• Journal of the Korean Statistical Society
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• 제27권1호
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• pp.57-66
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• 1998

In the analysis of time series it is an important issue to determine whether a time series under study is stationary. For the test of the stationary of the time series the Dickey-Fuller (DF) type tests have been mainly used. In this paper, we consider the regular unit root tests and seasonal unit root tests based on the generalized Durbin-Watson (DW) statistics when the errors are independent. The limiting distributions of the proposed DW-type test statistics are the functionals of standard Brownian motions. We also obtain the finite distributions and powers of the DW-type test statistics and compare the performances with the DF-type tests. It is observed that the DW-type test statistics have good behaviors against the DF-type test statistics especially in the nonzero (seasonal) mean model.

• 대한수학회지
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• 제44권4호
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• pp.903-913
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• 2007

A ring R has weakly stable range one provided that aR+bR=R implies that there exists a $y{\in}R$ such that $a+by{\in}R$ is right or left invertible. We prove, in this paper, that every regular element in an exchange ring having weakly stable range one is the sum of an idempotent and a weak unit. This generalize the corresponding result of one-sided unit-regular ring. Extensions of power comparability and power cancellation are also studied.

• Communications for Statistical Applications and Methods
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• 제4권3호
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• pp.663-676
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• 1997

We obtain the simultaneous unit roots test statistics for both regular and seasonal unit roots in a time series with possible seasonal deterministic trends. The limiting distributions of the proposed test statistics are derived and empirical percentiles of the test statistics are tabulated for some seasonal periods. The power and size of the test statistics are examined for finite samples through a Monte Carlo simulation and Compared with those of the Lagrange multiplier test.

• Journal of the Korean Statistical Society
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• 제30권4호
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• pp.597-612
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• 2001

We have developed a \

• 대한수학회지
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• 제54권1호
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• pp.177-191
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• 2017

In this note we consider the right unit-duo ring property on the powers of elements, and introduce the concept of weakly right unit-duo ring. We investigate first the properties of weakly right unit-duo rings which are useful to the study of related studies. We observe next various kinds of relations and examples of weakly right unit-duo rings which do roles in ring theory.

• 대한수학회보
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• 제55권5호
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• pp.1333-1338
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• 2018

A ${\ast}-ring$ R is called ${\ast}-regular$ if every principal one-sided ideal of R is generated by a projection. In this note, several characterizations of ${\ast}-regular$ rings are provided. In particular, it is shown that a matrix ring $M_n(R)$ is ${\ast}-regular$ if and only if R is regular and $1+x^*_1x_1+{\cdots}+x^*_{n-1}x_{n-1}$ is a unit for all $x_i$ of R; which answers a question raised in the literature recently.

• 대한수학회논문집
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• 제36권4호
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• pp.651-669
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• 2021

In this paper, we investigate some basic results on the slice regular Besov spaces of hyperholomorphic functions on the unit ball 𝔹. We also characterize the boundedness, compactness and find the essential norm estimates for composition operators between these spaces.

• Communications for Statistical Applications and Methods
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• 제2권2호
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• pp.101-114
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• 1995

In this paper we consider the multiple unit root tests both for the regular and seasonal unit roots based on the Lagrange Multiplier(LM) principle. Unlike Li(1991)'s method, by plugging the restricted maximum likelihood estimates of the nuisance parameters in the model, we propose a Lagrange multiplier test which does not depend on the existence of the nuisance parameters. The asymptotic distribution of the proposed statistic is derived and empirical percentiles of the test statistic for selected seasonal periods are provided. The power and size of the test statistic for examined for finite samples through a Monte Carlo simularion.

• 한국주거학회논문집
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• 제19권6호
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• pp.21-32
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• 2008

The purpose of this research is firstly to derive regular sizes of average dwellings in Korea and to examine minimum living standards in light of those regular dwellings in order to meet future housing requirements of low income households. Two plan types of unit floor area 60 $m^2$ and 85 $m^2$ have become prevalent and ubiquitous so as to reflect the basic requirements of ordinary living standards. Thus, dimensional characteristics of each space in those two plan types is thoroughly investigated in this research. The background of regular plans and their popularized process is first reviewed and the 120 cases of apartment units which were constructed between 2000 and 2007, are selected from those three regional groups and surveyed in detail. The area, depth, width and proportion of each space of unit plans are compared and analyzed in various aspects. As a result, proper space sizes and standards for low income households are reviewed and compared. The regional difference of space dimensions is not significant as expected but area and size characteristics of each space is very much regularized and obvious. And it is argued that those dimensional characteristics should convey the social and cultural values of Korean housing. The average dimensions of each spaces of surveyed apartment unit turns out to be much closer to guidable living standards rather than minimum living standards. Thus, it is very probable that the present guidable living standards could be upgraded to become the future minimum living standards soon.

• Korean Journal of Mathematics
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• 제28권1호
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• pp.149-157
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• 2020

Some basic properties in connection with generalized relative order and generalized relative lower order of analytic functions in the unit disc have been dicussed in this article.