• Journal of the Korean Mathematical Society
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• v.41 no.4
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• pp.717-735
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• 2004

A problem raised by Selfridge and solved by Pomerance asks to find the pairs (a, b) of natural numbers for which $2^a\;-\;2^b$ divides $n^a\;-\;n^b$ for all integers n. Vajaitu and one of the authors have obtained a generalization which concerns elements ${\alpha}_1,\;{\cdots},\;{{\alpha}_{\kappa}}\;and\;{\beta}$ in the ring of integers A of a number field for which ${\Sigma{\kappa}{i=1}}{\alpha}_i{\beta}^{{\alpha}i}\;divides\;{\Sigma{\kappa}{i=1}}{\alpha}_i{z^{{\alpha}i}}\;for\;any\;z\;{\in}\;A$. Here we obtain a further generalization, proving the corresponding finiteness results in a multidimensional setting.

• Bulletin of the Korean Mathematical Society
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• v.51 no.6
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• pp.1829-1839
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• 2014

Let (${\Omega}$, $\mathcal{S}$, ${\mu}$) be a probabilistic measure space, ${\varepsilon}{\in}\mathbb{R}$, ${\delta}{\geq}0$, p > 0 be given numbers and let $P{\subset}\mathbb{R}$ be an open interval. We consider a class of functions $f:P{\rightarrow}\mathbb{R}$, satisfying the inequality $$f(EX){\leq}E(f{\circ}X)+{\varepsilon}E({\mid}X-EX{\mid}^p)+{\delta}$$ for each $\mathcal{S}$-measurable simple function $X:{\Omega}{\rightarrow}P$. We show that if additionally the set of values of ${\mu}$ is equal to [0, 1] then $f:P{\rightarrow}\mathbb{R}$ satisfies the above condition if and only if $$f(tx+(1-t)y){\leq}tf(x)+(1-t)f(y)+{\varepsilon}[(1-t)^pt+t^p(1-t)]{\mid}x-y{\mid}^p+{\delta}$$ for $x,y{\in}P$, $t{\in}[0,1]$. We also prove some basic properties of such functions, e.g. the existence of subdifferentials, Hermite-Hadamard inequality.

• Kyungpook Mathematical Journal
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• v.50 no.1
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• pp.59-69
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• 2010

The main aim of this article is to introduce a new class of sequence spaces using the concept of n-norm and to investigate these spaces for some linear topological structures as well as examine these spaces with respect to derived (n-1)-norm. We use an Orlicz function, a bounded sequence of positive real numbers and some difference operators to construct these spaces so that they become more generalized and some other spaces can be derived under special cases. These investigations will enhance the acceptability of the notion of n-norm by giving a way to construct different sequence spaces with elements in n-normed spaces.

• Journal of the Korean Home Economics Association
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• v.19 no.3
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• pp.1-9
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• 1981

The object of this study lies in reviewing of the western costume history in the light of the negative regulations concerning costumes and adornments. Readings related with the subject lead to the following findings; 1. the principal purpose of the sumptuary laws has relationship with the social stratification of the feudalism and the frequency of their occurrence is related with the formation of feudal system, its decline, the appearance of imperial regimes and the start of civil revolutions. 2. Sumptuary regulations spread westward with the flow of civilization, eg., in the sequence of Italy, swiss, France, Britain and new world. 3. Sumptuary laws are also found in abundance in the english colonies of America, and their object seems to be rather of the moral concern than class distinction of economical restriction.4. The reviewed sumptuary regulations are concerned with : A. Material gold or silver clothes, silks, ermine, marten or miniver furs, velvets, laces and embroies. B. Colors-Purple, scarlet and red. Other colors do not show consistent pattern of color-status symbol; C. Form-Length and width of headdresses, shoes, collars, trains or hoops. E. numbers of dresses allowed to be worn.

