• Geomechanics and Engineering
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• 제4권3호
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• pp.173-190
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• 2012

With recent growing interests in the Performance-Based Seismic Design and Assessment Methodology, more realistic modeling of a structural system is deemed essential in analyzing, designing, and evaluating both newly constructed and existing buildings under seismic events. Consequently, a shallow foundation element becomes an essential constituent in the implementation of this seismic design and assessment methodology. In this paper, a contact interface fiber section element is presented for use in modeling soil-shallow foundation systems. The assumption of a rigid footing on a Winkler-based soil rests simply on the Euler-Bernoulli's hypothesis on sectional kinematics. Fiber section discretization is employed to represent the contact interface sectional response. The hyperbolic function provides an adequate means of representing the stress-deformation behavior of each soil fiber. The element is simple but efficient in representing salient features of the soil-shallow foundation system (sliding, settling, and rocking). Two experimental results from centrifuge-scale and full-scale cyclic loading tests on shallow foundations are used to illustrate the model characteristics and verify the accuracy of the model. Based on this comprehensive model validation, it is observed that the model performs quite satisfactorily. It resembles reasonably well the experimental results in terms of moment, shear, settlement, and rotation demands. The hysteretic behavior of moment-rotation responses and the rotation-settlement feature are also captured well by the model.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2018년도 추계학술대회
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• pp.241-247
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• 2018

Deep-sea fishing vessel No. 501 Oryong was fully flooded through its openings and sunk to the bottom of the sea due to the very rough sea weather on the way of evasion after a fishing operation in the Bearing Sea. As a result, many crew members died and/or were missing. In this study, a full-scale ship flooding and sinking simulation was conducted, and the sinking process was analyzed for the precise and scientific investigation of the sinking accident using a highly advanced Modeling & Simulation (M&S) system of the Fluid-Structure Interaction (FSI) analysis technique. To objectively secure the weather and sea states during the sinking accident in the Bering Sea, time-based wind and wave simulation at the region of the sinking accident was conducted and analyzed, and the weather and sea states were realized by simulating the irregular strong wave and wind spectrums. Simulation scenarios were developed and full-scale ship and fluid (air & seawater) modeling was performed for the flooding sinking simulation, by investigating the hull form, structural arrangement & weight distribution, and exterior inflow openings and interior flooding paths through its drawings, and by estimating the main tank capacities and their loading status. It was confirmed that the flooding and sinking accident was slightly different from a general capsize and sinking accident according to the simple loss of stability.

• 소음진동
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• 제8권3호
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• pp.494-503
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• 1998

In this paper, in order to analyze dynamic characteristics of an automobile steering system consisting of many components, natural frequencies and transfer functions of each component and the total system are found on a FFT analyzer by experiments. Then, the data are transmitted to a commercial package program, CADA-PC. By analyzing the data, the mode shape of each natural frequency and damping values are obtained. Also, the function of a rubber coupling in column and telescoping effects on system are considered. C.A.E commercial programs are used to compare with the results of experiments. For the finite element modeling, I-DEAS is used. Data processing and post processing are operated on NASTRAN and XL, respectively. The ball-bearing and the linkage of shaft with column are modeled by spring element. Stiffness is modified from the results of experiments. The results of those show close agreement. In the mode shape of total system, wheel mode is dominant at lower frequency, while the column mode is main mode at higher. The role of rubber coupling in vibration isolation is clear on mode shape. Telescoping function makes natural frequency of column changed.

• Geomechanics and Engineering
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• 제14권1호
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• pp.43-50
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• 2018

Applicability of constructing piled raft foundations on soft clay has been given attention in recent years. Lack of sufficient stiffness for soil and thus excessive settlements to allow higher contribution of piles is the major concern in this regard. This paper presents a numerical investigation of performance of piled-raft foundations on soft clay with focusing on a case study. A 3D FEM numerical model is developed using ABAQUS. The model was calibrated by comparing physical and numerical modeling results of other researchers. Then the possibility of using piled-raft system in construction of foundation for a water storage tank in Sarbandar, Iran is assessed. Soil strength parameters in the numerical model were calibrated using the instrumentation data of a heavily instrumented preloading project at the construction site. The results indicate that choosing the proper combination of length and spacing for piles can lead to acceptable differential and total settlements while a high percentage of total bearing capacity of piles can be mobilized, which is an efficient solution for the project. Overall, the construction of piled-rafts on soft clays is promising as long as the total settlement of the structure is not imposing restrictions such as the common 25 mm allowable settlement. But instead, if higher allowable settlements are adopted, for example in the case of rigid steel tanks, the method shall be applicable with considerable cost savings.

