• 대한수학회보
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• 제48권2호
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• pp.247-260
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• 2011

Let h be a meromorphic function with few poles and zeros. By Nevanlinna's value distribution theory we prove some new properties on the polynomials in h with the coefficients being small functions of h. We prove that if f is a meromorphic function and if $f^m$ is identically a polynomial in h with the constant term not vanish identically, then f is a polynomial in h. As an application, we are able to find the entire solutions of the differential equation of the type $$f^n+P(f)=be^{sz}+Q(e^z)$$, where P(f) is a differential polynomial in f of degree at most n-1, and Q($e^z$) is a polynomial in $e^z$ of degree k $\leqslant$ max {n-1, s(n-1)/n} with small functions of $e^z$ as its coefficients.

• Journal of Forest and Environmental Science
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• 제11권1호
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• pp.72-80
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• 1995

강원대학교 부속 연습림의 낙엽활엽수림에서 임상유기물(O층)의 집적에 미치는 표고의 영향을 조사하였다. 표고가 높아짐에 따라 O층의 두께는 증가하였으며, 이러한 경향은 F2층과 H층에서 뚜렷하였다. O층의 두께(X, cm)와 무게(Y, $kg/m^2$)의 관계는 직선회귀식 Y($kg/m^2$) = aX(cm)에 근사였으며, F2층, H층 및 F2 + H층에 대한 계수 "a" 의 값은 각각 0.43, 0.61 및 0.53이었다. 유기물의 용적중은 F2층, H층 및 F2+H층에서 각각 $45g/dm^2$, $60g/dm^2$ 및 $55g/dm^2$ 전후로 추정되었다. O층의 양은 표고 280m에서의 13ton/ha으로부터 표고 710m의 41ton/ha의 범위에 있었으며, F1, F2및 H층은 각각 5~10ton/ha, 5~11ton/ha 및 13~40ton/ha의 범위를 차지하였다.

• 한국자원식물학회지
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• 제29권4호
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• pp.407-418
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• 2016

본 연구는 ITS region과 3개의 엽록체 DNA region을 활용하여 한국산 수국속 7 분류군에 대한 계통학적 유연관계를 규명하고자 수행되었다. 계통학적 분석 결과 한국산 수국속의 7분류군은 단계통군을 형성하였으며, Macrophyllae 아절은 산수국과 수국의 두 개의 분계조로 나뉘었다. 산수국의 분계조는 꽃산수국과 탐라산수국이 유집되어 하나의 단계통군을 형성하였으며, 염기서열상으로도 뚜렷한 차이가 나타나지 않았다. 수국의 분계조는 산수국의 분계조와 독립된 분계조를 형성하며 뚜렷이 구분되었다. 수국속 분계조 내의 Petalanthe, Heteromallae, Calyptranthae 아절은 단계통군을 형성하였지만, Calyptranthae 아절에 속하는 등수국은 한라산 개체를 제외한 제주도 집단과 울릉도, 일본 집단으로 두 개의 소분계조를 이루었다. 등수국의 두 개의 소분계조에 대한 추가적인 연구는 더 많은 양의 채집과 지리학적인 연구가 추가 되어야 할 것으로 판단된다.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제14권4호
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• pp.289-306
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• 2007

We define and study a concept of $H^f-space$ for a map, which is a generalized concept of an H-space, in terms of the Gottlieb set for a map. For a principal fibration $E_{\kappa}{\rightarrow}X$ induced by ${\kappa}:X{\rightarrow}X'\;from\;{\epsilon}:\;PX'{\rightarrow}X'$, we can obtain a sufficient condition to having an $H^{\bar{f}}-structure\;on\;E_{\kappa}$, which is a generalization of Stasheff's result [17]. Also, we define and study a concept of $co-H^g-space$ for a map, which is a dual concept of $H^f-space$ for a map. Also, we get a dual result which is a generalization of Hilton, Mislin and Roitberg's result [6].

• Korean Journal of Mathematics
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• 제8권2호
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• pp.187-191
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• 2000

In the present paper we shall first introduce the timewidth of a signal, and then we shall investigate the relation between the timewidths of a signal $f$ and of the convolution $f*h$ for some other signal $h$.