• Journal of the Korean Data and Information Science Society
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• v.21 no.3
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• pp.481-491
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• 2010

In this paper, we made a program to compare between population parameters and sample statistics, via Excel macro. This program gathers each students’ files to one file, from which a sample is drawn. This program will help students to be interested in class through extracting a part of sample from a group and comparing the difference between parameters and statistics in a few seconds. In Excel, overlapping value could happen when random numbers are generated but we avoid this case by making the sub-program, without replacement with VBA.

• Journal of the Korean Mathematical Society
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• v.44 no.3
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• pp.499-509
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• 2007

Let m, n be positive integers or monic polynomials in $\mathbb{F}_q[T]$ with n|m. Let $K_m\;and\;K^+_m$ be the m-th cyclotomic field and its maximal real subfield, respectively. In this paper we define two matrices $D^+_{m,n}\;and\;D^-_{m,n}$ whose determinants give us the ratios $\frac{h(\mathcal{O}_{K^+_m})}{h(\mathcal{O}_{K^+_n})}$ and $\frac{h-(\mathcal{O}_K_m)}{h-(\mathcal{O}_K_n)}$ with some factors, respectively.

• Journal of the Korean Mathematical Society
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• v.54 no.6
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• pp.1801-1816
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• 2017

We study some spectral properties of Volterra-type integral operators $V_g$ and $I_g$ with holomorphic symbol g on the Fock-Sobolev spaces ${\mathcal{F}}^p_{{\psi}m}$. We showed that $V_g$ is bounded on ${\mathcal{F}}^p_{{\psi}m}$ if and only if g is a complex polynomial of degree not exceeding two, while compactness of $V_g$ is described by degree of g being not bigger than one. We also identified all those positive numbers p for which the operator $V_g$ belongs to the Schatten $S_p$ classes. Finally, we characterize the spectrum of $V_g$ in terms of a closed disk of radius twice the coefficient of the highest degree term in a polynomial expansion of g.

• 한국항공운항학회:학술대회논문집
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• 2015.11a
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• pp.237-241
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• 2015

After it first opened in 2001, Incheon International Airport (IIA) has grown into a world-class airport, leaving remarkable traces, such as being the first airport to win the ASQ Airport Serivce Price for 10 consecutive years. However, ever since its birth IIA has tried to position itself as the leading hub airport of Northeast Asia. Until this day, it has not been meeting this goal, with transfer passenger numbers and transfer rates decreasing recently. This study looks at the outer environment to discover which factors affect IIA's transfer market. Through extensive research on external analysis, the study will eventually provide a counter strategy guideline for fighting back against decreasing transfer usage.

• Honam Mathematical Journal
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• v.37 no.3
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• pp.339-352
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• 2015

We aim at giving explicit expressions of $${\sum_{m,n=0}^{{\infty}}}{\frac{{\Delta}_{m+n}(-1)^nx^{m+n}}{({\rho})_m({\rho}+i)_nm!n!}$$, where i = 0, ${\pm}1$, ${\ldots}$, ${\pm}9$ and $\{{\Delta}_n\}$ is a bounded sequence of complex numbers. The main result is derived with the help of the generalized Kummer's summation theorem for the series $_2F_1$ obtained earlier by Choi. Further some special cases of the main result considered here are shown to include the results obtained earlier by Kim and Rathie and the identity due to Bailey.

• Korean Journal of Childcare and Education
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• v.14 no.5
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• pp.85-99
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• 2018

Objective: This purpose of this study was to analyze articles and research trends in children's free-choice activities in major domestic journals published from 1998 to 2017. Methods: Registered research papers in academic journals from 1998 to 2017 for the National Research Foundation of Korea were analyzed in terms of trends in their annual submission numbers, research subject, research type, research area. and research theme. Results: The quantity of the studies has more than doubled since 2010 but has decreased in recent years. Studies about free-choice activities for young children held the majority of research subjects while physical subjects such as literature, class, and education plans were in the minority. Furthermore, qualitative research, fusion qualitative, and survey were the most common research types while literature review studies were less common. Most research themes were studies about contemplation, actual conditions and perception, factor analysis, and programs of free-choice activities for young children. Conclusion/Implications: Considering the results of this study, further studies on free-choice activities for young children must be conducted.