• Tribology and Lubricants
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• 제30권2호
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• pp.116-123
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• 2014

The objective of this study is to model and simulate the nonlinear lubrication performance of the sliding part between the piston and cylinder wall in a hydrostatic swash-plate-type axial piston pump. A numerical algorithm is developed that facilitates simultaneous calculation of the rotating body motion and fluid film pressure to observe the fluid film geometry and power loss. It is assumed that solid asperity contact, so-called mixed lubrication in this study, invariably occurs in the swash-plate-type axial piston pump, which produces a higher lateral moment on the pistons than other types of hydrostatic machines. Two comparative mixed lubrication models, rigid and elastic, are used to determine the reaction force and sliding friction. The rigid model does not allow any elastic deformation in the partial lubrication area. The patch shapes, reactive forces, and virtual local elastic deformation in the partial lubrication area are obtained in the elastic contact model using a simple Hertz contact theory. The calculation results show that a higher reaction force and friction loss are obtained in the rigid model, indicating that solid deformation is a significant factor on the lubrication characteristics of the reciprocating piston part.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.336-342
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• 1997

In this paper, in order to analyze dynamic characteristics of automobile steering system consisting of many components, natural frequencies and transfer functions of each component and total system are found on FFT by experiments. Then, the data are transmitted to commercial package program, CADA-PC. By analyzing the data, the mode shape of each natural frequency and damping values are obtained. Also, the function of rubber coupling in column and telescoping effects on system are considered. C.A.E commercial program are used to compare with the results of experiments. For finite element modeling, I-DEAS is used. Data processing and post processing are operated on NASTRAN and XL, respectively. The ball-bearing and the linkage of shaft with column are modeled by spring elements. Stiffness is modified from the results of experiments. The results of those show close agreement. In the mode shape of total system, wheel mode is dominant at lower frequency while the column mode is main mode at higher . The role of rubber coupling in vibration isolation is clear on mode shape. Telescoping function makes natural frequency of column changed.

• 한국철도학회논문집
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• 제16권4호
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• pp.286-297
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• 2013

본 연구에서는 PSC-I 거더 교량을 대상으로, 3차원 교량 모델로 이동하중해석에 의한 엄밀한 동적 안정성 해석을 수행할 때의 모델링 방법과 해석방법에 대한 영향 평가를 수행하였다. 이를 위해 콘크리트 및 자갈궤도 등을 채용할 때의 합리적인 모델링 방법론과 물성치를 제시하였다. 또한, 궤도 모델링 유무, 궤도 종류, 거더 중심에서 받침까지의 거리 고려 여부, 직접적분법과 모달해석법 등 이동하중해석법, 필터링 등이 응답에 미치는 영향을 분석하였다.

• 한국시뮬레이션학회논문지
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• 제26권3호
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• pp.65-72
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• 2017

함정 전투실험의 사후분석에서는 객체에 대한 자함의 표적 탐지능력와 무장 교전능력을 분석한다. 따라서 사후분석을 위해서는 전장 환경의 위협 객체와 센서에서 탐지한 표적간 연관 맺을 수 있는 정보가 필요하다. 기존의 공학급 교전 시뮬레이터는 이러한 객체-표적 연관정보를 제공하였다. 그러나 사용된 시뮬레이터의 잠수함모델에는 실제 소나시스템의 신호처리 알고리즘이 탑재되어있다. 소나신호처리 과정을 통해 얻은 표적정보에서는 실제 객체정보가 무엇인지 연관지을 수 없으며, 사용된 시뮬레이터도 그러한 정보를 제공하지 않고 있다. 따라서 본 연구에서는 객체정보와 소나신호처리에서 얻은 표적의 방위각, 거리, 속도 등의 기동정보를 이용하여 객체-표적 연관정보를 생성하였다. 객체-표적 연관정보를 생성하는 방법을 제안하고, 제안한 방법의 타당성을 실험을 통해 검증하였다.

• Smart Structures and Systems
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• 제6권4호
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• pp.389-403
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• 2010

By using image recognition technology, this paper presents a new fault diagnosis method for rotating machinery with artificial immune algorithm. This method focuses on the vibration state parameter image. The main contribution of this paper is as follows: firstly, 3-D spectrum is created with raw vibrating signals. Secondly, feature information in the state parameter image of rotating machinery is extracted by using Wavelet Packet transformation. Finally, artificial immune algorithm is adopted to diagnose rotating machinery fault. On the modeling of 600MW turbine experimental bench, rotor's normal rate, fault of unbalance, misalignment and bearing pedestal looseness are being examined. It's demonstrated from the diagnosis example of rotating machinery that the proposed method can improve the accuracy rate and diagnosis system robust quality effectively.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1328-1333
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• 2006

For fault diagnosis of machines and equipments, knowledge-based method has been used widely but has some limitations for complex systems. These can be covered by model-based method. As one kind of model-based method, Qualitative modeling diagnosis method is developed in this research. The developed method uses output signal only. In this method quantization of the output signal mattes automata which can characterize the flow of the signal pattern to normal and fault respectively. As an example of the qualitative diagnosis method, an electric tool which has faults at gear and bearing were examined in this research. The result shows that the developed method can diagnose the fault clearly for the two fault cases.