• 한국수학교육학회지시리즈B:순수및응용수학
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• 제22권1호
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• pp.13-23
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• 2015

We introduce a decomposition on a symplectic subspace determined by symplectic structure and study its properties. As a consequence, we give an elementary proof of the deformation of the Grassmannians of symplectic subspaces to the complex Grassmannians.

• 대한기계학회논문집A
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• 제26권9호
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• pp.1822-1830
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• 2002

The paper describes the development of a decomposition based multidisciplinary design optimization (MDO) method that coordinates each of disciplinary subspace optimization (DSO). A multidisciplinary design system considered in the present study is decomposed into a number of subspaces based on their own design objective and constraints associated with engineering discipline. The coupled relations among subspaces are identified by interdisciplinary design variables. Each of subsystem level optimization, that is DSO would be performed in parallel, and the system level coordination is determined by the first order optimal sensitivities of subspace objective functions with respect to interdisciplinary design variables. The central of the present work resides on the formulation of system level coordination strategy and its capability in decomposition based MDO. A fluid-structure coupled design problem is explored as a test-bed to support the proposed MDO method.

• 충청수학회지
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• 제36권2호
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• pp.87-91
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• 2023

It is concerned with the size of bounded functions in Besov spaces. It reports that every closed subspace consisted with bounded functions in Besov spaces B^s_p,p(𝕋^d) (s < 0) is finite dimensional.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.299-303
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• 1995

This paper charcterizes dynamics of cold tandem minns, and constructs it state-space model of which are linear time invariant, using subspace method. Step responses particularly show the influence on mass transfer delay. Input-output data set are obtained form nonlinear differential equations including mass transfer delay and nonlinearity. It is shown that the identified state-apace model well approximates the original systems dynamics.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.133-138
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• 2006

Singular value decomposition (SDV) approach is applied to the observability analysis of GPS/INS in this paper. A measure of observability for a subspace is introduced. It indicates the minimum size of perturbation in the information matrix that makes the subspace unobservable. It is shown that the measure has direct connections with observability of systems, error covariance, and singular structure of the information matrix. The observability measure given in this paper is applicable to the multi-input/multi-output time-varying systems. An example on the observability analysis of GPS/INS is given. The measure of observability is confirmed to be less sensitive to system model perturbation. It is also shown that the estimation error for the vertical component of gyro bias can be considered unobservable for small initial error covariance for a constant velocity horizontal motion.

• 한국통신학회논문지
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• 제35권1A호
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• pp.54-61
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• 2010

본 논문에서는 셀룰러 환경에서 셀 간 간섭을 완화시키기 위한 부분공간 간섭 정렬 방법을 실제 시스템에 적용할 때 발생하는 채널 분리 오차와 채널 추정 오차에 따른 성능 열화를 개선시키기 위한 수신단 직교화를 통한 간섭 정렬 방법을 제안하였다. 제안된 방법은 셀 마다 서로 직교하는 참조 벡터를 사용함으로써 채널 분리 오차와 채널 추정 오차에 인해 남아있는 간섭신호를 줄여준다. 전산 모의 실험을 통해 채널 추정 오차가 발생하는 환경에서 제안된 방법을 통해 기존의 방법에 비해 향상된 합용량을 얻을 수 있었다.

• 충청수학회지
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• 제24권1호
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• pp.19-34
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• 2011

A bounded linear operator T on a complex Banach space X is said to have property (I) provided that T has Bishop's property (${\beta}$) and there exists an integer p > 0 such that for a closed subset F of ${\mathbb{C}}$ ${X_T}(F)={E_T}(F)=\bigcap_{{\lambda}{\in}{\mathbb{C}}{\backslash}F}(T-{\lambda})^PX$ for all closed sets $F{\subseteq}{\mathbb{C}}$, where $X_T$(F) denote the analytic spectral subspace and $E_T$(F) denote the algebraic spectral subspace of T. Easy examples are provided by normal operators and hyponormal operators in Hilbert spaces, and more generally, generalized scalar operators and subscalar operators in Banach spaces. In this paper, we prove that if T has property (I), then the quasi-nilpotent part $H_0$(T) of T is given by $$KerT^P=\{x{\in}X:r_T(x)=0\}={\bigcap_{{\lambda}{\neq}0}(T-{\lambda})^PX$$ for all sufficiently large integers p, where ${r_T(x)}=lim\;sup_{n{\rightarrow}{\infty}}{\parallel}T^nx{\parallel}^{\frac{1}{n}}$. We also prove that if T has property (I) and the spectrum ${\sigma}$(T) is finite, then T is algebraic. Finally, we prove that if $T{\in}L$(X) has property (I) and has decomposition property (${\delta}$) then T has a non-trivial invariant closed linear subspace.

