• 제목/요약/키워드: Subspace

검색결과 721건 처리시간 0.103초

SOME INVARIANT SUBSPACES FOR SUBSCALAR OPERATORS

  • Yoo, Jong-Kwang
    • 대한수학회보
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    • 제48권6호
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    • pp.1129-1135
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    • 2011
  • In this note, we prove that every subscalar operator with finite spectrum is algebraic. In particular, a quasi-nilpotent subscala operator is nilpotent. We also prove that every subscalar operator with property (${\delta}$) on a Banach space of dimension greater than 1 has a nontrivial invariant closed linear subspace.

A NOTE ON k-HYPERREFLEXIVITY OF TOEPLITZ-HARMONIC SUBSPACES

  • Budzynski, Piotr;Piwowarczyk, Kamila;Ptak, Marek
    • 대한수학회보
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    • 제51권6호
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    • pp.1727-1733
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    • 2014
  • The 2-hyperreflexivity of Toeplitz-harmonic type subspace generated by an isometry or a quasinormal operator is shown. The k-hyperreflexivity of the tensor product $\mathcal{S}{\otimes}\mathcal{V}$ of a k-hyperreflexive decom-posable subspace $\mathcal{S}$ and an abelian von Neumann algebra $\mathcal{V}$ is established.

Every Operator Almost Commutes with a Compact Operator

  • Jung, Il Bong;Ko, Eungil;Pearcy, Carl
    • Kyungpook Mathematical Journal
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    • 제47권2호
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    • pp.221-226
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    • 2007
  • In this note we set forth three possible definitions of the property of "almost commuting with a compact operator" and discuss an old result of W. Arveson that says that every operator on Hilbert space has the weakest of the three properties. Finally, we discuss some recent progress on the hyperinvariant subspace problem (see the bibliography), and relate it to the concept of almost commuting with a compact operator.

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부분공간법에 의한 건축구조물의 동특성 식별 (System Identification of Building Structure using Subspace Identification Method)

  • 배기환
    • 한국공간구조학회논문집
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    • 제3권4호
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    • pp.53-58
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    • 2003
  • In order to control seismic responses of building structures effectively and stably, it is very important to estimate the dynamic characteristics of target structure exactly based on input-output signal data. In this paper, it is shown that Subspace Identification Method is able to be applied effectively to system identification of building structures. To verify the efficiency of Subspace Identification Method, the vibration experiments were conducted on a specimen structure which is a 5-storied building structure model consisted of H-shaped steel beam, and the simulated seismic responses of the identified structure model were compared with the observed ones under the same excitation. It was observed that the experimental results coincided with the analyzed ones proposed in this paper.

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정류된 부공간 해석을 이용한 PET 영상 분석 (Rectified Subspace Analysis of Dynamic Positron Emission Tomography)

  • Kim, Sangki;Park, Seungjin;Lee, Jaesung;Lee, Dongsoo
    • 한국정보과학회:학술대회논문집
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    • 한국정보과학회 2002년도 가을 학술발표논문집 Vol.29 No.2 (2)
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    • pp.301-303
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    • 2002
  • Subspace analysis is a popular method for multivariate data analysis and is closely related to factor analysis and principal component analysis (PCA). In the context of image processing (especially positron emission tomography), all data points are nonnegative and it is expected that both basis images and factors are nonnegative in order to obtain reasonable result. In this paper We present a sequential EM algorithm for rectified subspace analysis (subspace in nonnegativity constraint) and apply it to dynamic PET image analysis. Experimental results show that our proposed method is useful in dynamic PET image analysis.

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전력 소비 데이터로부터의 출현 부분패턴 추출 (Emerging Subspace Discovery from Daily Load Consumption Data)

  • 박현우;박명호;류근호
    • 한국정보처리학회:학술대회논문집
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    • 한국정보처리학회 2013년도 춘계학술발표대회
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    • pp.908-910
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    • 2013
  • Customers of different electricity consumer types have different daily load shapes in the manner of different characteristics. Therefore, maximally capture load shape variability are desirable in load flow analysis. And most of time, such load shape variability can be found in the particular subspace of load diagrams. Therefore, in this paper, we are using subspace projection method to capture the emerging subspaces of load diagrams which maximize the difference between particular load shapes in different group of customers. As the result, subspace projection method can be used in load profiling and the performance is good as traditional approaches.

