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전병혁,김단비,박순동,김찬중 한국초전도.저온공학회 2014 한국초전도저온공학회논문지 Vol.16 No.1
The effects of Mg content on the pore formation, density and critical properties were investigated in in-situ reacted MgB2 superconductors. The Mg1+xB2, (x=-0.2, 0.0, 0.05, 0.3, 1.0) bulk samples with different Mg contents were heat-treated at 900°C for 1 h in an Ar atmosphere. The dimensional changes of a pellet's mass and volume after heat-treatment were measured. After heat-treatment process, the sample mass was decreased by Mg evaporation, but the sample volume was expanded by pore formation at the Mg site; therefore, the apparent density was decreased. Spherical pores the same as Mg particles were developed after heat-treatment in all samples, and the pore density was increased with increasing Mg content. As the x of Mg content was increased to 1.0, the apparent density of Mg1+xB2 samples was decreased due to a relatively larger reduction in a mass change. The critical current density of Mg excessive sample of x=0.05 showed the highest values over the applied magnetic fields because the excessive Mg may compensate Mg loss and enhance grain connectivity
全炳赫,金成德 한밭대학교 산업과학기술연구소 1993 논문집 Vol.1 No.-
In this paper, we describe the electronic circuit design of a spectrophotometer which can measure the reflection, transmission and absorption of lighting in a sample material or the characteristics of an emitting device. The visible and ultraviolet light can be obtained from a Halogen lamp and a Deuterium lamp. In order to detect the insensity of the light generated by such light sources. Multi Channel Photodiode array Detector(MCPD) is used. The MCPD has good properties such as high speed of data translation, wide spectral response and many sampling data per unit time compared to the other commercial light detectors. Direct Memory Access(DMA) method adapted to this spectrophotometer can be designed to read as well as write serially data in the memory. The DMA can be serially and parallelly interfaced with a computer via RS232C. Moreover, it is designed a software to the given network system. The constructed spectrophotometer was calibrated by using SRM2009 and 2031 which are waveform calibrating materials in KRISS. After the performances for several samples was measured by the designed spectrophotometer, the results show good spectral resolution and responsibility.
기계적 밀링 및 글리세린 처리된 보론 분말을 사용하여 제조된 $MgB_2$의 임계전류밀도 향상
전병혁,김이정,김찬중,Jun, Byung-Hyuk,Kim, Yi-Jeong,Kim, Chan-Joong 한국초전도학회 2008 Progress in superconductivity Vol.10 No.1
A combined process of a mechanical ball milling and liquid glycerin ($C_{3}H_{8}O_3$) treatment of boron (B) powder has been conducted to enhance the superconducting properties of $MgB_2$. The individual aims of the mechanical milling and the glycerin treatment were to reduce the grain size of the $MgB_2$ and to achieve homogeneous carbon (C) incorporation into the $MgB_2$, respectively. Four kinds of B powders of as-received, glycerin treated, 2 h milled, and 2 h milled + glycerin treated were prepared. $MgB_2$ bulks were fabricated by in situ process using the prepared B powders. The mechanical ball milling was effective for a grain refinement, and a lattice disorder was easily achieved by glycerin addition. It was found that the critical current density ($J_c$) values were enhanced in the samples with milled B or glycerin treated B only. In the $MgB_2$ bulk prepared with both milled and glycerin treated B, the $J_c$ was further increased due to a higher grain boundary density and a greater C substitution.
밀리미터파 대역용 유전체 소재와 자유공간법에 의한 특성평가기술 연구개발 동향
전병혁,한진우,김동영,이상석,Jun, B.H.,Hahn, J.W.,Kim, D.Y,Lee, S.S. 한국전자통신연구원 1999 전자통신동향분석 Vol.14 No.5
최근 정보사회에 따른 전파수요가 높아지고 있으며 이에 따른 주파수의 요구가 점차 고주파화되고 있고 미개척분야인 밀리미터파의 개발이 중요한 과제로 대두되고 있다. 본 고에서는 밀리미터파 대역 수동부품용 세라믹 유전체 소재에 관한 동향을 서술하였으며, 이 대역에서 세라믹 소재의 유전특성을 측정, 평가하는 여러 방법 중에서 자유공간법을 이용한 기술에 관하여 소개하고자 한다.
MOCVD 법에 의해 제조된 YBCO 초전도 박막의 물성에 대한 완충층 템플릿의 영향
전병혁,최준규,김찬중,Jun, Byung-Hyuk,Choi, Jun-Kyu,Kim, Chan-Joong 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1
[$YBa_2Cu_3O_{7-x}$] thin films were deposited on various buffered-templates by a metal organic chemical vapor deposition(MOCVD). Three different templates of $CeO_2/YSZ/CeO_2/pure-Ni(CYC),\;CeO_2/YSZ/Y_2O_3/Ni-3at.%W(YYC)$ and $CeO_2/IBAD-YSZ$/stainless steel were used. The Ni and Ni-W alloy tapes were biaxially textured by cold rolling and annealing heat treatment. The dense YBCO films were grown on both the IBAD and YYC templates with no microcrack, while the YBCO films on the CYC templates were grown with the formation of microcracks and NiO. The YBCO film on the YYC template showed the higher $I_c$ than that on CYC template. Especially, the IBAD templates with a thin $CeO_2$(type I) and thick $CeO_2$(type II) top layer were used to compare the deposition nature of the YBCO on them. Comparing the current property of the YBCO films on IBAD templates, the YBCO film deposited on thick $CeO_2$ layer was better than the film on thin $CeO_2$ layer.
MOCVD 법에 의해 제조된 $CeO_2$ 버퍼층 증착 거동의 기판 의존성
전병혁,최준규,정우영,이희균,홍계원,김찬중,Jun, Byung-Hyu,Choi, Jun-Kyu,Jung, Woo-Young,Lee, Hee-Gyoun,Hong, Gye-Won,Kim, Chan-Joong 한국초전도학회 2006 Progress in superconductivity Vol.7 No.2
Buffer layers such as $CeO_2\;and\;Yb_2O_3$ films for YBCO coated conductors were deposited on (100) $SrTiO_3$ single crystals and (100) textured Ni substrates by a metal organic chemical vapor deposition (MOCVD) system of the hot-wall type. The substrates were moved with the velocity of 40 cm/hr. Source flow rate, $Ar/O_2$ flow rate and deposition temperature were main processing variables. The degree of film epitaxy and surface morphology were investigated using XRD and SEM, respectively. On a STO substrate, the $CeO_2$ film was well grown epitaxially above the deposition temperature of $450^{\circ}C$. However, on a Ni substrate, the XRD showed NiO (111) and (200) peaks due to Ni oxidation as well as (111) and (200) film growth. For the films deposited with $O_2$ gas as oxygen source, it was found that the NiO film was formed at the interface between the buffer layer and the Ni substrate. The NiO layer interrupts the epitaxial growth of the buffer layer. It seems that the epitaxial growth of the buffer layer on Ni metal substrates using $O_2$ gas is difficult. We are considering a new method avoiding Ni oxidation with $H_2O$ vapor instead of $O_2$ gas.