• 한국음향학회지
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• 제27권1호
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• pp.40-46
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• 2008

천해 영역에서 선박과 같은 수상 소음원의 간섭 신호는 정합장처리를 이용한 수중 표적 탐지 및 위치추정 기법 적용에 있어 문제점으로 남아있다. 정지 음원의 경우 수신기공간의 음장에 대한 고유벡터분해를 통해 각 음원 성분을 분리하고 간섭 신호 성분을 제거할 수 있다. 하지만 일반적인 이동 음원 환경에서는 각 신호 성분의 에너지가 수신 음장의 부분공간에 퍼지게 되므로, 고유값 분포 비교만으로 각 신호 성분을 구별하기 어렵게 되거나 하나의 고유벡터에 각 신호성분이 섞이는 경우도 발생한다. 본 논문에서는 수상 음원과 수중 음원 신호의 물리적 특성 차이를 이용한 모드공간 간섭 신호 제거 기법을 제안하였다. 이 기법은 모드-공분산행렬에 대한 고유벡터분해를 통해 간섭 신호 성분을 판별하며, 이 성분들을 부분공간에서 제거함으로써 차폐되었던 표적 신호를 복원하고 위치추정을 가능하게 한다. 이를 모의실험을 통해 확인하고 결과에 대해 논의하였다.

• 한국산학기술학회논문지
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• 제10권5호
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• pp.972-978
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• 2009

본 논문은 색 일관성을 달성하기 위해 $\chi$-색도 공간에서 고유벡터를 이용하여 본질 영상의 획득에 중대한 영향을 미치는 불변 방향을 검출하는 알고리즘을 제안한다. 이를 위해, 우선 영상을 Finlayson 등이 제안한 방법을 활용하여 $\chi$-색도 공간으로 변환한다. 두 번째로, 불변 방향에 영향을 줄 수 있는 잡음 같은 낮은 빈도를 갖는 데이터들을 제거한다. 세 번째로, 주축 방향과 일치하는 불변 방향을 검출하기 위해, 위 단계에서 추출된 데이터들로부터 가장 큰 고유값에 해당하는 고유벡터를 계산한다. 마지막으로, 검출된 불변 방향을 사용하여 복원함으로써, 본질 영상을 획득한다. 실험 영상은 Barnard 등이 사용한 영상 데이터들 중 일부를 사용하였고, 불변 방향의 검출 성능은 엔트로피 최소화 기법과 비교되었다. 실험 결과, 제안한 기법은 기존 기법에 비해 표준편차가 낮아 불변 방향이 일정하게 검출되었으며, 시간적 측면에서 기존의 기법에 비해 3배 이상 효율적이었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.44.3-44
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• 2002

Stability robustness of a linear time-varying system with time-varying structured state space uncertainties is considered by using extended-mean theorem and Bellman's lemma. The extended-mean theorem is a necessary and sufficient exponential stability criterion based on the recently developed PD-eigenvalue and PD-eigenvector for a linear time-varying system. Our new result required that the extended-mean of each nominal PD-eigenvalue should be negative real which is determined by a norm involving the structures of the uncertainty and the no...

• Korean Journal of Mathematics
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• 제30권1호
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• pp.61-66
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• 2022

A new type of Riemannian manifold called semirecurrent manifold has been defined and some of its geometric properties are studied. Among others we show that the scalar curvature of semirecurrent manifold is constant and hence semirecurrent manifold is also concircularly recurrent. In addition, we show that the associated 1-form (resp. the associated vector field) of semirecurrent manifold is closed (resp. an eigenvector of its Ricci tensor). Furthermore, we prove that if a Riemannian product manifold is semirecurrent, then either one decomposition manifold is locally symmetric or the other decomposition manifold is a space of constant curvature.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.515-522
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• 2001

A simplified method is presented for the computation of eigenvalue and eigenvector derivatives associated with repeated eigenvalues. In the proposed method, adjacent eigenvectors and orthonormal conditions are used to compose an algebraic equation whose order is (n+m)x(n+m), where n is the number of coordinates and m is the number of multiplicity of the repeated eigenvalue. One algebraic equation developed can be computed eigenvalue and eigenvector derivatives simultaneously. Since the coefficient matrix of the proposed equation is symmetric and based on N-space, this method is very efficient compared to previous methods. Moreover the numerical stability of the method is guaranteed because the coefficient matrix of the proposed equation is non-singular, This method can be consistently applied to both structural systems with structural design parameters and mechanical systems with lumped design parameters. To verify the effectiveness of the proposed method, the finite element model of the cantilever beam and a 5-DOF mechanical system in the case of a non-proportionally damped system are considered as numerical examples. The design parameter of the cantilever beam is its width, and that of the 5-DOF mechanical system is a spring.

