• Steel and Composite Structures
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• 제20권1호
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• pp.21-41
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• 2016

Cold-formed steel structures are increasingly attractive due to their benefits of good mechanical performance and constructional advantages. However, this type of construction is still not fully exploited as a result of the acknowledged difficulties involved in forming construction-efficient and cost-effective connections. Furthermore, there is a lack of information on the structural behavior of the cold-formed steel connections. In this study, the research on various cold-formed steel connections was comprehensively reviewed from both fundamental and structural points of view, based on the available experimental and analytical data. It reveals that the current design codes and guidelines for cold-formed steel connections tend to focus more on the individual bearing capacity of the fasteners rather than the overall structural behavior of the connections. Significant future work remains to be conducted on the structural performance of cold-formed steel connection. In addition, extensive previous research has been carried out to propose and evaluate an economical and efficient connection system that is obtained from the conventional connecting techniques used in the hot-rolled industry. These connecting techniques may not be suitable, however, as they have been adopted from hot-rolled steel portal frames due to the thinness of the sheet in cold-formed steels. The review demonstrates that with the increasing demand for cold-formed steel constructions throughout the world, it is crucial to develop an efficient connection system that can be prefabricated and easily assembled on site.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.300-310
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• 2008

A series of numerical simulations on the several types of breakwaters on the foundation systems utilizing buoyancy were carried out in plane-strain conditions using the modified Cam-Clay model and the Biot's consolidation theory. Improved foundation system by the replacement of original ground with light weighted material, expandable poly-styrene (called below EPS) and several foundation systems with buoyant cells were used. From the results of numerical simulations we found that the foundation systems utilizing buoyancy are efficient to reduce the maximum consolidation settlements without reducing lateral safety.

• Structural Engineering and Mechanics
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• 제44권4호
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• pp.417-429
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• 2012

Taking the superficial temperature increment as the major fatigue damage indicator, the infrared thermography was used to predict fatigue parameters (fatigue strength and S-N curve) of welded joints subjected to fatigue loading with a high mean stress, showing good predictions. The fatigue damage status, related to safety evaluation, was tightly correlated with the temperature field evolution of the hot-spot zone on the specimen surface. An energetic damage model, based on the energy accumulation, was developed to evaluate the residual fatigue life of the welded specimens undergoing cyclic loading, and a good agreement was presented. It is concluded that the infrared thermography can not only well predict the fatigue behavior of welded joints, but also can play an important role in health detection of structures subjected to mechanical loading.

• 한국안전학회지
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• 제32권1호
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• pp.75-81
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• 2017

A series of laboratory experiments has been performed in order to investigate the behavior of water-air two-phase flow in a horizontal pipe. A conductivity meter has been applied to detect the irregular alternation of air at the specific points in flows. The experimental condition has been established according to the water and air flowrates. Passing time, which is the time length for a measuring probe to pass through the entire length of a specific bubble, has been defined to evaluate the size of bubbles in the flow. Passing length, which can be considered as the equivalent value to bubble size and determined from the product of passing time and cross-sectional averaged velocity, and its corresponding occurrence frequency have been analyzed to classify the air flow patterns according to the condition of air and water fluxes. From the result, the dependancy of flow patterns on the variation of air-water flux ratio has been investigated and the existence of thresholds also checked for classifying the behavior of air in the flow.

• 치위생과학회지
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• 제11권4호
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• pp.311-317
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• 2011

본 연구는 2005년도에 실시된 제 3기 국민건강영양조사 자료를 이용하여 어린이의 생활안전행동과 구강보건행동의 관련성을 알아보고 사회인구학적 연관 요인을 평가하여 어린이의 생활안전행동와 구강보건행동을 효과적으로 증진하기 위한 기본 방향을 세우고자 수행되었다. 본 연구를 통하여 우리나라 어린이들의 생활안전행동과 구강보건행태에 대하여 다음과 같은 결론을 얻었다. 1. 대체로 어린이의 생활안전행동과 구강보건행동의 연관성이 발견되지 않았고 따라서 어린이의 생활안전행동과 구강보건행동의 변화를 추구함에 있어서 공통위험요인접근법 적용의 근거를 발견하지 못하였다. 2. 우리나라 3-11세 어린이는 56.3%가 하루 2회 이상 칫솔질을 실천하였고 74.7%가 예방적 치과진료 경험이 있는 것으로 나타났다. 자동차 뒷좌석 이용을 제외한 생활안전행동의 실천은 현저하게 부족하여 자동차 보호장구 이용율 10.4%, 자전거 안전모 착용율 4.3%, 및 인라인스케이트 안전모 착용율 29.0%에 그쳐(Table 2), 특히 생활안전교육의 강화의 필요성이 절실함을 보여주었다. 3. 미취학 어린이에 비하여 7세 이후 취학어린이에게서 생활안전행동과 구강보건행동의 실천률이 낮은 것으로 조사되어, 초등학생의 생활안전교육과 구강보건교육이 강조되어야 할 것으로 사료된다. 4. 3-6세 아동에서 거주지역 또는 가정의 경제수준 등 사회경제적 요인과 생활안전행동 및 구강보건행동의 연관성이 관찰되었으나, 취학아동에서는 대체로 유의한 연관성이 없었다(Table 3).

