• Journal of Korean Institute of Industrial Engineers
• /
• v.19 no.2
• /
• pp.15-21
• /
• 1993

This paper considers the optimal design of accelerated life test in which the stress is linearly increased. It discusses the special case when the life distribution under constant stress follows an exponential distribution and the accelerated equation satisfies the inverse power law. It is assumed that cumulative damage is linear, that is, the remaining life of test units depends only on the current cumulative fraction failed and current stress(cumulative exposure model). The optimization criterion is the asymptotic variance of the maximum likelihood estimator of the log mean life at a design stress. The optimal increasing rate is obtained to minimize the asymptotic variance. Table of sensitivity analysis is given for the prior estimators of model parameters.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.9C
• /
• pp.849-853
• /
• 2005

Signal detectors often utilize nonlinear statistics of observations rather than the observation as they are. The sign statistic, a typical example of the nonlinear statistics, for example, relies oかy on the sign information of observations. In this letter, a qualitative analysis is presented that the correlation coefficients between the statistics and original observations can be used to predict the asymptotic performance of a detection schemes utilizing the nonlinear statistics.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.37 no.6
• /
• pp.1-6
• /
• 2000

In this paper, the problem of the stability analysis for linear neutral delay-differential systems with nonlinear perturbations is investigated. Using Lyapunov second method, a new delay-dependent sufficient condition for asymptotic stability of the systems in terms of linear matrix inequalities (LMIs), which can be easily solved by various convex optimization algorithms, is presented. A numerical example is given to illustrate the proposed method.

• Journal of the Chungcheong Mathematical Society
• /
• v.21 no.1
• /
• pp.107-116
• /
• 2008

In this study the k-fold pseudo-Cauchy's method of order k+3 is proposed from the classical Cauchy's method defined by an iteration $x_{n+1}=x_n-{\frac{f^{\prime}(x_n)}{f^{{\prime}{\prime}}(x_n)}}{\cdot}(1-{\sqrt{1-2f(x_n)f^{{\prime}{\prime}}(x_n)/f^{\prime}(x_n)^2}})$. The convergence behavior of the asymptotic error constant is investigated near the corresponding simple zero. A root-finding algorithm with the k-fold pseudo-Cauchy's method is described and computational examples have successfully confirmed the current analysis.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2005.11a
• /
• pp.198-201
• /
• 2005

This study investigates the difference between single-cell and multi-cell cross-sections of thin-walled beams. The variationally and asymptotically consistent theory is used in order to model the two-cell thin- walled beam. The theory is based on an asymptotical analysis of two-dimensional shell energy. In addition, the method allows for the development of closed-form expressions for the displacement, stress field and beam stiffness coefficients. The numerical results show the difference between the cross-sectional stiffness of single-cell and that of multi-cell.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.17-22
• /
• 2002

Non-uniform and unsteady inflow into a Horizontal Axis Wind Turbine (HAWT) brings about an asymmetric flow field on the rotor plane and an unsteady aerodynamic load on the blades. In the present paper effects of yawed inflow and wind shear are analyzed by an inviscid aerodynamic model based on the asymptotic acceleration potential method. In the analysis the rotor blades are represented by spanwise and chordwise pressure distribution composed of analytical first-order asymptotic solutions for the Laplace equation. As the actual wind field experienced by a HAWT is turbulent, the effects of the turbulence are also examined using the Veers' model.

• Journal of KSNVE
• /
• v.9 no.3
• /
• pp.461-465
• /
• 1999

This paper presents theoretical analyses for unstable vibrations caused by the couple of bending and torsion in a rotating shaft driven through a universal joint. A driving shaft is assumed to be rigid and to rotate with a constant angular velocity. The driven shaft system consists of a flexible shaft with a circular section and a symmetrical rotor attached at a point between the shaft ends. Equations of motion derived hold with an accuracy of the second order of shaft deformations, and are analyzed by the asymptotic method. The vibrations become unstable when the driving shaft rotates with the angular velocity to be approximately equal to half of the sum of the natural frequencies for whirling and torsional vibrations.

• Journal of the Korean Statistical Society
• /
• v.25 no.2
• /
• pp.289-301
• /
• 1996

This paper suggests a new diagnostic measure for detecting influential observations in two group linear discriminant analysis(LDA). It is developed from an information theoretic point of view using the minimum discrimination information(MDI) methodology. MDI estimator of symmetric divergence by Kullback(l967) is taken as a measure of the power of discrimination in LDA. It is shown that the effect of an observation over the power of discrimination is fully explained by the diagnostic measure. Asymptotic distribution of the proposed measure is derived as a function of independent chi-squared and standard normal variables. By means of the distributions, a couple of methods are suggested for detecting the influential observations in LDA. Performance of the suggested methods are examined through a simulation study.

• Journal of the Korean Data and Information Science Society
• /
• v.10 no.2
• /
• pp.341-357
• /
• 1999

Greenwich and Jahr-Schaffrath(1995) considered a new process incapability index(PII) $C_{pp}$, which modified the useful index $C^{\ast}_{pm}{$ for detecting assignable causes. The new index $C_{pp}$ provides an uncontaminated separation between information concerning the process accuracy and precision while this kind of information separation is not available with the $C^{\ast}_{pm}$ index. In this paper, we will study about the index $C_{pp}$ based on the bootstrap. First, we will prove the consistency of bootstrap deriving the bootstrap asymptotic distribution for our index $C_{pp}$. Moreover, with the consistency of bootstrap, we will construct six bootstrap confidence intervals and compare their performances. Some simulation results, comparison and analysis are provided. In particular, two STUD and ABC bootstrap methods perform significantly better.

• Journal of Ocean Engineering and Technology
• /
• v.2 no.1
• /
• pp.46-58
• /
• 1988

The experimental investigations on the motion characteristics of a marine riser both in air and water were performed. The static deflections and natural frequencies of the riser in air including the effect of static offset, were obtained from the experiment. These results were compared with those of theoretical prediction by using a simple asymptotic formula. In order to investigate the nonlinear motion characteristics of the riser subject to nonlinear viscous drag and large displacement, the forced oscillation tests both in air and water were performed. In the forced oscillation tests in air, it was found that the transverse motion due to geometrical nonlinearity grows when the amplitude of in-line oscillation exceeds a certain critical value, say, order of 1-2 diameters. The planar motions of the riser in water due to vortex shedding and the geometrical nonlinearity were described. Some of these results were also compared with those of theoretical analysis, which uses a numerical perturbation technique based on the derived linear asymptotic solutions, and found to be generally in good agreement.