• Earthquakes and Structures
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• 제11권6호
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• pp.925-942
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• 2016

With ongoing development of earthquake engineering research and the lessons learnt from a series of strong earthquakes, the seismic design concept of "resilience" has received much attention. Resilience describes the capability of a structure or a city to recover rapidly after earthquakes or other disasters. As one of the main features of urban constructions, tall buildings have greater impact on the sustainability and resilience of major cities. Therefore, it is important and timely to quantify their seismic resilience. In this work, a quantitative comparison of the seismic resilience of two tall buildings designed according to the Chinese and US seismic design codes was conducted. The prototype building, originally designed according to the US code as part of the Tall Building Initiative (TBI) Project, was redesigned in this work according to the Chinese codes under the same design conditions. Two refined nonlinear finite element (FE) models were established for both cases and their seismic responses were evaluated at different earthquake intensities, including the service level earthquake (SLE), the design-based earthquake (DBE) and the maximum considered earthquake (MCE). In addition, the collapse fragility functions of these two building models were established through incremental dynamic analysis (IDA). Based on the numerical results, the seismic resilience of both models was quantified and compared using the new-generation seismic performance assessment method proposed by FEMA P-58. The outcomes of this study indicate that the seismic resilience of the building according to the Chinese design is slightly better than that according to the US design. The conclusions drawn from this research are expected to guide further in-depth studies on improving the seismic resilience of tall buildings.

• Smart Structures and Systems
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• 제12권3_4호
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• pp.363-379
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• 2013

Dynamic displacement of structures is an important index for in-service structural condition and behavior assessment, but accurate measurement of structural displacement for large-scale civil structures such as long-span bridges still remains as a challenging task. In this paper, a vision-based dynamic displacement measurement system with the use of digital image processing technology is developed, which is featured by its distinctive characteristics in non-contact, long-distance, and high-precision structural displacement measurement. The hardware of this system is mainly composed of a high-resolution industrial CCD (charge-coupled-device) digital camera and an extended-range zoom lens. Through continuously tracing and identifying a target on the structure, the structural displacement is derived through cross-correlation analysis between the predefined pattern and the captured digital images with the aid of a pattern matching algorithm. To validate the developed system, MTS tests of sinusoidal motions under different vibration frequencies and amplitudes and shaking table tests with different excitations (the El-Centro earthquake wave and a sinusoidal motion) are carried out. Additionally, in-situ verification experiments are performed to measure the mid-span vertical displacement of the suspension Tsing Ma Bridge in the operational condition and the cable-stayed Stonecutters Bridge during loading tests. The obtained results show that the developed system exhibits an excellent capability in real-time measurement of structural displacement and can serve as a good complement to the traditional sensors.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2012년도 학술발표회
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• pp.39-39
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• 2012

Data assimilation techniques have received growing attention due to their capability to improve prediction in various areas. Despite of their potentials, applicable software frameworks to probabilistic approaches and data assimilation are still limited because the most of hydrologic modelling software are based on a deterministic approach. In this study, we developed a hydrological modelling framework for sequential data assimilation, namely MPI-OHyMoS. MPI-OHyMoS allows user to develop his/her own element models and to easily build a total simulation system model for hydrological simulations. Unlike process-based modelling framework, this software framework benefits from its object-oriented feature to flexibly represent hydrological processes without any change of the main library. In this software framework, sequential data assimilation based on the particle filters is available for any hydrologic models considering various sources of uncertainty originated from input forcing, parameters and observations. The particle filters are a Bayesian learning process in which the propagation of all uncertainties is carried out by a suitable selection of randomly generated particles without any assumptions about the nature of the distributions. In MPI-OHyMoS, ensemble simulations are parallelized, which can take advantage of high performance computing (HPC) system. We applied this software framework for several catchments in Japan using a distributed hydrologic model. Uncertainty of model parameters and radar rainfall estimates is assessed simultaneously in sequential data assimilation.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2789-2802
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• 2020

Small Modular Reactors (SMRs) are attracting wide attention due to their outstanding performance, extensive studies have been carried out for lead-based fast reactors (LFRs) that cooled with Lead or Lead-bismuth (LBE), and small modular natural circulation LFR is one of the promising candidates for SMRs and LFRs development. One of the challenges for the design small modular natural circulation LFR is to master the natural circulation thermal-hydraulic performance in the reactor primary circuit, while the natural circulation characteristics is a coupled thermal-hydraulic problem of the core thermal power, the primary loop layout and the operating state of secondary cooling system etc. Thus, accurate predicting the natural circulation LFRs thermal-hydraulic features are highly required for conducting reactor operating condition evaluate and Thermal hydraulic design optimization. In this study, a thermal-hydraulic analysis code is developed for small modular natural circulation LFRs, which is based on several mathematical models for natural circulation originally. A small modular natural circulation LBE cooled fast reactor named URANUS developed by Korea is chosen to assess the code's capability. Comparisons are performed to demonstrate the accuracy of the code by the calculation results of MARS, and the key thermal-hydraulic parameters agree fairly well with the MARS ones. As a typical application case, steady-state analyses were conducted to have an assessment of thermal-hydraulic behavior under nominal condition, and several parameters affecting natural circulation were evaluated. What's more, two characteristics parameters that used to analyze natural circulation LFRs natural circulation capacity were established. The analyses show that the core thermal power, thermal center difference and flow resistance is the main factors affecting the reactor natural circulation. Improving the core thermal power, increasing the thermal center difference and decreasing the flow resistance can significantly increase the reactor mass flow rate. Characteristics parameters can be used to quickly evaluate the natural circulation capacity of natural circulation LFR under normal operating conditions.

