• 대한기계학회논문집A
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• 제27권12호
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• pp.2047-2054
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• 2003

In this paper, an approach of automatically finding and modifying the most appropriate orthogonal array (GO) is suggested and applied to a new structural optimization procedure with two steps. GO is motivated by the situation where finding a proper orthogonal array from the tables in the literature is difficult or impossible. Now the Taguchi method is made available for various numbers of variables and levels. In the two-step structural optimization, the Taguchi method equipped with GO and a shape optimization using the finite differencing method is consecutively applied. The existence or non-existence of an element can be taken as a factor level and this feature is utilized finding the best topology from a set of potential topologies suggested from the user's expertise. This greatly enhances applicability and one can expect a better result than the case in which each step is applied independently because these steps are complementary each other.

• 전자공학회논문지B
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• 제31B권4호
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• pp.18-29
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• 1994

For the efficient recognition of Korean Alphabets, we proposed the tree structure algorithm which was based on K-tuple NRF-SDF using representative images as training images. Representative images consisted of ECP-SDF images of several consonants or vowels. To reduce the effect of sidelobe in the output correlation plane, we used the representative images as training images and obtained the elements of a vector inner product matrix using the peak value of AMPOF correlation of training images with one another. The proposed algorithm consisted of three main-step containing several substeps. In filter synthesis of each step, representative images were used as training images in the first and the second main-step and each consonant or vowel was used as training images in the third main-step. The performance of this algorithm is demonstrated by computer simulation and optical experiment.

• 응용통계연구
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• 제9권1호
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• pp.53-73
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• 1996

일정형 및 계단형 가속수명시험의 시험설계에 대한 일반적인 모형과 최적설계에 대한 최근의 연구결과를 소개하고, 수명분포가 와이블인 경우에 대하여 두가지 시험방법에 대한 최적설계를 점근분산의 행태, 설계변수의 효과, 최적시험조건에서 시험종결 시점까지의 기대고장개수 및 기대시험종결시간, 점근분산의 상대적효율과 설계변수의 사전추정치에 대한 둔감성의 측면에서 비교, 분석하였다.

• International Journal of Reliability and Applications
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• 제15권1호
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• pp.23-50
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• 2014

This paper deals with formulation of optimum multi-objective modified step-stress accelerated life test (ALT) plan for Burr type-XII distribution under type-I censoring. Since it is impractical to estimate only one objective parameter after conducting costly ALT tests; also, it is not desirable to assume instantaneous changes in stress levels because of limited capacity of test equipments and the presence of undesirable failure modes, therefore, an optimum multi-objective modified step-stress ALT plan has been designed. The optimal test plan consists in determining the optimum low stress level and optimal time at which stress starts linearly increasing from low stress by minimizing the weighted sum of the asymptotic variances of the maximum likelihood estimator of quantile lifetimes at design constant stress. The method developed has been illustrated using an example. Sensitivity analysis has been carried out. Comparative study has also been done to highlight the merits of the proposed model.

• Structural Engineering and Mechanics
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• 제5권1호
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• pp.59-68
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• 1997

A two-step method is presented for the optimum design of trusses with available sections under stress and Euler buckling constraints. The shape design of the truss is used as a means to convert the discrete solution into a continuous one. In the first step of the method, a continuous solution is obtained by sizing and shape design using an approximate polynomial expression for the buckling coefficients. In the second step, the member sizes obtained are changed to the nearest available sections and the truss is reconfigured by using the exact values for the buckling coefficients. The optimizer used is based on the sequential quadratic programming and the gradients are evaluated in closed form. The method is illustrated by two numerical examples.

• Nuclear Engineering and Technology
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• 제44권6호
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• pp.689-696
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• 2012

A small integral reactor SMART (System Integrated Modular Advanced ReacTor), being developed in Korea since late 1990s and targeted to obtaining a standard design approval by the end of 2011, is introduced. The design scope and level for design certification (DC) is well described in the U.S. NRC SECY documents published the early 1990s. However, the documents are valid for a one-step licensing process called a combined operating license (COL) by the U.S. NRC, while Korea still uses a two-step licensing process. Thus, referencing the concept of the SECY documents, we have established the design scope and level for the SMART DC using the contexts of the standard review plan (SRP). Some examples of the results and issues raised during our review are briefly presented in this paper. The same methodology will be applied to other types of reactor under development in Korea, such as future VHTR reactors.

• 한국시뮬레이션학회논문지
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• 제9권3호
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• pp.91-102
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• 2000

The distribution routing problem is one of the important problems in distribution and supply center management. This research is concerned with an integrated distribution routing problem for multi-supply centers based on improved genetic algorithm and GUI-type programming. In this research, we used a three-step approach; in step 1 a sector clustering model is developed to transfer the multi-supply center problem to single supply center problems which are more easy to be solved, in step 2 we developed a vehicle routing model with time and vehicle capacity constraints and in step 3, we developed a GA-TSP model which can improve the vehicle routing schedules by simulation. For the computational purpose, we developed a GUI-type computer program according to the proposed methods and the sample outputs show that the proposed method is very effective on a set of standard test problems, and it could be potentially useful in solving the distribution routing problems in multi-supply center problem.

• International Journal of Fluid Machinery and Systems
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• 제5권4호
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• pp.143-151
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• 2012

Predicting the future condition of machine and assessing the remaining useful life are the center of prognostics. This paper contributes a new prognostic method based on grey model and survival probability. The first step of the method is building a normal condition model then determining the error indicator. In the second step, the survival probability value is obtained based on the error indicator. Finally, grey model coupled with one-step-ahead forecasting technique are employed in the last step. This work has developed a modified grey model in order to improve the accuracy of prediction. For evaluating the proposed method, real trending data of low methane compressor acquired from condition monitoring routine were employed.

• KIEE International Transaction on Systems and Control
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• 제2D권2호
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• pp.97-107
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• 2002

In this paper, we propose the concept of orthonormalized compressed measurement for the stability analysis of discrete linear time-varying Kalman filters. Unlike previous studies that deal with the homogeneous portion of Kalman filters, the proposed Lyapunov method directly deals with the stochastically-driven system. The orthonorrmalized compressed measurement provides information on the a priori state estimate of the Kalman filter at the k-th step that is propagated from the a posteriori state estimate at the previous block of time. Since the complex multiple-step propagations of a candidate Lyapunov function with process and measurement noises can be simplified to a one-step Lyapunov propagation by the orthonormalized compressed measurement, a stochastic radius of attraction can be derived that would be impractically difficult to obtain by the conventional multiple-step Lyapunov method.

• KIEE International Transactions on Electrophysics and Applications
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• 제5C권6호
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• pp.270-275
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• 2005

In order for the application of the in-vivo endoscopic biopsy, a micromirror which can be driven at a low voltage is required. In this paper, a two-step micromirror composed of bottom electrodes, moving plate and top mirror plate is proposed. Because an electrical wiring of two plates are separated, they can be actuated separately. Therefore, an intermediate moving plate plays an important role in reducing the driving voltage in half. The designed device was fabricated by the surface micromachining. Maximum rotation angle of $6.3^{\circ}$ was obtained by applying DC 48V, while a conventional one-step mirror pulled down at DC 120V. The designed structure can be used in microphotonic applications requiring low driving voltage.