• 대한수학회지
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• 제59권4호
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• pp.685-697
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• 2022

Recently, Gireesh, Shivashankar, and Naika [11] found some infinite classes of congruences for the 3- and the 9-regular cubic partitions modulo powers of 3. We extend their study to all the 3^k-regular cubic partitions. We also find new families of congruences.

• 대한수학회지
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• 제56권1호
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• pp.169-181
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• 2019

In [9], Geramita, Harbourne, and Migliore find a graded minimal free resolution of the 2nd order symbolic power of the ideal of a linear star configuration in ${\mathbb{P}}^n$ n of any codimension r. In [8], Geramita, Galetto, Shin, and Van Tuyl extend the result on a general star configuration in ${\mathbb{P}}^n$ but for codimension 2. In this paper, we find a graded minimal free resolution of the 2nd order symbolic power of the ideal of a general star configuration in ${\mathbb{P}}^n$ of any codimension r using a matroid configuration in [10]. This generalizes both the result on a linear star configuration in ${\mathbb{P}}^n$ of codimension r in [9] and the result on a general star configuration in ${\mathbb{P}}^n$ of codimension 2 in [8].

• 대한수학회지
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• 제58권2호
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• pp.283-308
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• 2021

In [30] the author finds a graded minimal free resolution of the 2-nd order symbolic power of a star configuration in ℙn of any codimension r. In this paper, we find that of any m-th order symbolic power of a star configuration in ℙn of codimension 2, which generalizes the result of Galetto, Geramita, Shin, and Van Tuyl in [15, Theorem 5.3]. Furthermore, we extend it to the m-th order symbolic power of a star configuration in ℙn of any codimension r for m = 3, 4, which also generalizes the result of Biermann et al. in [1, Corollaries 4.6 and 5.7]. We also suggest how to find a graded minimal free resolution of the m-th order symbolic power of a star configuration in ℙn of any codimension r for m ≥ 5.

• 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.

• 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.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제25권1호
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• pp.31-38
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• 2018

In [4], the authors show that if ${\mathbb{X}}$ is a ${\mathbb{k}}-configuration$ in ${\mathbb{P}}^2$ of type ($d_1$, ${\ldots}$, $d_s$) with $d_s$ > $s{\geq}2$, then ${\Delta}H_{m{\mathbb{X}}}(md_s-1)$ is the number of lines containing exactly $d_s-points$ of ${\mathbb{X}}$ for $m{\geq}2$. They also show that if ${\mathbb{X}}$ is a ${\mathbb{k}}-configuration$ in ${\mathbb{P}}^2$ of type (1, 2, ${\ldots}$, s) with $s{\geq}2$, then ${\Delta}H_{m{\mathbb{X}}}(m{\mathbb{X}}-1)$ is the number of lines containing exactly s-points in ${\mathbb{X}}$ for $m{\geq}s+1$. In this paper, we explore a standard ${\mathbb{k}}-configuration$ in ${\mathbb{P}}^2$ and find that if ${\mathbb{X}}$ is a standard ${\mathbb{k}}-configuration$ in ${\mathbb{P}}^2$ of type (1, 2, ${\ldots}$, s) with $s{\geq}2$, then ${\Delta}H_{m{\mathbb{X}}}(m{\mathbb{X}}-1)=3$, which is the number of lines containing exactly s-points in ${\mathbb{X}}$ for $m{\geq}2$ instead of $m{\geq}s+1$.

• 전기학회논문지
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• 제59권2호
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• pp.285-290
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• 2010

We investigate the outage probability in terms of QoS (quality of service) in indoor PLC network. We consider various kinds of appliances for realistic indoor PLC network. For estimation of the outage probability, we calculate the time-varying channel responses considering the loading conditions based on regular human activities and include the additive noise. We calculate the outage probability for each terminal and investigate relationship between the outage probability and the channel length, and transmit powers. Our results suggest that the outage probability is increased when the channel length becomes longer because more appliances affect the amount of reduced channel capacity and is not improved distinctly for very high and low outage threshold by increasing the transmit power. However, we can see outage probability improvement for 30% outage threshold case by increasing the transmit power.

