• East Asian mathematical journal
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• v.30 no.3
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• pp.311-319
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• 2014

It is shown that, for an even positive integer m with $m{\geq}4$ and arbitrary positive integer k and t, the complete multipartite graph $K_{km+1(2t)}$ can be decomposed into edge-disjoint gregarious m-cycles in such a way that the decomposition is circulant.

• Communications for Statistical Applications and Methods
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• v.14 no.1
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• pp.215-227
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• 2007

Variable selection algorithm for Sliced Inverse Regression using penalty function is proposed. We noted SIR models can be expressed as generalized eigenvalue decompositions and incorporated penalty functions on them. We found from small simulation that the HARD penalty function seems to be the best in preserving original directions compared with other well-known penalty functions. Also it turned out to be effective in forcing coefficient estimates zero for irrelevant predictors in regression analysis. Results from illustrative examples of simulated and real data sets will be provided.

• Honam Mathematical Journal
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• v.32 no.1
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• pp.101-112
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• 2010

Using some interesting convolution, we find kernels recovering the given function f. By a slight change of this convolution, we obtain an identity filter related to the Fourier series in the discrete time domain. We also introduce some techniques to decompose an impulse into several dilated pieces in the discrete domain. The detail examples deal with specific constructions of those decompositions. Also we obtain localized moving averages from a decomposition of an impulse to make hybrid Bollinger bands, that might give various strategies for stock traders.

• Bulletin of the Korean Mathematical Society
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• v.45 no.2
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• pp.355-363
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• 2008

For a Boolean rank 1 matrix $A=ab^t$, we define the perimeter of A as the number of nonzero entries in both a and b. The perimeter of an $m{\times}n$ Boolean matrix A is the minimum of the perimeters of the rank-1 decompositions of A. In this article we characterize the linear operators that preserve the perimeters of Boolean matrices.

• Bulletin of the Korean Mathematical Society
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• v.49 no.3
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• pp.589-599
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• 2012

An element of a ring is called strongly nil clean provided that it can be written as the sum of an idempotent and a nilpotent element that commute. We characterize, in this article, the strongly nil cleanness of $2{\times}2$ and $3{\times}3$ matrices over $R[x]/(x^2-1)$ where $R$ is a commutative local ring with characteristic 2. Matrix decompositions over fields are derived as special cases.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.17 no.3
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• pp.139-170
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• 2013

We extend a p-hierarchical decomposition of the second degree finite element space of N$\acute{e}$d$\acute{e}$lec for tetrahedral meshes in three dimensions given in [1] to meshes with hexahedral elements, and derive p-hierarchical decompositions of the second degree finite element space of Raviart-Thomas in two dimensions for triangular and quadrilateral meshes. After having proved stability of these subspace decompositions and requiring certain saturation assumptions to hold, we construct a local a posteriori error estimator for fem and bem coupling of a time-harmonic electromagnetic eddy current problem in $\mathbb{R}^3$. We perform some numerical tests to underline reliability and efficiency of the estimator and test its usefulness in an adaptive refinement scheme.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.65.2-65.2
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• 2016

We present a new database of our two-dimensional bulge-disk decompositions for 14,482 galaxies drawn from SDSS DR12 in order to examine the properties of bulges residing in the local universe (0.005 < z < 0.05). We performed decompositions in g and r bands by utilizing the GALFIT software. The bulge colors and bulge-to-total ratios are found to be sensitive to the details in the decomposition technique. The g-r colors of bulges derived are almost constantly red regardless of bulge size except for the bulges in the low bulge-to-total ratio galaxies (approximately $B/T_r{\leq}0.3$). Bulges exhibit similar scaling relations to those followed by elliptical galaxies, but the bulges in galaxies with lower bulge-to-total ratios clearly show a gradually larger departure in slope from the elliptical galaxy sequence. The scatters around the scaling relations are also larger for the bulges in galaxies with lower bulge-to-total ratios. Both the departure in slopes and larger scatters are likely originated from the presence of young stars. While bulges seem largely similar in optical properties to elliptical galaxies, they do show clear and systematic departures as a function of bulge-to-total ratio. The stellar properties and perhaps associated formation processes of bulges seem much more diverse than those of elliptical galaxies.

• International Area Studies Review
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• v.13 no.3
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• pp.309-330
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• 2009

This paper analyzes comparatively the effects of changes in real effective exchange rates on the business fluctuations of the cases of Korea and Japan employing structural vector auto-regression(S-VAR) model which uses quarterly data for the five variables of real effective exchange rates, GDP gap, real interest rates, oil prices, inflation rates for the period of 1980-2006. The paper employes impulse-response analysis and variance decompositions. The paper finds that real exchange rate depreciations are contractionay for the case of Korea while they are expansionary for the case of Japan. These results are consistent with the prevailing empirical results that real exchange rate depreciations are contractionary for developing countries while expansionary for advanced countries.

• Journal of applied mathematics & informatics
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• v.17 no.1_2_3
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• pp.663-670
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• 2005

In this paper we shall give some decompositions derived from cyclic subautomata or neighborhoods of the automaton. Also we shall discuss some characterizations of cyclic automata when an automaton is maximal cyclic refinement. If m $\in$ M is totally reachable state, we shall see that {$mX^{\ast}$} is minimal.

• Bulletin of the Korean Mathematical Society
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• v.35 no.1
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• pp.33-43
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• 1998

Matlis posed the following question in 1958: if N is a direct summand of a direct sum M of indecomposable injectives, then is N itself a direct sum of indecomposable innjectives\ulcorner It will be proved that the Matlis problem has an affirmative answer when M is a multiplication module, and that a weaker condition then that of M being a multiplication module can be given to module M when M is a countable direct sum of indecomposable injectives.