• 충청수학회지
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• 제27권4호
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• pp.735-743
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• 2014

We obtain a splitting theorem which characterizes when a given space is a catesian product of an $H^f$-space, and also obtain a dual theorem for a co-$H^g$-space. Then we get Dula and Gottlieb's results as corollaries.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 춘계학술발표회요약집
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• pp.388.1-388
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• 2001

• 한국수소및신에너지학회논문집
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• 제28권2호
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• pp.137-143
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• 2017

In the present study, Ni and $TaF_5$ were chosen as additives to enhance the hydriding and dehydriding rates of Mg. A sample with a composition of 80 wt% Mg + 14 wt% Ni + 6 wt% $TaF_5$ (named $80Mg+14Ni+6TaF_5$) was prepared by high-energy ball milling in hydrogen. Its hydriding and dehydriding properties were then examined. At the fourth cycle, the activated sample absorbed 3.88 wt% H for 2.5 min, 4.74 wt% H for 5 min, and 5.75 wt% H for 60 min at 593 K under 12 bar $H_2$. $80Mg+14Ni+6TaF_5$ had an effective hydrogen-storage capacity (the quantity of hydrogen absorbed for 60 min) of about 5.8 wt%. The sample desorbed 1.42 wt% H for 5 min, 3.42 wt% H for 15 min, and 5.09 wt% H for 60 min at 593 K under 1.0 bar $H_2$. Line scanning results by EDS for $80Mg+14Ni+6TaF_5$ before and after cycling showed that the peaks of Ta and F appeared at different positions, indicating that the $TaF_5$ in $80Mg+14Ni+6TaF_5$ was decomposed.

• 대한수학회지
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• 제43권2호
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• pp.311-322
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• 2006

For the Briot-Bouquet differential equations of the form given in [1] $${{\mu}(z)+\frac {z{\mu}'(z)}{z\frac {f'(z)}{f(z)}\[\alpha{\mu}(z)+\beta]}=g(z)$$ we can reduce them to $${{\mu}(z)+F(z)\frac {v'(z)}{v(z)}=h(z)$$ where $$v(z)=\alpha{\mu}(z)+\beta,\;h(z)={\alpha}g(z)+\beta\;and\;F(z)=f(z)/f'(z)$$. In this paper we are going to give conditions in order that if u and v satisfy, respectively, the equations (1) $${{\mu}(z)+F(z)\frac {v'(z)}{v(z)}=h(z)$$, $${{\mu}(z)+G(z)\frac {v'(z)}{v(z)}=g(z)$$ with certain conditions on the functions F and G applying the concept of strong subordination $g\;\prec\;\prec\;h$ given in [2] by the author, implies that $v\;\prec\;{\mu},\;where\;\prec$ indicates subordination.

• 한국재료학회지
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• 제23권10호
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• pp.562-567
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• 2013

A 90 wt% Mg-10 wt% $NbF_5$ sample was prepared by mechanical milling under $H_2$ (reactive mechanical grinding). Its hydriding and dehydriding properties were then examined. Activation of the 90 wt% Mg-10 wt% $NbF_5$ sample was not required. At n=1, the sample absorbed 3.11 wt% H for 2.5 min, 3.55 wt% H for 5 min, 3.86 wt% H for 10 min, and 4.23 wt% H for 30 min at 593K under 12 bar $H_2$. At n=1, the sample desorbed 0.17 wt% H for 5 min, 0.74 wt% H for 10 min, 2.03 wt% H for 30 min, and 2.81 wt% H for 60 min at 593K under 1.0 bar $H_2$. The XRD pattern of the 90 wt% Mg-10 wt% $NbF_5$ after reactive mechanical grinding showed Mg, ${\beta}-MgH_2$ and small amounts of ${\gamma}-MgH_2$, $NbH_2$, $MgF_2$ and $NbF_3$. The XRD pattern of the 90 wt% Mg-10 wt% $NbF_5$ dehydrided at n=3 revealed Mg, ${\beta}-MgH_2$, a small amount of MgO and very small amounts of $MgH_2$ and $NbH_2$. The 90 wt% Mg-10 wt% $NbF_5$ had a higher initial hydriding rate and a larger quantity of hydrogen absorbed for 60 min than the 90 wt% Mg-10 wt% MnO and the 90 wt% Mg-10 wt% $Fe_2O_3$, which were reported to have quite high hydriding rates and/or dehydriding rates. The 90 wt% Mg-10 wt% $NbF_5$ had a higher initial dehydriding rate (after an incubation period) and a larger quantity of hydrogen desorbed for 60 min than the 90 wt% Mg-10 wt% MnO and the 90 wt% Mg-10 wt% $Fe_2O_3$.