• 한국환경과학회지
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• 제17권12호
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• pp.1331-1341
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• 2008

For providing basic data on estuary conservation and pattern of vegetation succession of sand bar, the flora of delta was investigated from March 2004 to August 2006 in the Nakdong River estuary of Korea. The flora in the eight surveyed areas was composed of total 159 taxa that belonged to 46 families, 123 genera, 133 species, 1 subspecies, 20 varieties, and 5 forms. Among them, naturalized plants and evergreen broad trees were 31 taxa and 5 taxa, respectively. The communities of main species at delta of estuary were composed of 16 species such as Rosa rugusa community, Scirpus triqueter community, Phragmites communis community, Carex kobomugi community, Digitaria ciliaris community. Especially, Rosa rugusa community which are important to establish the southern limit line of distribution as the northern factor was distributed through Jinwoodo. The succession of main vegetation community in the new delta (Doyodeung) was in order of Carex scabrifolia, Scirpus triqueter, Phragmites communis, Imperata cylindrica var. koenigii and Miscanthus sinensis var. purpurascens. Therefore, the succession order of the surveyed area seems to predict the pattern of the vegetation succession of another deltas in Nakdong River estuary.

• 대한수학회보
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• 제50권4호
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• pp.1377-1387
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• 2013

Let $f$ be a harmonic mapping on the unit disc ${\Delta}$ in $\mathbb{C}$. We give some condition for $f$ to be a quasiconformal homeomorphism on ${\Delta}$ and to have a quasiconformal extension to the whole plane $\bar{\mathbb{C}}$. We also obtain quasiconformal extension results for starlike harmonic mappings of order ${\alpha}{\in}(0,1)$.

• 자원환경지질
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• 제24권3호
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• pp.219-226
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• 1991

High quality quartz crystals are grown in 0.5N NaOH + LiOH solution on the seed crystal at $370-395^{\circ}C$ and $1200-1300kg/cm^2$ condition. Growth rates are determined by the crystal thickness grown on the seed crystals with Z(0001) and X($11\bar{2}0$) direction. Relatively high growth rate of Z(0001) direction gradually changes as the temperaure difference (${\Delta}$ Ti) between growth and dissolution zones from 25 to $10^{\circ}C$. The X axis direction is affeced by ${\Delta}$ Ti, and +X($11\bar{2}0$) direction shows a high growth rate than -X($\bar{1}\bar{1}20$) direction. According to the variation with kinds of solutions used, the crystal growth that in NaOH solution is found to be slower than that in $Na_2CO_3$ solution. However, for the case in the NaOH solution mixed with LiOH, it shows a favorable growth rate in terms of grown crystal quality.

• 한국지진공학회논문집
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• 제4권3호
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• pp.99-105
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• 2000

한반도 동남부 지역에서 발생하고 관찰된 약진 또는 중진의 자료를 이영하여 이 지역의 Q값과 지진원의 특성인 모서리 주파수 (fc), 응력강하량(Δ$\delta$) 및 모멘크규모 (Mw)를 산정하였다. 가속도 스펙트럼의 경사와 관련된 x의 통계학적 분포로부터 추정한 Q의 95% 신뢰범위는 1656~2454 이다. 1998년 1월 18일 울산 앞바다 지진과 1997년 6월 26일 경주지진의 지진원 요소를 구한 결과 fc 는 각각 4.22Hz , 2.94Hz, Δ$\delta$는 각각 106.8 bar, 106.2 bar, Mw는 각각 3.9, 4.0으로 추정되었다. 제한된 자료수로 인하여 이들의 통계학적 성질을 충분히 규명하지는 못하였지만 다른 연구자들의 기존결과와 유사한 값을 보인다. 본 연구의 결과는 강진동 모사에 직접 이용이 가능하며, 이 지역에 위치한 원자력 발전소 내진 안전성 검토에도 이용될 수 있다.

• Journal of the Korean Statistical Society
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• 제24권2호
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• pp.337-347
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• 1995

In the problem of some sequential estimation, the stopping times may be written in the form $N(c) = inf{n \geq n_0; n \geq c^2 S^2_n/\delta^2 (\bar{X}_n)}$ where ${s^2_n}$ and ${\bar{X}_n}$ are the sequences of sample variance and sample mean of the independently and identically distributed (i.i.d.) random variables with distribution $F_{\theta}(x), \theta \in \Theta$, respectively, and $\delta$ is either constant or any given positive real valued function. We obtain some asymptotic normality and asymptotic expectation of the N(c) in various limiting situations. Specially, uniform asymptotic normality and uniform asymptotic expectation of the N(c) are given.