• Smart Structures and Systems
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• 제30권6호
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• pp.613-626
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• 2022

Guaranteeing the quality and integrity of structural health monitoring (SHM) data is very important for an effective assessment of structural condition. However, sensory system may malfunction due to sensor fault or harsh operational environment, resulting in multiple types of data anomaly existing in the measured data. Efficiently and automatically identifying anomalies from the vast amounts of measured data is significant for assessing the structural conditions and early warning for structural failure in SHM. The major challenges of current automated data anomaly detection methods are the imbalance of dataset categories. In terms of the feature of actual anomalous data, this paper proposes a data anomaly detection method based on data-level and deep learning technique for SHM of civil engineering structures. The proposed method consists of a data balancing phase to prepare a comprehensive training dataset based on data-level technique, and an anomaly detection phase based on a sophisticatedly designed network. The advanced densely connected convolutional network (DenseNet) and Transformer encoder are embedded in the specific network to facilitate extraction of both detail and global features of response data, and to establish the mapping between the highest level of abstractive features and data anomaly class. Numerical studies on a steel frame model are conducted to evaluate the performance and noise immunity of using the proposed network for data anomaly detection. The applicability of the proposed method for data anomaly classification is validated with the measured data of a practical supertall structure. The proposed method presents a remarkable performance on data anomaly detection, which reaches a 95.7% overall accuracy with practical engineering structural monitoring data, which demonstrates the effectiveness of data balancing and the robust classification capability of the proposed network.

• 대한공업교육학회지
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• 제43권1호
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• pp.134-157
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• 2018

이 연구는 지식재산 분야의 실무형 인재를 양성하는 NCS 기반 교육체계를 도입 운영하기 위해서 지식재산교육체제에 대한 만족도와 문제점, 지식재산 NCS(지식재산관리, 지식재산정보조사분석, 지식재산평가 거래)에 대한 교육요구를 조사 분석하였다. 이에 대한 연구의 결론은 다음과 같다. 첫째, 지식재산교육체제에 대한 만족도는 교육내용(M=3.86), 강사(M=3.79), 강의방법 및 환경(M=3.66), 교육평가(M=3.50) 순으로 높게 나타났다. 개선해야 할 문제점은 교육내용에 대해 내용 체계성 미흡과 산업현장 요구를 미반영하여 현업적용도가 낮은 것, 강사는 교육역량과 수강생과의 상호작용이 미흡하며 실무 능력보다 이론 지식을 강조하는 것, 강의 방법은 교육매체 활용성이 낮고 흥미 및 동기부여 방법이 미흡한 것, 평가방법은 이론 지식과 실무 능력의 목표 달성이 부족, 이론 위주로 평가를 실시한다는 것 등이 높게 나타나 이에 대한 개선방안이 마련되어야 한다. 둘째, 지식재산 NCS에 대한 교육요구도는 지식재산평가 거래(요구도 평균=4.33), 지식재산관리(요구도 평균=3.68), 지식재산정보조사분석(요구도 평균=2.99)순으로 높게 나타났으며, 이를 NCS 기반 교육과정을 개편하거나 신규 개발하는 데 반영할 수 있도록 검토해야 한다. 결론적으로 기존 지식재산교육은 보통이상의 만족도를 보였지만 산업현장의 활용성을 높이기 위해 이론보다 실무 능력을 높이는 직무 중심의 교육을 요구하고 있는 것으로 나타났다. 이를 위해서는 산업현장의 요구를 반영한 지식재산 NCS를 도입하여 NCS 기반 교육과정으로 개편하거나 신규 개발이 이루어져야 한다. 또한 공급자가 아닌 수요자 중심의 교수학습방법, 이론 지식이 아닌 수행 및 과정 중심의 평가방법 등의 변화된 교육 패러다임으로 지식재산교육이 개선되어야 한다.

