• 한국산학기술학회논문지
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• 제18권12호
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• pp.729-734
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• 2017

안전릴리프밸브는 배관라인 혹은 탱크의 과도한 압력을 완화하고 사용 적정압력 수준으로 유지해주는 장치이다. 안전릴리프밸브는 스프링 보닛에 통풍구가 대기 쪽으로 혹은 배출구 쪽으로 뚫려 있는지에 따라 배압의 변화에 직접적으로 영향을 받게 된다. 배압은 축적 배압(Built-up back pressure)과 부과 배압(superimposed back pressure)으로 나뉘게 되며 사용조건에 따라 배압의 특성이 달라진다. 본 연구에서 사용되는 안전밸브는 Conventional Safety Relief Valve로써, 배압의 특성을 가정하였다. 또한 개방력과 스프링력 사이의 힘의 평형 방정식을 세워 이론적 접근방법으로 초기 스프링 변위를 구하였다. 디스크가 받는 반력 즉 개방력과 스프링력을 비교하여 블로우 다운을 예측하였다. 블로우 다운은 설정 압력과 디스크 재닫힘 압력 간의 차이다. 본 연구는 ASME 규격 코드에 따라서 블로우 다운 시험 전에 전산 유동해석프로그램 CFX17.1을 이용하여 수치적으로 예측하였음을 밝힌다. 또한 유체-구조 연성해석(fluid-structure interaction analysis)을 통해 안전밸브 트림부의 안전성을 검토하였다. 향후, 시험과 전산수치해석 값을 서로 비교하여 블로우 다운 이론적 접근방법과 유동해석방법을 제안하고자 한다.

• 융합신호처리학회논문지
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• 제24권2호
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• pp.82-89
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• 2023

선박 구조 특성상 격실 구조는 복잡하고 협소하여 작업 과정에서 안전사고가 빈번히 발생하고 있다. 사고의 주된 원인은 구조물 충돌, 낙하물, 독성물질 누출, 화재, 폭발, 질식 등이 존재한다. 사고 발생 시 작업자의 현장 상황을 파악하는 것이 피해를 완화하는 요소 중 하나이다. 이에 안전성을 확보하기 위해 선박 내 CCTV로 현장 상황을 모니터링하고 있으나, 기존의 방식으로는 사고를 예방하기엔 어려움이 있다. 이를 해결하기 위해 안전 기술로 위치 식별, 음성/영상 통신 기능이 탑재되는 스마트 안전모가 개발 중에 있다. 또한, 작업 구역 내 환경 정보 수집 및 저장기능을 포함한 온도, 습도, 진동, 소음, 기울기(자이로 센서), 가스 센서를 사용하여 스마트 안전모를 착용한 작업자에게 위험 상황을 알릴 수 있다. 이를 통해 스마트 안전모 및 환경 센서의 사용으로 선박 내 작업자의 안전성을 강화할 수 있을 것이다.

• 한국안전학회지
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• 제18권1호
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• pp.101-107
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• 2003

Dynamic behavior of flexible rectangular liquid storage structures is analysed by the developed method. The rectangular liquid storage structures are assumed to be fixed to the ground and a moving coordinate system is used. The irrotational motion of invicid and incompressible ideal fluid is represented by two analytic solutions. One is the solution of the fluid motion in the rigid rectangular liquid storage structure due to ground motions and the other is the solution of the fluid motion by the motion of the wall in the flexible rectangular liquid storage structure. The motion of structure is modeled by finite elements. The fluid-structure interaction effect is reflected into the coupled equation of motion as added fluid mass matrix. The free surface sloshing motion and hydrodynamic pressure acting on the wall in the flexible rectangular liquid storage structure due to the horizontal ground motion are obtained by the developed method and verified.

• 한국안전학회지
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• 제19권4호
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• pp.109-116
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• 2004

The dynamic behavior of the rectangular liquid storage structure is known to be greatly influenced by fluid-structure interaction. By mounting the liquid storage structure on the properly designed base isolators, dynamic response of the superstructure can be reduced. However, base isolators inevitably incur large displacement of the structure to the ground ·ind may give adverse effects on the sloshing height. This paper presents the analysis method for fluid-structure-isolator interaction in base-isolated rectangular liquid storage structures. In the method, the irrotational motion of invicid and incompressible ideal fluid is expressed by analytic solutions and the superstructure and isolators are properly modeled by finite element and bilinear model. Free surface sloshing motion, hydrodynamic pressure acting on the wall and structural response are obtained by the presented method.