• Structural Engineering and Mechanics
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• 제17권3_4호
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• pp.445-466
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• 2004

In this paper, several modal identification techniques for output-only structural systems are extensively investigated. The methods considered are the power spectral method, the frequency domain decomposition method, the Ibrahim time domain method, the eigensystem realization algorithm, and the stochastic subspace identification method. Generally, the power spectral method is most widely used in practical area, however, the other methods may give better estimates particularly for the cases with closed modes and/or with large measurement noise. Example analyses were carried out on typical structural systems under three different loading cases, and the identification performances were examined throught the comparisons between the estimates by various methods.

• 한국음향학회지
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• 제39권5호
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• pp.490-496
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• 2020

본 논문에서는 잡음 환경에서 다채널 위너 필터의 성능을 향상시키기 위한 방법을 제안한다. 부공간(subspace) 기반의 다채널 위너 필터를 설계하는 경우, 목적 신호가 단일 음원인 경우는 음성 상관 행렬의 주성분 부공간에서 음성 성분을 추정할 수 있다. 이 때, 음성 상관 행렬은 음성과 간섭 잡음의 교차 상관도가 음성 상관 행렬에 비해 무시할만한 수준이라는 가정하에 신호 상관 행렬에서 간섭 잡음의 상관 행렬을 차감하여 추정하게 된다. 그러나 간섭 잡음 수준이 높아지게 되면 이러한 가정이 더 이상 유효하지 않게 되며 이에 따라 주성분 부공간 추정 오차도 증가하게 된다. 본 연구에서는 음성 존재 확률과 목적 신호의 방향 벡터를 이용하여 주성분 부공간을 보정하는 방법을 제안한다. 주성분 부공간에서 다채널 음성 존재 확률을 유도하고 주성분 부공간 벡터를 보정하는데 적용하였다. 실험을 통해 제안하는 방법이 잡음 환경에서 다채널 위너 필터의 성능을 향상시키는 것을 확인할 수 있다.

• Computers and Concrete
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• 제12권6호
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• pp.803-818
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• 2013

In this study, analytical and experimental modal analyses of a scaled bridge model are carried out to extract the dynamic characteristics such as natural frequency, mode shapes and damping ratios. For this purpose, a scaled bridge model is constructed in laboratory conditions. Three dimensional finite element model of the bridge is constituted and dynamic characteristics are determined, analytically. To identify the dynamic characteristics experimentally; Experimental Modal Analyses (ambient and forced vibration tests) are conducted to the bridge model. In the ambient vibration tests, natural excitations are provided and the response of the bridge model is measured. Sensitivity accelerometers are placed to collect signals from the measurements. The signals collected from the tests are processed by Operational Modal Analysis; and the dynamic characteristics of the bridge model are estimated using Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods. In the forced vibration tests, excitation of the bridge model is induced by an impact hammer and the frequency response functions are obtained. From the finite element analyses, a total of 8 natural frequencies are attained between 28.33 and 313.5 Hz. Considering the first eight mode shapes, these modes can be classified into longitudinal, transverse and vertical modes. It is seen that the dynamic characteristics obtained from the ambient and forced vibration tests are close to each other. It can be stated that the both of Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are very useful to identify the dynamic characteristics of the bridge model. The first eight natural frequencies are obtained from experimental measurements between 25.00-299.5 Hz. In addition, the dynamic characteristics obtained from the finite element analyses have a good correlation with experimental frequencies and mode shapes. The MAC values obtained between 90-100% and 80-100% using experimental results and experimental-analytical results, respectively.