• 한국산업보건학회지
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• 제20권4호
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• pp.282-294
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• 2010

The purpose of SAICM (Strategic Approach to International Chemicals Management) is to minimize the health and environmental hazards from the production and the consumption of chemicals by improving the chemicals management capability of developing countries and implementing a system of the risk assessment and the management based on the precautionary principle until 2020. To achieve this purpose, the UN has prescribed the principles, objectives and establishment of an action plan for the chemicals management strategy which must be carried out at international, local, and national levels, and requested the implementation of the Global Plan of Action (GPA) comprising of 273 recommendations in 36 work areas. SAICM is currently based on voluntary participation, but is expected to become the basic framework of international order in relation to chemicals management in the future. This study aims to analyze the practice in the occupational safety and health area relating to implement 273 recommendations of the GPA, and propose complementary measures for the system in order to provide political advices for establishing future plans to manage industrial chemicals. Twenty three areas of total 36 work areas and 161 items of 273 recommendations have relevance to occupational safety and health areas. We have found that, as a national implementation level, 157 of 161 industrial safety and health items are being implemented at a satisfactory level in regard to the implementation of the GPA, while 4 items, including the ratification of the ILO Conventions 170, 174, 184, and support for GHS (Globally Harmonized System of Classification and Labeling of chemicals) implementation of developing countries, require additional complementary measures for the system and operation.

• 정보교육학회논문지
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• 제12권3호
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• pp.275-282
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• 2008

수학과에서 학습자는 학습을 하기 전에 선수학습을 제대로 이수하지 못했을 경우 다음 학습에 곤란을 겪는다. 학습 부진아에 대한 개별적인 지도는 교육현장에서 반드시 해결해야 할 필연적인 과제이나 일선 학급 담임에게만 그 책임을 지우는 문제를 해결하기 위해 본 연구를 실시하였다. 본 연구에서는 웹기반 진단평가 시스템을 개발 및 적용하여 학습 부진아들의 학습 결손을 여부를 진단 평가 시스템을 통해 진단하고 누적된 학습 결손을 처치하여 본 학습에 도움을 주고자 하였다. 연구대상은 연구자가 근무하는 학교의 수학 기초학습 부진아 10명을 선정하였으며 수와 연산 영역을 중심으로 진단평가 시스템을 적용하였다. 그 결과 학습 부진아의 학력 향상 및 흥미를 높이는데 효과적임을 알 수 있었으며 통계처리는 F-검증(일원분산 분석)을 통해 검증한 결과 유의한 차이가 있음을 통계적으로 검증되었다.

• 한국정밀공학회지
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• 제29권10호
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• pp.1101-1109
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• 2012

Accelerometers play a key role in the structural assessment. However, the current electric type accelerometers have certain limitations to apply some structures such as heavy cabling labor, installed sea structure and sensitivity to electromagnetic fields. An optical Fiber Bragg Grating (FBG) accelerometer has many advantages over conventional electrical sensors since their immunity to electromagnetic interference and their capability to transmit signals over long distance without any additional amplifiers, and there is no corrosion from sea water. In this paper, we have developed a new FBG-based accelerometer. The accelerometer consists of two cantilevered type beams and a mass and two rollers. A bragg grating element is not directly glued to a cantilever to avoid possible non-uniform strain in the element. Instead, the bragg grating element will be attached to rotation part that rolled inducing vertical movement of the mass and support cantilever beams so that the bragg grating element is uniformly tensioned to achieve a constant strain distribution. After manufacturing, we will prove the performance and the natural frequency of the accelerometer through the experiment with a vibration shaker. The FBG-based accelerometer is developed for measuring the vibration not exceeding 50 Hz for the marine and civil structures.

• 자원환경지질
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• 제51권2호
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• pp.131-147
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• 2018

본 연구에서는 중 저준위 방사성 폐기물 표층처분시설의 방사성 핵종 누출에 대한 안전성을 검증하기 위해 덮개층 및 처분고의 구조적 특성 및 물성이 고려된 유체거동 수치모사를 실시하였다. 유체거동 수치모사를 통해 시설 내 침투수거동 양상을 모사한 후, 덮개층 및 처분고 구조물 경계면을 따라 침투수 흐름 선속을 정량적으로 산정함으로써 방사성 핵종 누출의 위험성이 평가되었다. 또한 발생 가능한 시설 설계조건 및 외부 환경 변화가 고려된 다양한 시나리오 기반 수치모사를 실시함으로써 구축된 표층처분시설의 안전여유도 평가 또한 실시되었다. 그 결과, 본 연구에서 이용된 설계 구조가 표층처분시설의 안전적 운영에 적합한 것을 확인하였으며, 다양한 시나리오 기반 다중 수치모사 결과를 통해 덮개층과 처분고 수리특성의 건전성 유지 여부가 시설 안전성에 지대한 영향을 미침을 확인하였다. 특히, 처분고 콘크리트 벽체의 열화상황에서 처분고 내부로의 침투수 흐름을 관찰함으로써 처분고의 차수기능이 처분시설 안전성에 중요한 영향을 미치는 것으로 판단된다.