• Structural Engineering and Mechanics
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• 제21권5호
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• pp.507-518
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• 2005

In the shear-lag analysis of structures deterministic procedure is insufficient to provide complete information. Probabilistic analysis is a holistic approach for analyzing shear-lag effects considering uncertainties in structural parameters. This paper proposes an efficient and accurate algorithm to analyze shear-lag effects of structures with parameter uncertainties. The proposed algorithm integrated the advantages of the response surface method (RSM), finite element method (FEM) and Monte Carlo simulation (MCS). Uncertainties in the structural parameters can be taken into account in this algorithm. The algorithm is verified using independently generated finite element data. The proposed algorithm is then used to analyze the shear-lag effects of a simply supported beam with parameter uncertainties. The results show that the proposed algorithm based on the central composite design is the most promising one in view of its accuracy and efficiency. Finally, a parametric study was conducted to investigate the effect of each of the random variables on the statistical moment of structural stress response.

• Geomechanics and Engineering
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• 제36권1호
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• pp.83-97
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• 2024

It is important to make reasonable prediction about the long-term deformation of high rockfill geostructures. However, the deformation is usually underestimated using the rockfill parameters obtained from laboratory tests due to different size effects, which make it necessary to identify parameters from in-situ monitoring data. This paper proposes a novel hybrid back-analysis method with a modified objective function defined for the time-dependent back-analysis problem. The method consists of two stages. In the first stage, an improved weighted average method is proposed to quickly narrow the search region; while in the second stage, an adaptive response surface method is proposed to iteratively search for the satisfactory solution, with a technique that can adaptively consider the translation, contraction or expansion of the exploration region. The accuracy and computational efficiency of the proposed hybrid back-analysis method is demonstrated by back-analyzing the long-term deformation of two high embankments constructed for airport runways, with the rockfills being modeled by a rheological model considering the influence of stress states on the creep behavior.

• 제어로봇시스템학회논문지
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• 제17권3호
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• pp.241-247
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• 2011

This paper is intended to improve efficiency of two-phase BLDC motor using analytical and statistical methods, and then the stability of the starting for the designed model is investigated. The characteristics of the motor according to magnetization directions of permanent magnet are analyzed through the analytical method, and design variables that affect the efficiency are selected. Preliminary optimal design is performed using the analytical method with the design variable. The RSM (Response Surface Method) based on the FEA (Finite Element Analysis) is applied to complement errors of the analytical method. As a result, the optimal design is determined. Finally, the stability of the starting for the optimal designed model is evaluated by analyzing cogging torque, and it is verified through the FEA.

• Nuclear Engineering and Technology
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• 제18권1호
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• pp.38-47
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• 1986

경수로심의 열 여유도를 분석하기 위하여 반응표면 및 Monte Carlo 방법을 이용하는 통계적 분석 방법이 제시되었다. 통계적인 열 여유도 분석 방법은 입력변수들의 불확실도를 확률론적으로 처리함으로써 열 여유도의 최적 평가를 수행한다. 이 방법은 원자력 1호기 정상상태의 원자로심 분석에 응용되었으며 또한 종래의 결정론적 방법 및 웨스팅하우스의 개선된 열설계 방법과도 비교되었다. 본 연구를 통하여 반응표면 분석 방법은 통계적인 열 여유도 분석에 유용함을 알 수 있었으며, 이 방법을 통한 열 여유도의 증가도 확인되었다.

• 한국해양공학회지
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• 제11권2호
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• pp.91-99
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• 1997

This paper presents theoretical formulations and numerical computations for predicting first-and second-order hydrodynamic force on a ship advvancing in waves. The theoretical formulation leads to linearized radiation and diffration problems solving the three-dimensional Green function integral equations over the mean wetted body surface. Green function representing a translating and pulsating source potantial for infinite water depth is used. In order to solve integral equations for three dimentional flows using Green function efficiently, the Hoff's method is adopted for numerical calculation of the Green function. Based on the first-order solution, the mean seconder-order forces and moments are obtained by directly integrating second-order pressure over the mean wetted body surface. The calculated items are carried out for analyzing the seakeeping characteristics of Series 60. The calculated items are hydrodynamic coefficients, wave exciting forces, frequency response functions and addd resistance in waves.