• Wind and Structures
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• 제31권5호
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• pp.381-392
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• 2020

Despite that the failure of sign structure may not have disastrous consequence, its sheer number still ensures the need for rigorous safety standard to regulate their maintenance and construction. During its service life, a sign structure is subject to extensive wind load, sometimes well over its permissible design load. A fragility analysis of a sign structure offers a tool for rational decision making and safety evaluation by using a probabilistic framework to consider the various sources of uncertainty that affect its performance. Wind fragility analysis was used to determine the performance of sign structure based on the performance of its connection components. In this study, basic wind fragility concepts and data required to support the fragility analysis of the sign structure such as sign panel's parameters, connection component's parameters, as well as wind load parameters were presented. Fragility and compound fragility analysis showed disparity between connection component. Additionally, reinforcement of the connection system was introduced as an example of the utilization of wind fragility results in the retrofit decision making.

• Composites Research
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• 제26권4호
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• pp.259-264
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• 2013

본 연구에서는 기계적 전기적 기능을 모두 만족하는 다중대역 스킨구조물에서의 복사 소자를 2중 사출으로 제작하였다. 추후 외부 스킨 구조 변형에 따른 복사 소자의 안정성을 검증하기 위하여 충격 및 좌굴에 대한 시험과 축 하중과 전단 하중에 대한 강도 해석을 실시하였다. 그리고 다중 대역 안테나 스킨 구조의 복사 소자에 대한 실험적 방법과 해석적 방법을 통한 강도 분석 결과, 구조의 허용 하중을 예측하고 충격과 좌굴에 대한 안정성을 평가할 수 있었다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 춘계학술대회논문집
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• pp.51-56
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• 2005

For a fire cause judgement this paper describes the short circuit characteristics of a electric wire through the cross section analysis under ac condition. The cower wires prepared for the experiment were 1.2mm, 1.6mm, and 2.0mm in diameter. Through the cross section analysis(CSA), it was confirmed that the dendrite structure grew at the angle of about $40^{\circ}\;or\;60^{\circ}$ when the fusing current was applied to the wires. The larger the fusing current is, the more decreased the growth angle of the dendrite structure is. It was confirmed that the dendrite structure was arranged like the columnar structure. In this paper, the characteristics analysis of short circuit was carried out in the range of transient duration and the correlation constant k was investigated by measuring the short circuit duration and the fusing current.

• International Journal of Concrete Structures and Materials
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• 제11권2호
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• pp.403-413
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• 2017

Residual axial capacity from numerical analysis was widely used as a critical indicator for damage assessment of reinforced concrete (RC) columns subjected to blast loads. However, the convergence of the numerical result was generally based on the displacement response, which might not necessarily generate the correct post-blast results in case that the strain softening behavior of concrete was considered. In this paper, two widely used concrete models are adopted for post-blast analysis of a RC column under blast loading, while the calculated results show a pathological mesh size dependence even though the displacement response is converged. As a consequence, a nonlocal integral formulation is implemented in a concrete damage model to ensure mesh size independent objectivity of the local and global responses. Two numerical examples, one to a RC column with strain softening response and the other one to a RC column with post-blast response, are conducted by the nonlocal damage model, and the results indicate that both the two cases obtain objective response in the post-peak stage.

• Computers and Concrete
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• 제27권1호
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• pp.1-12
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• 2021

This work presents a safety assessment of an underground tunnel subjected to a ballistic missile attack employing the numerical approach. For the impact simulation, a box shaped reinforced concrete (RC) structure with a cross section dimension of 8.0×10.0 m under a soil layer that was attacked by a SCUD missile was modeled using finite element (FE) software LS-DYNA. SCUD missile is one of a series of tactical ballistic missiles developed by Soviet Union during the Cold War, which is adopted for a short-range ballistic missile. The developed FE simulation for the penetration depth of the missile impacting into the soil structure was verified from the well-known formula of the penetration prediction. The soil-structure interaction, the soil type, and the impact missile velocity effects on the penetration depth of the missile into the different soil types were investigated. The safety assessment of the underground tunnel was performed with regard to the different depths of the underground tunnel. For each missile velocity and soil type, a specific depth called the unsafe depth was obtained from the analysis results. The structure beneath the soil beyond this depth remains safe. The unsafe depth was found to be increased with the increasing missile velocity.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.4033-4041
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• 2021

To better understand the permeability of uranium sandstone, improve the leaching rate of uranium, and explore the change law of pore structure characteristics and blocking mechanism during leaching, we systematically analyzed the microstructure of acid-leaching uranium sandstone. We investigated the variable rules of pore structure characteristics based on nuclear magnetic resonance (NMR). The results showed the following: (1) The uranium concentration change followed the exponential law during uranium deposits acid leaching. After 24 h, the uranium leaching rate reached 50%. The uranium leaching slowed gradually over the next 4 days. (2) Combined with the regularity of porosity variation, Stages I and II included chemical plugging controlled by surface reaction. Stage I was the major completion phase of uranium displacement with saturation precipitation of calcium sulfate. Stage II mainly precipitated iron (III) oxide-hydroxide and aluminum hydroxide. Stage III involved physical clogging controlled by diffusion. (3) In the three stages of leaching, the permeability of the leaching solution changed with the pore structure, which first decreased, then increased, and then decreased.