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초고속 디지털 회로의 GBN 억제를 위한 육각형 EBG 구조의 전원면 설계
김선화,주성호,김동엽,이해영,Kim, Seon-Hwa,Joo, Sung-Ho,Kim, Dong-Yeop,Lee, Hai-Young 한국전자파학회 2007 한국전자파학회논문지 Vol.18 No.2
본 논문에서는 초고속 디지털 PCB 회로에서 발생하는 GBN(Ground Bounce Noise)을 억제하기 위한 새로운 EBG(Electromagnetic Bandgap) 구조의 전원면을 제안하였다. 제안된 구조는 육각형 모양의 단위 셀과 각 셀을 연결하는 선로로 구성되어 있다. 육각형 모양의 단위 셀은 등방성을 띄어 인접 셀의 각 포트 사이의 전달 특성을 동일하게 한다. 제안된 구조는 실제 제작, 측정되었고 330 MHz부터 5.6 GHz까지 넓은 주파수 대역에서 -30 dB 이하로 GBN을 억제하는 특성을 나타낸다. Electromagnetic Interference(EMI) 방사 측정 시에도 일반 전원면/접지면에 비해 낮은 EMI 특성을 나타낸다. 본 논문에서 제안한 육각형 EBG 구조의 전원면은 실제 EBG 전원면의 적용에 효율적으로 작용하여 초고속 디지털 회로의 EMI 문제를 해결하는 데 기여할 것으로 기대된다. In this paper, a novel hexagonal-shaped electromagnetic bandgap(EBG) power plane for the suppression of the ground bounce noise(GBN) in high-speed circuits is proposed. The proposed structure consists of hexagonal-shaped unit cells and detoured bridges connecting the unit cells. The hexagonal-shaped unit cells could omni-directionally suppress the GBN in digital circuits. The fabricated power plane's omni-directional -30 dB suppression bandwidth is from 330 MHz to 5.6 GHz. Then the proposed structure suppresses electromagnetic interference(EMI) caused by the GBN within the stopband. As a result, the proposed structure is expected to be conducive solving EMI problem in high-speed circuits.
2024 Al 합금의 ECAP 공정에 따른 미세조직 변화와 강도특성
김선화,최용락,Kim, Seon-Hwa,Choi, Yong-Lak 한국재료학회 2006 한국재료학회지 Vol.16 No.1
2024 Al alloys were severely deformed by equal channel angular pressing(ECAP) to obtain an ultrafine grain structure. The more deformation amount increased, the more grain size decreased. Most of the grain structure were changed from elongated to equiaxed shape with increasing pass number. The morphology of S' phases was also changed from rod-type to spherical type. The grain size of 6 passed specimen was 100 to 200 nm, and the size of S' phases was about 10 nm in the microstructure. XRD measurements have revealed that the texture formed by plastic deformation disappeared in the 6 passed specimen. SP test results described that the start of crack propagation occurred at the transition zone between plastic bending and membrane stretching because of small elongation. The maximum strength of ECA pressed specimen increased 1.9 GPa to 2.9 GPa with increasing pass number.
퇴화처리(RRA)한 Al-Li 8090 합금의 미세조직에 관한 연구
김선화,이종권,Kim, Seon-Hwa,Lee, Jong-Gwon 한국재료학회 1995 한국재료학회지 Vol.5 No.5
Al 8090합금의 퇴화처리시에 나타나는 금속간화합물 변화과정과 PFZ 생성 및 입계석출물의 거동을 TEM을 사용하여 조사하였다. 기지에서는 $\delta$상, T$_{1}$ 상과 S'상이 모든 시편에서 관찰되었고, 입계어슨 PFZ이 형성되었다. 본 연구에 사용된 Al합금의 초기PFZ의 생성 기구는 입계의 임계공공 농도에 의한 것으로 나타났다. 2단계 열처리시 시간이 2분 이상이면 입계에 석축물이 형성되었다. 입계에는 중간단계로 5회전대칭축을 가지는 준안전상의 icosahedral상의 생성되었다. 평형 입계석출물은 사방정의 $Al_{13}$Fe$_{4}$였다.
급랭응고한 Al-Fe-V-Si계 합금의 미세조직과 열안정성에 관한 연구
김선화,박원욱,Kim, Seon-Hwa,Park, Won-Wook 한국현미경학회 1991 Applied microscopy Vol.21 No.2
The main purpose of this paper was to investigate the change of rapidly solidified microstructures and dispersoid behavior according to heat-treatment in the Al-Fe-V-Si-(Mn) alloys. It was found that (111) preferred orientation identified by X-ray diffraction and fine subgrain/large grain were observed in the rapidly solidified Al-Fe-V-Si-(Mn) alloys. Cell boundary of the zone A was composed of the microcrystalline, whereas that of the zone B was amorphous. Decomposition of the Al-Fe-V-Si-(Mn) alloys occurred at about $300^{\circ}C$. These alloys exhibited excellent thermal stability at the elevated temperature. Microstructure of the zone B was more stable than that of the zone A. The spherical dispersoid and 5-fold symmetry phase was also more thermally stable than the amorphous structure of cell boundary.
식물병원성 및 곰팡이 독성 Fusarium 방제를 위한 생물학적 방제제 Sphaerodes mycoparasitica
김선화 ( Seon Hwa Kim ) 한국환경농학회 2022 한국환경농학회 학술대회집 Vol.2022 No.-
Fusarium Head Blight (FHB) is one of the most important plant diseases affecting cereal crops such as wheat and barley. A group of Fusarium species including F. avenaceum (Fr.) Sacc., F. culmorum, F. oxysporum Schltdl., and F. graminearum Schwabe, is well known as devastating plant pathogens resulting in significant losses in seed germination, grain yield, and grain quality eventually leading to negative impacts on global food safety and security. With growing world’s population and expanding needs for environmentally friendly solution, scientific interests in biological control facilitated searching for potential biocontrol agents. Sphaerodes mycoparasitica was isolated from the wheat field in an association with F. avenaceum and F. graminearum. During the initial investigation on S. mycoparasitica, S. mycoparasitica was found to be a Fusarium specific mycoparasite which was partly proven by the mycoparasite-host cell-to-cell replacement and interface changes in F. graminearum. In addition, S. mycoparasitica showed that the level of adaptability and host compatibility strongly relied on the types of Fusarium filtrates. Further, morphological changes including alteration of fungal surface hydrophobicity of the host during mycoparasitism, with the different degree of host compatibility demonstrated that Sphaerodes mycoparasitica possesses diphasic mycoparasitism which derived from biotrophic-attraction relationship or antagonistic-inhibition relationship. More importantly, the ability of S. mycoparasitica to degrade or transform Fusarium mycotoxins was demonstrated through biodegradation experiments implying reduction in mycotoxin-related risks. On top of that, S. mycoparasitica showed the protective effect on the germinating wheat seeds by maintaining seed vigor and suppressing growth of F. graminearum insinuating possibility of an early preventive biocontrol measure on cereal crops against FHB. Taken together, S. mycoparasitica is suggested to be develop as a promising biocontrol agent for managing FHB and/or Fusarium-associated risks.