• 한국정보통신학회논문지
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• 제12권4호
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• pp.772-780
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• 2008

K-means는 알고리즘의 단순함과 효율적인 구현이 가능함으로 인해 군집화를 위해 현재까지 널리 사용되는 방법 중 하나이다. 하지만 K-means는 집단의 개수가 사전에 결정되어야 하는 근본적인 문제점이 있다. 이 논문에서는 BIC(Bayesian information criterion) 점수를 이용하여 효율적으로 집단의 개수를 추정할 수 있는 X-means 알고리즘을 확장한 두 가지 알고리즘을 제안한다. 제안한 방법은 기본적으로 X-means 방법을 따르면서 집단이 임의의 분산 행렬을 가질 수 있도록 함으로써 X-means 알고리즘이 원형 집단만을 허용함에 따른 over-fitting을 개선한다. 제안한 방법은 하나의 집단에서 시작하여 계속해서 집단을 나누어가는 하향식 방법으로, BIC score를 최대로 증가시키는 집단을 분할해 나간다. 제안한 알고리즘은 Modified X-means(MX-means)와 Generalized X-means(GX-means)의 두 가지로, 전자는 K-means 알고리즘을, 후자는 EM 알고리즘을 사용하여 현재 주어진 집단들에서 최적의 분할을 찾아낸다. MX-means는 GX-means보다 그 속도에서 앞서지만 집단들이 중첩 된 경우에는 올바른 집단을 찾아낼 수 없는 단점이 있다. GX-means는 실행 속도가 느린 단점이 있지만 집단들이 중첩된 경우에도 안정적으로 집단들을 찾아낼 수 있다. 이러한 점들은 일련의 실험을 통해서 확인할 수 있으며, 제안한 방법들이 기존의 방법들에 비해 나은 성능을 보임을 확인할 수 있다.

• 대한수학회보
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• 제50권2호
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• pp.485-498
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• 2013

In this paper, the Schur convexity is generalized to Schur $f$-convexity, which contains the Schur geometrical convexity, harmonic convexity and so on. When $f$ : ${\mathbb{R}}_+{\rightarrow}{\mathbb{R}}$ is defined as $f(x)=(x^m-1)/m$ if $m{\neq}0$ and $f(x)$ = ln $x$ if $m=0$, the necessary and sufficient conditions for $f$-convexity (is called Schur $m$-power convexity) of Gini means are given, which generalize and unify certain known results.

• 전자공학회논문지
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• 제54권4호
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• pp.61-67
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• 2017

방사선 노출의 위험을 줄이기 위한 저선량 X-ray 영상은 양자노이즈로 인해 화질열화가 발생한다. 본 논문은 저선량 X-ray 기기를 통해 입력받은 저화질의 동영상으로부터 포아송 확률 거리(Stochastic distance)에 기반하여 동영상 X-ray 데이터의 노이즈를 3차원 Non-local Means(3D NLM) 필터를 통해 제거한다. 포아송 확률 거리는 X-ray 영상에서 3D NLM 노이즈 제거 필터의 유사성을 판별하는 척도로써 사용되어 진다. 제안하는 방법은 움직임 정보가 포함된 프레임 유사도를 사용하여 움직임 아티팩트가 최소화된 X-ray 동영상 데이터를 출력하도록 한다. 수행한 결과로 노이즈가 제거된 X-ray 영상을 생성하도록 함으로써, 영상의 열화된 화질을 개선시켜 저선량 X-ray 영상 데이터에 대한 판독 능력을 향상시킬 수 있는 효과가 있다. 제안하는 방법은 객관적인 기준의 수치적인 관점에서 뿐만 아니라, 실제의 X 선 영상 시퀀스의 주관적인 시각적 인식에서도 뛰어남을 확인 할 수 있다.

• Journal of the Korean Data and Information Science Society
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• 제26권6호
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• pp.1495-1500
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• 2015

We obtain means and variances of max {X, Y} and min {X, Y} in the underlying Morgenstern type bivariate uniform variables X and Y with same scale parameters and different scale parameters respectively. And we obtain the conditional expectations in the underlying Morgenstern type bivariate uniform variables. Here, we shall consider the conditional expectations to know the dependence of one variable on the other variable and we consider the behaviors of means and variances of max {X, Y} and min {X, Y} with respect to changes in means, variances, and the correlation coeffcient of the underlying Morgenstern type bivariate uniform variables.

• 한국운동역학회지
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• 제15권3호
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• pp.153-159
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• 2005

The purpose of this study was to investigate the Effective X-Factor in golf swing. The term X-Factor means the relative rotation of shoulders with respect to hips during the golf swing. To ascertain the Effective X-Factor that resulted in a high club head speed at impact six golfers' swing motions were videotaped and analyzed using three-dimensional techniques. The results can be summarized as follows. The standard deviations of the professionals' average club head speeds were higher than the amateurs'. This means that the professionals' swing skills were better than amateurs' in driving accuracy and consistency. As the club head speeds were increased gradually the X-Factors and the club head speeds had reached to the subjects' average club head speeds, but the X-Factors and the club head speeds were not increased above the subjects' average club head speeds. The X-Factor Stretch early in the down swing was existed and Professional stretched values were higher than the amateurs. In conclusion my research results suggested that the increase in Effective X-Factors had no relationship to the increase in club head speeds.