• 호남수학학술지
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• 제23권1호
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• pp.91-111
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• 2001

In this paper we prove the following : Let M be a semi-invariant submanifold with almost contact metric structure (${\phi}$, ${\xi}$, g) of codimension 3 in a complex hyperbolic space $H_{n+1}{\mathbb{C}}$. Suppose that the third fundamental form n satisfies $dn=2{\theta}{\omega}$ for a certain scalar ${\theta}({\leq}{\frac{c}{2}})$, where ${\omega}(X,\;Y)=g(X,\;{\phi}Y)$ for any vectors X and Y on M. Then M has constant eigenvalues correponding the shape operator A in the direction of the distinguished normal and the structure vector ${\xi}$ is an eigenvector of A if and only if M is locally congruent to one of the type $A_0$, $A_1$, $A_2$ or B in $H_n{\mathbb{C}}$.

• 대한수학회논문집
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• 제29권2호
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• pp.319-329
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• 2014

In this paper we study the properties of conformally recurrent pseudo Riemannian manifolds admitting a proper conformal vector field with respect to the scalar field ${\sigma}$, focusing particularly on the 4-dimensional Lorentzian case. Some general properties already proven by one of the present authors for pseudo conformally symmetric manifolds endowed with a conformal vector field are proven also in the case, and some new others are stated. Moreover interesting results are pointed out; for example, it is proven that the Ricci tensor under certain conditions is Weyl compatible: this notion was recently introduced and investigated by one of the present authors. Further we study conformally recurrent 4-dimensional Lorentzian manifolds (space-times) admitting a conformal vector field: it is proven that the covector ${\sigma}_j$ is null and unique up to scaling; moreover it is shown that the same vector is an eigenvector of the Ricci tensor. Finally, it is stated that such space-time is of Petrov type N with respect to ${\sigma}_j$.

• 대한수학회논문집
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• 제15권4호
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• pp.649-668
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• 2000

In this paper we prove the following : Let M be a real (2n-1)-dimensional compact minimal semi-invariant submanifold in a complex projective space P(sub)n+1C. If the scalar curvature $\geq$2(n-1)(2n+1), then m is a homogeneous type $A_1$ or $A_2$. Next suppose that the third fundamental form n satisfies dn = 2$\theta\omega$ for a certain scalar $\theta$$\neq$c/2 and $\theta$$\neq$c/4 (4n-1)/(2n-1), where $\omega$(X,Y) = g(X,øY) for any vectors X and Y on a semi-invariant submanifold of codimension 3 in a complex space form M(sub)n+1 (c). Then we prove that M has constant principal curvatures corresponding the shape operator in the direction of the distingusihed normal and the structure vector ξ is an eigenvector of A if and only if M is locally congruent to a homogeneous minimal real hypersurface of M(sub)n (c).

• 비파괴검사학회지
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• 제21권1호
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• pp.46-53
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• 2001

음향방출 신호를 이용하여 분류기를 설계하는 과정에서의 특징값 선택법에 관해 연구하였다. 분류기는 역전파법을 이용한 신경망 분류기를 사용하였다. Fisher's criterion, class mean scatter criterion, eigenvector analysis와 함께 본 논문에서 새로 제안하는 특징값 공간에서의 특징값 좌표사이의 차이를 이용하는 2-D criterion, 3-D criterion을 이용해서 특징값을 선택하고 각각에 대해 분류기를 설계하여, 인식률과 수렴속도를 비교하였다. 분류를 위한 자료를 얻기 위하여 용접부 결함시편과 로터리 압축기 금속 접촉부 결함시편을 사용하였다. 인식률 면에서 2-D criterion과 3-D criterion이 우수한 결과를 나타내었다.

• 동의생리병리학회지
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• 제34권4호
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• pp.159-169
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• 2020

Shanghanlun (Treatise on Cold Damage Diseases) is the oldest document in the literature on clinical records of Traditional Asian medicine (TAM), on which TAM theories about symptoms-herbs relationships are based. In this study, we aim to quantitatively explore the relationships between symptoms and herbs in Shanghanlun. The text in Shanghanlun was converted into structured data. Using the structured data, Term Frequency - Inverse Document Frequency (TF-IDF) scores of symptoms and herbs were calculated from each chapter to derive the major symptoms and herbs in each chapter. To understand the structure of the entire document, principal component analysis (PCA) was performed for the 6-dimensional chapter space. Bipartite network analysis was conducted focusing on Jaccard scores between symptoms and herbs and eigenvector centralities of nodes. TF-IDF scores showed the characteristics of each chapter through major symptoms and herbs. Principal components drawn by PCA suggested the entire structure of Shanghanlun. The network analysis revealed a 'multi herbs - multi symptoms' relationship. Common symptoms and herbs were drawn from high eigenvector centralities of their nodes, while specific symptoms and herbs were drawn from low centralities. Symptoms expected to be treated by herbs were derived, respectively. Using measurable metrics, we conducted a computational study on patterns of Shanghanlun. Quantitative researches on TAM theories will contribute to improving the clarity of TAM theories.