• Composites Research
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• 제12권4호
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• pp.42-54
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• 1999

섬유-금속 적층 복합재료(FMLC)는 섬유와 금속 박판으로 구성된 새로운 형태의 구조재로 가볍고 우수한 피로 특성을 가지며 금속과 같이 가소성과 충격저항성이 우수하고, 가공성이 뛰어나다. 본 연구에서는 여러 하중 조건하에 있는 섬유-금속 적층 복합재료를 유전자 알고리듬을 이용하여 최적 설계하였다. 전단변형이론에 근거한 유한요소법을 사용하여 적층판을 해석하였으며, 설계변수로 금속판의 강도와 섬유 층의 수에 따른 적층각도를 두었다. 섬유층과 금속판의 적합도 함수로는 각각 Tasi-Hill failure criterion과 Miser yield criterion을 사용하였다. 유전자 알고리듬의 연산자로는 토너먼트 선택과 균일 교배를 사용하였다. 효율적인 진화를 위해 엘리티스트 모델을 사용하며, 높은 정확도를 가진 해를 얻기 위해 크리프 무작위 탐색(creeping random search) 방법을 통해 더 우수한 자손을 얻었다. 여러 가지 하중 조건에 대하여 최적설계 결과를 나타내었으며, 파괴 지수 측면에서 탄소섬유강화복합재료(CFRP)와 비교하였다. 해석 결과 섬유-금속 적층 복합재료는 탄소섬유강화복합재료에 비하여 집중하중이나 분포하중 형태에 대하여 우수한 특성을 보였으며, 파괴 지수의 편차가 적어 예기치 않은 하중에 잘 견딜 것으로 사료된다.

• Geomechanics and Engineering
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• 제36권4호
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• pp.355-366
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• 2024

The original elastoplastic Hardening Soil model is formulated actually partly under hexagonal pyramidal Mohr-Coulomb failure criterion, and can be only used in specific stress paths. It must be completely generalized under Mohr-Coulomb criterion before its usage in engineering practice. A set of generalized constitutive equations under this criterion, including shear and volumetric yield surfaces and hardening laws, is proposed for Hardening Soil model in principal stress space. On the other hand, a Mohr-Coulumb type yield surface in principal stress space comprises six corners and an apex that make singularity for the normal integration approach of constitutive equations. With respect to the isotropic nature of the material, a technique for processing these singularities by means of Koiter's rule, along with a transforming approach between both stress spaces for both stress tensor and consistent stiffness matrix based on spectral decomposition method, is introduced to provide such an approach for developing generalized Hardening Soil model in finite element analysis code ABAQUS. The implemented model is verified in comparison with the results after the original simulations of oedometer and triaxial tests by means of this model, for volumetric and shear hardenings respectively. Results from the simulation of oedometer test show similar shape of primary loading curve to the original one, while maximum vertical strain is a little overestimated for about 0.5% probably due to the selection of relationships for cap parameters. In simulation of triaxial test, the stress-strain and dilation curves are both in very good agreement with the original curves as well as test data.

• Communications for Statistical Applications and Methods
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• 제5권2호
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• pp.277-285
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• 1998

The smoothing parameter $\lambda$ in smoothing spline regression is usually selected by minimizing cross-validation (CV) or generalized cross-validation (GCV). But, simple CV or GCV is poor candidate for estimating prediction error. We defined MGCV (Multifold Generalized Cross-validation) as a criterion for selecting smoothing parameter in smoothing spline regression. This is a version of cross-validation using $leave-\kappa-out$ method. Some numerical results comparing MGCV and GCV are done.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2007년도 춘계학술발표대회
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• pp.873-874
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• 2007

In this paper, we make a detailed study about the routing related energy consumption problem in Wireless Sensor Networks. Based on this study, we present the selection criterion of the intermediate nodes so as to make the routing problem energy-efficient. Experimental results are provided with reasonable verification.

• Communications for Statistical Applications and Methods
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• 제6권1호
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• pp.169-180
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• 1999

A Markov Chain Monte Carlo method with development of computation is used to be the software system reliability probability model. For Bayesian estimator considering computational problem and theoretical justification we studies relation Markov Chain with Gibbs sampling. Special case of GOS with Superposition for Goel-Okumoto and Weibull models using Gibbs sampling and Metropolis algorithm considered. In this paper discuss Bayesian computation and model selection using posterior predictive likelihood criterion. We consider in this paper data using method by Cox-Lewis. A numerical example with a simulated data set is given.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.3-6
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• 2001

This paper presents optimal robust PID controller design method for second order systems to satisfy the design specifications in time domain. The parameters of PID controller are determinated by the weighting factors Q and R of cost function. It is suggested that the selection of Q and R matrix can be determinated by its relationship with the natural frequency of ITAE criterion.

• 천문학회지
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• 제29권spc1호
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• pp.197-198
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• 1996

We have carried out $^{13}CO$ J = 1 $\to$ 0 line observations with spatial resolution of 2' toward 17 small globules selected from the catalogue of Clemens & Barvainis (1988) with a selection criterion of [b] $\ge$ 15 degrees using the Nagoya 4-m radio telescope. Overall characteristics and physical parameters are presented and discussed by examining the $^{13}CO$ integrated intensity map for each of the globules.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.1004-1007
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• 1992

In this paper, we present a solution to the PID tuning problem by optimizing a GPC(General Predictive Control) criterion. The PID structure is ensured by constraning the parameters to a feasible set defined by the discrete-time Euler approximation of the ideal continuous-time PID controller. The algorithm is ectended by incorporating heuristic rules for selection of the significant design parameters. The algorithm has been successfully tested and some results are prewented.

• 대한전기학회논문지
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• 제43권2호
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• pp.318-329
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• 1994

This paper deals with the finite wordlength effect on the performance of digital PID controllers. The finite wordlength, one of the major limitation factors in digital controllers, results on two kinds of quantization error : the signal quantization error and the coefficient quantization error. This paper derives the variance of the plant output due to the signal quantization error. Using stability margins as performance criterion, the statistical wordlength concept is adopted for coefficient wordlength selection. Finally, the experimental results exhibit satisfactory performance of the digital PID controller with statistical coefficient wordlength.

• 한국통신학회논문지
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• 제22권3호
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• pp.423-431
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• 1997

A new decision tree generator MEC is proposed in this paper, which uses the difference of multi-base entropy as a consistent criterion for discretization and selection of attributes. To evaluate the performance of the proposed generator, it is compared to other generators which use criteria based on entropy and adopt different discretization styles. As an experimental result, it is shown that the proposed generator produces the most efficient classifiers, which have the least number of leaves at the same error rate, regardless of whether attribute values constituting the training set are discrete or continuous.