• 대한기계학회논문집A
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• 제35권6호
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• pp.629-633
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• 2011

항공기, 철도, 선박과 같은 대형 시스템들은 전기, 기계적으로 매우 복잡한 구조를 가졌으며 부품의 수명만을 고려한 기존의 유지보수에서 탈피하여, 고장분석의 시스템화를 통해 장치의 고유수명과는 관계없이 발생 가능한 우발고장도 대처할 수 있는 신뢰성 기반의 유지보수체계를 연구하여야 한다. 본 연구에서는 선행연구로 필요한 복합 시스템의 신뢰도 계산방법에 관한 연구이다. 복합 시스템의 신뢰도를 효과적으로 계산하기 위해 시스템의 RBD(Reliability Block Diagram)를 구성하고 인접행렬을 사용하여 RBD(Reliability Block Diagram)를 행렬로 표현한다. 또한 RBD(Reliability Block Diagram)행렬을 통하여 신뢰도 경로행렬과 고장열거 행렬을 구성하여 시스템의 신뢰도를 계산한다. 본 연구에서 제안한 알고리즘은 자동화, 시스템화가 가능하며 현재 개발하고 있는 신뢰도 정보관리 시스템 및 신뢰성 기반 유지보수 시스템에서 활용될 것이다.

• Composites Research
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• 제12권6호
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• pp.31-42
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• 1999

항공우주산업에서 무게를 증가시키지 않고 비행구조물의 구조적 성능을 증가시키는 것은 굉장한 잇점을 갖는다. 본 연구에서는 복합재료 평판의 무게를 증가시키지 않고 좌굴하중과 인장 파단하중을 동시에 증가시키는 혁신적인 설계 방법에 대해서 연구하였다. 원공이 있는 복합재료 적층판에서 곡선 섬유층과 직선 섬유층을 조합하여 적층판을 구성할 때 좌굴하중과 인장파단 하중이 동시에 증가되는 현상에 대하여 유한요소 해석을 사용하여 알아보았다. 원공의 크기와 적층 순서를 달리하면서 곡선섬유를 이용한 효과가 얼마나 되는지 알아보았다. 또한, 각각의 경우에 대해서 파단이 어떻게 일어나는가도 관찰하였다. 곡선섬유 평판을 제작하기 위해서는 연속적이고 부드럽게 변하는 fiber path가 필요하다. 여기서는 유한요소로 구한 섬유 방향을 사용하여 제작이 가능한 부드럽게 이어지는 fiber path를 구하는 간단한 방안을 제시하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.92-96
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• 2005

Among the failure modes which can be occurred in tube hydroforming such as wrinkling, bursting or buckling, the bursting by local instability under excessive tensile stresses is irrecoverable phenomenon. Thus, the accurate prediction of bursting condition plays an important role in producing the successfully hydroformed part without any defects. As the classical forming limit criteria, strain-based forming limit diagram has widely used to predict the failure in sheet metal forming. However, it is known that the FLD is extremely dependant on strain path throughout the forming process. Furthermore, the path-dependent limitation of FLD makes the application to hydroforming process, where strain path is no longer linear throughout forming process, more careful. In this work, stress-based forming limit diagram (FLSD), which is strain path-independent and more general, was applied to prediction of forming limit in tube hydroforming. Combined with the analytical FLSD determined from plastic instability theory, finite element analyses were carried out to find out Ihe state of stresses during hydroforming operation, and then FLSD is utilized as forming limit criterion. In addition, the approach is verified with a series of bulge tests in view of bursting pressure and shows a good agreement. Consequently, it is shown that the approach proposed in this paper will provide a feasible method to satisfy the increasing practical demands for judging the farming severity in hydroforming processes.

• 한국통신학회논문지
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• 제26권11C호
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• pp.85-93
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• 2001

본 논문에서는 전광 통신망에서 장애 위치에 독립적인 경로 복구 방법을 제안하고 그 필요 파장 수를 계산한다. 제안된 방법에서는 모든 링크 장애에 대해 하나의 대체 파장만을 이용하기 때문에 고정 파장 송수신기만을 사용한 수가 있어 노드 구축 경비를 줄인 수 있다. 또한 운용 경로와 대체 경로가 공유되지 않는다면 장애의 위치에 관계없이 대체 경로와 대체 파장이 사전에 결정되어 장애의 검출만으로 복구 과정이 바로 시작될 수 있다. 이러한 특징과 제안되는 병렬 크로스커넥션을 수행하도록 하는 메시지 전달 기법을 사용하면 복구 과정을 간단하고 빠르게 만들 수 있다. 그리고 제안된 복구 방법에서 필요한 파장 수를 계산하고 필요한 파장 수가 가변 대체 파장을 사용하는 복구 방법에서 필요한 파장 수와 서로 비슷함을 보임으로써 전송 경비의 증가 또한 거의 없음을 보인다.

