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- 저자 : 노재승 ( J. S. Roh ) (검색결과 5 건)
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산화반응에 의한 이방성 메조페이스 탄소섬유의 구조 변화(I) - TEM 및 XRD를 이용한 분석
노재승,Roh, J.S. 한국재료학회 2003 한국재료학회지 Vol.13 No.12
Structural changes during oxidation of anisotopic mesophase carbon fiber(AMCFs) have been observed with TEM and XRD. It was shown that the AMCFs are three dimensionally stacked structure of turbostratic layers, and are non-homogeneous structure which consist of the highly ordered areas and the random areas. The $d_{ 002}$, Lc, and La of AMCFs which were measured by XRD were 3.44, 146, and $135\AA$, respectively. It was observed that the oxidation initiated at the random areas, because the $d_{002}$ / decreased to the value of 3.41 $\AA$ during initial oxidation stage. It was also observed that the La of the oxidized AMCFs increased up to 182 $\AA$ during the whole oxidation process, and the $d_{002}$ of that increases up to 9.44 $\AA$ when the burn-off is over the degree of 20%. Therefore, it was suggested that the micro-crystalline grew up by heat treatment effects during the fibers were oxidized, In addition, it was shown that there was difference in the measured value of La by XRD and TEM, in case of 39% oxidized fibers for example, the measured La was $ 165\AA$ by XRD and in the range of 180∼220 $\AA$ by TEM.
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이산화탄소를 이용한 등방성 탄소섬유의 활성화과정 중 발생하는 구조변화(II)-TEM을 이용한 분석
노재승,Roh, J.S. 한국재료학회 2003 한국재료학회지 Vol.13 No.11
A development of micropores of $CO_2$activated isotropic carbon fibers from TEM was observed. It was observed that the micropores of activated carbon fibers(ACFs) were consisted of slit-shaped pores(SP) and cylinder-shaped pores(CP). The SPs were formed between two parallel-carbon layers, and the CPs were formed at a place which is connected polygonally by more than two carbon layers. It was shown that the CPs of the ACFs were developed at high degree of burn-offs and at high activation temperature. The pore size distribution of the best ACF, which was observed at a highest value of specific surface area(3,495 $\m^2$/g), showed a continuous distribution in the range of about $4∼l5\AA$, and the median pore size was 6.7$\AA$. The super-high specific surface area of ACFs was found to be due to that the SPs were connected with a maximum size of 7∼8$\AA$ continuously, It is possible that the SPs should be formed in the ACFs in order to show super-high SSA.
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노재승(Jea-Seung Roh),신원철(Won-Chul Shin),박현규(Hyun-Kyu Park),박영택(Young-Tack Park) 한국정보과학회 2021 정보과학회논문지 Vol.48 No.4
지식 그래프는 실세계의 지식을 다양한 소스로부터 수집하여 구조화된 방식으로 표현한 것이다. 지식 그래프는 데이터들 간의 관계를 표현한 네트워크로서 인공지능 기술에 접목되어 다양하게 활용되고 있지만, 엔티티 또는 엔티티 사이의 링크가 누락되어 지식의 불완전성에 대한 문제가 존재한다. 이러한 문제 해결을 위해 자동 지식 완성 기법 연구가 중요하게 요구되며, 임베딩 기법을 사용하거나 딥러닝을 활용한 연구와 온톨로지를 이용한 심볼릭 규칙 추론을 통한 지식 완성 수행과 같은 다양한 연구들이 진행되었다. 이러한 방식을 통해 효율적으로 자동 지식 완성을 수행하지만 딥러닝 방식은 데이터 기반의 처리방식으로 인해 대량의 학습 데이터가 요구되며, 결과에 대한 설명이 불가능한 문제점이 있다. 그리고 온톨로지 기반의 방식은 전문가에 의해 정의된 온톨로지 및 규칙이 필요하다는 문제가 존재한다. 따라서 본 논문에서는 뉴로 심볼릭 방식을 이용하여 데이터에 내포된 규칙을 명시적으로 추출하여 자동 지식 완성방법을 제안한다. 규칙 추출을 위해 심볼릭 방식의 단일화(unification) 기반의 릴레이션 임베딩 경로를 구현하고, 이에 대한 손실 함수를 정의하여 자동으로 규칙을 생성한다. 기존의 임베딩 기법에 비하여 뉴로 심볼릭 방식은 속도와 성능이 더 우월함을 보여준다. 제안하는 방법의 성능을 측정하기 위해 Nations, UMLS, Kinship 데이터 셋을 대상으로 최신 지식 완성 연구와 비교 실험을 진행하였으며, 학습 시간이 크게 감소했고, 평균적으로 성능이 37.5%p 증가한 것을 확인하였다. A knowledge graph is a structured representation of real-world knowledge and is designed by collecting information from various sources. These knowledge graphs are networks that represent relationships between data and are applied in various fields of artificial intelligence; however, there exists problems related to incomplete knowledge due to the omission of entities or omission links between the entities. To resolve the problems, research on automatic knowledge completion techniques is necessitated. Consequently, various studies have been examined including embedding techniques, deep learning or symbolic rule inference using ontology. Although automatic knowledge completion can be efficiently performed through the above-mentioned methods, deep learning methods require a large amount of learning data due to data-driven processing methods, and there exist problems related to the results that are hard to explain. Futhermore, ontology-based methods require ontology and rules that are defined by the experts. To overcome this limitation, in this study, we propose an automatic knowledge completion method by explicitly extracting the implicit rules from the data based on the Neuro-Symbolic method. For rule extraction, we have implemented a symbolic unification based embedding path and defined a cost function for it to automatically generate the rules. Compared with the approaches presented in previous embedding studies, the proposed method demonstrates the superiority of the Neuro-Symbolic method concerning speed and performance. To assess the performance of the proposed method, for datasets like Nations, UMLS, and Kinship, experiments were conducted in comparison with the approach of the state-of-the-art knowledge completion studies. Consequently, an immense reduction in the training time and 37.5%p increase in the average performance were observed.
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스파크 플라즈마 소결법으로 제조된 Sr - 페라이트의 특성
노재승(J. S. Roh),오명훈(M. H. Oh) 한국자기학회 2003 韓國磁氣學會誌 Vol.13 No.1
Anisotropic Sr-ferrites were prepared by the spark plasma sintering process (SPS). The Ferrite particles were oriented and densified during sintering process, and the anisotropic ferrites were manufactured at low sintering temperature and a remarkable short time processing by SPS method. It was showed that the anisotropy of ferrite particles at the specimen outer side was more higher than that at the specimen center, and it seems possible that the orientation of ferrite particles was related to DC current. Magnetic and physical properties of sintered Sr-ferrites are Br = 3.15 kG, iHc = 2.67 kOe, and density = 5.033 g/㎤ when the samples were sintered for 8 minutes at 1060℃.
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