• 대한수학회보
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• 제59권1호
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• pp.241-263
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• 2022

We consider a nonlinear Schrödinger equation with critical frequency, (P_𝜀) : 𝜀²∆v(x) - V(x)v(x) + |v(x)|^p-1v(x) = 0, x ∈ ℝ^N, and v(x) → 0 as |x| → +∞, for the infinite case as described by Byeon and Wang. Critical means that 0 ≤ V ∈ C(ℝ^N) verifies Ƶ = {V = 0} ≠ ∅. Infinite means that Ƶ = {x₀} and that, grossly speaking, the potential V decays at an exponential rate as x → x₀. For the semiclassical limit, 𝜀 → 0, the infinite case has a characteristic limit problem, (P_inf) : ∆u(x)-P(x)u(x) + |u(x)|^p-1u(x) = 0, x ∈ Ω, with u(x) = 0 as x ∈ Ω, where Ω ⊆ ℝ^N is a smooth bounded strictly star-shaped region related to the potential V. We prove the existence of an infinite number of solutions for both the original and the limit problem via a Ljusternik-Schnirelman scheme for even functionals. Fixed a topological level k we show that v_k,𝜀, a solution of (P_𝜀), subconverges, up to a scaling, to a corresponding solution of (P_inf ), and that v_k,𝜀 exponentially decays out of Ω. Finally, uniform estimates on ∂Ω for scaled solutions of (P_𝜀) are obtained.

• Kyungpook Mathematical Journal
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• 제55권4호
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• pp.909-931
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• 2015

This paper presents some new paranormed sequence spaces $X(r,s,t,p;{\Delta})$ where $X{\in}\{l_{\infty}(p),c(p),c_0(p),l(p)\}$ defined by using generalized means and difference operator. It is shown that these are complete linear metric spaces under suitable paranorms. Furthermore, the ${\alpha}$-, ${\beta}$-, ${\gamma}$-duals of these sequence spaces are computed and also obtained necessary and sufficient conditions for some matrix transformations from $X(r,s,t,p;{\Delta})$ to X. Finally, it is proved that the sequence space $l(r,s,t,p;{\Delta})$ is rotund when $p_n$ > 1 for all n and has the Kadec-Klee property.

• 한국재료학회지
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• 제13권1호
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• pp.48-52
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• 2003

The substituted yttrium iron garnet systems $Y_{ 3-x}$/Gd$_{x}$X$0.2_{0.2}$ $Fe_{4.8}$ $O _{12}$ (x = 0.2, 0.4, 0.6) have been investigated by means of X-ray diffraction, Mossbauer spectroscopy and SQUID. The X-ray diffraction patterns at room temperature confirm the samples to have a single phase of the garnet structure over the whole composition range. The lattice constants of all the samples linearly change with increasing x due to the size of substituted ions in the dodecahedral sites. $Y_{3-x}$ $Gd_{x}$ X$Fe_{4.8}$ $In_{0.2}$ $O_{12}$ system which $Y_{3-x}$ ions are substituted with Gd$^{ 3＋}$ ions, the Mossbauer spectrum consists of three Zeeman sextets at room temperature, one due to the $Fe^{3＋}$ ions on the octahedral(a-) sites and the others due to the $Fe^{3＋}$ ions on the tetrahedral(d-, d'-) sites, respectively. From the hysteresis loop measured by means of SQUID over the whole composition range, the saturation magnetization $M_{s}$ and magnetic moments $\mu_{ B}$ per unit cell have been obtained. The increment of Gd-ion content causes $M_{s}$ and $\mu_{B}$ decrease while the increment of In-ion content does not.

• Kyungpook Mathematical Journal
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• 제49권1호
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• pp.167-181
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• 2009

Based on Ricatti equation $XA^{-1}X=B$ for two (positive invertible) operators A and B which has the geometric mean $A{\sharp}B$ as its solution, we consider a cubic equation $X(A{\sharp}B)^{-1}X(A{\sharp}B)^{-1}X=C$ for A, B and C. The solution X = $(A{\sharp}B){\sharp}_{\frac{1}{3}}C$ is a candidate of the geometric mean of the three operators. However, this solution is not invariant under permutation unlike the geometric mean of two operators. To supply the lack of the property, we adopt a limiting process due to Ando-Li-Mathias. We define reasonable geometric means of k operators for all integers $k{\geq}2$ by induction. For three positive operators, in particular, we define the weighted geometric mean as an extension of that of two operators.

• 약학회지
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• 제32권1호
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• pp.80-85
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• 1988

QSAR of Salicylic acid derivatives, as anti-inflammatory agent, classified into Group I (not-having-5-phenyl ones) and Group II (having-5-phenyl ones) were investigated by quantum chemical calculations. The results are below: not significant statistically for both of Group I and Group II, but significant for each Group. $potency=-8.46X_{5}+1.639\;n=5\;r=0.77\;se=0.31\;for\;Group\;I.$ $({\pm}4.05)\;({\pm}0.5)$ where $X_5$ means charge of carbon atom bonded to hydroxyl radical. $potency=0.16X_{19}+7427.38HO-6629.85X_{15}+4977.40X_{10}+351.51X_5+3378.84$ $({\pm}0.17)\;({\pm}10.18)\;({\pm}11.70)\;({\pm}33.78)\;({\pm}4.41)\;({\pm}13.13)$ n=7 r=0.99 se=0.019 for Group II. where $X_{19}$ and $X_{15}$ stand for charges of the para carbon and the first carbon atoms in phenyl radical, respectively and $X_{10}$, charge of carboxylic carbon atom, HO, HOMO energy. It seems to be possible to qualitatively predict potency of drug by Pearson's HSAB theory. It means that drug should possess low LUMO energy and high HOMO energy.