• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.146-153
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• 2007

Weight reduction for automobile components has been sought to achieve fuel efficiency and energy conservation. There are two approaches in reducing their weights. One is by using material lighter than steel, and the other is by redesigning their structures. The latter has been performed by adopting hydroforming, tailor weled blank, optimization, etc. In this research, the kriging approximation method and simulated annealing algorithm are applied to the design of a front door made by TWB (Tailor Welded Blank) technology. The design variables are set up as the thicknesses of parts and the positions of parting lines. A thickness set considered as a design variable of each part is not arbitrarily determined but selected from standard products, so it is a discrete set. This research presents the discrete and continuous structural optimization method for an automotive door design.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.119-126
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• 2006

Kriging model is widely used as design DACE(analysis and computer experiments) model in the field of engineering design to accomplish computationally feasible design optimization. In this paper, the optimization of gate valve was performed using Kriging based approximation model. The DACE modeling, known as the one of Kriging interpolation, is introduced to obtain the surrogate approximation model of the function. In addition, we describe the definition, the prediction function and the algorithm of Kriging method and examine the accuracy of Kriging by using validation method.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.188-188
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• 2015

최근 기후변화와 지구온난화로 인한 돌발성 집중호우 및 홍수, 태풍의 빈도 증가는 사회 경제적으로 막대한 피해를 입히고 있다. 수자원 분야에서는 이러한 피해를 예방하고 빠른 대처를 위해 강우의 정밀한 관측뿐만 아니라 강우의 정확한 공간 분포 파악이 요구되고 있다. 그러나 일반적으로 강우의 측정 시 사용되는 지상우량계의 경우 공간적인 밀도가 낮고, 불규칙적으로 위치하고 있어 강우의 시 공간적 변화를 반영하기 어려운 한계가 있다. 이러한 문제를 보완하고자 지상강우자료와 레이더자료를 결합하여 사용하고 있다. 본 연구는 지상강우자료의 양적인 특성을 고려함과 동시에 레이더자료의 공간분포특성을 반영하는 강우장을 추정하고자 하였다. 따라서 지구통계학적 공간보간기법인 크리깅 기법을 적용하였으며, OK(Ordinary Kriging), KED(Kriging with External Drift), ColCOK(Collocated Cokriging) 기법에 의해 생성된 강우장을 비교하였다. 지상강우와의 양적인 측면을 비교하기 위해 관측소 위치에서의 실제 강우값과 추정된 강우값의 상관관계를 비교하였으며, 레이더자료의 공간분포특성과의 유사성을 확인하기 위해 각 기법에서의 베리오그램을 비교하였다.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.06b
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• pp.141-152
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• 2003

터널 설계를 위한 조사 있어서, 요사이 시추공 조사는 물론 탄성파 탐사, 전기 비저항 탐사 등의 물리탐사가 빈번히 행해지고 있는 실정이다. 따라서 최적의 지반평가(암반 등급 등)를 위해 조사에서 얻어지는 모든 자료를 체계적으로 최대한 활용할 수 있는 방법이 절실히 요구되고 있다. 많은 연구자들이 정량적 데이터가 부족한 경우에 대처하기 위해 정상적 데이터의 이용을 적극 제안해 왔다. 본 연구에서는 신뢰도가 다른 두 종류의 자료, 즉 시추공자료와 물리탐사 자료를 활용하여 시추가 되지 않은 구간의 암반등급을 추정하는 방법을 지구통계학적 이론에 근거하여 소개하고자 한다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.6
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• pp.391-398
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• 2023