• 한국지반공학회지:지반
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• 제3권3호
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• pp.31-48
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• 1987

지중에 매설된 관에는 관위의 흙무게나 지표면상재하중으로 인하여 연직견력이 작용하며, 지진이나 불등침하등으로 인하여 상향하중이 작용하는 경우도 있다. 본 연구에서는 Marston-Spangler이론을 새로운 방법으로 분석하여 관위의 흙무게로 인해 매설권에 작용하는 압력에 관하여 검토하였고, 매설연성관에 대한 재하실험을 실시하여 지표면상재하중으 로 인한 매설관의 거동특성을 연구하였다. 또 매설관의 인발저항(uplifting resistance)이론의 검토와 상향인발실험을 통하여 최대인발저항을 구하는 방법 등을 연구하였다.

• 한국자동차공학회논문집
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• 제21권5호
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• pp.130-135
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• 2013

Until now, passenger airbag design is based on the referred car design and many repetitive crash tests have been done to meet the crash performance. In this paper, it was suggested a new design process of passenger airbag. First, key performance factors were determined by analyzing the injury risk effectiveness of each performance factor. And it was made a relationship between injury risk and performance factor by using the response surface model. By using this one, it can be predicted the injury risk of head and neck. Predicted injury risk of optimal design was obtained through this injury risk prediction model and it was verified by FE analysis result within 18% error of head and 9% error of neck. It was shown that a target crash performance can be met by controlling the key performance factors only.

• 대한기계학회논문집A
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• 제32권8호
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• pp.654-659
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• 2008

This paper is to suggest a concept design of the permanent magnet type magnetic resonance imaging (MRI) device based on the parameter optimization method. Pulse currents in the gradient coils will introduce the effect of eddy currents in the ferromagnetic material, which will worsen the quality of imaging. In order to equalize the magnetic flux in the MRI device for good imaging, the eddy current effect in the ferromagnetic material must be taken into account. This study attempts to use the design of experiment (DOE) and the response surface method (RSM) for equalizing the magnetic flux of the permanent magnet type MRI device using that the magnetic flux can be calculated directly using a commercial finite element analysis package. As a result, optimal shapes of the pole and the yoke of the PM type MRI device can be obtained. The commercial package, ANSYS, is used for analyzing the magnetic field problem and obtaining the resultant magnetic flux.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1793-1799
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• 2003

An optimal design of a multi-layered plate structure to endure high-velocity impact has been suggested by using size optimization after numerical simulations. The NET2D, a Lagrangian explicit time-integration finite element code for analyzing high-velocity impact, was used to find the parameters for the optimization. Three different materials such as mild steel, aluminum for a multi-layered plate structure and die steel for the pellet, were assumed. In order to consider the effects of strain rate hardening, strain hardening and thermal softening, Johnson-Cook model and Phenomenological Material Model were used as constitutive models for the simulation. It was carried out with several different gaps and thickness of layers to figure out the trend in terms of those parameters' changes under the constraint, which is against complete penetration. Also, the measuring domain has been shrunk with several elements to reduce the analyzing time. The response surface method based on the design of experiments was used as optimization algorithms. The optimized thickness of each layer in which perforation does not occur has been obtained at a constant velocity and a designated total thickness. The result is quite acceptable satisfying both the minimized deformation energy and the weight criteria. Furthermore, a conceptual idea for topology optimization was suggested for the future work.

• 전자공학회논문지
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• 제53권2호
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• pp.62-69
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• 2016

본 논문에서는 대화력전의 목표달성에 대한 평가척도를 선정하고 평가척도의 최적값을 만족하는 청군의 타격자원의 합리적인 조합과 목표달성시간의 회귀식을 도출하고자 하였다. 또한 현실세계에서 회귀식을 도출하는 일련의 과정을 연구방법론적 관점에서 제시하고자 하였다. 이를 위해 현재 북한과 대한민국이 보유하고 있는 무기체계들의 정보를 이용하여 대화력전을 단순화한 시뮬레이션을 만들어 목표달성시간을 도출하였다. 시뮬레이션에서는 대화력전을 탐지, 결정, 타격의 세 단계로 나누었다. 탐지에는 난수를 활용한 확률을 적용했고 결정과 타격은 고정된 상수를 적용시켰다. 고정된 적에 대해서 목표달성시간을 도출하였으며 목표달성시간이 최단시간으로 나오는 것이 시뮬레이션의 최적값이라고 판단했다. 시뮬레이션의 목표달성시간을 바탕으로 미니탭의 반응표면분석법을 이용하여 고정된 홍군에 대한 청군 무기체계의 최적조합 및 회귀식을 도출하였다. 도출된 회귀식은 2-표본 t검정을 이용하여 검증하였다.