• 디지털융복합연구
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• 제14권3호
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• pp.279-285
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• 2016

나노기술이 발전함에 따라 나노물질의 사용량이 증가하고, 그에 따른 환경 및 인체 유해성 문제가 사회적 이슈로 대두되고 있으나 나노물질에 대한 규제나 법규는 아직 제정되어 있지 않다. 이에 본 연구에서는 WPMN에서 지정한 제조나노물질 13종 중 국내에서 가장 많이 사용되고 있는 물질인 aluminium oxide의 거동평가를 실시하여 연구활동종사자들을 위한 안전지침의 기초 자료로 활용하고자 하였다. 실험은 실제 연구실을 1/6의 크기로 축소하여 제작한 chamber에서 진행되며, NIOSH method 0500에 준하여 질량농도를 측정하였다. 연구 결과 질량 농도는 물질의 입자 크기에 반비례하는 것으로 나타났으며, 환기 설비의 작동만으로 질량농도가 약 1/8배까지 감소하는 것을 확인 할 수 있었다. 본 연구를 향후 나노물질 관련 연구활동종사자를 위한 안전지침의 기초자료로 활용할 수 있을 것으로 보이나, 연구의 신뢰도를 높이기 위해 입경에 따른 질량농도, 수농도 측정등의 실험이 필요할 것으로 사료된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1181-1192
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• 2008

A laboratory investigation was carried out into effects of strain rate on undrained shear behavior of Holocene clay underneath Kobe Airport with an objective to evaluate the factor of safety of the retaining structure built on it. It was examined in a series of triaxial compression and extension tests performed using different rate of axial straining. A comparative compression test in which the strain rate was changed in steps was also carried out. Similar tests were performed in constant-volume direct shear box (DSB) test. And, the deformation characteristics of the clay were also examined in order to evaluate the variation of stiffness during undrained shearing. It was found that the undrained strength increased with not only the shear rate but also the consolidation period. ISOTACH properties seemed a key to govern the undrained shear behavior.

• Nuclear Engineering and Technology
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• 제49권2호
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• pp.360-372
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• 2017

Many advanced reactor designs rely on passive systems to fulfill safety functions during accident sequences. These systems depend heavily on boundary conditions to induce a motive force, meaning the system can fail to operate as intended because of deviations in boundary conditions, rather than as the result of physical failures. Furthermore, passive systems may operate in intermediate or degraded modes. These factors make passive system operation difficult to characterize within a traditional probabilistic framework that only recognizes discrete operating modes and does not allow for the explicit consideration of time-dependent boundary conditions. Argonne National Laboratory has been examining various methodologies for assessing passive system reliability within a probabilistic risk assessment for a station blackout event at an advanced small modular reactor. This paper provides an overview of a passive system reliability demonstration analysis for an external event. Considering an earthquake with the possibility of site flooding, the analysis focuses on the behavior of the passive Reactor Cavity Cooling System following potential physical damage and system flooding. The assessment approach seeks to combine mechanistic and simulation-based methods to leverage the benefits of the simulation-based approach without the need to substantially deviate from conventional probabilistic risk assessment techniques. Although this study is presented as only an example analysis, the results appear to demonstrate a high level of reliability of the Reactor Cavity Cooling System (and the reactor system in general) for the postulated transient event.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전기설비전문위원
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• pp.231-232
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• 2008

The surface made of dielectric materials can therefore become probable sites for damaging electrostatic discharges. Thanks to a specially equipped chandler, the spatial environment can be reproduced experimentally in the laboratory. In this paper, the behavior of high energy electrons injected in polymers such as PolyMethylMetaAcrylate (PMMA) and Kpton is studied. Results obtained by surface potential technique, pulse-electro acoustic device and a cell based on the split Faraday cup system are analyzed and discussed.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2011년도 춘계학술논문발표회 논문집
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• pp.397-401
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• 2011