• Structural Engineering and Mechanics
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• 제3권5호
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• pp.475-495
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• 1995

In the past, physical models have been proposed, in compliance with the concept of the compressive-force path, for the realistic design of various statically determinate structural concrete members. The present work extends these models so as to encompass indeterminate RC structural forms. Pilot tests conducted on continuous beams and fixed-ended portal frames have revealed that designing such members to present-day concepts may lead to brittle types of failure. On the other hand, similar members designed on the basis of the proposed physical models attained very ductile failures. It appears that, unlike current design approaches, the compressive-force path concept is capable of identifying those areas where failure is most likely to be triggered, and ensures better load redistribution, thus improving ductility. The beneficial effect of proper detailing at the point of contraflexure in an indeterminate RC member is to be noted.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.622-627
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• 1996

Detailed analysis of Feedwater Line Break (FLB) event for the fuel failure point of view are lack because the event was characterized as the increase in reactor coolant system (RCS) pressure. Up to now, the potential of the rapid system heatup case has been emphasized and comprehensively studied. The cooldown effects of FLB event is considered to be bounded by the Steam Line Break (SLB) event since the cooldown effect of SLB event is larger than that of the FLB event. This analysis provides a new possible path which can cause the fuel failure. The new path means that the fuel failure can occur under the heatup scenario because the Pressurizer Safety Valves (PSVs) open before the reactor trips. The 1000 MWe typical C-E plant FLB event assuming Loss of Offsite Power (LOOP) at the turbine trip has been analyzed as an example and the results show less than 1% of the fuel failure. The result is well within the acceptance criteria. In addition to that, a study was accomplished to prevent the fuel failure for the heatup scenario case as an example. It is found that giving the proper pressure gap between High Pressurizer Pressure Trip (HPPT) analysis setpoint and the minimum PSV opening pressure could prevent the fuel failure.

• Advances in Computational Design
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• 제6권1호
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• pp.1-13
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• 2021

Failure of a Multi-storeyed reinforced concrete framed structure occurs when a primary vertical structural component is isolated or made fragile, due to artificial or natural hazards. Load carried by vertical component (column) is transferred to neighbouring columns in the structure, if the neighbouring column is incompetent of holding the extra load, this leads to the progressive failure of neighbouring members and finally to the failure of partial or whole structure. The collapsing system frequently seeks alternative load path in order to stay alive. One of the imperative features of collapse is that the final damage is not relative to the initial damage. In this paper, the effect on the column and beam adjacent to statically removed vertical element in terms of axial force, shear force and bending moment is investigated. Using Alternate load path method, numerical modelling of two dimensional one bay, two bay with variation in storey heights are analysed with FE model in order to obtain better understanding of failure mechanism of multi-storeyed reinforced concrete framed structure. The results indicate that the corner column is more susceptible to progressive collapse when compared to middle column, using this simplified methodology one can easily predict how the structure can be made to stay alive in case of sudden failure of any horizontal or vertical structural element before designing.

• 한국방재학회 논문집
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• 제5권3호
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• pp.67-72
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• 2005

본 연구는 건축물내의 완전 암흑상태에서 축광유도타일이 피난에 미치는 영향을 측정하기 위하여 조사하였다. 실험조사는 대구 Fire EXPO '05에 실험 장치를 전시하여 엑스포 관람자 520명을 대상으로 2005년 5월 26일부터 29일까지 실시되었다. 실험 조사결과 안전 암흑상태일 때 피난자세는 남자의 경우 70%, 여자는 72%가 벽을 더듬으며 피난한 반면에 축광유도타일이 설치된 경우에는 남자의 경우 88%, 여자의 경우 83%가 선채로 피난을 한 것으로 나타났다. 공공건물의 바닥에 축광유도타일을 설치하면 화재시 정전이 되더라고 평소와 다름없이 피난을 할 수 있는 것으로 나타났다.

• International journal of advanced smart convergence
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• 제10권1호
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• pp.56-61
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• 2021

Neighbor path selection is to pre-select alternate routes in case geographically correlated failures occur simultaneously on the communication network. Conventional heuristic-based algorithms no longer improve solutions because they cannot sufficiently utilize historical failure information. We present a novel solution model for neighbor path selection by using machine learning technique. Our proposed machine learning neighbor path selection (ML-NPS) model is composed of five modules- random graph generation, data set creation, machine learning modeling, neighbor path prediction, and path information acquisition. It is implemented by Python with Keras on Tensorflow and executed on the tiny computer, Raspberry PI 4B. Performance evaluations via numerical simulation show that the neighbor path communication success probability of our model is better than that of the conventional heuristic by 26% on the average.

• Safety and Health at Work
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• 제5권1호
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• pp.1-6
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• 2014

Background: Workflow interruptions during surgery may cause a threat to patient's safety. Workflow interruptions were tested to predict failure in action regulation that in turn predicts near-accidents in surgery and related health care. Methods: One-hundred-and-thirty-three theater nurses and physicians from eight Swiss hospitals participated in a cross-sectional questionnaire survey. The study participation rate was 43%. Results: Structural equation modeling confirmed an indirect path from workflow interruptions through cognitive failure in action regulation on near-accidents (p < 0.05). The indirect path was stronger for workflow interruptions by malfunctions and task organizational blockages compared with workflow interruptions that were caused by persons. The indirect path remained meaningful when individual differences in conscientiousness and compliance with safety regulations were controlled. Conclusion: Task interruptions caused by malfunction and organizational constraints are likely to trigger errors in surgery. Work redesign is recommended to reduce workflow interruptions by malfunction and regulatory constraints.