• 대한기계학회논문집
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• 제19권1호
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• pp.45-60
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• 1995

It is attempted to estimate excitation force of a linear vibratory system using measured vibration responses. The excitation force is estimated from the relationship between the vibration response and system characteristic matrices which are extracted from both the mathematical model of the system and actual response in contrast to the usual approach of inverting the frequency response matrices. This extraction scheme is based on the fact that the vibration response can be expressed in term of linear combination of frequency domain modal vectors defined as mutually orthonormal basis vectors in frequency domain. The extracted frequency domain basis vectors are very stable in computational manipulation. It is found that the estimated excitation force is in good agreement with actually measured force except at the natural frequencies the structure, which is the common feature still to be overcome by the research efforts in this area. From the results of this paper, this disagreement is considered to come from the discrepancy between the model and actual value of the mass, damping and stiffness of the structure.

• Wind and Structures
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• 제2권3호
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• pp.151-171
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• 1999

In its 90 years of life, the Tuned Mass Damper have found application in many fields of engineering as a vibration reducing device. The evolution of the theory of TMDs is briefly outlined in the paper. A generalised mathematical linear model for the analysis of the response of line-like structures with TMDs is presented. The system matrices of the system including the TMDs are written in the state space as a function of the mean wind speed. The stability of the system can be analysed and the Power Spectral Density Function of any response parameter calculated, taking into account an arbitrary number of modes of vibration as well as an arbitrary number of TMDs, for any given PSDF of the excitation. The procedure can be used to optimise the number, position and mechanical properties of the damping devices, with respect to any response parameter. Due to the stationarity of the excitation, the method is well suited to structures subjected to the wind action. In particular the procedure allows the calculation of the onset galloping wind speed and the response to buffeting, and a linearisation of the aeroelastic behaviour allows its use also for the evaluation of the response to vortex shedding. Finally three examples illustrate the suggested procedure.

• Earthquakes and Structures
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• 제16권6호
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• pp.641-654
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• 2019

This paper investigates the seismic response of a typical non-navigable continuous girder bridge isolated with friction sliding bearings of the Hong Kong-Zhuhai-Macao link projects in China. The effectiveness of the friction pendulum system (FPS) and accuracy of the numerical model were evaluated by a 1/20 scaled bridge model using shaking table tests. Based on the hysteretic properties of friction pendulum system (FPS), double concave friction pendulum (DCFP), and triple friction pendulum system (TFPS), seismic response analyses of isolated bridges with the three sliding-type bearings are systematically carried out considering soil-pile interaction under offshore soft clay conditions. The fast nonlinear analysis (FNA) method and response spectrum are employed to investigate the seismic response of isolated offshore bridge structures. The numerical results show that the implementation of the three sliding-type bearings effectively reduce the base shear and bending moment of the reinforced concrete pier, at the cost of increasing the absolute displacement of the bridge superstructure. Furthermore, the TFPS and DCFP bearings show better isolation effect than FPS bearing for the example continuous girder bridge.

• Nuclear Engineering and Technology
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• 제51권2호
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• pp.600-606
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• 2019

Studies on the application of the lead rubber bearing (LRB) isolation system to nuclear power plants are being carried out as one of the measures to improve seismic performance. Nuclear power plants with isolation systems require seismic probabilistic safety assessments, for which the seismic fragility of the structures, systems, and components needs be calculated, including for beyond design basis earthquakes. To this end, seismic response analyses are required, where it can be seen that the behaviors of the isolation system components govern the overall seismic response of an isolated plant. The numerical model of the LRB used in these seismic response analyses plays an important role, but in most cases, the extreme performance of the LRB has not been well studied. The current work therefore develops an extreme nonlinear numerical model that can express the seismic response of the LRB for beyond design basis earthquakes. A full-scale LRB was fabricated and dynamically tested with various input conditions, and test results confirmed that the developed numerical model better represents the behavior of the LRB over previous models. Subsequent seismic response analyses of isolated nuclear power plants using the model developed here are expected to provide more accurate results for seismic probabilistic safety assessments.

