• Communications for Statistical Applications and Methods
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• v.10 no.1
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• pp.79-88
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• 2003

In this paper, we study the efficiency of the stratified estimator in related with the variance lower bound of Horvitz-Thompson estimator subject to the superpopulation model. Especially, we compare the variance lower bound of optimum allocation with that of power allocation subject to Dalenius-Hedges stratification.

• Journal of the Korean Statistical Society
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• v.23 no.1
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• pp.187-198
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• 1994

We derive a new Cramer-Rao type lower bound for the reciprocal of the density height of the median-unbiased estimators which improves most of the previous lower bounds and is attainable under much weaker conditions. We also identify useful necessary and sufficient condition for the attainability of the lower bound which is considerably weaker than those for the mean-unbiased estimators. It is shown that these lower bounds are attained not only for the family of continuous distributions with monotone likelihood ratio (MLR) property but also for the location and scale families with strong unimodal property.

• Geomechanics and Engineering
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• v.11 no.4
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• pp.587-605
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• 2016

This study aimed to develop upper and lower bounds to predict the tunnel support pressure under the pile tip during the circular tunnel excavation. Most previous studies on the upper and lower bound methods were carried out for the single ground structures, e.g., retaining wall, foundation, ground anchor and tunnel, in the homogeneous ground conditions, since the pile-soil-tunnel interaction problem is very complicated and sophisticated to solve using those bound methods. Therefore, in the lower bound approach two appropriate stress fields were proposed for single pile and tunnel respectively, and then they were superimposed. In addition, based on the superimposition several failure mechanisms were proposed for the upper bound solution. Finally, these upper bound mechanisms were examined by shear strain data from the laboratory model test and numerical analysis using finite element method.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.859-863
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• 1987

In this paper, a relationship between difference triangular sets and sum triangular sets is developed to evaluate the weighted number of the third-order intermodulation products. In addition, a lower bound of the intermodulation products falling into the worst signal channel has been derived using the relationship between difference triangular sets and sum triangular sets. The formulas of the lower bound are useful for estimating the intermodulation impairment level in satellite communication systems.

• Journal of the Korean Statistical Society
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• v.21 no.1
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• pp.27-34
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• 1992

This paper provides a method of obtaining a lower bound on the probability of correct selection for a two-stage selection procedure. The resulting lower bound sharpens that by Tamhane and Bechhofer (1979) for the normal means problem with a common known variance. The design constants associated with the lower bound are computed and the results of the performance comparisons are given.

• Journal of Korean Society for Quality Management
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• v.22 no.1
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• pp.205-213
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• 1994

We construct a new lower bound of Cramer-Rao type for the median-unbiased estimator in the presence a nuisance parameter. We also identify useful necessary and sufficient conditions for the attainability of the lower bound. Some applications including the analysis of censored reliability data are considered as examples.

• Bulletin of the Korean Mathematical Society
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• v.30 no.2
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• pp.229-238
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• 1993

Let M be an n-dimensional compact Riemannian manifold with boundary .part.M. We consider the Neumann eigenvalue problem on M of the equation (Fig.) where .upsilon. is the unit outward normal vector to the boundary .part.M. due to the importance of Poincare inequality for analysis on manifolds, one wishes to obtain the lower bound of the first non-zero eigenvalue .eta.$_{1}$ of (1.1). For the purpose of applications, it is important to relax the dependency of the lower bound on the geometric quantities. For general compact manifolds with convex boundary, Li-Yau [3] obtained the lower bound of .eta.$_{1}$. Recently, Roger Chen [1] investigated the lower bound of the first Neumann eigenvalue .eta.$_{1}$ on compact manifold M with nonconvex boundary. We investigate the lower bound .eta.$_{1}$ with the same conditions as those of Roger chen. But, using the different auxiliary function, we have the following theorem.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.9
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• pp.664-668
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• 2003

A new sliding mode control method based on the lower bound of control gain is presented. Although the magnitube of the proposed control input is larger than that of the conventional control input using both lower and upper bounds, the positive-negative exchanging chattering is reduced and reaching mode is shorter. Because the proposed scheme needs only the lower bound of control gain, it is applicable to the system whose upper bound of control gain is doubtful to determine such as the control gain depends on the system states. It is proved that the proposed control method guarantees the sliding condition. The analysis of differences between the conventional method and the proposed method is given. The validity of the proposed control strategy is shown through a 2nd-order nonlinear system example.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.45
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• pp.291-299
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• 1998

We present a variant for the generalized continuous multiple-choice knapsack problem[1], which additionally has the well-known generalized lower bound constraints. The presented problem is characterized by some variables which only belong to the simple upper bound constraints and the others which are partitioned into both the continuous multiple-choice constraints and the generalized lower bound constraints. By exploiting some extended structural properties, an efficient algorithm of order Ο($n^2$1og n) is developed, where n is the total number of variables. A numerical example is presented.

• Bulletin of the Korean Mathematical Society
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• v.55 no.3
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• pp.735-747
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• 2018

This paper deals with the asymptotic behavior of solutions to the generalized MHD and Hall-MHD systems. Firstly, the upper bound for the generalized MHD and Hall-MHD systems is investigated in $L^2$ space. Then, the effect of the Hall term is analyzed. Finally, we optimize the upper bound of decay and obtain their algebraic lower bound for the generalized MHD system by using Fourier splitting method.