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개도율에 따른 가스파이프라인용 볼 밸브 후류유동의 수치평가
김철규,이상문,장춘만,KIM, CHUL-KYU,LEE, SANG-MOON,JANG, CHOON-MAN 한국수소및신에너지학회 2018 한국수소 및 신에너지학회논문집 Vol.29 No.4
Ball valve has been widely used in the field of high-pressure gas pipeline as an important component because of its low flow resistance and good leakage performance. The present paper focuses on the flow nature at the downstream of the ball valve used for gas pipelines according to valve opening rates. Steady 3-D RANS equations, SC/Tetra, have been introduced to analyze the flow characteristics inside the ball valve. Numerical boundary conditions at the inlet and outlet of the valve system are imposed by mass flow-rate and pressure, respectively. Velocity distributions obtained by numerical simulation are compared with respect to the valve opening rates of 30, 50, and 70%. Cavity distributions, asymmetry flow velocity and the flow stabilization point at each opening rate are also compared. When the valve opening rates are 30 and 50%, the flow stabilization requires the sufficient length of 10D or more due to the influence of the recirculation flow at the downstream of the valve.
김철규,전우평,박진일,김동주,최해천,Kim, Chul-Kyu,Jeon, Woo-Pyung,Park, Jin-Il,Kim, Dong-Joo,Choi, Haecheon 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.9
In this study, the modification of turbulent boundary layer flow by local wall vibration is investigated. The wall is locally vibrated using a wall deformation actuator, which moves up and down at the frequencies of 100Hz and 50Hz. Simultaneous measurements of the streamwise velocities in the spanwise direction are performed at several wall-normal and streamwise locations using an in-house multi-channel hot wire anemometer and a spanwise hot-wire-probe rake. The mean velocity is reduced in most places due to the wall vibration and its reduced amount becomes small as flow goes downstream. Interestingly, the mean velocity is found to increase very near the wall and near the actuator. This is due to the motion induced by the streamwise vortices which are generated by the downward motion of the actuator. In case of the streamwise velocity fluctuations, their magnitude increases as compared to the unperturbed turbulent boundary layer, and the increased amount becomes small as the flow moves downstream. The modified flow field at the forcing frequency of 50Hz is not much different from that of 100Hz, except the reduced amount of modification.
계층적 Mobile IPv6에서의 이동노드를 기반으로 한 경로 개선방법에 관한 연구
김철규(Kim chul-kyu),김정석(Kim jung-suk),김정호(Kim jeong-ho) 한국콘텐츠학회 2004 한국콘텐츠학회 종합학술대회 논문집 Vol.2 No.1
경로 최적화를 기본으로 한 Mobile IPv6의 바인딩 갱신은 자주 이동하는 노드에 의해 시그널 링 트래픽 증가를 초래한다. 이를 보완하기 위해 MAP(Mobile Anchor Point)를 두어 매크로 이동성과 마이크로 이동성의 지역적 이동성을 고려한 계층적 Mobile IPv6가 제안되었다. 그러나 계층적 Mobile IPv6는 패킷 전송에 있어서 MAP를 항상 거쳐야 하므로 MAP의 패킷 집중현상이 발생하고 경로 최적화를 보장하지 못한다. 이에 본 연구에서는 이동 노드의 이동성을 고려한 경로 개선을 수행하여 MAP로의 패킷 집중현상의 완화특성을 해석한다. The binding update of the Mobile IPv6 which does a route optimization in basic by the node which moves frequently brings about the signaling traffic increase of binding update. It supplements this the MAP(Mobile Anchor Point) for to let, and Hierarchical Mobile IPv6 which considers a macro mobility and a micro rambling regional mobility was proposed. But Mobile IPv6 when transmitting the packet, always does to pass by the MAP, the packet intensive actual condition of the MAP to occur it does not guarantee a route optimization. In this study, It accomplishes the course improvement which considers the mobility of mobile node and it interprets the relaxation quality of packet intensive actual condition with the MAP.
2016년 영국 신문의 브렉시트(Brexit) 관련 텍스트에 관한 코퍼스 언어학적 분석
김철규 ( Kim Chul-kyu ) 한국현대언어학회 2017 언어연구 Vol.33 No.1
This paper describes an analysis of 2 million word corpora taken from British newspapers in 2016, which refer to the issue of Brexit. The impetus of the research is to describe such social change as Brexit in linguistic terms, especially corpora and their keywords. Two corpora were built: Corpus A was compiled from news articles before the Brexit referendum, and Corpus B from articles after the referendum. Both corpora were compared to British Natinal Corpus (BNC) to identify any similarities between Corpora A and B, and were then compared to each other in order to identify differences between them. The analysis showed that the keywords from both the corpora typically contained names of major politicians and events relevant to the issue of Brexit. It also showed that changes in the political situation, around the time of the referendum, were well reflected in the keywords of both the corpora. Finally, the contents of the corpora were predicted through categorizing the keywords using Wmatrix. (Kyungsung University)
코퍼스에 기반한 영국 신문의 논설문과 한국 대학생의 영어 논설문에 사용된 메타담화(metadiscourse) 비교 연구
김철규(Kim Chul-Kyu) 담화·인지언어학회 2009 담화와 인지 Vol.16 No.3
Metadiscourse is known as a group of linguistic devices that the writer uses for helping readers process the information of a text more efficiently(textual metadiscourse) and engaging them in the argument of the text by constructing textual interaction explicitly(writer-reader’s interpersonal metadiscourse). The purpose of the present research is to investigate variations in the use of English metadiscourse in terms of the authors’ English language proficiency. For this, two corpora are built on the texts from two groups of writers: argumentative texts written by professional columnists in a British newspaper(The Guardian) and L2 English argumentative texts written by Korean university students. In order to neutralize topic effect, the texts that deal with the single topic of environmental issues are collected. The analysis reveals that the Korean students used more metadiscoursal devices. However, there is also a quantitative difference as well: the British writers used more writer-reader’s interpersonal metadiscourse, whereas the Koreans employed more textual metadiscourse. The reasons of these differences seem to be due to the writers’ rhetorical competence in developing ideas in texts on one hand and due to their awareness of constructing writer-reader interaction in text on the other. Finally, this work suggests some important implications for English language writing classes: raising learners’ awareness of constructing textual interaction can lead to an enhancement of their textual competence.