• Structural Engineering and Mechanics
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• 제83권3호
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• pp.401-413
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• 2022

The collapse of civil infrastructure due to natural disasters results in financial losses and many casualties. In particular, the recent increase in earthquake activities has highlighted on the importance of assessing the seismic performance and predicting the seismic risk of a structure. However, the nonlinear behavior of a structure and the uncertainty in ground motion complicate the accurate seismic response prediction of a structure. Artificial intelligence can overcome these limitations to reasonably predict the nonlinear behavior of structures. In this study, a deep learning-based algorithm was developed to estimate the time-history seismic response of bridge structures. The proposed deep neural network was trained using structural and ground motion parameters. The performance of the seismic response prediction algorithm showed the similar phase and magnitude to those of the time-history analysis in a single-degree-of-freedom system that exhibits nonlinear behavior as a main structural element. Then, the proposed algorithm was expanded to predict the seismic response and fragility prediction of a bridge system. The proposed deep neural network reasonably predicted the nonlinear seismic behavior of piers and bearings for approximately 93% and 87% of the test dataset, respectively. The results of the study also demonstrated that the proposed algorithm can be utilized to assess the seismic fragility of bridge components and system.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2728-2745
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• 2021

The purpose of this study is to reduce seismic responses of an actual nuclear piping system using a tuned mass damper (TMD) device. A numerical piping model was developed and validated based on shaking table test results with actual nuclear piping. A TMD for nuclear piping was newly devised in this work. A TMD shape design suitable for nuclear piping systems was conducted, and its operating performance was verified after manufacturing. The response reduction performance of the developed TMD under earthquake loading on actual piping was investigated. Results confirmed that, on average, seismic response reduction rates of 34% in the maximum acceleration response, 41% in the root mean square acceleration response, and 57% in the spectral acceleration response were shown through the TMD application. This developed TMD operated successfully within the seismic response reduction rate of existing TMD optimum design values. Therefore, the developed TMD and dynamic interpretation help improve the nuclear piping's seismic performance.

• Structural Engineering and Mechanics
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• 제87권2호
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• pp.173-189
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• 2023

For a given structural geometry, the stiffness and damping parameters of the soil and the dynamic response of the structure may change in the face of an equivalent linear soil behavior caused by a strong earthquake. Therefore, the influence of equivalent linear soil behavior on the impedance functions form and the seismic response of the soil-structure system has been investigated. Through the substructure method, the seismic response of the selected structure was obtained by an analytical formulation based on the dynamic equilibrium of the soil-structure system modeled by an analog model with three degrees of freedom. Also, the dynamic response of the soil-structure system for a nonlinear soil behavior and for the two types of impedance function forms was also analyzed by 2D finite element modeling using ABAQUS software. The numerical results were compared with those of the analytical solution. After the investigation, the effect of soil nonlinearity clearly showed the critical role of soil stiffness loss under strong shaking, which is more complex than the linear elastic soil behavior, where the energy dissipation depends on the seismic motion amplitude and its frequency, the impedance function types, the shear modulus reduction and the damping increase. Excellent agreement between finite element analysis and analytical results has been obtained due to the reasonable representation of the model.

• 풍력에너지저널
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• 제15권1호
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• pp.43-49
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• 2024

This study performed a response analysis according to the transmission error of the yaw drive. To perform the response analysis, the excitation source of the transmission error was modeled and the outer ring of the first stage bearing and the outer ring of the output shaft bearing were used as measurement positions. The response results were analyzed based on the vibration tolerance values of AGMA 6000-B96. As a result of the response of the first stage bearing outer ring, the maximum displacement of the first stage planetary gear system was 5.59 and the maximum displacement of the second to fourth stage planetary gear systems was 4.21 ㎛ , 3.13 ㎛ , and 25.6 ㎛ . In the case of the output shaft bearing outer ring, the maximum displacement of the first stage planetary gear system was 1.73 ㎛, and the maximum displacement of the second to fourth stage planetary gear system was 1.94 ㎛, 0.73 ㎛, and 2.03 ㎛. According to AGMA 6000-B96, the vibration tolerance of first stage is 17.5 ㎛, and the vibration tolerance of the second to fourth stages is 58 ㎛, 80 ㎛, and 375 ㎛, which shows that the vibration tolerance is satisfied and it is safe.

