• Journal of Advanced Marine Engineering and Technology
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• 제22권4호
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• pp.490-497
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• 1998

An elast-biscoplastic finite element analysis is performed to investigate detailed growth behavior of creep cracks and the numerical results are compared with experimental results. The results of mesh translation method are compared with those of node release method. Load line displancement curve obtained from the crack growth analysis by mesh translation shows the improved results than that obtained from the crack growth by node release method when the secondary creep rate is only used as creep material property. The results of accounting for primary creep rate and instantaneous plasticity shows a good agreement with the experimental result.

• 전자공학회논문지A
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• 제30A권5호
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• pp.1-15
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• 1993

In DQDB networks, the bandwidth can be increased considerably be using the EN(Erasure Node) algorithms and DR(Destination Release) algorithms. However, the important issue in implementing them is using method of extra capacity fairly. To improve it, this paper proposes AEN(Adaptive Erasure Node) algorithm which erasure function is activated by network traffic load. Its functional architecture consists of SESM, RCSM, LMSM in addition to the basic DQDB state machines (DQSM, RQM). The SESM and RCSM state machines are placed in front of the DQSM and RQM state machines in order for the node to take advantage of the newly cleared slots. This paper also presents some simulation results showing the effect of AEN algorithm on access delay, throughput and segment erasing ratio in the single and multiple priority networks. The results show that the AEN algorithm offer the better performance characteristics than existing algorithms under overload conditions.

• 한국통신학회논문지
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• 제35권1A호
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• pp.16-24
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• 2010

HSUPA(High Speed Uplink Packet Access)는 고속 스케줄링, HARQ, 짧은TTI등을 Node B에서 제공함으로써 HSDPA 에 대응되게 상향링크 쪽의 고속 데이터 전송률을 제공하는 WCDMA의 Rel 6 이동통신 기술이다. WCDMA 시스템의 RNC(Radio Network Controller)와 기지국인 Node B 간의 Iub 구간에서 혼잡을 검출하는 것은 사용자의 통신서비스 품질을 높이기 위해서 매우 중요하다. 이를 위해 TNL 혼잡 검출과 Node B의 링크 버퍼 관찰 방법을 제안하고 이를 통해 얻을 수 있는 패킷 수율에 대해 성능 분석을 하였다. 제안하는 방법을 통해 좁은 Iub 대역폭의 혼잡 검출은 패킷 수율 향상에 도움이 되는 것을 확인할 수 있었다.

• Journal of Advanced Marine Engineering and Technology
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• 제18권5호
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• pp.68-77
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• 1994

The authors apply the transfer influence coefficient method to the 3-dimensional vibration analysis of beam with multi-joints and formulate a general algorithm to analysis the longitudinal, flexural and torsional coupled free vibration. In this paper, the structure, which is mainly founded in the robot arms, cranes and so on, has some crooked parts, subsystems and joints but has no closed loop in this system. It is modeled as the beam of a distributed mass system with massless translational, rotational and torsional springs in each node, and joint elements of release or roll at which node the displacement vector is discontinuous. The superiorty of the present method to the transfer matrix method in the computation accuracy was confirmed by the numerical computation results. Moreover, we confirmed that boundary and intermediate conditions could ve controlled by varying the values o the spring constants.

• Journal of Advanced Marine Engineering and Technology
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• 제21권3호
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• pp.256-266
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• 1997

The authors apply the transfer influence coefficient method to the 3. dimensional vibration analysis of beam with multi - joints and formulate a general algorithm to analyse the longitudinal, flexural and torsional coupled forced vibration. In this paper, a structure which is mainly found in the robot arms, cranes and so on, has some crooked parts, subsystems and joints, but has no closed loop in this system. It is modeled as the beam of a distributed mass system with massless translational, rotational and torsional springs in each node, and joint elements of release or roll at node which the displacement vector is discontinuous. The superiority of the present method to the transfer matrix method in the computation accuracy was confirmed from the numerical computation results. Moreover, we confirmed that boundary and intermediate conditions could be controlled by varying the values of the spring constants.

