Lee, Jai-Sung 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.1
This study has been performed on the full density sintering of Fe nanopowder and the surface hardening by plasma ion nitriding. The Fe sintered part was fabricated by pressureless sintering of the Fe nanopowder at $700^{\circ}C$ in which the nanopowder agglomerates were controlled to have 0.5-5 ${\mu}m$ sized agglomerates with 150 nm Fe nanopowders. The green compact with 46% theoretical density(T.D.) showed a homogeneous microstructure with fine pores below 1 ${\mu}m$. After sintering, the powder compact underwent full densification process with above 98%T.D. and uniform nanoscale microstructure. This enhanced sintering is thought to be basically due to the homogeneous microstructure in the green compact in which the large pores are removed by wet-milling. Plasma ion nitriding of the sintered part resulted in the formation of ${\gamma}$'-$Fe_4N$ equilibrium phase with about 12 ${\mu}m$ thickness, leading to the surface hardening of the sintered Fe part. The surface hardness was remarkably increased from 176 $H_v$ for the matrix to 365 $H_v$.
가변위치 고음성인식 기술을 이용한 무선 홈 네트워크 시스템 구현에 관한 연구
윤준철,최상방,박찬섭,김세영,김기만,강석엽,Yoon, Jun-Chul,Choi, Sang-Bang,Park, Chan-Sub,Kim, Se-Yong,Kim, Ki-Man,Kang, Suk-Youb 한국정보통신학회 2010 한국정보통신학회논문지 Vol.14 No.4
실내 환경에서 음성인식 기술을 이용한 무선 홈 네트워크 시스템 구현에 있어, 잡음과 실내 잔향음은 시스템 성능 저하의 주요 원인이다. 본 연구에서는 실내 인식환경에서 스펙트럼 엔트로피(Spectral entropy) 기반의 음성 구간검출법을 이용하여 잔향음(reverberation) 및 실내잡음에 강인한 음성인식 홈 네트워크 시스템을 구현하고자 한다. 스펙트럼 차감법(Spectral Subtraction)은 잔향으로 인해 왜곡된 신호를 스펙트럼 상에서 제거하여 잔향의 효과를 줄일 수 있고 음성신호와 독립적인 잡음을 제거 할 수 있다. 효과적인 스펙트럼 차감을 위해서는 음성과 비음성 구간의 정확한 구분이 수반되어야 하며 이를 위해서 엔트로피 기반의 음성 구간 검출법을 적용하여 성능을 향상시킨다. 모의 및 실내환경 실험 결과 Spectral entropy 기반의 음성 구간 검출법을 이용할 경우 실내 잔향 및 잡음환경에서 명령어 인식률의 향상이 증명되었다. In realization of wireless home network system using speech recognition in indoor voice recognition environment, background noise and reverberation are two main causes of digression in voice recognition system. In this study, the home network system resistant to reverberation and background noise using voice section detection method based on spectral entropy in indoor recognition environment is to be realized. Spectral subtraction can reduce the effect of reverberation and remove noise independent from voice signal by eliminating signal distorted by reverberation in spectrum. For effective spectral subtraction, the correct separation of voice section and silent section should be accompanied and for this, improvement of performance needs to be done, applying to voice section detection method based on entropy. In this study, experimental and indoor environment testing is carried out to figure out command recognition rate in indoor recognition environment. The test result shows that command recognition rate improved in static environment and reverberant room condition, using voice section detection method based on spectral entropy.
윤준철,김용호,최유미,김명수 한국경영과학회 2022 한국경영과학회 학술대회논문집 Vol.2022 No.6
In the power systems, interoperability is performed through conformance evaluation and interconnection evaluation based on information models. There are many interoperability assessment models proposed in various areas. However, the preliminary steps for performing these procedures are still structured and operated in document format. This paper proposes a level measurement procedure based on the interoperability assessment model as a preliminary step for conformance evaluation and interconnection evaluation in the power systems.
미성숙 난자의 체외 성숙 시 다양한 체세포의 공동 배양 효과
윤준철,김은혜,황선웅,채련,현상환 韓國受精卵移植學會 2014 한국동물생명공학회지 Vol.29 No.1
Recent 2 decades, including in vitro maturation (IVM), assisted reproductive technologies (ARTs) achieved noteworthy development. However the efficiency of ARTs with in vitro matured oocytes is still lower than that with in vivo oocytes. To overcome those limitations, many researchers attempted to adapt co-culture system during IVM and consequently maturation efficiency has been increased. The beneficial effects of applying co-culture system is contemplated base on communication and interaction between various somatic cells and oocytes, achievement of paracrine factors, and spatial effects of extracellular matrix (ECM) from somatic cell surface. The understanding of co-culture system can provide some information to narrow the gap between in vitro and in vivo. Here we will review current studies about issues for understanding cu-culture system with various somatic cells to improve in vitro maturation microenvironment and provide bird view and strategies for further studies.
윤준철,이재성 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.3
This study investigates the synthesis of SmFe intermetallic compounds by a solid state reduction-diffusion process (R-D process) using a mixture of Sm2O3-CaH2 ball-milled powders and Fe nanopowders. The Sm2O3-CaH2-Fe mixed powders were subjected to heat treatment under a switched gas atmosphere from Ar-5 vol.%H2 to a vacuum atmosphere during the R-D process at 800 οC. It was found that the SmFe intermetallic phases of Sm2Fe17 and SmFe3 were effectively formed in a switched gas atmosphere and observed on the surface of the sintered Fe nanopowder agglomerate. This formation occurred because the sintering of agglomerated Fe nanopowders occurred at a low temperature of about 500 οC earlier before the Sm dissociated from SmH2 was diffused into the sintered Fe nanopowders agglomerate during the R-D process. The Sm2Fe17 phase of the target alloy was identified having a rhombohedral Th2Zn17-type (2:17 R) structure with a grain size of 400-800 nm. It is expected that the Sm2Fe17 nanopowders can be effectively fabricated by controlling the initial powder characteristics such as size refinement and mixing homogeneity
젖염소 분방 유즙에서 분리한 세균 및 항균제 감수성 조사
윤준철,이정치,김상기,박영석,김종택,이정길,이채용,Yoon, Joon-chul,Lee, Jeong-chi,Kim, Sang-ki,Park, Young-seok,Kim, Jong-taek,Lee, Chung-gil,Lee, Chai-yong 대한수의학회 2004 大韓獸醫學會誌 Vol.44 No.1
Samples of milk were collected from 425 halves of 216 dairy goats in Chonnam province over a period of January through August 2003. Bacterial isolation was carried out on those samples, and their antimicrobial susceptibility was tested. Bacteria were isolated from 166 milk samples (39.1%), either singly (74.7%) or in combination (25.3%). Of the 220 isolates, Staphylococcus spp. was the most prevalent (82.6%), followed by Streptococcus spp. (2.7%), Corynebacterium spp. (1.8%), Enterococcus spp. (1.8%), and Pasteurella spp. (1.8%). Of the 11 species identified from the 182 isolates of Staphylococcus spp., the most frequent species identified were S. epidermidis (28.6%) followed by S. chromogens (14.8%), S. haemolyticus (12.6%), S. aureus (12.1%), S. capitis (8.2%), S. lentus (8.2%), S. hyicus (4.4%), S. simulans (4.4%), S. caprae (2.8%), S. hominis (2.8%) and S. warneri (1.1%). Antimicrobial sensitivity test revealed that most isolates were highly susceptible to 11 antimicrobial agents (96.4 ~ 80.9%), while most isolates were resistant to penicillin.