• 한국지리정보학회지
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• 제19권1호
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• pp.180-196
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• 2016

재난의 피해를 최소화하기 위하여 예방, 대비, 대응 등의 다양한 측면에서 관리 하고 있다. 예방과 대비가 잘 되어있더라도, 자연재해와 같은 불가항력의 재난에 대해서는 예상과는 다른 피해가 생길 수도 있다. 따라서 통합적 재난 관리를 위해서 신속한 재난 관리 및 예측을 기반으로 동일한 재난정보 공유가 가능한 시스템을 구축 개발하여야 한다. 특히, 신속한 재난 대응을 위해서는 유관기관 및 현장공무원과 같은 직접적인 방재 투입 인력 간의 동일한 정보공유가 필요하다. 최근에 활용되는 재난 관리 시스템의 경우 고용량의 지리정보를 사용하거나, 정확한 재난 예측을 위해 다양한 인자들을 활용하여 구축된다. 그뿐만 아니라, 최근 구축 및 연구되고 있는 3D GIS를 활용할 경우 하드웨어 등의 문제로 인해 시스템을 사용하지 못하는 경우도 발생한다. 따라서 예측 시뮬레이션을 하여 대응 정보를 확보한다고 해도, 상황에 따라 시스템을 활용 불가한 경우 혹은 해당 정보의 확장자를 읽을 수 없는 환경일 경우에 본질적으로 공통된 정보를 공유하기는 힘들다. 따라서 본 연구에서는 재난 대응을 위한 시스템을 구축하고, 그를 기반으로 공유된 정보가 공통된 정보에 준할 수 있도록 신속하고 정확한 정보를 제공하는 체계를 구축하고자 한다. 이를 통해 기존 재해 대응 시간을 앞당기고, 신속한 대응을 통해 의사결정을 지원하여 인적 물적 피해를 최소화할 수 있다.

• 한국엔터테인먼트산업학회논문지
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• 제15권4호
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• pp.255-265
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• 2021

본 연구는 성인간호학I 전공이론 교과목 위장관계 대상자 간호중재 주제에 카훗(Kahoot!)을 활용하여 총 6회의 수업을 적용한 후 간호대학생의 학습몰입, 비판적 사고 성향, 문제해결능력에 미치는 효과를 확인하였고, 카훗(Kahoot!) 수업 적용 후 수업만족도에 영향을 미칠 수 있는 요인을 파악함으로써 효과적인 간호교육을 위한 교수학습법 개발의 기초자료를 제공하고자 시도되었다. 본 연구는 단일군 전·후설계 실험연구로서 G광역시 일개 D대학 간호학과 2학년 학생 176명을 연구대상으로 하였다. 본 연구결과 학습몰입 정도는 카훗(Kahoot!) 수업 적용 전 평균 2.75점에서 수업 적용 후 평균 2.95점으로 증가하였고, 통계적으로 유의한 차이가 있었다(t=-6.257, p=.000). 비판적 사고 성향 정도는 카훗(Kahoot!) 수업 적용 전 평균 3.39점에서 수업 적용 후 평균 3.43점으로 증가하였고, 통계적으로 유의한 차이가 있었다(t=-2.163, p=.032). 문제해결 능력 정도는 카훗(Kahoot!) 수업 적용 전 3.34점에서 수업 적용 후 3.42점으로 증가하였고, 통계적으로 유의한 차이가 있었다(t=-3.032, p=.003). 카훗(Kahoot!) 수업 적용 후 간호대학생의 학습몰입, 비판적 사고 성향, 문제해결능력, 수업만족도는 각각 정적 상관관계가 있었고, 카훗(Kahoot!) 수업만족도에 영향을 미치는 요인은 학습몰입(β=.307, p=.000), 문제해결능력(β=.158, p=.041) 순이었으며, 이러한 변수는 대상자의 수업만족도 요인을 15.2% 설명하였다(F=16.905, p=.000). 따라서 본 연구결과를 바탕으로 카훗(Kahoot!)을 활용한 수업은 간호교육의 효과적인 교수학습법임을 확인하였고, 추후 연구에서는 다양한 교과목과 주제에 카훗(Kahoot!) 교수학습법을 적용하고 수업 효과를 검증하는 반복연구를 제언한다.