• 대한수학회보
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• 제61권4호
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• pp.999-1017
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• 2024

In this paper, we study the Neumann problem for the complex Hessian quotient equation ${\frac{{\sigma}_k({\tau}{\Delta}uI+{\partial}{\bar{\partial}u)}}{{\sigma}_l({\tau}{\Delta}uI+{\partial}{\bar{\partial}u)}}}={\psi}$ with 0 ≤ 𝑙 < k ≤ n. We prove a priori estimate and global C¹ estimates, in particular, we use the double normal second derivatives on the boundary to establish the global C² estimates and prove the existence and the uniqueness for the Neumann problem of the above complex Hessian quotient equation.

• 대한수학회보
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• 제55권6호
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• pp.1869-1889
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• 2018

We are concerned with the following fractional p-Laplacian inclusion: $$(-{\Delta})^s_pu+V(x){\mid}u{\mid}^{p-2}u{\in}{\lambda}[{\underline{f}}(x,u(x)),\;{\bar{f}}(s,u(x))]$$ in ${\mathbb{R}}^N$, where $(-{\Delta})^s_p$ is the fractional p-Laplacian operator, 0 < s < 1 < p < $+{\infty}$, sp < N, and $f:{\mathbb{R}}^N{\times}{\mathbb{R}}{\rightarrow}{\mathbb{R}}$ is measurable with respect to each variable separately. We show that our problem with the discontinuous nonlinearity f admits at least one or two nontrivial weak solutions. In order to do this, the main tool is the Berkovits-Tienari degree theory for weakly upper semicontinuous set-valued operators. In addition, our main assertions continue to hold when $(-{\Delta})^s_pu$ is replaced by any non-local integro-differential operator.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1722-1725
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• 2003

절연물에 가해지는 열화 중에서 열 사이클(Thermal cycle) 열화를 모사하기 위하여, 대형 터빈 발전기 수냉각 고정자 권선용 바를 대상으로 IEEE Std 1310 규격에 따라 200 사이클의 열 사이클 열화 시험을 수행하였다. 바에 대한 절연 특성을 분석하기 위하여 시험 수행 전후의 Tan ${\delta}$ 및 Tip-up(%, ${\Delta}$ Tan ${\delta}$), 부분방전의 최대 방전량 등을 측정하였고 또한 바를 절단하여 절연물 내의 박리와 도체와 절연물 간의 분리 등을 점검하였다. 최종적으로는 절연파괴 시험을 수행하여 절연파괴 강도를 측정하였다. 시험 결과 초기 절연 특성상의 현저한 변화는 없었으며 양호한 특성을 보였다.

• 대한수학회보
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• 제56권1호
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• pp.245-251
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• 2019

Assume that ${\Omega}$ is a bounded domain in ${\mathbb{R}}^n$ with $n{\geq}2$. We study positive solutions to the problem, ${\Delta}u=u^p$ in ${\Omega}$, $u(x){\rightarrow}{\infty}$ as $x{\rightarrow}{\partial}{\Omega}$, where p > 1. Such solutions are called boundary blow-up solutions of ${\Delta}u=u^p$. We show that a boundary blow-up solution exists in any bounded domain if 1 < p < ${\frac{n}{n-2}}$. In particular, when n = 2, there exists a boundary blow-up solution to ${\Delta}u=u^p$ for all $p{\in}(1,{\infty})$. We also prove the uniqueness under the additional assumption that the domain satisfies the condition ${\partial}{\Omega}={\partial}{\bar{\Omega}}$.

• 열처리공학회지
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• 제7권1호
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• pp.17-24
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• 1994

The evaluation and analysis of diffusivity of lithium for coarsening and coarsening kinetics of ${\delta}^{\prime}$ precipitate in Al-Li-Cu-Mg-Zr alloy aged at $170^{\circ}C$ have been investigated by transmission electron microscopy. With ageing time, ${\delta}^{\prime}$ precipitate coaesened to followed $\bar{\gamma}{\propto}t^{1/3}$ and coarsening kinetics was found to be obeyed to the Lifshitz-Slyozov-Wagner(LSW) theory and diffusivity of lithium for coarsening of ${\delta}^{\prime}$ precipitate in Al-Li-Cu-Mg-Zr alloy was obtained to be $5.85{\times}10^{-17}{\sim}1.53{\times}10^{-16}$ by experimental coarsening rate constant and various coarsening kinetic theory. Diffusivity of lithium measured by using various model but MLSW and Tsumuraya (VI) et al. model in Al-Li-Cu-Mg-Zr alloy is similar to that calculated by the Costas's diffusivity equation. It was, therefore, suggested that additing to the Cu, Mg and Zr element in Al-Li system have no great effect on diiffusivity of lithium for coarsening of ${\delta}^{\prime}$ This suggest that in matrix.