• Communications for Statistical Applications and Methods
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• v.6 no.3
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• pp.719-728
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• 1999

This paper discusses an optimal burn-in procedure to minimize total costs based on the assumption that the failure rate pattern follows a bimodal mixed Weibull distribution. The procedure will consider warranty period as a factor of the total expected burn-in cost. A cost model is formulated to find the optimal burn-in time that minimizes the expected burn-in cost. Conditional reliability for warranty period will be discussed. An illustrative example is included to show how to use the cost model in prctice.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.19 no.39
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• pp.285-292
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• 1996

In the case of existence of second-hand market, some methods for economic depreciation measurement have been developed. Among them, we consider two method. Those are Box -Cox model by Halten and Wykoff and Ratio method of T-factor by Iowa State University. Here, we suggest a new measurement method of economic depreciation based on the above two methods. According to the new method, we can get the failure rate of a equipment under the appropriate assumption. Then we can measure the economic depreciation more simply.

• Journal of applied mathematics & informatics
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• v.41 no.1
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• pp.155-165
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• 2023

We consider circular Rayleigh problem of hydrodynamic stability which deals with linear stability of axial flows of an incompressible iniviscid homogeneous fluid to axisymmetric disturbances. For this problem, we obtained two parabolic instability regions which intersect with Batchelor and Gill semi-circle under some condition. This has been illustrated with examples. Also, we derived upper bound for the amplification factor.

• Journal of applied mathematics & informatics
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• v.41 no.2
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• pp.363-372
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• 2023

We consider Kuo problem of hydrodynamic stability which deals with incompressible, inviscid, parallel shear flows in the 𝛽-plane. For this problem, we derived instability region without any approximations and which intersects with Howard semi-circle region under certain condition. Also, we derived upper bound for growth rate and amplification factor of an unstable mode and proved Howard's conjecture.

• Journal of applied mathematics & informatics
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• v.41 no.5
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• pp.1071-1084
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• 2023

We consider inviscid, incompressible homogeneous shear flows of variable cross section known as extended Rayleigh problem. For this extended Rayleigh problem, we derived instability region which intersect with semi-circle instability region under some condition. Also we derived condition for stability, upper bound for amplification factor and growth rate of an unstable mode.

• The Pure and Applied Mathematics
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• v.30 no.4
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• pp.377-395
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• 2023

The purpose of this paper is to consider the abstract theory of hypernear rings. In this regard, we derive the isomorphism theorems for hypernear rings as well as Chinese Remainder theorem. Our results can be considered as a generalization for the cases of Krasner hyperrings, near rings and rings.

• Communications for Statistical Applications and Methods
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• v.19 no.3
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• pp.495-500
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• 2012

We consider a Bayesian test of independence in a two-way contingency table that has some zero cells. To do this, we take a three-stage hierarchical Bayesian model under each hypothesis. For prior, we use Dirichlet density to model the marginal cell and each cell probabilities. Our method does not require complicated computation such as a Metropolis-Hastings algorithm to draw samples from each posterior density of parameters. We draw samples using a Gibbs sampler with a grid method. For complicated posterior formulas, we apply the Monte-Carlo integration and the sampling important resampling algorithm. We compare the values of the Bayes factor with the results of a chi-square test and the likelihood ratio test.

• Journal of Korea Society of Digital Industry and Information Management
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• v.9 no.3
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• pp.21-30
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• 2013

Powell-Miller theory is a good method to express or treat incorrect information. But it has limitation that requires too much time to apply to actual situation because computational complexity increases in exponential and functional way. Accordingly, there have been several attempts to reduce computational complexity but side effect followed - certainty factor fell. This study suggested expanded Approximation Algorithm. Expanded Approximation Algorithm is a method to consider both smallest supersets and largest subsets to expand basic space into a space including inverse set and to reduce Approximation error. By using expanded Approximation Algorithm suggested in the study, basic probability assignment function value of subsets was alloted and added to basic probability assignment function value of sets related to the subsets. This made subsets newly created become Approximation more efficiently. As a result, it could be known that certain function value which is based on basic probability assignment function is closely near actual optimal result. And certainty in correctness can be obtained while computational complexity could be reduced. by using Algorithm suggested in the study, exact information necessary for a system can be obtained.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.65.1-65.1
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• 2010

Thermal performance tests of solar thermal collectors include determination of coefficient parameters in an efficiency equation. The parameters can be estimated using regression method to minimize an objective function as sum of differences between measured efficiency data and regressed efficiency equation. However, this conventional approach doesn't consider measurement uncertainties. In this presentation, a method to determine regression parameters in the efficiency equation and uncertainties of the parameters is described with mainly mathematical expressions based on literature reviews. In the method, parameters in the equation for collector efficiency can be determined using regression analysis with a weighting factor in the objective function. The weighting factor can be uncertainties of the differences between measured and fitted efficiencies. To evaluate the approach, performance estimation of a solar collector using the efficiency equation with uncertainties is compared to the result using the conventional efficiency equation by a simulated way for a case in one of previous studies.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.327-334
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• 2002

This paper develops an optimized torsional design method of asymmetric wall structures considering deformation capacities of walls. Contrary to the current torsional provisions, a deformation based torsional design is based on the assumption that stiffness and strength are dependent. Current torsional provisions specify two design eccentricity of stiffness to calculate the design forces of members. But such a methodology leads to an excessive over-strength of some members and an optimal torsional behavior is not ensured. Deformation-based torsional design uses displacement and rotation angle as design parameters and calculates base shear for inelastic torsional response directly. Because optimal torsional behavior can be defined based on the deformation of members, deformation based torsional design procedure can be applied to the optimal and performance-based torsional design. To consider the effect of accidental eccentricity, an over-strength factor is defined. The over-strength factor is determined from performance level, torsional resistance and arrangement of walls.