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EPON에서 실시간 트래픽의 지연성능 향상을 위한 동적 대역할당방안의 성능분석
박철근,이유태,정해,유건일,김종안,Park, Chul-Geun,Lee, Yu-Tae,Chung, Hae,You, Geon-Il,Kim, Jong-An 한국통신학회 2003 韓國通信學會論文誌 Vol.28 No.11B
본 논문에서는 서로 다른 요구조건을 갖는 응용 서비스들을 지원하는 가입자 접속망에서 서비스 고유의 서비스 품질을 효과적으로 지원하기 위한 대역 할당 방안을 다룬다. 음성 및 실시간 비디오 등의 지연에 민감한 실시간 트래픽과 데이터 및 BE(Best Effort)와 같은 비 실시간 트래픽 등 다중 응용 서비스를 지원해야 하는 EPON(Ethernet Passive Optical Network)망에서 상향 트래픽의 동적 대역 할당방안에 대하여 논하기로 한다. 구조적으로 제한된 자원 환경에서 상향 전송 대역을 효율적으로 사용하고, 실시간 트래픽의 지연성능을 향상하는 새로운 방안을 제안하고, 시뮬레이션으로 제안된 방안의 지연성능을 분석한다. In this paper, we deal with an effective dynamic bandwidth allocation(DBA) scheme in order to support the qualify of services (QoS) in the customer access network which supports various applications with own service requirements. we discuss the DBA scheme for upstream traffic in the EPON which support both the delay sensitive traffic such as voice and real-time video and non-real time traffic such as data and BE. We propose the new DBA scheme which guarantee the delay performance of the real time traffic and utilize the upstream bandwidth effectively in the limited resource environment. We analize the delay performance of the proposed scheme by simulation.
Iosipescu Shear Test를 이용한 고분자 복합재료의 종방향 전단계수 연구
정태헌(Tae-Heo Jeong),권용수(Yong-Su Kwon),이유태(You-Tae Lee),이동주(Dong-Joo Lee) 한국산업융합학회 2000 한국산업융합학회 논문집 Vol.3 No.1
Effective shear modulus of continuous fiber reinforced polymeric composites is measured using a modified Iosipescu Shear Test(IST) and compared with data obtained by finite element analyses that a concept of unit cell is. It is found that the numerical results of the longitudinal shear modulus give a good agreement with experimental data at lower fiber volume fraction. In this paper, both the distance and stress transfer between the fibers are discussed as the major factors.<br/>
SMC 복합재료와 Carbon/Epoxy 복합재료의 파괴인성평가
최영근(Young-Geun Choi),이유태(You-Tae Lee),이택순(Taik-Soon Lee) 한국해양공학회 1993 韓國海洋工學會誌 Vol.7 No.1
In composite materials, the fracture perpendicular to the fiber direction usually shows a non-linear behavior accompannying blunting and plastic deformation around the crack tip.<br/> In this study, the fracture thoughness in random short fiber SMC composite material and Carbon/Epoxy composite material is estimated by the A.M.(Area Method) and the G.L.M.(Generalized Locus Method) which can determine a stable total energy release rate(GT) not only in highly elastic material but also in highly non-linear materials.
多重 過荷重에 의한 Al 7075-T6 合金의 疲勞龜裂 成長遲延現狀에 관한 硏究
李澤淳(Taik-Soon Lee),李侑泰(You-Tae Lee) 한국해양공학회 1992 韓國海洋工學會誌 Vol.6 No.1
Aircraft structures and engineering structures are always subject to variable amplitude loads. Variable amplitude loads include some kind of loading history ; for example, constant amplitude load, single peak overload and block overload etc. Crack growth under variable amplitude loading exhibits retardation effect.<br/> In this study, the 4 point bending fatigue test was performed by hydrolic servo fatigue testing machine on 7075-T6 Al-alloy.<br/> The retardation effect of overload ratio and numbers of overload cycle was quantitatively studied.<br/> 1) Change of retardation effect against increment of overload ratio is more evident when the multiple overload is applied than single overload is done.<br/> 2) The number of overload cycle is very important factor about the crack growth retardation effect when the overload ratio is more than 1.75 ; that is not when the overload ratio is less than 1.75.<br/> 3) Overload affected zone size increased gradually by increment of crack growth retardation effect.<br/> 4) Crack driving force is more greatly reduced when the crack tip branched off two direction than it sloped to one direction.
2.25Cr-1Mo 강의 피로균열 전파특성에 미치는 미세구조 변화와 하중비의 영향에 관한 연구
김형진,이유태,김상태 嶺南大學校 工業技術硏究所 1995 工業技術硏究所論文集 Vol.23 No.1
The effects of load ratio and microstructural change on fatigue crack propagation behavior for 2.25Cr-1Mo steel were evaluated. Fatigue tests were conducted at frequency of 10Hz, and the load ratio of 0.05, 0.1, 0.3 and 0.5 for the specimens heat treated in the temperature range from 400℃ to 800℃. The value of threshold stress intensity range decreased with increasing tempering temperature and with increasing the load ratio. The observed threshold levels and crack growth behavior were explained with crack closure phenomena induced by plasticity and oxide particles.