• 한국해양공학회지
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• 제16권6호
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• pp.55-59
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• 2002

Delamination means that cracking occurs on the interface layer between composite laminates. In this paper, to predict the delamination growth in composite laminates subjected to low-velocity impact, the unit load method was introduced, and an eighteen-node 3-D finite element analysis, based on assumed strain mixed formulation, was conducted. Strain energy release rate, necessary to determine the delamination growth, was calculated by using the virtual crack closure technique. The unit load method saves the computation time more than the re-meshing method. The virtual crack closure technique enables the strain energy release rate to be easily calculated, because information of the singular stress field near the crack tip is not required. Hence, the delamination growth in composite laminates that are subjected to low-velocity impact can be efficiently predicted using the above-mentioned methods.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1996년도 추계학술대회논문집; 한국과학기술회관, 8 Nov. 1996
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• pp.203-209
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• 1996

The authors apply the transfer influence coefficient method to the 3-dimensional vibration analysis of beam with multi-joints and formulate a general algorithm to analysis the longitudinal, flexural and torsional coupled forced vibration. In this paper, a structure, which is mainly founded in the robot arms, cranes and so on, has some crooked parts, subsystems and joints but has no closed loop in this system. It is modeled as the beam of a distributed mass system with massless translational, rotational and torsional springs in each node, and joint elements of release or roll at which node the displacement vector is discontinuous. The superiority of the present method to the transfer matrix method in the computation accuracy was confirmed from the numerical computation results. Moreover, we confirmed that boundary and intermediate conditions could be controlled by varying the values of the spring constants.

• Structural Engineering and Mechanics
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• 제50권5호
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• pp.665-677
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• 2014

A numerical method, using a special mixed finite element associated with the virtual crack extension technique, has been developed to evaluate the energy release rate for kinking cracks. The element is two dimensional 7-node mixed finite element with 5 displacement nodes and 2 stress nodes. The mixed finite element ensures the continuity of stress and displacement vectors on the coherent part and the free edge effect. This element has been formulated starting from a parent element in a natural plane with the aim to model different types of cracks with various orientations. Example problems with kinking cracks in a homogeneous material and bimaterial are presented to assess the computational accuracies.

• 한국통신학회논문지
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• 제30권9B호
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• pp.581-590
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• 2005

근거리망의 이더넷 기술과 도시망에 적합한 링 토폴로지를 결합하여 성능이 뛰어나고 고장에 강하며 근거리망과의 호환성을 유지하는 RPR(Resilient Packet Ring)이 도시망의 핵심기술로 뜨오르고 있다. IEEE 802.11에서 RPR에 대한 표준화가 완성중인데, 공평한 대역폭의 사용을 보장하기 위해 설계된 RPR의 공정성 제어기법이 비대칭 과부하 트래픽 환경에서 성능저하를 초래하는 문제점을 안고 있다. 본 논문에서는 이러한 성능저하 문제를 해결하기 위해 체증해제 통보 기반의 공정성 제어방식을 제안하고 이의 성능을 분석한다. 제안된 방식에서는 체증 발생노드가 자신의 체증해제 여부를 판단하여 상단노드로 통보하면 상단노드는 하단노드의 체증을 해소하기 위해 제한하였던 자신의 트래픽 전송속도를 즉시 원래의 속도로 복구한다. 제안된 방식은 종래의 공정성 제어방식과 호환성을 가지며 체증해제 임계값의 선택에 의해 성능저하의 정도를 임의대로 조정할 수 있다.

• 한국전산구조공학회논문집
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• 제27권1호
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• pp.17-26
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• 2014

본 논문은 MLS(Moving Least Squares) 차분법을 바탕으로 동적균열전파 해석을 수행하기 위한 알고리즘을 제시한다. MLS 차분법은 절점만으로 이루어진 수치모델을 사용하며, 이동최소제곱법을 이용하여 전개한 Taylor 다항식을 기초로 미분근사식을 유도하기 때문에, 요소망의 제약에서 완벽하게 벗어난 절점해석이 가능하다. 시간항을 포함하는 동적 평형방정식은 Newmark 방법으로 시간적분 하였다. 동적하중을 받는 균열이 전파할 때, 매 시간단계마다 절점모델을 재구성하지 않고 균열선단 주변에서 국부적인 수정을 통해 해석이 가능하다. 동적균열을 묘사하기 위해 가시한계법(visibility criterion)을 적용하였고, 동적 에너지해방률을 산정하여 균열의 진전유무와 그에 상응하는 진전방향을 결정하였다. 모드 I 상태와 혼합모드 상태에서 균열이 진전하는 현상을 모사하였고, 이론해와 Element-Free Galerkin법으로 계산한 결과와의 비교를 통해 개발된 알고리즘의 정확성과 안정성을 검증하였다.