• Journal of Electrical Engineering and Technology
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• 제8권2호
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• pp.271-281
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• 2013

In order to improve the performance of analysis, it is important to consider the nonlinearity in power system. The Carleman embedding technique (linearization procedure) provides an effective approach in reduction of nonlinear systems. In the approach, a group of differential equations in which the state variables are formed by the original state variables and the vector monomials one can build with products of positive integer powers of them, is constructed. In traditional Carleman linearization technique, the tensor matrix is truncated to form a square matrix, and then regular linear system theory is used to solve the truncated system directly. However, it is found that part of nonlinear information is neglected when truncating the Carleman model. This paper proposes a new approach to solve the problem, by combining the Poincar$\acute{e}$ transformation with the Carleman linearization. Case studies are presented to verify the proposed method. Modal analysis shows that, with traditional Carleman linearization, the calculated contribution factors are not symmetrical, while such problems are avoided in the improved approach.

• 한국산학기술학회논문지
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• 제10권4호
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• pp.707-716
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• 2009

본 연구는 일부 소방직공무원들의 스트레스 및 피로 수준을 파악하고, 스트레스와 피로에 관련된 요인을 구명하고자 청주시의 소방공무원 262명을 대상으로 구조화된 무기명 자기기입식 설문지(self-administrated questionnaire)를 이용한 설문조사를 실시하였다. 연구결과 전체 조사대상 소방공무원들의 사회심리적 스트레스 수준은 잠재적 스트레스군이 12.2%, 고위험스트레스군이 87.5%이었으며, 건강군은 한 명도 없었다 피로수준은 중앙값을 기준으로 구분하였을 경우, 낮은 군이 51.1%, 높은 군이 48.9%를 차지하였다. 단계별 다변량 회귀분석 결과 사회심리적 스트레스에 영향을 미치는 요인으로는 주관적인 건강상태, 직장생활만족도, 직무요구도, 음주상태 등이 선정되었으며, 피로수준에 영향을 미치는 요인으로는 주관적 건강상태, 규칙적인 운동여부 등이 선정되었다. 이상의 연구결과는 소방공무원의 사회심리학적 스트레스나 피로수준이 대단히 높은 것을 시사하며 여러 요인들이 관여하고 있음을 알 수 있다. 따라서 소방공무원들의 스트레스나 피로를 감소시키기기 위한 건강증진프로그램의 개발 및 시행이 필요할 것으로 생각된다.

• 한국산학기술학회논문지
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• 제12권10호
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• pp.4493-4501
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• 2011

본 연구는 장기요양보험급여를 받고 있는 노인들의 장기요양등급에 따른 인지기능상태를 파악해 보고, 인지 기능에 영향을 미치는 관련요인을 규명해 보고자 시도하였다. 조사는 충청남도 9개 군의 농촌지역에서 장기요양보험 급여를 받고 있는 노인 410명을 대상으로 2009년 3월 1일부터 5월 31일까지의 기간 동안에 표준화된 무기명식 면접조사용 설문지를 사용하여 면접조사 하였다. 연구결과, MMSE-K를 사용하여 측정한 전체 조사대상자의 인지기능상태는 확정적 인지기능장애(19점 이하)가 80.5%, 인지기능장애 의심(20~23점)이 11.7%, 확정적 정상(24점 이상)이 7.8%로 나타났다. 조상대상자의 인지기능은 장기요양등급이 높을수록 유의하게 낮은 것으로 나타났으며, 교육정도가 낮을수록, 직업이 없는 군, 혼자 산다는 군, 월수입이 낮은 군, 생활비를 자녀가 조달하거나 정부의 보조를 받는다는 군, 귀의 부자유가 있다는 군, 요실금이 있다는 군, 건망증이 있다는 군, 규칙적인 운동을 하지 않는다는 군, 외출을 거의 하지 않는다는 군에서 유의하게 낮았다. 조사대상자의 인지기능에 영향을 미치는 요인으로는 연령, 생활비 조달원, 눈의 부자유 유무, 요실금유무, 건망증유무, 규칙적인 운동 여부 및 장기요양등급이 유의한 변수로 선정되었으며, 특히 건강상태를 나타내는 변수들이 인지기능과 높은 관련성이 있었다.