In this paper, a penalized maximum likelihood estimation (PMLE) method that applies a penalty to increase the accuracy of a basis-screening-based Kriging model (BSKM) is introduced. The maximum order and set of basis functions used in the BSKM are determined according to their importance. In this regard, the cross-validation error (CVE) for the basis functions is employed as an indicator of importance. When constructing the Kriging model (KM), the maximum order of basis functions is determined, the importance of each basis function is evaluated according to the corresponding maximum order, and finally the optimal set of basis functions is determined. This optimal set is created by adding basis functions one by one in order of importance until the CVE of the KM is minimized. In this process, the KM must be generated repeatedly. Simultaneously, hyper-parameters representing correlations between datasets must be calculated through the maximum likelihood evaluation method. Given that the optimal set of basis functions depends on such hyper-parameters, it has a significant impact on the accuracy of the KM. The PMLE method is applied to accurately calculate hyper-parameters. It was confirmed that the accuracy of a BSKM can be improved by applying it to Branin-Hoo problem.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.255-256
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• 2006

• Journal of the Korean earth science society
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• v.26 no.5
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• pp.429-435
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• 2005

3D RMR (Rock Mass Rating) analysis has been performed by applying the Geostatistical integration technique for geophysical and borehole data. Of the various geostatistical techniques for the integrated data analysis, in this study, we applied the SKlvm (Simple Kriging with local varying means) method that substitutes the values of the interpreted geophysical result with the mean values of the RMR at the location to be inferred. The substitution is performed by the indicator transform between the result of geophysical interpretation and the observed RMR values at borehole sites. The used geophysical data are the electrical resistivity and MT result, and 10 borehole sites are investigated to obtain the RMR values. This integrated analysis makes the interpretation to be more practical for identifying the realistic RMR distribution that supports the regional geological situation.

• Journal of the Korean Association of Geographic Information Studies
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• v.11 no.4
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• pp.64-75
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• 2008

Since the current database systems for managing geotechnical investigation results were limited by being described boring test result in point feature, it has been trouble for using other GIS data. Although there are some studies for spatial characteristics of subsurface modeling, it is rather lack of being interoperable with GIS, considering geotechnical engineering facts. This is reason for difficulty of practical uses. In this study, we has developed subsurface spatial information model through extracting needed geotechnical engineering data from geotechnical information DB. The developed geotechnical information clustering program(GEOCL) has made a cluster of boring formation(and formation ratio), classification of layer, and strength characteristics of subsurface. The interpolation of boring data has been achieved through zonal kriging method in the consideration of spatial distribution of created cluster. Finally, we make a subsurface spatial information model to integrate with digital elevation model, and visualize 3-dimensional model by subsurface spatial information viewing program(SSIVIEW). We expect to strengthen application capacity of developed model in subsurface interpretation and foundation design of construction works.

• Tunnel and Underground Space
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• v.13 no.2
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• pp.87-99
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• 2003

Geostatistics is defined as the theory of modeling of regionalized variables and is an efficient and elegant methodology for estimation and uncertainty evaluation from limited spatial sample data. In this study, we have made a theoretical comparison between kriging estimation and geostatistical simulation methods. Kriging methods do not preserve the histogram of original data nor their spatial structure, and also provide only an incomplete measure of uncertainty when compared to the simulation methods. A practical procedure of geostatistical simulation is suggested in this study and the technique is demonstrated through an application, in which it was used to identify the spatial distribution of RMR as well as to evaluate the spatial uncertainty. It is concluded that the geostatistical simulation is the appropriate method to quantify the spatial uncertainty of geotechnical variables such as RMA. Therefore, the results from the simulation can be used as useful information for designer's considerations in decision-making under various geological conditions as well as the related terms of contract.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.2
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• pp.32-38
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• 2005

In this research, a procedure to improve the feasibility of design space is proposed by an approximation model. The Chebyshev Inequality is used as the criterion of modification of design space. This procedure is applied to the aero-elastic transonic wing design problem and the feasibility of the design space is greatly improved. Also the optimization results are improved by appling this procedure. That is, the probability to satisfy all imposed constraints is increased and the better design points are included in design space after this procedure. And the use of both a second-order response surface model and the Kriging model is investigated and compared in accuracy, efficiency, and robustness as approximation models in this procedure for different sampling methods. As a result, the second-order response surface model is more appropriate for our application than the Kriging model, because it is linear enough to be fitted well by the response surface model.