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수치적으로 안정한 부분공간 반복법 (Numerically Stable Subspace Iteration Method)

  • 정형조;김만철;박선규;이인원
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 1998년도 가을 학술발표회 논문집
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    • pp.84-91
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    • 1998
  • A numerically stable technique to remove tile limitation in choosing a shift in the subspace iteration method with shift is presented. A major difficulty of the subspace iteration method with shift is that because of singularity problem, a shift close to an eigenvalue can not be used, resulting in slower convergence. This study selves the above singularity problem using side conditions without sacrifice of convergence. The method is always nonsingular even if a shiht is an eigenvalue itself. This is one of tile significant characteristics of the proposed method. The nonsingularity is proved analytically. The convergence of the proposed method is at least equal to that of the subspace iteration method with shift, and the operation counts of above two methods are almost the same when a large number of eigenpairs are required. To show the effectiveness of the proposed method, two numerical examples are considered

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자동미분을 이용한 분리시스템동시최적화기법의 개선 (Improved Concurrent Subspace Optimization Using Automatic Differentiation)

  • 이종수;박창규
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 1999년도 가을 학술발표회 논문집
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    • pp.359-369
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    • 1999
  • The paper describes the study of concurrent subspace optimization(CSSO) for coupled multidisciplinary design optimization (MDO) techniques in mechanical systems. This method is a solution to large scale coupled multidisciplinary system, wherein the original problem is decomposed into a set of smaller, more tractable subproblems. Key elements in CSSO are consisted of global sensitivity equation(GSE), subspace optimization (SSO), optimum sensitivity analysis(OSA), and coordination optimization problem(COP) so as to inquiry valanced design solutions finally, Automatic differentiation has an ability to provide a robust sensitivity solution, and have shown the numerical numerical effectiveness over finite difference schemes wherein the perturbed step size in design variable is required. The present paper will develop the automatic differentiation based concurrent subspace optimization(AD-CSSO) in MDO. An automatic differentiation tool in FORTRAN(ADIFOR) will be employed to evaluate sensitivities. The use of exact function derivatives in GSE, OSA and COP makes Possible to enhance the numerical accuracy during the iterative design process. The paper discusses how much influence on final optimal design compared with traditional all-in-one approach, finite difference based CSSO and AD-CSSO applying coupled design variables.

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A Novel Subspace Tracking Algorithm and Its Application to Blind Multiuser Detection in Cellular CDMA Systems

  • Ali, Imran;Kim, Doug-Nyun;Song, Yun-Jeong;Azeemi, Naeem Zafar
    • Journal of Communications and Networks
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    • 제12권3호
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    • pp.216-221
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    • 2010
  • In this paper, we propose and develop a new algorithm for the principle subspace tracking by orthonormalizing the eigenvectors using an approximation of Gram-Schmidt procedure. We carry out a novel mathematical derivation to show that when this approximated version of Gram-Schmidt procedure is added to a modified form of projection approximation subspace tracking deflation (PASTd) algorithm, the eigenvectors can be orthonormalized within a linear computational complexity. While the PASTd algorithm tries to extracts orthonormalized eigenvectors, the new scheme orthonormalizes the eigenvectors after their extraction, yielding much more tacking efficiency. We apply the new tracking scheme for blind adaptive multiuser detection for non-stationary cellular CDMA environment and use extensive simulation results to demonstrate the performance improvement of the proposed scheme.

비압축성 Navier-Stokes 방정식의 수렴 가속을 위한 예조건화 Krylov 부공간법과 다중 격자법의 결합 (Combination of Preconditioned Krylov Subspace Methods and Multi-grid Method for Convergence Acceleration of the incompressible Navier-Stokes Equations)

  • 맹주성;최일곤;임연우
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 1999년도 춘계 학술대회논문집
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    • pp.106-112
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    • 1999
  • In this article, combination of the FAS-FMG multi-grid method and the Krylov subspace method was presented in solving two dimensional driven-cavity flows. Three algorithms of the Krylov subspace method, CG, CGSTAB(Bi-CG Stabilized) and GMRES method were tested with MILU preconditioner. As a smoother of the pressure correction equation, the MILU-CG is recommended rather than MILU-GMRES(k) or MILU-CGSTAB, since the MILU-GMRES(k) preconditioner has too much computation on the coarse grid compared to the MILU-CG one. As for the momentum equation, relatively cheap smoother like SIP solver may be sufficient.

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