• 대한수학회보
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• 제41권1호
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• pp.125-135
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• 2004

One of the intriguing and fundamental algorithmic graph problems is the computation of the strongly connected components of a directed graph G. In this paper we first introduce a simple procedure for determining the location of the nonzero elements occurring in $B^{-1}$ without fully inverting B, where EB\;{\equiv}\;(b_{ij)\;and\;B^T$ are diagonally dominant matrices with $b_{ii}\;>\;0$ for all i and $b_{ij}\;{\leq}\;0$, for $i\;{\neq}\;j$, and then, as an application, show that all of the strongly connected components of a directed graph G can be recognized by the location of the nonzero elements occurring in the matrix $C(G)\;=\;(D\;-\;A(G))^{-1}$. Here A(G) is an adjacency matrix of G and D is an arbitrary scalar matrix such that (D - A(G)) becomes a diagonally dominant matrix.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.216-220
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• 1989

Direct calculation algorithm for the elements of A matrix is suggested for a single machine connected to the infinite bus. Excitation system and power system stabilizer are included. When A matrix is partitioned into seven submatrices, we can identify the location of non-zero elements and formula for each element. No matrix inversion and multiplication are necessary.

• 대한수학회지
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• 제57권4호
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• pp.973-986
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• 2020

In this paper, we compute the Hankel matrix representation of the Hankel operator on the Hardy space of a general bounded domain with respect to special orthonormal bases for the Hardy space and its orthogonal complement. Moreover we obtain the compact form of the Hankel matrix for the unit disc case with respect to these bases. One can see that the Hankel matrix generated by this computation turns out to be a generalization of the case of the unit disc from the single simply connected domain to multiply connected domains with much diversities of bases.

• 대한수학회논문집
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• 제15권4호
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• pp.587-595
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• 2000

We contain a simple construction for the sparse n x n connected orthogonal matrices which have a row of p nonzero entries with 2$\leq$p$\leq$n. Moreover, we study the analogous sparsity problem for an m x n connected row-orthogonal matrices.

• 한국정보통신학회논문지
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• 제22권11호
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• pp.1538-1543
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• 2018

원 상에 n개의 점들의 쌍 (a,b)이 존재할 때, 두 점 a와 b를 연결하는 직선 선분을 코드라고 한다. 이러한 n개의 코드들은 새로운 그래프 G를 정의한다. 각 코드는 G의 한 정점을 정의하고 두 코드가 교차하는 경우에 대응되는 정점들 간에 간선을 연결한다. 이렇게 만들어진 그래프 G를 원 그래프라고 부른다. 본 논문에서는 원 그래프에서 연결 요소를 찾는 문제를 다룬다. 연결 요소란 그래프 G의 부분 그래프 H로서 H안의 임의의 두 정점 간에 경로가 존재한다는 조건을 만족하는 최대 부분 그래프이다. 그래프 G가 인접 행렬로 주어지는 경우, 연결 요소를 찾는 문제는 깊이 우선 탐색 또는 너비 우선 탐색을 통해서 해결할 수 있다. 하지만 원 그래프의 경우에 코드들을 정의하는 n개의 점들의 쌍 정보만 입력으로 주어질 때, 인접 행렬을 구하는데 ${\Omega}(n^2)$ 시간이 소요됨을 알 수 있다. 본 논문에서는 인접 행렬을 만들지 않고 원 그래프의 연결 요소를 $O(n{\log}^2n)$시간에 찾는 알고리즘을 고안한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2020년도 전력전자학술대회
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• pp.381-382
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• 2020

In the battery energy storage system, battery cells are connected in series to increase the operating voltage. Due to the difference in characteristics, the performance degradation of cells is dissimilar. This paper proposes an online DC internal impedance estimation for battery cells in the series string using a matrix-switched capacitor converter, which is already verified as useful for the series balancing of the cells. The simulation in the hardware in the loop test rig shows good accuracy and the feasibility of the proposed method.

• 전력전자학회논문지
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• 제19권6호
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• pp.538-548
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• 2014

This study provides a robust control of a grid-connected three-phase two-level photo voltaic inverter. The introduced control method uses the cascade control strategy to regulate AC-side current and DC-link voltage. A robust controller with integration action is used for the inner-loop AC-side current control, which maximizes the convergence rate using a linear matrix inequality-based optimization design method and eliminates the offset error. The robust controller design method considers the parameter uncertainty set to accommodate parameter mismatch and un-modeled components in the inverter model. An outer-loop proportional-integral controller is used to regulate DC-link voltage with linearization of DC/AC relation. The proposed control strategy is applied to a grid-connected 100 kW photo voltaic inverter.

• Korean Journal of Mathematics
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• 제14권1호
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• pp.47-55
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• 2006

This paper presents an image analysis technique using connected components by applying SPA (shortest path algorithm) from graph theory. Software implementation of Floyd-Warshall transitive matrix labelling method is discussed. Results are also presented.

• 통합자연과학논문집
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• 제10권2호
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• pp.110-114
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• 2017

The connected and simply connected four-dimensional matrix solvable Lie group $Sol^4_1$ is the four-dimensional geometry. A crystallographic group of $Sol^4_1$ is a discrete cocompact subgroup of $Sol^4_1{\rtimes}D(4)$. In this paper, we geometrically describe the crystallographic groups of $Sol^4_1$.

• 대한수학회논문집
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• 제34권4호
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• pp.1135-1143
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• 2019

The matrix representation of the Toeplitz operator on the Hardy space with respect to a generalized orthonormal basis for the space of square integrable functions associated to a bounded simply connected region in the complex plane is completely computed in terms of only the Szegő kernel and the Garabedian kernels.